MEPS 491:295-301 (2013)  -  DOI: https://doi.org/10.3354/meps10485

ABSTRACT: The presence of ‘ecosystem engineers’ alters the biophysical landscape and can shape associated animal and plant communities within terrestrial, marine and aquatic ecosystems. For instance, in shallow marine ecosystems, reefs formed by filter-feeding bivalves such as oysters provide complex structure, while simultaneously influencing water column properties (e.g. light availability) through suspension feeding. Although it is well supported that both complex structure and light level can influence trophic interactions individually, both factors are highly variable in shallow marine ecosystems and potentially interact to produce non-additive effects. To explore how the multiple influences of an ecosystem engineer affect trophic interactions, we conducted mesocosm experiments with common estuarine species (i.e. Atlantic croaker and grass shrimp, and blue crab and brown shrimp) to test the effects of habitat context (high complexity oyster reefs vs. structureless bottom) and light level on prey survival. Atlantic croaker Micropogonias undulatus predation on grass shrimp Palaemonetes pugio was significantly reduced by the presence of oyster reef structure and was not affected by light level. In contrast, blue crab Callinectes sapidus predation on brown shrimp Farfantepenaeus aztecus was influenced by the interaction of habitat context and light level: the presence of oyster reefs reduced brown shrimp survival rates at high light levels, but increased survival in low light. Therefore, predicting how habitat context influences species interactions requires an understanding of both species composition and light level. The setting and the physical factors altered by ecosystem engineers can influence community structure both individually and collectively, and consequently should be incorporated in predictive models aimed at understanding and enhancing our management of coastal ecosystems.

KEY WORDS: Crassostrea virginica · Predation · Refuge habitat · Indirect effects · Trophic interactions