AN ASSESSMENT OF ECOLOGICAL CHANGES DURING THE RECENT HISTORY OF LAKE ONTARIO BASED ON SILICEOUS ALGAL MICROFOSSILS PRESERVED IN THE SEDIMENTS^1,2

Abstract

Quantitative analysis of siliceous algal microfossils (diatoms and chrysophytes) in a radiometrically dated core of Lake Ontario sediments shows striking modifications of the flora produced and preserved, apparently as a result of anthropogenic modification of nutrient loadings to the lake, Qualitatively similar microfossil assemblages were deposited during the period ca. 1700–1815. A single major event is recorded in assemblages deposited ca. 1769. Between this event horizon and ca. 1815 there was an apparent increase in algal production, but minimal change in species composition. A major disturbance occurred at the level of the Ambrosia horizon, ca. 1831–1847. Assemblages deposited between ca. 1855 and 1900 indicate increasing eutrophication. We infer that silica limitation became important by about 1860 and that the system reached its greatest effective production ca. 1900. Major modification of the flora occurred in the period ca. 1900–1945, with most local extinctions of major indigenous populations occurring ca. 1920–1945. Assemblages deposited in the period ca. 1945–1975 are composed of some stenothermal populations also present in pre‐disturbance assemblages, a large component of benthic and nearshore planktonic species, and a number of apparently planktonic populations rarely recorded from large temperate lakes, particularly species of the genus Nitzschia. Our results indicate that the major factor driving species succession in Lake Ontario was phosphorus enrichment and consequent depletion of available silica supplies. Our results also show the importance of a species' physical niche in determining its survival under these conditions.

Biology, distribution and ecology of Didymosphenia geminata (Lyngbye) Schmidt an abundant diatom from the Indian Himalayan rivers

“…Since the river waters used as medium to transport trout seed are dominated by D. geminata, it is ossible that this source water brings about accidental dispersal of the diatom (see Kristiansen 2006). There are a number of instances of intentional as well as accidental introduction of diatom species along with fishes (Stoermer et al 1985;Edlund et al 2000).…”

The ecological history of Lake Ontario according to phytoplankton

“…Stoermer, 1993;Stoermer et al, 1996) have furnished essential long-term evidence for establishing environmental trends relevant to primary producers. Limnological conditions and historic shifts in physical and chemical properties in Lake Ontario have been explained using modern and fossil indicator assessments (e.g., Stoermer et al, 1985aStoermer et al, , 1985bWolin et al, 1991;Yang et al, 1993), which were particularly important during a time when few direct measurements of water quality were available. Summaries were recently published for Lake Erie (Allinger and Reavie, 2013) and Lake Superior (Reavie and Allinger, 2011) in an attempt to put recent, rapid changes in a context of long-term lake conditions.…”

Biogenic silica accumulation in the sediments of Iron Gate I Reservoir on the Danube River

“…Records of BSi concentration represent a powerful tool for paleoproductivity and paleoecological reconstruction (Coleman et al, 1992;Granina et al, 1993;Qiu et al, 1993). Past trophic conditions (Carney, 1982;Dixit et al, 1992;Stoermer et al, 1985a) or historical lake phosphorus concentrations (Hall and Smol, 1992;Anderson and Rippey, 1994;Bennion et al, 1996) were reconstructed from sedimentary BSi studies. Fluctuations in the nutrient regime (Stoermer, 1978;Stoermer et al, 1985b) or changes in water residence time (Soballe and Kimmel, 1987) were quantifi ed by investigating the diversity and abundance of diatoms over time.…”