Beeckman, T.; Caemelbeke, K. (Ed.) (1998). Populations: Natural and manipulated, symposium organized by the Royal Society of Natural Sciences Dodonaea, University of Gent, 29 October 1997. Biologisch Jaarboek (Dodonaea), 65. Koninklijk Natuurwetenschappelijk Genootschap Dodonaea: Gent. 257 pp., more
In the trace of low temperature and sea-ice formation high-latitude-ecosystem components show a strong seasonal variation. Benthic community distribution and characteristics generally mirror the productivity and depositional regime of the ambient environment. The current question arises how does the interstitial fauna behave throughout the Antarctic seasons, and how do the populations react to extreme ecological situations and events typical for the Antarctic ecosystem. Studies of temporal fluctuations of shallow water meiobenthos in temperate and subpolar regions demonstrated that abundance and biomass vary seasonally over the year. Environmental factors that were proposed to structure the meiofaunal patterns included temperature, physico-chemical regime and trophic dynamics of the environment. However, the regulation of abundance within a given site was sometimes poorly understood, despite the predictable trends in the environment. As part of integrated British research programme the metazoan meiofauna and the surrounding sediments were studied forth nightly for an 18-rnonth period to test whether the temporal variability, of the environment was detectable in meiofaunal abundance, biomass and nematode composition. Environmental impact was inferred by analysing sediment features (total organic carbon and nitrogen, sediment texture, chloropigments, dissolved organic carbon), sediment trap data (chlorophyll, phaeopigments, dry mass, ash and AFDM, carbon and nitrogen), and water column variables (temperature, ice-cover, micro and nano Chl-a and respective phaeopigments). Total meiofaunal density fluctuated between 0,7 and 18,8.106 ind.m-2 and total biomass between 0,2 and 13,3 9 dwt m-2. Ear1y winter (May-June) records of total density and biomass in the first year were very high and distinct from other seasons. They declined sharply to a minimum in the middle of the ice-covered period. During the second year seasonality was less pronounced. Individual taxa varied in different ways. The major response mechanisms of the meiofauna to the environment were: 1) distinct peak abundances, lagging with a few weeks behind peak diatom production 2) lower, though still highly fluctuating figures during most of the year with immediate and lagged responses to lower quality nanoplankton input 3) strong reduced stocks with a short duration in mid winter, when food availability was at its lowest. Only four nematode genera -Daptonema (Gonionichus), Aponema, Neochromadora and Sabatieria proved to be highly abundant. The dominance structure prevailed during the entire time transect. 51% of all nematodes were epistrate feeders (probably feeding on diatoms) and 47% deposit feeders (probably feeding on a mixture of detrital sources). The rest were omnivores. No clear seasonal trend was discernable, as within short periods (- weeks) single trophic categories augmented to episodic peaks irrespective of season. Downloading the temporal investigation to life stage/sex investigations revealed that all categories (juveniles, gravid and non-gravid females, males) were encountered throughout the year with a slight dominance of gravid females (specimens with eggs in the uterus) in August and November, followed by maxima in juvenile densities during September and December. The study emphasizes that meiofauna stock is profoundly influenced by the temporal patterns of the primary production, and this as result of the seasonal varying ice-cover.
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