Sandy beaches and their surf zones make up a large proportion of the open coast of California and are significant components of many MPAs statewide. The rich and productive food webs of beaches, including invertebrates, fishes and birds, are closely linked to subsidies from rocky reefs and coastal waters. In MPA baseline studies, these subsidies were shown to strongly affect the diversity and abundance of prey resources available for surf zone fish and birds in recipient beach ecosystems. Thus, MPA protection can affect beaches and their surf zones in two ways: directly through harvest of fish, and indirectly through the influence of trophic cascades and other factors influencing the key donor ecosystems of kelp forests and rocky reefs. The strong connections of beaches to rocky habitats, especially kelp forests, are key ecological pathways through which direct and indirect effects of MPA protection can cascade, making sandy beaches and surf zones an important element of long-term monitoring and integrative analyses to assess the performance of MPAs and inform adaptive management of the State’s MPA network.
Our project goals for using beach and surf zone ecosystems to address MPA performance and the evaluation questions and goals of the MLPA are two fold. We will assess indirect effects of MPAs by exploiting the bottom up effects of the ecological connectivity of sandy beaches with kelp forests and rocky reefs thru monitoring the abundance and composition of kelp subsidies and birds. We will assess direct effects of MPAs by surveying the abundance, biomass, size and diversity of surf zone fish, including harvested species. We will monitor: 1) abundance and diversity of birds that forage on sandy beaches and in adjacent surf zones, including shorebirds, seabirds and terrestrial birds 2) population size structure, abundance and diversity of ecologically and culturally important surf zone fishes that could directly respond to MPA protection: including surfperch species, atherinids, flatfish, sharks, and rays, 3) abundance and composition of kelp wrack subsidies cast onto beaches from adjacent intertidal and subtidal ecosystems inside and outside MPAs, and 4) physical characteristics of sandy beaches and adjacent surf zones over time inside and outside MPAs. We will use new and existing datasets to conduct integrated analyses across sites and regions and donor and recipient ecosystems to evaluate MPA performance and inform adaptive management through the lens of sandy beach and surf zone ecosystems.