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Open-File Report 2012–1153

Benthic Community Structure and Composition in Sediment from the Northern Gulf of Mexico Shoreline, Texas to Florida

By Amanda W.J. Demopoulos and Douglas G. Strom

Thumbnail of and link to report PDF (2.4 MB)Abstract

From April 20 through July 15, 2010, approximately 4.93 million barrels of crude oil spilled into the Gulf of Mexico from the British Petroleum Macondo-1 well, representing the largest spill in U.S. waters. Baseline benthic community conditions were assessed from shoreline sediment samples collected from 56 stations within the swash zone (for example, sample depth ranged from 0 to 1.5 feet) along the northern Gulf of Mexico coastline. These sites were selected because they had a high probability of being impacted by the oil. Cores collected at 24 stations contained no sediment infauna. Benthic community metrics varied greatly among the remaining stations. Mississippi stations had the highest mean abundances (38.9 ± 23.9 individuals per 32 square centimeters (cm2); range: 0 to 186), while Texas had the lowest abundances, 4.9 ± 3 individuals per 32 cm2 (range: 0 to 25). Dominant phyla included Annelida, Arthropoda, and Mollusca, but proportional contributions of each group varied by State. Diversity indices Margalef’s richness (d) and Shannon-Wiener diversity (H’) were highest at Louisiana and Mississippi stations (0.4 and 0.4, for both, respectively) and lowest at Texas (values for both indices were 0.1± 0.1). Evenness (J’) was low for all the States, ranging from 0.2 to 0.3, indicating a high degree of patchiness at these sites. Across stations within a State, average similarity ranged from 11.1 percent (Mississippi) to 41.1 percent (Louisiana). Low within-state similarity may be a consequence of differing habitat and physical environment conditions. Results provide necessary baseline information that will facilitate future comparisons with post-spill community metrics.

First posted August 14, 2012

For additional information contact:
Amanda W.J. Demopoulos
U.S. Geological Survey
Southeast Ecological Science Center
7920 NW 71st Street
Gainesville, FL 32653

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Suggested citation:

Demopoulos, A.W.J.,and Strom, D.G., 2012, Benthic community structure and composition in sediment from the northern Gulf of Mexico shoreline, Texas to Florida: U.S. Geological Survey Open-File Report 2012–1153, 15 p., also available at http://pubs.usgs.gov/of/2012/1153.



Contents

Abstract

Introduction

Methods

Results

Conclusions

Acknowledgments

References Cited


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