ACCESS NUMBER: 30916 

STUDY TITLE: Deepwater Program: Gulf of Mexico Deepwater Information Resources 

Data Search and Literature Synthesis 

REPORT TITLE: Deepwater Gulf of Mexico Environmental and Socioeconomic Data 

Search and Literature Synthesis, Volume I: Narrative Report and Volume II: Annotated 

Bibliography 

CONTRACT NUMBER: 1435-01-98-CT-30916 

SPONSORING OCS REGION: Gulf of Mexico 

APPLICABLE PLANNING AREAS: Eastern, Central, and Western 

FISCAL YEAR(S) OF PROJECT FUNDING: 1998; 1999; 2000 

COMPLETION DATE OF REPORT: July 2000 

COSTS: FY 1998: $0; FY 1999: $118,621; FY 2000: $203,073; CUMULATIVE 

PROJECT COST: $321,694 

PROJECT MANAGER: D. Gettleson 

AFFILIATION: Continental Shelf Associates, Inc. 

ADDRESS: 759 Parkway Street, Jupiter, Florida 33477 

PRINCIPAL INVESTIGATORS*: E.G. Ward, W.R. Bryant, J.Y. Liu, W.D. Nowlin, A.E. 

Jochens, S.F. DiMarco, R.O. Reid, M.C. Kennicutt II, D.C. Biggs, P.H. Ressler, G.T. 

Rowe, I.R. MacDonald, S.T. Viada, D.B. Snyder, L.A. Tobin, N.W. Phillips 

KEY WORDS: Eastern Gulf; Central Gulf; Western Gulf; deepwater; oil and gas; 

synthesis; literature review; annotated bibliography; technology; geology; physical 

oceanography; chemical oceanography; plankton; water column; benthos; seep; 

chemosynthetic; socioeconomics 

BACKGROUND: Recent years have seen a great increase in oil and gas industry 

interest in the deepwater Gulf of Mexico. Deepwater development poses a number of 

environmental, socioeconomic, and technological issues. A “Deepwater Workshop” 

was held by the Minerals Management Service (MMS) in 1997. Workshop participants 

identified synthesis of existing environmental and socioeconomic data as an important 

priority. This synthesis report addresses the need for a comprehensive search and 

integration of environmental and socioeconomic data for the deepwater Gulf of Mexico. 

OBJECTIVES: The goal of this program was to gather environmental and 

socioeconomic information related to the deepwater environment, in order to describe 

the ecosystem; understand the environmental processes that drive the system; and 
ACCESS NUMBER: 30916 

understand potential sensitivities to oil and gas operations. Specific objectives were to 

develop (1) a computer-searchable annotated bibliography incorporating literature, 

relevant data, and ongoing research pertaining to geological, physical, chemical, and 

biological processes of the study area, social and economic data and literature, and 

deepwater technology; and (2) a synthesis report that describes the deepwater Gulf 

ecosystem, dominant environmental processes, biologically sensitive pathways, and 

socioeconomic activities in the area. 

DESCRIPTION: This report focuses on the deepwater Gulf of Mexico, defined as 

extending from a depth of 305 m (1,000 ft) to the border of the U.S. Exclusive Economic 

Zone. Conventional and innovative technologies used to explore and develop 

hydrocarbon resources in the deepwater Gulf of Mexico are described. The physical 

environment is described, including geology and physical and chemical oceanography. 

Biological communities of the water column and benthic environments are discussed, 

including chemosynthetic communities associated with hydrocarbon seeps. Fish 

communities and fisheries potentially affected by deepwater operations are described. 

Socioeconomic effects of oil and gas industry operations in the Gulf of Mexico are 

summarized. A synthesis chapter draws together information to contrast deepwater 

operations and deepwater environments with their shallow water counterparts. 

A computer-searchable annotated bibliography was also produced. 

SIGNIFICANT CONCLUSIONS: Deepwater operations differ from their shelf 

counterparts in several significant ways. These differences pose technical, 

environmental, and socioeconomic challenges, most of which are being addressed by 

ongoing and planned industry and MMS studies. The deepwater environment also 

differs from the better-known shelf environment in ways that could affect the nature of 

environmental and socioeconomic impacts. Areas of significant data gaps include 

geohazards, energetic currents, benthic processes, and linkages between the benthic 

and water column environments. 

STUDY RESULTS: Differences between deepwater operations and their shelf 

counterparts include higher production rates, which may affect spill probabilities and 

spill sizes; a shift from primarily bottom-founded structures (fixed platforms and 

compliant towers) to floating production systems (tension leg platforms, spars, 

semisubmersibles), and subsea production systems; a lower density of structures and 

reduced need for explosive platform removals; increased use of synthetic based drilling 

fluids; increased use of subsea wells tied to a floating production system; a need for 

longer, heavier pipelines to connect to existing infrastructure; problems keeping 

flowlines open due to formation of waxes and hydrates in cold temperatures; and use of 

floating production storage and offloading facilities (FPSOs) for transportation. These 

differences pose technical and environmental challenges, most of which are being 

addressed by ongoing and planned industry and MMS studies. 

The engineering and geological constraints on the continental slope off Texas and 

Louisiana related to hydrocarbon recovery will require both novel geological and 

geophysical surveys and engineering methods. Significant seafloor engineering 
ACCESS NUMBER: 30916 

problems in deep water include slope instabilities, both short-term (slump) and 

long-term (creep); pipeline spanning problems; mass transport from unknown causes; 

and unusual stiffness and strength conditions. 

Physical oceanographic characteristics of the deepwater Gulf may be of concern to the 

MMS from three perspectives: (1) facilities design; (2) pollutant transport; and 

(3) biological consequences, such as intensified primary and secondary production 

associated with cyclonic eddies and confluence zones between Loop Current eddies. 

Five classes of energetic currents in the deepwater Gulf of Mexico are of potential 

concern from a facilities design perspective. Oceanographic research has shown that 

the continental slope is characterized by a complex array of cyclonic and anticyclonic 

eddies of varying time and length scales. These features have substantial impacts on 

nutrient concentrations, plankton and micronekton communities, and cetacean 

distribution 

Chemically, the deep Gulf is buffered from the direct influence of coastal waters and 

processes, as reflected in low levels of anthropogenic contaminants in the water 

column. However, oceanographic mechanisms can transport low-salinity, nutrient-rich 

waters across the shelf and into the deepwater environment. Secondary movement of 

materials downslope is an important process as well. The benthic environment is 

mostly unaffected by anthropogenic impacts. Widespread natural seepage of oil, gas, 

and brines in near-surface sediments creates an unusual “natural background” of 

hydrocarbons, which is important when attempting to detect impacts of oil and gas 

activities. 

Standing stocks and productivity of plankton are low in the deepwater Gulf of Mexico. 

However, “hot spots” in primary production occur when/where nutrient availability is 

locally enhanced. Those deepwater “hot spots” that are temporally persistent (even if 

spatially variable) have higher stocks of zooplankton and micronekton. The occurrence 

of “hot spots” in the deepwater Gulf of Mexico is relevant not only to plankton, but to 

fisheries and apex predators like marine mammals. The presence of sizeable 

populations of apex predators in the deepwater Gulf of Mexico implies a reliable supply 

of lower trophic level prey resources and suggests that underlying physical processes 

allow “oases” of biological productivity to develop in the mostly oligotrophic deepwater 

environment. When/where they occur over deepwater in the Gulf, anticyclonic and 

cyclonic hydrographic features play an important role in determining biogeographic 

patterns of and controlling secondary productivity. 

Current deepwater fishing practices in the northern Gulf of Mexico include trapping for 

golden crab, trawling for royal red shrimp, bottom longlining for groupers and tilefishes, 

and surface longlining for sharks and tunas. Of these gear types, the pelagic longline 

presents the greatest possibility for interactions or space-use conflicts with the oil and 

gas industry. Another concern is the potential for interference with migratory routes due 

to attraction of epipelagic fishes (e.g., tunas, dolphin, billfishes, and jacks) to surface 

structures and mooring lines. Because of the highly migratory nature of many 

epipelagic species, these effects could extend to the regional scale (hundreds of 
ACCESS NUMBER: 30916 

kilometers). In addition, eggs and larvae of many epipelagic and mesopelagic fishes 

are commonly found in the surface waters of the deepwater Gulf, where they could be 

exposed to contaminants discharged from surface facilities. The potential for impacts 

could be higher where eggs and larvae are concentrated, as may occur in association 

with certain oceanographic features. 

In contrast with the continental shelf, the deepwater environment is inhabited by a 

relatively rich assemblage of up to 28 cetacean species. The assemblage includes 

resident population(s) of endangered sperm whales and several “cryptic” species 

(beaked whales, dwarf and pygmy sperm whales) whose habits are poorly known due 

to their avoidance of aircraft and ships. Therefore, many more cetacean species may 

come in contact with routine oil and gas operations in deepwater. Conversely, most 

historical sea turtle sightings have been recorded on the continental shelf. Historically, 

deepwater sea turtle sightings have consisted primarily of adult leatherbacks, with few 

loggerheads and Kemp’s ridleys (to the shelf edge only). Deep waters of the Gulf may 

also serve as developmental habitat for hatchling and juvenile sea turtles of the five 

Atlantic species, and may be used by all species as a transitory habitat. The presence 

and persistence of mesoscale oceanographic features strongly influences the 

distributions of protected species. Knowledge of these mesoscale features, as well as 

the ability to detect and track them through remote sensing, may provide a tool for 

mitigating some impacts of oil and gas operations in the deepwater Gulf. 

Most benthic studies have been descriptive, focusing on abundance, biomass, species 

composition, and zonation. While oceanographic mesoscale features are known to 

strongly affect water column primary and secondary productivity (“hot spots”), this 

understanding has not been extended to the benthos. It is reasonable to suspect that 

where water column “hot spots” persist spatially, benthic enrichment may occur. The 

implications for the deepwater benthos are just beginning to be investigated. Also, 

compared with the continental shelf, the northern Gulf of Mexico continental slope offers 

complex and rugged morphology including numerous submarine canyons and salt 

structures. Due to the water depth, true reef communities such as those seen on the 

shelf will not be present. However, there are some physiographic features whose 

benthic communities are practically unknown, including the Sigsbee and Campeche 

Escarpments. As additional information is obtained, new communities and resources 

may be encountered, and the MMS will need to evaluate their need for protection from 

oil and gas operations. 

Chemosynthetic communities are a distinctive and widespread feature of the deepwater 

environment. The amount of seafloor influenced by seepage is quite small compared to 

the extent of the subbottom hydrocarbon system, and industry engineers generally 

strive to avoid the unstable substrate at seeps. In addition, the MMS requires 

site-specific surveys for proposed bottom disturbing activities in water depths greater 

than 400 m to evaluate the potential for chemosynthetic communities. When such 

areas are identified, they are subsequently protected from physical disturbance from 

anchors, pipelines, chains, and templates. Current interest lies in improving the 

capacity to predict where seep communities will occur and in understanding processes 
ACCESS NUMBER: 30916 

that contribute to either stability or change in this environment so that anthropogenic 

changes could be distinguished from natural processes. 

STUDY PRODUCT(S): Continental Shelf Associates, Inc. 2000. Deepwater Gulf of 

Mexico Environmental and Socioeconomic Data Search and Literature Synthesis. 

Volume I: Narrative Report. U.S. Department of the Interior, Minerals Management 

Service, Gulf of Mexico OCS Region, New Orleans, LA. OCS Study MMS 2000-049. 

354 pp. 

Continental Shelf Associates, Inc. 2000. Deepwater Gulf of Mexico Environmental and 

Socioeconomic Data Search and Literature Synthesis. Volume II: Annotated 

Bibliography. U.S. Department of the Interior, Minerals Management Service, Gulf of 

Mexico OCS Region, New Orleans, LA. OCS Study MMS 2000-050. 298 pp. 

P.I.’s affiliation may be different than that listed for Project Manager(s).