Abstract
The brackish-water Lake Vargsundet (SW Finland) was affected by multiple algal toxins and extensive fish mortality in July 1997. Dense populations of the ichthyotoxic haptophyte Prymnesium sp. and the hepatotoxic cyanobacterium Planktothrix agardhii were observed simultaneously, but usually in distinct layers. Fish died in the relatively clear epilimnion where 10-40 million Prymnesium cells per litre were recorded (chlorophyll a range 6-18 μg l-1). Fish survived in the metalimnion dominated by the hepatotoxic P. agardhii (chlorophyll a 20-40 μg l-1). The deeper layers were anoxic. The Prymnesium-rich water remained ichthyotoxic until the end of August but the toxicity was less marked in tests with Artemia salina. As even inconspicuous haptophyte blooms with low chlorophyll a concentrations may be harmful, safety and monitoring issues need reconsideration.
| Original language | English |
|---|---|
| Pages (from-to) | 109-120 |
| Number of pages | 12 |
| Journal | Hydrobiologia |
| Volume | 397 |
| DOIs | |
| Publication status | Published - 1999 |
| MoE publication type | A1 Journal article-refereed |
Funding
We thank the Åland water authorities, especially Mr Carl Storå for arranging financial support. A grant from the Maj and Tor Nessling Foundation to J. M. is also acknowledged. Mr Svante Wistbacka assisted greatly in organizing the test fishing. We thank the staff of the Husö Biological Station and the Åbo Akademi University for excellent working facilities.
Keywords
- Fish kill
- Microcystin
- Planktothrix
- Prymnesin
- Prymnesium
- Toxic algae
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