TEMPORAL AND SPATIAL VARIATION OF DOMINANT PELAGIC COPEPODA (CRUSTACEA) IN THE WEDDELL SEA (SOUTHERN-OCEAN) 1929 TO 1993

The abundances of four dominant Antarctic copepod species, Metridia ge rlachei, Rhincalanus gigas, Calanoides acutus and Calanus propinquus, were examined in the Southern Ocean in a combination of a literature r eview, analysis of museum samples and field sampling. The data were an alysed for spatial and temporal variations. The data included in the a nalysis were from the Weddell Sea area in the summertime at periods 19 29-1939 and 1989-1993. The results are discussed in the light of envir onmental changes and their hypothesised and observed consequences in t he Southern Ocean: global temperature change, ozone deficiency and cas cading trophic interactions. Combining all these hypothetical effects our null hypothesis was that there were no consistent long-term change s in the abundance of dominant pelagic Copepoda. The null hypothesis w as rejected, since several taxons did show statistically significant l ong-term changes in abundance. The changes were not uniform however. T he numbers of adults and juveniles of Calanus propinquus increased sig nificantly between the periods studied. Adult stages of Calanoides acu tus were the only taxon decreasing in abundance, in concert with the c ascading trophic interactions theory. Latitudinally, only Metridia ger lachei showed a significant increase from north to south. Longitudinal ly, the abundances of Calanus propinquus juveniles and both adults and juveniles of Rhincalanus gigas increased from west to east. There wer e no significant variations between day and night samples. Interannual changes were statistically significant in juvenile stages of all the species and in adults of Calanus propinquus. We conclude that no unifo rm and consistent abundance changes could be observed in the pelagic C opepoda of the Weddell Sea that could be connected to major environmen tal changes, expected to affect the whole planktonic ecosystem of the Southern Ocean. Significant changes in some of the species studied sha w that the pelagic ecosystem is not in a steady state, but in addition to interannual changes, there also are major fluctuations extending o ver decades.