Glider-Based Observations Reveal Seasonal pH and Aragonite Saturation State Variability in Coastal U.S. Mid-Atlantic Shellfishery Management Zones

Ocean and coastal acidification alter the oceanic carbonate system, increasing potential for ecological, economic, and cultural losses. Currently, productive coastal systems lack vertically-resolved high-resolution ocean carbonate system measurements on timescales relevant to organism ecology and life history. To address this issue, we modified and integrated a newly developed deep ISFET (Ion Sensitive Field Effect Transistor)-based pH sensor system into a Slocum G2 profiling glider. From Spring 2018 to Fall 2019, we conducted seasonal pH glider deployments in Atlantic surfclam (Spisula solidissima) and Atlantic sea scallop (Placopecten magellanicus) commercial management zones in the Mid-Atlantic Bight (MAB). Simultaneous measurements from multiple sensors on the same glider enable calculation of carbonate system parameters (e.g. aragonite saturation state) and mapping of these parameters against other variables, such as dissolved oxygen and chlorophyll. The seasonal observations of carbonate chemistry presented here, along with ongoing glider-based monitoring, reveal the physical, chemical, and biological drivers of acidification in this vital economic zone. Furthermore, these data are being used in conjunction with shellfish stock assessments and larval dispersal models to identify times and locations where shellfish stock may be at high risk of acidification. Understanding carbonate chemistry dynamics in coastal systems is necessary to predict the impacts of ongoing climate change on ecosystem services and the economy.