Skip to main content
U.S. flag

An official website of the United States government

Gulf Watch Alaska Nearshore Component: Intertidal Soft-Sediment Invertebrates from Prince William Sound, Katmai National Park and Preserve, and Kenai Fjords National Park, 2007-2015

December 6, 2019

These data are part of the Gulf Watch Alaska (GWA) long term monitoring program, nearshore monitoring component. The data consists of species identification, counts, and size measurements from intertidal soft-sediment sampling sites. Observers excavated, identified, and measured invertebrates from soft sediment sites. Sites are in Alaska and include locations in Katmai National Park and Preserve, Kenai Fjords National Park and Prince William Sound. There are five sites in each of those three regions. The time interval includes 2007-2015. Intertidal invertebrates on gravel and mixed sand-gravel beaches are important components of nearshore zone in the Gulf of Alaska (GOA). These habitats comprise approximately 25% of the intertidal zone in the GOA and are a rich source of invertebrate production that includes clams, snails, polychaete worms, and small crustaceans. These in turn are a primary food sources for a variety of vertebrate and invertebrate predators such as sea stars, sea otters, and subsistence users. Intertidal soft-sediment communities are particularly vulnerable to both natural and human-induced disturbance, and in the GOA communities in the gravel, mixed-sand gravel habitat have been particularly vulnerable to earthquakes, hydrocarbon contamination from the Exxon Valdez oil spill, and changes in sediment composition as a result of spill related clean-up activity. The intertidal community on gravel and mixed sand-gravel beaches in GOA is comprised primarily of infaunal species that live under the surface, but in the upper several centimeters of sediments. Numerically dominant taxa include bivalves (Mysella tumida, Protothaca staminea, Macoma spp.) small gastropods (Cingula sp., Fartulum sp., Alvinia compacta), crustaceans (Amphitoe sp. and Cumella vulgaris), and polychaetes (Pholoe minuta and Pectinaria granulata). Mussels (Mytilus trossulus) can also be locally abundant. The community is spatially variable and species composition and relative abundance is dependent on a variety of factors, the most important of which are sediment grain size distributions, fresh water input, and degree of disturbance by waves. Eelgrass (Zostera marina) in common at soft sediment sites in the lower intertidal and often extends into the subtidal zone. Species of particular importance are the larger clams (Protothaca staminea, Clinocardium spp., and Macoma spp.) that are often the dominant organisms in terms of biomass and are critical prey for larger predators including sea otters. In addition, Protothaca are harvested by subsistence users and are of commercial importance in a growing mariculture industry.