Assessment of Benthic Habitats and Communities in Areas Targeted for Offshore Wave Energy Development

While the coastal waters of western North America hold great potential for offshore renewable energy development, concerns have been raised about the effects to benthic habitat and organisms by the installation of devices and complex mooring systems. However, little is known about natural species-habitat relationships and community processes in depths and substrate types targeted by wave energy developers relative to other regions. This study surveyed benthic habitats from northern California to Washington State using a variety of techniques, providing baseline data on habitats and species potentially affected by offshore renewable energy development and identifying species-habitat relationships. The overarching objective of this project is to develop predictive capabilities of where benthic invertebrate species of interest and unique communities may occur to inform decision-making regarding siting of facilities in areas where comprehensive surveys have not been conducted.

In summer 2011 sites were mapped using high-resolution multibeam sonar and acoustic backscatter. Following mapping, sedimentary habitats within six study sites were sampled with a 0.1 m² box core to collect infaunal invertebrates and sediment samples for community characterization and ground-truthing of backscatter results as well as organics analysis. Additional shipek grabs of sediment were taken to supplement ground-truthing. At each box core sampling station, CTD casts were conducted to obtain physical data of the overlying water column for further habitat characterization. Throughout the study region, sites varied significantly in physical characteristics of the sediment and water as well as in the benthic invertebrate assemblages found at the sites. Significant differences in assemblages were observed between sandy and silty habitats; within slit/clay sediments breaks in species assemblages were observed at 90 – 100 m depth. Relationships between physical factors and species distributions and correlations with overall diversity will be presented.