Award: OCE-1041089

This project was the first, and most comprehensive, effort to study the patterns and impacts of ocean acidification (OA) at the scale of a large marine ecosystem using a combination of laboratory and field experiments, and remote sensing. The grant enabled the formation of a coast-wide consortium, OMEGAS (Ocean Margin Ecosystems Group for Acidification Studies), a group of 15 principal investigators spread across six West Coast institutions from Oregon to southern California. OMEGAS addressed the effects of OA using an approach that integrated across levels of biological organization (i.e., genes, genomes, individuals, populations, communities, and ecosystems), with laboratory experiments investigating the genetic and physiological mechanisms underlying ecological responses of mussels and sea urchins across the varying oceanographic conditions along the US West Coast. Here, the California Current System (CCS) flows from north to south, and coastal upwelling occurs during April-October. As is well known, coastal upwelling injects cold, nutrient-rich, salty, low pH water into the coastal zone. The high nutrients fuel the high productivity of the CCS, but also have a downside. After a short life, the dense phytoplankton blooms that are formed in some coastal regions die and begin to sink. Phytoplankton decay releases carbon dioxide, which ultimately drives down pH, making waters more acidic. Combined with the naturally low pH in the upwelled water, this additional source of acidity can drive coastal ocean pH to exceptionally low levels that interfere with precipitation of calcium carbonate shells or skeletons in shellfish and other marine organisms. The discovery by Dr. Richard Feely and colleagues in 2007 that such acidified water occurs at the surface of the ocean over the continental shelf, and can actually arrive on the shore at some locations, was a surprise to most marine scientists. In OMEGAS, we (1) established a network of pH sensors on rocky shores and in adjacent shallow waters at sites from central Oregon to southern California that varied in the strength of coastal upwelling, (2) carried out laboratory experiments testing the effects of ocean acidification (OA) on the performance of mussel and sea urchin larvae, (3) sequenced the genomes of lab-reared larvae to identify those genes affected by elevated OA, and (4) transplanted marked mussels, a key space occupier along the coast, to determine how their growth varied along the coastal mosaic of OA. We found that (1) mussel larvae grew less and had weaker shells when raised under elevated OA conditions, (2) the performance (growth, physiology) of sea urchin larvae was minimally affected by elevated OA, but (3) OA imposed natural selection for specific genotypes that were adapted to these conditions, (4) adult mussel growth was positively, not negatively associated with lower pH conditions, (5) periods of unexpectedly low pH are already occurring along the CCS and are induced by upwelling events, (6) that, surprisingly, these low pH events are more severe to the north, where upwelling is weaker but where phytoplankton blooms are denser, and (7) as a result, regions of the coast differ in their intensity of OA. Lastly, our results suggest that (8) the currently decreasing levels of pH along the CCS are attributable to anthropogenic-derived increases in CO2. Furthermore, because of 30-40 year time lags between the uptake of CO2 in the Western and Tropical Pacific Ocean and the arrival of such waters to the CCS, there will be unavoidable changes in carbonate chemistry that will likely result in substantial increases in the severity and frequency of corrosive conditions along the US West Coast. Overall, although lack of funding has ended OMEGAS, our work vastly increased the understanding of current and future OA regimes in the CCS, and has set the stage for investigation of broader, ecosystem impacts, which remains as perhaps the greatest challenge imposed on marine s...