Phycological studies in lakes Ontario, Erie, Huron, and Superior

Abstract

An indepth phycological comparison is presented for lakes Ontario, Erie, Huron, and Superior, based on extensive lake-wide surveys carried out during the past 12 years. This comparison was achieved by the application of standard and consistent identification, enumeration, and data-processing techniques. The resulting species composition data are voluminous and present a broad picture of the phytoplankton assemblage. Our data base has enabled us to assess the long-term floristic changes, knowledge of which is lacking in the Great Lakes. The species composition reflects more or less the current trophic status of these lakes. The preponderance of nannoplankton and phytoflagellates is the subject of our current experimental research, which includes the fractionation of chlorophyll a and carbon-14 uptake, toxicity studies of heavy metals upon various size fractions of algae, and the role of microalgae and ultraplankton in the transfer of contaminants via zooplankton grazing. The need for phycological research in the Great Lakes is expanding with decreasing eutrophication and the increasing problems of contaminants. The recovery, rehabilitation, and preservation of these vital freshwaters are the primary concern of the continuing Canadian research program in the Great Lakes.

The long, the short and the stalled: on the attributes of phytoplankton selected by physical mixing in lakes and rivers

“…The sensitivity of algal suspension to the extent of turbulent mixing and to the frequency of its variability are important contributing factors in the spatial and temporal distribution of phytoplankton generally and diatoms in particular. In addition to the seasonality of diatoms among smaller temperate lakes and, often, those at lower latitudes, there is also evident a mixingdependent pattern among larger lakes, which may be invoked to account for the prevalence of diatoms in large well-mixed lakes of Eurasia and N America, through much of the year (Skabichevskii, 1960;Lund, 1962;Munawar & Munawar, 1982), during the less thermally stable periods in the tropical Lake Victoria and Tanganyika (Talling, 1966;Hecky & Kling, 1981) and under clear ice in Lake Baikal, when a convective layer of up to 25 m in depth may be maintained (Rossolimo, 1957). Of particular interest are those lowlatitude lakes which experience diel cycles of stratification and mixing: whereas many of these may come to support a dominant planktonic population of larger, motile species whose own movements can accommodate the variability (often Microcystis: Reynolds, 1993b), others support dominant populations of the diatoms Aulacoseira.…”

Quantification of virus genes provides evidence for seed-bank populations of phycodnaviruses in Lake Ontario, Canada

“…As phycodnaviruses infecting the same host taxa typically cluster in monophyletic groups Brussaard et al, 2004), it is plausible that the hosts of the viruses encoding these genes are prasinophytes or closely related phytoplankton. Surprisingly, while phytoplankton surveys of Lake Ontario noted the high diversity and abundance of chlorophyte phytoplankton, no prasinophytes were ever reported (Munawar and Munawar, 1982). It is possible that prasinophytes were present but missed because they were too small or too few for microscopy-based identification; many prasinophytes are picoplankton (o3 mm), and entire clades of unknown prasinophytes have been discovered recently via molecular surveys (Viprey et al, 2008).…”

Differential effects of phosphorus limitation on cellular metals in Chlorella and Microcystis

“…LE-3). Both species are isolated from Lake Erie and represent important classes of primary producers that have been documented in the North American Great Lakes (Munawar and Munawar 1982). The current study was carried out to complement ongoing field studies in Lake Superior, an extremely P-deficient aquatic system (Sterner et al 2004;Anagnostou 2005;Anagnostou and Sherrell 2008) in which Zn cycling has been shown to be particularly intense (Nriagu et al 1996;Sherrell unpubl.).…”