Micro and mesozooplankton composition during winter in Ushuaia and Golondrina Bays (Beagle Channel, Argentina)

Abstract

The current paper analyses the micro and mesozooplankton in Ushuaia and Golondrina Bays, the first research on these plankton fractions of these areas in wintertime (August 2004). The number of microzooplankton and mesozooplankton taxa was higher in Ushuaia Bay than in Golondrina Bay. Aloricate ciliates predominated over tintinnids in microzooplankton and holoplankton over meroplankton in mesozooplankton in both bays. Ctenocalanus citer, Drepanopus forcipatus and Clausocalanus brevipes presented the highest frequency of occurrence. Among the meroplankton. Halicarcinus planatus and Munida gregaria were the most frequent decapod larvae in both bays. The distribution of the different sampling station groups of microzooplankton and mesozooplankton as determined by cluster analysis suggests the influence of natural conditions in each bay and anthropogenic environmental differences between the two bays.

The current paper analyses the micro and mesozooplankton in Ushuaia and Golondrina Bays, the first research on these plankton fractions of these areas in wintertime (August 2004). The number of microzooplankton and mesozooplankton taxa was higher in Este trabalho analisa 0 micro e o mesozooplancton das Baias Ushuaia e Golondrina, constituindo a primeira pesquisa realizada nessas a'reas sobre estas fracoes do plancton no invemo (agosto 2004). 0 n1'1mero dos taxa do microzooplancton e do mesozooplancton foi mais elevado na Baia Ushuaia do que na Baia Golondrina. Os ciliados aloricados foram dominantes sobre os tintinideos. enquanto que no mesozooplancton o holoplancton foi dominante nas duas baias. Ctenocalamus citer, Drepanopus forcipatus e Clausocalamus brevipes foram as espe'cies mais freqiientes. No meroplancton, Halicamus planatus e Munida gregaria foram as larvas de decapodes mais freqfientes em ambos os locais. Os diferentes grupos de estacoes formados em funcao do microzooplancton e do mesozooplankton, e detectados na analise de agmpamento. sugerem a influéncia de condicoes naturais em cada baia e de diferencas ambientais antropogénicas entre as duas baias.