Program     Circulation, biogeochemistry and carbon cycling in ocean margins       Poster Distribution and changes of pH along the East Coast of USA P-M1-09-S Xinyu Li* , University of Delaware Baoshan Chen, University of Delaware Yuanyuan Xu, University of Delaware Qian Li, University of Delaware Najid Hussain, University of Delaware Wei-Jun Cai, University of Delaware Presenter Email: xinyuli@udel.edu Ocean acidification has raised increasing worldwide concerns. It includes reducing seawater pH and saturation states of calcium carbonate minerals, which can have a dramatic effect on calcifying species and fisheries. As part of program monitoring process of ocean acidification, East Coast Ocean Acidification 2 (ECOA2) cruise was conducted from June 25, 2018 to July 31, 2018. total alkalinity(TA) and dissolved inorganic carbon(DIC) were measured. Parameters including pH, total alkalinity(TA) and dissolved inorganic carbon(DIC) were measured during the cruise. We used automated system AS-spec-pH1 Analyzer (Apollo SciTech) with purified meta Cresol Purple(mCP) dye for high precision spectrophotometric pH measurements. All pH data was calculated to in situ temperature. Results exhibited generally high pH (7.7653-8.0362) in southern waters (East Florida and South Atlantic Bight) and low pH (7.5867-8.0029) in northern waters (Mid Atlantic Bight and Gulf of Maine). Low pH is observed nearshore, where fresh water input is strong. Additionally, we calculated pH using DIC and TA data through CO2SYS. Differences between measured pH and calculated pH can indicate other control factors on pH. Besides, we compared pH data from ECOA2 cruise with pH results from previous cruises, Gulf of Mexico Ecosystems and Carbon Cruise1&2 (GOMECC1 & 2) and ECOA1. The broad patterns and changes of pH over 10 years along the East coast can be described by the impact of large scale circulation, source water contributions and anthropogenic influences.

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