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Map of the risk of current fish habitat degradation of Northern Gulf of Mexico estuaries.
This ScienceBase item provides the queries and code that identifies components and organization of the detailed methodology for the National Fish Habitat Partnership's regional estuary assessment for the Northern Gulf of Mexico.
Assembling Response Data The assessment uses available fish and shellfish species presence/absence as indicators of the effects of anthropogenic (human caused) stressors on the estuarine habitats where fish and shellfish live, feed, and reproduce. Fish data were obtained from state and federal trawl survey programs, including each of the five coastal states as well as the U.S. Environmental Protection Agency’s (EPA) Environmental Monitoring and Assessment Program (EMAP) and National Coastal Assessment (NCA). Fish trawl nets are pulled through the water at specified sampling locations for a set period of time to determine the abundance and diversity of fish in the area. Environmental data like water temperature,...
Many of the Gulf Coast estuaries of Florida were scored to be at low or very low risk. However, Sarasota Bay scored at high risk, largely due to basin development. Although this variable is comprised of both urban and agricultural land use, urban development is the dominant landscape in this watershed. Other estuaries affected by urban land use are Galveston, Bay near Houston, and Lake Pontchartrain adjacent to New Orleans. In 2008, there were over 20 million people living in the coastal counties of the Gulf of Mexico, where the population increased by 103% since 1970. The Houston area, by highly stressed Galveston Bay, had the second most building permits, 56,863, in the nation in 2015. Runoff from these large...
Screening Responses to Individual Stressors We used hierarchical models to develop the northern Gulf of Mexico Regional Estuary Assessment. This approach is a compromise between pooling all data from each estuary together into a single model, and modeling each estuary separately. For hierarchical models, the intercept and/or slope parameters can vary among different groups in the model. The assessment defines groups as estuaries and states (FL, AL, MS, LA, and TX). “Random effects” in hierarchical models account for group-level differences that are not accounted for by the available predictor variables. For example, some variation between estuaries is due to different morphologies and physical features that are...
Relative condition of fish habitat in estuaries of the Northern Gulf of Mexico.
Integrating Data into a Spatial Framework This part of the assessment examined 33 estuaries across the northern Gulf of Mexico (Florida, Alabama, Mississippi, Louisiana, and Texas). These estuaries were cataloged in a spatial framework used to quantify and analyze the effects of stressors on the estuaries. The framework was composed of a series of estuaries, linked to associated shoreline buffer units, Estuarine Drainage Areas (EDAs), and watershed basins. The spatial framework was developed based on estuary boundaries used for the National Estuary Assessment. A number of changes were made for the northern Gulf of Mexico region to improve the way estuaries and their coastal catchments were defined in the framework...
Oil and gas exploration was not evaluated as a stressor variable in the 2015 assessment, but this practice obviously can affect Gulf habitats. With 45 percent of the nation’s petroleum refining capacity, the Gulf of Mexico is one of the most important regions for oil and gas production in the United States. Offshore oil production in the Gulf of Mexico accounts for 17 percent of total U.S. crude oil production and production is expected to increase in 2017. The federal Bureau of Safety and Environmental Enforcement reported that from 2007 to 2014, an average of ten oil spills releasing more than 50 barrels was reported per year just on the Outer Continental Shelf. Obviously, the worst incident was the Deepwater...
The Regional Estuary Assessment for the northern Gulf of Mexico represents an effort to develop, test, and implement a new assessment methodology for marine habitats that improves the analytical basis for identifying impacts to estuarine fish habitats. This new regional assessment approach offers several advantages: Incorporates information on fish/shellfish presence/absence from over 70,000 sampling events collected over two decades, so we can better relate fish habitat condition to natural and anthropogenic variables. Better accounts for the high amounts of natural variation found in the marine environment, which can affect the susceptibility of individual estuaries. Allows us to take advantage of regional datasets...
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The methodology used for Regional Estuary Assessment for the northern Gulf of Mexico represents the next generation development of estuary assessments and compares the relative condition of different estuary systems using biological indicators. A key challenge to measuring habitat stress within estuaries is separating cumulative anthropogenic (man-made) effects from the high degree of natural variability and statistical “noise” present in available datasets. Identifying indicators of estuary condition and measuring their status relative to some objective or relative benchmark can allow for comparisons between estuary systems. Fish and shellfish species are key biological indicators as they reflect the conditions...
The estuaries of Breton/Chandeleur Sound in Louisiana are affected by the annual formation of the northern Gulf of Mexico hypoxic (low oxygen) zone, which is primarily the result of excess nutrients from Mississippi River Basin into the Gulf of Mexico. Urban areas contribute to the nutrient loading but agricultural runoff is the primary source. These nutrients come from the entire basin, which begins in Minnesota and extends through the “farm belt” of the nation. Nutrients are required for plant growth and excess nutrients increase algal growth. The algae then die and decompose, using up oxygen in the process. In 2015, this so-called “ Dead Zone” was 6,474 square miles - about the size of Connecticut and Rhode Island...
This item provides the ScienceBase query that identifies components of the fish habitat assessments within the Northern Gulf of Mexico estuaries. It also contains a link to a configuration file that pulls these pieces of information into a logical order. This information can be accessed through the ScienceBase API to display a summary of fish habitat assessment information for the Northern Gulf of Mexico estuaries.
There were two different assessments completed for estuaries of the Northern Gulf of Mexico, one is part of the National Estuary Assessment and the other is a regional estuary assessment. The National Estuary Assessment ranked the condition of Gulf estuaries relative to other estuaries in the contiguous U.S. using a simple index-based approach. The National Estuary Assessment results for the Gulf of Mexico are discussed in both the Eastern Gulf of Mexico and Southern Plains regional sections of this report. The Regional Estuary Assessment used a new detailed approach that fully incorporates fish survey data to better measure the effects of human-caused (anthropogenic) activities on fish habitat and is the prototype...
Identifying Disturbances to Fish Habitat Multi-stressor models were used to identify the most important disturbance factors for Gulf estuaries. For each species, the significant stressors identified in the screening models, along with the event-level variables (temperature, salinity, distance to shore) were combined using a backward selection process to develop a final model for each individual fish species. Backward selection eliminates variables in a stepwise fashion based on statistical significance, until only highly significant (95% confidence level) predictors are left in the model. Once final model configurations for each species were complete, they were used to measure anthropogenic disturbance levels...
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Assembling Predictor Data Predictor data variables include both anthropogenic stressors and natural variables that can affect the susceptibility of estuaries to pollutants and other stressors. Predictors for this assessment were measured at two different scales in space and time: “event-level” and “estuary-level”. Event-level data were recorded at the specific times and locations of individual fish trawls and include variables like water temperature, salinity, and location (i.e. distance to shore). Estuary-level data refers to values averaged at the estuary level. Estuary-level variables include a range of anthropogenic stressors (e.g. nutrient loadings, toxic releases, land use, and population characteristics),...