Multivariate analysis applied to total and living fauna: seasonal ecology of recent benthic Ostracoda off the North Cádiz Gulf coast (southwestern Spain)

Abstract

Q-mode principal component analyses of ostracode percentages from 55 samples collected in summer and winter in the Huelva littoral zone (southwestern Spain) delimited four total associations and five living associations. Urocythereis oblonga, Palmoconcha guttata, Pontocythere elongata and Loxoconcha elliptica associations are represented both in the total and in the biocoenosis distributions. An additional biocoenosis association is characterized by Neocytherideis subulata and Callistocythere rastrifera, two minor species in the total distribution. Salinity differentiates the euryhaline Loxoconcha elliptica association (29–36%.) and four marine associations (> 34%.) Under marine conditions, grain size is the main factor delimiting the ostracod fauna, with the Urocythereis oblonga association living 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 sediments, whereas the Pontocythere elongata association inhabits all types of substrate. In the estuary of the Tinto and Odiel rivers, one of the most polluted zones of Europe, study of the seasonal distribution of ostracodes and comparison with previous reports indicate some recuperation in this degraded system. Such species as Loxoconcha elliptica, Leptocythere tenera, or Cytherois fischeri, common in other Atlantic estuaries, are found. In some channel areas, however, the combined effects of metal pollution, medium-grain sand, dredging and strong bottom drift may cause the disappearance of living specimens in some sectors, both in summer and winter.