Ecología de ostracodos en medios estuarinos: el Subsistema Carreras (río Guadiana, SO de España)

Abstract

Analyses from 69 samples collected in the Carreras subsystem delimited ten grain size distributions (five in the channel, four in the channel border and one in the salt marsh). The geochemical analysis of some samples shows low pollution in this zone. Four ostracod assemblages were delimitated: a) indigenous estuarine assemblage (Loxoconcha elliptica, Cyprideis torosa, Cytherois fischeri, Elofmnia pusilla and Leptocythere sp.), dominant in all samples, both in biocoenosis and tanathocoenosis; b) coastal assemblage (Urocythereis oblonga, Pontocythere elongata, Aurila convexa and Cytheretta adriatica), with high species well represented in the main channels with marine connection; c) open sea assemblage (Carinocythereis whitei, Palmoconcha guttata and Palmoconcha turbida), with small species very abundant in deeper marine environments (> 10 m deep) of the Huelva littoral; and d) fresh water assemblage (Candona sp., Cyprinotus salinus and Limnocythere inopinata), very minoritary in the silty-muddy tidal flats. The estuarine biocoenosis is composed by euryhaline species, with numerous live individuals in waters with low hydrodynamics and important vegetation. The coastal and, to a lesser extent, the open sea association were introduced during the tidal flux; in addition, these assemblages may be collected in some secondary channels, owing to the erosion of fossil spits.