Seasonal variation of contamination by coliforms on the sand and water of the Cassino Beach, Rio Grande-RS

Abstract

The occurrence and concentration of indicating bacteria such as coliforms in the ocean has been used for decades as a safety recreational measure. The water in the recreational area of beaches as well as the sand are easily acted upon the fecal contamination originated from effluents of agriculture, domestic sewers contribution, the presence of wild and domestic animals and the swimmers. The increase of the human activities, the urbanization and the industrialization has considerable influence on the environment balance of those areas. This study had as objective to evaluate the coliform contamination on the water and sand at places next to the urban areas of Cassino Beach, in Rio Grande/RS. The choice reference was the west jetty located in the Patos Lagoon’s mouth, two sample places were chosen and the same were used eighteen times. The MPN (Most Probable Number) analysis was accomplished for thermotolerants coliforms using the multiple tubes technique, with five tubes series in two stages, a preliminary test and a confirmation test. This study results showed that the contamination of the sand is higher than that in the water throughout the year. The largest sand and water contamination happened during the spring and the summer.