Cladocera Community Response to Experimental Eutrophication in Lake 227 as Recorded in Laminated Sediments

Abstract

The response of pelagic zooplankton to experimental fertilization was compared with the fossil record of Cladocera obtained from the annually laminated sediments of Lake 227, Experimental Lakes Area, northwestern Ontario. Constrained cluster analysis of both total fossil Cladocera and littoral chydorid communities clearly distinguished between pre- and post-eutrophication communities and further differentiated between years of high and low nitrogen:phosphorus fertilization ratios. However, there were few chydorid species extirpations resulting from the manipulation. Total chydorid accumulation rates and indices of species diversity, richness, and equitability were relatively constant over the last century and were not affected by fertilization. Among pelagic Cladocera, Bosmina longirostris abundance declined > 60% after initial fertilization. Although harsh chemical conditions (pH > 10) may have contributed to reduced abundance of pelagic Cladocera, Bosmina populations were also naturally variable prior to manipulation. Changes in Bosmina morphology (mucrone, antennule, and carapace length) and cladoceran size ratios (Daphnia/[Daphnia + Bosmina]) suggested that zooplanktivory by fish and invertebrates exercised important control of herbivore populations. Fossil Bosmina concentration (remains∙[g dry wt]−1 or remains∙[g organic matter]−1) were significantly correlated (r = 0.66, P < 0.01, 1970–1989) to standing crop in the water column (animals∙m−2). Fossil accumulation rate (remains∙cm−2∙yr−1) was not significantly correlated to Bosmina abundance, perhaps because of errors in determining bulk sediment accumulation rates.

Effects of production, sedimentation and taphonomic processes on the composition and size structure of sedimenting cladoceran remains in a large deep subalpine lake: paleo-ecological implications

“…However, common patterns can be highlighted. These studies consistently showed that taphonomic processes do not operate equally between zooplankton taxa (Frey, 1960;Hann et al, 1994;Rautio et al, 2000), since cladoceran exoskeletons, in contrast to copepods and rotifers, are well-preserved in lake sediments. Preservation of remains might even differ among cladoceran species with Bosmina and chydorid well represented by different body part (Frey, 1988) in contrast to Daphnia which are usually under-represented in sediment samples compared to Bosmina (Frey, 1960;Kattel et al, 2007;Kattel, 2009;Nykänen et al, 2009).…”

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

“…Despite their usefulness, relatively few quantitative paleolimnological studies of Cladocera have been completed on Ontario lakes (e.g. Hann, 1981;Smol & Boucherle, 1985;Boucherle et al, 1986;Hann et al, 1994;Tremel et al, 2000;St. Jacques et al, 2005).…”

Management Strategies for Large River Floodplain Lakes Undergoing Rapid Environmental Changes

“…The cladocerans display morphological variability (cyclomorphosis) in food web. Vertebrate predation pressure on Bosmina, for example can result in variation in size of the mucro (Hann et al, 1994). In temperate arid Australia, Daphnia carinata show a cyclomorphic behaviour with seasonal changes in body size.…”