Seasonal variation in the phytoplankton of a saline lowland river (Buenos Aires, Argentina) throughout an intensive sampling period

Abstract

The aim of this survey was to analyse seasonal variations in phytoplankton composition and abundance with respect to temperature and conductivity values at two sampling sites in the Salado River's lower basin: El Destino and Guerrero. Samples were taken twice a week from 9 March 2004 to 20 July 2004. A total of 145 and 143 species were identified for these two sites, respectively. Infrequent species were discarded to avoid statistical misinterpretations. Autocorrelation analyses (Ljung-Box Qstatistic) were performed in order to establish seasonal patterns for species abundance. Similar significant ( p < 0.05) autocorrelation patterns were observed for phytoplankton species composition, temperature and conductivity, thus, illustrating correlations with seasonal behaviour. On the basis of these data, species were grouped as (1) late-summer: with 34 species well represented in warm waters (>228C) (e.g. Planctonema lauterbornii and Chroococcus spp.); (2) winter: with 10 species that reached their highest densities in cold waters (<128C) (e.g. Binuclearia eriensis and Microcystis firma); (3) transitional: of only four species with abundance peaks during intermediate conditions (15.58C average) such as Closteriopsis acicularis and Nodularia spumigena and (4) independent: with 22 species of random behaviour whose autocorrelations remain within confidence limits. These four classifications pertain to species with similar presence at both sampling sites; the rest of the species evinced slightly different patterns. An apparent season-associated succession of species was detected with those adapted to the warm, stagnant water of the late summer being replaced by others acclimated to the cold water of the winter.The first row corresponds to mean values and the standard deviation, while the second row gives the observed range. For differences between the sampling sites, the values for the Student t-test and the probabilities ( p) are also shown (n ¼ 28) Ã p < 0.05.

Abiotic factors controlling the seasonal and spatial patterns of phytoplankton community in the Tigris River, Turkey

“…In terms of changes in species composition and density, seasonal and spatial patterns of phytoplankton community variability have been the subject of many studies (Bazzuri, Gabellone, & Solari, ). Although phytoplankton dynamics have been studied extensively in lakes and reservoirs, considerably less research has focused on understanding the species composition and community structure of phytoplankton in streams and rivers (Bazzuri et al, ; Piirsoo, Pall, Tuvikene, & Viik, ; Reynolds, ; Wu, Schmalz, & Fohrer, ). Therefore, more studies are needed to clarify general patterns in phytoplankton community structure in relation to different river types and hydrological regimes (Salmaso & Braioni, ).…”

Phytoplankton chlorophyte structure as related to ENSO events in a saline lowland river (Salado River, Buenos Aires, Argentina)

“…Crucigenia quadrata, M. minutum , and Tetraedron minimun manifested the largest increases in density and were identified as species that preferred the summer season (Descy 1987 ; Bazzuri et al. 2010 ). The significant increase in nonmobile ( M. minutum ) and mobile ( Chlamydomonas spp.)…”

Effects of surface runoff from agricultural soils on the succession of microconsumer organisms in a lotic mesocosm

“…The Salado-River basin (Buenos Aires, Argentina) contains a large number of shallow lakes each with a different degree of connectivity to the main channel and the associated wetlands. These differences have a direct in uence on the degree of salinity, organic matter, and nutrient input into the river, thus determining the structure and composition of the plankton (Bazzuri 2016;Bazzuri et al 2010Bazzuri et al , 2018Bazzuri et al , 2020. Certain shallow lakes associated with the lower basin of the Salado River undergo uctuations in the water level, the conductivity and the the concentration of nutrients; parameters that vary according to the degree of connectivity of those environments to the river and to the hydrologic cycle (Gabellone et al 2001; Solari et al 2002).…”