Efficacy of Marine Protected Areas for seabird species richness and abundance

Abstract

Seabirds, or birds that are affiliated with the marine environment, are important intertidal predators whose effects due to anthropogenic impacts may reflect the environment in which they inhabit. In this way, seabirds may be considered indicator species, or species that directly signal shifts in the health of their associated ecosystem. Marine lagoons, which support diverse benthic communities, are an example of an ecosystem in which seabirds act as indicator species. Despite the designation of Marine Protected Areas (MPAs) for some lagoons on San Juan Island, WA, the benefits of this strategy for highly mobile species, such as seabirds, must be better understood for the conservation of seabirds. The present study was an observational study designed to test whether seabird species diversity at the MPA, Argyle Lagoon, is greater than that of the unprotected lagoon, Third Lagoon. Similarly, the present study attempted to test whether the species diversity of seabird prey is greater at the protected lagoon relative to the unprotected lagoon. Two counts were performed in the morning and the afternoon at each site, with seabird identification and count being recorded. Sediment samples were also taken at each site once a day, using mesh sieves, and noting observed prey individual and group count. One tailed t-tests were then performed to determine significance of the relationships of seabird and prey diversity against protectiveness. Seabird richness, the number of unique species, and abundance, the number of individuals, was significantly greater at the protected lagoon than at the unprotected lagoon. Prey richness and abundance was similarly increased at the protected lagoon relative to the unprotected lagoon, but the relationship between prey and protectiveness was not significant. While the designation of MPA for Argyle Lagoon may have explained the substantially increased species diversity of both seabird and prey species, a more likely explanation is the continuous inflow of seawater creating a more rich, diverse, and appealing ecosystem for seabirds and associated prey species at Argyle Lagoon compared to Third Lagoon.