mill plants, fish processing, commercial and recreational fisheries, municipal wastewater treatment, maritime shipping, and land modifications for flood control, river development, and for harbors, docks, navigation channels and pipelines. The petrochemical industry located along the Gulf coast is the largest in the United States and includes extensive oil and gas development operations occurring both onshore and offshore, tanker and barge transport of both imported and domestic petroleum into the Gulf region, and petrochemical refining and manufacturing operations. Louisiana imports more hazardous waste than any other State, about 600,000 tons per year (Times Picayune, 1992).

The Gulf of Mexico has more point sources of contaminants than any other region in the country - more than 3,700 sites, according to one assessment (Weber, Townsend, and Bierce, 1992). Point sources contribute contaminants through discharges and accidental releases. More than half of the 3,700 sites were industrial facilities. Four hundred and sixty point sources discharge directly into the waters of the Gulf or its estuaries. Of this total, 113 are municipalities, which discharge primarily sewage wastes, discharging more than a billion gallons a day of sewage effluent to Gulf coastal waters (Weber, Townsend, and Bierce, 1992). Of the 460 sources, 192 were in Texas, 79 in Louisiana, 30 in Mississippi, 29 in Alabama, and 17 in Florida. Most were petroleum refineries and petrochemical plants. Another major point source of contamination to Gulf waters is vessel traffic. Vessel are contributing bilge and waste discharges, spills, and the leaching of tributyl tin from ship hulls near marinas. Of the 10 busiest ports in the United States, 4 are located on the Gulf coast. Adding to vessel traffic from commercial shipping is the largest commercial fishing industry in the United States and a large recreational boating industry.

Hydromodification, which includes, channelization, wetland dredge and fill modifications, and natural subsidence in the coastal zone is also strongly altering the Gulf's coastal water quality. These activities are resulting in sediment deficit and saltwater intrusion, particularly in the Louisiana coastal area. Saltwater intrusion is defined as the inland movement of offshore saline waters into more brackish and fresh waters. To support oil and gas projects within Louisiana, about 9 to 10 million cubic meters of material is estimated to be dredged every year. Most material dredged from the extensive navigational channels system is dumped at 27 dredged material disposal sites located along the Gulf of Mexico coastline. On an average about 25 million cubic meters of sediments are disposed of at these sites annually. Dredged material disposal results in temporarily increased turbidity and resuspension of released sediment contaminants into coastal waters.

Despite the level of point sources, nonpoint sources of contaminants entering coastal waters from riverine outflows into the Gulf of Mexico, primarily that of the Mississippi River, impact, to the largest extent, coastal water quality. Major categories of nonpoint pollutant sources include agriculture, forestry, urban runoff, marinas and recreational boating, and hydromodification. Waterways draining over two-thirds of the United States enter the Gulf, transporting the wastes from three-fourths of the United States's farms and ranches, 80 percent of the U.S. cropland, hundreds of cities, and thousands of industries not located in the Gulf's coastal zone. Urban and agricultural runoff contribute large quantities of nutrients, pesticides, and fecal coliform bacteria.

Over 10 million pounds of pesticides were applied within the Gulf of Mexico coastal area in 1987, making it the top user of pesticides in the country (USDOC, NOAA, 1992a). The Gulf of Mexico ranked highest in the use of herbicides (6.6 million pounds) and fungicides, and a close second in the use of insecticides. The Atchafalaya/Vermilion Bays, the Lower Laguna Madre, and Matagorda Bay ranked in the top 10 estuarine drainage areas in the U.S. for carrying pesticides to coastal waters. Although ranking high based on inputs, when NOAA normalized pesticide use for risk to estuarine organisms (USDOC, NOAA, 1992a), the Gulf fared better; Tampa Bay and the Lower Laguna Madre were the only two drainage basins in the top 10.

Excess nutrients primarily found in river runoff is one of the greatest sources of contamination to Gulf coastal waters. Nutrient overenrichment can lead to noxious algal blooms, turbidity blooms, decreased seagrasses, fish kills, and oxygen-depleted events. Loadings of nitrogen and phosphorus in the Mississippi River and the entire Gulf coast have risen dramatically over the last three decades (Rabalais, 1992). The Nutrient Enrichment Subcommittee of the Gulf of Mexico Program studied nutrient loadings into Gulf coastal waters (Lovejoy, 1992). They estimated that more than 379,000 pounds of phosphorus and over 1.87 million pounds of Kjeldahl nitrogen are discharged into the Gulf on an average day; 90 percent of both elements coming from the Mississippi River system. Low dissolved oxygen occurring in the summer in Gulf coastal waters has been shown to be from a combination of high nutrient or organic matter levels, high water temperatures, high benthic metabolic rates, low light penetration, and weak winds resulting in density stratification. Nutrient overenrichment have been noted in recent years in Gulf Coast estuaries, particularly as a water quality problem for the Lower and Upper Laguna Madre, Texas; Lake Pontchartrain, the Mississippi River and Barataria Bay, Louisiana; Mississippi Sound, Pascagoula Bay, and Biloxi Bay, Mississippi; and Perdido, Pensacola, Choctawhatchee, and St. Andrews Bay, Florida (Rabalais, 1992).

A good indicator of coastal and estuarine water quality is frequency of fish kill events and the closures of commercial oysters harvested from its waters. Of the top 10 fish kills reported in the United States between 1980 and 1989, 5 occurred in Texas (3 in Galveston County, 1 in Harris County, Texas and 1 in Chambers County, Texas) (USDOC, NOAA, 1992b). Because oysters are filter feeders, these bottom dwellers may concentrate pollutants and pathogens. The oyster industry is a good indicator of impacts from septic tank runoff pollution. About half of the harvestable shellfish beds in Louisiana are closed annually because of Ecoli bacteria contamination. Most of the productive oyster reefs in Gulf estuaries are in conditionally approved areas or areas where shellfish harvesting is affected by predictable levels of pollution.

Since 1984, the National Oceanic and Atmospheric Administration (NOAA) has monitored, through its National Status and Trends Program (NST), the concentrations of synthetic chlorinated compounds such as DDT, chlordane, polychlorinated biphenyls (PCB's), tributyl tin, polynuclear aromatic hydrocarbons (PAH's) and trace metals in bottom feeding fish, shellfish, and sediments at coastal and estuarine sites located along the Gulf of Mexico (U.S Department of Commerce, 1992c). Site selection attempted to be random and representative of general conditions in estuaries and nearshore waters, away from waste discharge points. Eighty-nine sites were sampled along the Gulf coast and compared to more than 300 sites located throughout the U.S. coastal areas. The following information summarizes NOAA's findings for both sediments and shellfish. NOAA defines "high" levels of a compound class as one where the logarithmic value is more than the mean plus one standard deviation of the logarithm. Chemical concentrations exceeding natural levels are considered contamination.

Oysters were sampled for 5 years as part of NOAA's (NST) National Mussel Watch Program. Examining the entire U.S. coastal area, the highest chemical contamination consistently occurred near urban areas. Fewer sites in the Gulf of Mexico were contaminated than in other coastlines, probably because urban centers along the Gulf are further inland than those near other coasts. Of the top six U.S. urbanized areas showing high levels of organic compound contamination in shellfish, Mobile Alabama was the only site in this group. Sites located along the Gulf having oysters containing at least three compounds with "high" concentrations included: Panama City, Choctawhatchee Bay, Florida; Mobile Bay, Alabama; Lake Borgne, Louisiana; and Galveston Bay, Brazos River, Corpus Christi, and the Lower Laguna Madre, Texas (O'Connor, 1992). Moderately elevated concentrations of pesticides and polychlorinated biphenyls (PCB's) appeared along the central Louisiana coastline and at isolated stations in Texas (Matagorda and Galveston Bays) (Texas A&M University, 1988). Within Gulf samples, the highest concentrations of chlorinated hydrocarbons were observed along the Mississippi to northern Florida coast and at stations in Tampa Bay. High cadmium concentrations in oysters

occurred at some sites for some years, but the reasons for the changes in cadmium levels could not be explained. Mercury was found to be high in Matagorda Bay, TX; probably related to a major discharge of this element in the area in the 1970's (USDOC, NOAA, 1992c). There were also some temporal trends that were apparent in the data. DDT concentrations in oysters showed significant decreases over the 5 years sampled, as hoped for since DDT use is no longer allowed. In Terrebonne Bay, Louisiana, arsenic showed consistent decreases while zinc increased each year.

Sediment data were collected and examined in the same manner (O'Connor, 1990). As in benthic samples, higher levels of sediment contamination was associated with highly populated areas, and in general, sites in the Gulf of Mexico had lower concentrations of toxic contaminants than the rest of the country. Again, the likely reason for this finding was that site locations in the Gulf of Mexico were in estuaries and nearshore waters, away from discharge points. The geographical trends in organochlorine loadings in sediments followed those observed in oysters (Texas A&M University, 1988). Florida sites exhibited 17 contaminant concentrations among the top 20 nationally; Mississippi and Texas each had one site; and Alabama and Louisiana had none (USDOC, NOAA, 1992c). Florida was one of four States that have contaminant concentrations in the top 20 nationally for all selected toxics; Mississippi's site ranked high only for polynuclear aromatic hydrocarbons, and the Texas's site had high DDT's. Areas containing sediments with chemical concentrations exceeding "high" levels include Tampa Bay, Panama City, St. Andrew Bay, and Choctawhatchee Bay, all in Florida, and Biloxi Bay, Mississippi and Galveston Bay, Texas.

Another report by the National Status and Trends Program examines the spatial distribution of sediment contamination data from six different electronic information systems maintained by EPA or NOAA (Daskalakis & O'Connor, 1994). The report's conclusion that the Gulf of Mexico has more areas with "high" concentrations than other U.S. coasts contradicts the conclusions presented above that are based only on the NOAA Status and Trends dataset. Although the report does not explain this discrepancy, it does state that the majority of the six databases provide chemical concentration information directly linked to discharge site locations. Knowing that the Gulf of Mexico has the greatest number of waste discharge point sources, it is not surprising that, when comparing data for samples taken in association with point sources, the Gulf of Mexico shows a large number of sites with "high" levels of contamination than in other regions.

The Gulf of Mexico is influenced by a maritime subtropical climate controlled mainly by the clockwise wind circulation around a semipermanent area of high barometric pressure alternating between the Azores and Bermuda Islands. This circulation, around the western edge of the high pressure cell, aided by the trade winds, results in the predominance of moist easterly wind flow in this area. Another factor influencing the climate in the Gulf is the persistence of high barometric pressure over the North American continent during the winter months, resulting in rare periods of relatively dry northerly wind flow over the Gulf. Humidity, cloudiness, visibility, precipitation, and air temperatures over the Gulf are typical of a maritime climate and show little diurnal or seasonal variation. Tropical storms also effect this area, and a hurricane can be expected to influence the Gulf at least once every 2 years.

Further information on climatic and meteorologic conditions for the Gulf of Mexico can be found in Balsillie (1985); Brower et al. (1972); CEI (1977); Chatry (1986); DeWald (1982); Louisiana Geological Survey (1985 and 1986); McGowen et al. (1970); Tatum (1985); and USDOI, BLM (1982).

Air quality of the coastal areas bordering the Gulf of Mexico is measured against the National Ambient Air Quality Standards (NAAQS) resulting from the Clean Air Act, as amended, or more restrictive standards adopted by a State. The NAAQS have been adopted by four of the States coastal to the Gulf of Mexico. Florida has amended these standards to make total suspended particulates (TSP) and Sulfur Dioxide (SO2) emissions more restrictive. The regulation of air quality east of 87.5 degrees longitude, i.e., offshore of Florida, falls to the EPA, therefore few references will be made to air quality issues in this area.

The State of Texas is considered attainment for the pollutants SO, and NO2. Exceedances of the national standards for CO and PM10 have only been measured in the interior of the State. Thus, there have been no exceedances of the NAAQS for SO2, NO2, CO and PM10 in Texas coastal areas. The following Texas coastal counties are classified as nonattainment for ozone (O3): Brazoria, Chambers, Fort Bend, Galveston, Harris, Liberty, Victoria, Jefferson, Hardin, and Orange. Louisiana is considered to be in attainment of the NAAQS for CO, SO2, NQ, and PM. Twelve coastal Louisiana parishes have been tentatively designated nonattainment for ozone, with eight of those parishes pending attainment approval under USEPA review. Ozone measurements (Louisiana Department of Environmental Quality, 1993) between 1989 and 1993 show that the number of days exceeding the national standards are declining. All coastal counties in Mississippi and Alabama are classified as clean air counties; TSP and SO2 meet the NAAQS and O,, CO, and NO2 meet the standards or cannot be classified.

Class I Federal areas have been designated for mandatory Prevention of Significant Deterioration (PSD) of air quality, including such Air Quality Related Values (AQRVs) as visibility. Class I areas are located in two of the five Gulf Coast states: Louisiana and Florida. In Louisiana there is one Class I area, and Florida has three. The Class I area offshore of Louisiana is comprised of the Breton Wildlife Refuges, located on Breton Island and on many of the Chandeleur Islands. All five States have State Implementation Plans for air quality coupled with regulatory enforcement and monitoring programs in operation.

In 1993, MMS in conjunction with the EPA completed a preliminary OCS contributions to ozone formation using the Regional Oxidant Model (ROM) for episodes with onshore transport (USDOI, MMS, 1993b). This preliminary screening showed the impact on maximum episodic ozone concentrations predicted over land due to OCS emissions was small (5-10 ppb) and could be as high as 10-20 ppb. The study recommended an improved emissions database and the use of a finer resolution photochemical model to assess OCS contributions to coastal ozone nonattainment areas.

The MMS subsequently has completed a more extensive study, the Gulf of Mexico Air Quality Study (GMAQS)(USDOI, MMS, 1995), of the impact of OCS activities upon the ozone nonattainment areas of coastal Texas and Louisiana. This study involved the collection of meteorological data, air samples, an updated emissions database and the modeling of ozone episodes using the Urban Airshed Model, variable grid (UAM-V).

The GMAQS showed OCS contributions to ozone exceedance episodes, in coastal Texas and Louisiana, during August and September of 1994, to be less than 2 ppb. It also showed that extended periods with onshore winds resulted in substantially decreased ozone levels in coastal areas. With extended periods of onshore winds, one would expect the OCS contribution to the ozone level to increase, and the study did show this. Modeling runs put OCS increments of ozone, during these periods, as high as 10-12 ppb in the Houston, Beaumont and Port Authur areas, 10-15 ppb in the Baton Rouge area and 8-10 ppb in the Lake Charles area. The corresponding total ozone levels for these areas, during these periods, were in the 30-60 ppb range.

Overall, the GMAQS showed that OCS activities have a very minimal impact (less than 2 ppb) during periods of exceedance of the NAAQS of 120 ppb for ozone in coastal areas of Texas and Louisiana; and that OCS activities are projected to continue to have a minimal impact on exceedance episodes in these areas.

There are five baleen (northern right, blue, fin, sei, and humpback) and one toothed (sperm) whale species occurring in the Gulf of Mexico that are endangered. The sperm whale is common in the Gulf, while the baleen whales are considered uncommon (Davis et al., 1995). Two families of baleen whales occur in the Gulf: balaenids (northern right) and balaenopterids, or rorquals (blue, fin, sei, and humpback).

The northern right whale is one of the stockiest of all whales; it has a massive head that can be up to nearly one-third of its body length (Jefferson et al., 1993). Right whales forage primarily on subsurface concentrations of calanoid copepods by skim feeding with their mouths agape (Watkins and Schevill, 1976). The northern right whale is one of the world's most endangered whales. The western North Atlantic population (numbering 300-350 individuals) ranges primarily between Nova Scotia and Florida (USDOC, NMFS, 1991a). Confirmed historical records of northern right whales in the Gulf of Mexico consist of a single stranding in Texas (Schmidly et al., 1972) and a sighting off Florida (Moore and Clark, 1963; Schmidly, 1981). The northern right whale is not a normal inhabitant of the Gulf of Mexico; existing records probably represent extralimital strays from the wintering grounds of this species off the southeastern United States, from Georgia to northeastern Florida (Davis et al., 1995). The coastal nature and slow swimming speed of the northern right whale makes it vulnerable to human activities (USDOC, NMFS, 1991a).

The blue whale is the largest animal ever known. Like all rorquals, the blue whale is slender and streamlined. The blue whale feeds almost exclusively on zooplankton via a combination of gulping and lunge-feeding in areas of heavy prey concentration (Yochem and Leatherwood, 1985). The blue whale occurs in all major oceans of the world; some blue whales are resident, some are migratory (Jefferson et al., 1993). Those that migrate move poleward to feeding grounds in spring and summer after wintering in subtropical and tropical waters (Yochem and Leatherwood, 1985). It is believed that the entire surviving blue whale population in the North Atlantic consists of only a few hundred individuals (Leatherwood and Reeves, 1983). Records of the blue whale in the Gulf consist of two strandings on the Texas coast (Lowery, 1974). There appears to be little justification for considering the blue whale to be a regular inhabitant of the Gulf of Mexico (Davis et al., 1995).

The fin whale is the second largest rorqual. The fin whale has unusual head coloration; it is markedly asymmetric with the right lower jaw being largely white in contrast to the rest of the head which is dark. Fin whales are active lunge feeders, taking small invertebrates, schooling fishes, and squid (Jefferson et al., 1993). Fin whales have a worldwide distribution and are most commonly sighted where deep water approaches the coast (Jefferson et al., 1993). The fin whale makes regular seasonal migrations between temperate waters, where it mates and calves, and the more polar feeding grounds occupied in the summer months. Sightings in the Gulf have typically been in deeper waters, more commonly in the north-central area (Mullin et al., 1991). There are seven reliable reports of fin whales in the Gulf, indicating that fin whales are not abundant in the Gulf of Mexico (Davis et al., 1995). It is possible that the Gulf represents a portion of the range of a low