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Environmental Conditions in Northern Gulf of Mexico Coastal Waters Following Hurricane Katrina

Author(s): Macauley, J., L.M. Smith, V. Engle, L. Harwell, W. Berry, J. Hyland, M. Fulton, G. Lauenstein, P. Bourgeois, T. Heitmuller


Publication Type: NOAA Special Reports

Journal Title: US EPA Technical Report Series No. EPA/600/R-07/063

Date of Publication: 2007

Reference Information: 63 pages

Keywords: Hurricane Katrina environmental effects; Gulf of Mexico; extreme natural events; hurricane impacts; EMAP

Abstract: EXECUTIVE SUMMARY: On the morning of August 29, 2005, Hurricane Katrina struck the coast of Louisiana, between New Orleans and Biloxi, Mississippi, as a strong category three hurricane on the Saffir-Simpson scale. The resulting winds, storm surge, and flooding created the potential for a tremendous environmental impact along the northern Gulf of Mexico coast. The U.S. Environmental Protection Agency (EPA), National Oceanic and Atmospheric Administration (NOAA), and U.S. Geological Survey (USGS) conducted a joint study in October 2005 to assess potential ecological effects of the hurricane in coastal waters of Lake Pontchartrain, Louisiana, and Mississippi Sound from Dauphin Island, Alabama, to the western side of Lake Borgne, Lousiana. Post-hurricane conditions were compared to pre-hurricane conditions using data collected from the same areas in 2000 to 2004 with similar indicators and protocols. Monitoring surveys were conducted at 30 stations in Lake Pontchartrain from October 11-14, 2005, using small trailered boats and at 30 stations in Mississippi Sound from October 9-15, 2005, using small boats staged from EPA’s OSV Bold in Gulfport, Mississippi. A major focus of these surveys was on the collection and analysis of water and sediment samples using standard protocols and core indicators applied in EPA’s Environmental Monitoring and Assessment Program (EMAP) and National Coastal Assessment (NCA) programs. Water analyses included nutrients, chlorophyll a, total suspended solids, carbon, waterborne pathogens (fecal coliforms and enterococci), and chemical contaminants (organochlorine pesticides, PCBs, PAHs, oil and grease, and metals). Sediment was collected from multiple grabs at each site, combined into single station composites, and then sub-sampled for toxicity testing and the analysis of chemical contaminants, microbial/pathogenic indicators, TOC, and grain size. One additional sediment grab (0.04 m2) was collected at each site for analysis of benthic macroinfauna (> 0.5 mm). These data were compared to similar data collected prior to the storm and to environmental evaluation thresholds available in the literature. Dissolved oxygen increased after the hurricane in both Lake Pontchartrain and Mississippi Sound/Lake Borgne due most likely to mixing of the water column from wind and tidal action. Storm-related changes in bottom-water salinity also occurred in both systems though with contrasting patterns. The salinity change was particularly pronounced in Lake Pontchartrain, which shifted from a predominantly oligohaline system prior to the hurricane to predominantly mesohaline after, due possibly to storm surge and the intrusion of more saline water from Lake Borgne and Mississippi Sound. Portions of Mississippi Sound, particularly on the west side, became slightly less saline after the hurricane, due most likely to dilution from runoff and mixing of water from Lake Pontchartrain and Lake Borgne. Total suspended solids (TSS) in the

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