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Titolo:
POTENTIAL EFFECTS OF CLIMATE CHANGES ON AQUATIC SYSTEMS - LAURENTIAN GREAT-LAKES AND PRECAMBRIAN SHIELD REGION
Autore:
MAGNUSON JJ; WEBSTER KE; ASSEL RA; BOWSER CJ; DILLON PJ; EATON JG; EVANS HE; FEE EJ; HALL RI; MORTSCH LR; SCHINDLER DW; QUINN FH;
Indirizzi:
UNIV WISCONSIN,CTR LIMNOL,680 N PARK ST MADISON WI 53706
Titolo Testata:
Hydrological processes
fascicolo: 8, volume: 11, anno: 1997,
pagine: 825 - 871
SICI:
0885-6087(1997)11:8<825:PEOCCO>2.0.ZU;2-2
Fonte:
ISI
Lingua:
ENG
Soggetto:
FRESH-WATER ECOSYSTEMS; BOREAL FOREST; THERMAL HABITAT; YOUNGER DRYAS; SEEPAGE LAKE; PHYTOPLANKTON PHOTOSYNTHESIS; NORTHWESTERN-ONTARIO; NUTRIENT LIMITATION; SOUTHERN ONTARIO; AIR-TEMPERATURE;
Keywords:
LAURENTIAN GREAT LAKES; PRECAMBRIAN SHIELD; CLIMATE CHANGE; AQUATIC SYSTEMS; NORTH TEMPERATE GLACIAL LAKES; HYDROLOGY; PALEOCLIMATES; LAKE ICE; WATER LEVEL; PHYSICAL LIMNOLOGY; CHEMICAL LIMNOLOGY; PHYTOPLANKTON; ZOOPLANKTON; FISH; TERRESTRIAL-AQUATIC LINKAGES; INTERACTION WITH OTHER STRESSES; HETEROGENEITY IN RESPONSE; BIOGEOCHEMISTRY;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
219
Recensione:
Indirizzi per estratti:
Citazione:
J.J. Magnuson et al., "POTENTIAL EFFECTS OF CLIMATE CHANGES ON AQUATIC SYSTEMS - LAURENTIAN GREAT-LAKES AND PRECAMBRIAN SHIELD REGION", Hydrological processes, 11(8), 1997, pp. 825-871

Abstract

The region studied includes the Laurentian Great Lakes and a diversity of smaller glacial lakes, streams and wetlands south of permanent permafrost and towards the southern extent of Wisconsin glaciation. We emphasize lakes and quantitative implications. The region is warmer andwetter than it has been over most of the last 12000 years. Since 1911observed air temperatures have increased by about 0.11 degrees C per decade in spring and 0.06 degrees C in winter; annual precipitation has increased by about 2.1% per decade. Ice thaw phenologies since the 1850s indicate a late winter warming of about 2.5 degrees C. In future scenarios for a doubled CO2 climate, air temperature increases in summer and winter and precipitation decreases (summer) in western Ontario but increases (winter) in western Ontario, northern Minnesota, Wisconsin and Michigan. Such changes in climate have altered and would further alter hydrological and other physical features of lakes. Warmer climates, i.e. 2 x CO2 climates, would lower net basin water supplies, stream flows and water levels owing to increased evaporation in excess ofprecipitation. Water levels have been responsive to drought and future scenarios for the Great Lakes simulate levels 0.2 to 2.5 m lower. Human adaptation to such changes is expensive. Warmer climates would decrease the spatial extent of ice cover on the Great Lakes; small lakes,especially to the south, would no longer freeze over every year. Temperature simulations for stratified lakes are 1-7 degrees C warmer for surface waters, and 6 degrees C cooler to 8 degrees C warmer for deep waters. Thermocline depth would change (4 m shallower to 3.5 m deeper)with warmer climates alone; deepening owing to increases in light penetration would occur with reduced input of dissolved organic carbon (DOG) from dryer catchments. Dissolved oxygen would decrease below the thermocline. These physical changes would in turn affect the phytoplankton, zooplankton, benthos and fishes. Annual phytoplankton production may increase but many complex reactions of the phytoplankton communityto altered temperatures, thermocline depths, light penetrations and nutrient inputs would be expected. Zooplankton biomass would increase, but, again, many complex interactions are expected. Generally, the thermal habitat for warm-, cool- and even cold-water fishes would increase in size in deep stratified lakes, but would decrease in shallow unstratified lakes and in streams. Less dissolved oxygen below the thermocline of lakes would further degrade stratified lakes for cold water fishes. Growth and production would increase for fishes that are now in thermal environments cooler than their optimum but decrease for those that are at or above their optimum, provided they cannot move to a deeper or headwater thermal refuge. The zoogeographical boundary for fishspecies could move north by 500-600 km; invasions of warmer water fishes and extirpations of colder water fishes should increase. Aquatic ecosystems across the region do not necessarily exhibit coherent responses to climate changes and variability, even if they are in close proximity. Lakes, wetlands and streams respond differently, as do fakes ofdifferent depth or productivity. Differences in hydrology and the position in the hydrological flow system, in terrestrial vegetation and land use, in base climates and in the aquatic biota can all cause different responses. Climate change effects interact strongly with effects of other human-caused stresses such as eutrophication, acid precipitation, toxic chemicals and the spread of exotic organisms. Aquatic ecological systems in the region are sensitive to climate change and variation. Assessments of these potential effects are in an early stage and contain many uncertainties in the models and properties of aquatic ecological systems and of the climate system. (C) 1997 by John Wiley B Sons, Ltd.

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Documento generato il 04/12/20 alle ore 19:40:55