HR: 11:15h
AN: NB32D-04    [Abstracts]
TI: Does Climate Change Confound Lake Recovery?
AU: * Stendera, S
EM: Sonja.Stendera@ma.slu.se
AF: Department of Environmental Assessment, Swedish University of Agricultural Sciences P.O. Box 7050, Uppsala, SE-75007 Sweden
AU: Johnson, R K
EM: Richard.Johnson@ma.slu.se
AF: Department of Environmental Assessment, Swedish University of Agricultural Sciences P.O. Box 7050, Uppsala, SE-75007 Sweden
AB: Four acidified (pH < 6) and nine reference lakes have been sampled since 1988 for chemistry and benthic macroinvertebrates of the littoral, sublittoral and the profundal habitat. Many lakes showed positive trends in pH, reflecting recently decreasing SO4 deposition but negative trends in sublittoral and profundal species richness and diversity. Littoral species richness and diversity, however, increased in both lake types during this time period. In multiple stepwise regression TN, conductivity and NAOwinter index, and pH were the best predictors of species richness, diversity, and CA axis 1 scores against physico-chemical variables. The processes generating these patterns are unclear, but we speculate that decreasing conductivity and increasing water color indicating the influence of 'wet' years might increase allochthonous DOM inputs, which may negatively affect periphyton communities and in turn benthic macroinvertebrate richness and community composition. Positive phases of the NAO winter index bring warmer, wetter winters to Scandinavia, this may cause longer summer stratification, and thus an increase of hypolimnetic anoxia. Furthermore, a deeper thermocline in shallow lakes caused by warmer climate may particularly effect the sublittoral fauna due to e.g. enhanced nutrient turnover leading to internal eutrophication and thus lack of oxygen.
DE: 1620 Climate dynamics (3309)
DE: 1630 Impact phenomena
DE: 1845 Limnology
DE: 1871 Surface water quality
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly