4 Great Lakes - Temperate Biomes Temperate biomes are...

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Temperate BiomesTemperate biomes are characterized by four seasons, generally mild temperatures, and sufficient precipitation to support high rates of primary and secondary production - in the north temperate zone, one of the legacies of the last glaciation (the Wisconsinan, about 10,000 ya), is a tremendous number of lakes, many of which are located in the boreal forest we have been discussing- south of the boreal forest, these lakes are characterized by longer growing seasons, richer soils in the watershed, and complex systems of connecting rivers - these characteristics have resulted in productive lacustrine (lake) ecosystems that have provided rapidly growing human populations with water, food, transportation, energy, and recreation, as well as habitat for a tremendous diversity of flora and fauna - the Great Lakes have been integral to development of the north-central U.S., so let’s look at this lake system, and some of the conservation issues that have developed over the last century- 21% of world’s freshwater - Superior 2ndlargest lake in the world- max depth 407 m (1,335 ft)- 35,000 islands- 84% of U.S. freshwater- limnology similar to freshwater oceans- problems…SuperiorMichiganHuronGeorgian BayOntarioSt. Clair
The Great LakesThe Great Lakes basin covers 764,600 km2(295,200 mi2) and includes river and lake systems in 8 states and 2 provinces
The Great LakesDepth and hydrology vary considerably among lakes:Retention time: 191 yearsRT: 99 yearsRT: 22 yearsRT: 2.6 yearsRT: 6 yearsSuperiorMichiganHuronErieOntario
Great Lakes EconomicsThe economic value of the Great Lakes region is tremendous:- $4.7 trillion economic output in 2011, 28% of combined U.S. and Canadian activity- 4thlargest economy in the world if it was a country- 46 million jobs in the region, 29% of U.S. and Canadian workforce- 24% of U.S. exports in 2012, 38% of Canadian exports- transportation equipment, agricultural and food products, metals, chemicals- 160 million tons of cargo moved each year- 40% of Fortune 500 companies based in the region- $4 billion/year recreational fisheryHowever, this economic development has also resulted in:- widespread pollution; industrial release of DDT/DDE, dieldrin, lead, mercury, PCBs, dioxins, cadmium – considerable bioaccumulationand biomagnification- nutrients from agriculture and livestock production in the watershed – culturaleutrophication(increasing primary productivity)- sewage pollution and runoff from rapidly expanding urban areas; additional sources of eutrophication as well as disease- pervasive changes in the biotic community from bacteria to top-level carnivores- extinction of at least 5 fishes, declines in other speciesConservation strategies: 1) prevent, detect invasive species; 2) reduce stormwater runoff; 3) improve effectiveness of agricultural BMPs; and 4) improve stream connectivity
Great Lakes EutrophicationAlgae blooms resulting from eutrophication have caused widespread water quality problems in Lake Erie’s central basin - during summer stratification, high P loading → algal blooms → excessive decomposition hypoxia

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