Human-driven spatial and temporal shift in trophodynamics in the Gulf of Maine, USA

Utilizing marine protected areas (MPAs) to isolate the ecological effects of human influence can help us understand our effect on systems and foster ecosystembased approaches to management. Specifically, examining invertebrate prey community dynamics inside and outside an MPA may provide a measure of how altering human influence (i.e., certain fishing pressures) affects ecosystem interactions. We measured trophic interactions inside and outside a deep-water temperate MPA over 2 years. Predation rates on tethered, preferred groundfish prey (crabs) were initially identical inside and outside the MPA, but decreased outside the MPA after the commercial groundfish fishing season commenced. Predation trials using a ubiquitous prey species (brittle stars) and a less preferred prey species (urchins) served as controls, showing no MPA effect. Our experiments quantify differential predatory activity resulting from differences in human activity driven by an MPA, demonstrating important effects of fishing and regulations on the strength of trophic interactions. Introduction Fishing, even at levels considered sustainable, can affect the structure and function of marine ecosystems (Pauly et al. 1998; Jackson et al. 2001). Biodiversity and species abundance can be altered, either directly (e.g., removal resulting from fishing effort) or indirectly (e.g., through changes in food web linkages). Some systems have even collapsed under intense fishing pressure, which can be further exacerbated when coupled with unfavorable ocean conditions (Steneck and Carlton 2002). Although managers and scientists can mitigate human impacts on ocean ecosystems, our knowledge of how exactly systems are affected by fishing is still fairly rudimentary. In order to better grasp this, and to provide for ecological buffers, conserve biodiversity and protect or help rebuild fisheries to robust population levels, policy makers are implementing various ecosystem-based approaches to management. Along with a handful of other management techniques, marine protected areas (MPAs), including marine reserves, are emerging as important conservation tools that can help enhance the regional abundances of overfished species (Sobel and Dahlgren 2004; Tognelli et al. 2009; Selig and Bruno 2010). Many studies indicate that the establishment of MPAs can influence local ecosystems as a whole by restructuring benthic communities, boosting populations of large predators, and returning system dynamics to at least a perceived natural state (Babcock et al. 1999; Lester et al. 2009). This is achieved primarily by removing or dampening identified human activities that can adversely affect ecosystem dynamics, such as fishing. Understanding these changes in human activity will shed light on how nutrients and energy move through a system and influence overall productivity and provide a greater understanding of the Communicated by P. Kraufvelin. J. J. Meyer (&) J. E. Byers Department of Zoology, University of New Hampshire, Durham, NH, USA e-mail: [email protected] J. E. Byers e-mail: [email protected] Present Address: J. J. Meyer Puget Sound Partnership, Tacoma, WA 98421, USA Present Address: J. E. Byers Odum School of Ecology, University of Georgia, Athens, GA 30602, USA 123 Mar Biol (2011) 158:631–638 DOI 10.1007/s00227-010-1587-1