Spatial and seasonal changes of net plankton and zoobenthos in Lake Tonle Sap, Cambodia

Abstract

To clarify spatial and seasonal differences in net plankton and zoobenthos in Lake Tonle Sap, Cambodia, quantitative surveys were carried out at 14 stations in the north and south basins in high-and low-water seasons during 2003-2005. In the phytoplankton communities, a diatom Aulacoseira granulata dominated throughout the lake in the high-water seasons, while blue-green algae, mostly composed of Microcystis, surpassed other algae in the low-water season when the lake water was very turbid and the Secchi disk readings were only a few centimeters. In the low-water seasons, a bloom of floating blue-green algae occurred everywhere, especially prominent in the coastal areas. Protozoans and rotifers dominated the zooplankton communities. In the open-water stations, diversity was higher in high-water seasons in phytoplankton, while it was not significantly different between seasons in zooplankton. Composition of plankton communities in Lake Tonle Sap appears to have changed little since the 1950s, at least in phytoplankton, while the phytoplankton density appears to be higher in the present study. Among the macrozoobenthos, mollusks, oligochaetes and chironomids dominated in density, and mollusks exceeded others in biomass in both basins and seasons. The total densities of macrozobenthos were not high, being fewer than 1,300 m -2 throughout the stations and seasons. Possible reasons for the low zoobenthos abundance in the lake may include high predation pressures by benthivorous fish or unfavorable unstable and flocculant substrates.

Phytoplankton dynamics and species diversity in a shallow eutrophic, natural mid-altitude lake in Himachal Pradesh (India): role of physicochemical factors

“…Ohtaka et al [45] also reported a bimodal pattern of phytoplankton fluctuation in their study on Lake Tonle Sap, Cambodia. During 2008-09, the phytoplankton community (individuals per litre) showed major peak (mode) in May (5.2 × 10 6 ) and minor peaks during August (3.3 × 10 6 ) and September (3.2 × 10 6 ) ( Figure 6).…”

Description of the new freshwater diatom genus Okhapkinia gen. nov. from Laos (Southeast Asia), with notes on family Sellaphoraceae Mereschkowsky 1902

“…In the 21 st century, application of water quality monitoring led to more reports on the freshwater diatoms of the region (e.g. Duong et al 2002;Fujita & Ohtsuka 2005;Ohtaka et al 2010;Leelahakriengkrai et al 2009;Yana & Peerapornpisal 2009;Suphan & Peerapornpisal 2009Blanсo et al 2012), but did not yield description of novel or endemic species. Recently new species and some taxonomical reinvestigation including morphology of some rare species have been described from Vietnam, Laos and Indonesia in our publications (Gusev & Kulikovskiy 2014;Glushchenko & Kulikovskiy 2017;Kociolek et al 2015;Kulikovskiy et al 2015a;Glushchenko et al 2016;Kapustin et al 2017).…”

Filamentous sulfur-oxidizing bacteria of the genus Thioploca from Lake Tonle Sap in Cambodia

“…In Lake Biwa, Thioploca was also detected in a site where sediment temperatures reached 30°C in summer but decreased to 7°C in winter. In contrast, the bottom water temperature of the sampling site in Lake Tonle Sap was 28.1°C in December 2004 and 30.9°C in May 2005 (Ohtaka et al 2010). The phylogenetic diversity within Thioploca of Lake Tonle Sap was consistently shown in the analyses of 16S rRNA, 23S rRNA, and the ITS region.…”

“…The sampling site, Site S3 (12°33' 57'' N, 104°22' 10'' E; 0.4 m deep), corresponds to the site of a previous study (Ohtaka et al 2010). At the sampling time, the pH and specific conductivity of surface water were 8.0 and 155 µS cm −1 respectively (Ohtaka et al 2010). The lake water was characterized by very low transparency (0.02 m).…”

“…This lake is characterized by a dramatic seasonal change of water level, and the samples were obtained in the season of shallow water depth. The sampling site, Site S3 (12°33' 57'' N, 104°22' 10'' E; 0.4 m deep), corresponds to the site of a previous study (Ohtaka et al 2010). At the sampling time, the pH and specific conductivity of surface water were 8.0 and 155 µS cm −1 respectively (Ohtaka et al 2010).…”