Evaluación microbiológica de la laguna de Tamiahua, Veracruz, en el ciclo 1994-1995

Abstract

The Tamiahua lagoon bacteriological pollution was evaluated, in water, sediments and oyster, through the multiple tubes methos (Most Probable Number), utilizing faecal coliforms ans streptococci bacteria as indicators. Physicochemical parameters: pH, dissolved oxigen, salinity and temperature were measured. The samplings were performed in May, September (1994) and March (1995). The central part of the lagoon showed a sevre pollution surpassing the 2,400 coliforms/100 ml in water and 240,000 coliforms/100g in sediment. The water quality was inadequate for molllusk cultivation, the 63% of the samples were polluted by cultivate faecal coliforms; it was inadequate for recreation qith primary contact and for the protection of the aquatic life too, because 26% of the samples exceeded the limits. The lagoon conditions have shown deterioration comparing with previous studies. The oyster was inadequat for human consumption, with a maximum of 15,000 faecal coliforms/100g anad 4,300 cultivate faecal streptococci/100g. The faecal streptococci surpassed the 2,400 bacteria/100ml in water and 24,000 bacteria/100g in sediment and presented seasonality with low incidence in water during rainy season. This group had value as complementary indicator, in samples that not eceeded the limits by coliforms. The relationships between the physicochemical parameters and bacteria showed low importance. The pH and temperature had few variations. The dissolved oxigen has a direct relatioship with faecal coliforms and streptococci, the greater concentrations of the first group were associated with the higher levels of dissolved oxigen and the scarce presence of the second group with sites with oxigen low levels. The salinity had low values in localities with high concentrations of bacteria, though it was found high concentrations of bacteria in sites with marine influence, due to discharges of the Tamiahua city.