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UC Davis Natural Reserve System

A pair of Clark’s grebes perform the rushing ceremony, part of the bird’s courtship behavior.

Seaweeds from Bodega Marine Reserve’s rocky intertidal.

 

Matthew Bracken samples seaweeds at Bodega Marine Lab.

Matthew Bracken samples seaweeds at Bodega Marine Lab.

Featured Research - Bodega Marine Reserve

Matthew Bracken
Bodega Marine Lab Postdoctoral Fellow, UC Davis
Susan Williams (BML/EVE)

Functional consequences of realistic biodiversity changes in a marine ecosystem

Conservation biologists are seeking to understand how loss of biodiversity may affect ecosystem functions, such as nutrient flow or productivity. Most of the research linking diversity and ecosystem-level processes uses random assemblages of species to experimentally assess diversity’s influences on ecosystem functions. Our research on nitrogen use by intertidal seaweed communities shows that this approach can yield misleading results.

Conservation biologists are seeking to understand how loss of biodiversity may affect ecosystems functions, such as nutrient flow or productivity. Most of the research linking diversity and ecosystem-level processes is based on experiments with random assemblages of species, yet natural communities are not assembled randomly. Understanding how processes such as eutrophication, herbivory, and stress shape unique assemblages of species is critical to conservation efforts. Our research on intertidal seaweed communities revealed that indeed the ecosystem functions provided by natural assemblages can differ significantly from random ones.

At BMR, we recorded seaweed species diversity in 50 tide pools and replicated naturally-occurring species combinations in the laboratory to compare to random combinations. Based on these combinations, we quantified changes in nitrogen (ammonium) uptake along a realistic diversity gradient. Realistic seaweed assemblages with the highest species diversity took up nitrogen nearly twice as efficiently as those with the least diversity. But when the same experiment was repeated with random combinations of species, we saw no differences in nitrogen uptake as diversity changed (Bracken et al. 2008. Proceedings of the National Academy of Sciences U.S.A., 105 [3], 924928).

Our results emphasize the value of UC Davis reserves in protecting research sites for the investigation of real-world processes and the need for ecologists to keep one foot in the field to ensure that experimental studies are designed based on realistic scenarios.