Spatial scales of connectivity in subsidy-dependent coastal ecosystemsBroad-scale Spatial Patterns

Kyle Emery¹, Kyle Cavanaugh², David Hubbard¹, Jenifer Dugan¹, Robert Miller¹

¹University of California, Santa Barbara, USA - ²University of California, Los Angeles, USA

Maintaining ecosystem connectivity is a key factor in the resilience of ecosystems to climate change. Subsidies of material and energy from donor ecosystems can significantly influence the structure and dynamics of recipient communities and food webs. The largest observed cross-ecosystem fluxes are from marine to terrestrial systems, consist of exported primary production, and are driven by currents and tides. An exceptional example is the subsidy of organic matter exported by highly productive nearshore kelp forests to sandy beaches. The wrack subsidies exported from kelp forests to beaches support their biodiversity and numerous ecosystem functions as well as fuel highly productive beach food webs. Kelp wrack inputs to beaches are highly dynamic, but the relative spatial scale at which this connectivity occurs is largely unknown. Here, we utilized a kelp tagging experiment, local (100 m) to regional (100 km) scale measurements of kelp wrack inputs, and nearshore kelp supply derived from satellite estimates of kelp canopy biomass to determine the scale at which connectivity between beaches and kelp forests is maximized. Our results indicated that connectivity is maximized at scales of less than 10 km. Further, these relationships are strongest in winter and weakest in summer. In addition, the form of kelp wrack (fronds vs. whole plants) is an important factor in determining the spatial scale of connectivity with kelp forests. Elucidating the fine-scale variability in ecosystem subsidies will be critical as ecosystem connectivity is weakened through climate change and anthropogenic development.