Analysis of ocean acidification conditions across Bight wraps up

SCCWRP and its partners have completed a synoptic analysis of ocean acidification
conditions across the Southern California Bight continental shelf, the first phase of a multi-part Bight ’13 study documenting water quality in coastal waters.

The first-of-its-kind analysis, completed in October by the Southern California Bight 2013 Regional Monitoring Program, involved taking field measurements of pH and total alkalinity at variable ocean depths across all four seasons for two years, then calculating key indicators of ocean acidification, including aragonite saturation state.

Aragonite saturation state indicates whether shell-forming organisms are able to build and maintain their shells; as the world’s oceans acidify, shell-forming organisms are experiencing increasing difficulty forming calcium carbonate shells.

The study found that some Bight marine  communities are being exposed to waters at or near aragonite saturation state thresholds, which are levels at which organisms may experience adverse biological impacts, including shell dissolution and growth inhibition.

Deeper waters tended to be more acidic and have lower aragonite saturation states during the winter and spring, according to the study. Winter and spring are when seasonal mixing and upwelling move deeper, more acidic waters closer to the surface and to shore.

The findings are in line with data collected by the California Cooperative Oceanic Fisheries Investigations program (CalCOFI), which sampled farther offshore and observed similar patterns.

The ocean acidification analysis will feed into an ongoing, multi-year modeling study assessing the relative influence of anthropogenic vs. natural sources of nutrient inputs on biogeochemical cycling in the Southern California Bight.