Time filter

Source Type

Laird K.R.,Queens University | Das B.,Environment Canada | Kingsbury M.,Queens University | Moos M.T.,Lake Simcoe Region Conservation Authority | And 5 more authors.
Hydrobiologia | Year: 2013

The extraction of bitumen from the Athabasca oil sands is rapidly expanding, and emission of sulphur and nitrogen oxides has substantially increased. To determine whether lakes downwind of this development in northwest Saskatchewan have been detrimentally impacted since development of the oil sands, a paleolimnological assessment of ten lakes was carried out. Analysis of diatom valves and inferences of diatom-inferred pH indicated that emissions have not resulted in widespread chronic acidification of acid-sensitive lakes ~80-250 km east and northeast of the oil sands development around Fort McMurray and Fort Mackay. However, one of the closest sites to the development indicated a slight decline in diatom-inferred pH, but the two next closest sites, both of which had higher alkalinity, did not show any evidence of acidification. There were also no consistent trends in the concentration or flux of total or individual priority pollutants including lead, mercury, copper, zinc and vanadium. The sedimentation rates in most lakes increased since the mid-1900s, along with increased flux of both diatoms and scaled chrysophytes. Subtle changes in the species assemblages of diatoms and increased flux of diatoms and chrysophyte scales are consistent with recent climate change in this region. © 2013 Springer Science+Business Media Dordrecht.

Ozersky T.,Ontario Ministry of Natural Resources | Ozersky T.,University of Minnesota | Evans D.O.,Ontario Ministry of Natural Resources | Ginn B.K.,Lake Simcoe Region Conservation Authority
Freshwater Biology | Year: 2015

This study examined the effect of invasive dreissenid mussels on nutrient and carbon dynamics in a large lake (Lake Simcoe, Ontario). We measured rates of nutrient (phosphorus and nitrogen) and carbon excretion and biodeposition by zebra and quagga mussels and the P, N and C content of their soft tissues and shells at different depths throughout the open-water season. Measurements were combined with detailed information about dreissenid biomass and lakewide distribution to examine the impacts of dreissenids on whole-lake dynamics of P, N and C. Mussel tissue P, N and C content and rates of excretion and biodepositon varied among species, seasons and depths, apparently driven by metabolic and stoichiometric factors. Dreissenid mussels excreted, deposited and stored large quantities of P, N and C when compared to lake standing stocks and loadings, and represent an important driver of nutrient cycling in the lake. Living and discarded mussel shell material is shown to represent a potentially important, and hitherto largely overlooked, long-term sink for P, N and C. The concentration of dreissenid biomass in the well-mixed and illuminated littoral portion of L. Simcoe results in redirection of nutrients and carbon from offshore areas to the nearshore zone of the lake. Changes in nutrient and carbon distribution and cycling patterns caused by dreissenid establishment in L. Simcoe and other ecosystems can have implications for the distribution of primary and secondary production and should be considered in the context of water quality and nutrient input management. © 2015 John Wiley & Sons Ltd.

Species composition, distribution, and biomass of submerged aquatic plants were studied in Lake Simcoe (Ontario, Canada) as was the use of macrophytes as indicators of lake trophic status. While previous studies in this lake targeted one eutrophic embayment, this study covered the entire lake area, identified five areas of high plant biomass and recorded 16 macrophyte species; the community was dominated by Ceratophyllum demersum (39.1% of the total biomass), the invasive species Myriophyllum spicatum (27.4%), Elodea canadensis (10.7%) and Chara spp. (9.7%). Canonical correspondence analysis (CCA) identified four significant limnological variables related to plant biomass: (a) depth, likely a proxy for light levels; (b) substrate type, related to nutrient availability, stability, and wave exposure; (c) phosphorus loading from the closest tributary; and (d) size of the area drained by a tributary. Since initial (1971) macrophyte surveys on Lake Simcoe, the community has been dramatically altered by expansion of an invasive species (i.e. M. spicatum) resulting in declines of native shallow-water species (e.g. Chara spp.). The arrival of zebra mussels (Dreissenia polymorpha) ~1995 and reductions in phosphorus loading have increased water clarity, extending the maximum depth of plant colonization (6.0m in 1984 to 10.5m in 2008), and almost tripled macrophyte biomass (1.2kg·m-2 in 1984 to 3.1kg·m-2 in 2008). Increased plant biomass, and a loss of species diversity due to spread of M. spicatum are interpreted by macrophyte indices as a decrease in lake trophic status, which likely explains why these indices did not follow trends in reduced phosphorus loading. © 2011 International Association for Great Lakes Research.

Loh P.S.,York University | Molot L.A.,York University | Nurnberg G.K.,Freshwater Research | Watson S.B.,National Water Research Institute | Ginn B.,Lake Simcoe Region Conservation Authority
Inland Waters | Year: 2013

This study evaluated phosphorus (P) and iron (Fe) release from anoxic sediment cores in 3 different water bodies, Lake Winnipeg in Manitoba and Lake Simcoe and Hamilton Harbour in Ontario, and developed empirical models to predict P and Fe release rates as functions of sediment and water chemistry. Maximum P and Fe sediment release rates, which occurred shortly after sulfate (SO4) was depleted in most cores, showed unique positive linear relationships for each lake. High P release rates only occurred from Lake Simcoe and Lake Winnipeg sediments with molar ratios ≤8.1 of NaOH-extractable aluminum (Al) to reducible Fe (Fe extractable with bicarbonate-dithionite [BD]). High Fe release rates only occurred in Lake Winnipeg sediments, perhaps due to low SO4 reduction rates (<115 mg m-2 d-1). Three approaches were used to develop linear regression models for maximum P and Fe release rates using data from all lakes: only Lake Winnipeg, only Lake Simcoe, and low (≤8.1) and high molar ratios (>20) of NaOH-extractable Al to BD-extractable Fe. Regression models differed depending on the study sites used, and only 3 of the 5 significant regression models for P release had high predictive value (R2 > 0.7). Four of the 5 significant Fe release models had R2 > 0.7, but we were unable to find a significant Fe model for Lake Simcoe. These results are important because they delineate the limitations of this approach to modeling release using operationally defined fractions. © Her Majesty the Queen in Right of Canada, as represented by Environment Canada 2013.

Nurnberg G.K.,Freshwater Research | Molot L.A.,York University | O'Connor E.,Lake Simcoe Region Conservation Authority | Jarjanazi H.,Environment Canada | And 2 more authors.
Journal of Great Lakes Research | Year: 2013

Hypoxia and cyanobacterial blooms were extensive in Lake Simcoe during the 1980s and are still a problem to a lesser degree despite extensive nutrient load reduction from the catchment basin. The continuing signs of productivity indicate a potential internal phosphorus (P) source. Internal P load, as a redox-dependent release from bottom sediments, is hard to determine in a large, relatively shallow and partially unstratified lake such as Lake Simcoe. Of the lake's three major basins, only Kempenfelt Bay stratifies long enough to develop hypoxia in the stagnant summer hypolimnion. The following indications of sediment P release are available from historic data: 1) hypolimnetic hypoxia still occurs in Kempenfelt Bay although the hypoxic factor (number of days that an area equal to the bay's surface area is overlain by water of ≤. 2. mg/L dissolved oxygen, DO) has decreased substantially and significantly from 15.8. d/yr (1980-1994) to 4.0. d/yr (1995-2011); 2) hypoxic factors for other lake sections and at different DO levels also indicate widespread hypoxia; 3) concentrations of redox dependent metals, Fe and Mn, increase with depth; and 4) euphotic zone P and chlorophyll concentrations increase and water clarity decreases during fall turnover. Cyanobacterial blooms appear to occur in response to internal load as supported by occasional cyanobacteria counts. These indicators provide evidence that internal loading is likely occurring and affecting the water quality in Lake Simcoe. We expect that further monitoring, specific for internal load, will corroborate these results. © 2013 Elsevier B.V.

Discover hidden collaborations