Document: GAR-3-15-4

Effects of ocean to land trophic interconnections on the dynamics and stability of populations and food webs.

POLIS, G.A.* ¹, P.STAPP ^1,2 and M.D.ROSE ¹

University of California at Davis, Davis, CA 95616 USA ¹
University of York, York, UK, YO10 5YW ²

Abstract:
We have long recognized that lakes, streams, and other freshwater systems are deeply influenced by their terrestrial watershed. Likewise, oceanographers know well how 'terriginous input' affects marine primary and secondary productivity at the land-sea interface. Here, we assess the diverse and often substantial influence of marine input (MI) on the structure and dynamics of populations, communities, and food webs in coastal and island ecosystems worldwide. MI enters terrestrial systems via four conduits: shore drift of algae and carrion, marine vertebrates (turtle, birds, mammals) that come to land, marine aerosols, and consumers that forage in the intertidal. The first-level effects of MI are increased consumer abundance or elevated ANPP from seabird guano or aerosols. Less obvious effects include changes in consumer-resource and food web dynamics. For example, depending on consumer preference, consumers subsidized by MI often depress in situ resources, sometimes initiating trophic cascades. Moreover, both theory and our data suggest that food web structure (nutrients, "multi-channel" omnivory, spatial subsidies) can greatly influence the stability of populations and ecosystem function. For example, MI appears to stabilize consumer populations on small islands and around seabird colonies and the coast. Small amounts of allochthonous nutrients via guano stabilize ANPP and herbivore dynamics whereas large inputs destabilize. The overall importance of MI to land systems is potentially great because a large area (594,000 km of coastline, ~8% of the Earth's surface) is juxtaposed to the sea. This major ecosystem, the coastal ecotone, contains a disproportionate share of biodiversity and productivity but is threatened by the ~65% of the human population that lives along the coast.

Keywords: food web structure, allochthonous marine input, stability, ecosystem function, coastal ecotones

This abstract is being presented at: 10:30 AM in session:
Symposium # 3: Linking Communities Across Ecosystem Boundaries: A Symposium in Memory of Gary A. Polis.