Estuaries exist at the land-sea margin, so are both directly impacted by N pollution and important in the processing of terrestrial nutrients. West Falmouth Harbor (WFH) is a shallow estuary in Massachusetts (USA) that intercepts high-N groundwater discharge from a local aquifer impacted by a wastewater treatment facility. Our early work (2005-09) showed a net import of total N (TN), total P (TP), and inorganic P (DIP) from the coastal ocean during the summer. Import of P from coastal waters was sufficient to maintain N-limiting conditions, and the estuary on average retained the entire, large terrestrial N load plus additional N from the adjacent coastal waters (Buzzards Bay). This N retention was presumably a combination of seasonal storage and biogeochemical processes.  Since 2010, there has been a significant loss of eelgrass habitat in the harbor. Between 2014 and 2019 we again measured summer season nutrient fluxes and found a continued net import of DIP, but a change to a small export of TP and a significant export of TN from WFH. Examining the incoming and outgoing tide data revealed that the concentrations of N and P in coastal waters that daily enter WFH have decreased, perhaps related to changes in N. Atlantic circulation patterns and warming coastal waters.  Hence we are seeing changes in WFH seasonal net nutrient fluxes due to processes acting at both regional (climatic) and ecosystem scales.  Inorganic N:P ratios still indicate strong N limitation of primary production, suggesting control of N inputs remains critical to ecosystem health and habitat recovery.  

Primary Presenter: Roxanne Marino, Cornell University (rmm3@cornell.edu)

Authors:

Roxanne Marino, Cornell University  (rmm3@cornell.edu)

Melanie Hayn, Cornell University / Marine Biological Laboratory  (mkh23@cornell.edu)

Robert Howarth, Cornell University / Marine Biological Laboratory  (rwh2@cornell.edu)