Environmental contaminants in otter (Lutra lutra) in Småland : Present levels and temporal changes (1966-2014)

The Swedish otter (Lutra lutra) population decreased markedly after the 1950’s and was considered to be seriously threatened for decades. Pollution from industries and other anthropogenic activities were suspected to be the major cause of the decline. The otter is a top-predator in aquatic systems and therefore particularly susceptible to bioaccumulative and toxic substances. For this reason, the species can be regarded as a valuable indicator of environmental health. Today, the Swedish otter population is increasing and has been reestablished in many areas. However, the otter is still missing in some regions of Sweden, especially in the southeast. The aim of this study was to investigate past and present levels, and temporal trends, of environmental contaminants in otters from Småland.The study is based on data of environmental contaminants in liver and muscle tissue from dead otters found in Småland during 1966-2014. I found that the perfluorinated compounds PFOS and PFOA have increased in otters since the 1970’s which is alarming and should be given special concern in future monitoring. Also, while mercury (Hg) is rather stable, selenium (Se) concentrations are decreasing, resulting in Hg exceeding Se on molar mass basis in several otters. This indicates that all of the available Se is bound to mercury, which may imply that the otters are vulnerable to additional Hg contamination. My conclusions are that the present concentrations of the studied environmental contaminants have probably not affected the otter population in general. However, otters may be exposed to toxic levels of some contaminants in certain areas that are more polluted from anthropogenic activities. This could be harmful to individual otters or their reproduction, and therefore, continued monitoring is highly relevant