Cladocera assemblages from the surface sediments of south-central Ontario (Canada) lakes and their relationships to measured environmental variables

Abstract

Fossil cladoceran remains preserved in surface sediment samples from 44 oligotrophic lakes in south-central Ontario were examined to evaluate the relationships between species assemblages and measured environmental variables. Differences in cladoceran assemblages were related to physical and chemical variables using multivariate techniques. Redundancy Analysis (RDA) identified five environmental variables as significantly influencing assemblage composition: sulphate (SO 4 2-), calcium (Ca 2+ ), pH, maximum lake depth (Z max ) and dissolved organic carbon (DOC). There was a distinct separation of lakes and taxa along the ion gradient based on SO 4 , Ca and pH. Additionally, cladoceran communities in coloured, shallow lakes had relatively higher abundances of littoral chydorid species and the pelagic taxa Holopedium spp., and the Daphnia pulex complex. Deep, clear lakes had relatively higher abundances of other pelagic taxa. Predation by fish (measured as presence-absence) and Chaoborus (measured as density) were less significant than some of the physicochemical variables in influencing cladoceran assemblage structure. However, this could be due to the limited resolution of the predation data that was available at the time of this study. The distribution of cladocerans in the surface sediment, and their relation to these important environmental variables, suggests that there is considerable potential for the use of sedimentary cladoceran remains as environmental indicators in south-central Ontario lakes.

Linking mean body size of pelagic Cladocera to environmental variables in Precambrian Shield lakes: A paleolimnological approach

“…In addition, DOC was highly correlated to TP in our lake set (R 2 = 0.81; DeSellas et al 2008), and the size response to the DOC gradient may actually be an artefact of the size-TP relationship. However, the relationship between size and TP was determined to be linear, while size displayed a threshold relationship to DOC.…”

“…In addition to TP, DOC has been shown to be important in shaping cladoceran communities in these study lakes (DeSellas et al 2008;Yan et al 2008b). DOC can influence cladoceran size in a number of ways.…”

“…Cladoceran community dynamics can also be influenced by lakewater pH (DeSellas et al 2008). Some zooplankton taxa experience physiological stress under laboratory conditions of declining pH (Havas 1987).…”

“…Replicate sediment cores were taken from the deepest basin of each of the 42 study lakes in the autumns of 2004(DeSellas et al 2008. A Glew (1989) gravity corer and a miniature Glew (1991) gravity corer were used to collect sediment cores, and a Glew (1988) vertical extruder was used to extract the top 1-cm of sediment from each core (DeSellas et al 2008) the dataset.…”

“…A Glew (1989) gravity corer and a miniature Glew (1991) gravity corer were used to collect sediment cores, and a Glew (1988) vertical extruder was used to extract the top 1-cm of sediment from each core (DeSellas et al 2008) the dataset. Principal components analysis (PCA) was performed on the remaining presence/absence matrix, and the resulting PCA axes 1, 2, and 3 scores were included as predictor variables of cladoceran size structure in the dataset (Tab.…”