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vol.71 issue1SEXUAL AND GEOGRAPHIC VARIATION OF COLOR PATTERNS IN LIOLAEMUS TENUIS (SQUAMATA, LIOLAEMINAE)DIVERSITY AND ABUNDANCE OF LITTORAL ZOOPLANKTONIC COMMUNITIES OF PANTANOS DE VILLA WETLAND, LIMA, PERU author indexsubject indexarticles search
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Gayana (Concepción)

Print version ISSN 0717-652XOn-line version ISSN 0717-6538

Abstract

VIGNATTI, Alicia; ECHANIZ, Santiago  and  MARTIN, María C. ZOOPLANKTON OF THREE SHALLOW LAKES OF DIFFERENT SALINITY AND TROPHIC STATE IN THE SEMIARID PAMPEAN REGION (ARGENTINA). Gayana (Concepc.) [online]. 2007, vol.71, n.1, pp.34-48. ISSN 0717-652X.  http://dx.doi.org/10.4067/S0717-65382007000100005.

The Argentine Valley is a dune formation located in the central part of La Pampa Province, in the semiarid central region of Argentina, which habors a group of shallow lakes fed by rainfalls. These lakes share a high degree of eutrophication but differ in their physical and chemical characteristics, specially in their salinity. In order to integrate information on the composition and variation of their zooplankton assemblages, we analyzed monthly samples of three shallow lakes ("lagunas") of different trophic degree and salinity, two of them subsaline and a third one hipo-mesosaline. Both subsaline lakes were turbid, and present cyanobacteria and fishes. Their zooplankton was characterized by a high diversity (32 - 37 species) and abundance, as well as by the dominance of microzooplankton (mainly rotifers). The macrozooplankton of these lakes was represented by small-sized crustacean species, less vulnerable to the feeding interference caused by filamentous cyanobacteria, and whose low filtration efficiency contributes to keep the turbid condition of the water. In spite of its higher salt concentration, the third lake can be characterized as clear. Its zooplankton species richness (13 species) and abundance were lower, and the absence of fish predation allow the dominance of large-sized macrozooplankters (the copepod Boeckella poopoensis Marsh, 1906 and the cladoceran Daphnia menucoensis Paggi, 1996), which are efficient filtrators and whose feeding activity contributes to water clarity. The existence of both zooplankton assemblages is mainly influenced by salinity. The two subsaline lakes shared ten species that were not detected in the more saline lake. Conversely, the latter water body had a zooplankton assemblage that included four halophile species, none of which were registered in the lakes of lower salinity.

Keywords : Boeckella; copepods; Daphnia; nauplii; rotifers.

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