The latest investigations confirm the suspicion that the mass development of a toxic brackish water alga has occurred in the Oder. This phenomenon could have played a role in the massive kill of fish, mussels, snails, and possibly other animal species. The researchers continue to believe that it is not a natural phenomenon, given that the algae species Prymnesium parvum does not, under natural conditions, occur in large numbers on the stretches of the Oder that have been hit. To occur in large numbers in this area, the species is dependent on salinity levels that can only be produced by industrial discharges.