About the project
The project is investigating whether the dredging of the mouths of the Toby and Solf rivers has had far-reachingeffects on water quality, zooplankton and the microbial community in the area. Several
sampling points in the Toby River and its estuary, as well as in Södra Stadsfjärden, will be included in
the project. In addition, the project will investigate whether metal concentrations in the water in the area
remain high following the dredging. Zooplankton abundance is being studied in the project because they
constitute an important food source for fish fry. Zooplankton communities also change in response to various environmental changes,
e.g. acidification and high metal concentrations, and therefore provide information on the effects of different types of
environmental disturbances. Chlorophyll levels are being investigated both as an indicator of potential eutrophication
and as a measure of the amount of food available to zooplankton. The microbial community is examined to
determine whether the water, like the dredged material and the surrounding fields with acidic
sulphate soils, is dominated by acidophilic bacteria.
To monitor water quality, field measurements are carried out, and water samples are taken for further
analysis. Chlorophyll samples are also taken as an indicator of eutrophication levels and the amount of food available
for zooplankton. Zooplankton are studied because they are an important food source for predatory fish fry, e.g.
pike and perch, and because they are sensitive to acidic and metal-rich water.
Microbial populations are a key factor in the biogeochemical processes in both the water phase and
sediments and directly influence water quality by determining which substances are dissolved in
the water phase and which are bound to the sediment. To our knowledge, the microbial communities in the Toby River and Södra
Stadsfjärden have never been studied.
The aim of the project is to increase knowledge of the state of the aquatic ecosystem at the mouth of the Toby River and
Södra Stadsfjärden approximately seven years after dredging was completed, and to investigate the conditions
for once again strengthening the status of fish stocks.
Project goal
The aim of the project is to improve our understanding of the state of the aquatic ecosystem at the mouth of the Toby River andin Södra Stadsfjärden approximately seven years after dredging was completed, and to investigate the potential
for improving the status of fish stocks.
UN's Sustainable Development Goals
Jonna Engström-Öst
Special Researcher