Water quality and cyanobacterial blooms in the Piancó-Piranhas-Açu Watershed, Semi-arid Region of Northeastern Brazil: relationships with education toward sustainability

Greater emphasis has been attached to aquatic ecosystems in recent decades, as these are associated with indicators determinant of sustainability indices. The environmental impacts potential risk human health the semi-arid region state Rio Grande do Norte have frequently observed. This study aimed at evaluating cyanobacteria density, and indices that indicate Piancó-Piranhas-Açu Watershed quality. It also targeted identify factors impact most blooming organisms. sampling design consisted 12 collections different seasonal periods from 2009 2016, carried out by Água Azul Program on 6 points along basin. Environmental variables were used analyze Water Quality Index (WQI), Trophic State (TSI), Cyanobacteria Density (CD). mean WQI indicated ‘Regular’ water status for PPA3 PPA4, while PPA1, PPA2, PPA5 PPA6 resulted ‘Good’. As TSI, levels average degree eutrophication (mesotrophy) three points, high (eutrophy) two low (oligotrophy) one point. In this sense, activities - especially diffuse polluting sources around spring seemed worsen scenarios. density potentially toxic was high, exceeding CONAMA Resolution 357/2005 recommends a maximum value 50,000 cells/mL, Ministry Health Ordinance 2914/2011 threshold 20,000 cells/mL. Regarding general correlation between CD seasonality we found significant influence (p < 0.05), greater proliferation organisms directly related drought. We concluded although dams’ waters suitable multiple uses, TSI had limitations, considering excessive primary productions presence and, thus, occurrence cyanotoxins ensuing pollutant loads. led us conclude adoption education practices toward would help preservation local social development. enable establishment effective priority public policies mitigation pollution.