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Influence of habitat complexity in structuring species-specific interactions and trophic linkages on oyster reefs of southeastern North Carolina

UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
Joseph M. Sonnier (Creator)
Institution
The University of North Carolina Wilmington (UNCW )
Web Site: http://library.uncw.edu/
Advisor
Stephen Kinsey

Abstract: Species interactions influencing the strength of trophic linkages play a key role in structuring communities. Although the importance of these interactions has been recognized, currently there are relatively few studies characterizing the role of habitat in moderating these interactions, especially in marine environments. Habitat complexity that provides refuge for some organisms may alter interactions between species with consequences for community composition. Recently created oyster reefs of differing complexity in southeastern North Carolina provide an excellent opportunity to test the hypothesis that increased habitat complexity modifies predator-prey interactions leading to direct and indirect effects in the oyster reef community. The common mud crab, Panopeus herbstii, is an abundant intermediate predator living within oyster reefs feeding on bivalves such as oyster spat, Crassostrea virginica, and ribbed mussels, Geukensia demissa, and is prey for other species such as blue crabs, Callinectes sapidus, and larger fishes. The goal of this study was to determine the direct and indirect effects of oyster complexity on mud crab populations (density, distribution, feeding, and survival) in a field setting and mud crab: bivalve (predator-prey) dynamics in the presence and absence of a top predator, the blue crab in a laboratory setting. Mud crab density was significantly greater in areas of high habitat complexity during both field and lab studies. Tethering trials indicated predation on mud crabs increased as oyster reef complexity decreased with highest predation rates in open sand. However, highest predation on mud crabs occurred in open sand areas along the edge of high complexity reefs compared to sand areas distant from a reef. Laboratory studies indicated mud crab predation on oyster spat and mussels was greater in high complexity oyster patches, but mussels were preferred over oyster spat. The presence of a top predator had differing effects on mud crab predation of oyster spat and ribbed mussels. Predation on oyster spat was reduced in high complexity patches, whereas predation on ribbed mussels was reduced in low complexity patches when blue crabs were present. A potential positive feedback was observed where high complexity oyster habitat provide increased settlement habitat for mussels and mussels provide an alternate, preferred prey source reducing predation pressure on oyster spat. This study demonstrated the multifaceted role of habitat complexity in modifying trophic interaction within a multi-prey system.

Additional Information

Publication
Thesis
A Thesis Submitted to the University of North Carolina at Wilmington in Partial Fulfillment of the Requirement for the Degree of Masters of Science
Language: English
Date: 2009
Keywords
Bivalves--Effect of habitat modification on, Habitat (Ecology)--North Carolina, Mussels--Effect of predation on--North Carolina, Oyster culture--North Carolina, Oysters--Effect of predation on--North Carolina, Predation (Biology)
Subjects
Oyster culture -- North Carolina
Habitat (Ecology) -- North Carolina
Oysters -- Effect of predation on -- North Carolina
Mussels -- Effect of predation on -- North Carolina
Predation (Biology)
Bivalves -- Effect of habitat modification on