The biovolume and species composition of algae on the sediment along a depth gradient were determined before and after liming of acidic (pH 4.9), oligotrophic Woods Lake in the Adirondack Park in New York State (Herkimer Co., NY, USA). The epipelic algal community was dominated by diatoms and cyanobacteria prior to and following liming. Distinct depth zonation patterns of community composition were evident and unaffected by CaCO3 addition. Treatment with calcite increased pH from 4.9 to above 9.0, caused ANC to rise from 0 to >400 μeq∙L−1, and immediately reduced overall water clarity which subsequently improved during the summer. There was a significant decrease (p <0.001) in total algal biovolume after liming corresponding to a significant reduction in biovolume of Hapalosiphon pumilus at the deepest sites. Total diatom biovolume was not significantly changed as a result of the addition of calcite; however, a shift in community composition from dominance by Navicula tenuicephala and Fragilaria acidobiontica to dominance by Achnanthes microcephala and Anomoeoneis vitrea was observed following liming.
Comparative marine biodiversity and depth zonation in the Southern Ocean: evidence from a new large polychaete dataset from Scotia and Amundsen seas