Summary

High levels of the toxic, brominated substances; hydroxylated polybrominated diphenyl ethers (OH-PBDEs), methoxylated polybrominated diphenyl ethers (MeO-PBDEs), and 2,4,6-tribromophenol (2,4,6-TBP) have been found in Baltic biota with levels fluctuating over seasons. A growing body of evidence is pointing towards filamentous algae as a natural producer of these chemicals. However, conclusive scientific evidence supporting this hypothesis is lacking and why such production occurs has not comprehensively been addressed. This pilot study, carried out with a limited set of replicates reveals a production of 6-OH-BDE47, 6-OH-BDE137, and 2,4,6-TBP in the filamentous alga,

Ceramium tenuicorne, a common red alga both in the Baltic Sea and in temperate waters. When exposed to grazing or strong light, monocultures of the female marine clone of C. tenuicorne tended to produce elevated levels of 2,4,6-TBP compared to undamaged controls. When exposed to increased levels of salinity, monocultures of the female brackish clone of C. tenuicorne tended to produce elevated levels of 2,4,6-TBP compared to undamaged controls. Algae collected from the Swedish east coast also tended to produce higher levels of 2,4,6-TBP than algae collected from the west coast. From field collected material, a seasonal variation with a peak of OH-PBDEs, MeO-PBDE, and TBP concentrations in July- August could also be detected.

The results of this study open up for further studies regarding natural production of brominated aromatic compounds by filamentous algae as a response to environmental stress. Increased understanding regarding sources and possible variations in production of brominated aromatic compounds is crucial for successful monitoring and assessment of environmental status.