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EFFECTS OF HURRICANE KATRINA ON BENTHIC MACROINVERTEBRATE COMMUNITIES ALONG THE NORTHERN GULF OF MEXICO COAST
Citation:
ENGLE, V. D., J. L. HYLAND, AND C. COOKSEY. EFFECTS OF HURRICANE KATRINA ON BENTHIC MACROINVERTEBRATE COMMUNITIES ALONG THE NORTHERN GULF OF MEXICO COAST. ENVIRONMENTAL MONITORING AND ASSESSMENT. Springer, New York, NY, 150(1-4):193-209, (2009).
Impact/Purpose:
To assess potential effects on benthic fauna and habitat quality in coastal waters of Louisiana, Mississippi, and Alabama following Hurricane Katrina.
Description:
A study was initiated in fall 2005 to assess potential effects on benthic fauna and habitat quality in coastal waters of Louisiana, Mississippi, and Alabama following Hurricane Katrina, which struck the coast of Louisiana, between New Orleans and Bioloxi, Mississippi on August 29, 2005. Sampmles for analysis of macroinfauna (>0.5 mm sieve size), chemical contamination of sediments (metals, pesticides, PAHs, PCBs), and other general habitat characteristics (salinity, dissolved oxygen pH, depth, nutrients, chlorophyll, suspended solids, sediment organic carbon, sediment granulometry) were collected at 30 sites in Lake Pontchartrain, Louisiana (October 11-14, 2005) and at 30 sites in teh more open waters of Mississippi Sound (October 9-15, 2005) from Dauphin Island, Alabama to the western side of Lake Borgne, Louisiana. 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, as part of EPA's National Coastal Assessment (NCA) program. There were notable changes in seeral benthic community characteristics between pre- and post-hurricane periods that suggest storm-related effects in both coastal systems. These included shifts in the composition and ranking of dominant taxa and reductions in number of taxa, H difersity, and total faunal abundance. A benthic condition index, developed for use in Gulf of Mexico estuaries, in general did not reveal such effects, though there was a slight decline in the percentage of Lake Pontchartrain waters with healthy benthic assemblages after the hurricane in comparison to average pre-hurricane periods. Any potential storm-related effects on the benthos did not appear to be linked to chemical contamination, organic enrichment of sediments, or hypoxia. While increased mobilization of contaminants may have contributed to localized effects, storm-related changes in salinity were a more likely cause of the observed benthic changes in both survey areas. 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 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, becamse slightly less aline after the hurricane, due most likely to dilution from runoff and mixing of water from Lake Pontchartrain and Lake Borgne. Storm-niduced scouring of sediments could have contributed to these effects as well.