Influences of Nonrandom Biodiversity Change on Marine Ecosystem Functioning

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Because the diversity of species in an ecosystem is influenced by a variety of factors, it is important to understand both how diversity is altered by these factors and how the resulting changes in diversity influence the transformation and flux of energy and matter in that system. Most research linking diversity and ecosystem-level processes has been terrestrial (97% of studies) and has used random assemblages of species to experimentally assess diversity's influences on ecosystem functioning. While these studies suggest that diversity influences processes such as productivity, nutrient cycling, and energy flow, they fail to evaluate the consequences of nonrandom changes in biodiversity associated with factors such as nutrient availability, consumers, biological invasions, abiotic stressors, local extinction, and habitat loss. This project will evaluate the consequences of nonrandom biodiversity changes by conducting observations and experimental manipulations of intertidal seaweed assemblages to determine the influences of abiotic stress, consumers, and nutrients on diversity. Rocky intertidal seaweeds are an optimal study system for evaluating these effectors of biodiversity change, as previous research has demonstrated dramatic impacts of disturbance, herbivory, and nutrient availability on seaweed diversity. The research will include complementary field and laboratory experiments in the Bodega Marine Reserve and at the Bodega Marine Laboratory on the northern California coast to assess the influences of these nonrandom biodiversity changes on ecosystem-level processes, including primary production (growth and photosynthetic rates) and nutrient cycling (nitrogen uptake rates). The specific objectives of the project are to: (1) Quantify specific changes in seaweed diversity associated with variation in herbivory, nutrient availability, and abiotic stress; (2) Evaluate the influences of herbivore-, nutrient-, and stress-mediated diversity changes on marine ecosystem functioning; and (3) Compare these impacts to the effects of random assemblages of seaweed species selected from the local species pool. Intellectual merit: This research integrates measurements of individual seaweeds' physiological rates and condition, community structure and dynamics, and ecosystem-level processes (primary production, nitrogen immobilization). The factorial manipulations of consumers, nutrients, and stress will help quantify how these factors combine to influence seaweed diversity. Finally, the work will contribute to the small, but growing, body of evidence suggesting that the diversity of organisms in marine ecosystems influences biogeochemical processes in those systems. This project will specifically evaluate a novel aspect of biodiversity-ecosystem function research: the influence of nonrandom diversity changes on key biogeochemical processes in a marine ecosystem. Broader impacts: Biodiversity is changing from local to global scales, and it is essential to understand both the drivers and consequences of these changes to predict and ameliorate their impacts on ecosystem processes. This project will provide crucial information for the conservation and management of marine ecosystems. The study will also provide training and research experience for postdoctoral researchers, graduate students, and undergraduates, including opportunities for minority and under-represented students participating in the summer REU program at Bodega Marine Laboratory (BML). Results will be communicated through the public education program at BML and through outreach.