Seasonal changes in structure of an Alaskan intertidal meiofaunal assemblage

Abstract

A subarctic, intertidal meiofaunal assemblage in Auke Bay, Alaska, USA, was sampled throughout one year at 3 intertidal heights; mean low water (0 m) and 1 m above and below this level (+1 m, -1 m). Samples were taken twice a month at 0 m and approximately every other month at -1 and +1 m intertidal heights. Nematodes predominated numerically (31 to 77%), followed by harpacticoid copepods (adults and copepodites combined 10 to 35%, nauplii 5 to 32%). Meiofaunal densities fluctuated significantly throughout the sampling period. The demography of the 6 numerically predominant species of copepods was examined. In order of abundance, they were Halectinosoma sp. Amphiascoides dimorphus Lang 1965, Microarthridion cf. littorale Poppe 1881, Apolethon sp., Mesochra sp. and Stenhelia (Stenhelia) peniculata Lang 1965. Densities of the adults, ovigerous females and copepodites of these species changed significantly throughout time. The peak densities of ovigerous females and copepodites were well separated temporally (whereas those of adults overlapped) and tended to occur in months from November to March. Only M. cf. littorale displayed a high abundance of ovigerous females and copepodites in the summer months. Reproductive patterns varied among the harpacticoid species, from discrete (Apolethon sp.) to continuous reproductive periodicity (all other species).