| The overall objective of this project is to determine the importance of algal blooms for transporting persistent organic pollutants (POPs) into aquatic food webs. Many POPs are hydrophobic and preferentially sorb to organic matter such as algae instead of being dissolved in the water. The fate and transport of POPs in the aquatic environment are thus highly linked to the fluxes of organic matter, such as the strong sedimentation events occurring during algal blooms. The enrichment of pollutants in sediments and the subsequent uptake by benthic fauna will result in enrichment also at higher trophic levels, which can lead to disturbingly high levels in top consumers, for instance fish.
The specific objectives of the project are:
1) To quantify the sorption of various POPs to different algal species, and the effect this sorption has on pollutant levels in the water column and in sediment during and after an algal bloom. Different algal species are likely to differ not only in sorbing properties, but also in propensity to sediment to the lake/sea floor.
2) To investigate the fate of the pollutants as algae settle at the sediment floor, i.e. to what extent the pollutants are incorporated into benthic fauna instead of retained in sediment or remobilized to the water column.
3) To determine the trophic transfer of the algal-associated pollutants to higher trophic levels (fish).
This project combines field studies in Lake Ekoln/Lake Mälaren with ecosystem modelling to determine the sorption of POPs to algae and the subsequent trophic transfer. Areas differing in primary productivity will be compared. The target pollutants are PCBs, flame retardants and fluorinated compounds. They are all substances of concern in Swedish waters. They cover a range of hydrophobicities and also differ in other physicochemical properties, which will enable a detailed study on the sorption and trophic transfer.
The work will be carried out during 2014. The main applicant will be responsible for the project and conduct the majority of the sampling, laboratory and modelling work, but will cooperate with other researchers at the Department of Aquatic Sciences and Assessment, SLU, and at the University of Jyväskylä, Finland.
The project is expected to result in new knowledge on the mechanisms of pollutant transport into aquatic food webs, and on the effects on pollutant transport of changing algal bloom patterns due to changes in nutrient status of the waters.
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