Seasonal variations of pollution indicators in a wildfowl reserve (Doñana National Park, Spain).

Pollution indicators in Doñana National Park show a cyclic seasonal pattern with maximum level in the autumn and minimum in the spring. While faecal streptococci proved to be the best indicator micro-organisms in this type of salty, alkaline environment, total coliforms gave an overestimation of pollution because of the presence of hydroteluric coliforms.