Assessing Red Sea Urchin Spine Canopy Microhabitat for Juvenile Abalone and Other Gastropods: Measuring Marine Ecosystem Health

Dr. Laura Rogers-Bennett, UC Bodega Marine Laboratory

$38,157

Measures of ecosystem “health” require defining key ecosystem features. Here we define health for nearshore rocky reefs as habitats that support positive species interactions enabling the persistence of northern abalone (Haliotis kamtschatkana). We propose this definition for four reasons (1) stocks of northern abalone have fallen to dangerously low levels (potentially below persistence levels), (2) abalone densities continue to fall despite fishery closure suggesting other management or restoration measures are needed, (3) the spine canopy provided by red sea urchins (Strongylocentrotus franciscanus) may be critical microhabitat for juvenile northern abalone, and (4) northern abalone are an integral part of the nearshore ecosystem and the cultural heritage of the San Juan Islands.

We will address whether the red sea urchin fishery may indirectly impact juvenile northern abalone abundance due to the removal of an ecosystem engineer. Ecosystem engineers are species that provide structure within the habitat (e.g. corals and kelp) altering resource availability to other species and thus their removal may have negative consequences for species diversity. We propose to assess patterns of faunal abundance, microhabitat utilization and species associations by the rare northern abalone and abalone surrogates to examine the relative importance of positive species interactions within marine communities of the San Juan Islands. Abundances, sizes and microhabitat distribution will be assessed to quantify the relationship between juvenile abalone and other mollusks with and without the biogenic structure provided by the spine canopy of red sea urchins.

A combination of field and laboratory experiments will be used to discern the relative importance of the red sea urchin spine canopy as microhabitat. Field data collected in cooperation with WDFW will be analyzed to discern patterns of associations between biological (species) and physical variables in habitats with and without red sea urchin fishing. Biological samples taken from microhabitats with and without urchins will be analyzed. We will address the question, “Do management measures such as upper size limits in the sea urchin fishery protect sea urchin spine canopy microhabitat.” In the laboratory, we will assess survival and feeding of hatchery reared juvenile abalone in a variety of microhabitat treatments including with and without sea urchin spine canopy. We will develop an index of ecological health based on physical and biological features that promote juvenile abalone productivity, develop community diversity as well as compare patterns of species rarity between habitat types. Identifying positive species interactions within marine communities can aid in the goals of (1) establishing ecosystem-based management and (2) recovering species in decline.