Climate controls biotic community composition at multiple spatiotemporal scales through variability in environmental control mechanisms (assembly filters). This research investigated the role of climate variability in the community dynamics of estuarine nekton in Breton Sound estuary, Louisiana, and, specifically the effects of El Niño Southern Oscillation (ENSO), freshwater discharge, and a tropical cyclone. A teleconnection was found between ENSO and juvenile brown shrimp (<i>Farfantepenaeus aztecus</i>) abundance in Breton Sound from 1988 2007. ENSO affected winter weather conditions (air pressure, temperature and precipitation), and spring brown shrimp abundance in Breton Sound. Juvenile brown shrimp abundance lagged ENSO by three months; below-average abundance of juvenile brown shrimp was caught in springs following El Niño winters while above-average abundance of brown shrimp was caught in springs following La Niña winters. Salinity was the dominant ENSO-forced assembly filter that regulated brown shrimp abundance. Study of short-term freshwater pulses revealed higher nekton density and biomass in marshes receiving pulsed riverine flow (inflow) than in reference marshes, due to differences in water depth and flooding duration caused by the pulses. Communities consisted mainly of marsh resident species; individual-species examination revealed habitat preference related to water depth. Inflow marshes were capable of producing optimum growth of <i>Gambusia affinis</i> (0.001 g DW
d<sup>-1</sup>) and energetically valuable habitat (> 6,000 cal g<sup>-1</sup>) for trophic transport. Riverine pulses may enhance secondary productivity in Breton Sound estuary. Breton Sound was directly hit by Hurricane Katrina in 2005, causing extreme physical habitat damage and a protracted period of elevated salinity in tidal freshwater marshes. Results included higher nekton densities and a nekton community shift from one dominated by Tidal freshwater / Resident (T/R) species toward one that included Brackish / Migrant species. Effects were short lived; by spring 2007, the nekton community had returned to T/R species, despite the lasting loss of vegetated marsh habitat. These findings provide greater understanding of large-scale climate effects on local estuarine nekton community dynamics and productivity.
| Identifer | oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-04132009-091738 |
| Date | 15 April 2009 |
| Creators | Piazza, Bryan Patrick |
| Contributors | Harris H. Wong, Barry D. Keim, Lawrence P. Rozas, Megan K. La Peyre, Kenneth A. Rose, Jaye E. Cable |
| Publisher | LSU |
| Source Sets | Louisiana State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lsu.edu/docs/available/etd-04132009-091738/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached herein a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to LSU or its agents the non-exclusive license to archive and make accessible, under the conditions specified below and in appropriate University policies, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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