tailieunhanh - Lake Trout Ecosystems in a Changing Environment - Chapter 8

Carbon hữu cơ hòa tan như là một kiểm soát biến trong hồ cá hồi và hồ khiên phương bắc khác Hồ cá hồi sông hồ trên Shield phương bắc thường tương đối rõ ràng (Martin và Olver, 1976; Johnson et al, 1977; Marshall và Ryan, 1987). Bảy mươi phần trăm lớn Secchi độ sâu hơn 4 m (Hình ). Minh bạch trong Lá chắn hồ là thường phần lớn được xác định bởi nồng độ chất hữu cơ hòa tan (thường được gọi là DOC, hoặc giải thể carbon hữu cơ, cho nó thường được định lượng bằng cách đo hàm lượng của nó) (Schindler, 1971; Hình. | chapter eight Dissolved organic carbon as a controlling variable in lake trout and other Boreal Shield lakes David w. Schindler Department of Biological Sciences University of Alberta John M. Gunn Ontario Ministry of Natural Resources Laurentian University Contents Introduction The effect of DOC on the physical properties of lakes The effect of DOC on the chemical properties of lakes The effect of DOC on biological properties of lakes Human activities that affect DOC Local influences Acid rain Climate warming Recommendations Acknowledgments References Introduction Lake trout lakes on the Boreal Shield are usually relatively clear Martin and Olver 1976 Johnson et al. 1977 Marshall and Ryan 1987 . Seventy percent have Secchi depths greater than 4 m Figure . Transparency in Shield lakes is usually largely determined by the concentration of dissolved organic matter usually called DOC or dissolved organic carbon for it is usually quantified by measuring its carbon content Schindler 1971 Figure much of which originates from decomposing vegetation in wetlands and forest soils. Fulvic and tannic acids are important components of DOC imparting a yellowish-brown color to the lakes and streams Schindler 1998 . However most lake trout lakes 2004 by CRC Press LLC 100 90 80 70 60 50 40 30 20 10 73 55 32 n 2103 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 Secchi Depth m Figure Secchi depth m in lake trout lakes of eastern North America. From data compiled for text edited by Gunn Steedman and Ryder 2003 . Figure DOC concentrations mg L in lake trout lakes of eastern North America. From data compiled for text edited by Gunn Steedman and Ryder 2003 . contain enough DOC to have important effects on optical chemical physical and biological properties Schindler et al. 1997 . For example over 80 of lake trout lakes have DOC concentrations 3 mg L-1 Figure a range where DOC attenuates enough light to reduce photosynthesis and block UV radiation. The most colored lake .