The Albemarle-Pamlico estuary system (APES) is the second largest estuary in the lower 48 states, and surrounds one of the largest expanses of coastal freshwater wetlands in the country. The Intergovernmental Panel on Climate Change predicts that by the end of this century global sea level will rise by as much as 82 cm, which could result in a loss of 1260 to 3020 km2 of valuable wetland habitat around the APES. Before this large-scale inundation occurs, many coastal ecosystems are already experiencing elevated salinity. Salinization of previously freshwater or brackish ecosystems can be expected to lead to shifts in the biotic and chemical composition of these systems as well as altering biogeochemical cycles. Here, we examined seasonal and long-term trends in salinity in the APES over the last 46 years. We predicted that salinity would exhibit strong seasonal variation overlaid on top of a general increasing trend. Using geospatial analysis of salinity data from 1970 to 2015, accessed from the EPA’s STORET data warehouse, we calculated the average salinity of the APES on a monthly basis and analyzed seasonal and long-term trends.
Results/Conclusions
From 1970 to 2015 annual average salinity in the APES has increased by 1.5 parts per thousand (ppt), an average of 0.033 ppt yr-1. During this time the annual maximum salinity increased nearly 20 ppt in some parts of the estuary. There is high variability in salinity within years, with the highest salinity occurring in late summer following years with low precipitation. The magnitude of seasonal variation has increased from 3.8 ppt between the lowest and highest salinity months in 1970 to 5.6 ppt in 2015. With the APES contributing half of fish nursery area from Maine to Florida, these patterns of increasing seasonal differences and higher average annual salinity could have serious consequences for Atlantic fisheries. At this point it is unclear what is driving the increase in salinity in the estuary, but decreases in river discharge, changes in precipitation regimes, and sea level rise could all be contributing to the long-term pattern. This work contributes to our understanding of the effects of climate change in and around the APES, and could help us forecast how estuaries will respond to accelerating sea level rise.