Using temporal coherence to determine the response to climate change in Boreal Shield lakes (original) (raw)
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Lancet, 2011
Climatic change is recognized as an important factor capable of influencing the structural properties of aquatic ecosystems. Lake ecosystems are particularly sensitive to climate change. Several long time-series studies have shown close coupling between climate, lake thermal properties and individual organism physiology, population abundance, community structure, and food-web structure. Understanding the complex interplay between climate, hydrological variability, and ecosystem structure and functioning is essential to inform water resources risk assessment and fisheries management. The purpose of this paper is to present the current understanding of climate-induced changes on lake ecosystem phenology. We first review the ability of climate to modulate the interactions among lake hydrodynamics, chemical factors, and food-web structure in several north temperate deep lakes (e.g., Lake Washington, Lake Tahoe, Lake Constance, Lake Geneva, Lake Baikal, and Lake Zurich). Our aim is to assess long-term trends in the physical (e.g., temperature, timing of stratification, and duration of ice cover), chemical (e.g., nutrient concentrations), and biological (e.g., timing of the spring bloom, phytoplankton composition, and zooplankton abundance) characteristics of the lakes and to examine the signature of local weather conditions (e.g., air temperature and rainfall) and large-scale climatic variability (e.g., ENSO and PDO) on the lake physics, chemistry and biology. We also conducted modeling experiments to quantify the relative effect of climate change and nutrient loading on lake phenology. These modeling experiments focused on the relative changes to the major causal associations underlying plankton dynamics during the spring bloom and the summer stratified period. To further understand the importance of climate change on lakes, we propose two complementary directions of future research. First, additional research is needed to elucidate the wide array of in-lake processes that are likely to be affected by the climate change. Second, it is essential to examine the heterogeneity in responses among different water bodies. The rationale of this approach and its significance for dealing with the uncertainty that the climate signals cascade through lake ecosystems and shape abiotic variability and/or biotic responses have been recently advocated by several other synthesis papers.
Vulnerability of northern lake ecosystems to climate change
Vulnerability of Cryospheric and …, 2006
Lakes and ponds are a major element of the northern landscape. They are habitats for aquatic wildlife, aqueous systems for biogeochemical and photochemical processes, and rich centres of microbial biodiversity. Many of these limnetic ecosystems are also important to local native communities as hunting and fishing sites, and in some cases they have additional value as reservoirs for hydroelectricity generation and for drinking water supplies. These ecosystems are integrators of their surrounding catchment properties including geomorphology, lithology, hydrology, vegetation and permafrost soil dynamics. Many of these properties, as well as intrinsic limnological characteristics of the lakes such as ice-cover and mixing regime, are strongly dependent on climate. These features, in combination with the predicted magnitude of warming at high northern latitudes , imply that northern lakes are sensitive indicators of global climate change.
Water Resources Research, 2008
1] We explored relations between climate and trophic status of shallow lakes (lake area > 5 ha, mean depth < 3.2 m) located on the subhumid western Boreal Plain of Canada. Correlation and regression analyses were used to assess the association between indicators of climate and satellite-based estimates of trophic status (chlorophyll a (Chl a)). Chl a was derived using red band reflectance of Landsat satellite images for 76 lakes, which were then averaged for each year to produce a landscape median for summer (August) over a 20-year period from 1984 and 2003. Our results showed that climate was related to interannual changes in trophic status. Average May temperature was positively correlated to Chl a, suggesting the importance of conditions in the early part of the growing season. Growing season effective precipitation (P -PET) was negatively correlated to Chl a such that wetter conditions seemed to lead to a dilution of Chl a. Very wet years resulted in a larger Chl a drop than one expected by a linear model, suggesting greater water contribution from the landscape. P -PET explained 64% of the variance in Chl a using a nonlinear regression tree. Our study offers clues as to how shallow lake systems may behave on the subhumid Boreal Plain as a function of future climate change.
Lakes as sentinels of climate change
Limnology and Oceanography, 2009
While there is a general sense that lakes can act as sentinels of climate change, their efficacy has not been thoroughly analyzed. We identified the key response variables within a lake that act as indicators of the effects of climate change on both the lake and the catchment. These variables reflect a wide range of physical, chemical, and biological responses to climate. However, the efficacy of the different indicators is affected by regional response to climate change, characteristics of the catchment, and lake mixing regimes. Thus, particular indicators or combinations of indicators are more effective for different lake types and geographic regions. The extraction of climate signals can be further complicated by the influence of other environmental changes, such as eutrophication or acidification, and the equivalent reverse phenomena, in addition to other land-use influences. In many cases, however, confounding factors can be addressed through analytical tools such as detrending or filtering. Lakes are effective sentinels for climate change because they are sensitive to climate, respond rapidly to change, and integrate information about changes in the catchment.
Lakes and reservoirs as sentinels of present climate change
While there is a general sense that lakes can act as sentinels of climate change, their efficacy has not been thoroughly analyzed. We identified the key response variables within a lake that act as indicators of the effects of climate change on both the lake and the catchment. These variables reflect a wide range of physical, chemical, and biological responses to climate. However, the efficacy of the different indicators is affected by regional response to climate change, characteristics of the catchment, and lake mixing regimes. Thus, particular indicators or combinations of indicators are more effective for different lake types and geographic regions. The extraction of climate signals can be further complicated by the influence of other environmental changes, such as eutrophication or acidification, and the equivalent reverse phenomena, in addition to other land-use influences. In many cases, however, confounding factors can be addressed through analytical tools such as detrending or filtering. Lakes are effective sentinels for climate change because they are sensitive to climate, respond rapidly to change, and integrate information about changes in the catchment.
Impact assessment of climate changing patterns on ecosystem productivity of lakes: A crtical review
Abstract: Climate change is recognized as a threat on ecosystem productivity of lakes. Climatic variation affects the hydrological, physico-chemical and biological characteristics of lakes. Climatic change will make future efforts to change the water quality and its trophic status of lakes and wetland ecosystem. Impacts of global warming on lakes include an extended growing period at high latitudes, intensified stratification and nutrient loss from surface waters, decreased hypolimnetic oxygen (below the thermocline) in deep, stratified lakes and expansion in range for many invasive aquatic weeds. Direct effects of climate change on lakes includes changes in temperature, water level, pH, concentration of dissolved gases (dissolved oxygen, free carbon dioxide, ammonia etc.). Elevated temperatures would decrease oxygen solubility and increase the rates of microbial oxygen demand, both leading to a decrease in dissolved oxygen available for biotic communities in different trophic level of lake ecosystem. Climate changes are increasingly recognized as important regulatory factors to assess the primary productivity in relation to distribution changing pattern of biotic communities (phytoplankton, zooplankton aquatic birds and fish species) in the lake ecosystem. The remedial measures for regulate the impact assessment of climate change on lake ecosystem are required scientific attentions on national and international environmental forums. Key words: Climate Change, Ecosystem productivity, Lake, Aquatic Biodiversity
Climate change drives coherent trends in physics and oxygen content in North American lakes
Climatic Change, 2014
Using a 25-year record of monitoring data, we show that recent climate change has affected the thermal properties and oxygen content of seven lakes in south-central Ontario, Canada, and five lakes in north-central Wisconsin, USA. Coherent patterns in autumnal lake warming were driven by increased autumn air temperature in both lake districts. Temperature increases were restricted to the epilimnion and metalimnion of the lakes, resulting in increased thermal stability of the water column. Mixing depths also decreased over the study period. Shallower mixing depths in the Ontario lakes were due to climate-driven increases in lakewater dissolved organic carbon concentrations. Collectively, changes in the thermal regime of the lakes suggest autumn mixing of the water column may be delayed. Metalimnetic oxygen also increased in the Wisconsin lakes, perhaps in response to increased algal production as lake thermal regimes changed. The response of individual lakes to climate change was modified by lake chemistry in the Ontario lake district and by lake chemistry and morphometry in the Wisconsin lake district. Our results demonstrate coherent lake response to climate change and highlight the importance of both regional and local factors in regulating individual lake response to global climate change.
A comparison of shallow Danish and Canadian lakes and implications of climate change
Freshwater Biology, 2007
1. Winter temperatures differ markedly on the Canadian prairies compared with Denmark. Between 1 January 1998 and 31 December 2002, average weekly and monthly temperatures did not drop below 0°C in the vicinity of Silkeborg, Denmark. Over this same time, weekly average temperatures near Calgary, Alberta, Canada, often dropped below )10°C for 3-5 weeks and the average monthly temperature was below 0°C for 2-4 months. Accordingly, winter ice conditions in shallow lakes in Canada and Denmark differed considerably. 2. To assess the implications of winter climate for lake biotic structure and function we compared a number of variables that describe the chemistry and biology of shallow Canadian and Danish lakes that had been chosen to have similar morphometries. 3. The Danish lakes had a fourfold higher ratio of chlorophyll-a: total phosphorus (TP). Zooplankton : phytoplankton carbon was related to TP and fish abundance in Danish lakes but not in Canadian lakes. There was no significant difference in the ratio log total zooplankton biomass : log TP and the Canadian lakes had a significantly higher proportion of cladocerans that were Daphnia. These differences correspond well with the fact that the Danish lakes have more abundant and diverse fish communities than the Canadian lakes. 4. Our results suggest that severe Canadian winters lead to anoxia under ice and more depauperate fish communities, and stronger zooplankton control on phytoplankton in shallow prairie lakes compared with shallow Danish lakes. If climate change leads to warmer winters and a shorter duration of ice cover, we predict that shallow Canadian prairie lakes will experience increased survivorship of planktivores and stronger control of zooplankton. This, in turn, might decrease zooplankton control on phytoplankton, leading to 'greener' lakes on the Canadian prairies.
Inland Waters, 2020
Rapid climate changes may potentially have strong impacts on the ecosystem structure and nutrient dynamics of lakes as well as implications for water quality. We used a space-for-time approach to elucidate such possible effects by comparing data from 1656 shallow lakes (mean depth <3 m) in north temperate Denmark (DK) and subtropical Florida (FL). The lakes were categorized into 7 total phosphorus (TP) classes within the range of 2 to 300 µg L −1. Physicochemical variables showed significant seasonal differences, which can be attributed to different sunlight regimes and temperatures. The FL lakes had overall higher fish biomasses (notably in the littoral zone) but a substantially lower zooplankton biomass and body mass of microcrustaceans, a much lower zooplankton:phytoplankton biomass ratio (lower grazing on phytoplankton), and a markedly lower biomass of benthic invertebrates, indicating much greater control of consumers by fish in the FL lakes. Accordingly, the summer phytoplankton biomass was higher in the FL lakes. Cyanobacteria in summer were proportionally more important in the FL lakes at all TP levels, whereas the proportion of dinophytes, chrysophytes, and cryptophytes was higher in the DK lakes at low TP. Submerged macrophytes occurred at higher TP (>100 µg L −1) in the FL lakes, but coverage was higher in the DK lakes at low TP. We also found lower oxygen saturation in the nutrient-rich FL lakes than in the DK lakes, suggesting lower net ecosystem production in the FL lakes. We discuss our results within the framework of climate warming.
Within-lake habitat heterogeneity mediates community response to warming trends
Climate change is rapidly altering many aquatic systems, and life history traits and physiological diversity create differences in organism responses. In addition, habitat diversity may be expressed on small spatial scales, and it is therefore necessary to account for variation among both species and locations when evaluating climate impacts on biological communities. Here, we investigated the effects of temperature and spatial heterogeneity on long-term community composition in a large boreal lake. We used a five-decade time series of water temperature and relative abundance of fish species captured in the littoral zone throughout the summer at 10 discrete locations around the lake. We applied a spatial dynamic factor analysis (SDFA) model to this time series, which estimates the sensitivity of each species to changing water temperature while accounting for spatiotemporal variation. This analysis described the trend in community composition at each sampling location in the lake, given their different trends in temperature over time. The SDFA indicated different magnitude and direction of species responses to temperature; some species increased while others decreased in abundance. The model also identified five unique trends in species abundance across sites and time, indicating residual dynamics in abundance after accounting for temperature effects. Thus, different regions in the lake have experienced different trajectories in community change associated with different rates of temperature change. These results highlight the importance of considering habitat heterogeneity in explaining and predicting future species abundances, and our model provides a means of visualizing spatially-explicit temporal variation in species' dynamics.