Intertidal reconnaissance survey to assess composition, distribution, and habitat of marine/estuarine infauna in soft sediments in the Southwest Alaska Network

Lees, Dennis; Driskell, William

Soft sediments on beaches in three parks in the Southwest Alaska Network (SWAN) were examined to provide baseline data on infaunal assemblages, especially bivalves. The surveys were conducted in Kenai Fjords National Park (KEFJ), Lake Clark National Park and Preserve (LACL), and Katmai National Park and Preserve (KATM) were examined using a variety of sampling techniques often employed on soft substrata. These included 1/4-m2 (2.7 ft2) and 1/16-m2 (0.67 ft2) macrobivalve excavations, microbivalve core samples, and visual assessments to assess species composition and distribution of the infauna, especially bivalves used for prey by important predators (esp. brown bears (Ursus arctos), sea otters (Enhydra lutris), diving ducks (e.g., Melanitta spp., Histrionicus histrionicus, and Clangula hyemalis), and shorebirds (e.g., Calidris spp.)), as well as visual evidence of recent predation. Samples were collected at 39 of 56 sites in KEFJ, 9 of 21 sites in LACL, and 13 of the 31 sites in KATM. Soft intertidal habitats in KATM are quite diverse, varying from clean fine sand on the exposed beaches to compact sandy mud in protected areas in Kamishak Bay. Habitats differ substantially within and among the parks. Sediments in KEFJ are dominated by gravel with substantial quantities of sand or silt. In contrast, very few gravel or mixed-soft sediments were observed in KATM although they appeared biologically rich where they occurred. In contrast, habitats in the northern region of KATM, dominated by sand or mud, are quite similar to those observed in LACL but wave exposure in KATM may have created harsher environments. Generally, beaches in KEFJ appear to be considerably younger than those in KATM or LACL. The bivalve faunae differed considerably within and among regions in KATM, but dominant bivalves within the regions also dominated within either KEFJ or LACL. Potential target species common in KATM and KEFJ included butter and softshell clams (Saxidomus giganteus and Mya arenaria), Baltic macomas (Macoma balthica), and foolish mussels (Mytilus trossulus). Potential target species common in KATM and LACL included razor, surf, and softshell clams and Baltic macomas (Siliqua spp., Mactromeris polynyma, Mya spp., and Macoma balthica). Among the three parks surveyed, KATM exhibited the highest diversity in habitats and bivalve assemblages. All parks supported bivalve population that could support a long-term monitoring program and exhibited evidence of predation by major foraging species like brown bears, sea otters, and diving duck.

Intertidal reconnaissance survey to assess composition, distribution, and habitat of marine/estuarine infauna in soft sediments in the Southwest Alaska Network

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