Gulf Coast Estuaries: National Coastal Condition Assessment 2015

Setting

The coastal resources of Gulf of Mexico Coast region are diverse and extensive, covering an estimated 10,715 square miles. The region extends from Florida Bay in the east through the Texas-Mexico border to the west. The provinces of this region are a portion of the West Indian Province, whose waters are similar to those of subtropical ecosystems, extends from the  Florida Keys up the west coast of Florida, including Tampa Bay; and the Louisianian Province which goes from Anclote Key, FL through the Texas coast.

Gulf Coast estuaries, bays, and wetlands provide critical feeding, spawning, and nursery habitat for a rich assemblage of fish and wildlife, including essential habitat for commercially and recreationally important fish, shrimp, and birds. The Gulf Coast is also home to a diverse array of unique coastal ecosystems, including hypersaline lagoons, coral reefs, and mangrove forests.

More than half of the coastal wetlands in the conterminous United States occur along the Gulf Coast, providing a wide range of ecosystem services, such as fishery support, storm-surge and sea-level protection, water quality improvement, wildlife habitat provision, recreational opportunities, and carbon sequestration.

Between 2010 and 2020, the aggregated population of coastal shoreline counties bordering the Gulf of Mexico increased by nearly 13%. The greatest increases were in counties of the West coast and panhandle of Florida, Baldwin County Alabama bordering Mobile Bay, and the counties surrounding Galveston Bay in Texas. Throughout the rest of the Gulf of Mexico Region, shoreline county populations grew at slow rates, remained steady or decreased. Kennedy County in Southeast Texas has the distinction of having the smallest population of all US Shoreline counties, with 350 people counted in the 2020 census, a decrease of nearly 16% since 2010¹.

Biological Condition

The NCCA found that in 2015, biological condition was good in 68% of the estuaries in the Gulf of Mexico, according to the M-AMBI marine benthic index. This is similar to the overall national estimate of estuaries in good biological condition of 71% and is not significantly different from the proportion of Gulf of Mexico area rated good in 2010.

Eutrophication Index

The eutrophication index, which examines the potential for estuarine area to undergo social eutrophication based upon measurements of nutrients, chlorophyll a, dissolved oxygen and water clarity, found that 18% of Gulf of Mexico estuarine area was in good condition, 55% of area was in fair condition and 28% in poor condition. This indicates that the estuarine area in the Gulf is more likely to experience eutrophication than the country as a whole, but doesn’t represent a statistically significant change since 2010. There is a need for continued improvements in nutrient management in waters that flow into estuaries of the Gulf of Mexico.

Sediment Quality Index

About 75% of Gulf of Mexico estuarine area had good sediment quality based on measures of chemical contaminants found in sediments and laboratory tests of toxicity. This is similar to the rest of the estuarine area in the continental US in 2015 and shows statistically significant improvement over the NCCA results for sediment quality in the Gulf of Mexico in 2010.

Ecological Fish Tissue Contaminants

Ecological fish tissue contamination was degraded in estuaries of the Gulf of Mexico in 2015 with 74% of waters in poor condition and 15% in fair. Only 9% of the area is rated good. The proportion of area rated poor for ecological fish tissue contaminants in the Gulf of Mexico is higher than the national estimate of 55%. However, a closer look at the data reveals that the area not assessed (area for which fish suitable for analysis could not be caught) in the Gulf is only 1%, while the national estimate of not assessed area is about 10%, and is as high as 28% in estuaries of the West Coast. Care must be taken when comparing populations when there is a wide range of area for which assessments are not available for an indicator. It is important to note that this assessment of potential for adverse effects applies only to wildlife that eat fish and does not apply to people.

Human Health Indicators

More than 99% of Gulf of Mexico estuarine waters have low levels of bacteria and microcystin and are safe for recreation.

Because field crews were unable to catch fish that were suitable for human consumption, 30% of the estuarine area in the Gulf of Mexico was unassessed for mercury contamination in fish fillet plug samples; no estimate of area with mercury contamination either above or below the 300 parts per billion human health consumption benchmark is available for that proportion of the Gulf of Mexico. About 4% of Gulf Coast estuarine area have fish with concentrations of mercury in fillet plug samples exceeding the human health benchmark while fish from 66% of the area posed little to no risk for human consumption. In order to address the large proportion of area that was unassessed, the NCCA implemented new fish fillet plug sampling procedures in 2020.

A fish fillet “plug” is a small biopsy sample taken from a live fish. The fish is released after sampling.

PCBs and PFOS in whole fish fillets were only assessed in Great Lakes nearshore waters.

Recreational anglers should consult local fish consumption advisories before eating their catch.

To access more indicator graphics please visit the interactive NCCA dashboard.​

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