Comparative ecological analysis of the ostracod faunas from low- and high-polluted southwestern Spanish estuaries: a multivariate approach

The distribution and abundance of both living and total ostracod population s from the estuaries of the southwestern Spanish coast are discussed. A tot al of 68 species were obtained from 120 bottom samples collected in the cha nnels, channel margins and salt marshes. Four assemblages were recognized i n this area: (a) Urocythereis oblonga assemblage, with marine species well- represented in sandy substrates located near the mouths; (b) Loxoconcha rho mboidea assemblage, mainly developed in the quiet tidal channels conected w ith the. main channels of the marine domains; (c) Loxoconcha elliptica asse mblage, enclosing the most cosmopolitan and euryhaline species, very abunda nt in muddy sediments and low to moderate hydrodynamic conditions; and (d) Leptocythere porcellanea assemblage, only observed in the clayey-silty chan nel margins of the most protected ebb channels. In these transitional environments, very unfavorable conditions for the ost racod development were found in: (a) the erosional channels and channel mar gins; (b) most of the salt marsh samples with high subaerial exposure; and (c) sectors with high metallic pollution levels and acidic waters. (C) 2000 Elsevier Science B.V. All rights reserved.