Calcium content of littoral Cladocera in three softwater lakes of the Canadian Shield

Abstract

Aqueous calcium (Ca) concentrations are declining in softwater lakes of the Canadian Shield largely because of decades of acid deposition and afforestation following timber harvesting. Populations of pelagic cladoceran taxa with high Ca requirements, especially Daphnia spp., are declining in response to reduced aqueous Ca availability. However, the Ca content, and thus the requirements of littoral cladoceran taxa are unknown; therefore, the potential vulnerability of this major component of lake ecosystems to ongoing regional Ca decline remains uncertain. Here, we identify the body Ca concentration of nine littoral cladoceran taxa collected from three lakes in the Muskoka-Haliburton region of Ontario, Canada. Ca content differed among taxonomic groups, ranging from 3.6 mg g -1 for Acroperus harpae to 23.2 mg g -1 for Disparalona spp. Perhaps surprisingly, some littoral microcrustacean taxa have Ca burdens comparable to the Ca-rich daphniids. Therefore, there may be differential responses to ongoing lake water Ca declines among taxa within littoral communities as has been observed among open-water taxa, with potential ecological repercussions for nearshore food webs.

Changes since the onset of acid deposition among calcium-sensitive cladoceran taxa within softwater lakes of Ontario, Canada

“…and Chydorus spp. ; Jeziorski and Yan 2006;Shapiera et al 2011) were examined. More specifically, as laboratory analyses of Ca limitation within the Cladocera have largely been limited to daphniid species, daphniid changes over time were examined among the two species complexes (i.e.…”

“…In addition, the littoral cladoceran community remains a large, untapped resource for Ca decline studies. Despite large differences in Ca content among some common littoral taxa (Shapiera et al 2011), the Ca requirements of the majority of taxa found in softwater Shield lakes remain unknown, and continued laboratory and field determinations to identify other Ca-sensitive taxa will be valuable. In the meantime, attempts to tease apart the effects of Ca decline from those of acidification will benefit greatly from the adoption of a multi-proxy approach, in order to distinguish between acidified and naturally acidic low Ca lakes.…”

“…having much higher Ca content than Acroperus harpae, Alonella excisa, and Chydorus spp. (Shapiera et al 2011). The species-specific differences in Ca content do not appear to be a simple function of body size, as larger taxa (e.g.…”

“…A. harpae) can have a lower Ca content than their smaller peers (e.g. A. rectangula; Shapiera et al 2011). Furthermore, ambient Ca concentration has been observed to influence daphniid Ca content (albeit to a lesser degree than species identity; Jeziorski and Yan 2006).…”

Cladocera Community Composition as a Function of Physicochemical and Morphological Parameters of Dystrophic Lakes in NE Poland

“…The occurrence of Daphnia (in 3 lakes) and Eubosmina (in 11 lakes) at very low relative abundances was likely more associated with the morphometry of the studied lakes (small and shallow) than with dystrophic conditions. However, low Daphnia percentages may have also been linked with very low calcium content in the water of the lakes, an environmental condition that is critical for the development of most species belonging to this genus (Jeziorski et al 2008;Shapiera et al 2011).…”