EFFECTS OF PULP-MILL CHLORATE ON BALTIC SEA ALGAE

The long-term effects of pulp mill chlorate on different algal species of the Baltic Sea were studied in land-based model ecosystems simulat ing the littoral zone. Brown algae (Phaeophyta) exhibited an extraordi narily high sensitivity to chlorate and pulp mill effluents containing chlorate. All brown algal species ceased growth or showed major signs of toxicity at all concentrations tested, down to microgram per litre levels. EC50 levels for growth of Fucus vesiculosus were about 80-100 mug ClO3- litre-1. Blue-green algae (Cyanophyta) were not deleterious ly affected nor were green algae (Chlorophyta). The perennial and annu al species of red algae (Rhodophyta) were also unaffected by the efflu ents. Diatoms did not show any sensitivity and phytoplankton (fresh- a nd brackish water) were particularly insensitive. A phanerogam, Zoster a marina was also unaffected by the treatments.