Press release 2014-06-10 at 7:37
Alexandrium ostenfeldii © Daniel Eriksson
A peculiar optical phenomenon, a turquoise glow of the sea in late summer nights, has increasingly raised the attention of residents, vacationers and local fishermen of coastal areas around the Baltic Sea. The phenomenon, called bioluminescence, is caused by dense blooms of Alexandrium ostenfeldii, a toxic dinoflagellate alga, which emits light upon mechanical stimulation.
The toxins produced by A. ostenfeldii belong to the group paralytic shellfish toxins (PSTs), and accumulate in shellfish and fish. This occurs in similar manner as with liver toxins. When consumed contaminated seafood can cause hazards to humans. In the Baltic Sea A. ostenfeldii is common in shallow coastal areas, at the Finnish coast it has been found in the Åland and Tammisaari archipelagos.
Ecology of the species and variation of the toxin content in the waters of Föglö, Åland, has been studied by SYKE since 2007, including also measurements of toxin content in the surrounding biota. Results from these studies have recently confirmed the research group´s hypothesis that the toxins will accumulate in the food web. Experiments made with caged blue mussels showed that mussels accumulate PST toxins during blooms of
A. ostenfeldii.
Toxins were also detected in natural bivalve communities at the bloom site, the highest toxin concentrations being found in very small bivalves, Cerastoderma glaucum individuals, exceeding the EC safety limit for shellfish consumption. Relatively high total toxin concentrations were also detected from some fish species, but mainly from the viscera. Only traces of toxins were detected from the flesh of fish (perch).
The blooms of A. ostenfeldii in the northern Baltic Sea do not pose a hazard to humans. SYKE advises a precautionary task not to offer whole fish collected from A. ostenfeldii bloom areas as feed for domestic animals like cats and dogs during times of heavy A. ostenfeldii blooms. At present only few areas have been identified as areas for A. ostenfeldii mass occurences. One well known and studied area is situated in Föglö, Åland.
The finding of toxins in cultured blue mussels and natural marine biota may however have implications for commercial mussel farming that has been advocated as a measure against nutrient loading and is already realized in the archipelago sea (HS 23.8. 2013). Saxitoxins are extremely toxic and any risk of toxin transfer should be avoided. Large scale mussel farming (producing animal feed) in an area with PST producing A. ostenfeldii (or other toxic species) are present and form blooms needs to be regulated and observed/monitored in order to be safe.
New sensitive and cost-efficient monitoring approaches for the detection of PSTs from the water are presently being developed and tested by SYKE scientists in collaboration with the Universities of Turku and Helsinki.
The research group in SYKE is interested in all observations of bioluminescence again this summer. The phenomenon is visible usually around one hour after sunset. When water is agitated by boating for example, it promotes bioluminescence of the cells, which is seen as bright turquoise color.
You can report observations of bioluminescence to the SYKE Marine Research Centre Algae Service number 0295 251 373 on Mon-Fri at 13:00-15:00.
More information
Researcher Outi Setälä, SYKE Marine Research Centre tel +358 295 251 635
Project leader Ankere Kremp SYKE Marine Research Centre tel +358 295 251 320