Meeting Abstract

9.4  Monday, Jan. 4  Indirect effects of marine protected areas on early community development in the San Juan Islands, WA TURNER, KR*; SEBENS, KP; Univ. of Washington; Univ. of Washington krturner@u.washington.edu

Marine protected areas (MPAs) can be effective tools to aid the recovery of harvested species, but can also influence non-targeted species. In areas where top predators are protected, other species may decrease or increase in abundance due to direct and indirect interactions. To determine the effects of protected predatory fishes on the recruitment of sessile invertebrates, we affixed settlement plates to gently sloping solid bedrock substrate at approximately 21 m depth at two MPAs in the San Juan Islands, WA, known to have increased predator (lingcod, Ophiodon elongatus, and copper rockfish, Sebastes caurinus) abundance, and at two non-protected locations. Predation pressure was manipulated using four treatments: large-mesh cages, small-mesh cages, no cage, and a cage control. These treatments were designed to quantify the influence of different predator size classes on recruiting organisms, and how these effects change in MPAs. The plates were collected after 11 months, and non-metric multidimensional scaling was used to compare recruit communities. Location had the largest effect on community structure, an effect dominated by the abundance and identity of encrusting bryozoans. This clustering may be due to location-specific differences in the benthic community, as larvae of these bryozoans settle within hours of release. However, cage type may explain differences in communities within some of the locations, resulting in differential consumption of foliose red algae on caged and uncaged plates. These results are discussed in the context of trophic webs in the San Juan Islands, how these webs may be affected by MPAs, and our plans for the extension of this research.