MULTIVARIATE-ANALYSIS APPLIED TO TOTAL AND LIVING FAUNA - SEASONAL ECOLOGY OF RECENT BENTHIC OSTRACODA OFF THE NORTH CADIZ GULF-COAST (SOUTHWESTERN SPAIN)

e-mode principal component analyses of ostracode percentages from 55 s amples collected in summer and winter in the Huelva littoral zone (sou thwestern Spain) delimited four total associations and five living ass ociations; Urocythereis oblonga, Palmoconcha guttata, Pontocythere elo ngata and Loxoconcha elliptica associations are represented both in th e total and in the biocoenosis distributions. An additional biocoenosi s association is characterized by Neocytherideis subulata and Callisto cythere rastrifera, two minor species in the total distribution. Salin ity differentiates the euryhaline Loxoconcha elliptica association (29 -35 parts per thousand) and four marine associations (>34 parts per th ousand). Under marine conditions, grain size is the main factor delimi ting the ostracod fauna, with the Urocythereis oblonga association liv ing in coarser sandy sediments and the Palmoconcha guttata association being widely distributed in silty sands. The Neocytherideis subulata- Callistocythere rastrifera association prefer very fine sandy sediment s, whereas the Pontocythere elongata association inhabits all types of substrate. In the estuary of the Tinto and Odiel rivers, one of the m ost polluted zones of Europe, study of the seasonal distribution of os tracodes and comparison with previous reports indicate some recuperati on in this degraded system. Such species as Loxoconcha elliptica, Lept ocythere tenera, or Cytherois fischeri, common in other Atlantic estua ries, are found. In some channel areas, however, the combined effects of metal pollution, medium-grain sand, dredging and strong bottom drif t may cause the disappearance of living specimens in some sectors, bot h in summer and winter.