Sammendrag
Cladocera
Copepoda
Zooplankton
Road salt
Acidification
Indicators
Numerous boreal lakes across the Northern Hemisphere recovering from acidification are experiencing a simultaneous
increase in chloride (Cl) concentrations fromroad salting. Increasing Clmay have profound effects on the
lake ecosystem. We examine if an increase in Cl from road salting has modified the recovery of the
microcrustacean community in an acidified boreal lake undergoing chemical recovery (study lake). Results
from the study lake were compared with an acidified “reference lake”. The community changed during the
study period in the study lake mainly driven by the reduction in acidification pressure. Despite the community
changes and an increase in species richness, the absence of several acid sensitive species, previously occurring
in the lake, indicates a delayed biological recovery relative to the chemical recovery.Moreover, changes in occurrence
of acid sensitive and acid tolerant species indicated that the biological recovery was slower in the study lake
compared to the “reference”. Although recurrent episodes of high aluminum and low pH and decreasing Ca are
likely important factors for the delay, these do not explain, for instance, the shift from Cyclops scutifer to Bosmina
longispina in the study lake. Although the contribution of Cl was not significant, the correlation between Cl and
the variation in microcrustacean community was twice as high in the study lake compared to the “reference”.
We argue that small, sheltered forest lakes may be especially sensitive to increased Cl levels, through changes
in pattern of stratification, thus providing amechanism for the shift fromC. scutifer to B. longispina. The reduction
of the acidification pressure seems to override the Cl effects on microcrustaceans at low Cl levels in salt-affected
lakes recovering fromacidification. However, prognoses for growing traffic and increasing road salting raise concern
for many recovering lakes located in proximity to roads and urbanized areas.
© 2014 Elsevier B.V. All rights reserved.
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