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Oyster reefs provide valuable ecosystem services including nutrient cycling, buffering storm surge, and serving as a food source and habitat. As a part of a Duke University Bass Connections team, our group of undergraduate, law, and graduate students are working to develop methods to better assess oyster reef health. Through our work, we hope to determine whether drone and audio analysis can be used as a non-invasive proxy by which to measure reef health and track changes in the community over time. In order to assess this, we have to establish a baseline of reef health. We chose to use reef biodiversity as our reef health measurement. Knowing how many species and individuals are on a reef is interesting purely from a basic science perspective, it may not be initially obvious why biodiversity is an important measure of reef health.
Oyster reefs provide complex structures to the ocean floor, which form small crevices that support invertebrates, algae, and juvenile fish species. A healthy reef can support hundreds of species. Each new species that settles on the reef increases its biodiversity, as biodiversity is influenced by species richness as well as evenness.
Biodiversity is not important just because we like to see diverse communities. Species that use the reef as a habitat can provide additional ecosystem services. For example, oysters filter the water and uptake nutrients like nitrogen, which can protect coastal waters from suffering algal blooms. There are other organisms on the reef that can provide additional filtering abilities. Reefs attract sponges and other filter feeding organisms that remove heavy metals and pollutants (Miller 2002). In one day, sponges can filter the entire water column up to 15 meters deep (Miller 2002). If the reefs studied in Miller (2002) lacked these sponges, their potential to filter the water would be significantly decreased. There are ecosystem services provided by reef inhabitants outside of just filtering water. Algae and other photosynthetic organisms that settle on the oysters increase the habitat’s primary productivity and act as a food source for other species in the community. As reefs support more species, the reefs as a community will be able to provide additional ecosystem services for the water and habitat around the reef.
Without a diverse community of reef dwelling species, a reef may not reach its full potential as an ecosystem service provider. This is why groups like NOAA have made it a priority to restore oyster reefs to bring back biodiverse ecosystems. When we assess biodiversity in our study through limited invasive oyster surveys and invertebrate identification, we could be indirectly measuring the ability of that oyster reef to support other species, which can help indicate the health of the reef. Then, we can use these baselines to develop non-invasive proxies to study reef health and composition through audio and drone surveys.
Post by Melissa Baldino, Biodiversity team
References:
Miller, M. W.2002. Using ecological processes to advance artificial reef goals. – ICES Journal of Marine Science, 59: S27–S31.
