Psammolittoral marine tardigrada from Coleman Beach, California

Purpose of the Study:\ud Most of what is known about marine tardigrades is based on research conducted in Europe and along the east coast of the United States. Prior to this study only two cursory surveys of marine sand-dwelling taxa had been conducted along the coast of California. In each case a new species was described, but the number of species recovered from any single beach did not exceed three, giving the impression that species diversity along the California coast is unusually low.\ud This study is a survey of the taxonomic composition, intertidal distribution, and temporal variation of marine interstitial tardigrades from Coleman Beach, Sonoma County, California. Procedure:\ud Sand cores were collected on March 23, July 23, and November 3, 1994 at Coleman Beach, Sonoma County, California. These were treated as representative samples for spring, summer, and fall respectively. The cores were taken along an 1 8 meter transect within the upper intertidal area (mean lower low water to mean higher high water) in 3.5cm diameter by 10cm depth (1 OOcm3) sections to a maximum depth of 60cm. Findings:\ud Eight species representing three arthrotardigrade families were encountered. Two of these are new records for the west coast of North America and two others are new to science. In the family, Batillipedidae Batillipes tridentatus were the most abundant in the spring and B. sonomacus n. sp. were most abundant in fall. Halechinischus remanei was the single most common member of the family Halechiniscidae and the most abundant species in summer samples. H. californiensis n. Spa occurred along with its congener in very low abundance. The Halechiniscidae was also reprsented byTanarctus arborspinosus in summer and T. ramazzotti in fall. Stygarctus spinifer and S. bradypus comprised the family Stygarctidae. The halechiniscids and stygarctids typicaly occurred in the deepest (40-60cm) cores at mid to high tide level.\ud Conclusions: The presence of seven different species of tardigrades in the summer samples alone establishes that species diversity along the California coast is as rich as that found elsewhere. The distribution patterns observed during this study conform to the findings in both Europe and the eastern United States. Seasonal variation patterns suggest an alternation in abundance between congeneric species at Coleman Beach and may be the out come of interspecific competition