Meiofaunal responses to sedimentation from an Alaskan spring bloom. II. Harpacticoid population dynamics

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Abstract
As previously reported, metazoan meiofaunal major taxon seasonal variation and density maxima were found to be unrelated to spring phytoplankton sedimentation over a 4 yr period in Auke Bay, Alaska. To determine how individual species responded to sedimentation, meiobenthic copepods were analysed separately and the results discussed here. The harpacticoid copepod assemblage was diverse: 35 species, of which 16 were common and abundant each field season and throughout the bay. Three species, Tachidiella cf. minuta, Danielssenia reducta Gee and Pseudameira sp., dominated collections, comprising about 60% of all individuals. Reproductive cycles in some species appeared to be related to the April-May sedimentation event. Age-structured data indicate marked changes coincident with sedimentation for 2 of the 3 predominant species. In the overwinter species D. reducta and T. cf. minuta, the proportion of copepodites increased in April and May and striking increases in the proportions of males followed in May and June annually. This pattern suggests that a cohort is produced in conjunction with spring sedimentation. Pseudameira sp. reproduced early, before spring sedimentation. Most significantly however, seasonality in population density was not obvious, and although abundances differed among years, density maxima did not co-vary with sedimentation intensity. This suggests that harpacticoid density maxima are not tightly linked with phytodetritus and that other factors regulate abundance.