This project is a renewal of an existing ocean acidification (OA) grant supporting an interdisciplinary research team (called OMEGAS) with expertise in oceanography, ecology, biogeochemistry, molecular physiology, and molecular genetics. Research to date has documented a dynamic oceanographic mosaic in the inner shelf of the California Current System (CCS) that spans 1,200+ km and varies at tidal, diurnal, event, and seasonal temporal scales at local to ocean basin spatial scales. In OMEGAS II, the project seeks to better understand the drivers of this striking time-space variability, and to link the OA seascape to the physiological and ecological performance of a key member of this ecosystem, the mussel Mytilus californianus. In addition, the investigators will explore the influence of this oceanographic mosaic on species interactions and community organization. As a dominant habitat-forming species, strong interactor, and major space occupant, M. californianus is arguably the core component of the rocky intertidal ecosystem along the upwelling-dominated CCS. Using an interdisciplinary, spatially extensive approach integrating inner shelf oceanography with ecology, physiology, and eco-mechanics, the interdisciplinary team will study the response of juvenile mussels M. californianus to OA. The studies span levels of biological organization, thereby allowing assessment of how the cost of forming a shell under field conditions might influence physiological performance and resistance to predation. This investigation will include modeling to link to larger-scale ecosystem and oceanographic dynamics in the CCS and beyond.
Results from OMEGAS I show that the growth, survival, and shell strength of mussel larvae are strongly negatively affected by elevated pCO2, and that growth of adult mussels varied among sites within regions and between regions. Emerging data on natural variability in seawater conditions will allow a deeper exploration of the organismal response of M. californianus, and the ecological consequences of traits, such as reduced shell thickness and strength. The present project will expand and strengthen the existing oceanographic network to increase our understanding of the coastal OA regime, and provide the environmental context for ecological and physiological research. Specifically, this project will (1) conduct field and laboratory experiments on the influence of OA on the growth, shell accretion, and resistance to predation of juvenile mussels collected from 10 sites spanning 1,400 km of coastline, (2) link the OA-sensor oceanographic "backbone" to an existing database of community structure via ecological modeling to assess the influence of OA on coastal variation in community organization, (3) determine the physiological responses of juvenile mussels following field deployments and culture under common garden conditions to evaluate mechanistic underpinnings to the responses observed in mussels from different sites, (4) explore the physiological and transcriptomic response of mussels in lab mesocosms to field-documented variability in pCO2, and (5) using modified ROMS models, evaluate the linkage between basin-scale oceanography and local-scale variation in inner-shelf oceanography to evaluate the relative influences of large-to-local scale factors on OA variability. This research aims to understand how coastal ecosystems will respond to OA, and thus to develop our capacity to predict the future impact of OA on coastal ecosystems.
Broader Impacts. This project will leverage complementary funding for research, training and outreach, and engage undergraduates, graduate students, and postdoctoral researchers, as well as PIs. Part of an overall goal is to increase the visibility and familiarity of OA science for policy makers and the general public. Outreach will be facilitated through extensive ties to COMPASS (Communication Partnership for Science and the Sea), public lectures, websites, and multimedia outlets, such as films and television. Each campus is engaged in local-to-national displays on OA.
The impact of the increased absorption by the ocean of fossil fuel derived atmospheric carbon dioxide is one of the major present-day challenges in the ocean sciences. The steady absorption of carbon dioxide has led to a slow decrease in ocean pH with uncertain consequences to marine biota. This project supported a consortium, OMEGAS (Ocean Margin Ecosystem Group for Acidification Studies), of 13 Principal Investigators associated with six academic/research institutions along the California Current Large Marine Ecosystem (CCLME). The CCLME is subject to the phenomena of coastal upwelling where northwesterly winds act to draw water from depth, rich in the nutrients that drive photosynthesis, but also high in carbon dioxide and low in oxygen and pH. Coastal topography strongly modifies the coastal upwelling processes; coastline irregularities such as capes and bays produce variations in coastal wind, ocean currents, chemistry and biology. Strong upwelling at wind-exposed capes results in "upwelling centers", while in their lee, in bays or behind headlands, winds, upwelling and ocean currents are weaker creating "upwelling shadows". Strong gradients form between the freshly upwelled waters, low in pH, off a cape and the protected shadow waters behind the cape where photosynthesis is able to consume carbon dioxide and increase pH. The consortium research had two broad goals: 1) To understand the oceanographic drivers of the striking time-space variability in coastal pH documented previously in the CCLME and; 2) To link this pH seascape to the physiological and ecological performance of a key member of the coastal rocky intertidal ecosystem of the California Current System, the mussel Mytilus californianus. To address these goals the consortium: 1) Created a network of pH sensors from Oregon to Santa Barbara; 2) Tested the effects of varying pH on the growth, shell accretion, and resistance to predation of juvenile mussels collected from 10 sites spanning 1400 km of coastline; 3) Determined the physiological and genetic responses of field-deployed juvenile mussels that were subsequently exposed to varying pH conditions in a common garden experiment and; 4) Evaluated the linkage between basin-scale oceanography and local-scale variation in inner shelf oceanography to determine the relative influences of variation at these two scales on intertidal pH. As part of consortium MBARI (Monterey Bay Aquarium Research Institute): 1) Developed and built low cost autonomous pH sensors for deployment in intertidal locations from Oregon to Santa Barbara, 2) developed small, low cost moorings to measure pH, the partial pressure of carbon dioxide at the sea surface and in the atmosphere together with other standard oceanographic variables such as temperature, salinity, oxygen, chlorophyll fluorescence, and wind speed and direction; 3) Deployed these moorings and collected ancillary ocean acidity data from the intertidal to the California Current in the Monterey Bay region; 4) used a coupled ecosystem model to understand the processes driving variations in ocean pH along the US West Coast. Significant results from the MBARI work were: 1) Document large variations in pH along the US West Coast; 2) Determine that these variations were driven by both by the location of the site relative to upwelling centers and the CO2 but also by the content of the local upwelling source waters; 3) Determining that the CO2 content (and the pH) of upwelling source waters was strongly modulated by the decay of material at depth and its associated respiration; 4) Uncovering a strong and pervasive diel cycle in intertidal pH from Oregon to California; 5) Determining that this cycle was driven by photosynthesis (increase in day) and respiration (decrease at night) and; 6) Determining an exponential decay in the amplitude of the diel pH cycle with distance from shore in the Monterey Bay region. As part of the project we were able to demonstrate: 1) That it is possible to deploy affordable and sustainable pH sensor arrays that are able to collect information on scales of minutes and meters to years and hundreds of kilometers and; 2) That these large scale arrays are required to document and understand the variations in ocean acidity. With these tools managers and policy makers will be able to make informed decisions to preserve ocean resources, health and services.
