Seasonal change in the abundance and spatial distribution of a meiobenthic assemblage on the open Oregon coast and its relationship to the diet of O-age flatfishes

Graduation date: 1982The shallow, wave-swept sea floor off the central Oregon coast\ud is used by 0-age flatfishes as a nursery ground. This dissertation\ud is based on a series of projects designed to: 1) identify the dominant\ud meiobenthic nematodes present in a coastal nursery area; 2)\ud describe the important temporal and spatial scales of nematode variability\ud at this site; 3) discuss the role of sediment disturbance in\ud structuring nematode assemblages; and 4) relate seasonal and spatial\ud differences in the distributions of meiobenthos to observed changes\ud in the diet of flatfishes.\ud The 19 numerically dominant nematode species found at the study\ud site showed significant fluctuations in density over a 15 month\ud period, yet their rank order based on abundance did not change. Four\ud mechanisms capable of producing seasonal changes in nematode abundance\ud without altering species proportions are discussed: winnowing from sediments, non-selective predation, seasonally variable food resources,\ud and compensatory links between birth and death rates among species.\ud Significant differences in the abundance of nematodes were found\ud over horizontal distances of kilometers and centimeters. Sediment\ud disturbance contributes to the generation of these spatial patterns.\ud Over broad scales there were two distinct faunal groups associated\ud with different water depths. The division between these assemblages\ud was closely correlated with the threshold depth at which sediments\ud are influenced by passing waves. On small scales (