Sponsored by the Ocean Carbon & Biogeochemstry Program

with support from the:

National Science Foundation

National Oceanic and Atmospheric Administration

National Aeronautics and Space Administration

U.S. Geological Survey

U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2009-1070

Ocean Carbon and Biogeochemistry Scoping Workshop

on Terrestrial and Coastal Carbon Fluxes

in the Gulf of Mexico, St. Petersburg, FL

May 6-8, 2008

Ocean Carbon and Biogeochemistry Scoping 

Workshop on Terrestrial and Coastal 

Carbon Fluxes in the Gulf of Mexico, 

St. Petersburg, FL, May 6-8, 2008

By L.L. Robbins, P.G. Coble, T.D. Clayton, and W.-J. Cai

Sponsored by the Ocean Carbon & Biogeochemstry Program 

with support from the:

National Science Foundation

National Oceanic and Atmospheric Administration

National Aeronautics and Space Administration

U.S. Geological Survey

Open-File Report 2009–1070

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2009

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Government. 

This report summarizes the results of the Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and 

Coastal Carbon Fluxes in the Gulf of Mexico that was held in St. Petersburg, Florida, May 6-8, 2008. This event was 

jointly sponsored by the Ocean Carbon and Biogeochemistry Program (OCB) with support from the National Science 

Foundation (NSF), the National Oceanic and Atmospheric Administration (NOAA), the National Aeronautics and Space 

Administration (NASA), and the U.S. Geological Survey (USGS). Recommendations set forth in this document do not 

necessarily reflect the positions of the United States Government.

Suggested citation:

Robbins, L.L., Coble, P.G., Clayton, T.D., and Cai, W.-J., 2009, Ocean Carbon and Biogeochemistry Scoping Workshop 

on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico, St. Petersburg, FL, May 6-8, 2008: U.S. Geological 

Survey Open-File Report 2009-1070, 46 p.

The persistent URL for this report is http://pubs.usgs.gov/of/2009/1070/
iii

Contents

Executive Summary.......................................................................................................................................1

Introduction.....................................................................................................................................................2

Background............................................................................................................................................2

Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal 

Carbon Fluxes in the Gulf of Mexico, St. Petersburg, FL, May 6-8, 2008........................5

Workshop Motivation..................................................................................................................5

Workshop Goals...........................................................................................................................6

Workshop Description ................................................................................................................6

Overarching Research Question...............................................................................................6

Key Recommendations ...............................................................................................................7

Gulf of Mexico Carbon Fluxes: Knowns, Unknowns, and Uncertainties ..............................................7

Gulf of Mexico Provinces: Priority Environments for Future Research.......................................7

Open Gulf.......................................................................................................................................8

Eastern Gulf of Mexico .............................................................................................................10

Northern Gulf of Mexico...........................................................................................................10

Western Gulf of Mexico............................................................................................................12

Southern Gulf of Mexico...........................................................................................................13

Gulf-Wide Features ...................................................................................................................14

Carbon Budgets and Fluxes ..............................................................................................................15

From Drainage Basin to Ocean Basin: Research Gaps, Linkages, and Opportunities............17

Summary: Common Themes and General Recommendations.............................................................22

Data Availability and Continuity........................................................................................................22

Numerical Modeling...........................................................................................................................23

Issues of Scale....................................................................................................................................24

Infrastructure and Integration..........................................................................................................26

Workshop Agenda .......................................................................................................................................29

Participant List..............................................................................................................................................32

References Cited..........................................................................................................................................38

Figures

1-4. Maps showing:

1. The Gulf of Mexico’s surface drainage system covers more than 40% of 

 Mexico and more than 60% of the United States...............................................................3

2. Distribution of coastal surface water CO2 partial pressure measurements made 

 between 1979 and 2004 around North America.................................................................4

3. Distribution of the annual mean air-sea net CO2 flux over 1° x 1° pixel areas 

 around North America.............................................................................................................4

4. The Gulf of Mexico offers a variety of environments well suited for studying 

 various aspects of carbon transport and related processes...........................................9

5. Diagram showing carbon budget for the Mississippi River plume and northern 

 Gulf of Mexico.................................................................................................................................15
iv

 Abbreviations

AUV autonomous underwater vehicle

CDOM colored dissolved organic material

CRP Conservation Reserve Program

DEM digital elevation model

DIC dissolved inorganic carbon

DIN dissolved inorganic nitrogen

DOC dissolved organic carbon

DOM dissolved organic matter

ECoS Eastern Continental Shelf

EPA Environmental Protection Agency

ESRL Earth System Research Laboratory

FSLE Florida Shelf Lagrangian Experiment

GIS geographic information system

GMx Gulf of Mexico

GOMECC Gulf of Mexico and East Coast 

Carbon Cruise

IASNFS Intra-Americas Sea Ocean Nowcast/

Forecast System

LOICZ Land-Ocean Interactions in the 

Coastal Zone

LTER Long-Term Ecological Research

MMS Minerals Management Service

MOC marine organic carbon

NACP North American Carbon Program

NASA National Aeronautics and Space 

Administration

NDBC National Data Buoy Center

NEON National Ecological Observatory 

Network

NERRS National Estuarine Research Reserve 

System

NOAA National Oceanic and Atmospheric 

Administration

OCB Ocean Carbon and Biogeochemistry

OCCC Ocean Carbon and Climate Change

pCO2 partial pressure of carbon dioxide

PIC particulate inorganic carbon

POC particulate organic carbon

SGD submarine groundwater discharge

SLR sea-level rise

SPARROW SPAtially Referenced Regressions 

on Watershed Attributes

SSS sea surface salinity

SST sea surface temperature

SWAT Soil and Water Assessment Tool

TEM Terrestrial Ecosystem Model

USDA U.S. Department of Agriculture

USGS U.S. Geological Survey
Executive Summary 

Despite their relatively small surface area, ocean margins 

may have a significant impact on global biogeochemical 

cycles and, potentially, the global air-sea fluxes of carbon 

dioxide. Margins are characterized by intense geochemical 

and biological processing of carbon and other elements and 

exchange large amounts of matter and energy with the open 

ocean. The area-specific rates of productivity, biogeochemical 

cycling, and organic/inorganic matter sequestration are high in 

coastal margins, with as much as half of the global integrated 

new production occurring over the continental shelves and 

slopes (Walsh, 1991; Doney and Hood, 2002; Jahnke, in 

press). However, the current lack of knowledge and understanding of biogeochemical processes occurring at the ocean 

margins has left them largely ignored in most of the previous 

global assessments of the oceanic carbon cycle (Doney and 

Hood, 2002). A major source of North American and global 

uncertainty is the Gulf of Mexico, a large semi-enclosed 

subtropical basin bordered by the United States, Mexico, and 

Cuba. Like many of the marginal oceans worldwide, the Gulf 

of Mexico remains largely unsampled and poorly characterized in terms of its air-sea exchange of carbon dioxide and 

other carbon fluxes. 

In May 2008, the Ocean Carbon and Biogeochemistry 

Scoping Workshop on Terrestrial and Coastal Carbon 

Fluxes in the Gulf of Mexico was held in St. Petersburg, FL, 

to address the information gaps of carbon fluxes associated 

with the Gulf of Mexico and to offer recommendations to 

guide future research. The meeting was attended by over 90 

participants from over 50 U.S. and Mexican institutions and 

agencies. The Ocean Carbon and Biogeochemistry program 

(OCB; http://www.us-ocb.org/) sponsored this workshop with 

support from the National Science Foundation, the National 

Oceanic and Atmospheric Administration, the National 

Aeronautics and Space Administration, the U.S. Geological 

Survey, and the University of South Florida.

The goal of the workshop was to bring together 

researchers from multiple disciplines studying terrestrial, 

aquatic, and marine ecosystems to discuss the state of 

knowledge in carbon fluxes in the Gulf of Mexico, data gaps, 

and overarching questions in the Gulf of Mexico system. 

The discussions at the workshop were intended to stimulate 

integrated studies of marine and terrestrial biogeochemical 

cycles and associated ecosystems that will help to establish 

the role of the Gulf of Mexico in the carbon cycle and 

how it might evolve in the face of environmental change. 

The information derived from the plenary sessions, questions, and recommendations formulated by the participants 

will drive future research projects. Further discussion of 

carbon dynamics is needed to address scales of variability, the 

infrastructure required for study, and the modeling framework 

for cross-system integration. 

1U.S. Geological Survey, St. Petersburg, FL

2University of South Florida College of Marine Science, St. Petersburg, FL

3Ironwood Editorial Services, St. Petersburg, FL

4University of Georgia Department of Marine Sciences, Athens, GA

Ocean Carbon and Biogeochemistry Scoping 

Workshop on Terrestrial and Coastal 

Carbon Fluxes in the Gulf of Mexico, 

St. Petersburg, FL, May 6-8, 2008

By L.L. Robbins1, P.G. Coble2, T.D. Clayton3, and W.-J. Cai4
2 Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico

During the workshop, participants discussed and 

provided a number of priorities and recommendations, 

including:

□ An integrated, three-pronged approach to the study 

of Gulf of Mexico carbon fluxes, utilizing field 

observations, remote sensing, and coupled physicalbiogeochemical modeling

□ A formal data-mining effort to compile existing 

datasets and identify critical data gaps

□ Continuity of data collection, in terms of both 

frequency and duration

□ The selection of Gulf of Mexico study sites using 

existing classification schemes and study sites

□ Numerical modeling to help plan effective field 

campaigns and interpret results

□ Development of linked, nested models, using existing 

Gulf of Mexico models as a good starting point 

□ A forum devoted to collaborative assessment of 

existing data, model capabilities, and potential barriers 

to model linking or coupling 

□ Initial determination of appropriate temporal and 

spatial scales for field observations, and modeling 

efforts to constrain Gulf of Mexico carbon fluxes

□ With respect to infrastructure:

• An integrated network of terrestrial and marine 

carbon monitoring stations that build on existing 

infrastructure, with augmentation of capabilities 

where needed

• Recurring process cruises in the Gulf of Mexico

• The development of improved algorithms for 

interpretation of satellite remote sensing products

• A Gulf of Mexico data management center to 

provide measurement, modeling, and remote 

sensing products

• A common communication effort that uses 

existing networks and outreach opportunities to 

involve stakeholders and decisionmakers

Participants recognized that the key to understanding the 

Gulf of Mexico system requires international collaboration 

with scientists from countries adjacent to the Gulf of Mexico. 

Improved collaboration across existing research community 

boundaries will be critical and should be encouraged by the 

funding agencies.

Introduction

Background

North America has a major influence on the global 

carbon cycle—a cycle that is now out of balance (King and 

others, 2007), contributing to both the warming of the Earth’s 

atmosphere (IPCC, 2007) and the acidification of the Earth’s 

oceans (Kleypas and others, 2006). The continent is currently 

a net source of carbon dioxide (CO2) to the atmosphere. 

In 2003, 85% of North American emissions came from 

the United States, 9% from Canada, and 6% from Mexico. 

The continent’s land sink is about one-third the magnitude of 

its fossil-fuel emissions, making the continent a net source of 

carbon to the atmosphere (King and others, 2007).

As the United States, Mexico, and other countries move 

toward actively managing the flow of carbon—CO2 specifically—through terrestrial, oceanic, and atmospheric reservoirs, 

reducing uncertainties in estimates of past, current, and future 

carbon fluxes grows increasingly important. Coastal oceans in 

particular remain a large unknown, though the quantification 

of carbon fluxes in coastal oceans is important for understanding the global carbon cycle and for informing public 

discourse and decisionmaking (King and others, 2007).

Complicating such a quantification effort, coastal 

processes are complex and highly dynamic, with rapid 

changes and large variations across small distances (Chavez 

and others, 2007). Ocean margins are characterized by intense 

geochemical and biological processing of carbon and other 

elements, and exchange large amounts of matter and energy 

with the open ocean. Topographic features, tidal mixing, 

turbulent physical circulation, and freshwater inflow from 

rivers and groundwater all contribute to small-scale intricacies. Biological productivity is generally elevated relative 

to open ocean areas, and the proximity of bottom sediments 

and land introduces additional biogeochemical complexity. 

Area-specific rates of productivity, biogeochemical cycling, 

and organic/inorganic matter sequestration are high in coastal 

margins, with as much as half the global integrated new 

production occurring over continental shelves and slopes 

(Walsh, 1991; Doney and Hood, 2002; Jahnke, in press).

Most studies of these highly dynamic regions have been 

local to regional in scope, and few synthesis products and 

models have been designed with the special case of coastal 

oceans in mind. The lack of knowledge and understanding of 

biogeochemical processes occurring at ocean margins makes it 

difficult to assess their contributions to the global carbon cycle 

(Doney and Glover, 2005). 

It is not clear whether coastal oceans tend to be a net 

source or sink of atmospheric CO2. Numerous studies support 

the view that a significant fraction of current ocean uptake of 

anthropogenic CO2 may occur in continental-margin waters 

in the East China Sea (Tsunogai and others, 1999; Wang 
Introduction 3

and others, 2000), North Atlantic European shelves (Kempe 

and Pegler, 1991; Frankignoulle and Borges, 2001; Thomas 

and others, 2004), U.S. Middle Atlantic Bight (Boehme and 

others, 1998; DeGrandpre and others, 2002; Vlahos and 

others, 2002), and larger river plumes such as those of the 

Amazon (Ternon and others, 2000; Kortzinger, 2003) and 

Mississippi Rivers (Cai, 2003; Lohrenz and Cai, 2006). These 

findings, however, stand in contrast to prevailing arguments 

that continental shelves must be net heterotrophic (Smith and 

MacKenzie, 1987; Smith and Hollibaugh, 1993; Mackenzie 

and others, 1998). The latter view is supported by recent 

reports on several low-latitude shelf systems, including the 

U.S. southeastern shelf (Cai and others, 2003), South China 

Sea (Zhai and others, 2005), major upwelling areas (Lefèvre 

and others, 2002), and tropical coastal margins (Chavez 

and others, 2007). These contrasting and conflicting reports 

highlight the need for an integrated study of carbon fluxes and 

regulatory processes in continental-margin waters in order to 

better understand processes regulating fluxes and to constrain 

estimates of coastal margins’ contributions to overall oceanic 

CO2 uptake.

Large uncertainties remain for North American 

coastal margins. With the exception of one or two isolated 

time series, little is known about historical trends in the coastal 

oceans’ air-sea fluxes or source-sink behaviors (Chavez and 

others, 2007). 

One major source of North American and global uncertainty is the Gulf of Mexico (GMx), a large semi-enclosed, 

subtropical basin bordered by the United States, Mexico, and 

Cuba (fig. 1). Like many coastal oceans worldwide, the Gulf 

remains largely unsampled and poorly characterized in terms 

of its air-sea exchange of carbon dioxide (fig. 2) and fluxes 

of other carbon species. Limited data indicate that Gulf and 

Caribbean waters are, on the whole, a strong CO2 source 

(fig. 3). A recent synthesis suggests that GMx air-sea CO2

flux may dominate the net flux of the entire North American 

margin because of the Gulf’s large size and strong signals. 

Northern Gulf waters appear to be a strong local CO2 sink 

(Cai, 2003; Chavez and others, 2007). 

Interest in the Gulf of Mexico as a targeted study site has 

grown steadily over the past few years. A U.S. Carbon Cycle 

Science Plan (Sarmiento and Wofsy, 1999) proposed two 

long-term research goals: first, understanding the Northern 

Hemisphere land (carbon) sink, and, second, understanding 

the ocean carbon sink (with priority for regions in North 

America). Carbon cycling in ocean margins constitutes a 

critical link between these two atmospheric CO2 sinks, as 

is recognized by several recent workshops and meetings 

organized by the North American Carbon Program (NACP) 

and the Ocean Carbon and Biogeochemistry (OCB) Steering 

Committee.

Figure 1. The Gulf 

of Mexico’s surface 

drainage system covers 

more than 40% of Mexico 

and more than 60% of the 

United States.

Gulf of Mexico

Pacific Ocean

Atlantic Ocean

N
4 Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico

A 2005 ocean carbon and climate change workshop, 

“The Ocean Carbon System: Recent Advances and Future 

Opportunities,” highlighted the continental-margin carbon 

cycle as a key research area. Workshop participants noted that 

an improved understanding of coastal carbon processes will 

require a more extensive observational network (including 

field and remote sensing observations) across a diverse 

range of margin environments, such as river-dominated and 

upwelling regions (Doney and Glover, 2005). 

Another 2005 meeting, “North American Continental 

Margins: A Synthesis and Planning Workshop,” produced 

eight specific recommendations for improving knowledge 

of coastal carbon cycling (http://www.whoi.edu/cms/files/

NACM_04.25_35943.pdf). Participants noted the need for 

additional data, improved data synthesis, coastal models, 

remote-sensing algorithms, in-water technologies, and welldefined continental margin boundaries. Integrated process 

and synthesis studies were also recommended, with modeling 

to proceed in parallel with (and not subsequent to) the in-water 

process studies. The need for field measurements to determine 

net fluxes of total carbon across key regime boundaries (for 

example, estuary-ocean, air-sea) was emphasized.

Terrestrial/coastal carbon fluxes and exchanges are also 

a priority of the newly formed OCB program. A 2007 OCB 

workshop breakout session identified several key questions 

to be considered in large-scale studies of coastal carbon 

processes. Of particular interest were an improved understanding of the intricacies of shelf processes (for example, 

lateral transport, denitrification, nitrogen fixation) and 

their implications for coastal carbon budgets—and, in turn, 

continental and global carbon fluxes. Climate change and 

resource management were also recognized as processes that 

impact watershed dynamics, coastal ecological processes, and 

biogeochemical cycles, including that of carbon (Benway and 

Doney, 2007).

Figure 2. Distribution of coastal 

surface water CO2 partial pressure 

measurements made between 1979 

and 2004 (from Chavez and others, 

2007).

Figure 3. Distribution of the annual mean 

air-sea net CO2 flux over 1° x 1° pixel 

areas around North America. The greenyellow colors indicate that the ocean 

water is a source of CO2; the magenta 

colors indicate a sink of atmospheric 

CO2 (from Chavez and others, 2007).

180° 160° 140° 120° 100° 80° 60° 40°

180° 160° 140° 120° 100° 80° 60° 40°

80°

70°

60°

50°

40°

30°

20°

10°

80°

70°

60°

50°

40°

30°

20°

10°

N
Introduction 5

The Gulf of Mexico provides an ideal venue for studying 

many of the key carbon issues identified in prior workshops 

and publications:

• The Gulf represents the single largest North American 

coastal-ocean source of atmospheric CO2 (Chavez and 

others, 2007).

• The basin is semi-enclosed, facilitating the constraint 

of exchanges (Walsh and others, 1989).

• Including open water areas and coastal wetlands, the 

Gulf region covers more than 1.9 million square kilometers (km2), with inflow from 33 major river systems 

(Yáñez-Arancibia and Day, 2004a).

• The Gulf’s surface drainage system covers more 

than 60% of the United States and more than 40% 

of Mexico (Yáñez-Arancibia and Day, 2004b). 

The United States’ Mississippi River [18,400 cubic 

meters per second (m3/s) discharge (Benke and Cushing, 2005)] discharges directly onto the northern GMx 

shelf and represents one of the world’s largest signals 

for carbon cycling. Mexico’s Usumacinta-Grijalva rain 

forest river system [2,687 m3/s (Benke and Cushing, 

2005)] discharges directly onto the southern GMx 

shelf. The Gulf is also influenced by major river 

systems outside the Gulf proper, such as Venezuela’s 

Orinoco River.

• In addition to rivers, the Gulf receives significant 

freshwater inflow from submarine groundwater discharge, especially along its eastern and southern margins. In some areas, groundwater discharge represents 

a significant influx of nutrients.

• The basin provides a variety of margin types—including 

wide carbonate shelves with significant groundwater 

inflow, a river-dominated muddy shelf, and a narrow 

upwelling shelf.

• The basin is subject to a wide variety of physical processes—including significant buoyancy inputs, major 

boundary current flow, upwelling, eddy intrusions, and 

frequent strong storms (including hurricanes). 

• The Gulf is the site of significant nitrogen fixation, a 

process now recognized as important in carbon cycling 

and other aspects of ocean ecology and biogeochemistry. 

• For the past two decades, the northern Gulf has been 

the site of persistent, widespread summer hypoxia 

(up to 20,000 km2 in area), with significant ecological and economic impacts (Turner and others, 2005). 

Researchers expect the 2008 nitrogen-rich Mississippi 

River flood to produce the largest “dead zone” on 

record (Beeman, 2008).

• The Gulf of Mexico is significantly under-sampled in 

some respects. A recent compilation of North American coastal CO2 measurements (Chavez and others, 

2007; Hales and others, 2008) indicates a dearth of 

measurements in the region—to an extent rivaled only 

by the Gulf of California among all “lower 48” U.S. 

coastal waters. 

• Due to its riverine and other connections to the 

North American continent, the Gulf represents a 

unique opportunity to study land/ocean interactions 

comprehensively. 

In addition, a Gulf of Mexico carbon research program 

offers an excellent opportunity for international collaboration 

among agencies and scientists in the United States, Mexico, 

and Cuba. 

Ocean Carbon and Biogeochemistry Scoping 

Workshop on Terrestrial and Coastal Carbon Fluxes in 

the Gulf of Mexico, St. Petersburg, FL, May 6-8, 2008

Workshop Motivation

Despite their relatively small surface area, ocean margins 

may have a significant impact on global biogeochemical cycles 

and, potentially, the global air-sea fluxes of CO2. Margins are 

characterized by intense geochemical and biological processing 

of carbon and other elements and exchange large amounts of 

matter and energy with the open ocean. The area-specific rates 

of productivity, biogeochemical cycling, and organic/inorganic 

matter sequestration are high in coastal margins, with as much 

as half of the global integrated new production of carbon 

occurring over the continental shelves and slopes (Walsh, 1991; 

Doney and Hood, 2002; Jahnke, in press). However, the current 

gaps in knowledge and understanding of biogeochemical 

processes occurring at the ocean margins have left them largely 

excluded in most of the previous global assessments of the 

oceanic carbon cycle (Doney and Hood, 2002). 

Contrasting reports that some margins are sinks of anthropogenic CO2 and some are sources of CO2 highlight the need for 

an integrated study of carbon fluxes and processes in continental 

margin waters in order to better understand processes regulating 

fluxes and better constrain the role of coastal margins’ contribution to overall oceanic carbon cycling. 

A U.S. Carbon Cycle Science Plan (Sarmiento and 

Wofsy, 1999) proposed two long-term research goals: first, 

understanding the Northern Hemisphere land (carbon) sink 

and second, understanding the ocean carbon sink (with priority 

for regions in North America). Understanding carbon cycling 

in ocean margins provides a critical link between these two 

atmospheric CO2 sinks as is recognized by several recent 

workshops and meetings organized by the NACP and the OCB 

Steering Committee. A key area of uncertainty in current North 

American carbon budgets is the Gulf of Mexico. A recent 

synthesis (Chavez and others, 2007) suggests that the air-sea 

CO2 flux from the Gulf of Mexico may dominate the net flux of 

the entire North American margins because of the large size and 

strong signals. 
6 Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico

The Gulf of Mexico provides an excellent setting for 

large-scale study. Although it is a large body of water, its semienclosed nature makes it more feasible to constrain exchanges 

(Walsh and others, 1989). The Gulf of Mexico provides a wide 

variety of margin types (terrigenous clastic and carbonate 

sediments, narrow and broad shelves) and physical processes 

(buoyancy inputs, major boundary current, upwelling, eddy 

intrusions). The Mississippi River system represents one of the 

largest signals for carbon cycling in not just the North American 

continent but the entire world. A coordinated study in the Gulf 

of Mexico also provides an excellent opportunity for international collaboration with neighboring Mexico; scientists from 

this country have already expressed interest in such a study. 

Workshop Goals

The Ocean Carbon and Biogeochemistry Steering 

Committee identified coastal carbon fluxes and exchanges as 

a priority topic for future research. At a recent Ocean Carbon 

and Biogeochemistry Workshop held in Woods Hole, MA, on 

July 23-26, 2007, a breakout group examined this topic and 

identified several key questions, including: 

• Do continental margins represent a conduit for the 

large carbon signal that is currently unaccounted for in 

the terrestrial continental carbon budgets?

• What are the magnitudes and uncertainties of coastal 

carbon signals and to what extent will incorporation 

of more precise and accurate assessments of coastal 

carbon budgets into larger scale models improve the 

overall estimates of global carbon fluxes?

• How important are the intricacies of the shelf processes 

(lateral transport or cross shelf exchange, denitrification and nitrogen fixation, benthic processes, and 

ballasting of carbon and other elements by lithogenic 

materials) in regulating coastal carbon budgets?

• What are the impacts of climate change and resource 

management on watershed dynamics and coastal ecological processes, and what are the potential implications 

for biogeochemical cycles, including that of carbon?

This list is not exhaustive but identifies key issues that should 

be considered in large-scale studies of coastal carbon processes. 

Workshop Description

The Ocean Carbon and Biogeochemistry Scoping 

Workshop on Terrestrial and Coastal Carbon Fluxes in 

the Gulf of Mexico was held in St. Petersburg, FL, on 

May 6-8, 2008. The goal of the workshop was to bring 

together researchers to discuss potential integrated research 

projects related to carbon fluxes and exchange in the Gulf. 

Approximately 90 scientists attended, representing U.S. and 

Mexican research organizations, academic institutions, and 

government agencies. 

Twelve plenary speakers were asked to summarize the 

state of knowledge on carbon dynamics in various parts of the 

GMx system and to highlight processes of primary importance 

in controlling variability in fluxes and fates. During breakout 

sessions, conference participants were asked to build on the 

plenary information and formulate questions that will drive 

future research projects. Approximately 40 participants 

contributed posters.

The ultimate goal of future GMx research is to achieve 

an understanding of material and energy fluxes, exchanges, 

and fates so that we can anticipate river-ocean system changes 

related to global-scale climate changes. The workshop agenda, 

list of participants, background papers, and many of the 

presentations and posters are available online: http://www.

whoi.edu/sites/GMxCarbon/

This document outlines the major findings and recommendations of this workshop. Special thanks are owed to 

all the hard-working discussion leaders and rapporteurs for 

excellent note-taking and write-ups of all the breakout sessions 

and especially for staying after the end of the conference to 

be sure their reports were completed. These include Barnali 

Dixon, Chris Anderson, David Butman, Kathy Tedesco, Bob 

Chen, Robyn Conmy, Ron Benner, Nazan Atilla, David John, 

John Paul, Miguel Goñi, Regina Easley, Simone Alin, Charles 

Perry, Lori Adornato, Liz Gordon, Carlos Del Castillo, and 

Laura Lorenzoni. Thanks also to the Steering Committee: 

Wei-Jun Cai, Scott Denning, Ben de Jong, Eileen Hoffman, 

Brent McKee, and Steve Lohrenz (ex officio). We are particularly grateful to all the participants for their engagement in 

discussions and valuable contributions to our knowledge base 

and recommendations for future research planning.

Overarching Research Question

Workshop participants developed the following overarching question to express the proposed general scope and 

orientation of a Gulf of Mexico carbon flux program:

What are the net fluxes of total carbon through the 

key interfaces defining the Gulf of Mexico system, how can 

future changes in these fluxes be predicted, and how will these 

changes impact ecosystems?

□ The Gulf of Mexico system is here defined as including 

watersheds, margins, the open Gulf of Mexico, and the 

overlying atmosphere.

□ Key interfaces of interest are land-atmosphere, soilriver, river-estuary, estuary-ocean, seafloor-water 

column, ocean-atmosphere, shelf-Gulf interior, and 

Gulf of Mexico-Atlantic. 

□ Quantification of net fluxes of total carbon (dissolved 

and particulate, organic and inorganic) is needed over 

sufficiently long time scales to represent irreversible 

transfers between reservoirs.
Introduction 7

□ Anticipated future changes include both natural and 

human-induced perturbations. 

□ Successful prediction of future changes will require 

process- and synthesis-level understanding of internal 

carbon cycling as well as the roles of relevant 

noncarbon elements (for example, nitrogen and 

phosphorus). 

□ Ecosystem refers to all physical and all biological 

components, including human, of the environment. 

□ Careful consideration of appropriate scales and 

resolution is required, and these may not be the same 

for prediction as for quantification of fluxes.

Key Recommendations

Key recommendations to answer the overarching 

research question provided by the workshop participants 

included:

□ The study of the Gulf of Mexico as a whole system, 

from watersheds to open Gulf, rather than a 

conglomeration of parts.

□ An integrated, three-pronged approach to the study 

of GMx carbon, utilizing field observations, remote 

sensing, and coupled physical-biogeochemical 

modeling.

□ Comprehensive, cross-disciplinary data mining and 

model assessment, undertaken early in the program.

□ Augmentation of existing programs to build a largescale terrestrial and aquatic carbon-monitoring 

network and establish routine coastal process 

studies.

□ Ongoing support for well-calibrated, long-term 

remotely sensed measurements and accompanying 

algorithm development.

□ Interdisciplinary, multiscale modeling efforts that 

nest and link existing models, with emphasis on 

development of a community ocean circulationbiogeochemical model.

□ Strategic investment in new technologies.

□ Direct measurement of carbon and carbonrelated fluxes across key interfaces (for example, 

air-sea CO2 fluxes) will be required, along with 

accompanying process studies. Opportunities to 

maximize societal relevance, such as collaboration 

with economists and engagement in public outreach, 

should be encouraged.

□ Long-term continuity of monitoring data is critically 

important. The elimination of stream gage and water 

quality monitoring stations and potential lapses in 

satellite ocean color measurements were cited as 

particular concerns. 

□ Facilitation of communication between GMx researchers, 

policymakers, stakeholders, and the general public must 

be a core program element. On this note, the community 

recommends:

•	 Support for international and interdisciplinary 

collaborations

•	 Development of a one-stop Web-accessible GMx 

data management center or enhancement of one 

of the many existing data management programs 

to include this focus

•	 Augmentation of existing communication 

networks and outreach opportunities to solicit 

public input and provide information about 

carbon cycle biogeochemistry and its social and 

economic implications

□ Logistical support and assistance from the Ocean 

Carbon and Biogeochemistry program is desired in 

these specific areas:

•	 Administration of electronic lists to facilitate 

international, cross-disciplinary sharing 

of expertise and data among various 

subcommunities of researchers and stakeholders

•	 Mining of historical datasets

•	 Development and hosting of Web-based 

resources to receive and distribute information 

about GMx projects, research cruises, and so on

•	 Logistical support for field campaigns

•	 Data management, such as from GMx field 

campaigns

•	 Coordination of future meetings
8 Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico

Gulf of Mexico Carbon Fluxes: Knowns, 

Unknowns, and Uncertainties 

Land-ocean interactions represent a major gap in our 

understanding of carbon fluxes and biogeochemical cycling. 

With its riverine and other connections to the North American 

continent, the Gulf of Mexico presents a special opportunity to 

study these interactions.

Gulf of Mexico Provinces: Priority Environments 

for Future Research

Among North American continental margins, the Gulf of 

Mexico (fig. 1) is distinctive in terms of its river-dominated 

shelves and strong episodic storm events. On the northern 

and southern margins, where rivers deliver large quantities 

of particulate and dissolved carbon, sediments, and nutrients, 

high rates of sediment deposition and primary productivity 

occur, along with episodic sediment resuspension and redistribution. On the eastern and western Gulf margins, the river 

imprint is relatively small, and Loop Current and upwelling 

processes predominate (Hales and others, 2008).

The Gulf is fed by more than 150 rivers, including 20 

major river systems. The two largest are the Mississippi in 

the northern Gulf and the Usumacinta-Grijalva in the south. 

Freshwater inflow to the Gulf is approximately 10.6 x 1011

cubic meters per year (m3/yr), with more than 64% of that 

total arriving via the Mississippi River. Other U.S. rivers 

contribute another 21%, and the remaining one-fifth is 

supplied from Mexico and Cuba (Nipper and others, 2004). 

South Texas receives the least rainfall among Gulf coastal 

areas, more than an order of magnitude less than the wet 

regions of the northern Gulf’s Mississippi Delta and the 

southern Gulf’s Tabasco Plain (Solis and Powell, 1999). 

Groundwater contributions are significant in many areas, 

especially the eastern and southern margins of the Gulf.

Thirty-nine major estuary systems rim the Gulf, 32 on 

the eastern and northern margins and 7 along the western 

and southern edges (Schroeder and Wiseman, 1999). Large 

marine-dominated bays occur in the east, river-dominated 

estuaries characterize the northern Gulf, and examples of 

coastal lagoons may be found in the south (Pennock and 

others, 1999). Most of the Gulf’s estuaries are shallow 

[mean U.S. depth <2.5 m; (McKee and Baskaran, 1999)] and 

meteorologically dominated (Solis and Powell, 1999), with 

surface area and wind fetch higher than in other U.S. estuaries. 

Most are generally characterized by fine-grained sediments 

and frequent resuspension (McKee and Baskaran, 1999). Tidal 

influence on estuaries around the microtidal Gulf is relatively 

uniform (in contrast to freshwater influence), with tide ranges 

generally less than 1 m (Stumpf and Haines, 1998; McKee and 

Baskaran, 1999). The Mississippi River plume can be thought 

of as an unbounded estuary. 

More than 14,500 km2 of estuarine wetlands line Gulf 

coastlines. Approximately one third consists of forested 

mangrove wetlands, with the remainder being herbaceous 

marsh (Childers and others, 1998). Estuarine wetlands loss 

is a severe problem in all U.S. Gulf States (U.S. EPA, 1999), 

especially in the northern Gulf.

Human impacts, including eutrophication, are significant 

in some Gulf estuaries (Kennish, 2002). Nuisance and toxic 

algal blooms have been increasing in U.S. Gulf estuaries 

since the 1970s, and seagrass habitat has been declining. Fish 

biomarkers indicate fair to poor fish health in some areas 

of the northern Gulf, and shellfish bed closures have been 

significant (>25% of shellfish-growing waters) in most U.S. 

Gulf States (U.S. EPA, 1999).

Remote sensing coverage varies considerably over the 

basin. For ocean color measurements, satellite coverage, in 

terms of the percentage of clean pixels (Wanninkhof, 2008), 

is best over the carbonate shelves of the eastern and southern 

Gulf of Mexico (20-35% clean pixels) and poorest over the 

western basin.

The workshop participants recognized the Gulf of 

Mexico as five interconnected regions with distinctive physical 

forcings and biogeochemical characteristics and processes:

the deep Gulf basin and four marginal regions (fig. 4). 

The central region (1) is a deep, semi-enclosed oligotrophic 

basin with an energetic circulation strongly connected to the 

Caribbean Sea and Atlantic Ocean. The eastern GMx shelf 

(2) is influenced by upwelling, river discharge, and a large 

but poorly quantified influx of groundwater. The northern 

GMx shelf (3) is river-dominated, receiving major discharge 

from the Mississippi-Atchafalaya River system. The narrow 

western GMx shelf (4) is dominated by upwelling and by 

eddies shed from the Loop Current. The southern GMx shelf 

(5) is influenced by upwelling and by groundwater and river 

(Usumacinta-Grijalva) discharge.

Open Gulf

The Gulf of Mexico (figs. 1, 4) is a dynamic, semienclosed subtropical/tropical sea. Of the total marine area, 

approximately 20% is continental slope and another 20% is 

abyssal plain. The average depth is about 1,600 m and the 

maximum depth is about 4,000 m (Nipper and others, 2004).

Because of its size and connectivity, the Gulf’s contribution to global and regional processes is significant. The Gulf 

has a total marine area of about 1.5 million km2 (Nipper and 

others, 2004), and its great volume implies that it has large 

gross (though perhaps not net) fluxes (such as nutrients, 

air-sea gas fluxes). The Gulf strongly participates in the North 

Atlantic gyre circulation, and recent studies indicate that 

circulation in the Gulf of Mexico and the Caribbean Sea are 

dynamically interdependent (Oey and others, 2005). 
Gulf of Mexico Carbon Fluxes: Knowns, Unknowns, and Uncertainties 9

The central basin region interfaces with each of the other 

GMx (margin) regions and is the integrator of all processes in 

all other regions. Studying only the shelf regions would yield an 

incomplete picture of carbon dynamics in the Gulf.

The Gulf of Mexico may be an important driver for 

fluxes of carbon from ocean to land. The North American 

Carbon Program is especially interested in the effect of Gulf 

air masses on the Mississippi River basin. 

Dominant circulation features in the basin are the highly 

energetic Loop Current and its associated eddies (rings). 

Water enters the Gulf through the Yucatan Channel in the 

south, feeding the Yucatan/Loop western boundary current. 

The current then makes a wide, vigorous meander through 

the basin before flowing southward along the west Florida 

Shelf and exiting through the Florida Straits. The current and 

its rings (warm core rings in the western Gulf and cold core 

rings in the eastern Gulf) strongly interact with the basin’s 

continental slope and shelves (Vukovich, 2007). As a result, 

the Loop Current drives many shelf processes.

Physical forcing in the Gulf is poorly parameterized. 

The broad range of spatial and temporal scales associated with 

GMx circulation contributes to the challenges the Gulf presents to numerical modelers (Oey and others, 2005), although 

there are many GMx circulation models in existence. 

The Gulf of Mexico is a unique gas hydrate province 

(Milkov and Sassen, 2000). Natural gas hydrate, a mineral in 

which hydrocarbon and non-hydrocarbon gases are held within 

rigid (“icy”) cages of water, typically occurs from depths of 

about 440 m to more than 2,400 m (Milkov and Sassen, 2000). 

These deposits represent an enormous potential reservoir of 

methane—and therefore a potential future energy resource and 

agent of climate change (Kvenvolden and Lorenson, 2007). 

The Gulf is unique in that both bacterial methane and thermogenic methane occur in shallow sediments and outcrops at the 

seafloor (Milkov and Sassen, 2000). 

Figure 4. The Gulf of Mexico offers a variety of environments well suited for studying various aspects of 

carbon transport and related processes: (1) the open Gulf, (2) the West Florida shallow carbonate shelf, (3) the 

river-dominated northern shelf, (4) the narrow western shelf with its strong eddy-shelf interactions, and (5) the 

tropical Campeche Bay/Bank. Each region includes the watersheds of the streams and rivers that flow into the 

region’s estuaries and onto the shelf.

N

OPEN GULF

WEST FLORIDA SHALLOW CARBONATE SHELF

RIVER-DOMINATED NORTHERN SHELF

NARROW WESTERN SHELF

TROPICAL CAMPECHE BAY/BANK

1

2

3

4

5

EXPLANATION
10 Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico

Eastern Gulf of Mexico 

Terrestrial influences in the eastern Gulf (figs. 1, 4) 

arrive via local rivers, submarine springs, and aeolian dust. 

The southern two-thirds of the Florida peninsula is characterized by small rivers draining low-relief basins of less than 

2,600 km2 (Boning, 2008). To the north, two major rivers, the 

Suwannee and the Apalachicola, flow across the southeastern 

United States and into the Gulf. Their basins are characterized by moderate climate and abundant rainfall (Ward and 

others, 2005). Groundwater flows into the eastern Gulf from 

numerous freshwater springs on the West Florida Shelf 

(WFS), with concentrations of submerged springs found just 

off Tampa Bay and in the Aucilla River embayment (Hu and 

others, 2006). During summer months, aeolian (windborne) 

dust is supplied from Saharan West Africa to eastern Gulf and 

Caribbean waters, after a transit of thousands of kilometers 

across the Atlantic Ocean (Lenes and others, 2001).

Large marine-dominated bays are found along the eastern 

Gulf (Schroeder and Wiseman, 1999). Unlike most Gulf 

estuaries, these bays tend to show little intra-annual variability 

in salinity (Solis and Powell, 1999). Tides of the eastern Gulf 

margin are mixed but dominantly semidiurnal (Flick and 

others, 2003). Tidal range at Key West, FL, in the southeastern 

Gulf, is 0.56 m; at Cedar Key, FL, in the northeastern Gulf, it 

is 1.05 m. (Stumpf and Haines, 1998).

The land/sea boundary within this province is characterized by low-relief mangrove islands in the south, siliciclastic 

barrier islands in the central region, and marshes and 

limestone outcrops in the north. Episodic blooms, including 

headline-generating “red tides,” have been observed on the 

eastern shelf, but for most of the year this system is oligotrophic (Hales and others, 2008). The seaward margin of 

the broad (100-150 km wide) carbonate shelf is defined by 

the precipitous 1,600-m drop-off of the Florida Escarpment 

(Sager, 2007). 

The watersheds of the eastern Gulf have experienced 

explosive population growth over recent decades. Between 

1990 and 2004, the Florida Gulf Coast population grew by 

32.0%, from 4.07 million to 5.37 million; 2004-2006 brought 

another 4.6% growth. Population density during that period 

increased from 84 (1990) to 111 (2004) to 116 (2006) individuals/mi2. The population growth rate was highest (56%, 

1990-2003) in southwest Florida (Kildow, 2006, 2008).

The eastern Gulf is strongly influenced by the Loop 

Current and, seasonally, by Mississippi River outflow. 

The Loop Current occasionally intrudes upon the West Florida 

Shelf, generating a strong southward current of cold, nutrientrich water along the shelf slope (He and Weisberg, 2003). 

When the Loop Current retreats (that is, does not intrude far 

into the Gulf), it can generate southward flow on the middle 

and inner shelf as well. Mississippi River waters interact with 

the shelf seasonally and after major flood events.

This region provides an interesting contrast with the 

northern Gulf of Mexico, in terms of riverine influences. 

Freshwater surface inflow in the eastern Gulf is much lower 

than in the northern Gulf. West Florida rivers differ from 

northern rivers in terms of not only discharge rates but also 

chemistry. For example, West Florida rivers typically have 

higher concentrations of dissolved organic matter (DOM) and 

can strongly influence optical properties and dissolved organic 

carbon (DOC) concentrations of shelf waters (Del Castillo and 

others, 2000). 

Aeolian deposition is an important source of nutrients 

to the West Florida Shelf. West Florida Shelf summer iron 

concentrations, for example, are controlled by not only local 

riverine inflows but also by windborne dust transported from 

Saharan Africa. This episodic dust supply can fuel significant 

diazotrophic (nitrogen-fixing) activity and, ultimately, red 

tides (Lenes and others, 2008). 

The West Florida Shelf is a “leaky coastal margin” 

where submarine groundwater discharge (SGD) plays an 

important role. Many submarine springs occur along the West 

Florida Shelf, and SGD may be a significant source of nutrients, radionuclides, and other materials (Burnett and others, 

1990). Groundwater inputs of nitrogen to the inner West 

Florida Shelf may at times exceed those from atmospheric and 

riverine sources and may have been largely responsible for 

the sustenance of an intense 2005 red tide (67,500 km2) that 

could not have been supported by river runoff alone (Hu and 

others, 2006). Groundwater-related fluxes remain a significant 

unknown.

Phototrophic benthic microalgae are a potentially 

significant ecological constituent of the West Florida Shelf.

Pelagic algal blooms of the West Florida Shelf can, upon 

decay and remineralization, contribute to the growth of these 

members of the shelf-sediment flora. The contribution of 

phototrophic benthic microalgae to continental shelf ecosystems and carbon cycling has only recently been appreciated 

(Darrow and others, 2003).

Northern Gulf of Mexico

The northern Gulf margin (figs. 1, 4) is a highly dynamic, 

river-dominated region strongly influenced by watershed 

dynamics, most notably via Mississippi River inflow. 

Sediments on this shelf are largely terrigenous (land derived), 

and the region bears the distinction of annually developing 

one of the world’s most spectacular hypoxic zones (“the dead 

zone”).

The Mississippi River is the world’s second longest 

(6,700 km). Its basin, which covers 4,141 m of vertical relief, 

6 degrees of latitude, and approximately 3.72 million km2, 

is the world’s second largest, draining nearly 14% of North 

America and more than 40% of the continental United States. 
Gulf of Mexico Carbon Fluxes: Knowns, Unknowns, and Uncertainties 11

Mean precipitation is 94 cm/yr (Brown and others, 2005), 

ranging from 60 cm/yr in the northern grasslands to 160 

cm/yr in the south (DeLong, 2005). Food and fiber crops 

(such as corn, soybeans, rice) dominate the southern vegetation. For the basin as a whole, land use is 57% agricultural, 

28% forest/shrub, and 14% urban (Brown and others, 2005). 

The agricultural lands are generally highly engineered, 

characterized by pesticide and fertilizer application and 

physical modifications (for example, tilling) to facilitate 

the use of heavy machinery (Raymond and others, 2008). 

Population density in the upper basin is 54 individuals/

km2; in the lower basin, it is 10 individuals/km2 (Brown and 

others, 2005; DeLong, 2005). Mean river discharge to the 

Gulf is 18,400 m3/s, with runoff peaking in April (Brown and 

others, 2005). The Mississippi River is the major nutrient 

source to the Gulf, and its sediment discharge rate is among 

the world’s top 10 (Pennock and others, 1999). The basin 

exports about 10 (±5) grams of carbon per square meter per 

year (gCm-2 y-1) (80% in the form of dissolved inorganic 

carbon, DIC) to the Gulf, largely from cultivated land, where 

erosion is an order of magnitude greater than on forested land 

(Raymond and others, 2008).

Significant discharge from the Mississippi, in conjunction with the Atchafalaya River, is responsible for relatively 

high terrestrial inputs of organic carbon compared to other 

coastal margins of the United States (Hedges and Parker, 

1976; Bianchi and others, 1997). Recent work has suggested 

that much of the terrestrially derived organic carbon delivered 

to the shelf is from C3 and C4 plants and materials from 

eroded soils in the northwestern grasslands of the Mississippi 

River drainage basin. These investigators also concluded 

that C4 plant material [13C-enriched values similar to marine 

organic carbon (MOC)] was transported greater distances 

offshore because of its characteristically smaller grain size 

(Goñi and others, 1997; Goñi and others, 1998; Onstad and 

others, 2000; Gordon and Goñi, 2003). On the basis of 

earlier work, Goñi and others (1997) concluded that the C3

(

13C-depleted) terrestrial samples were being deposited on 

the shelf. However, recent analyses suggested that woody 

angiosperm material (C4-depleted) preferentially settles 

within the lower Mississippi and in the proximal portion of 

the dispersal system on the shelf (Bianchi and others, 2002). 

More recently, it has been demonstrated that erosion of relict 

peats in transgressional facies of the lower Mississippi River 

can provide another source of “old” vascular plant detritus to 

the Louisiana coastal margin (Galler and others, 2003). Inputs 

of Spartina spp. (C4 plants) from eroding marshes are also 

sources that contribute to the C4 signal found in Louisiana 

shelf sediments. 

The Mississippi River Delta is one of the most modified 

aquatic coastal ecosystems in the world and experiences as 

much as 80% of the wetland loss nationwide (peak rates of 

60-90 km2/y) (Gagliano and others, 1981; Turner and Rabalais, 

1991). Overall, recent estimates indicate an annual flux of 

particulate organic carbon (POC) of 9.3 x 108 kilograms 

per year (kg y-1) to the Gulf of Mexico (Bianchi and others, 

2007). Total lignin fluxes, which were based on lignin content 

normalized to organic carbon values of POC, were estimated 

to be 1.2 x 105 kg y-1. Louisiana shelf sediments have also 

been shown to effectively record the decrease in sediment and 

POC accumulation since about 1952, due to dam construction 

in the river (Allison and others, 2007). If the total DOC flux is 

included (3.1 x 109 kg y-1) (Bianchi and others, 2004; Bianchi 

and others, 2007), this results in a total organic carbon flux 

of 4.0 x 109 kg y-1. This represents 0.82% of the annual total 

organic carbon supplied to the oceans by rivers (4.9 x 1011 kg).

Other major rivers in the region include the 

Choctawhatchee, Escambia-Conecuh, Mobile, Pascagoula, and 

Pearl. Their drainage basins are characterized by a moderate 

climate and abundant rainfall, and their mainstem channels 

are often fragmented by damming and deepened by dredging. 

Several of the major rivers flow into moderate to large 

estuaries (Pennock and others, 1999).

The river-dominated estuaries that characterize the 

northern Gulf from the Florida panhandle to eastern Texas 

have short residence times, some as low as 2 days (Solis and 

Powell, 1999), and high displacement rates (Pennock and 

others, 1999). These high displacement rates indicate the 

potential for substantial discharge of materials to the Gulf 

and enhancement of shelf productivity (Solis and Powell, 

1999). Gulf bays dominated by freshwater inflow (such as 

the Atchafalaya-Vermilion Bay) show little intra-annual 

variability in salinity, unlike most GMx estuaries (Solis and 

Powell, 1999). Among U.S. Gulf estuaries, salinity values tend 

to be lowest in the vicinity of the Mississippi River (Solis and 

Powell, 1999). Galveston Bay’s Port of Houston is one of the 

world’s busiest commercial ports. In 2006, it recorded more 

than 7,500 vessel calls (Port of Houston Authority, 2008).

Tides are dominantly diurnal on Alabama shores, strongly 

diurnal at the Mississippi River Delta, and mixed in Louisiana 

(Flick and others, 2003). Tidal range at Pensacola, FL, is 

0.40 m; at Galveston, TX, it is 0.36 m (Stumpf and Haines, 

1998). 

The northern Gulf of Mexico acts as a “continental 

integrator.” This region integrates a huge meridional 

range because of the size and location of its watershed. 

The Mississippi River drains more than 3 million km2, 

approximately 40% of the land area of the continental United 

States, and supplies about 90% of the GMx freshwater inflow 

(Mitsch and others, 2001).

The northern Gulf margin is strongly influenced by 

watershed/river processes and land use in the continental 

United States. Efforts to reduce the development of hypoxia in 

the northern Gulf, for example, focus in large part on changing 

agricultural practices in the Mississippi River basin (Mitsch 

and others, 2001). 
12 Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico

Because conditions in the northern Gulf are determined 

in large part by river processes, river management represents 

an important nexus where some control over fluxes can be 

exerted. Policy and management decisions can impact water 

quality on surprisingly short time scales. 

River plume processes profoundly influence carbon 

fluxes and cycling in the northern Gulf. The Mississippi River 

supplies the shelf not only with freshwater but also with large 

amounts of dissolved and suspended particulate materials. 

Primary production rates in the Mississippi River plume 

are among the highest measured in large-river estuaries and 

plumes (Cai, 2003), and plume waters are distinct from those 

of the Gulf at large in terms of air-sea gas exchange. Offshore 

transport of plume sediments to canyons is important in GMx 

carbon transport. 

The northern Gulf in the region of the Mississippi River 

plume may be an important CO2 sink. Studies suggest that 

biological productivity fueled by nutrient input can lead to 

seawater in this region becoming a strong local CO2 sink during 

the summer growing season (Chavez and others, 2007).

The northern continental shelf has the largest zone of 

oxygen-depleted shelf waters (“the dead zone”) in the western 

Atlantic Ocean. Its extent on the sea bottom (1996-2006 

average) is twice the total surface area of the Chesapeake Bay 

(Turner and others, 2007). Hypoxia is one symptom of eutrophication—an increase in carbon production and accumulation 

rates—and improved carbon-flux monitoring is a primary 

recommendation of the U.S. Environmental Protection Agency’s 

Scientific Advisory Board (U.S. EPA, 2007). The annual formation of this northern GMx low-oxygen water mass (Rabalais and 

others, 2002) profoundly affects not only local biotic assemblages but also sediment structure and all chemical constituents 

and biogeochemical cycling in the area. 

This province provides a good opportunity to study 

cross-shelf sediment/carbon transport, including the roles 

of benthic and canyon-related processes. The northern Gulf 

experiences massive sediment input, and its submarine 

canyons are relatively accessible. Sediment remobilization is 

an important process in this area. 

The northern Gulf supports major recreational 

and commercial fisheries. The Mississippi River region 

supports one of the United States’ most productive fisheries 

(Pennock and others, 1999), with fisheries in the northern 

Gulf generating $2.8 billion per year (NOAA, 2007). With 

estuarine-dependent species accounting for more than 95% of 

the commercial GMx fish harvest, area wetlands (more than 

half the U.S. total) (U.S. EPA, 1999) constitute a significant 

commercial asset. 

This region is the site of much of the Gulf’s hydrocarbon 

production. The outer continental shelf of the Gulf of Mexico, 

with its nearly 40,000 wells, is said to be the world’s most 

extensively developed and mature offshore petroleum province 

(Kaiser and Pulsipher, 2007).

Western Gulf of Mexico 

The northwestern Gulf (figs. 1, 4) is fed by 11 major 

rivers with generally narrow southeast-trending catchments (the 

Sabine, Neches, Trinity, San Jacinto, Brazos, Colorado, Lavaca, 

Guadalupe/San Antonio, Nueces, and Rio Grande). The lower 

reaches of these rivers are generally channelized for irrigation 

and navigation. From east to west, the climate is increasingly 

arid, ranging from humid continental in eastern Texas to desert 

in western Texas. The western rivers contribute relatively little 

discharge to the Gulf (Dahm and others, 2005). Laguna Madre, 

one of the world’s few hypersaline estuaries, is in this area (Solis 

and Powell, 1999). 

The major river system of the western Gulf (figs. 1, 4) is 

the Rio Pánuco, which drains 98,200 km2, mostly from the 

mountains of east-central Mexico (basin relief is 3,800 m), and 

discharges at the port city of Tampico. Mean air temperature is 

20 °C, and mean precipitation is 96 cm/yr. Population density 

in the basin is low, and land use is dominated by traditional 

slash-and-burn and other agriculture in the uplands and sugarcane and citrus farming and cattle ranching in the lowlands. 

Petroleum extraction also occurs in the lower basin. Water 

quality is poor in many places. Mean discharge to the Gulf is 

540 m3/s (Hudson and others, 2005). The microtidal Estuario 

Pánuco is, most of the time, a highly stratified salt-wedge 

estuary (Arcos-Espinosa and others, 2008). 

Much of the land/sea boundary in this region is defined 

by extensive sandy barrier beaches. The narrow shelf is characterized by anticyclonic ring interactions, convective mixing, 

and river runoff and fronts (Escobar-Briones and Soto, 1997). 

Tides are dominantly diurnal (Flick and others, 2003). 

Coastal land use and land cover in this region are 

rapidly changing. For the six Mexican states bordering the 

southern and western Gulf, more than 80% of their economic 

activities—primarily oil and gas production and petrochemical 

industries, fisheries, marine transportation, agriculture, cattle 

ranching, and tourism—are located in or are associated with 

the coastal zone (Sánchez-Gil and others, 2004). Growing 

commercial and recreational activities on the Gulf’s western 

coast are contributing to growing pollution problems (Siemens 

and others, 2006), with the Rio Pánuco being acutely compromised by water quality degradation (Hudson and others, 

2005). Mexico’s principal Gulf port is located at Veracruz 

(Siemens and others, 2006). 
Gulf of Mexico Carbon Fluxes: Knowns, Unknowns, and Uncertainties 13

Episodic rivers with high sediment loads flow into this 

Gulf region. The major river system, the Rio Pánuco-Tamesi, 

arises in the arid altiplano, descends through dry mountains 

and moist forests, and enters the Gulf near Tampico. Discharge 

is low from December through May and often peaks in 

September, following regional patterns of precipitation, which 

are determined in part by tropical cyclones (Hudson and 

others, 2005).

The western Gulf is characterized by strong eddy/

shelf interactions. Loop Current warm core rings have been 

observed colliding with the western shelf (Oey and others, 

2005). Shelf properties and benthic communities in the area 

are strongly influenced by these ring interactions (EscobarBriones and Soto, 1997). 

Summer coastal upwelling occurs in this region. 

Upwelling-favorable winds occur from April to August, peaking 

in July. As a result, cold waters occur on the shelf in the 

summer, with maximum sea surface temperatures occurring in 

September (Zavala-Hidalgo and others, 2006). 

Longshore and cross-shelf transport are both important 

on this narrow shelf. At Veracruz, the shelf is only about 30 

km wide (Zavala-Hidalgo and others, 2006).

The northwestern Gulf of Mexico is characterized by 

vast rafts of free-floating vegetation. Satellite ocean color 

studies (2002-2007) indicate that Sargassum—a protected 

essential fish habitat and a huge carbon pool—accumulates in the 

Gulf early in the year, with concentrations peaking May-June. 

The floating brown algae is then advected into the Atlantic, 

occurring off Cape Hatteras in the summer and eventually 

northeast of the Bahamas by the following February (Gower and 

others, 2006; Gower and King, 2008). Sea surface accumulations 

of Trichodesmium are also prominent in the northwestern Gulf.

Southern Gulf of Mexico

The major river system of the southern Gulf (figs. 1, 4) is 

the Usumacinta-Grijalva, which drains a 112,600 km2 region 

characterized by tropical rain forest. Basin relief is 3,800 m. 

Mean air temperature is 23 °C, and mean precipitation is 

199 cm/yr (Hudson and others, 2005). The low-lying Tabasco 

Plain is one of the regions of highest Gulf coast rainfall (Solis 

and Powell, 1999). Population density is approximately 28 

individuals/km2. Dominant land cover is forest (59%) and 

cropland (31%). Mean discharge to the Gulf is 2,678 m3/s, 

with runoff peaking in October (Usumacinta only) (Hudson 

and others, 2005). Tides in this region are dominantly diurnal 

(Flick and others, 2003). 

The watershed data for the southern Gulf of Mexico 

represent a significant knowledge gap. In general, fewer data 

are available for Mexican watersheds, rivers, and marine areas 

than for regions in the United States. Water quality information for the Usumacinta-Grijalva River system, for example, is 

not available (Hudson and others, 2005). The Campeche Bay/

Bank area, a broad tropical carbonate platform that hosts some 

of the Gulf’s healthiest coral reefs, has long been recognized 

as a strategic location for a global-observing network timeseries station (IOC, 1997). 

The Usamacinta-Grijalva River system, which drains 

lush tropical rain forest, provides the second highest freshwater discharge to the Gulf, second only to the Mississippi

(Yáñez-Arancibia and Day, 2006). All of the drainage basin 

receives ample rainfall. Discharge into the Gulf is poorly 

quantified (Hudson and others, 2005). 

One major uncertainty in the region is associated with 

groundwater fluxes. Submarine groundwater discharge into 

the Yucatan coastal zone is significant (Álvarez-Góngora and 

Herrera-Silveira, 2006) but poorly quantified. The semiarid 

lagoons of the karstic northern peninsula receive very little 

surface inflow but significant groundwater discharge from 

submarine springs. This groundwater tends to be characterized by low suspended sediment, low dissolved oxygen, low 

ammonium and phosphate, and high nitrate concentrations 

(Pennock and others, 1999). In the state of Quintana Roo 

on the Yucatan Peninsula, groundwater pollution is a major 

concern (Yáñez-Arancibia and Day, 2006).

The southern coastal region is experiencing rapid 

population growth. The state of Quintana Roo, for example, 

has experienced exponential population growth over the last 

quarter-century, driven largely by tourism (Yáñez-Arancibia 

and Day, 2006). 

With this rapid population growth come rapid changes 

in land cover, land use, and the delivery of continental 

materials to the Gulf. In Quintana Roo, for instance, an explosion of tourism has brought cruise ships and extensive coastal 

development. The result has been widespread inland deforestation, groundwater pollution, coastal habitat destruction, and 

unsustainable fisheries (Yáñez-Arancibia and Day, 2006). 

Biomass burning is also significant in the region. For the six 

Mexican states bordering the southern and western Gulf, more 

than 80% of their economic activities—primarily oil and gas 

production and petrochemical industries, fisheries, marine 

transportation, agriculture, cattle ranching, and tourism—are 

located in or are associated with the coastal zone (Sánchez-Gil 

and others, 2004).

Cross-shelf exchange is important in Campeche Bay. 

The southern shelf, with the exception of the huge Campeche 

Bank, is generally narrow.

The Yucatan is one of the most important upwelling 

regions on a western oceanic margin (Merino, 1997). One 

upwelling area has been observed north of Cabo Catoche 

(IOC, 1997), a site of high new carbon production and chlorophyll stocks. A second upwelling area has been observed 

as a band of cool coastal water along the northern Yucatan 

coastline (IOC, 1997). 
14 Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico

The Campeche area experiences nearly year-round 

phytoplankton blooms and may export red tide “seed” 

material to other areas of the Gulf. On the Bank of Campeche, 

diatom blooms occur in the winter and spring, followed by toxic 

dinoflagellate blooms during summer and fall. Bloom material is 

often entrained into the Loop Current, which carries it north and 

east into the Gulf of Mexico (IOC, 1997).

The southern Gulf is the site of significant hydrocarbon production. The Bay of Campeche is responsible for 

more than three-quarters of Mexican oil and gas production 

(Schifter and others, 2005).

Gulf-Wide Features

Some important processes and research opportunities are 

common to all five Gulf provinces.

Sea-Level Rise. The entire Gulf of Mexico is subject to 

global sea-level fluctuations. Additionally, local geomorphology 

and processes that contribute to high rates of relative sea-level 

rise (SLR) make some margin areas especially vulnerable. 

During the past century, mean sea level has risen consistently 

in the Gulf of Mexico (Stumpf and Haines, 1998). For the U.S. 

Gulf Coast, lowest rates of SLR (0 to 3 mm/yr) are found along 

the Florida coast, and highest rates (upwards of 9 mm/yr) are 

found in eastern Louisiana (NOAA, 2008). The microtidal range 

of the entire Gulf Coast enhances vulnerability to the effects of 

rising sea level (Thieler and Hammar-Klose, 2000).

Most of the eastern Gulf is at moderate risk in terms of 

vulnerability to sea-level rise. The greatest risk factors in this 

region are its geomorphology (largely high-risk barrier island 

complexes, marshes, lagoons, and deltas), low tidal range and, in 

some areas, high erosion rates (Thieler and Hammar-Klose, 2000). 

In the northern Gulf, relative (local) sea level is rising 

in some areas at rates of up to 10 mm/yr. Coastal erosion 

and wetlands loss along the northern Gulf are occurring at 

dramatic rates. In the Mississippi Delta, annual wetlands loss 

may be as high 65 km2 (Douglas, 2005).

In some areas of the southern Gulf (Campeche), the sea 

is advancing inland at about 3 m/yr (IOC, 1997). Campeche 

coastal areas are characterized by extensive seagrass 

meadows, mangrove forests, tidal wetlands, and a broad 

deltaic environment (Yáñez-Arancibia and others, 1999)—

low-lying or shallow environments susceptible to drowning or 

inundation by rising seas. 

Extreme Events. The region is subject to extreme natural 

events. The warm waters of the Caribbean and Gulf provide 

abundant energy to fuel intense tropical storms (Maloney 

and Hartmann, 2000), and the entire Gulf region is subject to 

hurricanes and the accompanying extreme precipitation and 

devastating storm surge and high winds. High precipitation 

associated with cold fronts constitutes an additional hazard in 

some areas.

The northern Gulf region provides a good opportunity 

to study the effects of extreme events on a river-dominated 

ocean margin. This region is subject to a variety of short-term, 

intense environmental disruptions, such as hurricanes and river 

floods. The northern continental slope experiences turbidity 

currents and debris flows. The distribution of existing research 

facilities along the northern Gulf makes a regionally coordinated 

research response to extreme events feasible (Bortone, 2006). 

The western Gulf margin and its watersheds are 

subject to droughts and floods. Some of the flood risk is 

associated with tropical cyclones. In August 2007, Hurricane 

Dean made landfall (its second) just north of Veracruz as 

a Category 2 storm (Avila, 2008). River flow in the region 

tends to be flashy, following local precipitation (Hudson and 

others, 2005).

Along the southern margin, one of the most devastating 

recent events was associated with the passage of a cold front. 

In late October 2007, high precipitation and Grijalva River 

overflow inundated the Tabasco lowlands, generating extensive infrastructure and property damage and impacting more 

than 1 million victims (López-Méndez and others, 2008).

Ocean Acidification. Since 1980, approximately onethird of the excess CO2 released by anthropogenic activities 

has been taken up by the oceans. This uptake, which tends 

to drive seawater to lower pH and lower carbonate-mineral 

saturation states, is expected to increase carbonate dissolution 

rates, decrease biotic and abiotic calcification, and perhaps 

shift the average composition of modern carbonate sediments 

(Kleypas and others, 2006; Morse and others, 2006). Corals 

are expected to become increasingly rare in response to the 

double blow of a warming climate and ocean acidification 

(Hoegh-Guldberg and others, 2007). 

The “carbonate factory” of the broad West Florida Shelf 

in the eastern Gulf represents significant buffering capacity 

and provides a natural subtropical laboratory for studying 

ocean acidification. Situated in the subtropical transition zone 

between photozoan-reef communities (coral reefs characterized by photosynthesis-dependent aragonitic corals and 

calcareous algae) and heterozoan-ramp carbonate communities 

(carbonate ramps characterized by foraminifers and coralline 

algae), this shelf offers a good opportunity to study changes 

in aragonite saturation state and carbonate-producing biota 

(Hallock, 2005). Such studies are needed to understand and 

predict the responses of shallow-water carbonate communities to 

conditions of rising atmospheric CO2.

The southern region’s carbonate-producing communities 

provide another natural laboratory—this one more tropical in 

nature. Campeche Bank, like the West Florida Shelf, is a sedimentary carbonate environment but is more tropical in nature. 

Coral reefs, almost a third of the Gulf’s named reefs, occur on 

this broad bank. Largely removed from human and continental 

influence by their distance offshore, these reefs are among the 

healthiest in the area (Tunnell, 2007). Whitings also occur in 
Gulf of Mexico Carbon Fluxes: Knowns, Unknowns, and Uncertainties 15

the region. The socioeconomic impact of declining fisheries 

habitat including coral reefs (Orr and others, 2005; Fabry and 

others, 2008) may be especially severe in this region. 

International Collaboration. Research in the Gulf 

of Mexico provides an ideal opportunity for international 

collaboration. Three countries have watersheds bordering 

the Gulf of Mexico—the United States, Mexico, and Cuba. 

Activities in any one of these countries’ watersheds can 

potentially affect the industries—such as fisheries, oil, and 

tourism—and welfare of the others.

Carbon Budgets and Fluxes 

Achieving closure of macroscopic carbon budgets in 

continental margin settings is generally difficult (Hales and 

others, 2008), and the Gulf of Mexico is no exception. The key 

unresolved questions regarding carbon cycling along North 

American margins (Hales and others, 2008) apply to the Gulf 

as well: Is the coastal ocean a net source or sink for atmospheric CO2? What are the net sources and forms of carbon 

and nutrients delivered from rivers through estuaries to the 

ocean? What is the net processing of terrestrial and marine 

carbon within the coastal ocean, and what are the resulting net 

transfers of carbon between the coastal oceans and adjacent 

areas (for example, coastal seafloor, open ocean)? In other 

words, the fluxes of total carbon across key interfaces are 

poorly constrained, and the net diagenesis of total carbon in 

the coastal ocean is poorly understood.

At present, no carbon budget is available for the Gulf of 

Mexico as a whole or for most GMx subregions. Preliminary 

budgets for the northern Gulf shelf, site of the Gulf’s dominant 

river system, have been recently formulated, still with large 

uncertainties (fig. 5; Lohrenz, 2008; Lohrenz and Cai, 2008; 

Cai, unpub. data, 2008). This exercise, useful for identifying 

not only major flux terms but also major data gaps, should 

be undertaken for the Gulf early in a GMx carbon research 

program, along with direct measurements of fluxes across key 

interfaces. 

The major GMx carbon pathways are terrestrial inputs; 

vertical flux, sinking, and burial; shelf-ocean exchange; and 

air-sea flux. Significant carbon-transformation processes in the 

Gulf include primary production, remineralization and biogeochemical cycling, and photodegradation/photoremineralization 

(Lohrenz, 2008). Major uncertainties in GMx carbon budgets 

include the rates of organic carbon degradation in the water 

column and surface sediments and the rates of shelf-ocean 

carbon exchange (Lohrenz and Cai, 2008; Lohrenz, 2008). 

Terrestrial inputs of inorganic and organic carbon to the 

Gulf of Mexico arrive primarily via rivers on the northern 

and southern GMx shelves. Estimated terrestrial input to the 

northern Gulf from the Mississippi-Atchafalaya River system 

is approximately 26.0 teragrams of carbon per year (TgC/yr) 

(fig. 5). Roughly 80% arrives in the form of inorganic carbon, 

almost all dissolved, and 20% arrives as organic carbon 

(8% dissolved plus 12% particulate). For comparison, total 

riverine carbon input to the global ocean is approximately 50% 

dissolved inorganic carbon and 50% organic carbon (28% 

dissolved plus 22% particulate; McKee, 2003; Lohrenz, 2008). 

Figure 5. Carbon budget for the 

Mississippi River plume (green 

box) and northern Gulf of Mexico. 

Courtesy of Wei-Jun Cai. 

Outside plume

Turbidity plume

PP = (20)?

20%PP

CO (?) 2

CO (0.34?) 2

20 CO (atm) 2

Drainage Basin

River input

DIN = 1.0

DIC = 21

TOC = 5.0

DIC, DIN

Overall NCP = 5.7/2 (P) - 4(R) = -1.2

(all units = 10 gC/yr; DIN = 10 gN/yr) 12 12

1

?

15%PP

Outside NCP < -3.5

DIC?

DIN?

PP = 5.7, R = 0.6PP

plume NCP = 2.3

CARBON BUDGET-For the

Mississippi River plume

northern Gulf of Mexico

DISSOLVED INORGANIC CARBON

DISSOLVED INORGANIC NITROGEN

GRAMS OF CARBON PER YEAR

DIC

DIN

gC/yr

GRAMS OF NITROGEN PER YEAR

NET COMMUNITY PRODUCTION

PHOTOSYNTHESIS

PRIMARY PRODUCTIVITY

RESPIRATION

TOTAL ORGANIC CARBON

gN/yr

NCP

P

PP

R

TOC

EXPLANATION
16 Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico

Mississippi River organic carbon export (5.0 TgC/yr) 

represents more than 10% of the total POC+DOC export 

for North America (as estimated by Seitzinger and others, 

2005). Even in areas where the delivery of organic carbon 

is not particularly large (such as the West Florida Shelf), its 

implications for ecosystem structure and carbon cycling can 

be significant (Walsh and others, 2003).

Several lines of evidence indicate significant recent 

changes in terrestrial inputs to Gulf waters. The riverine 

supply of inorganic carbon, for example, has increased over 

recent decades in the northern Gulf (Raymond and Cole, 

2003). During the past half-century, the export of carbonate 

alkalinity (HCO3

-

 + CO3

2-) from terrestrial soils to the Gulf 

via the Mississippi River has increased dramatically, due in 

part to increased river flow (resulting from higher rainfall in 

the river basin) and in part to changes in land cover. Alkalinity 

export per unit area tends to be high in areas of cropland 

cover.

Groundwater represents another route for terrestrial 

inputs and can be significant, especially along the eastern 

(Corbett and others, 2000; Hu and others, 2006) and southern 

shelves. Even in areas without conspicuous springs, groundwater inflow via seepage can be important (for example, 

northern and northeastern Gulf; Cable and others, 1996; Krest 

and others, 1999; Rutkowski and others, 1999). Submarine 

groundwater discharge into Gulf coastal regions has not, 

however, been extensively studied (Zektser and others, 2007). 

The role of coastal wetlands as suppliers of organic carbon 

(“outwelling”) is also emerging as an important GMx research 

issue (Lohrenz, 2008). 

GMx vertical carbon flux, sinking, and burial are 

highly variable in space and time, and large uncertainties are 

associated with their estimates. Rivers deliver large amounts of 

particulate and dissolved organic carbon to GMx estuaries and 

shelves, but the fractions recycled in the water column, recycled 

in surface sediments, exported to the open ocean, and buried in 

sediments are not well known (Lohrenz and Cai, 2008). In situ 

marine production is also an important source term. 

In general, water-column degradation of POC in shallow, 

river-dominated areas is relatively small compared to that 

occurring in the open ocean (with its long settling times), but 

in some shelf areas adjacent to the Mississippi River, pre- and 

post-depositional decay can be equally significant (Chen and 

others, 2001; McKee and others, 2004). Sinking of particulates 

(Trefry and others, 1994), flocculation and aggradation (Dagg 

and others, 1996), and zooplankton-mediated vertical transfer 

(Wysocki and others, 2006) are important and have been best 

studied in the northern Gulf. Vertical flux rates of organic 

material may also be enhanced by lithogenic particles that act as 

ballast materials (Trefry and others, 1994). High sedimentation 

rates encourage longer-term organic carbon burial and preservation (McKee and others, 2004; Lohrenz, 2008; Lohrenz and 

Cai, 2008). Organic carbon burial on the northern Gulf shelf is 

estimated to be approximately 0.5 to 1.0 Tg/yr (approximately 

10-20% of the terrestrial delivery; Lohrenz, 2008). 

Shelf-ocean exchange is perhaps the most poorly 

constrained flux term for the Gulf. Important GMx shelfexchange processes include eddy-topography interactions 

(Sutyrin and others, 2003), buoyancy-driven circulation, 

wind-driven canyon flow (Yuan, 2002), river-plume displacement, and circulation and upwelling. Upwelling patterns in 

the Gulf are influenced by not only winds but also bottom 

bathymetry (see Weisberg and others, 2000). Wind forcing 

also exerts a strong influence on the position of the Mississippi 

River plume and the transport of suspended sediments (Walker 

and others, 2005). In areas of high deposition, sediment mass 

movement (for example, slumps and slides in the vicinity of 

the Mississippi; McKee and others, 2004) is significant.

Limited observations, comparisons with similar systems, 

and preliminary calculations indicate that, on an annual 

basis, the Gulf is likely a source of CO2 to the atmosphere

(fig. 3) (Chavez and others, 2007; Lohrenz and Cai, 2008). 

Local exceptions have been observed on the eastern and 

northern shelves in association with high biological productivity, which can produce significant CO2 drawdown (see 

Lohrenz and Cai, 2006). On the eastern shelf, nearshore 

sampling indicates that surface waters are a CO2 source, but 

it is not known whether these sites are representative of the 

broader shelf. The state of the northern, western, and southern 

shelves is not known. In the area of the Mississippi River 

plume, surface partial pressure of carbon dioxide (pCO2) is 

highly variable (Chavez and others, 2007; Lohrenz, 2008; 

Lohrenz and Cai, 2008), with reduced pCO2 consistently 

observed in late spring and early summer (Lohrenz and Cai, 

2006; Lohrenz, 2008). Resolving the magnitude of the Gulf 

of Mexico CO2 source (or sink) is a critical need (Chavez and 

others, 2007; Lohrenz and Cai, 2008). 

Developing general expectations or predictions regarding 

CO2 fluxes in the Gulf is difficult, as key forcings in the 

region can drive surface pCO2 toward either super- or undersaturation (Lohrenz and Cai, 2008). Rivers, for example, 

deliver significant organic matter to the Gulf—the respiration 

of which tends to elevate pCO2. At the same time, rivers also 

deliver freshwater (buoyancy) and nutrients, which encourage 

water column stratification and fuel photosynthetic CO2

uptake—thus lowering surface pCO2. Storms can similarly 

create conditions that support both CO2 release to the atmosphere and CO2 uptake. For example, storms may destratify 

the water column and bring high-pCO2 waters to the sea 

surface, where they can outgas to the atmosphere. But storms 

may also, through more than one pathway, deliver nutrients 

that support post-storm blooms and CO2 uptake.
Gulf of Mexico Carbon Fluxes: Knowns, Unknowns, and Uncertainties 17

Additional GMx observations are needed to improve 

estimates of CO2 air-sea exchange and other carbon-related 

fluxes for North American coastal oceans and the continental 

atmosphere. No large-scale systematic effort to measure 

air-sea CO2 fluxes has been undertaken in the Gulf (Lohrenz 

and Cai, 2008), and maps of coastal surface water pCO2

measurements show few in the region (fig. 2). Limited data are 

available for the relatively well-studied eastern and northern 

shelf areas, with additional data collected recently on the 

2007 NACP Gulf of Mexico and East Coast Carbon Cruise 

(GOMECC) (Peng and Langdon, 2007). For the western 

and southern shelves, no measurements of CO2 distributions 

or fluxes were unearthed during recent data compilations 

(Chavez and others, 2007; Lohrenz and Cai, 2008). A full 

complement of seasonal pCO2 measurements is also lacking 

(Chavez and others, 2007). For the entire Gulf, not a single 

1o x 1o pixel has CO2 measurements for more than two 

calendar months (see fig. 1.4 in Hales and others, 2008).

Gulf CO2 fluxes are important in the modulation and 

estimation of continental (atmospheric) CO2 concentrations, especially for the U.S. mainland north of the Gulf 

of Mexico. Large fluctuations in air-sea CO2 fluxes—not 

uncommon in the coastal ocean—can influence CO2 concentrations over adjacent continents. This effect is especially 

important where the mean airflow is onshore, as is typical 

of the summertime northern GMx coast. In addition, poorly 

characterized air-sea CO2 fluxes and variability can introduce 

significant errors into continental CO2 fluxes calculated by 

atmospheric inversion methods, especially at regional scales 

(Chavez and others, 2007; Hales and others, 2008; Lohrenz 

and Cai, 2008). 

Estimating and explaining GMx carbon fluxes and 

budgets requires consideration of not only carbon but also 

carbon-relevant elements and compounds (such as nutrients) and ecosystem structure. In the Mississippi plume, 

for example, river-supplied nutrients support high levels 

of biological production, which in turn strongly influence 

particle export fluxes and air-sea CO2 exchange (Lohrenz 

and Cai, 2008). Integrated primary production (Lohrenz and 

others, 1997; Cai and Lohrenz, in press) and satellite-derived 

chlorophyll measurements (Lohrenz and Cai, 2006) are 

directly proportional to terrestrial nitrogen fluxes. Sustained 

high nutrient loading from the Missisippi River also drives 

sustained high sedimentary oxygen demand (Turner and 

others, 2008), which profoundly influences the cycling 

of carbon and many other elements on the northern shelf. 

The Mississippi River not only dominates the terrestrial input 

of nitrogen and phosphorus to the Gulf (Turner and Rabalais, 

2004)—it is also unique among the world’s major rivers, 

having the highest ratio of dissolved inorganic nitrogen (DIN) 

flux to discharge (Dagg and others, 2004). 

In northern Gulf plume and marine food webs, the largest 

fluxes of carbon are through the phytoplankton and bacterioplankton. The major fate of phytoplankton is microzooplankton-dominated grazing (Lohrenz, 2008), but grazing and 

“packaging” by larger zooplankton (for example, copepods) 

may have a greater impact on vertical carbon fluxes (Dagg and 

others, 2007).

Gulf of Mexico carbon modeling studies, an important 

tool in budget formulations, are in an early stage of development. Ocean circulation models have been developed for the 

Gulf, with a particular focus on the challenge of reproducing 

Loop Current behavior, and ecosystem models have been 

developed for the study of specific regions and ecological 

components (for example, red tides on the West Florida Shelf; 

Walsh and others, 2003). However, carbon cycling in the Gulf 

of Mexico has never been modeled (Hales and others, 2008). 

Early experimental efforts are now underway (He, 2008), 

coupling ecosystem models (see Denman and Peña, 1999; 

Fennel and others, 2006; Kishi and others, 2007) with a U.S. 

East Coast and GMx circulation model.

From Drainage Basin to Ocean Basin: Research 

Gaps, Linkages, and Opportunities

The Gulf of Mexico is uniquely well suited for the study 

of land/ocean coupling as it influences carbon fluxes and 

biogeochemical cycling. The landward boundaries of the Gulf 

are best defined not by its tidal shores but by the upslope and 

recharge boundaries of its watersheds and aquifers (fig. 1). 

Many rivers, submerged springs and seeps, and atmospheric 

exchange processes link the Gulf to the lands and people 

of the North American continent. Freshwater, sediments, 

nutrients, and carbon—inorganic and organic, particulate and 

dissolved, labile and refractory—are supplied in great quantity 

to the semi-enclosed basin, and the Gulf’s warm waters in turn 

supply moisture and sustenance to the midcontinental United 

States and other Gulf regions. 

Critical data/research gaps

•	 Long-term monitoring data

•	 Direct observations of total carbon and related 

fluxes across key ocean interfaces

•	 Community ocean circulation model

Rigorously defined high-quality physical and biogeochemical measurements will be required to constrain 

estimates of carbon inputs, transport, transformation, and 

fate in the streams, rivers, estuaries, and open basin of the 

Gulf of Mexico. The various forms of carbon, nitrogen, and 

phosphorus need to be better understood and more skillfully 

measured. Methods development and investment in new technologies will be key elements of a successful GMx program. 

Particulate organic carbon measurements, for example, 

need to be improved (compelling evidence of measurement 
18 Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico

shortcomings is presented in the fact that some databases 

report more dissolved than total organic carbon), and spectral 

information about dissolved components would be helpful. 

The capabilities of isotope and optical measurements (such as 

fluorescence) have yet to be fully exploited. 

Key observations regarding GMx carbon sources, transport, and sinks include characterizations of seasonal carbon 

storage in river channels, suspended minerals and organics in 

watersheds and coastal environments, river nutrient inputs, 

groundwater-ocean interface fluxes, cross-shelf and canyon 

sediment transport, and storm and frontal-event impacts (for 

example, flushing of coastal systems and resuspension of 

sediments).

The major sources of terrestrial carbon to the estuaries, 

shelves, and central basin of the Gulf of Mexico are not well 

characterized. Both riverine and nonriverine sources supply 

significant carbon, but the relative contributions of the various 

sources are not well known, nor are the relative proportions 

of various carbon forms or the effects of tides, seasonality, 

and coastal management. Nonriverine sources include aeolian 

deposits as well as runoff (including stormwater runoff) and 

seepage from wetlands, coastal lagoons, marshes, beaches, 

and groundwater. In the Gulf basin, contributions from natural 

hydrocarbon seeps and oil platforms are also of interest.

Long-term precipitation and river discharge monitoring 

are critically needed, and recent cutbacks in these programs 

are a concern. Precipitation, along with land use/land cover, 

is a key determinant of carbon fluxes from the landscape into 

streams and estuaries and ultimately the Gulf. Data on areaspecific precipitation are needed, as are better constraints on 

likely precipitation-pattern changes associated with large-scale 

climate change. Understanding fluxes through river-mouth 

and estuarine zones is a key need, for which the coverage of 

stream gage monitoring stations will need to be expanded 

downstream into the zone of tidal influence (into the salt 

wedge). 

Comparative studies of the contrasting river-estuarine 

systems of the Gulf of Mexico are encouraged. For example, 

Mexican GMx watersheds and rivers have generally fewer 

dams and greater rainfall than U.S. watersheds, and that 

contrast presents an opportunity to study the effects of a range 

of landscape processes. To help characterize fluvial contributions to the Gulf, determination of the carbon loading of a 

variety of GMx rivers over time would be helpful. Much of the 

research to date has focused on the northern Gulf because of 

the magnitude of the signal there and the relevance of carbon 

loading to the problem of hypoxia (see Turner and others, 

2007). Riverine carbon storage and downstream transport in 

general are not well understood, nor are connections to higher 

trophic levels. Improved definition of the stream-flow network 

is required, and accumulation terms need to be defined, along 

with in-stream residence times and downstream changes in 

nutrient reactivity. In river-dominated areas, a better understanding of the importance of in-river autochthonous production below the confluence relative to upstream watershed and 

tributary inputs is needed. Quantification of the effects of 

dams and land use changes on riverine carbon transport and 

sequestration around the Gulf is essential. 

Recommendations

•	 Reinstate key monitoring stations and programs 

and support their long-term maintenance

•	 Quantify fluxes of carbon and carbon-relevant 

materials across key interfaces via direct 

measurement with accompanying process 

studies

•	 Identify the major sources of terrestrial carbon to 

the Gulf

Groundwater inputs, which are poorly characterized but 

substantial in at least the eastern and southern regions, cannot 

be ignored. In some areas, groundwater flow dominates the 

freshwater inflow (Pennock and others, 1999). This inflow—

the significance of which is coming to be appreciated by not 

only scientists but also coastal managers—can be an important 

source of freshwater, carbon, nutrients, pesticides, industrial 

wastes, sewage, and pathogens (SCOR and LOICZ, 2004). 

The role of GMx wetlands needs to be better constrained. 

Preliminary results from one case study in northern Gulf salt 

marshes, for example, indicate that outwelling and groundwater inputs of DOM likely exceed riverine inputs in the area 

(Dittmar, 2007). Inferences from studies of the microbial food 

web may also indicate a role for wetlands-derived DOM in 

encouraging the development of hypoxia (Dagg and others, 

2008). A major data gap is the lack of a nationally consistent 

wetlands database (Boyer, 2008); wetlands characterizations 

are inconsistent in their approach and need to be standardized. 

Remote sensing can likely contribute to this endeavor. 

The nature of the carbon discharged to the Gulf, refractory versus labile, needs to be better characterized, as do the 

effects of changing proportions as the carbon is processed in 

estuaries and on the shelf. In the northern Gulf, the relative 

proportions of labile and refractory carbon have tremendous 

societal relevance, as different assumptions or conclusions 

regarding the lability of terrestrial carbon leads to starkly 

different conclusions regarding the cause of inner-shelf 

hypoxia—and therefore strikingly different mitigation recommendations (Boesch, 1999, 2003). Fluorescence measurements 

suggest that Mississippi River DOC is more labile than the 

DOC of Florida rivers, yet this difference and its implications 

have yet to be fully explored. 
Gulf of Mexico Carbon Fluxes: Knowns, Unknowns, and Uncertainties 19

The fate of carbon once it enters the coastal ocean is not 

well understood. Lateral and vertical carbon fluxes need to 

be quantified, but the dominant modes and effects of carbon 

transformation and transport are not well characterized. It is 

not known, for example, how much terrigenous organic carbon 

is remineralized in the water column, how much is remineralized in the sediments, or how much is buried and preserved in 

estuarine, shelf, slope, and basin environments (Lohrenz and 

Cai, 2008). The fate of carbon discharged to the Gulf depends 

in large part on the type of margin to which the materials 

are delivered (for example, shallow, shelf-dominated versus 

deeper, slope-dominated). Variations in river flow, biological 

production, remineralization, photochemistry, hydrological 

sorting (winnowing), and diagenesis must all be considered 

(Gardner and others, 1994; Waterson and Canuel, 2008). 

Carbon-relevant species—their fluxes and biogeochemical 

cycling—must be considered as well. Nitrogen cycling in 

general (including N supply and N2 fixation) is a critical topic 

(Lohrenz, 2008).

Recommendations

•	 Support community development and adoption of 

a mature GMx ocean circulation model

•	 Support continuous, well–calibrated satellite 

ocean color measurements; support algorithm 

development for sea-surface temperature, 

sea-surface salinity, chlorophyll concentration, 

phytoplankton standing stock, and colored 

dissolved organic material

Sediments are very important in Gulf estuaries yet also 

represent a major unknown in terms of their dynamics and 

biogeochemical roles (for example, in modulating biological 

productivity or delivering pollutants). Approximately 90% 

of the sediment discharged by rivers of the conterminous 

United States enters Gulf estuarine environments (McKee and 

Baskaran, 1999). 

The role of inorganic (mineral) ballast on carbon 

transport in the Gulf is likely significant but is not well 

characterized. The association of nearly neutrally buoyant 

organic particles with dense, fast-sinking mineral particles 

allows the organic matter to sink at an accelerated rate. This 

association may also help preserve the organic matter from 

degradation (Armstrong and others, 2001; Lee and others, 

2004). Candidate mineral ballast particles in the Gulf include 

fine terrigenous river-borne sediments, aeolian dust particles, 

siliceous diatom tests, and the calcium carbonate tests of 

foraminifera. 

Determination of transport parameters for dissolved 

species presents a particular challenge, and the quantity of 

terrigenous carbon transported offshore as dissolved organic 

carbon remains unknown. Research in the northern Gulf 

indicates that autochthonous production, bacterial utilization, 

and photo-oxidation could all be important in regulating and 

removing DOC. Further study of these processes is recommended (Wang and others, 2004). 

The role of microbial organisms and food-web processes 

represents a major knowledge gap. Recent work in the 

northern Gulf, for example, indicates that the microbial food 

web may make an unexpectedly significant contribution to 

the summertime development of inner-shelf hypoxia when 

pelagic appendicularians are abundant in coastal waters, 

especially during times of low river flow and in regions 

remote from the Mississippi-Atchafalaya River plumes 

(Dagg and others, 2008). 

The effects of episodic events, including their timing 

and frequency, warrant further investigation. These effects are 

sometimes dramatic and sometimes subtle. In the disappearing 

salt marshes of the undeveloped northern Gulf, for example, 

spectacular hurricanes are the dominant supplier of inorganic 

sediment, with the net long-term effect being greatest when 

several strong hurricanes occur within a few years (Turner and 

others, 2007). On the Campeche shelf of the southern Gulf, 

quiet changes in the local macrofauna of carbonate sediments 

accompany winter storms coming from the northerly direction, 

as evidenced by increases in opportunistic polychaete taxa 

several months after storm passage (Hernández-Arana and 

others, 2003).

Another important issue is the transport and fate of 

river-, wetland-, and plume-derived material across the shelf 

to canyons. In the river-dominated northern Gulf, the slope 

and canyons may be important sinks for terrigenous carbon 

(Waterson and Canuel, 2008). Ultimate GMx carbon sinks 

(such as burial, export) and controls on burial rates are in 

general poorly quantified.

Other significant unknowns include the role of photochemistry, effects of hypoxia on carbon burial, effects of salt 

wedge adsorption/desorption processes, and the role of events 

beyond GMx boundaries (that is, south of Yucatan). The landsea exchange of living resources (for example, the cycling of 

shrimp, fish) is an open question to which fisheries data might 

be applied. 

Gulf of Mexico air-sea gas fluxes are of intense interest, 

but observations are sparse. The Gulf remains largely 

unsampled and poorly characterized in terms of air-sea gas 

exchange (figs. 2, 3). Extrapolation from limited CO2 data 

collected primarily on the northern and eastern shelves 

suggests that Gulf and Caribbean waters are, on an annual 

basis, a CO2 source (Chavez and others, 2007). Extrapolation 

from other limited data—those collected in the southern Gulf 

and Caribbean Sea—suggest the opposite: that the region is a 
20 Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico

CO2 sink (Wanninkhof, 2008). To better characterize regional 

CO2 fluxes, a network of surface water pCO2 observing 

systems (ships and moorings) is recommended. 

Recommendations

•	 Establish surface water pCO2 observing systems 

(ships and moorings)

•	 Establish a robust air sampling program

•	 Perform a process study for direct measurement 

of CO2 fluxes (as an example, a yearlong platform 

study)

•	 Develop robust CO2 -relevant remote sensing 

algorithms applicable to regions affected by 

riverine input

A more extensive CO2 dataset is needed to characterize 

not only GMx air-sea fluxes but also regional land-atmosphere 

fluxes. Atmospheric inversion approaches to estimating net 

regional land-atmosphere exchanges rely in part on carbon 

dioxide measurements in surface seawater. At present, open 

ocean values are used because coastal ocean data are generally 

not available. This compromised approach may result in the 

misattribution of some regional fluxes, especially in zones 

with large area-specific air-sea CO2 fluxes and mean crossshore air flow, such as the summertime northern Gulf (Hales 

and others, 2008). Preliminary analyses (Wanninkhof, 2008) 

indicate that air CO2 values used in inversion models may be 

lower (by about 2 parts per million) than actual Gulf values. 

High-quality air measurements are needed in coastal (land and 

sea) areas.

The Gulf is potentially important in the exchange of 

not only carbon dioxide but also other climatically active 

gases. The open ocean, estuaries, and coastal seas can be 

important sources of such gases [Upstill-Goddard, 2006; for 

example, carbon monoxide (CO) and methane (CH4)], but 

exchange rates are not well quantified in the Gulf of Mexico 

or other coastal waters. 

Estimation of air-sea gas fluxes presents a particular 

challenge in coastal waters (Upstill-Goddard, 2006). Gas 

exchange processes are complex, and spatial and temporal 

gradients in coastal areas are strong. Seawater pCO2 and gas 

exchange are influenced by ocean circulation, primary production, mineralization, and a host of other atmosphere and ocean 

processes and properties, some of which may be specific to the 

coastal ocean—that is, strong salinity and alkalinity gradients, 

terrigenous carbon supply, high turbidity, eutrophication, 

benthic processes, suboxic respiration, and pollutants (Liu and 

others, 2000).

In the open ocean, calculations of air-sea gas exchange 

are often based on measurements of wind speed (from which 

gas-transfer velocities are derived) and observed differences in 

air and surface-water pCO2 values. However, the 1996 Florida 

Shelf Lagrangian Experiment (FSLE) (Wanninkhof and 

others, 1997) and other studies have shown that this approach 

can yield inaccurate results in coastal regions (see Zappa and 

others, 2003; Baschek and others, 2006; Tokoro and others, 

2007). Therefore, direct eddy covariance air-sea flux measurements (McGillis and others, 2001a) or indirect measurements 

using tracers (Wanninkhof and others, 1997) or the gradient 

flux method (McGillis and others, 2001b) would be a useful 

part of any Gulf of Mexico carbon study. A process study for 

direct measurement of CO2 fluxes (for example, a yearlong 

platform study) is recommended.

Potentially important factors in the Gulf of Mexico 

include the effects of chemical enhancement, biofilms, surface 

ocean density fronts, and wave fetch. Carbon dioxide is not 

an inert gas, and its air-sea exchange rates may be enhanced 

by its chemical reactions in seawater under conditions of low 

turbulence and high pH (Morel and Hering, 1993; Wanninkhof 

and Knox, 1996). In equatorial areas, with low winds and high 

temperatures, chemical enhancement has been calculated to 

account for 4-8% of the total CO2 exchange (Wanninkhof and 

Knox, 1996). The subtropical Gulf of Mexico is also characterized by low winds and relatively high temperatures.

Biofilms may also be important in the Gulf, tending to 

suppress gas exchange. These organic materials may act as 

surfactants and can substantially reduce rates of gas transfer 

across the air-sea interface (Azetsu-Scott and Passow, 2004). 

Laboratory studies of oxygen evasion rates under turbulent 

conditions have documented rate reductions of 5-50% in the 

presence of phytoplankton exudates (Frew and others, 1990). 

Fronts, which are common in the Gulf of Mexico, may 

be sites of enhanced air-water gas transfer. Strong turbulence and bubble entrainment typically occur in conjunction 

with frontal downwelling (Marmorino and Trump, 1996), 

enhancing gas transfer in ways not captured by wind-based 

parameterizations (Baschek and others, 2006). In the northern 

Gulf, fronts are common due to strong buoyancy input from 

the Mississippi River. 

Wind fetch can also be important in influencing GMx 

sea state and therefore gas exchange. Gas transfer velocities 

increase with greater fetch (Zhao and others, 2003) and greater 

whitecap coverage (Monahan and Spillane, 1984; Wanninkhof 

and others, 1995). 

Strong spatial and temporal variability, typical of coastal 

waters, further complicate experimental design and data interpolation and extrapolation. River plumes, for example, though 

relatively limited in areal extent, may exert strong local effects 

on air-sea gas exchange. In the vicinity of the Mississippi 

River plume, spatial CO2 gradients and air-sea differences can 

be quite large (Cai and others, 2008). 
Gulf of Mexico Carbon Fluxes: Knowns, Unknowns, and Uncertainties 21

Priority research questions related to Gulf CO2

exchange cover a great range of temporal and spatial scales 

and range in scope from basic characterizations of seawater 

chemical distributions to studies of potentially far-reaching 

GMx influences on continental airmass chemistry. Air 

sampling programs and surface observations of seawater pCO2

are a high priority. The vertical distribution of CO2-system 

species in Gulf waters is also largely unknown and should be 

included in sampling programs. Determination of air-sea CO2

fluxes in the coastal seas of the conterminous United States is a 

component of the North Atlantic Carbon Program.

The effects of eddy variability and other physical 

processes (such as upwelling and downwelling) on CO2 source/

sink behavior in the Gulf merit additional study. Seasonal 

and episodic events (examples include hurricanes and diatom 

blooms) may induce rapid system changes from source to sink 

or vice versa, and the effects need to be better understood. 

Episodic wind events, for example, can produce coastal 

upwelling that drives rapid air-sea gas exchange (see Lueker 

and others, 2003). Coastal upwelling is known to contribute 

to the Gulf’s highly variable CO2 levels and correspondingly 

variable CO2 fluxes (Wanninkhof and others, 2007). 

Many pressing questions about Gulf carbon dioxide 

fluxes relate to biologically mediated processes. For example, 

what is the role of GMx primary production as a sink 

for atmospheric CO2? High nutrient input, as seen in the 

Mississippi River delta region, contributes to pCO2 drawdown (Wanninkhof, 2008). What other elemental cycles are 

important in controlling CO2 fluxes? The effects of nitrogen 

fixation, denitrification, and calcification by marine organisms 

need to be better characterized. Recently, anammox reactions have been found to represent a surprisingly significant 

pathway for the loss of fixed nitrogen in low-oxygen natural 

waters. The role of this process in the anoxic zone of the 

northern Gulf is a tantalizing unknown (Arrigo, 2005). 

Meteorological processes play an important role in 

moving atmospheric constituents between continental and 

marine areas (Parrish and others, 1992), and GMx oceancontinent fluxes through the atmosphere are an important 

research topic. The Mississippi River plume, due to its large 

area and strong air-sea gradients, may influence ocean-continent atmospheric fluxes. In the Gulf, the transport of volatile 

organic compounds (VOCs) and the effects of atmospheric 

pollution plumes are of particular interest. 

The implications of human practices (such as land use 

and river flood control) for Gulf of Mexico carbon fluxes 

cannot be ignored. Large-scale societal changes in Mexico 

and the United States have profoundly affected Gulf conditions, 

and such changes can be expected to continue and in some 

cases accelerate. During the 1900s, for example, changing 

agricultural practices in the Mississippi River basin (such 

as tile drainage, fertilizer use, irrigation, tillage practices, 

and changes in crop type) led to increases in river discharge. 

In conjunction with increased precipitation and agricultural 

lime applications, the net result has been a large increase in 

alkalinity flux, which in turn has implications for many other 

element and biogeochemical cycles (Raymond and others, 

2008). Mississippi River Delta sediments also record depositional changes during that time consistent with documented 

historical changes in upriver land use (such as deforestation), damming, and channelization (Santschi and others, 

2007). Restoration plans like those proposed for the Florida 

Everglades are also likely to produce major changes in carbon 

and nutrient fluxes to the Gulf (NRC, 2002).

With more land within Gulf watersheds now going 

“under the plow,” land use changes will have a profound 

influence on future Gulf conditions. In the United States, 

Conservation Reserve Program (CRP) enrollments are 

declining, as land is being converted from conservation to 

agricultural uses, largely in response to shrinking global 

food surpluses and anticipated increases in biofuel demand. 

Large-scale, rapid landscape changes can be expected, with 

the net effect being the conversion of terrestrial nitrogen to 

Gulf carbon. The effects of increasing biofuel production, in 

particular, may be profound. One GMx management goal is 

to reduce the application of nitrogen (as fertilizer) in upstream 

watersheds. However, cropland conversion from soy to corn 

production, as is being encouraged by anticipated ethanol 

demand, requires the application of additional nitrogen. 

The current expansion of corn-based ethanol production in 

the Midwest and the resulting increase in nitrogen export is 

expected to make nearly impossible the hoped-for reduction 

of the northern GMx hypoxic zone unless large shifts in food 

production and agricultural management are implemented 

(Donner and Kucharik, 2008). 

Climate change introduces another major unknown for 

the Gulf of Mexico. There remains considerable uncertainty 

regarding likely future temperature and especially precipitation over GMx watersheds—climate conditions that will 

ultimately influence watershed carbon yields. One particular 

difficulty in predicting the terrestrial supply of carbon to Gulf 

coastal and ocean regions arises from the large uncertainties 

in climate-change predictions for the Mississippi River basin 

(Najjar, 2008). Large uncertainties are also associated with 

how climate change is likely to affect soil nutrient stores 

and weathering rates. The community acknowledges the 

importance of constraining precipitation predictions. 
22 Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico

Summary: Common Themes and 

General Recommendations

An integrated, three-pronged approach to the study 

of Gulf of Mexico carbon fluxes is recommended, utilizing 

field observations, remote sensing, and coupled physicalbiogeochemical modeling. Some of the most pressing questions regarding net fluxes of total carbon across key interfaces 

can be addressed directly through the development of a coastal 

ocean observing system. Such a system would include both 

direct CO2-system measurements and supporting measurements (such as radioisotopes). Ocean buoys, flux towers, 

dedicated research cruises, and ships of opportunities are 

all important platforms for making CO2 flux measurements 

at critical interfaces (air-sea, land-ocean, land-air). Paleooceanography and paleoclimatology provide an important 

complementary perspective.

Remote sensing, which has radically transformed our 

understanding of ocean processes in recent decades, will 

play an extremely important role in GMx carbon studies. 

The development and improvement of remote sensing 

algorithms for the characterization of sea surface temperature 

(SST), sea surface salinity (SSS), chlorophyll concentration, 

phytoplankton standing stock, colored dissolved organic material (CDOM), and dissolved organic carbon (DOC) would be 

especially useful. The possibility of a lapse in well-calibrated 

ocean color measurements is a grave concern. 

Numerical models are an essential complement to 

observational programs and should be used to help design 

observation systems, plan effective field campaigns, and 

interpret results. A nested system of coupled physicalbiogeochemical models with data assimilation capabilities 

should be implemented in conjunction with the field programs. 

Adoption of a community circulation model should be a core 

undertaking. Support for the development of complementary 

models (producing high-resolution salinity fields, for example) 

is encouraged.

Judicious integration of field observations, remote 

sensing, and numerical modeling provides a powerful and 

essential tool for data interpolation and extrapolation, integration, and interpretation. Another potential application is the 

use of remote sensing to generate synoptic CO2 flux maps 

of larger areas than can be achieved by field sampling alone. 

A good example of an integrated interdisciplinary modeling, 

data assimilation, and analysis project is the U.S. Eastern 

Continental Shelf Carbon Budget (U.S. ECoS) program 

(Hofmann and Mannino, 2007). A similar program should 

be an integral part of a coordinated Gulf of Mexico carbon 

study. The Gulf of Mexico carbon project should strategically 

capitalize on existing data, infrastructure, and models.

Data Availability and Continuity

A formal data-mining effort should be initiated as soon 

as possible to compile existing datasets and identify critical 

data gaps. A Web-accessible forum should be provided to 

receive and distribute quality-controlled and quality-assured 

data. Funding for this substantial data compilation effort will be 

necessary in the initial stages of a Gulf of Mexico project. 

Basic terrain data and long-term hydrological monitoring 

of U.S., Mexican, and Cuban GMx watersheds are critical to 

our understanding of biogeochemical cycles in the Gulf of 

Mexico. Initial data compilation and synthesis efforts should 

include the gathering of digital elevation models (DEMs) 

for Mexico and Cuba. The United States has uniquely robust 

continental-scale datasets (Sundquist, 2008), but a major data 

gap is the lack of a nationally consistent wetlands database 

(Boyer, 2008). National digital inventories of forests, land 

use, and ecoregions have been published for Mexico, and a 

forest update is scheduled for 2009 (Muhlia Melo, 2008). Gulf 

watershed information about not only land use but also land 

characteristics (such as soil mineral content) will be required. 

High-spatial-resolution data for continental carbon inventories 

(for example, biomass and soil carbon) are available. 

Some long-term time-series datasets (as examples, flow 

regimes, historical land use, nutrient loadings) collected by 

academic, federal, state, and local agencies in Gulf regions 

need to be collated and intercalibrated. Standardization of 

units of measure and correction for methodological differences 

will be required. 

Ongoing programs and data collection initiatives that will 

contribute significantly to GMx observational efforts are U.S. 

Department of Agriculture (USDA) land use data, National 

Aeronautics and Space Administration (NASA) satellite observations, National Oceanic and Atmospheric Administration 

(NOAA) ocean observing systems, and EPA and USGS 

water-quality data. Minerals Management Service (MMS) has 

an ongoing research program focused on the Gulf of Mexico 

(see http://www.gomr.mms.gov/homepg/regulate/ environ/

studiesprogram.html), as well as an online Report Archive (see 

http://www.gomr.mms.gov/ homepg/regulate/environ/techsumm/

rec_pubs.html). The U.S. Long-Term Ecological Research 

(LTER) network offers an additional source of valuable data.

These varied background data are needed to assess such 

things as the likely flux-related impacts of changes in land 

use and land cover, the stability of erosion control measures, 

and the extent and effects of sustainable land use practices. 

Integration of these historical and new datasets will contribute 

greatly to the ability to model and predict key carbon fluxes 

in river-estuary systems, including air-sea CO2 flux, lateral 

exports to the shelf, and carbon sequestration in sediments. 
Summary: Common Themes and General Recommendations 23

Continuity of data collection, in terms of both frequency 

and duration, is a critical element of a successful Gulf of 

Mexico research program. Long-term historical datasets are 

necessary for model implementation, validation, and calibration, and the procurement of adequate funding for this core 

element is essential.

Of particular concern regarding continuity of data:

□ USGS stream-gaging station data: Fewer rivers and 

streams are monitored today than in 2000 (U.S. EPA, 

2007). 

□ Satellite ocean color data: The potential for a lapse 

in well-calibrated ocean color measurements is a 

particular concern. 

□ Remote sensing algorithm development: Field 

observations required to support the development 

of remote-sensing algorithms must be adequately 

supported.

Recent declines in stream-gaging and water-quality 

monitoring programs will hamper efforts to monitor, model, 

and predict likely impacts of many terrestrial and aquatic 

processes related to GMx carbon fluxes. During the 1990s, 

the number of U.S. river gages dropped by about 6%; between 

1971 and 1999, gages on small, free-flowing rivers dropped 

22% (Stokstad, 1999). Declines since then have continued 

(U.S. EPA, 2007). It is imperative that discontinued monitoring stations be re-established, that current stations be 

maintained, and that networks be expanded. These long-term 

data, along with new types of data, are required to validate the 

numerical models upon which scientific advances depend and 

upon which policy decisions will be based. 

Gulf of Mexico studies would benefit greatly from a 

geostationary ocean color satellite, such as the proposed 

GEO-CAPE mission (NRC, 2007). This mission would provide 

data on aerosols, phytoplankton, organic matter, suspended 

sediments, and other constituents of ocean color at frequencies 

of several passes per day, thus permitting direct observation of 

dynamic, short-time-scale events and processes. In situ field 

observations and measurements are essential for the development of remote sensing algorithms, ocean color and otherwise. 

The selection of GMx study sites should be chosen by 

using existing classification schemes and study sites—such 

as those of the international Land-Ocean Interactions in the 

Coastal Zone project (LOICZ) or the U.S. National Estuarine 

Research Reserve System (NERRS). In the United States, the 

National Ecological Observatory Network (NEON) (Keller 

and others, 2008) may be an especially good partner in this 

regard. The lack of study sites in aquatic systems in the North 

American Carbon Program (Ogle and Davis, 2006) must be 

redressed immediately. 

Additional sampling opportunities (for example, ships 

of opportunity) should be explored as a means of expanding 

Gulf data coverage. Complementary platforms might include 

commercial shipping vessels, pleasure cruise ships, and 

hydrocarbon-extraction ships and platforms.

Meteorological and military towers represent one 

potential opportunity for building on existing infrastructure 

and encouraging coordinated cross-disciplinary research:

□ U.S. Air Force towers - Roughly half a dozen of these 

unused military towers are located along the west 

Florida coast and could potentially be instrumented for 

GMx studies.

□ Tall towers - Meteorological tall towers sample 

atmospheric parameters at heights of tens or hundreds 

of meters and give a “footprint” view on the scale of 

hundreds of kilometers. At present, only a few North 

American tall towers exist.

□ Flux towers - Flux towers measure the exchanges 

of CO2, water vapor, and energy between terrestrial 

ecosystems and the atmosphere, and their sites are well 

characterized in terms of vegetation, soil, hydrologic, 

and meteorological characteristics. The United States 

has active flux towers in Florida (Everglades and 

Gainesville) and Texas (San Marcos) and inactive 

towers in Florida and Mississippi. Mexico’s one 

active flux tower is located in the mountains of La 

Paz (http://public.ornl.gov/ameriflux/site-select.cfm). 

Long-term continuity of funding for flux towers is not 

assured (Baldocchi, 2008). 

Numerical Modeling

Numerical modeling will be an essential component 

of a GMx carbon program and should be used to help plan 

effective field campaigns and interpret results. Fiscal realities inevitably limit the scope of field programs; therefore, a 

nested system of coupled physical-biogeochemical models 

with data assimilation capabilities (for both field and remote 

sensing measurements) should be implemented prior to and 

in conjunction with the field program. Historical data from 

the initial data-mining effort can be used to constrain existing 

models, which can in turn be “sampled” to help determine 

optimal scales and locations for observations. New data will 

be supplied to the models as they come available. For some 

carbon-relevant questions, modeling of a particular environment may be appropriate (such as certain river/estuarine 

systems). For other questions, an exploration of couplings and 

feedbacks among the atmosphere, terrestrial watersheds, river 

systems, margins, open Gulf of Mexico, or adjacent basins 

may be required. Increases in Gulf sea surface temperature 

may, for example, result in higher atmospheric water vapor 

concentrations and concomitant increases in precipitation over 

land—which will in turn influence GMx conditions.
24 Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico

Socioeconomic and climate-change aspects that may 

need to be considered in Gulf models include: 

• Changes in land and water management (agricultural 

practices, human population distributions, groundwater 

mining, etc.) 

• Changes in sea level, sea-surface temperature, and 

ocean chemistry (for example, ocean acidification; 

Kleypas and others, 2006)

• Changes in coastal morphology (for example, through 

subsidence or coastal erosion)

Quantifying model uncertainty—and therefore the 

precision and accuracy of the underlying field data—should be 

a core element of field and modeling programs. Estimates of 

uncertainty can help qualify predictions and guide the prioritization of future research and data collection. Postponing the 

modeling effort until the program’s end is to be avoided.

A forum devoted to collaborative assessment of existing 

data, model capabilities, and potential barriers to modellinking and -coupling is recommended. Forum participants 

should include modelers and observationalists drawn from a 

wide variety of complementary geographic and computational 

areas of expertise. Early model assessments must consider not 

only data availability and model capabilities but also software 

compatibility and “language barriers” (such as different state 

variables, different data formats). Many existing carbon 

models do not strictly trace carbon but are driven by pertinent 

constituents that influence carbon, such as nutrients. A core 

undertaking of this assessment effort should be the identification of candidate community ocean circulation models for the 

Gulf of Mexico. Circulation models constitute the “backbone” 

of spatially explicit biogeochemical ocean models, and GMx 

circulation modeling is a particular challenge.

Linked, nested models are recommended, and existing 

GMx models provide a good starting point. A general 

modeling strategy would be to nest and link existing models 

of various subsystems or components (for example, watershed 

yield, air-sea exchange, coastal shelf processing). Many major 

subsystems can be characterized adequately with existing 

models—for example:

□ SPARROW - SPAtially Referenced Regressions on 

Watershed Attributes, for modeling surface-water 

quality (http://water.usgs.gov/nawqa/sparrow/)

□ SWAT - Soil and Water Assessment Tool, a riverbasin-scale model for quantifying the impact of land 

management practices in large, complex watersheds 

(http://www.brc.tamus.edu/swat/)

□ Terrestrial CO2

□ VOC

□ TEM - Terrestrial Ecosystem Model, a processbased ecosystem model that describes plant and soil 

(non-wetlands) carbon and nitrogen dynamics (http://

www.cgd.ucar.edu/vemap/abstracts/TEM.html)

Model nesting is recommended to accommodate the great 

range of process scales encountered in Gulf regions. In dry, 

low-productivity terrestrial areas, for example, coarse spatial 

and temporal resolution may be adequate. In other areas, finer 

scale resolution will be required. A loose coupling (linking) of 

subsystem models is also recommended, in which the output 

from one subsystem model provides the input for another. For 

example, output from the SWAT and SPARROW models may 

provide some input required by coastal and oceanographic 

biogeochemical models. In some cases, tighter coupling may 

be required. For example, climate models need to be coupled 

to process-driven land models so that feedbacks can be identified and explored. As a general approach, models need to at 

least loosely couple carbon with other important constituents. 

The development of complementary data assimilation 

models should be encouraged. Such models do not include 

carbon as a state variable but instead provide output fields 

needed by carbon researchers. One example is the U.S. Navy’s 

experimental real-time Intra-Americas Sea Ocean Nowcast/

Forecast system (IASNFS) (Ko and others, 2003), which 

could potentially supply high-resolution salinity fields for the 

calculation of CO2 fluxes. Such models offer a powerful tool 

for regional data interpolation and extrapolation.

Issues of Scale

The determination of appropriate temporal and spatial 

scales for field observations and modeling efforts depends on 

the nature of the biggest unknowns in the constraint of Gulf 

of Mexico carbon fluxes. The overarching spatial scale can be 

conceptualized as a two-part system: the GMx marine basin, 

plus all North American watersheds that discharge into the 

Gulf (fig. 1). The relevant temporal scales require measurement 

frequencies ranging from hourly to seasonal, with durations 

ranging from one to several decades. A comprehensive GMx 

research program will require a blend of high-resolution (high 

frequency, short duration, small area) and low-resolution (low 

frequency, long duration, large area) measurements. 

Critical scales need to be defined for a variety of carbonrelevant processes, parameters, and provinces. An important 

question is what kinds of carbon species need to be measured 

in different ecosystems and at what scales. Smaller scales need 

to be understood if we are to anticipate and predict changes 

occurring on larger scales. Longer temporal scales are required 

for more detailed system analyses. The relative contributions 

of steady-state conditions versus episodic events also need to 

be investigated. 

In general, a minimum set of carbon fluxes for a particular 

region or spatial scale (for example, entire Gulf of Mexico) 

should be defined in terms of the carbon species or carbon-relevant 

parameters to be measured. Researchers can then identify where 
Summary: Common Themes and General Recommendations 25

adequate assessments are available and where additional ones are 

required—that is, they can identify what kind of data to collect (at 

what scale, frequency, and duration) to answer specific questions. 

A standard list of measurements should be formulated, 

related to the scales under consideration. For example, one 

goal might be to establish Mississippi River fluxes at heads of 

passes. There, “choke points” are small, and daily sampling is 

feasible. In the Mississippi River plume, however, long-term 

daily measurements are not feasible, except by remote sensing. 

Some processes can be sampled intensively, some not—and 

overlap of scales should be sought where possible. Point stations 

and moorings can provide high-frequency data, which must be 

combined with satellite data and shipboard measurements for 

spatial integration. Autonomous underwater vehicle (AUV) 

measurements of DIC-system parameters are also evolving and 

may soon offer another means of spatial integration. 

Continental data synthesis inevitably presents scaling 

challenges. Variability is tied to the scale of the system, and 

there is a need to capture episodic events but also integrate 

them. Researchers will inevitably grapple with the question 

of, in collapsing temporal scales and integrating, what an 

appropriate scale of inference is. Analysis at continental scales 

must include watersheds and aquifers, which can be characterized, in part, in terms of land use (agricultural, forested). 

Measurement platforms include satellites and tall towers. 

The temporal scale for point measurements will be daily to 

annual, but maintenance of the instrumentation for these sorts 

of measurements is a challenge. For stream and river measurements, gages provide water fluxes (hourly) and often include 

less frequent (weekly) measurements of water quality. One 

important goal is the derivation of robust relations between 

water flux and carbon parameters. Water quality measurements 

are important and temporal coverage of events is desired, but 

sufficient data coverage does not currently exist. 

The Gulf presents its own scaling challenges, and it must 

be kept in mind that the Gulf is characterized by continuums of properties and processes rather than hard physical 

boundaries. Once semi-distinct, process-defined provinces 

are defined and conceptual boundaries are established (fig. 4), 

it becomes necessary to measure fluxes across them, and this 

undertaking will be particularly difficult for the margin-basin 

boundary. In general, more intensive sampling (that is, smaller 

spatial and temporal scales of measurement) will be required 

in margin regions than in the central Gulf. 

One goal for a GMx carbon program would be the 

formulation of a well-constrained carbon budget (inflows and 

outflows). Such a budget will not provide a detailed mechanistic understanding of carbon-relevant processes, but it will 

provide critical insights into the fate of land-derived carbon 

in the GMx system. As examples, the most important carbon 

fluxes and desired temporal and spatial measurement resolutions are provided here for two GMx provinces. 

The eastern Gulf shelf (fig. 4) provides a good example 

of a margin region. Five important fluxes were identified by 

workshop participants:

□ Air-sea CO2 flux: the desired temporal resolution in 

this province would be hourly, with decadal duration. 

Temporal resolution may be better defined with a 

nested approach, starting with high frequency (hourly) 

measurements and decreasing the frequency when and 

where feasible.

□ Land-sea carbon flux: this flux can be mediated 

by water flux via rivers or groundwater. Critical 

measurements include DIC, DOC, POC, PIC, and 

nutrients. Required temporal resolution is hourly, with 

decadal duration. 

□ Benthic-pelagic flux: again, pertinent parameters are 

DIC, DOC, POC, PIC, and nutrients. The desired 

temporal resolution is seasonal, with flexibility for 

event-based coverage. Temporal duration is decadal. 

□ Margin-to-basin flux: required parameters include DIC, 

DOC, POC, PIC, nutrients, and radium isotopes (for 

time scale definition). The desired temporal resolution 

is weekly, with decadal duration.

□ Net primary productivity and respiration: the desired 

temporal resolution is monthly, with event-based 

coverage when possible. Duration is decadal. 

Additional considerations include the role and definition 

of river plumes (with boundary definitions based on salinity 

or a combination of salinity and geography), fluxes outside 

the plume “box” and estuary-ocean exchange, fluxes from 

the water column to sediments and the potential for carbon 

burial, and shallow-to-deep water exchange (at the basin scale 

or smaller). Uncertainties about boundaries and the potential 

contributions of satellites should be explored as well. 

For the deep GMx basin (fig. 4), measurements at the 

circulation “choke points”—the Yucatan and Florida Straits—

will be important in quantifying carbon fluxes in and out of the 

basin. The Loop Current and eddies (large but transient—up to a 

year in duration) are the dominant physical features in the basin. 

Three major fluxes were considered to be most significant:

□ Air-sea CO2 fluxes for the entire Gulf of Mexico: 

air-sea carbon fluxes show significant interannual 

variability, so seasonal sampling is needed. Sampling 

duration should be decadal. 

□ Water mass flux through the Gulf of Mexico: 

measurement parameters associated with this flux 

are DOC, DIC, PIC, POC, pCO2, and nutrients. 

Measurement frequency should be seasonal, with 

decadal duration. 

□ Primary production: estimations of primary production 

in surface waters of the deep basin can be derived from 

satellite observations of chlorophyll-a concentrations 

(that is, ocean color). The relevant temporal scales are 

weekly to annual, with decadal duration. 
26 Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico

Infrastructure and Integration

Integration of the many individual research efforts in 

the Gulf of Mexico will require strategic investments in 

infrastructure and could lead to a significant increase in our 

understanding of the cycling of carbon and carbon-relevant 

materials through land, atmosphere, river, estuarine, and ocean 

reservoirs. Infrastructure is taken to mean common shared 

resources for use by the research community in terms of an 

integrated measurement program, a data management center, 

modeling efforts, and outreach activities. The following six 

efforts are recommended: 

□ An integrated network of carbon monitoring stations on 

land and ocean, building on existing infrastructure and 

augmenting these capabilities where needed

□ A regular set of process cruises in the Gulf of Mexico

□ The development of improved algorithms for 

interpretation of satellite remote sensing products

□ A shared integrated modeling effort that is connected to 

the measurement efforts

□ The establishment of a Gulf of Mexico data 

management center to provide a “one-stop” connection 

to all measurement, modeling, and remote sensing 

products

□ A common communication effort that uses existing 

networks and outreach opportunities to involve 

stakeholders and decisionmakers in the research efforts

These six recommendations are further detailed below. 

The community seeks to initiate a networked system of 

monitoring stations in terrestrial and aquatic environments in 

the GMx region, where a large-scale, integrated system can be 

leveraged against numerous smaller, dedicated systems that 

are already in place. A set of time series stations with carbonrelevant measurements is recommended. Many of these exist 

in some form already; others will need some modification 

or augmentation to meet the needs of the GMx-wide study. 

Specific examples include buoys, platforms, river gaging 

stations, and flux towers that are currently outfitted—or could 

be outfitted at minimal cost—with necessary instrumentation. 

For example, key physical parameters such as wind, salinity, 

and temperature are available from some existing platforms, 

such as those operated by the National Data Buoy Center 

(NDBC; http://www.ndbc.noaa.gov/) but will need to be 

augmented with in situ carbon sensors. In addition, networks 

such as the tall tower and aircraft sites operated by NOAA’s 

Earth System Research Laboratory would need to be expanded 

for adequate spatial and temporal coverage of this region. 

Many universities and government agencies have assets along 

the Mississippi River and coastal sites along the Gulf that 

can provide access and staging areas for time-series sampling 

efforts. Gulf of Mexico ocean observing systems that are 

already in place can be utilized for leveraging and infrastructure support [see http://www-ocean.tamu.edu/GCOOS/System/

gom.htm for information on Gulf of Mexico Coastal Ocean 

Observing System (GCOOS)]. Offshore drilling platforms 

provide an excellent opportunity for leveraging existing 

infrastructure for scientific use, but the science community 

needs to work closely to align science goals with industry needs 

to succeed with this dual use. For the capture of extreme events 

(hurricanes), a few critical sites need to be outfitted with rugged 

instrumentation designed to “weather the storm.” Regular 

meetings of a Gulf of Mexico infrastructure working group and 

further discussion of existing measurement efforts, common 

data quality standards, and evolving technologies are needed to 

establish this network. 

A set of routine coastal process studies measuring 

carbon system properties, hydrographic properties, and 

nutrients would greatly contribute to the goal of better understanding the transport and transformation of carbon-relevant 

species throughout the system. As in the case of networked 

monitoring stations, governmental agencies (federal, state, 

tribal, local), universities, and other organizations already 

have several projects underway that are collecting some of 

these vital measurements. This region is also host to numerous 

research laboratories that can provide facilities and logistical 

support for field measurements and laboratory experiments. 

Dedicating time and resources to establish continuity among 

these studies (including coordinating sampling efforts, intercalibrating data, and merging datasets) will advance the success 

of the proposed GMx field campaign. Through a regular set of 

process studies and time series measurements, researchers can 

begin compiling the data required for a more complete understanding of the transport, transformation, and fate of carbon 

and other climate-critical parameters in the Gulf of Mexico.

Remotely sensed measurements from aircraft and 

satellites are also required for synoptic coverage of Gulf 

processes. These products will be used to bridge the gaps where 

field data cannot be collected and will assist in developing 

sampling strategies. Emphasis on improved coastal zone sensors 

(such as complete CODAR coverage), coordinated airborne 

coverage (for example, LIDAR), and improved satellite remote 

sensing coverage (increased spatial and temporal resolution) and 

algorithms (especially for chlorophyll, CDOM, and salinity) is 

needed to guide process studies and drive models more accurately. This effort will require coordinated ground-truthing of the 

satellite measurements during time-series and process studies. 

Finally, higher-resolution remote sensing data (< 1 km resolution) 

are necessary for studying coastal processes such as outwelling, 

sediment transport, and wetland losses. 

Fusion of all data products will require an extensive, 

integrated modeling effort. Validation of models would be 

conducted via hindcasting, with the purpose of ultimately 

generating forecasting models to provide predictive capabilities for management issues—in particular, land use effects on 

watersheds (both upstream and downstream). These models can 
Summary: Common Themes and General Recommendations 27

in turn provide valuable information to guide sampling strategies 

and maximize data and information output. Numerical modeling, 

including data assimilation, will also be necessary in designing 

the observing network and scaling up the results of process 

studies. Modelers and modeling capabilities need to be considered and integrated during the planning stages of the time-series 

network and process studies to maximize the efficacy of the 

measurement efforts and ensure maximum impact of modeling 

products. 

Implicit in a networking of stations and field studies is 

the recognition that different strategies will be needed for the 

unique reservoirs of interest. Each research community offers 

distinct strengths that may be applicable to other communities 

as well. An example is the detailed North American forest 

inventory of the USDA—translating that type of database to an 

aquatic environment for an equivalent coastal inventory would 

be very useful. Implementing new approaches in different 

regimes may offer a wealth of carbon-relevant information. 

Such cross-disciplinary, cross-environment approaches may 

also encourage the development of better sampling strategies in 

regard to extreme weather events, a problem that has challenged all field researchers and has compromised numerous 

datasets. Such an endeavor would give researchers an unprecedented opportunity to work collaboratively across disciplines 

and geographic realms to constrain climate-critical carbon 

measurements.

Skillful data management will be required to handle 

the numerous large datasets that would be generated by 

a large-scale GMx field campaign. To assure the provision 

of accessible, high-quality data to end users, a central data 

repository will be needed, as will adherence to universal formats 

and standardized collection protocols. Coordination will be 

necessary between Ocean Carbon and Biogeochemistry (OCB) 

and the North American Carbon Program (NACP) data management offices. The end result of this management effort needs 

to be data products that are easily accessible, user-friendly, and 

transportable to geographic information system (GIS) programs. 

The envisioned data management center would also bring 

together historical data to facilitate studies of past changes and 

the generation of longer time series. These efforts will allow for 

extensive data mining and maximal usage of existing data. 

Research conducted in the GMx region falls under 

the recommendations of two nationally recognized carbon 

cycle research programs aimed at coordinating existing and 

new carbon cycle science research programs: the North 

American Carbon Program (NACP) and the Ocean Carbon 

and Climate Change Program (OCCC). The NACP and 

OCCC, which are supported by the U.S. Global Change 

Research Program Carbon Cycle Science Program and the 

U.S. Climate Change Science Program, address the global 

carbon cycle research theme in the Strategic Plan for the U.S. 

Climate Change Science Program (2003). Both programs 

have recognized the need for international collaboration in 

carbon cycle and climate research activities. A GMx research 

campaign would require such coordination with the Mexican 

governmental agencies and universities.

The success of this type of endeavor depends on the 

successful communication of results to the public. There 

is a need to educate the public at all levels in carbon cycle 

biogeochemistry and its social and economic implications. 

Web-based tools, graphic interfaces, and museum displays can 

all contribute to this goal. 

Involving stakeholders and decisionmakers in the 

research program, from the planning stages to the end products, is critical in generating the sorts of interactions between 

scientists and their ultimate audiences that will result in 

maximizing the use of science in policy-making decisions. 

Interactive discussions of science strategies, measurement 

protocols, modeling products, and predictions need to be 

“two way,” rather than simply flowing from the science 

community outward to the public. Feedback from the public 

can be gathered via high-tech interactive outlets (for example, 

Internet, YouTube, video games) and participation in existing 

large-scale networks such as the Centers for Ocean Science 

Education Excellence (COSEE) and the Global Learning and 

Observations to Benefit the Environment (GLOBE) projects. 

International collaboration between the United States 

and Mexico will further broaden the impact of research 

efforts. A strategic plan for communication and outreach is necessary for maximizing the impact of this coordinated research. 

In summary, determination of the magnitude and distribution of carbon sources and sinks requires quantification of 

the reservoirs of carbon and carbon-relevant parameters as 

well as the biological, chemical, and physical processes that 

influence their spatial and temporal variability. A comprehensive Gulf of Mexico research initiative will provide better 

constraints on carbon fluxes and concentrations in and across 

key interfaces such as watersheds, the Yucatan Strait, the shelf 

break, the sediment-water interface, and the atmosphere through 

in situ measurements, multidisciplinary process studies, and 

modeling. By coordinating time series measurements, process 

studies, data management, modeling, and outreach efforts, the 

Gulf of Mexico research community can make a great leap 

forward in its understanding of the carbon cycle in the Gulf and 

the relevance of these results to the global carbon cycle. 
28 Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico
Workshop Agenda 29

Workshop Agenda

Tuesday, May 6, 2008

7:30 Registration and Continental Breakfast at the USGS

(Posters can be put up immediately)

8:30 Introduction, Welcome, and Logistics 

Welcome by USGS and USF College of Marine Science 

Comments by program managers: NSF, NOAA, NASA, USGS, MMS

Goals of Meeting - Paula Coble and Lisa Robbins

9:30 Plenary Talks, Carbon Cycle Land-Ocean Coupling - Processes, Fluxes, and Fates Session 

Moderator: Wei-Jun Cai

9:30 Eric Sundquist, USGS, From Carbon Footprint to Carbon Pathway: Carbon-Cycle 

Science at Crossroads

10:10 Break

10:30 Ken Davis, Pennsylvania State University, Land-Atmosphere Dynamics and 

Measurement of CO2

11:10 Tom Bianchi, Texas A&M University. Anthropogenic and Natural Effects on the 

Biogeochemistry of Organic Carbon Cycling in a River-Dominated Margin: 

The Mississippi River System

11:50 Questions for presenters

12:00 Lunch and posters

 1:00 Moderator: Ben de Jong

1:00 Steve Lohrenz, Gulf of Mexico Carbon Cycling

1:40 Rik Wanninkhof, CO2 Flux Dynamics over the Gulf of Mexico

2:20 Dick Feely, Pressing questions and research needs from morning session

Open discussion: 

(1) Most pressing questions or hypotheses

(2) General ideas on how to test them

3:00 Break

3:15 Breakout Session 1: Assessing the state of knowledge on carbon transport and flux in each 

of the three segments of the land-ocean system. What do we know? What are perceived data 

gaps? See actual breakout questions in Workshop folder.

Breakout groups: 

1. River/ Estuary Group - Meet in Normile Room

 Co-Chairs: John Paul and Miguel Goñi

 Reporter: Regina Easley

2. Terrestrial/ Watershed Group - Meet in Breakout Room 1

 Co-Chairs: Simone Alin and Charles Perry

 Reporter: Lori Adornato

3. Ocean/Terrestrial/Atmospheric Group - Meet in Breakout Room 2

 Co-Chairs: Liz Gordon and Carlos Del Castillo

 Reporter: Laura Lorenzoni

4:40 Report from Breakout 1 back to Normile Conference Room

6:30-10:00 Dinner reception and posters on StarLite Cruise: Loading at 6:30 p.m., leaving at 7:00 p.m. 

from USF docks; map will be provided. Cash bar. Bring sweater.
30 Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico

Wednesday, May 7, 2008

7:30 Continental Breakfast 

8:30 Update: Paula Coble and Lisa Robbins, Normile Conference Room

8:45 Plenary Talks

Moderator: Lisa Robbins

8:45 Peter Raymond, Yale, Watershed Carbon Cycle and Export

9:15 Hobie Perry, USDA Forest Service, National Inventories of Terrestrial Ecosystem 

Carbon Stocks, Documenting Impacts of Resource Management on Watershed Carbon Dynamics

9:45 Ray Najjar, Penn State, Eastern U.S. Continental Shelf Carbon Budget: Modeling, Data 

Assimilation, and Analysis

10:15 Break

Moderator: Paula Coble

10:30 Beth Boyer, UC Berkeley, Modeling Watershed Nutrient Fluxes

11:00 Mead Allison, UT Austin, Modeling Sediment Transport and Deposition on GM. Shelf

11:30 Ruoying He, NCSU, Physical Oceanography and Circulation of the Gulf of Mexico

12:00 Lunch and posters 

1:15 Ben de Jong and Arturo Muhlia Melo, Update on Mexican Carbon Programs and Projects

1:30 Breakout Session 2: Pulling together a design for a future research project, taking into account 

the scales of variability, infrastructure required and modeling framework for integration across 

the system. See actual questions in Workshop folder.

Breakout groups: 

1. Modeling and Prediction Group - Meet in Normile Room

 Co-Chairs: Barnali Dixon and Chris Anderson

 Reporter: David Butman

2. Infrastructure Group - Meet in Breakout Room 1

 Co-Chairs: Kathy Tedesco and Bob Chen

 Reporter: Robyn Conmy

3. Scales Group - Meet in Breakout Room 2

 Co-Chairs: Ron Benner and Nazan Atilla

 Reporter: David John

4:00 Summary Report back from Breakout 2 to plenary 

6:00 Dinner on your own 
Workshop Agenda 31

Thursday, May 8, 2008

7:30 Breakfast 

8:30 Wei-Jun Cai, Summary of Breakouts 1 and 2 and Discussion of new directions 

9:00 Brent McKee and Miguel Goñi

1. Discussion of priority environments to focus research

* Coastal environments around the Gulf, including Cuba, Straits of Florida, West Florida 

Shelf, north-east shelf, Mississippi/Atchafalaya River region, Louisiana/Texas shelf, 

East Mexico shelf, Bay of Campeche, Campeche Bank and the Yucatan channel. Which 

environments will be most influenced by climate change (CO2 in systems)?

*Where is there synergy with past or planned research projects?

2. Implementation and proposal planning

12:00 Adjourn

1:00- 5:00 Report write-up session: including organizers, session chairs, reporters, and involved students
32 Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico

Participant List

Meeting Leaders: 

Paula G. Coble

University of South Florida

140 7th Ave. South

St. Petersburg, FL 33701

Phone: 727-553-1631

E-mail pcoble@marine.usf.edu

Lisa Robbins

U.S. Geological Survey

600 4th St. South

St. Petersburg, FL 33701

Phone: 727-803-8747 x3005

E-mail: lrobbins@usgs.gov

Lori R. Adornato

SRI International

140 7th Ave. South COT 100

St. Petersburg, FL 33701

Phone: 727-553-3502

Fax: 727-553-3529 

E-mail: Lori.Adornato@sri.com 

Simone R. Alin 

NOAA Pacific Marine Environmental Laboratory 

7600 Sand Point Way NE

Seattle, WA 98115

Phone: 206-526-6819 

E-mail: simone.r.alin@noaa.gov 

Mead Allison 

University of Texas Institute for Geophysics 

10100 Burnet Rd.

Bldg 196, R2200

Austin, TX 78758-4445

Phone: 512-471-8453 

E-mail: mallison@mail.utexas.edu 

Christopher J. Anderson 

Auburn University 

3301 Forestry and Wildlife Building

Auburn, AL 36849

Phone: 334-844-1033

E-mail: andercj@auburn.edu 

Nazan Atilla 

University of Wisconsin-Madison 

Dept. Atmospheric and Oceanographic Sciences-Center for 

Climate Research

1225 West Dayton St.

Madison, WI 53706

Phone: 608-890-0472 

E-mail: atilla@wisc.edu 

Phil Bass 

EPA Gulf of Mexico Program 

Bldg. 1100, Rm 232

Stennis Space Center, MS 39529-6000

Phone: 228-688-2356 

Fax: 228-688-2709 

E-mail: bass.phil@epa.gov 

James E. Bauer 

VIMS, College of William & Mary 

P.O. Box 1346

Gloucester Point, VA 23062

Phone: 804-684-7136 

E-mail: bauer@vims.edu 

Ronald Benner 

University of South Carolina 

Dept. of Biological Sciences

Columbia, SC 29208

Phone: 803-777-9561

E-mail: benner@biol.sc.edu 

Heather Benway 

OCB Project Office

Dept. of Marine Chemistry and Geochemistry

Woods Hole Oceanographic Institution

MS 43

Woods Hole, MA 02543

Phone: 508-289-2838 

Fax: 508-457-2161 

E-mail: hbenway@whoi.edu 

Thomas S. Bianchi 

Texas A&M University 

Dept. of Oceanography, 3146 TAMU

College Station, TX 77843-3146

Phone: 979-845-5137 

Fax: 979-845-6331 

E-mail: tbianchi@tamu.edu 

Paula Bontempi 

NASA Headquarters 

Mail Suite 3B74

300 E St. S.W.

Washington, DC 20546

Phone: 202-358-1508 

E-mail: paula.s.bontempi@nasa.gov 

Elizabeth W. Boyer

School of Forest Resources and Penn State Institutes of 

Energy and the Environment

304 Forest Resources Building

Pennsylvania State University

University Park, PA 16802

Phone: 814-865-8830

E-mail: ewb100@psu.edu

Jay A. Brandes 

Skidaway Institute of Oceanography 

10 Ocean Science Circle

Savannah, GA 31411

Phone: 912-598-2361 

Fax: 912-598-2310 

E-mail: jay.brandes@skio.usg.edu 
Participant List 33

David E. Butman 

Yale University 

210 Prospect Street

New Haven, CT 06511

Phone: 203-577-9911 

E-mail: david.butman@yale.edu 

Robert H. Byrne 

University of South Florida 

College of Marine Science

140 Seventh Ave. South

St. Petersburg, FL 33701

Phone: 727-553-1508 

Fax: 727-553-1189 

E-mail: byrne@marine.usf.edu 

Wei-Jun Cai 

University of Georgia 

Department of Marine Sciences

Athens, GA 30602

Phone: 706-769-1466 

E-mail: wcai@uga.edu 

Robert F. Chen 

University of Massachusetts Boston 

Environmental, Earth and Ocean Sciences

100 Morrissey Boulevard

Boston, MA 02186

Phone: 617-287-7491 

E-mail: bob.chen@umb.edu 

Robyn N. Conmy 

University of South Florida 

140 7th Ave. South

St. Petersburg, FL 33701

Phone: 727-692-5333 

Fax: 727-553-1189 

E-mail: rconmy@marine.usf.edu 

William T. Cooper 

Florida State University 

Department of Chemistry & Biochemistry

Tallahassee, FL 32306-4390

Phone: 850-644-6875

Fax: 850-644-8281

E-mail: cooper@chem.fsu.edu

Reide Corbett 

East Carolina University 

Department of Geological Sciences

Graham Bldg.

Greenville, NC 27858

Phone: 252-328-1367 

E-mail: corbettd@ecu.edu 

Kenneth J. Davis 

Penn State University 

512 Walker Building

Department of Meteorology

University Park, PA 16802

Phone: 814-863-8601 

E-mail: kjd10@psu.edu 

Mike D. DeGrandpre 

University of Montana 

Department of Chemistry

Missoula, MT 59812

Phone: 406-243-4118 

E-mail: michael.degrandpre@umontana.edu

Bernardus H.J. de Jong 

El Colegio de la Frontera Sur 

Carra Reforma KM 15.5

Ra Guineo 2da Sección

C.P. 86280

Villahermosa, Tabasco, Mexico 86280

Phone: +52-993-3136111 

Fax: +52-993-3136110 ext. 3001 

E-mail: bjong@ecosur.mx 

Carlos E. Del Castillo 

The Johns Hopkins University 

Applied Physics Laboratory 

11100 Johns Hopkins Rd.

Laurel, MD 20723

Phone: 240-228-8457 

E-mail: carlos.del.castillo@jhuapl.edu 

Barnali Dixon 

University of South Florida 

140 7th Ave. South

St. Petersburg, FL 34236

Phone: 727-873-4025 

E-mail: bdixon@stpt.usf.edu 

Kellie Dixon 

Mote Marine Laboratory 

1600 Ken Thompson Parkway

Sarasota, FL 34210

Phone: 941-388-4441 

E-mail: lkdixon@mote.org 

William Drennan 

University of Miami, RSMAS

4600 Rickenbacker Causeway

Miami, FL 33149

Phone: 305-421-4798 

E-mail: wdrennan@rsmas.miami.edu 

Eurico J. D’Sa 

Louisiana State University 

Coastal Studies Institute

Dept. of Oceanography and Coastal Sciences

Baton Rouge, LA 70803

Phone: 225-578-0212 

E-mail: ejdsa@lsu.edu 

Regina A. Easley 

University of South Florida 

College of Marine Science

140 7th Ave. South

St. Petersburg, FL 33701

Phone: 727-278-1470 

E-mail: reasley@marine.usf.edu 
34 Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico

Richard A. Feely 

PMEL/NOAA

7600 Sand Point Way N.E.

Seattle, WA 98115

Phone: 206-526-6214 

E-mail: Richard.A.Feely@noaa.gov 

Sonia C. Gallegos 

Naval Research Laboratory 

Ocean Sciences - Code 7333

Building 1009 A

Stennis Space Center, MS 39529

Phone: 228-688-4867 

Fax: 228-688-4149 

E-mail: gallegos@nrlssc.navy.mil 

Wilford D. Gardner 

Texas A&M University 

3146 TAMU

Department of Oceanography

College Station, TX 77845-3146

Phone: 979-845-3928 

Fax: 979-845-6331 

E-mail: wgardner@ocean.tamu.edu 

Miguel A. Goñi 

Oregon State University

College of Oceanic and Atmospheric Sciences

104 Ocean Admin. Bldg.

Corvallis, OR 97331

Phone: 541-737-0578 

E-mail: mgoni@coas.oregonstate.edu

Elizabeth S. Gordon 

Fitchburg State College 

160 Pearl Street

Fitchburg, MA 01420

Phone: 978-665-3083 

E-mail: egordon3@fsc.edu 

Peter Griffith 

NASA GSFC / SSAI Code 614.4

Greenbelt, MD 20771

Phone: 301-614-6610 

E-mail: peter.c.griffith@nasa.gov 

Burke Hales 

Oregon State University

104 Ocean Admin. Bldg.

Corvallis, OR 97331

Phone: 541-737-8121 

E-mail: bhales@coas.oregonstate.edu 

Emily R. Hall 

Mote Marine Laboratory 

1600 Ken Thompson Parkway

Sarasota, FL 34236

Phone: 941-388-4441 x327 

E-mail: emily8@mote.org 

Dennis A. Hansell 

University of Miami 

4600 Rickenbacker Causeway

RSMAS/MAC

Miami, FL 33149

Phone: 305-421-4078 

E-mail: dhansell@rsmas.miami.edu 

Ruoying He 

North Carolina State University 

2800 Faucette Drive

Raleigh, NC 27695

Phone: 919-513-0249 

E-mail: rhe@ncsu.edu 

Iuri Herzfeld 

University of Hawaii 

1000 Pope Road

Honolulu, HI 96822

Phone: 727-692-1473 

E-mail: herzfeld@soest.hawaii.edu 

Gary L. Hitchcock 

University of Miami/MBF 

4600 Rickenbacker Causeway

Miami, FL 33149

Phone: 305-421-4926 

Fax: 305-421-4600 

E-mail: g.hitchcock@miami.edu 

David T. Ho 

Lamont-Doherty Earth Observatory

61 Route 9W

Palisades, NY 10964

Phone: 845-365-8706 

E-mail: david@ldeo.columbia.edu 

Charles W. Holmes 

U.S. Geological Survey

9103 64th Ave. East

Bradenton, FL 34202

Phone: 941-753-0050 

E-mail: cholmes@usgs.gov 

Markus Huettel 

Florida State University 

117 N Woodward Ave.

Tallahassee, FL 32306-4320

Phone: 850-645-1394 

Fax: 850-644-2581

E-mail: mhuettel@ocean.fsu.edu

David E. John 

University of South Florida 

140 7th Ave. South

St. Petersburg, FL 33701

Phone: 727-553-1647 

E-mail: djohn@marine.usf.edu 
Participant List 35

Paul O. Knorr 

U.S. Geological Survey 

600 4th St. South

St. Petersburg, FL 33701

Phone: 727-803-8747 

Fax: 727-803-2032 

E-mail: pknorr@usgs.gov 

Charles W. Kovach

Florida Department of Environmental Protection 

13051 North Telecom Parkway

Temple Terrace, FL 33637-0926

Phone: 813-632-7600 x329

Fax: 813-632-7663 

E-mail: charles.kovach@dep.state.fl.us

Mingliang Liu 

Auburn University 

3301 Forestry and Wildlife Sciences Building

Auburn University

Auburn, AL 36830

Phone: 334-844-8061 

E-mail: liuming@auburn.edu

Sherwood Liu 

College of Marine Science

University of South Florida 

140 7th Ave. South

St. Petersburg, FL 33701

Phone: 727-553-3922 

E-mail: liu@marine.usf.edu 

Steven E. Lohrenz 

The University of Southern Mississippi 

1020 Balch Blvd.

Stennis Space Center, MS 39529

Phone: 228-688-3177 

E-mail: Steven.Lohrenz@usm.edu 

Laura Lorenzoni 

University of South Florida 

140 7th Ave. South, KRC 3117

St. Petersburg, FL 33701

Phone: 727-553-3987 

Fax: 727-553-1103 

E-mail: laural@marine.usf.edu 

Alexis Lugo-Fernandez 

MMS-Gulf of Mexico 

OCS Physical Sciences Unit (MS 5433)

1201 Elmwood Park Blvd.

New Orleans, LA 70123-2394

Phone: 504-736-2593 

E-mail: alexis.lugo.fernandez@mms.gov 

Lawrence M. Mayer 

University of Maine 

Darling Marine Center 

193 Clarks Cove Rd.

Walpole, ME 04573

Phone: 207-563-3146 

E-mail: LMayer@maine.edu 

Brent A. McKee 

University of North Carolina - Chapel Hill 

UNC Department of Marine Sciences

449 Chapman Hall; Campus Box 3300

Chapel Hill, NC 27599-3300

Phone: 919-843-3604 

E-mail: bmckee@unc.edu 

Ralph N. Mead 

University of North Carolina - Wilmington

Department of Chemistry and Biochemistry 

601 South College Road

Wilmington, NC 28403

Phone: 910-962-2447 

E-mail: meadr@uncw.edu 

Richard Miller 

East Carolina University 

Department of Geological Sciences

101 Graham

Greenville, NC 27858

Phone: 985-285-6708 

E-mail: richard.miller@alumni.duke.edu 

Dong-Ha Min 

The University of Texas at Austin

Marine Science Institute 

750 Channel View Dr.

Port Aransas, TX 78373

Phone: 361-749-6743 

E-mail: dongha@mail.utexas.edu 

Siddhartha Mitra 

East Carolina University 

Department of Geological Sciences

101 Graham

Greenville, NC 27858

Phone: 252-328-6611 

E-mail: mitras@ecu.edu 

Willard S. Moore 

University of South Carolina 

701 Sumter St.

Department of Geological Sciences

Columbia, SC 29208

Phone: 803-777-2262 

Fax: 803-777-6610 

E-mail: moore@geol.sc.edu 

Arturo F. Muhlia 

CIBNOR, S.C. 

Mar Bermejo No 195 

Col. Palo de Santa Rita

La Paz, Baja 

California Sur, México 23090

Phone: +52-612-1238430 

Fax: +52-612-1253625 

E-mail: amuhlia04@cibnor.mx 
36 Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico

Michael C. Murrell 

U.S. Environmental Protection Agency 

Gulf Ecology Division 

1 Sabine Island Drive

Gulf Breeze, FL 32561

Phone: 850-934-2433 

E-mail: murrell.michael@epa.gov 

Raymond G. Najjar 

The Pennsylvania State University 

Department of Meteorology

503 Walker Building

University Park, PA 16802-5013

Phone: 814-863-1586 

E-mail: najjar@meteo.psu.edu 

Karen M. Orcutt 

University of Southern Mississippi 

Department of Marine Science 

1020 Balch Blvd.

Stennis Space Center, MS 39529

Phone: 228-688-3154 

Fax: 228-688-1121 

E-mail: karen.orcutt@usm.edu 

Philip M. Orton 

Lamont-Doherty Earth Observatory

61 Route 9W

Palisades, NY 10964

Phone: 845 365-8317 

E-mail: orton@ldeo.columbia.edu 

Christopher Osburn 

Naval Research Laboratory Code 6114

4555 Overlook Ave. SW

Washington, DC 20375

Phone: 703-899-4828 

E-mail: christopher.osburn@nrl.navy.mil 

John H. Paul 

University of South Florida 

140 7th Ave. South

St Petersburg, FL 33701

Phone: 727-553-1168 

E-mail: jpaul@marine.usf.edu 

Tsung-Hung Peng 

NOAA/AOML 

4301 Rickenbacker Causeway

Miami, FL 33149

Phone: 305-361-4399 

E-mail: tsung-hung.peng@noaa.gov 

Charles H. Perry 

USDA Forest Service 

Northern Research Station

1992 Folwell Ave.

St. Paul, MN 55108

Phone: 651-649-5191 

Fax: 651-649-5140 

E-mail: charleshperry@fs.fed.us 

Rodney T. Powell 

LUMCON 

8124 Highway 56

Chauvin, LA 70344

Phone: 985-851-2825 

Fax: 985-851-2874 

E-mail: rpowell@lumcon.edu 

Ellen Raabe 

U.S. Geological Survey

600 4th St. South

St. Petersburg, FL 33701

Phone: 727-803-8747 x3039 

E-mail: eraabe@usgs.gov

Peter Raymond 

Yale University 

21 Sachem St.

New Haven, CT 06511

Phone: 203-432-0817 

E-mail: peter.raymond@yale.edu 

Mary Jo Richardson 

Texas A&M University 

3146 TAMU

Department of Oceanography

College Station, TX 77843

Phone: 979-845-7966 

E-mail: mrichardson@ocean.tamu.edu 

Joseph E. Salisbury 

University of New Hampshire

Ocean Processes Analysis Lab 

142 Morse Hall

Durham, NH 03824

Phone: 603-862-0849 

E-mail: joe.salisbury@unh.edu 

Robert H. Stav

University of North Carolina - Greensboro 

Eberhart 312

321 McIver St.

Greensboro, NC 27412

Phone: 336-334-4979 

E-mail: stavnr@uncg.edu 

Ajit Subramaniam 

National Science Foundation 

4201 Wilson Blvd.

Arlington, VA 22230

Phone: 703-292-7592 

E-mail: asubrama@nsf.gov 

Eric Sundquist 

U.S. Geological Survey 

384 Woods Hole Rd.

Woods Hole, MA 02543

Phone: 508-457-2397 

E-mail: esundqui@usgs.gov
Participant List 37

Kathy A. Tedesco 

U.S. Geological Survey 

600 4th St. South

St. Petersburg, FL 33701

Phone: 727-803-8747 x3121

E-mail: ktedesco@usgs.gov 

Hanqin Tian 

Auburn University 

School of Forestry and Wildlife Sciences

602 Duncan Drive

Auburn, AL 36849

Phone: 334-844-1059 

E-mail: tianhan@auburn.edu 

R. Eugene Turner 

Louisiana State University 

Coastal Ecology Inst. SCE

Baton Rouge, LA 70803

Phone: 225-578-6454 

Fax: 225-578-6326 

E-mail: euturne@lsu.edu 

Baris M. Uz 

NOAA Climate Program Office 

1315 East West Highway

Silver Spring, MD 20910

Phone: 301-724-1247 

E-mail: baris.uz@noaa.gov

Zhaohui Wang 

University of South Florida

College of Marine Science 

140 7th Ave. South

St. Petersburg, FL 33701

Phone: 727-553-3922 

E-mail: awang@marine.usf.edu 

Rik Wanninkhof 

NOAA/AOML 

4301 Rickenbacker Causeway 

Miami, FL 33149

Phone: 305-361-4379 

E-mail: rik.wanninkhof@noaa.gov 

Lucian Wielopolski 

Brookhaven National Laboratory 

Environmental Sciences Department

Bldg. 490D

Upton, NY 11973

Phone: 631-344-3656 

E-mail: lwielo@bnl.gov 

Jerry Wiggert 

The University of Southern Mississippi

Department of Marine Sciences 

1020 Balch Blvd.

Stennis Space Center, MS 39529

Phone: 228-688-3491 

Fax: 228-688-1121 

E-mail: jerry.wiggert@usm.edu 

Andrew R. Zimmerman

University of Florida 

Department of Geological Sciences

241 Williamson Hall

Gainesville, FL 32611

Phone: 352-392-0070 

E-mail: azimmer@ufl.edu
38 Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico

References Cited

Allison, M., Bianchi, T.S., McKee, B.A., and Sampere, T.P., 

2007, Carbon burial on the river-dominated continental 

shelves: Impact of historical changes in sediment loading 

adjacent to the Mississippi River: Journal of Geophysical 

Resarch, v. 34, p. 1-6.

Álvarez-Góngora, C., and Herrera-Silveira, J.A., 2006, Variations of phytoplankton community structure related to water 

quality trends in a tropical karstic coastal zone: Marine 

Pollution Bulletin, v. 52, no. 1, p. 48-60.

Arcos-Espinosa, G., Medina-Santamaría, R., Méndez-Incera, 

F.J., and Jiménez-Hernández, S.B., 2008, Study of the salt 

wedge of the Panuco River, Mexico: Ingenieria Hidraulica 

en Mexico, v. 23, no. 3, p. 77-88.

Armstrong, R.A., Lee, C., Hedges, J.I., Honjo, S., and 

Wakeham, S.G., 2001, A new, mechanistic model for 

organic carbon fluxes in the ocean based on the quantitative association of POC with ballast minerals: Deep-Sea 

Research Part II, v. 49, no. 1-3, p. 219-236.

Arrigo, K., 2005, Marine microorganisms and global nutrient 

cycles: Nature, v. 437, no. 15, p. 349-355.

Avila, L.A., 2008, Highlights of the 2007 Atlantic and eastern 

North Pacific hurricane seasons -- A year of extremes in 

the Atlantic basin, AMS 28th Conference on Hurricanes 

and Tropical Meteorology: Miami, FL, American Meteorological Society, p. 3B.1-4. http://ams.confex.com/ams/

pdfpapers/137377.pdf

Azetsu-Scott, K., and Passow, U., 2004, Ascending marine 

particles: Significance of transparent exopolymer particles 

(TEP) in the upper ocean: Limnology and Oceanography, 

v. 49, no. 3, p. 741-748

Baldocchi, D., 2008, ‘Breathing’ of the terrestrial biosphere: 

Lessons learned from a global network of carbon dioxide 

flux measurement systems: Australian Journal of Botany, 

v. 56, no. 1, p. 1-26.

Baschek, B., Farmer, D.M., and Garrett, C., 2006, Tidal fronts 

and their role in air-sea gas exchange: Journal of Marine 

Research, v. 64, no. 4, p. 483-515.

Beeman, P., 2008, Floods may yield record Gulf 

‘dead zone’, Des Moines Register: Des Moines. 

http://www.desmoinesregister.com/apps/pbcs.dll/

article?AID=/20080626/NEWS/806260395

Benke, A.C., and Cushing, C.E., 2005, Rivers of North 

America: Amsterdam, Academic Press, 1144 p.

Benway, H.M., and Doney, S.C., 2007, Advancing the integration of marine ecosystem dynamics and biogeochemistry: Second Annual Ocean Carbon and Biogeochemistry 

Summer Workshop: Eos, Transactions, v. 88, no. 47, doi: 

10.1029/2007EO470007.

Bianchi, T.S., Filley, T., Dria, K., and Hatcher, P., 2004, 

Temporal variability in sources of dissolved organic carbon 

in the lower Mississippi River: Geochimica et Cosmochimica Acta, v. 68, p. 959-967.

Bianchi, T.S., Galler, J., and Allison, M.A., 2007, Hydrodynamic sorting and transport of terrestrially derived organic 

carbon in sediments of the Mississippi and Atchafalaya 

Rivers: Estuarine, Coastal and Shelf Science, v. 73, p. 

211-222.

Bianchi, T.S., Lambert, C.D., Santschi, P.H., and Guo, L., 

1997, Sources and transport of land-derived particulate 

and dissolved organic matter in the Gulf of Mexico (Texas 

shelf/slope): The use of lignin-phenols and loliolides as 

biomarkers: Organic Geochemistry, v. 27, p. 65-78.

Bianchi, T.S., Mitra, S., and McKee, M., 2002, Sources of 

terrestrially-derived carbon in the Lower Mississippi River 

and Louisiana shelf: Implications for differential sedimentation and transport at the coastal margin: Marine Chemistry, 

v. 77, no. 211-223.

Boehme, S.E., Sabine, C.L., and Reimers, C.E., 1998, CO2

fluxes from a coastal transect: A time-series approach: 

Marine Chemistry, v. 63, no. 1-2, p. 49-67.

Boesch, D.F., 1999, The role of the Mississippi River in 

Gulf of Mexico hypoxia: Oversimplifications and confusion: Document submitted to the Gulf of Mexico Hypoxia 

Working Group, National Oceanic and Atmospheric Administration, 18 p.

Boesch, D.F., 2003, Continental shelf hypoxia: Some compelling answers: Gulf of Mexico Science, v. 21, p. 143-145.

Boning, C., 2008, Florida’s rivers: Sarasota, Pineapple Press, 

240 p.

Bortone, S.A., 2006, Recommendations on establishing a 

research strategy in the Gulf of Mexico to assess the effects 

of hurricanes on coastal ecosystems: Estuaries and Coasts, 

v. 29, no. 6, p. 1062-1066.

Boyer, E., 2008, Modeling watershed nutrient fluxes [presentation], in Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf 

of Mexico, St. Petersburg, FL, May 6-8, 2008. Accessed at 

http://www.whoi.edu/cms/files/boyer_ocb_large_36743.pdf

Brown, A.V., Brown, K.B., Jackson, D.C., and Pierson, W.K., 

eds., 2005, Lower Mississippi River and its tributaries, 

in Benke, A.C., and Cushing, C.E., eds., Rivers of North 

America: Amsterdam, Academic Press, p. 231-281.
References Cited 39

Burnett, W.C., Cowart, J.B., and Deetae, S., 1990, Radium 

in the Suwannee River and Estuary: Spring and river input 

to the Gulf of Mexico: Biogeochemistry, v. 10, no. 3, 

p. 237-255.

Cable, J.E., Burnett, W.C., Chanton, J.P., and Weatherly, G.L., 

1996, Estimating groundwater discharge into the northeastern Gulf of Mexico using radon-222: Earth and Planetary Science Letters, v. 144, p. 591-604.

Cai, W.-J., 2003, Riverine inorganic carbon flux and rate 

of biological uptake in the Mississippi River plume: 

Geophysical Research Letters, v. 30, no. 2, 1032, 

doi:10.1029/2002GL016312.

Cai, W.-J., and Lohrenz, S.E., in press, Carbon, nitrogen, 

and phosphorus fluxes from the Mississippi River and the 

transformation and fate of biological elements in the river 

plume and the adjacent margin, in Liu, K.K., Atkinson, L., 

Quinones, R., and Talaue-McManus, L., eds., Carbon and 

nutrient fluxes in continental margins: a global synthesis: 

New York, Springer-Verlag.

Cai, W.-J., Gao, X., Chen, F., Huang, W.-J., Wang, Y., and 

Lohrenz, S.E., 2008, The dynamics of CO2 in the Mississippi River plume and Northern Gulf of Mexico [presentation], in Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf 

of Mexico, St. Petersburg, FL, May 6-8, 2008. Accessed at 

http://www.whoi.edu/sbl/liteSite.do?litesiteid=23613

Cai, W.-J., Wang, Y., Krest, J., and Moore, W.S., 2003, 

The geochemistry of dissolved inorganic carbon in a surficial groundwater aquifer in North Inlet, South Carolina, 

and the carbon fluxes to the coastal ocean: Geochimica et 

Cosmochimica Acta, v. 67, no. 4, p. 631-639.

Chavez, F.P., Takahashi, T., Cai, W.J., Friederich, G., Hales, B., 

Wanninkhof, R., and Feely, R.A., 2007, Coastal oceans, in

King, A.W., Dilling, L., Zimmerman, G.P., Fairman, D.M., 

Houghton, R.A., Marland, G., Rose, A.Z., and Wilbanks, 

T.J., eds., The First State of the Carbon Cycle Report 

(SOCCR): The North American Carbon Budget and Implications for the Global Carbon Cycle: Asheville, NC, USA, 

National Oceanic and Atmospheric Administration, National 

Climatic Data Center, p. 156-166.

Chen, N., Bianchi, T.S., McKee, B.A., and Bland, J.M., 2001, 

Historical trends of hypoxia on the Louisiana shelf: Application of pigments as biomarkers: Organic Geochemistry, 

v. 32, p. 543-562.

Childers, D.S., Davis, S., Twilley, R., and Rivera-Monroy, 

V., 1998, Estuary-watershed coupling around the Gulf of 

Mexico, in Bianchi, T., Pennock, J., and Twilley, R., eds., 

Biogeochemistry of Gulf of Mexico estuaries: New York, 

Wiley, p. 211-235.

Corbett, D.R., Dillon, K., Burnett, W., and Chanton, J., 2000, 

Estimating the groundwater contribution into Florida Bay 

via natural tracers 222Rn and CH4: Limnology and Oceanography, v. 45, no. 7, p. 1546-1557.

Dagg, M., Benner, R., Lohrenz, S., and Lawrence, D., 2004, 

Transformation of dissolved and particulate materials 

on continental shelves influenced by large rivers: Plume 

processes: Continental Shelf Research, v. 24, no. 7-8, 

p. 833-858.

Dagg, M., Green, E., McKee, B., and Ortner, P., 1996, Biological removal of fine-grained lithogenic particles from a large 

river plume: Journal of Marine Research, v. 54, no. 1, p. 

149-160.

Dagg, M.J., Ammerman, J.W., Amon, R.M.W., Gardner, W.S., 

Green, R.E., and Lohrenz, S.E., 2007, A review of water 

column processes influencing hypoxia in the northern Gulf 

of Mexico: Estuaries and Coasts, v. 30, p. 735-752.

Dagg, M.J., Bianchi, T., McKee, B., and Powell, R., 2008, 

Fates of dissolved and particulate materials from the Mississippi River immediately after discharge into the northern 

Gulf of Mexico, USA, during a period of low wind stress: 

Continental Shelf Research, v. 28, no. 12, p. 1443-1450.

Dahm, C., Edwards, R., and Gelwick, F., 2005, Gulf Coast 

rivers of the southwestern United States, in Benke, 

A.C., and Cushing, C.E., eds., Rivers of North America: 

Amsterdam, Academic Press.

Darrow, B.P., Walsh, J.J., Vargo, G.A., Masserini, R.T., 

Fanning, K.A., and Zhang, J.Z., 2003, A simulation study of 

the growth of benthic microalgae following the decline of a 

surface phytoplankton bloom: Continental Shelf Research, 

v. 23, no. 14-15, p. 1265-1283.

DeGrandpre, M.D., Olbu, G.J., Beatty, C.M., and Hammar, 

T.R., 2002, Air-sea CO2 fluxes on the US Middle Atlantic 

Bight: Deep-Sea Research Part II, v. 49, no. 20, p. 4355-

4367.

Del Castillo, C., Gilbes, F., Coble, P.G., and Muller-Karger, 

F.E., 2000, On the dispersal of riverine colored dissolved 

organic matter over the West Florida Shelf: Limnology and 

Oceanography, v. 45, no. 6, p. 1425-1432.

DeLong, M., 2005, Upper Mississippi River basin, in Benke, 

A.C., and Cushing, C.E., eds., Rivers of North America: 

Amsterdam, Academic Press, p. 327-374.

Denman, K., and Peña, M., 1999, A coupled 1-D biological/

physical model of the northeast subarctic Pacific Ocean with 

iron limitation: Deep-Sea Research Part II, v. 46, no. 11-12, 

p. 2877-2908.

Dittmar, T., 2007, Non-riverine pathways of terrigenous 

carbon to the ocean, Eos, Transactions, v. 88, no. 52, 

abstract #B13G-08.
40 Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico

Doney, S.C., and Glover, D.M., 2005, Recent advances in the 

ocean carbon system: Eos, Transactions, v. 86, p. 399-400.

Doney, S.C., and Hood, M., 2002, A global ocean carbon 

observation system, a background report: UNESCO Intergovernmental Oceanographic Commission IOC/INF-1173, 

Global Ocean Observing System Report No. 118, 55 p.

Donner, S.D., and Kucharik, C.J., 2008, Corn-based ethanol 

production compromises goal of reducing nitrogen export 

by the Mississippi River: Proceedings of the National 

Academy of Sciences, v. 105, no. 11, p. 4513-4518.

Douglas, B.C., 2005, Gulf of Mexico and Atlantic coast sea 

level change: Geophysical Monograph, v. 161, p. 111-121.

Escobar-Briones, E.G., and Soto, L.A., 1997, Continental shelf 

benthic biomass in the western Gulf of Mexico: Continental 

Shelf Research, v. 17, no. 6, p. 585-604.

Fabry, V., Seibel, B., Feely, R., and Orr, J., 2008, Impacts 

of ocean acidification on marine fauna and ecosystem 

processes: ICES Journal of Marine Science, v. 65, no. 3, 

p. 414-432.

Fennel, K., Wilkin, J., Levin, J., Moisan, J., O’Reilly, 

J., and Haidvogel, D., 2006, Nitrogen cycling in the 

Middle Atlantic Bight: Results from a three-dimensional 

model and implications for the North Atlantic nitrogen 

budget: Global Biogeochemical Cycles, v. 20, no. 3, 

doi:10.1029/2005GB002456.

Flick, R.E., Murray, J.F., and Ewing, L.C., 2003, Trends in 

United States tidal datum statistics and tide range: Journal 

of Waterway, Port, Coastal and Ocean Engineering, v. 129, 

no. 4, p. 155-164.

Frankignoulle, M., and Borges, A.V., 2001, European continental shelf as a significant sink for atmospheric carbon 

dioxide: Global Biogeochemical Cycles, v. 15, no. 3, 

p. 569-576.

Frew, N.M., Goldman, J.C., Dennett, M.R., and Johnson, 

A.S., 1990, Impact of phytoplankton-generated surfactants 

on air-sea gas exchange: Journal of Geophysical Research, 

v. 95, no. C3, p. 3337-3352.

Gagliano, S.M., Meyer-Arendt, K.J., and Wicker, K.M., 1981, 

Land loss in the Mississippi River deltaic plain: Transactions of Gulf Coast Association of Geological Societies, 

v. 31, p. 295-300.

Galler, J.J., Bianchi, T.S., Allison, M.A., Campanella, R., 

and Wysocki, L.A., 2003, Biogeochemical implications of 

levee confinement in the lowermost Mississippi River: Eos, 

Transactions, v. 84, no. 44, p. 475-476.

Gardner, W.S., Cotner, J.B., Eadie, B.J., Cavaletto, J.F., 

Benner, R., and Chin-Leo, G., 1994, Mineralization of 

organic material and bacterial dynamics in Mississippi 

River plume water: Estuaries and Coasts, v. 17, no. 4, 

p. 816-828.

Goñi, M.A., Ruttenberg, K.C., and Eglinton, T.I., 1997, 

Sources and contribution of terrigenous organic carbon to 

surface sediments in the Gulf of Mexico: Nature, v. 389, 

no. 6648, p. 275-278.

Goñi, M.A., Ruttenberg, K.C., and Eglinton, T.I., 1998, 

A reassessment of the sources and importance of landderived organic matter in surface sediments from the Gulf 

of Mexico: Geochimica et Cosmochimica Acta, v. 62, 

p. 3055-3075.

Gordon, E.S., and Goñi, M.A., 2003, Sources and distribution 

of terrigenous organic matter delivered by the Atchafalaya 

River to sediments in the northern Gulf of Mexico: Geochimica et Cosmochimica Acta, v. 67, p. 2359-2375.

Gower, J., Hu, C., Borstad, G., and King, S., 2006, Ocean 

color satellites show extensive lines of floating Sargassum

in the Gulf of Mexico: IEEE Transactions on Geoscience 

and Remote Sensing, v. 44, no. 12, p. 3619-3625.

Gower, J., and King, S., 2008, Satellite images show the 

movement of floating Sargassum in the Gulf of Mexico 

and Atlantic Ocean: Nature Proceedings, v. 1894.1, no. 15. 

http://precedings.nature.com/documents/1894/version/1/

html

Hales, B., Cai, W.-J., Mitchell, G., Sabine, C., and Schofield, O., 

2008, North American continental margins: A synthesis and 

planning workshop: U.S. Carbon Cycle Science Program, 

110 p.

Hallock, P., 2005, Global change and modern coral reefs: New 

opportunities to understand shallow-water carbonate depositional processes: Sedimentary Geology, v. 175, no. 1-4, 

p. 19-33.

He, R., 2008, Physical oceanography and circulation of 

the Gulf of Mexico [presentation], in Ocean Carbon and 

Biogeochemistry Scoping Workshop on Terrestrial and 

Coastal Carbon Fluxes in the Gulf of Mexico, St. Petersburg, FL, May 6-8, 2008.

He, R., and Weisberg, R.H., 2003, A Loop Current intrusion 

case study on the West Florida Shelf: Journal of Physical 

Oceanography, v. 33, no. 2, p. 465-477.

Hedges, J.I., and Parker, P.L., 1976, Land-derived organic 

matter in surface sediments from the Gulf of Mexico: 

Geochimica et Cosmochimica Acta, v. 40, no. 9, 

p. 1019-1029.
References Cited 41

Hernández-Arana, H.A., Rowden, A.A., Attrill, M.J., 

Warwick, R.M., and Gold-Bouchot, G., 2003, Large-scale 

environmental influences on the benthic macroinfauna of 

the southern Gulf of Mexico: Estuarine, Coastal and Shelf 

Science, v. 58, no. 4, p. 825-841.

Hoegh-Guldberg, O., Mumby, P.J., Hooten, A.J., Steneck, 

R.S., Greenfield, P., Gomez, E., Harvell, C.D., Sale, P.F., 

Edwards, A.J., and Caldeira, K., 2007, Coral reefs under 

rapid climate change and ocean acidification: Science, 

v. 318, no. 5857, p. 1737-1742.

Hofmann, E., and Mannino, A., 2007, Integrated study of the 

carbon budget of the continental shelf of the Mid-Atlantic 

and South Atlantic Bights: Geophysical Research Abstracts, 

v. 9. http://www.cosis.net/abstracts/EGU2007/04439/

EGU2007-J-04439.pdf

Hu, C., Muller-Karger, F.E., and Swarzenski, P.W., 2006, 

Hurricanes, submarine groundwater discharge, and Florida’s 

red tides: Geophysical Research Letters, v. 33, L11601, 

doi:10.1029/2005GL025449.

Hudson, P., Hendrickson, D., Benke, A., Varela-Romero, A., 

Rodiles-Hernandez, R., and Minckley, W.L., 2005, Rivers 

of Mexico, in Benke, A.C., and Cushing, C.E., eds., Rivers 

of North America: Amsterdam, Academic Press, p. 1031-

1084.

IOC, 1997, Workshop report on the transports and linkages of 

the Intra-Americas Sea (IAS): Intergovernmental Oceanographic Commission Workshop Report No. 162, 58 p. 

http://unesdoc.unesco.org/images/0012/001283/128357e.

pdf

IPCC, 2007, Climate change 2007: Mitigation: Contribution of 

Working Group III to the Fourth Assessment Report of the 

Intergovernmental Panel on Climate Change: Cambridge, 

Cambridge University Press, 841 p.

Jahnke, R.A., in press, A global synthesis, in Liu, K.K., 

Atkinson, L., Quinones, R., and Talaue-McManus, L., eds., 

Carbon and nutrient fluxes in continental margins: A global 

synthesis: New York, Springer-Verlag.

Kaiser, M.J., and Pulsipher, A.G., 2007, The impact of weather 

and ocean forecasting on hydrocarbon production and pollution management in the Gulf of Mexico: Energy Policy, 

v. 35, no. 2, p. 966-983.

Keller, M., Schimel, D.S., Hargrove, W.W., and Hoffman, 

F.M., 2008, A continental strategy for the National Ecological Observatory Network: Frontiers in Ecology and the 

Environment, v. 6, no. 5, p. 282-284.

Kempe, S., and Pegler, K., 1991, Sinks and sources of CO2

in coastal seas: The North Sea: Tellus B. v. 43, no. 2, 

p. 224-235.

Kennish, M.J., 2002, Environmental threats and environmental 

future of estuaries: Environmental Conservation, v. 29, 

no. 1, p. 78-107.

Kildow, J., 2006, Phase I. Florida’s ocean and coastal 

economies report: National Ocean Economics Program, 

Florida Oceans and Coastal Council, 117 p. http://www.

floridaoceanscouncil.org/meetings/files/Florida_Ocean_&_

Coastal_Eco.pdf

Kildow, J., 2008, Phase II. Florida’s ocean and coastal 

economies report: National Ocean Economics Program, 

Florida Oceans and Coastal Council, 205 p. http://www.

floridaoceanscouncil.org/meetings/files/2008/06-17/

Florida_Phase_II_Report_2008.pdf

King, A.W., Dilling, L., Zimmerman, G.P., Fairman, D.M., 

Houghton, R.A., Marland, G., Rose, A.Z., and Wilbanks, 

T.J., eds., 2007, The first state of the carbon cycle report 

(SOCCR): The North American carbon budget and implications for the global carbon cycle: National Oceanic 

and Atmospheric Administration, National Climatic Data 

Center, 242 p.

Kishi, M.J., Kashiwai, M., Ware, D.M., Megrey, B.A., 

Eslinger, D.L., Werner, F.E., Noguchi-Aita, M., Azumaya, 

T., Fujii, M., Hashimoto, S., Huang, D., Iizumi, H., Ishida, 

Y., Kang, S., Kantakov, G.A., Kim, H.-C., Komatsu, K., 

Navrotsky, V.V., Smith, S.L., Tadokoro, K., Tsuda, A., Yamamura, O., Yamanaka, Y., Yokouchi, K., Yoshie, N., Zhang, J., 

Zuenko, Y.I., and Zvalinsky, V.I., 2007, NEMURO--a lower 

trophic level model for the North Pacific marine ecosystem: 

Ecological Modelling, v. 202, no. 1-2, p. 12-25.

Kleypas, J.A., Feely, R.A., Fabry, V.J., Langdon, C., Sabine, 

C.L., and Robbins, L.L., 2006, Impacts of ocean acidification on coral reefs and other marine calcifiers: A guide for 

future research: A report of a workshop held 18-20 April 

2005, St. Petersburg, FL, sponsored by NSF, NOAA, and 

the U.S. Geological Survey, 88 p.

Ko, D.S., Preller, R.H., and Martin, P.J., 2003, An experimental real-time Intra-Americas Sea ocean nowcast/forecast 

system for coastal prediction, in 32nd Conference on Broadcast Meteorology/31st Conference on Radar Meteorology/

Fifth Conference on Coastal Atmospheric and Oceanic 

Prediction and Processes, Seattle, WA, p. 5.2, http://ams.

confex.com/ams/pdfpapers/64664.pdf

Kortzinger, A., 2003, A significant CO2 sink in the tropical Atlantic Ocean associated with the Amazon River 

plume: Geophysical Research Letters, v. 30, no. 24, 

doi:10.1029/2003GL018841.

Krest, J.M., Moore, W.S., and Rama, 1999, 226Ra and 228Ra in 

the mixing zones of the Mississippi and Atchafalaya Rivers: 

Indicators of groundwater input: Marine Chemistry v. 64, 

p. 129-152.
42 Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico

Kvenvolden, K.A., and Lorenson, T.D., 2007, A global inventory of natural gas hydrate occurrence: U.S. Geological 

Survey. http://walrus.wr.usgs.gov/globalhydrate/poster.pdf

Lee, C., Wakeham, S., and Arnosti, C., 2004, Particulate 

organic matter in the sea: The composition conundrum: 

AMBIO: A Journal of the Human Environment, v. 33, no. 8, 

p. 565-575.

Lefèvre, N., Aiken, J., Rutllant, J., Daneri, G., Lavender, S., 

and Smyth, T., 2002, Observations of pCO2 in the coastal 

upwelling off Chile: Spatial and temporal extrapolation 

using satellite data: Journal of Geophysical ResearchOceans, v. 107, no. C6, p. 8.1-8.15.

Lenes, J., Darrow, B., Walsh, J., Prospero, J., He, R., Weisberg, R., Vargo, G., and Heil, C., 2008, Saharan dust and 

phosphatic fidelity: A three-dimensional biogeochemical 

model of Trichodesmium as a nutrient source for red tides 

on the West Florida Shelf: Continental Shelf Research, 

v. 28, no. 9, p. 1091-1115.

Lenes, J.M., Darrow, B.P., Cattrall, C., Heil, C.A., Callahan, 

M., Vargo, G.A., Byrne, R.H., Prospero, J.M., Bates, D.E., 

Fanning, K.A., and Walsh, J.J., 2001, Iron fertilization and 

the Trichodesmium response on the West Florida Shelf: 

Limnology and Oceanography, v. 46, no. 6, p. 1261-1277.

Liu, K.K., Iseki, K., and Chao, S.Y., 2000, Continental margin 

carbon fluxes, in Hanson, R.B., Field, J.G., and Ducklow, 

H.W., eds., The changing ocean carbon cycle: A midterm 

synthesis of the Joint Global Ocean Flux Study: Cambridge, 

Cambridge University Press, p. 187-239.

Lohrenz, S.E., 2008, Gulf of Mexico carbon cycling [presentation], in Ocean Carbon and Biogeochemistry Scoping 

Workshop on Terrestrial and Coastal Carbon Fluxes in the 

Gulf of Mexico, St. Petersburg, FL, May 6-8, 2008.

Lohrenz, S.E., and Cai, W.-J., 2006, Satellite ocean color 

assessment of air-sea fluxes of CO2 in a river-dominated 

coastal margin: Geophysical Research Letters, v. 33, no. 1, 

doi:10.1029/2005GL023942.

Lohrenz, S.E., and Cai, W.-J., 2008, North America’s Gulf of 

Mexico coast: North American continental margins report.

Lohrenz, S.E., Fahnenstiel, G.L., Redalje, D.G., Lang, G.A., 

Chen, X., Dagg, M.J., 1997, Variations in primary production of northern Gulf of Mexico continental shelf waters 

linked to nutrient inputs from the Mississippi River: Marine 

Ecology Progress Series, v. 155, p. 45-54.

López-Méndez, V., Zavala-Hidalgo, J., and Romero-Centeno, 

R., 2008, Analysis of the extreme flooding during October 

2007 in Tabasco, Mexico using the WRF model: 9th Annual 

WRF (Weather Research & Forecasting Model) Users’ 

Workshop: Boulder, CO, 23-27 June 2008, National Center 

for Atmospheric Research.

Lueker, T.J., Walker, S.J., Vollmer, M.K., Keeling, R.F., 

Nevison, C.D., and Weiss, R.F., 2003, Coastal upwelling 

air-sea fluxes revealed in atmospheric observations of O2/

N2, CO2 and N2O: Geophysical Research Letters, v. 30, 

no. 6, 1292, doi:10.1029/2002GL016615.

Mackenzie, F.T., Lerman, A., and Ver, L.M.B., 1998, Role of 

the continental margin in the global carbon balance during 

the past three centuries: Geology, v. 26, no. 5, p. 423-426.

Maloney, E.D., and Hartmann, D.L., 2000, Modulation of 

hurricane activity in the Gulf of Mexico by the MaddenJulian Oscillation: Science, v. 287, no. 5460, p. 2002-2004.

Marmorino, G.O., and Trump, C.L., 1996, High-resolution 

measurements made across a tidal intrusion front: Journal of 

Geophysical Research, v. 101, p. 25661-25674.

McGillis, W.R., Edson, J.B., Hare, J.E., and Fairall, C.W., 

2001a, Direct covariance air-sea CO2 fluxes: Journal of 

Geophysical Research, v. 106, no. C8, p. 16729-16746.

McGillis, W.R., Edson, J.B., Ware, J.D., Dacey, J.W.H., Hare, 

J.E., Fairall, C.W., and Wanninkhof, R., 2001b, Carbon 

dioxide flux techniques performed during GasEx-98: 

Marine Chemistry, v. 75, no. 4, p. 267-280.

McKee, B., 2003, RIOMar: The transport, transformation, and 

fate of carbon in river-dominated ocean margins: A report of 

the RioMAR community workshop, Tulane University, 8 p.

McKee, B.A., Aller, R.C., Allison, M.A., Bianchi, T.S., 

and Kineke, G.C., 2004, Transport and transformation of 

dissolved and particulate materials on continental margins 

influenced by major rivers: Benthic boundary layer and 

seabed processes: Continental Shelf Research, v. 24, 

p. 899-926.

McKee, B.A., and Baskaran, M., 1999, Sedimentary processes 

of Gulf of Mexico estuaries, in Bianchi, T., Pennock, J., 

and Twilley, R., eds., Biogeochemistry of Gulf of Mexico 

estuaries: New York, Wiley, p. 63-85.

Merino, M., 1997, Upwelling on the Yucatan Shelf: Hydrographic evidence: Journal of Marine Systems, v. 13, no. 1-4, 

p. 101-121.

Milkov, A.V., and Sassen, R., 2000, Thickness of the gas 

hydrate stability zone, Gulf of Mexico continental slope: 

Marine and Petroleum Geology, v. 17, no. 9, p. 981-991.

Mitsch, W.J., Day, J.W., Jr., Gilliam, J.W., Groffman, P.M., 

Hey, D.L., Randall, G.W., and Wang, N., 2001, Reducing 

nitrogen loading to the Gulf of Mexico from the Mississippi 

River Basin: Strategies to counter a persistent ecological 

problem: BioScience, v. 51, no. 5, p. 373-388.
References Cited 43

Monahan, E.C., and Spillane, M.C., 1984, The role of oceanic 

whitecaps in air-sea gas exchange, in Brutsaert, W., and 

Jirka, G.H., eds., Gas transfer at water surfaces: Hingham, 

MA, D. Reidal, p. 495-503.

Morel, F., and Hering, J., 1993, Principles and applications of 

aquatic chemistry: New York, Wiley, 588 p.

Morse, J.W., Andersson, A.J., and Mackenzie, F.T., 2006, 

Initial responses of carbonate-rich shelf sediments to rising 

atmospheric pCO2 and “ocean acidification”: Role of high 

Mg-calcites: Geochimica et Cosmochimica Acta, v. 70, 

no. 23, p. 5814-5830.

Muhlia Melo, A., 2008, Programa Mexicano del C (PMC): 

Mexican Carbon Program [presentation], in Ocean Carbon 

and Biogeochemistry Scoping Workshop on Terrestrial and 

Coastal Carbon Fluxes in the Gulf of Mexico, St. Petersburg, FL, May 6-8, 2008.

Najjar, R., 2008, Eastern U.S. continental shelf carbon budget: 

Modeling data assimilation and analysis [presentation], in

Ocean Carbon and Biogeochemistry Scoping Workshop 

on Terrestrial and Coastal Carbon Fluxes in the Gulf of 

Mexico, St. Petersburg, FL, May 6-8, 2008.

Nipper, M., Chavez, J.A.S., and Tunnell, J.W., Jr., 2004, 

Gulfbase: Resource database for Gulf of Mexico 

research: Corpus Christi, Texas A&M University. http://

www.gulfbase.org

NOAA, 2007, Gulf of Mexico ecosystems & hypoxia assessment (NGOMEX): Silver Spring, National Oceanic and 

Atmospheric Administration, National Ocean Service, 

National Centers for Coastal Ocean Science, Center for 

Sponsored Coastal Ocean Research. http://www.cop.noaa.

gov/stressors/pollution/current/gomex-factsheet.html

NOAA, 2008, Regional mean sea level trends: Silver Spring, 

MD, National Oceanic and Atmospheric Administration. 

http://tidesandcurrents.noaa.gov/sltrends/slrmap.html

NRC, 2002, Florida Bay research programs and their relation to the Comprehensive Everglades Restoration Plan: 

Washington, DC, National Academies Press, 54 p.

NRC, 2007, Earth science and applications from space: 

National imperatives for the next decade and beyond: 

Washington, DC, National Academies Press, 456 p.

Oey, L.Y., Ezer, T., and Lee, H.-C., 2005, Loop Current, rings 

and related circulation in the Gulf of Mexico: A review of 

numerical models and future challenges, in Sturges, W., 

and Lugo-Fernandez, A., eds., Circulation in the Gulf of 

Mexico: Observations and models; Geophysical Monograph 

Series v. 161: Washington, DC, American Geophysical 

Union, p. 11-29.

Ogle, S., and Davis, K., 2006, Science plan: Mid-continent 

intensive campaign of the North American Carbon Program: 

North American Carbon Program, 11 p. http://www.

nacarbon.org/nacp/documents/NACP_MCI_SciPlan_8-06.

pdf

Onstad, G.D., Canfield, D.E., Quay, P.D., and Hedges, J.I., 

2000, Sources of particulate organic matter in rivers from 

the continental USA: Lignin phenol and stable carbon 

isotope compositions: Geochimica et Cosmochimica Acta, 

v. 64, p. 3539-3546.

Orr, J.C., Fabry, V.J., Aumont, O., Bopp, L., Doney, S.C., 

Feely, R.A., Gnanadesikan, A., Gruber, N., Ishida, A., 

Joos, F., Key, R.M., Lindsay, K., Maier-Reimer, E., Matear, 

R., Monfray, P., Mouchet, A., Najjar, R.G., Plattner, G.-K., 

Rodgers, K.B., Sabine, C.L., Sarmiento, J.L., Schlitzer, R., 

Slater, R.D., Totterdell, I.J., Weirig, M.-F., Yamanaka, Y., 

and Yool, A., 2005, Anthropogenic ocean acidification over 

the twenty-first century and its impact on calcifying organisms: Nature, v. 437, no. 7059, p. 681-686.

Parrish, D.D., Hahn, C.J., Williams, E.J., Norton, R.B., 

Fehsenfeld, F.C., Singh, H.B., Shetter, J.D., Gandrud, 

B.W., and Ridley, B.A., 1992, Indications of photochemical 

histories of Pacific air masses from measurements of atmospheric trace species at Point Arena, California: Journal of 

Geophysical Research, v. 97, no. D14, p. 15883-15901.

Peng, T.-H., and Langdon, C., 2007, Gulf of Mexico and East 

Coast Carbon Cruise (GOMECC): Cruise report: Silver 

Spring, MD, National Oceanic and Atmospheric Administration. http://www.aoml.noaa.gov/ocd/gcc/GOMECC/

CruiseReportfinal.pdf

Pennock, J.R., Boyer, J.N., Herrera-Silveira, J.A., Iverson, 

R.L., Whitledge, T.E., Mortazavi, B., and Comin, F.A., 

1999, Nutrient behavior and phytoplankton production 

in Gulf of Mexico estuaries, in Bianchi, T., Pennock, J., 

and Twilley, R., eds., Biogeochemistry of Gulf of Mexico 

estuaries: New York, Wiley, p. 109-162.

Port of Houston Authority, 2008, General information: Houston, Port of Houston Authority. http://www.

portofhouston.com/geninfo/overview1.html

Rabalais, N.N., Turner, R.E., and Wiseman Jr, W.J., 2002, 

Hypoxia in the Gulf of Mexico, a.k.a. “The Dead Zone”: 

Annual Review of Ecology and Systematics, v. 33, 

p. 235-263.

Raymond, P., Oh, N., Turner, R., and Broussard, W., 2008, 

Anthropogenically enhanced fluxes of water and carbon 

from the Mississippi River: Nature, v. 451, no. 7177, p. 

449-452.

Raymond, P.A., and Cole, J.J., 2003, Increase in the export 

of alkalinity from North America’s largest river: Science, 

v. 301, no. 5629, p. 88-91.
44 Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico

Rutkowski, C.M., Burnett, W.C., Iverson, R.L., and Chanton, 

J.P., 1999, The effect of groundwater seepage on nutrient 

delivery and seagrass distribution in the northeastern Gulf 

of Mexico: Estuaries, v. 22, p. 1033-1040.

Sager, W., 2007, AUV and multibeam survey on the Florida 

Escarpment, 2007 Offshore Technology Conference, 

Houston, TX, 30 April - 3 May 2007. http://www.otcnet.

org/2007/technical/schedule/documents/otc184791.pdf

Sánchez-Gil, P., Yáñez-Arancibia, A., Ramírez-Gordillo, J., 

Day, J.W., and Templet, P.H., 2004, Some socio-economic 

indicators in the Mexican states of the Gulf of Mexico: 

Ocean & Coastal Management, v. 47, no. 11-12, p. 581-596.

Santschi, P.H., Oktay, S.D., and Cifuentes, L., 2007, Carbon 

isotopes and iodine concentrations in a Mississippi River 

delta core recording land use, sediment transport, and dam 

building in the river’s drainage basin: Marine Environmental Research, v. 63, no. 3, p. 278-290.

Sarmiento, J.L., and Wofsy, S.C., 1999, A U.S. carbon cycle 

science plan; Report of the Carbon and Climate Working 

Group for the U.S. Global Change Research Program: 

Washington, U.S. Global Change Research Program, 69 p.

Schifter, I., González-Macías, C., Miranda, A., and LópezSalinas, E., 2005, Air emissions assessment from offshore 

oil activities in Sonda de Campeche, Mexico: Environmental Monitoring and Assessment, v. 109, no. 1, p. 

135-145.

Schroeder, W.W., and Wiseman, W.J., 1999, Geology and 

hydrodynamics of Gulf of Mexico estuaries, in Bianchi, T., 

Pennock, J., and Twilley, R., eds., Biogeochemistry of Gulf 

of Mexico estuaries: New York, Wiley, p. 3-28.

SCOR and LOICZ, 2004, Submarine groundwater discharge: 

Management implications, measurements and effects: 

International Hydrological Program (IHP) and Intergovernmental Oceanographic Commission (IOC), IHP-VI series 

on groundwater no. 5; IOC manuals and guides no. 44, 35 p. 

http://unesdoc.unesco.org/images/0013/001344/134436e.

pdf

Seitzinger, S.P., Harrison, J.A., Dumont, E., Beusen, A.H.W., 

and Bouwman, A.F., 2005, Sources and delivery of carbon, 

nitrogen, and phosphorus to the coastal zone: An overview of Global Nutrient Export from Watersheds (NEWS) 

models and their application: Global Biogeochemical 

Cycles v. 19, p. GB4S01.

Siemens, A.H., Moreno-Casasola, P., and Bueno, C.S., 2006, 

The metabolization of dunes and wetlands by the City of 

Veracruz, Mexico: Journal of Latin American Geography, 

v. 5, p. 7-29.

Smith, S.V., and Hollibaugh, J.T., 1993, Coastal metabolism and the oceanic organic carbon balance: Reviews of 

Geophysics, v. 31, no. 1, p. 75-89.

Smith, S.V., and Mackenzie, F.T., 1987, The ocean as a net 

heterotrophic system: Implications from the carbon biogeochemical cycle: Global Biogeochemical Cycles, v. 1, no. 3, 

p. 187-198.

Solis, R.S., and Powell, G.L., 1999, Hydrography, mixing 

characteristics, and residence times of Gulf of Mexico 

estuaries, in Bianchi, T., Pennock, J., and Twilley, R., eds., 

Biogeochemistry of Gulf of Mexico estuaries: New York, 

Wiley, p. 29-61.

Stokstad, E., 1999, Scarcity of rain, stream gages threatens 

forecasts: Science, v. 285, p. 1199-1200.

Stumpf, R.P., and Haines, J.W., 1998, Variations in tidal level 

in the Gulf of Mexico and implications for tidal wetlands: 

Estuarine, Coastal and Shelf Science, v. 46, p. 165-173.

Sundquist, E., 2008, From carbon footprint to carbon pathway: 

carbon-cycle science at a crossroads [presentation], in

Ocean Carbon and Biogeochemistry Scoping Workshop 

on Terrestrial and Coastal Carbon Fluxes in the Gulf of 

Mexico, St. Petersburg, FL, May 6-8, 2008.

Sutyrin, G.G., Rowe, G.D., Rothstein, L.M., and Ginis, I., 

2003, Baroclinic eddy interactions with continental slopes 

and shelves: Journal of Physical Oceanography, v. 33, no. 1, 

p. 283-291.

Ternon, J.F., Oudot, C., Dessier, A., and Diverres, D., 2000, 

A seasonal tropical sink for atmospheric CO2 in the Atlantic 

Ocean: The role of the Amazon River discharge: Marine 

Chemistry, v. 68, no. 3, p. 183-201.

Thieler, E.R., and Hammar-Klose, E.S., 2000, National 

assessment of coastal vulnerability to future sea-level rise: 

Preliminary results for the US Gulf of Mexico coast: U.S. 

Geological Survey Open-File Report 00-179.

Thomas, H., Bozec, Y., Elkalay, K., and de Baar, H.J.W., 

2004, Enhanced open ocean storage of CO2 from shelf sea 

pumping: Science, v. 304, no. 5673, p. 1005-1008.

Tokoro, T., Watanabe, A., Kayanne, H., Nadaoka, K., Tamura, 

H., Nozak, K., Kato, K., and Negishi, A., 2007, Measurement of air-water CO2 transfer at four coastal sites using a 

chamber method: Journal of Marine Systems, v. 66, no. 1-4, 

p. 140-149.

Trefry, J., Butterfield, D., Metz, S., Massoth, G., Trocine, R., 

and Feely, R., 1994, Trace metals in hydrothermal solutions 

from Cleft segment on the southern Juan de Fuca Ridge: 

Journal of Geophysical Research, v. 99, p. 4925-4936.
Tsunogai, S., Watanabe, S., and Sato, T., 1999, Is there a continental shelf pump for the absorption of atmospheric CO2? 

Tellus B, v. 51, no. 3, p. 701-712.

Tunnell, J.W., Jr., 2007, Introduction, in Tunnell, John W., 

Jr., Chavez, E.A., and Withers, K., eds., Coral reefs of the 

Southern Gulf of Mexico: Corpus Christi, Texas A&M 

University Press, p. 1-4.

Turner, R., Rabalais, N., Alexander, R., McIsaac, G., and 

Howarth, R., 2007, Characterization of nutrient, organic 

carbon, and sediment loads and concentrations from 

the Mississippi River into the northern Gulf of Mexico: 

Estuaries and Coasts, v. 30, no. 5, p. 773-790.

Turner, R.E., and Rabalais, N.N., 1991, Changes in Mississippi River quality this century: BioScience, v. 41, no. 3, 

p. 140-147.

Turner, R.E., and Rabalais, N.N., 2004, Suspended sediment, 

C, N, P, and Si yields from the Mississippi River Basin: 

Hydrobiologia, v. 511, p. 79-89.

Turner, R.E., Rabalais, N.N., and Justic, D., 2008, Gulf of 

Mexico hypoxia: Alternate states and a legacy: Environmental Science and Technology, v. 42 no. 7, p. 2323-2327.

Turner, R.E., Rabalais, N.N., Swenson, E.M., Kasprzak, M., 

and Romaire, T., 2005, Summer hypoxia in the northern 

Gulf of Mexico and its prediction from 1978 to 1995: 

Marine Environmental Research, v. 59, no. 1, p. 65-77.

Upstill-Goddard, R., 2006, Air-sea gas exchange in the coastal 

zone: Estuarine, Coastal and Shelf Science, v. 70, no. 3, 

p. 388-404.

U.S. EPA, 1999, Ecological condition of estuaries in the Gulf 

of Mexico: U.S. Environmental Protection Agency Office of 

Research and Development, National Health and Environmental Effects Research Laboratory, Gulf Ecology Division 

EPA 620-R-98-004, 71 p. http://www.epa.gov/ged/docs/

EcoCondEstuariesGOM_print.pdf

U.S. EPA, 2007, Hypoxia in the Northern Gulf of Mexico: 

An update by the EPA Science Advisory Board: U.S. Environmental Protection Agency EPA-SAB-08-003, 333 p.

Vlahos, P., Chen, R.F., and Repeta, D.J., 2002, Dissolved 

organic carbon in the Mid-Atlantic Bight: Deep-Sea 

Research Part II, v. 49, no. 20, p. 4369-4385.

Vukovich, F.M., 2007, Climatology of ocean features in the 

Gulf of Mexico using satellite remote sensing data: Journal 

of Physical Oceanography, v. 37, no. 3, p. 689-707.

Walker, N.D., Wiseman, W.J., Jr., Rouse, L.J., Jr., and Babin, 

A., 2005, Effects of river discharge, wind stress, and slope 

eddies on circulation and the satellite-observed structure of 

the Mississippi River plume: Journal of Coastal Research, 

v. 21, p. 1228-1244.

Walsh, J.J., 1991, Importance of continental margins in the 

marine biogeochemical cycling of carbon and nitrogen: 

Nature, v. 350, no. 6313, p. 53-55.

Walsh, J.J., Dieterle, D.A., Meyers, M.B., and Muller-Karger, 

F.E., 1989, Nitrogen exchange at the continental margin: a 

numerical study of the Gulf of Mexico: Progress in Oceanography, v. 23, p. 245-301.

Walsh, J.J., Weisberg, R.H., Dieterle, D.A., He, R., Darrow, 

B.P., Jolliff, J.K., Lester, K.M., Vargo, G.A., Kirkpatrick, G.J., Fanning, K.A., Sutton, T.T., Jochens, A.E., 

Biggs, D.C., Nababan, B., Hu, C., and Muller-Karger, 

F.E., 2003, Phytoplankton response to intrusions of slope 

water on the West Florida Shelf: Models and observations: 

Journal of Geophysical Research, v. 108, no. C6, 3190, 

doi:10.1029/2002JC001406.

Wang, S.L., Chen, C.T., Hong, G.H., and Chung, C.S., 2000, 

Carbon dioxide and related parameters in the East China 

Sea: Continental Shelf Research, v. 20, no. 4-5, p. 525-544.

Wang, X.C., Chen, R.F., and Gardner, G.B., 2004, Sources and 

transport of dissolved and particulate organic carbon in the 

Mississippi River estuary and adjacent coastal waters of the 

northern Gulf of Mexico: Marine Chemistry, v. 89, no. 1-4, 

p. 241-256.

Wanninkhof, R., 2008, CO2 flux dynamics in the Gulf of 

Mexico [presentation], in Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon 

Fluxes in the Gulf of Mexico, St. Petersburg, FL, May 6-8, 

2008.

Wanninkhof, R., Asher, W., and Monahan, E.C., eds., 1995, 

The influence of bubbles on air-water gas exchange results 

from gas transfer experiments during WABEX-93, in Airwater Gas Transfer: Selected papers from the Third Symposium on air-water gas transfer, Hanau, Germany, Aeow 

Verlag, p. 239-255.

Wanninkhof, R., Hitchcock, G., Wiseman, W.J., Vargo, G.A., 

Ortner, P.B., Asher, W., Ho, D.T., Schlosser, P., Dickson, 

M.-L., Masserini, R.T., Fanning, K.A., and Zhang, J.-Z., 

1997, Gas exchange, dispersion, and biological productivity 

on the West Florida Shelf: Results from a Lagrangian tracer 

study: Geophysical Research Letters, v. 24, no. 14, p. 1767-

1770.

Wanninkhof, R., and Knox, M., 1996, Chemical enhancement 

of CO2 exchange in natural waters: Limnology and Oceanography, v. 41, no. 4, p. 689-697.
46 Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico

Wanninkhof, R., Lohrenz, S., and Cai, W.-J., 2007, Estimating 

air-sea carbon dioxide fluxes in the river-dominated 

northern Gulf of Mexico, in Northern Gulf Institute 

Conference, Biloxi, MS, May 16-17, 2007. http://www.

northerngulfinstitute.org/ngiconference/presentations/NGI_

Conf_Presentations_2007/19-Wanninkhof_NOAA_Project.

pdf

Ward, M., Harris, P., and Ward, A., 2005, Gulf Coast rivers 

of the southeastern United States, in Benke, A.C., and 

Cushing, C.E., eds., Rivers of North America: Amsterdam, 

Academic Press, p. 125-180.

Waterson, E.J., and Canuel, E.A., 2008, Sources of sedimentary organic matter in the Mississippi River and adjacent Gulf of Mexico as revealed by lipid biomarker and 

δ13C TOC analyses: Organic Geochemistry, v. 39, no. 4, 

p. 422-439.

Weisberg, R.H., Black, B., and Li, Z., 2000, An upwelling 

case study on Florida’s west coast: Journal of Geophysical 

Research, v. 105(C5), p. 11,459-11,469.

Wysocki, L.A., Bianchi, T.S., Powell, R.T., and Reuss, N., 

2006, Spatial variability in the coupling of organic carbon, 

nutrients, and phytoplankton pigments in surface waters 

and sediments of the Mississippi River plume: Estuarine, 

Coastal and Shelf Science, v. 69, no. 1-2, p. 47-63.

Yáñez-Arancibia, A., and Day, J.W., 2004a, The Gulf of 

Mexico: Towards an integration of coastal management 

with large marine ecosystem management: Ocean & Coastal 

Management, v. 47, no. 11-12, p. 537-563.

Yáñez-Arancibia, A., and Day, J.W., 2004b, Environmental sub-regions in the Gulf of Mexico coastal zone: 

The ecosystem approach as an integrated management tool: 

Ocean & Coastal Management, v. 47, no. 11-12, p. 727-757.

Yáñez-Arancibia, A., and Day, J.W., Jr., 2006, Hydrology, 

water budget, and residence time in the Terminos Lagoon 

Estuarine System, Southern Gulf of Mexico, in Coastal 

Hydrology and Processes: Proceedings of the American 

Institute of Hydrology 25th Anniversary Meeting & International Conference, Water Resources Publication, p. 423-436.

Yáñez-Arancibia, A., Lara-Domínguez, A.L., Rojas Galaviz, 

J.L., Zárate Lomeli, D.J., Villalobos Zapata, G.J., and 

Sánchez-Gil, P., 1999, Integrating science and management 

on coastal marine protected areas in the Southern Gulf of 

Mexico: Ocean & Coastal Management, v. 42, no. 2-4, 

p. 319-344.

Yuan, D., 2002, A numerical study of barotropicly forced 

intrusion in DeSoto Canyon: Journal of Geophysical 

Research, v. 107, no. C2, doi:10.1029/2001JC00079.

Zappa, C.J., Raymond, P.A., Terray, E.A., and McGillis, 

W.R., 2003, Variation in surface turbulence and the gas 

transfer velocity over a tidal cycle in a macro-tidal estuary: 

Estuaries and Coasts, v. 26, no. 6, p. 1401-1415.

Zavala-Hidalgo, J., Gallegos-García, A., Martínez-López, B., 

Morey, S.L., and O’Brien, J.J., 2006, Seasonal upwelling 

on the western and southern shelves of the Gulf of Mexico: 

Ocean Dynamics, v. 56, no. 3, p. 333-338.

Zektser, I.S., Dzhamalov, R., Everett, L.G., eds., 2007, 

Submarine groundwater: Boca Raton, CRC Press, 466 p.

Zhai, W., Dai, M., Cai, W.-J., Wang, Y., and Hong, H., 2005, 

The partial pressure of carbon dioxide and air-sea fluxes 

in the northern South China Sea in spring, summer and 

autumn: Marine Chemistry, v. 96, no. 1-2, p. 87-97.

Zhao, D., Toba, Y., Suzuki, Y., and Komori, S., 2003, Effect of 

wind waves on air-sea gas exchange: Proposal of an overall 

CO2 transfer velocity formula as a function of breakingwave parameter: Tellus B, v. 55, p. 478-487.

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– OFR 2009-1070 Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico, St. Petersburg, FL, May 6-8, 2008 L.L. Robbins and others –