Data of Seasonal changes in bay water around Curacao Version 2

As endpoints of watersheds, bays often collect and concentrate erosion- and human-derived substances such as sediments, dissolved inorganic nutrients and pollutants. Through their connection with the ocean, the export of substances from bays to the coastal zone will affect the nearby benthic shallow ecosystems. We investigated the water movement and biogeochemistry of two bays with different adjacent land uses, Piscadera Bay and Spaanse Water, along the south coast of Curaçao during the Caribbean dry (May 2022 and 2023) and wet seasons (November 2021 and 2023). Water exchange between the bay and offshore waters was limited during the dry season for both bays, enhancing dissolved inorganic nutrient concentrations within the bays. The wet season showed increased mixing between bay and offshore water. Extreme weather conditions during the 2023 wet season due to an El Niño episode, resulted in heavy rainfall and runoff with an increased influx of waste water into the bay. This was apparent from the enriched δ15N and total xenobiotic concentrations that were over 1.5 times higher than were measured in the dry season. During the wet season, Piscadera Bay is subjected to higher wastewater influx and indeed exhibited elevated δ¹⁵N and δ¹³C values, indicating greater terrestrial influence than Spaanse Water. While this study includes data from one El Niño event, it highlights how extreme weather can boost nutrient and xenobiotics export from bays to the ocean, offering insights into potential impacts on nearby reefs under future climate change scenarios.