Marine Protected Areas (MPAs) are a critical tool for conservation and management of economically, socially, and ecologically valuable species in California. The positive effects of MPAs on the biodiversity and abundance of targeted (fished) species are well-described.
The objective of this research was to consider whether MPAs can also promote ecosystem resilience in the face of global climate change. Many commercially important species are at risk due to changing ocean conditions including acidification and hypoxia. This project will examine the potential for MPAs to serve as climate change refuges to economically important species via persistence of kelp forests that mediate the physical and chemical environment.
Giant kelp specifically tends to persist at higher levels in MPAs in Southern California. This is a trickle-down effect of the protected status: more predatory species like spiny lobster and sheepshead survive, which means there are fewer urchins, which feed on kelp. All that seaweed means that water flows through the MPAs more slowly. The presence of the kelp then alters the chemistry of the water through photosynthesis — which is a kind of antidote to the expected impacts of climate change. Photosynthesis consumes carbon dioxide, which lowers the water’s acidity, and releases oxygen.
The team used existing satellite imagery to estimate the amount of giant kelp growing across Southern California and other existing data to quantify the impact of this kelp on local biogechemistry. Then, through laboratory studies, they examined how the observed physical and chemical changes were likely to impact the relationship between lobsters, urchin and kelp. While results have not yet been published addressing the full hypothesis, the research has resulted in the publication of several papers on the food webs involving lobsters, urchins and kelp, including the impacts of warmer waters. The team has been meeting with the California Department of Fisheries and Wildlife, suggesting that creating a “slot fishery” for spiny lobster — narrowing the range of sizes that can be harvested — would allow large lobsters to persist, and consume more urchins.