Eutrophication and water quality in a tropical Brazilian estuary

The use of indexes and trophic state models are gaining importance in evaluating the degree of anthropogenic influence on estuarine eutrophication and the impact on coastal and adjacent areas. A TRIX index and an ASSETS model were used to evaluate the level of eutrophication in the estuary of Suape Industrial Port Complex. The values for the TRIX trophic state multivariate index revealed the increase towards the upper estuary, going from 2.26 at high tide at station 1 (low estuary), demonstrating a medium trophic state and good water quality, to 6.43 at low tide at station 3 (upper estuary), showing an elevated trophic state and poor water quality, where continental drainage is accelerating the eutrophication process in the environment. In the evaluation generated by the ASSETS eutrophication model, the estuary eutrophication level was considered to be moderate, with Overall Human Influence considered Low, General Eutrophication Conditions also considered Low. Finally, the Determination of Future Outlook showed an unchanged expression and perspectives for slow degradation. The comparison between the index and model showed some similarities, in general, TRIX quantified the Massangana river estuary at a level medium of eutrophication and ASSETS qualified it as moderate.