Environmental parameters and dissolved substances in the coastal waters of Curacao

The presence of dissolved substances in coastal waters and their impact on coastal ecosystems depend on influx of substances from land and offshore waterbodies, biological community composition, seasonal changes in environmental conditions, hydrodynamics and topographic factors. The relative importance of these factors is not well known for tropical islands. Here we examined the impact of physical and anthropogenic drivers on spatial and seasonal variability in geochemical properties (concentrations of inorganic nutrients, silicate, inorganic carbon and total alkalinity) of the coastal waters of a Caribbean island (Curaçao), comparing a dry (April 2022) and a wet (January 2024) season. CTD transects were conducted to depths down to 250 m to characterize water column properties offshore, and discrete water samples were collected along the same transects nearshore. Vertical mixing between nutrient-rich Subtropical Under-Water (70–200 m), Western North Atlantic Central Water (below 200 m) and shallow Caribbean Surface Water (70 m) was observed during the wet season, when coastal waters showed higher Si concentrations, especially at shallow depths, indicating terrestrial runoff. However, despite known high nutrient inputs into coastal waters near urbanized areas from earlier studies, we did not observe a clear relationship between land-based activities and nearby coastal water characteristics. During the dry season, higher N:P ratios were observed, indicating potential P-limitation of primary productivity. Additionally, at specific sites elevated alkalinity and inorganic carbon concentrations suggested enhanced (coral) carbonate dissolution. We discuss how seasonal variability in nutrient inputs and topography-hydrography interactions underlie the temporal fluctuations of observed dissolved substances in Curaçaoan waters.