Species interactions, trophic structure and food web dynamics

Subsidies to other coastal habitats

Kelp wrack stranded on an exposed sandy beach in the Santa Barbara Channel.

The condition and productivity of kelp forests may have profound effects on the structure and function of neighboring ecosystems that rely on subsidies of organic matter to sustain their food webs. Such is the case for exposed sandy beaches in southern California, which make up more than 70% of the mainland shore. The rich intertidal macroinvertebrate communities of beaches in the region depend largely upon external sources of organic matter because relatively little primary production occurs on the beach itself. Giant kelp forests supply large amounts of detrital kelp and other macrophytes (>450 kg m^-1 y^-1) to sandy beaches which serve as an important foundation for the beach food web.

Beachhoppers (Megalorchestia spp.) are major consumers of stranded kelp.

The diversity and abundance of intertidal macroinvertebrates, such as talitrid amphipods and beetles, and of their shorebird predators on sandy beaches in the Santa Barbara region respond positively to subsidies of algal detritus from kelp forests. We are exploring the role of beach consumers in the biological processing of imported drift macrophytes to better understand exchanges among kelp forests and other coastal ecosystems.