Persson, Gunnar
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
Abstract
Taxonomic composition and variation in density of zooplankton were studied since 1989 to investigate possible long-term effects of anthropogenic acidification and liming in Sweden (the Integrated Studies of the Effects of Liming in Acidified Water (ISELAW) programme). In the programme, 15 long-term (18-31 years) limed lakes were studied in parallel with 8 untreated circumneutral lakes (representing target conditions) and 7 acid lakes. Five-year means from these lakes were used to evaluate differences between the three lake groups. Water chemistry (including trace metals), phytoplankton, invertebrate predators and fish were also monitored. Older records from 8 of the limed lakes obtained during the acid period preceding the initial liming were compared with records from the limed period. The number of taxa more than doubled in 6 lakes after liming. Total present-day zooplankton biovolume showed insignificant differences between the neutral and limed groups, i.e., conformed with the target conditions. Trace metals, including inorganic aluminium, appeared in low concentrations in limed and neutral lakes whereas zooplankton in one acid lake was Al-intoxicated. Daphnid populations in 4 other lakes may suffer from effects of high Cd or Cu concentrations. "Bottom-up" regulation of the zooplankton biovolumes was indicated by positive regressions between total phosphorus-phytoplankton and phytoplankton-zooplankton. Corresponding tests showed no "top-down" regulation of zooplankton by fish and of phytoplankton by zooplankton. Biornasses of planktivorous fish were higher in the neutral reference lakes than in both the acid and the limed lake groups, but neither zooplankton density and biovolume nor mean body size were lower in the neutral references. A higher production and turnover of zooplankton in neutral reference lakes may explain similar densities and structure of zooplankton in spite of a heavier predation pressure. (c) 2007 Elsevier GmbH. All rights reserved.
Keywords
zooplankton; acidification; liming; oligotrophication; aluminium; metals; pelagic fish; planktivores
Published in
Limnologica
2008, volume: 38, number: 1, pages: 1-13
Publisher: ELSEVIER GMBH, URBAN & FISCHER VERLAG
SLU Authors
UKÄ Subject classification
Fish and Aquacultural Science
Publication identifier
- DOI: https://doi.org/10.1016/j.limno.2007.07.004
Permanent link to this page (URI)
https://res.slu.se/id/publ/78150