February 1st to 5th 2016
Olhão, Portugal
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Barrier island restoration following Hurricane Katrina affects habitat quality for oysters in a northern Gulf of Mexico estuary

Oral Presentation
Habitat Loss and Ocean Noise
Friday, February 5, 2016 -
12:00 to 12:15

Park, K. 1 Powers, S.P. 2 Bosarge, G.S. 3 Jung, H.-S. 4

1Texas A&M University at Galveston
21. University of South Alabama 2. Dauphin Island Sea Lab
31. University of South Alabama 2. Dauphin Island Sea Lab
4The Water Institute of the Gulf

Changes in geomorphology of estuaries are common following major perpetuations such as hurricanes and may have profound impacts on coastal ecosystems. Hurricane Katrina in 2005 created a new pass, called Katrina Cut, halving a barrier island, Dauphin Island, in Mobile Bay, USA. Significant decline in oyster population at Cedar Point Reef, the primary oyster harvest grounds, had persisted since then until the Cut was artificially closed in 2010. A bio-physical model for oyster larval transport was used to evaluate two potential mechanisms responsible for oyster population declines: salinity changes in the context of oyster habitat suitability and larval transport changes in the context of larval retention. The model results revealed that the presence of Katrina Cut increased salinity at Cedar Point Reef. During high freshwater discharge, in particular, water exchange through the Cut increased the bottom salinity from < 5 psu to well over 15 (sometimes > 20) psu during the tropic tides. Elevated salinities are associated with greater predation on oysters and higher disease incidence. The presence of the Katrina Cut also reduced larval retention in the spawning area regardless of tidal or river discharge conditions. It was likely due to more dynamic transport conditions owing to the enhanced tidal energy coming in through the Cut, which then resulted in increased westward transport of larvae from the spawning area. Decreases in larval retention at Cedar Point Reef were particularly large for near median river discharge conditions (450-537 cms), which are most frequently occurring conditions in Mobile Bay. Closing the Katrina Cut hence likely improved conditions for oysters within the Bay system and these improved conditions have contributed to increased oyster landings. We believe our results highlight how large scale changes in the marine landscape can alter habitat quality for a key biological component of the ecosystem.
Oyster population, Hurricane Katrina, Recovery, Salinity, Larval retention

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