Appendix I. Summary of conclusions from papers from the Lake Vänern Symposium (SOLVE)
published in Aquatic Ecosystem Health & Management, 17(4), 2014.
State of Lake Vänern Ecosystem
Lake Vänern: A historical outline (Drotz et al., 2014)
The landscape around Lake Vänern was shaped into its present form during the latest
glaciations some 10,000 years ago. Large variation exists in its tributaries, with forest in the
north and agricultural areas in the south. Human influence on the landscape was relative small
until the mid-18th Century. Later, in the mid-19th Century, the agriculture, forestry, and shipping
industries underwent large transformations as the towns around the lake grew and the economy
changed. Development of fishing equipment, processes, and changes in catching methods
industrialized the fishing industry after mid-20th Century. In the 1960s the lake was considered
to be one of the most heavily mercury-polluted lakes in the world. After the passing of the first
national environmental protection law in Sweden the lake turned into a success story: it has been
declared to be healthy. However, old pollution still affects the fishing industry. With this new
focus on the environment, the scientific community started to be interested in the lake. The lake
has also played a very important role as the largest hydropower reservoir in Sweden. Here, too,
the environmental question is in focus and the effects of the water regulation are still under
debate. The result has been loss of biodiversity and an increased risk of an inflow of invasive
species from international shipping.
Sustainability aspects of water regulation and flood risk reduction in Lake Vänern (Nyberg
et al., 2014).
There are different interests in relation to water level regimes of Lake Vänern. From a
flood protection perspective (risks around the lake and downstream to Gothenburg) a low and
stable water level is beneficial. For shipping and hydropower, a stable medium-high water level
is wanted, whereas from an ecosystem and landscape development perspective larger water level
amplitudes are optimal. One out of a few reasons for this is the need to prevent a massive
increase in vegetation in coastal areas.
Increasing algal biomass in Lake Vänern despite decreasing phosphorus concentrations – a
lake-specific phenomenon? (Weyhenmeyer and Broberg, 2014)
In Lake Vänern total phytoplankton biomass has significantly increased since the 1980’s at
the same time as total phosphorus and inorganic nitrogen concentrations have significantly
decreased, and long-term data from 13 small oligotrophic reference lakes revealed the same
pattern. Decreasing acidity in combination with increasing water temperatures has been more
important for phytoplankton growth than total phosphorous and nitrogen concentrations.
Has climate variability driven the trends and dynamics in recruitment of pelagic fish
species in Swedish lakes Vänern and Vättern in recent decades? (Sandström et al., 2014a)
1
The inter-annual variation in recruitment of both Smelt (Osmerus eperlanus) and Vendace
(Coregonus albula) was considerable. Recruitment appeared to be more affected by biotic
factors in Lake Vättern and more by abiotic factors in Lake Vänern.
A test of sampling methods for fishes in the littoral zone of Lake Vänern, Sweden
(Sandström et al., 2014b)
Three sampling methods (electrofishing, detonation and multi-mesh gillnet) were
compared in a shallow area of Lake Vänern, with slightly different results for the number of
species caught and their densities. These results demonstrate that the method used for sampling
will affect the sampling result, and the use of standardized methods is essential for achievement
of comparable results.
Atlantic Salmon and Brown Trout in Lake Vänern: A proposal for a co-management
system (Bergman et al., 2014)
Ecosystem-based management is a possible way towards sustainability, co-management
seems to be a natural way to implement it. Four major barriers were identified: 1) ecosystem
borders and state/county borders are rarely the same; 2) different stakeholders have different
needs and perspectives; 3) coordinating the monitoring that is needed for salmonids with their
complex life cycle in a large ecosystem is difficult and expensive; and 4) it is difficult to attract
adequate funding. Further, we argue that by using Atlantic Salmon and Brown Trout as example
species we show the full complexity of the problem, as these species need both river and lake
habitat to complete their life cycle.
Can multi-frequency acoustics improve the monitoring of large zooplankton in large
temperate lakes? (Ragnarsson-Stabo et al., 2014)
Developing combined, integrated monitoring of fish, mysids and zooplankton would
substantially improve the potential to accurately assess the interactions among the main organism
groups in pelagic ecosystems of large temperate lakes. This will require modifications of the
procedures for hydro-acoustics (day-night, multi-frequency use).
State of Great Lakes ecosystem
Management of Great Lakes Fisheries: Progressions and Lessons (Minns, 2014)
Research over the last 50 years on the Laurentian Great Lakes can be summarized in the
following points:




A whole ecosystem view is essential, and in particular for fisheries.
Keep monitoring, since wise management depends on continuous input of information.
Beware of the inertia of cumulative impacts, since the accumulated impacts and pressures
of past actions always weigh heavily on the present.
We are rehabilitating not restoring ecosystems, and the ecosystem may not recover
completely to their pristine state.
2



Strive to involve all of society, and be aware of stakeholders with conflicting interests
and hidden agendas.
Beware of shifting baselines. Today most people have less contact with natural
ecosystems and their conditions in the past.
Be actively adaptive, since the opportunities to run controlled experiments are limited,
adaptive management may be an alternative approach.
Ecosystem-based management is forever, and the three guiding principles should be:
1. No net loss of the natural productive capacity of ecosystems
2. No net loss of the biological diversity of ecosystems
3. No net loss of the potentially utilizable productivity of natural ecosystems
Relative Comparison and Perspective on Invasive Species in the Laurentian and Swedish
Great Lakes (Nalepa, 2014).
While responses to reduced input of nutrients (P) and pollutants (Hg) have been similar in
most lakes, the responses to invasive species have differed.
A comparison of invasive taxa between the Laurentian Great Lakes and Lake Vänern
showed an approximately ten-fold higher number of exotic taxa of plants, invertebrates, fish and
the combined taxa of bacteria, virus, flukes, fungi etc. in the Great Lakes. For mammals and
birds it was the opposite with one of each in Vänern and none in the Great Lakes.
A dedicated long term monitoring is essential both for understanding and measures.
Many recent introductions of non-treatable species have been by ballast water.
The Laurentian Great Lakes in transition: A chronicle of research at the base of the
foodweb (Munawar et al., 2014).
The Laurentian Great Lakes, including Superior, Michigan, Huron, Erie and Ontario are an
enormous fresh water resource shared by Canada and the United States. Efforts to protect the
lakes from cultural eutrophication and other pollutants led to an international treaty, the Great
Lakes Water Quality Agreement, in 1972. Much of the scientific and policy rationale behind the
treaty can be attributed to Drs. R.A. Vollenweider (phosphorus abatement) and J.R. Vallentyne
(the ecosystem approach). The paper chronicles the evolution of phytoplankton, primary
productivity and microbial food web research in the Great Lakes and offers lessons that can be
applied to the management of large lake ecosystems throughout the world. These lessons
include both spatially and temporally intensive sampling programs in addition to structural and
functional assessments of the microbial – planktonic food web.
International management and agreements
Progress towards the implementation of the European Water Framework Directive (2000 –
2012) (Phillips, 2014)
3
The European Water Framework Directive (WFD), which came into force in 2000,
introduced a system of river basin management which required member states (MS) to develop a
range of new biological assessment systems to determine the status of Europe’s surface waters.
Although it is desirable to align status class boundaries to significant changes of ecological
status, so that the resulting classifications can be linked to ecosystem function, many methods
simply divide status into five equal classes along a pressure gradient. An exception was the
approach used for lakes, where a greater understanding of the impacts of eutrophication has been
established. Here, boundaries were derived from the likelihood of undesirable disturbances
caused by the secondary impacts of eutrophication.
Aquatic ecosystems across boundaries: Significance of international agreements and
cooperation (Dave and Munawar, 2014)
Research on large lakes requires special considerations for reasons described below:







A scientifically-sound sampling program must evaluate a great number of sampling
stations
Large size means slow response to environmental impacts. This also implies that
response to environmental management is slower than for smaller lakes.
Large lakes may have higher species diversity than smaller lakes with more complex
food webs. This implies that a stress on one part of the food web can affect the entire
food web, and therefore species other than those affected directly. A variety of experts
may be needed to fully evaluate the food web.
Large lakes are often regulated for boat traffic and hydroelectricity. These manipulations
may affect immigration of invasive species, the impacts of which are difficult to predict
and control.
Regulations for hydroelectricity will not only affect fish migration but also river gravel
size (spawning substrate), shore erosion and vegetation, which will also affect spawning
of many fish species.
Furthermore, since large lakes (or their watersheds) are generally shared by more than
one nation, they require international co-operation both for scientific monitoring and
research (with standard methods) to understand the whole ecosystem. Co-operation is
also necessary for environmental management and regulatory action for maintaining
ecosystem function.
A large lake and its watershed may be regulated by laws at the international, national,
provincial and municipal level. Representatives need to be empowered to make decisions
and have the capacity to carry out assigned initiatives. Local actors are more susceptible
to political pressure especially where there is no overarching provincial or national
standard to be met. Jurisdictional fragmentation leads to confusion as to who is to play
what role and to what degree of responsibility (Norman and Bakker, 2013). Effective coordination and co-operation between these governments is essential if the system is to
achieve good health status.
4