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Seasonal dynamics in the inner Guayas Estuary, Ecuador

Abstract:

The Guayas estuary in Ecuador is the largest estuarine ecosystem on the Pacific coast of South America. This estuary provides nursery and fisheries habitats, as well as filtering and detoxification services provided by suspension feeders, vegetation, and wetlands. We used oceanographic and meteorological observations to understand the hydrodynamic variability of two areas in the inner part of the estuary, Manglares de Churute and Estero Salado, from February 2016 to February 2017. Churute has less anthropogenic impacts than Estero Salado, which is currently uncoupled from river flow and highly influenced by Guayaquil, the second largest city in Ecuador, and adjacent shrimp pond effluents. The influences from the ocean and river on Churute include higher dissolved oxygen (DO) and lower salinity, temperature and phosphates than in Estero Salado, particularly during the wet season when the river is the dominant mode of forcing in those warm and rainy first months of the year. Hypoxic levels (DO below 2 mg L-1) were found in Estero Salado in several stations during the hot, rainy season. These data suggest seasonal variability (dry/rainy season) influences the hydrographic conditions in the inner Guayas estuary mostly, adding variability to salinity, turbidity, nutrients and DO of the whole water column.