[P-23] Phytoplankton and Zooplankton Communities in Swedish Lakes Covering a Gradient of
Inorganic Aluminum Concentrations
Presenter: Tobias Vrede, Swedish University of Agricultural Sciences, Department of Aquatic
Sciences and Assessment, Sweden, tobias.vrede@slu.se
Author(s): Tobias Vrede, Department of Aquatic Sciences and Assessment, Swedish University of
Agricultural Sciences, Sweden
Marcus Sundbom,Department of Environmental Science and Analytical Chemistry, Stockholm
University, Sweden
Labile inorganic aluminum (Ali) is highly toxic to many aquatic organisms. Different studies exhibit a range in
critical concentrations. This suggests that there is a complex relationship between Ali concentration and
toxicity, possibly modulated by TOC and F concentrations as well as pH. We also hypothesize that there are
differences in the responses on the species level. Here we present results on phytoplankton and zooplankton
community composition in 177 and 51 lakes, respectively, from the Swedish National Monitoring and ISELAW
(Integrated Studies of the Effects of Liming Acidified Waters) programs. These lakes have either measured or
modeled Ali concentrations and cover large ranges in annual median Ali, pH and TOC of <3-780 μg/L, 4.2-9.3
and 0.4-50 mg/L, respectively. The colonization pattern of plankton species and the response of phytoplankton
and zooplankton communities to long-term changes in Ali were investigated by time series analysis on 10
selected lakes with at least 15 years of plankton and chemistry data. These lakes have a median pH<6 and are
currently recovering from acidification as evident from positive trends in pH. To investigate the opposite
scenario, the changes in the plankton communities in response to increasing Ali concentrations were also
assessed in a few re-acidifying lakes where liming has been discontinued.
[O2C-2] Long-term effects of liming on fish in Swedish streams and lakes
Presenter: Kerstin Holmgren, Swedish University of Agricultural Sciences, Department of Aquatic
Resources, Institute of Freshwater Research, Drottningholm, kerstin.holmgren@slu.se
Author(s): Kerstin Holmgren, Erik Degerman, Björn Bergquist and Erik Petersson, Swedish University
of Agricultural Sciences, Department of Aquatic Resources, Institute of Freshwater Research,
Drottningholm
Thousands of Swedish lakes and rivers have been limed since 1977, at experimental scale until 1981, and then
increasing to a large-scale national management action. The annual amount of limestone spread peaked at
more than 200,000 tons during 1998-2002. As an adjustment to decreasing acidification, the amount of lime
decreased and recently stabilized at about 120,000 tons per year. Standard sampling of fish assemblages in
lakes and streams was an important part of monitoring the effects of liming. More than 1300 limed lakes were
sampled with multi-mesh gillnets (EN 14757), and electrofishing (EN 14011) was done at 1029 sites in 669
rivers where liming occurred in the upstream catchment. Data from large-scale fish monitoring were quality
assured and stored in nationally managed and publically accessible data bases, i.e. the National Register of
Survey test-fishing (NORS) and the Swedish Electrofishing Register (SERS). We show the importance of longterm liming of acidified streams and rivers, for slowly achieving positive effects on fish populations and
assemblages on a national scale. The proportion of limed stream sites with no fish decreased with time, and
after more than 16 years this proportion was not significantly different between limed sites and non-limed
reference sites with minimum pH > 5.4. Increasing trends were observed for species richness and for
proportion of sites with presence of young-of-the-year fish, and it took between 13-16 years and more than 20
years, to approach values observed at reference sites. Abundance of brown trout (Salmo trutta), perch (Perca
fluviatilis) and roach (Rutilus rutilus) increased at sites sampled both before and after liming. A similar national
evaluation of long-term effects of liming on fish of acidified lakes is needed, and we will indicate how
preconditions for evaluation differ between rivers and lakes.
[O7C-2] Status and trends in stream ecosystems in limed, acidic or neutral waters (benthic
diatoms, benthic fauna, fish)
Presenter: Cecilia Andrén, Stockholm University, cecilia.andren@aces.su.se
Author(s): Cecilia Andrén, Stockholm University, Björn Bergquist, Swedish University of Agricultural
Sciences and Amelie Jarlman, Jarlman Konsult AB,
While there are numerous studies of the effects of acidification and the mitigation by liming on water
quality, the biological effects and interactions are less well understood. The main focus in this study is
on status, trends and interactions in stream diatom, benthos and fish communities. Within ISELAW
(Integrated Studies of the Effects of Liming Acidified Waters) 42 acidic, neutral, limed or previously
limed Swedish streams have been monitored for 8-25 years. Water was sampled at least monthly,
sampling of benthic diatoms, benthos and electrofishing were performed every fall. Species
abundances and relevant biological indices were used to assess status and trends in the stream
communities, and their relationship to water quality, here represented by 12-month means of pH, Ca,
TOC and Al. Benthic diatoms were tightly correlated to water acidity (pH-ACID, Spearman’s rho 0.74).
Benthic fauna was less closely linked to water quality (pH-MISA, rho 0.50) and more to the habitat,
while brown trout showed the weakest correlation with water quality (pH-VIX, rho 0.35) but a stronger
relationship with habitat and hydro-morphology. Acidity (pH, Ca) distinguishes (Tukey’s HSD) acidic
streams from other stream categories, together with several biotic indices (NoT-diatoms; ACID; NoTEPT/-Plechoptera; MISA; VIX). TOC and Al differed among acidic, neutral or limed streams, as did the
diversity of benthic diatoms and fauna, Medin’s index, NoT-benthic fauna/-Ephemeroptera/Trichoptera, and abundance of YoY and older brown trout. There was no significant trend
(Kendall/Theil) for the whole dataset or for the different stream categories, and only a few significant
trends for individual streams.
The interactions in biota are further examined using multivariate ordination and clustering. A current
challenge is to adapt the liming strategies to the decreased acidification; mainly to sustain stream
communities comparable with those in reference streams and above all - when liming is stopped pass
on vital ecosystems.
[O1B-2] High quality long-term monitoring: Swedish experiences with assessments of surface
water acidification and recovery
Presenter: Jens Fölster, Swedish University of Agricultural Sciences, Jens.Folster@slu.se
Author(s): Jens Fölster, Martyn N. Futter, Richard K. Johnson and Anders Wilander, Swedish
University of Agricultural Sciences,
Surface water acidification and recovery are long term processes related to changing deposition but
confounded by climatic variation and land management including forestry. Credible trend assessment
needs long term, high quality time series with consistent collection, analysis and management
protocols so as to separate changes due to acidification from other sources of variation. The Swedish
example of 50 years of freshwater monitoring shows how such data can be obtained and can serve as
an example for surface water monitoring programs in other countries and regions.
The program started with strong cooperation between scientists and society to address pressing
concerns related to surface water eutrophication. When acidification came up as environmental issue
in the 1970s, it was apparent that the original focus on monitoring large lakes and river mouths had to
be widened to include smaller lakes and streams.
Today the program holds hundreds of time series of water chemistry with up to 50 years of continuous
data. Sampling, analysis and data storage have been performed by the same unit personnel
throughout the years. International scientific review helped to ensure program rigor and relevance.
Participation in international networks within e.g. UN-ECE LRTAP convention, has led to quality
improvements by laboratory inter-calibrations as well as cooperative publications in high ranked
journals. Open access to all data for both scientists and authorities has further contributed to
improving data quality and to comprehensive use of the data. Time series have been used to
demonstrate recovery from acidification and are an important resource for model calibration as well as
assessments of the effectiveness of emission control and liming programs.
Reference:
Fölster, J., R.K. Johnson, M.N. Futter, A. Wilander (2014). "The Swedish monitoring of surface waters:
50 Years of adaptive monitoring." Ambio 43: 3-18.