Action, Monitoring, and Research Action, Monitoring, and Research
his assessment of the causes and consequences of Gulf of

Mexico hypoxia, and its analysis of options for dealing with it,

is drawn from the assembly and peer review of a massive

amount of direct and indirect evidence collected and reported

over many years of scientific inquiry. The findings presented are

thus well founded and are grounded in those research and monitoring results. There are, however, always uncertainties in scientific analysis. This section identifies areas of further monitoring

and research that are needed to reduce those uncertainties in

future assessments and to aid decision making in an adaptive management framework.

The complex nature of nutrient cycling and transport within

the MARB and Gulf of Mexico make it difficult to predict specific

improvements in water quality that will occur for a given reduction in nutrient inputs. Nutrient cycling is affected by atmospheric, watershed, riverine, and marine processes. Many of these

processes, such as nitrogen transformations in river reaches, are

not fully understood at the local scale at which they occur. Largescale, multidisciplinary interpretations that integrate knowledge

across these hydrologic compartments are difficult.

Further, it is clear that environmental responses to management

actions in the MARB likely will be slow, possibly requiring

decades of data to demonstrate statistically that remedial actions

have helped the recovery of oxygen concentrations in the Gulf

and have improved water quality in the Basin. For example, the

nitrogen balance in the soil zone and ground water will adjust relatively slowly to changes in nitrogen inputs and outputs, slowing

any change in the flux of nitrogen to the Gulf. At the same time,

the flux of nutrients to the Gulf most likely will respond quickly

and dramatically to large variations in precipitation and runoff—

further complicating measurement of reductions in nutrient flux. 

A comprehensive program of monitoring, interpretation, modeling, and research to facilitate continual improvement in scientific

knowledge and adjustments in management practices should be

coupled to whatever initial nutrient management strategies are

chosen (see Figure 6.1). This adaptive management scheme

involves continual feedback between interpretation of new information and improved management actions. 

Chapter 6: Adaptive Management ■ 47
Monitoring and Research in a

Modeling Framework

The adaptive management framework

includes monitoring programs that use

integrated models of the hydrologic and

ecological systems for interpretation of

system change. Whole-system monitoring

will enable comprehensive interpretation

of processes and linkages that affect nutrient concentrations and transport within

the MARB and development of hypoxia in

the Gulf. These coordinated monitoring

efforts must be able to: 

■ detect environmental trends to evaluate

the effectiveness of management

actions, to enable effective adaptation

of strategies over time;

■ observe physical, chemical, and biological processes and their roles in the

cause-and-effect relationships between

nutrient inputs and resulting environmental quality; and

■ differentiate among trends caused by

changes in climate, streamflow, nutrient and landscape management measures, and other concurrent factors.

An effective research strategy is also

integral to the adaptive management

framework. Coordinated research efforts

improve monitoring designs, support the

interpretation of monitoring output, and

increase the predictive

power of models and other

assessment tools used in the

management process.

For a system as large

and complex as the

MARB and the

northern Gulf of

Mexico, monitoring and

research should

be integrated using

holistic models that simulate

our understanding of how

the overall system functions

and how management practices can best be implemented. Such

holistic models include a suite of conceptual, functional, and numerical formulations; integrate research findings; and are

tied to monitoring programs designed to

both provide input variables and verify

model outputs. River monitoring data

should be integrated with offshore ecological and oceanographic data on appropriate time scales. An effective modeling

framework would include models that

simulate:

■ transport and transformation of nutrients (nitrogen, phosphorus, and silica)

from natural, urban, and agricultural

landscapes to ground water and surface

waters; 

■ inputs and outputs of nutrient flow

throughout the landscape to improve

estimates of nutrient mass balances;

■ biogeochemical cycling and water

quality effects of those nutrients on

river ecosystems within the drainage

basin;

■ oceanographic and climate influences

on those nutrients and their impacts on

Gulf productivity as they leave the

Mississippi–Atchafalaya River system; 

■ impacts of increased nutrient flux on

productivity in the northern Gulf of

Mexico ecosystem, including commercially and recreationally important fisheries; and

■ three-dimensional coupling of biological and physical processes in the Gulf

ecosystem influenced by the

Mississippi River discharge.

Within this larger modeling framework, important research and monitoring

needs have emerged from this assessment.

Monitoring gaps are found in environmental programs of the MARB and Gulf,

as well as in programs that monitor management measures. Research needs include

improving the quantitative understanding

of the biogeochemical cycling of nutrients

within the watershed and the Gulf and its

relationship to the dynamics of organic

carbon flux in the Gulf; the roles of longterm change in climate, hydrology, and

population in year-to-year and long-term

trends in nutrient loads and hypoxia; and

the social and economic impacts of various management and policy alternative

strategies.

48 ■ HYPOXIA IN THE NORTHERN GULF OF MEXICO

A comprehensive

program of

monitoring,

interpretation,

modeling, and

research should be

coupled to whatever 

initial nutrient 

management 

strategies are 

chosen 
Chapter 6: Adaptive Management ■ 49

Monitoring Needs

A comprehensive monitoring

program requires both measurement of environmental response

in the MARB and the Gulf of

Mexico and tracking indicators of

programmatic progress toward

mitigating excessive nutrients.

Environmental Responses 

in the Gulf

Essential components of an

environmental monitoring program in the Gulf of Mexico

include efforts to:

■ Document the temporal and

spatial extent of shelf hypoxia,

and to collect basic hydrographic, chemical, and biological data related to the

development and maintenance

of hypoxia over seasonal

cycles. A triad of mid-summer

shelf-wide hypoxia surveys,

monthly transects off Terrebone Bay, and instrumented

arrays at stations in the core

of the hypoxic zone would

provide an optimal combination of spatial and temporal

scales of measurement and

would be consistent with the

existing long-term data.

Establishing multiple vertical

and horizontal instrument

arrays oriented cross-shelf and

along-shelf will better define

processes that control the

temporal and spatial development of hypoxia.

■ Improve the collection of ecological, production, and economic information related to

fishery and nonfishery species.

■ Facilitate synthesis and interpretation of these data through

an integrated database.

Environmental Responses 

in the MARB 

Essential components of an

environmental monitoring program

in the MARB include efforts to:

■ Document the flux of nutrients,

carbon, and selected other

water quality constituents from

the MARB to the Gulf of

Mexico systematically on at

least a monthly basis and more

frequently at high flows—at

least 25–30 times annually.

Additional monitoring sites in

the main channel of the

Mississippi River are needed to

evaluate the extent of nutrient

retention/loss within the lockand-dam system, and to clarify

The adaptive management concept connects monitoring, analysis, and management actions with continuous feedback for

improvement. New understandings from research should be interwoven throughout the process.

Conduct research

Monitor

system

response

Implement

management

strategy

Interpret data,

analyze and

improve model

Improve model

prediction and

management plan

FIG. 6.1 Adaptive Management Framework

Source: Herb Buxton, U.S. Geological Survey
50 ■ HYPOXIA IN THE NORTHERN GULF OF MEXICO

the extent of nutrient retention

in the lower Mississippi. There

is a need to re-establish monitoring of nutrients, carbon, and

selected other water quality

constituents in the major subbasins (the 42 interior basins)

throughout the MARB and to

establish monitoring in selected small basins within some of

the 42 interior basins where

the effects of changes in land

management practices on

nutrient concentrations and

yields will be easiest to detect

and quantify. 

■ Monitor nutrients from atmospheric wet deposition in the

MARB, and expand the current

limited monitoring of nutrients

in atmospheric dry deposition.

This information is needed to

determine if nutrient management strategies affect precipitation chemistry.

■ Establish a periodic inventory

of effluent reporting conducted

through the National Pollution

Discharge Elimination System

(NPDES) to systematically

improve current estimates of

nitrogen and phosphorus loads

discharged to streams from

municipal and industrial point

sources.

■ Improve measurements for soil

nitrogen and nitrogen loss.

Programmatic Measures 

Ongoing programs are taking

action to improve water quality

conditions within the MARB and

Gulf of Mexico. Coordination of

current and future programs to

improve water and ecological

conditions can increase their overall effectiveness in achieving

goals. Some major measures of

progress of ongoing programs

include inventories of:

■ changing patterns in other

nutrient inputs to the Basin,

such as fertilizer use and

manure application and disposal;

■ acres of land leased annually

through the Conservation

Reserve Program and the

Conservation Reserve

Enhancement Program;

■ acres of created or restored

wetlands implemented through

the Wetlands Reserve Program,

the Emergency Wetlands

Reserve Program, the Clean

Water Act section 319 program, and the various environmental restoration and related

authorities, such as the Coastal

Wetlands Planning, Protection

and Restoration Act, the Environmental Management Program and other Corps of

Engineers programs, and the

Partners for Wildlife Program;

■ acres of riparian buffers implemented through the Conservation Buffer Initiative and the

Clean Water Act section 319

program; and

■ actions to reduce nutrient

runoff stimulated by the

Environmental Quality

Incentive Program and the

Clean Water Act section 319

program.

Research Needs

The research needs outlined

below fall into two categories: 

(1) immediate priorities that are

essential for designing near-term

management actions, and (2)

longer-term priorities that fill critical gaps in understanding as well

as guide efforts to mitigate and

control the effects of hypoxia and

excess nutrients.

Immediate Research Priorities

Ecological Effects of Hypoxia. A better definition of the past, current,

and potential impacts of hypoxia

on both commercially and ecologically important species and

ecosystems is needed. New retrospective analyses over longer temporal and spatial scales, based on

data from marine sediment cores

should improve the historical perspective. Better understanding of

other factors that affect the ecological health and fisheries of the

northern Gulf of Mexico is needed

to uniquely identify the role of

hypoxia and to design effective

management actions.

Contemporary effects. Additional

data sources have yet to be examined exhaustively, most notably

the SEAMAP database, which

includes long-term fishery-independent data on nektonic species’

composition in the northern Gulf

of Mexico ecosystem. Model

analyses of trophic structure and

ecosystem dynamics—which will

help identify affected fishery

resources, and assess potential

future impacts—are also needed. 

Historical perspective. The

northern Gulf of Mexico ecosystem may have already undergone

significant ecological change

prior to initiation of the first indepth scientific investigation in

the mid-1980s. Thus, the system

is likely in a transitional state as

nutrient loading approaches new

plateaus. Further research and

assessment of these longer-term

trends are needed. New retrospective analysis over longer

temporal and spatial scales, based

on data from marine sediment

cores should improve the historical perspective. 

Watershed Nutrient Dynamics.

There is a need to better understand the dynamics and timing of

movement of nitrogen and other

nutrients from the edge of the

field in agricultural landscapes to

small streams and tributaries.

Additional information is also

needed on the geographic distribution and design criteria for targeting wetland creation and

restoration efforts and to determine if other strategies (e.g.,

riparian buffers) and mixtures

provide the best nitrate reduction

for the least cost.
Chapter 6: Adaptive Management ■ 51

From edge of the field to streams.

There is a need to better understand the dynamics and timing of

movement of nitrogen and other

nutrients from the edge of the

field in agricultural landscapes to

small streams and tributaries. This

is especially true as it relates to

tile drains and other practices that

move nitrogen and other plant

nutrients through the soil

drainage system.

Wetlands creation. Additional

information is needed on the geographic distribution and design

criteria for targeting wetland creation and restoration efforts.

There is also a need to determine

which other strategies (e.g., riparian buffers) and mixtures provide

the best nitrate reduction for the

least cost. It is important to

understand and quantify the

potential for changes in the production of the greenhouse gas

N2O that could occur from wetland creation and restoration

efforts.

Agricultural Practices. While improvements in agricultural practices have been achieved in recent

years and the efficiency of nitrogen use has increased substantially, there is a need to better

quantify the effects of on-farm

practices and methods that intercept agricultural nutrients between

the field and ground water and

adjacent streams.

Watershed/farm-scale studies.

There is a critical need to scale up

from experimental plots to watershed/farm-scale studies falling into

two classes. The first class includes

studies to better quantify and

demonstrate the effects of on-farm

practices, such as precision farming, altered lateral spacing of

drainage tiles, controlled water

table levels, use of fall and winter

cover crops, altered timing of fertilizer application, and exploring

alternatives to traditional crop

rotations. The second class

includes studies on better means

to intercept agricultural nutrients

between the field and ground

water and adjacent streams

through riparian buffers, wetlands,

and other means.

Experimental policies and practices. Measuring and quantifying

the effectiveness of recent policies and voluntary actions to

reduce nutrient inputs should be

coordinated on a basin scale.

There is a need to better quantify

and understand the impacts of

current and proposed policies

(e.g., nutrient trading, fertilizeruse insurance) that increase

incentives to reduce nitrogen loss.

Additionally, there is a need to

evaluate how future policies or

Longer-Term 

Research Priorities

Nutrient Cycling and Carbon Dynamics

– Soil organic nitrogen

– In-stream, in-river, and Gulf sediment

denitrification

– Nutrient cycling in the northern Gulf of

Mexico

– Atmospheric deposition

Long-Term Changes in Hydrology, Climate, 

and Population

– Large-scale climate effects

– Flood events

– Mississippi–Atchafalaya River delta

management and restoration

– Point-source and urban nonpoint-source

controls

Economic and Social Impacts

– Economic values of river and lake water

quality improvements

– Economic values of Gulf water quality

improvements

– Economic trade-offs in agricultural systems

Immediate 

Research Priorities

Ecological Effects of Hypoxia

– Contemporary effects

– Historical perspective

Watershed Nutrient Dynamics

– From “edge-of-field” to

streams

– Wetlands creation

Agricultural Practices

– Watershed/farm-scale

studies

– Experimental policies and

practices

Research Priorities
RALPH LAURER

52 ■ HYPOXIA IN THE NORTHERN GULF OF MEXICO

practices might best be implemented and administered under

various institutional frameworks.

Longer-Term Research Priorities

Nutrient Cycling and Carbon

Dynamics. Research is needed to

improve understanding of nutrient cycling and carbon dynamics,

particularly variations across the

Basin and the relationship of sitespecific actions to Basin-scale

effects.

Soil organic nitrogen. Scientific

investigations indicate that the

soil zone is a huge storage reservoir of nitrogen. Both inputs to

and outputs from this reservoir

have increased dramatically in

recent decades. Research is

needed to better understand mineralization and immobilization

processes, to develop better

means to measure the amount and

forms of nitrogen in the soil reservoir, and to develop strategies to

minimize leaching of nitrate from

the soils to the streams.

In-stream, in-river, and Gulf sediment denitrification. There is a need

to better quantify denitrification

and nutrient retention rates in

small and large streams and in

Gulf sediments, and to compare

these rates to those achieved in

riparian buffers and wetlands. 

Nutrient cycling in the northern

Gulf of Mexico. Further refinements

of the relationships among nutrient

fluxes, nutrient ratios, and nutrient

cycling on the continental shelf in

the Gulf are necessary. Such refinements would improve simulations

of subsequent effects on primary

productivity, species composition,

development of hypoxia, and

higher trophic-level productivity in

the Gulf ecosystem. 

Atmospheric deposition. Additional research on atmospheric

deposition of nitrogen in the

Gulf is needed to improve understanding of various cycling mechanisms involving different forms

of nitrogen.

Long-Term Changes in Hydrology,

Climate, and Population. Additional

research is needed to more clearly

identify, understand, and predict

the effects of long-term changes in

hydrology, climate, and population.

Large-scale climate effects. The

relationship between large-scale

climate patterns (e.g., long-term

trends and changes in variability

of precipitation) and their potential impacts on river flows, nutrient flux, and flow dynamics on

the continental shelf need further

evaluation. Changes in precipitation, temperature, and flow patterns may have significant

long-term influence on the rate

and pattern of nitrate flux within

the basin, and on the physical

constraints of nitrate assimilation

in the northern Gulf. The potential effects of future global climate

change on such large-scale climate patterns should also be taken

into consideration. 

Flood events. Episodic events,

such as the Great Mississippi

River Flood of 1993 not only

have caused significant damage to

life and property, but also have

transported abnormally high

quantities of nitrogen and phosphorus to the Gulf. Studies are

needed to evaluate the potential

role of flood prevention and control methods that seek to distribute and retain more floodwater

within the Basin and thus increase

nitrogen retention, while protecting against flood damage.

Mississippi–Atchafalaya River

delta management and restoration.

Studies are needed to improve

understanding of nutrient cycling

in the deltaic plain in order to

guide possible changes in management activities, such as the

Scientists deploy conductivity, temperature, and depth (CTD) instruments, along

with dissolved oxygen sensors, to sample water conditions in the Gulf. 
Chapter 6: Adaptive Management ■ 53

diversion of floodwaters to delta

backwaters and coastal wetland

restoration.

Point-source and urban nonpointsource controls. The cost of nitrogen reduction from point sources

and from urban nonpoint sources

has been analyzed on the basis of

existing technologies and human

population densities. The potential for additional population and

landscape changes to offset

reductions achieved in nitrogen

loading from the Basin should be

carefully evaluated.

Economic and Social Impacts. In the

spirit of a “win-win” approach to

action plan design and implementation, all potential ancillary

social and economic benefits of

management actions as well as

potential adverse effects should

be identified and considered in

the design of monitoring and

research activities. 

Economic values of river and lake

water-quality improvements. The

benefits of reducing nutrient loads

in the freshwater system are considered significant. A great deal of

research into these benefits has

been conducted. Most studies,

however, have been site-specific

and have been performed for

selected watersheds or water uses.

There is a growing need for an

aggregated analysis of both direct

(e.g., drinking-water protection)

and indirect (increased recreation)

improvements in water quality, for

the Basin as a whole. 

Economic values of Gulf water

quality improvements. To date only

the potential direct economic

effects of Gulf hypoxia on commercial fish catch have been

attempted. Additional work

needs to be done to explore a

broader range of ecological

impacts, including potential

impacts to biodiversity and to

nonmarket-valued ecosystem

goods and services.

Economic trade-offs in agricultural systems. Better estimates of

cost savings to agricultural producers from reduced fertilizer

nutrient inputs are needed.

Similarly, better estimates of the

social costs that could result from

nitrogen management or reduction strategies (e.g., from dislocation in land use, agribusiness

infrastructure, and farm communities) are needed.