Project: Context-Dependency of Marine Biodiversity-Ecosystem Function Relationships

Description from NSF award abstract:
Because species mediate key biogeochemical processes and play unique ecological roles, changes in the diversity and composition of species in an ecosystem can alter how that system functions. A growing body of work has demonstrated that changes in biodiversity can have profound effects on the functioning of marine ecosystems. However, key unresolved issues remain with respect to relationships between marine biodiversity and ecosystem functioning. In particular, few studies have evaluated interactions between producer diversity and herbivore diversity, especially in the field. Furthermore, the vast majority of experiments have evaluated the consequences of biodiversity changes at only one location, so there is very little knowledge of how diversity-function relationships are modified by environmental context. This study will examine, in the field, how environmental context shapes marine diversity-function relationships and particularly the interaction between changes in consumer and producer diversity in intertidal ecosystems at three sites spanning 500 km of the New England coastline. These factorial experiments will manipulate seaweed and grazer diversity at East Point, Massachusetts; Chamberlain Point, Maine; and Quoddy Head, Maine. The research asks the following questions:
1) How does seaweed diversity influence key marine ecosystem processes such as primary and secondary productivity?
2) How does herbivore diversity affect the top-down impacts of molluscan grazers on intertidal seaweed assemblages?
3) What are the feedbacks between grazer and seaweed diversity in driving intertidal community and ecosystem structure and function? And
4) How does environmental context modify the top-down and bottom-up effects of biodiversity change on intertidal ecosystem functioning?

This study will make important intellectual contributions to marine ecology by considering feedbacks between diversity change at two adjacent trophic levels. The work will be conducted at multiple sites which span a range of nearshore oceanographic and climatic conditions, enhancing the generality of the work and allowing for evaluation of the effects of environmental context on diversity-function relationships. Biodiversity is changing at all scales, from local to global, and it is essential to understand the consequences of these changes in order to better predict and ameliorate their impacts on communities and ecosystems. This research will provide a more holistic understanding of the links between diversity, trophic interactions and ecosystem function that will facilitate more effective conservation and management strategies in marine, as well as other, ecosystems. It will provide training and research experience for students at all educational levels. The investigators will involve graduate and undergraduate students in all phases of the research and will also offer a summer research internship each year to a high school student from the Coastal Ocean Science Academy (COSA) that is taught by the Northeastern University Marine Science Center's Outreach staff. COSA students are primarily from under-represented groups in the greater Boston area. Finally, the results of the research will be communicated to the public through the outreach and public education program at the Center.

Publications produced as a result of this research:
Bracken, M.E.S. and N.H.N. Low. 2012. Realistic losses of rare species disproportionately impact higher trophic levels. Ecology Letters, 15, 461-467. doi:10.1111/j.1461-0248.2012.01758.x