Long-term trends in hypolimnetic volumes and dissolved oxygen concentrations in Boreal Shield lakes of south-central Ontario, Canada

2019 ◽  
Vol 76 (12) ◽  
pp. 2315-2325 ◽  
Author(s):  
Clare Nelligan ◽  
Adam Jeziorski ◽  
Kathleen M. Rühland ◽  
Andrew M. Paterson ◽  
John P. Smol
Keyword(s):  
Dissolved Oxygen ◽  
Climatic Factors ◽  
Thermocline Depth ◽  
South Central ◽  
Air Temperatures ◽  
Hypolimnetic Oxygen ◽  
Long Term Trends ◽  
Shield Lakes ◽  
Carbon Concentrations

Temperature–oxygen profiles, collected biweekly to monthly for ∼40 years, were used to calculate end-of-summer volume-weighted hypolimnetic oxygen (VWHO) concentrations in six small lakes located in south-central Ontario, Canada. Coherent decreases in thermocline depth and increases in hypolimnetic volume, mean hypolimnetic dissolved oxygen (DO) concentration, and VWHO were observed in five of the six study lakes. All lakes underwent an abrupt increase in VWHO and mean hypolimnetic DO after 2010. In four of the six study lakes, the highest hypolimnetic DO concentrations were observed in years where chlorophyll a concentrations were low, whereas at five of the six study lakes the highest hypolimnetic volumes were observed when dissolved organic carbon concentrations were relatively high. Warmer spring or winter air temperatures were associated with higher hypolimnetic DO concentrations at two sites, and longer ice-free periods were associated with smaller hypolimnetic volumes at two sites. These results suggest that the recent VWHO increases in the studied south-central Ontario lakes may be a function of multiple drivers that include changes in primary production, lake water transparency, and regional climatic factors.

Quantitative inferences of past hypolimnetic anoxia in south-central Ontario lakes using fossil midges (Diptera: Chironomidae)

1998 ◽  
Vol 55 (3) ◽  
pp. 587-596 ◽  
Author(s):  
Roberto Quinlan ◽  
John P Smol ◽  
Roland I Hall
Keyword(s):  
Weighted Averaging ◽  
Species Variation ◽  
Calibration Model ◽  
Forward Selection ◽  
Lake Ecosystems ◽  
South Central ◽  
Hypolimnetic Oxygen ◽  
Chironomid Assemblages ◽  
Shield Lakes

The ability to infer long-term changes in hypolimnetic oxygen levels is important for ecological studies of eutrophication and the impacts of climatic change on freshwater lakes. We examined the distributions of fossil midge (Diptera: Chironomidae) assemblages in the surface sediments of 54 south-central Ontario lakes and, using canonical correspondence analysis (CCA), determined if fossil chironomid assemblages could be used to reconstruct levels of hypolimnetic anoxia in thermally stratifying Laurentian Shield lakes. Anoxia was expressed as the anoxic factor (AF), which represents the days per season that a sediment area equal to a lake's surface area is overlain by anoxic water. Forward selection in CCA showed that AF, maximum depth, [SO4], [Na], and watershed area all explained significant portions of species variation. A weighted-averaging regression and calibration model of the chironomid-anoxia relationship was developed which suggests that it is possible to infer AF from fossil chironomid assemblages ( (r2appar ) = 0.70, bootstrapped RMSE = 6.5 days/summer). Quantitative reconstruction of past changes in anoxia using fossil Chironomidae should provide a new and useful tool for paleoecological assessments of lake ecosystems.

scholarly journals Effects of climatic factors and air pollution on damage of London plane (Platanus hispanica Mill.)

2010 ◽  
Vol 37 (No. 3) ◽  
pp. 109-117 ◽  
Author(s):  
B. Gregorová ◽  
K. Černý ◽  
V. Holub ◽  
V. Strnadová
Keyword(s):  
Air Pollution ◽  
Regression Analysis ◽  
Health Status ◽  
Climatic Factors ◽  
Total Precipitation ◽  
The Czech Republic ◽  
Air Temperatures ◽  
Significant Regression ◽  
London Plane

London plane (Platanus hispanica Mill.) is considered as very tolerant to pollution and other stresses and in the Czech Republic it has been unaffected by important pathogens until now. However, in recent years the health status of London plane has been significantly deteriorating. During an 11-year survey it was found out that development of London plane damage was characterized by important fluctuations. Minimum value of population damage was 3.6% and maximum 97.5%. The health status of London plane was negatively influenced by long-term precipitation totals, higher total precipitation in May, low average air temperatures in January and May and higher NO<sub>x</sub> concentrations in the vegetation season. Using the multiple regression analysis a highly significant regression model was obtained, wherein the average air temperatures in January and May explain together 84% variability of London plane population damage. During the period of the highest damage, planes were moreover affected by the pathogen Apiognomonia veneta (Sacc. et Spegg.) H&ouml;hn. &nbsp;

scholarly journals Environmental and climatic factors affecting winter hypoxia in a freshwater lake: evidence for a hypoxia refuge and for re-oxygenation prior to spring ice loss

Hydrobiologia ◽  
2020 ◽  
Vol 847 (19) ◽  
pp. 3983-3997
Author(s):  
Michael N. Davis ◽  
Thomas E. McMahon ◽  
Kyle A. Cutting ◽  
Matthew E. Jaeger
Keyword(s):  
Dissolved Oxygen ◽  
Spatial Variability ◽  
Climatic Factors ◽  
Oxygen Depletion ◽  
Late Winter ◽  
Factors Affecting ◽  
Arctic Grayling ◽  
Air Temperatures ◽  
Depletion Rate ◽  
Rock Lake

Abstract Low dissolved oxygen, or hypoxia, is a common phenomenon in ice-covered lakes in winter. We measured dissolved oxygen (DO) before, during, and after ice-over to characterize the timing, severity, and spatial variability of winter hypoxia in Upper Red Rock Lake, Montana, home to one of the last remaining lacustrine populations of endemic Montana Arctic Grayling (Thymallus arcticus). Unlike most previous investigations of winterkill-prone lakes, we observed considerable horizontal spatial variability in DO, a non-linear winter oxygen depletion rate, and lake-wide re-oxygenation 2–4 weeks prior to spring ice loss. Parts of the upper 1 m of the lake and near stream mouths remained well-oxygenated even during late winter. DO levels were strongly associated with maximum daily air temperature. Our analysis of a 28-year weather record revealed large interannual variability in risk of winter hypoxia, with a slight declining trend in winter severity (number of days with maximum air temperatures ≤ 0°C) in Upper Red Rock Lake. The approach we used in our study provides a useful framework for quantifying and mapping the seasonal dynamics of the extent and severity of winter hypoxia, and for identifying critical winter habitats.

A comparison of pre-industrial and present-day changes in Bosmina and Daphnia size structure from soft-water Ontario lakes

2010 ◽  
Vol 67 (4) ◽  
pp. 754-762 ◽  
Author(s):  
Jennifer B. Korosi ◽  
Andrew M. Paterson ◽  
Anna M. DeSellas ◽  
John P. Smol
Keyword(s):  
Body Size ◽  
Size Structure ◽  
South Central ◽  
Zooplankton Size ◽  
Copepod Predation ◽  
Post Impact ◽  
North Temperate Lakes ◽  
Impact Data ◽  
Shield Lakes

Understanding the long-term controls on cladoceran size structure has important implications for aquatic ecosystems. Although there has been considerable interest in zooplankton size trends for Canadian Shield lakes, data are not available for zooplankton size structure prior to the period of anthropogenic disturbances. Here, we present pre- and post-impact size data for the common pelagic cladocerans Bosmina and Daphnia for 44 well-studied Shield lakes in south-central Ontario (Canada). We show that Daphnia were larger and that the length of Bosmina body appendages (mucrones and antennules) was longer in pre-industrial times than they are today. The reduction in Bosmina appendage length we observed may suggest a reduction in copepod predation pressure since pre-industrial times. Reduced maximum body size in Daphnia is a predicted response to a warming climate in north temperate lakes; however, we suggest that alternate explanations, specifically acidification and subsequent recovery following emission reductions, should also be explored as the primary drivers of Daphnia size changes in this lake set. Overall, our results highlight the importance of pre-impact data for understanding the long-term controls on cladoceran body size from pre-1850 to present.

scholarly journals Long-term trends in solar radiation and the associated climatic factors over China for 1961-2000

2005 ◽  
Vol 23 (7) ◽  
pp. 2425-2432 ◽  
Author(s):  
F. Liang ◽  
X. A. Xia
Keyword(s):  
Solar Radiation ◽  
Climatic Factors ◽  
Sunshine Duration ◽  
Cloud Amount ◽  
Atmospheric Composition ◽  
Abrupt Decrease ◽  
Radiative Processes ◽  
Aerosol Loading ◽  
Long Term Trends

Abstract. Long-term trends in downwelling solar irradiance and associated climatic factors over China are studied in the paper. Decreasing trends in global and direct radiation are observed over much of China. The largest decrease occurs in South and East China (east of about 100° E and south of about 40° N). The spatial pattern of observed trends in diffuse irradiance is complex and inhomogeneous. An intriguing aspect of trends in global and direct irradiance is the rather abrupt decrease in annual and seasonal mean values from 1978 onward. The decreasing trends in solar radiation in China did not persist into the 1990s. The spatial and temporal patterns of trends in sunshine duration are consistent with that of global and direct irradiance. A decreasing trend in rainy days is observed over much of China, which is in agreement with the secular trend in cloud amount. The fact that trends in cloud amount and solar radiation are quite similar suggests that the cloud amount is not the primary cause for the decrease in solar radiation. Visibility in the eastern part of China has deteriorated heavily as a result of the rapid increase in aerosol loading. The statistical analysis showed that atmospheric transmission under clear conditions decreased rapidly. These facts suggest that the rapid increase in aerosol loading should be one of the principle causes for the decrease in solar radiation. The observed diurnal temperature range decreases remarkably in China, which is closely related to the increase in aerosols. The effects of anthropogenic air pollutants on climate should be further studied and included in the simulation of climate and projection of climate scenario. Keywords. Atmospheric composition and structure (Aerosol and particles; General or miscellaneous) – Meteorology and atmospheric dynamics (Radiative processes)

Long-term declines in phosphorus export from forested catchments in south-central Ontario

2009 ◽  
Vol 66 (10) ◽  
pp. 1682-1692 ◽  
Author(s):  
M. Catherine Eimers ◽  
Shaun A. Watmough ◽  
Andrew M. Paterson ◽  
Peter J. Dillon ◽  
Huaxia Yao
Keyword(s):  
Stream Flow ◽  
Seasonal Patterns ◽  
Forested Catchments ◽  
Annual Average ◽  
Temporal And Spatial Patterns ◽  
South Central ◽  
Hydrologic Event ◽  
Temporal And Spatial ◽  
Shield Lakes

Total phosphorus (TP) levels in many Canadian Shield lakes in central Ontario have declined over recent decades, despite increases in human activity in most watersheds. To investigate the contribution of changes in catchment export to long-term declines in lake TP, we examined temporal and spatial patterns in TP concentrations and export (1980–1981 to 2001–2002) across 11 subcatchments that drain into three lakes in which average ice-free TP levels have declined by approximately 35%. Annual stream export of TP decreased significantly by 30%–89% in eight of the 11 subcatchments, and decreases in export were driven by declines in TP concentration, not changes in stream flow. Annual average TP concentrations varied fivefold among adjacent subcatchments, and temporal patterns in annual average TP concentrations were poorly correlated. Seasonal patterns of TP concentration were most similar among streams in the spring (March–April–May), and TP export in the spring declined significantly in 10 of the 11 subcatchments. Because spring melt is the principal hydrologic event in these seasonally snow-covered basins, decreases in TP export during the spring were primarily responsible for declines observed in annual export. The drivers of changes in TP over time are unclear at this point but are the focus of current research.

scholarly journals Long-term Trends of Organic Carbon Concentrations in Freshwaters: Strengths and Weaknesses of Existing Evidence

Water ◽  
2014 ◽  
Vol 6 (5) ◽  
pp. 1360-1418 ◽  
Author(s):  
Montserrat Filella ◽  
Juan Rodríguez-Murillo
Keyword(s):  
Organic Carbon ◽  
Long Term Trends ◽  
Carbon Concentrations
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