River-backwater pond interactions in the lower basin of the Salado River (Buenos Aires, Argentina).

Ann. Limnol. - Int. J. Lim.

2002

Seasonal samples of zooplankton were taken during 1997-1999 at fifteen stations in the Salado River basin, and analysed in order to study the rotifer fauna. Spatio-temporal changes in the rotifer plankton composition were examined in the main channel and its tributaries. The majority of species found are tolerant of a wide range of pH, whereas others prefer neutral to alkaline values. The total rotifer plankton density increased downstream from the headwaters to the middle sector of the river. The associated shallow lakes and tributaries were an important source of species. Variations in density and number of species were shown to be associated with conductivity, and species tolerant of high conductivity conditions were especially prevalent (upper 7,000 (J.S cm -1 ). Rotifer density was influenced by hydrological conditions, which promoted maximum values during low water periods and in the high water condition promoted the incorporation of species from shallow lakes connected with the river during flood events. The species associations found are related to such water parameters as conductivity and nutrient availability and to the presence of ponds and shallow, waterlogged depressions connected in varying extent to the main channel.

Section: Discussionmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Planktonic rotifers of a saline-lowland river : the Salado River (Argentina)

Neschuk

Ann. Limnol. - Int. J. Lim.

2002

“…In the Salado River of the Buenos Aires province, plankton investigations associated with a backwater pond have been carried out in the lower sector (Solari et al, 2002). An input of organisms from the backwater pond (94 ha) was detected in the river, and the zooplankton structure downstream from this lentic environment was similar to that recorded in the pond itself.…”

Section: Introductionmentioning

confidence: 99%

“…In Argentina, zooplankton investigations on saline rivers have been performed in the provinces of Santa Fe (José de Paggi and Paggi, 1998) and Buenos Aires (Modenutti, 1998;Neschuk et al, 2002;Solari et al, 2002). In the first of these studies, a comparison of the zooplankton structure was performed in three environments (two rivers with different salinity and a shallow lake).…”

Section: Introductionmentioning

confidence: 99%

Influence of regional factors on zooplankton structure in a saline lowland river: the Salado River (Buenos Aires province, Argentina)

Neschuk

2008

River Research & Apps

Knowledge of regional factors influencing zooplankton structure in a semiarid river must include both the main channel and any tributaries in order to identify spatial and temporal patterns along with the main factor that affect the zooplankton community. Accordingly, seasonal samples were taken during 1997-1999 at 15 stations in the Salado River basin, where 172 species were identified (53 protozoans, 88 rotifers and 31 crustaceans). Conductivity and temperature optima and tolerances were calculated for the evident taxa. Different assemblages were recognized by cluster analysis, on the basis of their temperature and conductivity preferences. With respect to the zooplankton assemblages, three zones can be distinguished along the longitudinal axis of the basin: (1) the headwaters (the effluent from large saline shallow lakes), (2) the inter-tributaries, and (3) the lower basin and associated shallow lakes. The spatial distribution of the assemblages was a result of the combined action of factors always promoting the dominance of rotifers. The influence of floodplain waters (backwater ponds, waterlogged depressions, flushing lakes) was attenuated progressively downstream, thus producing disadvantages for the crustaceans. The food availability and high nutrient concentrations related to land use in the headwaters favoured the co-dominance of cladocerans and copepods along with the rotifers in that region.

“…In the last decade, there have been some contributions for particular shallow lakes as Lobos (Boltovskoy et al 1990), San Miguel (Gabellone et al 2001, Solari et al 2002a) and San Miguel del Monte (Benítez & Claps 2000, Claps et al 2002. All of these studies emphasised the importance of rotifers and the larval stages of copepods in determining the zooplankton density.…”

Section: Introductionmentioning

confidence: 99%

Zooplankton biomass in an eutrophic shallow lake (Buenos Aires, Argentina): spatio-temporal variations

Ann. Limnol. - Int. J. Lim.

Benítez

2004

Self Cite

in a shallow eutrophic lake (San Miguel del Monte, Argentina). Duplicate samples of zooplankton were obtained from three stations with different limnological characteristics. The density of zooplankton community was dominated by rotifers and small cladocerans related to the trophic status of this shallow lake. The zooplankton biomass showed similar values to other eutrophic shallow lakes. The annual biomass distribution was bimodal (winter and summer peaks). The contribution of crustaceans, mainly copepods, determined the total biomass. The total zooplankton biomass was significantly correlated with chlorophyll «a» in the sampling station located at the deep part of this shallow lake. There were factors and processes promoting changes in the zooplankton biomass, such as food availability, grazing ability, fish predation, eutrophication process with alternation of turbid and clear water periods, and also the addition of organisms from the Salado River during floods.