Influence of hydrophyte abundance on the spatial distribution of zooplankton in selected lakes in Greece

Abstract

Submerged hydrophyte vegetation consists of a highly important biotic component of maintaining lake ecosystems towards a ''clear water'' ecological status. Aquatic macrophytes are well known to play a significant multidimensional role in lakes by competing with phytoplankton growth, stabilising sediment and offering refuge to fishes, macro-invertebrates and littoral zooplankton, amongst others. Zooplanktons that are associated with macrophyte beds, in particular, may act as a positive feedback mechanism that contributes to maintaining a clear-water state. Although there are several studies investigating the relationships between macrophytes and zooplankton in European lakes, few have yet been carried out in Greek lakes. Seasonal field sampling was conducted from spring 2006 to autumn 2008 in four lakes of northwestern Greece. Zooplankton samples were collected from within hydrophyte beds in each lake to estimate their relative abundance and species density. Hydrophyte abundance and composition was recorded on a five-point scale. Moreover, water samples were analysed to determine nutrient and chlorophyll-a concentration. Pearson correlations between zooplankton density and key physicochemical variables were conducted to distinguish significant abiotic variables related with major zooplankton groups. Kruskal-Wallis non-parametric analysis was used to test for significant differences in zooplankton composition and environmental variables amongst the five hydrophyte abundance classes. In addition, Canonical correspondence analysis was used to distinguish possible correlations amongst the macrophyte and zooplankton species. Zooplankton density was significantly higher in dense macrophyte vegetation. Small-sized species (e.g. Rotifera) dominated the zooplankton community, indicating the eutrophic nature of the lakes. Large Cladocera were present in low abundance and were mostly littoral. The current research contributes to a better understanding of relationships between biotic groups in selected Greek lakes.

Implications of Human Activities, Land Use Changes and Climate Variability in Mediterranean Lakes of Greece

“…(Figures 4 and 5). These changes were confirmed by field observations during 2006-2008 where, apart from the reed bed a diverse submerged macrophytic community was identified [37,38].…”

Ecological impacts of global warming and water abstraction on lakes and reservoirs due to changes in water level and related changes in salinity

“…4e). During this period, charophytes disappeared from the lake and Potamogeton pectinatus increased in abundance (Stefanidis & Papastergiadou, 2010). Between 1987 and1988, charophytes occurred in 33% of the sampling plots, while Potamogeton pectinatus and Myriophyllum spicatum were found in 38 and 52% of the total sampling plots, respectively (Papastergiadou & Babalonas, 1993).…”

Effects of a long term water level reduction on the ecology and water quality in an eastern Mediterranean lake

“…Nitrate, nitrite, ammonium, phosphate, total phosphorus, carbonate, bicarbonate and chlorophyll-a concentrations were determined following the analytical procedure of APHA (APHA, 1992). For the quantification of the zooplankton, subsamples were collected within the macrophyte beds using a tube and were pooled into a vessel in order to form an integrated sample of approximately 10 L (Kuczyńska-Kippen, 2003;Stefanidis and Papastergiadou, 2010). A volume of 6-7 L was finally concentrated through a 50 µm net and fixed immediately with Lugol's solution.…”

“…Rotifera and Cladocera were counted using a Sedgewick-Rafter cell and were identified at species or genus level. Aquatic macrophyte abundance was visually estimated according to a five point scale (1: rare, 2: common, 3: frequent, 4: abundant, 5: dominant, Stefanidis and Papastergiadou, 2010). Frequencies of occurrence were calculated for each taxon at the two different time periods and the taxa were classified into the following categories: rare (<0.25% of quadrats), occasional (0.26-1% of quadrats), common (1-5% of quadrats), abundant (5-20% of quadrats) and very abundant (>20% of quadrats) .…”