Structuring features of lake districts: landscape controls on lake chemical responses to drought

Abstract

1. Within a lake district of relatively homogeneous geomorphology, the responses of lakes to climate are influenced by the complexity of the hydrogeologic setting, position in the landscape, and lake‐specific biological and physical features. We examined lake chemical responses to drought in surface water‐ and groundwater‐dominated districts to address two general questions. (1) Are spatial patterns in chemical dynamics among lakes uniform and synchronous within a lake district, suggesting broad geomorphic controls; variable in a spatially explicit pattern, with synchrony related to landscape position, suggesting hydrologic flowpath controls; or spatially unstructured and asynchronous, suggesting overriding control by lake‐specific factors? (2) Are lake responses to drought a simple function of precipitation quantity or are they dictated by more complex interactions among climate, unique lake features, and hydrologic setting? 2. Annual open‐water means for epilimnetic concentrations of chloride, calcium, sulfate, ANC, DOC, total nitrogen, silica, total phosphorus, and chlorophyll a measured between 1982 and 1995 were assembled for lakes in the Red Lake and ELA districts of north‐western Ontario, the Muskoka – Dorset district in south‐central Ontario, and the Northern Highland district of Wisconsin. Within each district, we compared responses of lakes classified by landscape position into highland or lowland, depending on relative location within the local to regional hydrologic flow system. Synchrony, defined as a measure of the similarity in inter‐annual dynamics among lakes within a district, was quantified as the Pearson product‐moment correlation (r) between two lakes with observations paired by year. To determine if solute concentrations were directly related to interannual variations in precipitation quantity, we used regression analysis to fit district‐wide slopes describing the relationship between each chemical variable and annual (June to May) and October to May (Oct–May) precipitation. 3. Among lakes in each of the three Ontario districts, the pattern of chemical response to interannual shifts in precipitation was spatially uniform. In these surface water‐ dominated districts, solute concentrations were generally a simple function of precipitation. Conservative solutes, like calcium and chloride, tended to be more synchronous and were negatively related to precipitation. Solutes such as silica, total phosphorus, and chlorophyll a, which are influenced by in‐lake processes, were less synchronous and relationships with precipitation tended to be positive or absent. 4. In the groundwater‐dominated Northern Highland lakes of Wisconsin, we observed spatial structure in drought response, with lowland lakes more synchronous than highland lakes. However, there was no evidence for a direct relationship between any solute and precipitation. Instead, increases in the concentration of the conservative ion calcium during drought were not followed by a symmetrical return to pre‐drought conditions when precipitation ...

Landscape effects of climate, agriculture, and urbanization on benthic invertebrate communities of Canadian prairie lakes

“…7). We attribute this pattern to landscape differences in lake sensitivity to climate change or land use (cf., Webster et al 2000), rather than urbanization, because both Pasqua and Echo Lakes receive sewage, yet exhibit rates of community change similar to those seen in Buffalo Pound Lake.…”

Temporal Coherence of Chlorophyll a during a Spring Phytoplankton Bloom in Xiangxi Bay of Three‐Gorges Reservoir, China

“…Each off-diagonal value in this matrix represents the strength of the relationship between the temporal trajectories of chlorophyll a. Longitudinal gradient of nutrient and NVSS from the mouth to the headwater were tested by the regression analysis of concentrations and distance from the mouth. In order to characterize spatial heterogeneity in environmental characteristics, we calculated the relative difference indices (D x ) of environmental variable (DIN, DIP and NVSS) between sites as follow (modified from BAINES et al, 2000;FÖLSTER et al, 2005):…”

“…GEORGE et al (2000) examined the extent to which year-to-year variations in the physical, chemical and biological characteristics of five lakes varied synchronously over a 30 ~ 40 year period. WEBSTER (2000) found that chlorophyll a, which are influenced by in-lake processes, were less synchronous. However, phytoplankton populations respond so rapidly and sensitively to their environment that conventional sampling methods fail to obtain more subtle and interesting aspects of the controlling mechanisms of phytoplankton growth.…”

“…In lake research and management, chlorophyll a is the most commonly used surrogate for phytoplankton biomass, and it is a good indicator of algal blooms (DILLON and RIGLER, 1974;MAZUMDER and HAVENS, 1998;WETZEL, 2001;AN and PARK, 2002;PHILLIPS et al, 2008). Temporal dynamics of chlorophyll a is of great interest for water quality and resource management (BAINES et al, 2000). Some researchers pointed out that the phytoplankton growth in oligotrophic waters is usually assumed to be mainly influenced by the nutrient availability, whereas in eutrophic ones the effects of environmental conditions determined by climate are much more decisive (e.g., REYNOLDS and BELLINGER, 1992;HORN, 2003).…”

“…For instance, BAINES et al (2000) demonstrated a high level of temporal coherence for temperature, calcium, and chlorophyll a in lakes of Northern Wisconsin and suggested the usefulness of selected lakes to predict the regional effects of climatic variability on aquatic ecosystems. GEORGE et al (2000) examined the extent to which year-to-year variations in the physical, chemical and biological characteristics of five lakes varied synchronously over a 30 ~ 40 year period.…”