Anthropogenic Impacts on Marine Subsidies to Coastal Ecosystems

BAJA WORKING GROUP – CLIMATE SCIENCE ALLIANCE

Anthropogenic Impacts on Marine Subsidies to Coastal Ecosystems Jeremy Long (San Diego State University), Rulon Clark (San Diego State University), Sarah Lester (Florida State University), Keith Lombardo (National Park Service), Jesús Sigala-Rodríguez (Universidad Autónoma de Aguascalientes), Ricardo DeSantiago (San Diego State University), Ana Sofia Gomez (San Diego State University)

COASTAL ECOSYSTEMS, LIKE ISLANDS, RECEIVE IMPORTANT NUTRIENTS FROM THE SEA. PHOTO CREDIT: RICARDO DESANTIAGO

Key Takeaways •

Several coastal Baja California ecosystems receive important nutrient subsidies from the sea via seaweed wrack, carrion, and foraging seabirds.

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Some of the best studied global examples of marine subsidies to coastal food webs are the arid islands of Bahía de los Ángeles.

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Human activities, including climate change, invasive species introductions, and aquaculture, have the potential to modify the quantity and quality of these subsidies.

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Few studies have examined the anthropogenic impacts on marine subsidies, especially beyond the introduction of invasive predators to islands.

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What is the focus and area of your research?

Marine subsidies (e.g. seabirds, seaweeds, fish, and marine mammal carcasses) move resources from the sea to islands. These subsidies can completely change coastal food webs. But, human activities threaten to change the quality and quantity of these subsidies. We seek to understand how humans are modifying these subsidies and the consequences of these modifications on recipient coastal zones.

How do you see climate change impacting the focus of your research?

Ecologists agree that climate change is the major stressor threatening natural habitats. Climate change can influence subsidies to coastal ecosystems via changed storm intensity and frequency, shifted distribution and abundance of marine populations, and altered precipitation patterns. For example, shifts between wet and dry years in the Gulf of California can shift the relative importance of seabird and seaweedderived nutrients (1).

What are you most concerned about?

Our group has two major concerns regarding how climate change will affect marine subsidies to coastal ecosystems.

First, previous research suggests that abiotic factors (e.g. precipitation) susceptible to climate change dramatically influence the role of subsidies. Second, climate change is likely to modify the quantity (e.g. amount of baitfish) and quality (e.g. species composition) of marine species which could, in turn, influence the impact of how these species are used as subsidies.

PLANTS FROM SEABIRD-SUBSIDIZED ISLANDS HAVE ISOTOPIC SIGNATURES UNIQUE FROM POPULATIONS THAT DON’T RECEIVE THESE SUBSIDIES. WE ARE USING STABLE ISOTOPES TO EXPLORE IF THE ROLE OF MARINE SUBSIDIES TO THESE ISLANDS HAVE CHANGED OVER TIME. CREDIT: ANA SOFIA GOMEZ

What are the gaps in understanding that need more research?

First, we need to understand the current role of subsidies to coastal ecosystems beyond Bahía de los Ángeles and around Baja California. Second, we need to model how climate change will impact the quantity and quality of subsidies these ecosystems will receive. Third, we need experiments that explore how such changes will impact recipient ecosystems. And fourth, we need to develop and implement standardized protocols that monitor marine subsidies to coastal ecosystems.

PELICANS, SEAGULLS, AND OTHER BIRDS BRING NUTRIENTS FROM THE SEA TO THE COAST ESPECIALLY IN NESTING AREAS. CREDIT: RICARDO DESANTIAGO

References 1. Stapp, P., Polis, G. A., & Sánchez Piñero, F. (1999). Stable isotopes reveal strong marine and El Niño effects on island food webs. Nature, 401(6752), 467–469. https://doi.org/10.1038/46769

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