Caroly's Notes: Ocean Connections

Welcome to our March 2019 e-News! I continue to search for interesting connections between ocean life, land, and freshwater. Sometimes, connections are found in the unlikeliest of circumstances, such as the middle of the ocean. A February issue of the journal PLOSOne included a fascinating study showing that sea snakes depend upon freshwater to drink, even in the open ocean. Lillywhite and coauthors studied the drinking behavior of the Yellow-Bellied Sea Snake, a pelagic snake found throughout the Pacific ocean. Specifically, the researchers studied this snake near Guanacaste, Costa Rica, where the region’s dry season can last for over six months. The snakes were previously thought to have drunk saltwater, as they have salt glands; however, the glands are small and may be used more for ion balancing than enabling the snakes to rely on seawater for drinking. The scientists asked the question: what do these snakes do for freshwater during the dry and rainy seasons? Lillywhite and coauthors captured the snakes at different times and tested their response to freshwater in the lab. The researchers found that the percentage of snakes drinking freshwater immediately upon capture significantly and progressively declined over time, starting from just prior to and during the rainy season. The evidence suggests that the animals take advantage of freshwater lenses of water over the ocean (or dilute brackish water) immediately following rainfall, and that their subsequent need for freshwater is reduced as a result of precipitation.

Climate change is projected to increase both the intensity and extent of droughts in the tropics. These species may be especially sensitive to any changes in precipitation caused by climate change. Here at REEF, we are currently pursuing funding to explore the relationship between our extensive fish dataset in the Florida Keys, climate change, and other environmental stressors; as well as exploring climate change impacts on the Nassau Grouper, reported later in this issue. We hope you enjoy reading about REEF's work, partners, and members, and see you next month!