Widespread Effects of Climatic Warming on Freshwater Ecosystems in North America

Abstract

Freshwaters in dierent regions show many similarities and dierences in their responses to climatic warming. Bases for comparison include reports from regional committees, long-term records for several sites where climate has warmed in the past two decades and other human alterations to freshwaters that simulate some of the expected results of climatic warming, such as reservoir construction. Palaeoecological studies of freshwaters under climatic warming and dierences in communities under dierent climatic regimes are also considered. Major changes in the physical, chemical and biological characteristics of lakes occur. Many of the changes to lakes and streams are the result of strong eects of climatic warming on terrestrial catchments. Inputs from catchments can be either dampened or ampli®ed by in-lake processes, in some cases causing counter-intuitive responses, such as the acidi®cation of streams but alkalinization of lakes in areas where supplies of base cations are limited. Consideration of land±water interactions and interactions between climatic warming and other human stresses are important for the accurate prediction of the eects of climatic change.

Long-term trends of chemical and modelled photochemical parameters in four Alpine lakes

“…Alkalinity is largely affected by climate change, particularly in softwater lakes (Schindler, 1997;Sommaruga-Wögrath et al, 1997;Koinig et al, 1998). Changes in alkalinity may involve the temperatureenhanced dissolution of CaSO 4 , where Ca 2+ can be up-taken, but it is not transformed by biota, while SO 4 2− is biologically transformed into organic sulphur compounds with consumption of H + .…”

“…Changes in alkalinity may involve the temperatureenhanced dissolution of CaSO 4 , where Ca 2+ can be up-taken, but it is not transformed by biota, while SO 4 2− is biologically transformed into organic sulphur compounds with consumption of H + . The latter induces, for example, enhanced dissolution of carbon dioxide into the surface lake water layer (Schindler, 1997). For example, in reaction (1), R-H is an organic compound and R-SH is a mercaptan, and several H + ions are consumed in the relevant transformation.…”

“…Changes in DOC concentration are important because they affect the penetration of sunlight (and most notably of UV radiation) into the water column (Laurion et al, 2000), as well as several other processes including photochemical reactions (Schindler, 1997).…”

Trends in Research on the Possible Effects of Climate Change Concerning Aquatic Ecosystems With Special Emphasis on the Modelling Approach

“…Several studies draw attention to the negative effects of climate change on fish (Rahel et al 1996;Schindler 1997;Stefan et al 2001). Many studies are run on themostly harmful -consequences of climate change on the water quality of freshwater ecosystems, habitat of fish, fish communities and fishery exploitation.…”

“…There have been some articles summarizing our knowledge on the possible effects of climate change on aquatic habitats in general (Carpenther et al 1992, Schindler 1997). The Pew Center (Poff et al 2002) has summarized such results for the U.S. by presenting several case studies for all types of freshwater and marine ecosystems.…”