Contrasting nutrient distributions during dry and rainy seasons in coastal waters of the southern Gulf of Mexico driven by the Grijalva-Usumacinta River discharges

Globally, nutrient river discharges drive water quality of coastal ecosystems, and excess nutrients can cause eutrophication impacts. The Grijalva-Usumacinta River System (GURS) discharges in the southern Gulf of Mexico (SGoM) and it is the second largest riverine input to the Gulf. To study how contrasting GURS freshwater flow between rainy and dry seasons affects nutrients concentrations in the receiving coastal ecosystem, we evaluated nutrient variability in the water column during both seasons. High inorganic nutrients and total phosphate outline the rivers discharge plumes during rainy season, and were significantly higher than during the dry season throughout the study area, suggesting contrasting seasonal nutrient discharge of the GURS to coastal waters. On average the GURS discharged 141,123 t N yr(-1 )6893 t P yr(-1 ) and 928,904 t Si yr(-1 ) to SGoM. These results contribute with a nutrient baseline in the SGoM that could be useful for GURS decision-makers.

Automated summary

The study shows that GURS' freshwater flow in rainy and dry seasons has different impacts on nutrient concentrations in coastal ecosystems, with significantly higher nutrient discharge in the rainy season.