Island Refugia and the Catalina Dynamic Ocean Chemistry Program

Islands offer the possibility of being refugia from ocean acidification. Oceanic conditions may produce different mean pH values for islands relative to nearby mainland, while natural variations in pH may influence how marine fauna tolerate increasingly acidifying waters. The Catalina Dynamic Ocean Chemistry (CDOC) program is designed to investigate natural variations at Santa Catalina Island, California, USA. Measurements of various ocean chemical parameters, including pH, were made at 18.3-m depth from a mooring near Two Harbors. There were 5 deployments, each being approximately 3 weeks in duration. The average pH value among the deployments was 8.18, significantly larger than measurements reported from the mainland coast in the Southern California Bight. We find that during regimes of strong stratification and internal waves (i.e., summer conditions), pH is modulated significantly at internal wave frequencies and is highly correlated with temperature. Strong episodic upwelling events occurring in less stratified conditions (i.e., winter conditions) are also attended by more acidic water. We find the largest modulation in pH for either summer or winter conditions to be greater than 0.1 pH unit.