CHANGES IN AND SLOW RECOVERY OF A MEIOBENTHIC NEMATODE ASSEMBLAGE FOLLOWING A HYPOXIC PERIOD IN THE GULLMAR FJORD BASIN, SWEDEN

Meiobenthos samples were collected from Gullmar Fjord, on the Swedish west coast, for just over 2 yr (December 1978-February 1981, inclusive), spanning a short period of severe hypoxia. Previously published analysis indicated no meiofaunal response at the major taxon level. Nematode samples were further analysed to the genus level. Data were analysed with both univariate and multivariate statistics. Although there was no immediate response to the hypoxic period, changes in assemblage structure at both genus and family level during the subsequent year may have been caused by it: diversity was reduced, multivariate assemblage structure was altered, and within-site variability was considerably increased. These changes may have resulted directly from the influence of hypoxia on reproductive success and juvenile survival and/or indirectly as a consequence of the complete disappearance of the macrobenthos (due to the hypoxia) which would alter macrobenthos-meiobenthos interactions. A year after the hypoxia there was no evidence that the nematode assemblage structure was returning to its pre-hypoxia state. This suggests that in physically undisturbed, deep sites, such as the Gullmar Fjord basin, recovery of nematode assemblages after environmental disturbance may be a lengthy process.