Zooplankton assemblages from a tidal channel in the Bahía Blanca Estuary, Argentina

Abstract

In this study we investigate for the first time the zooplankton assemblages in a relatively small tidal channel called Bahía del Medio, situated in the middle-outer area of the Bahía Blanca Estuary, South of the Main channel. We focused the study on micro- and mesozooplankton assemblages with emphasis on tintinnids, copepods and meroplankton along the annual cycle 1997-1998. Fifteen species of tintinnids belonging to 6 genera were observed in the study area, the mean total tintinnid abundance fluctuating between 3.4 x 10(6) ind. m-3 and 5.1 x 10(6) ind m-3. The mesozooplankton comprised 11 taxa, total abundance fluctuating between 449 ind m-3 in March 1997 and only 1 ind m-3 in October 1997. The channel proved to be spatially homogeneous in its physical and biochemical features. Micro- and mesozooplankton abundance displayed a high degree of spatial homogeneity, though the seasonal variation in both environment and zooplankton was significant. Comparison with the zooplankton observed at a station in the Main channel of the estuary showed differences in number of taxa represented, a general lower abundance of both assemblages and the presence of some rare species, a fact which is discussed.<br>Neste estudo pesquisamos pela primeira vez as associações do zooplâncton num pequeno canal de maré, relativamente novo e chamado Bahía del Medio, localizado na região média-exterior do estuário da Bahía Blanca e ao sul do canal principal. Focalizamos o estudo no micro- e mesozooplâncton com ênfase nos grupos Tintinnida, Copepoda e meroplâncton, ao longo do ciclo anual 1997-1998. Foram observadas 15 espécies de Tintinnida pertencentes a 6 gêneros; a abundância média total de Tintinnida variou entre 3,4 x 10(6) ind. m-3 e 5,1 x 10(6) ind. m-3. O mesozooplâncton apresentou 11 taxa e uma abundância total entre 449 ind. m-3 em março de1997 e 1 ind. m-3 em outubro de 1997. O canal provou ser espacialmente homogêneo em suas características biológicas, químicas e físicas. A abundância do micro- e mesozooplâncton mostrou um alto grau de homogeneidade espacial, embora a variaçao estacional fosse significativa nas características do meio ambiente e do zooplâncton. A comparação com o zooplâncton observado em uma estação de amostragem no canal principal do estuário mostrou diferenças no número de taxa, na abundância, em geral mais baixa, e na presença de algumas espécies raras , fato esse comentado

Monstrilloida (Crustacea: Copepoda) from the Beagle Channel, South America

“…In the Americas there are few records of Monstrilloida from high latitudes of the Southern hemisphere (i.e. Ramírez, 1971;Marín and Antezana, 1985;Dias, 2005;Suárez-Morales et al, 2006;Dias and Bonecker, 2007a, b;Biancalana et al, 2007;Hoffmeyer and Barría de Cao, 2007), and only two species have been hitherto reported from Subantarctic waters (Razouls, 1996).…”

“…In Bahia Blanca, Argentina, at the same general latitude range (42°S), records include Monstrilla sp., M. helgolandica, and M. aff. serricornis (Hoffmeyer and Barría de Cao, 2007). It is not explicitly stated if the latter records are from females or males, but it is probable that the females were identifi ed as M. helgolandica following Ramírez (1971) and the males as M. aff.…”

Distribution of Ciliates in Relation to Environmental Parameters in two Gulfs of Kapıdağ Peninsula (the Sea of Marmara)

“…In addition, a negative correlation between the number of individuals and salinity was determined (p < 0.05). Other studies have reported that tintinnid species and number of individuals have a negative correlation with salinity (Capriulo and Carpenter, 1983;Kamiyama and Tsujino, 1996;Hoffmeyer and Cao, 2007;Lee and Kim, 2010). Durmus and Balkis (2014) found similar results in their study carried out in the southeast of the Sea of Marmara, and also stated that DO is positively correlated with the number of species and individuals.…”

Eutrophication disrupts summer trophic links in an estuarine microbial food web

“…Both sites are located within tidal channels ranging 50-300 m width and 4-7 m depth. The first experiment was performed at Bahía del Medio (BM), which is not directly impacted by human stress (Baldini et al 1999, Hoffmeyer andBarría de Cao 2007), while the second experiment was conducted in Canal Vieja (CV), a site directly affected by cultural eutrophication since it receives point-source untreated domestic effluent from the adjacent Bahía Blanca city (300,000 inhab.). The experiments were daily-deployed on March 6, 2012, to match the seasonal pulse of microzooplankton (Barría de Cao et al 2011) and the first annual phytoplankton bloom (Guinder et al 2013).…”