Effects of Liming on the Aquatic Fauna in a Norwegian Watershed: Why Do Crustaceans and Fish Respond Differently? |
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Authors: | Trygve Hesthagen Bjørn Walseng Leif Roger Karlsen Roy M Langåker |
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Institution: | 1. Norwegian Institute for Nature Research, Tungasletta 2, N-7485, Trondheim, Norway 2. Norwegian Institute for Nature Research, Gaustadallèen 21, N-0349, Oslo, Norway 3. ?stfold County Council, Environmental Administration, P. O. Box 325, N-1502, Moss, Norway 4. Directorate for Nature Management, Tungasletta 2, 7485, Trondheim, Norway
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Abstract: | We studied the effects of liming on fish and crustaceans in a watershed which is in a region known to have one of the highest
diversity of aquatic biota in Norway. This watershed, Enningdal, is shared between Norway (1/3) and Sweden (2/3) and includes
61 lakes > 1.0 ha in Norway. Liming started on a large scale in the 1980s. Currently, a total of 26 of lakes (43%) are limed,
covering 93% of the total lake area. The mean value ± S.D. of pH and the concentration of inorganic labile Al in these lakes
is 6.62 ± 0.35 and 3 ± 4 μg l−1, respectively. Historical data of fish communities have been obtained from surveys, while test-fishing and sampling of crustaceans
were conducted in 24 lakes in recent years (2002–2004). The present study shows that crustaceans to a greater extent than
fish has responded to improved water quality after more than 20 years of liming. Of a total of 120 fish populations, 42 (35%)
have gone extinct. Only five of the lost fish populations (12%) have been re-established, all due to human re-introductions.
Physical barriers are considered to be the main factor preventing fish from invading limed lakes. In contrast, crustaceans
have been re-established in most limed lakes. This may be mainly due to their good spreading capacity. However, they might
also have survived in refuges within the watershed, or as resting-eggs in the sediment. |
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Keywords: | acidification liming recovery rate crustaceans fish |
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