Posted on EPOCA: 10 Apr 2012
What is ocean acidification?
As the ocean absorbs increasing levels of carbon dioxide (CO2) from the atmosphere, it causes changes in ocean chemistry. When carbon dioxide reacts with water, it creates carbonic acid, decreasing pH and carbonate ion concentration. Lower levels of pH in the ocean result in higher levels of acidity, causing “ocean acidification.”
What are the potential impacts?
Ocean acidification can have significant impacts on marine species, especially organisms that rely on calcium carbonate to build and maintain their shells and skeletons, such as clams, oysters, sea urchins, crabs, lobsters, and corals. Ocean acidification can both reduce amounts of calcium carbonate and prove corrosive to shells and corals.
What is SCCOOS doing?
SCCOOS plans to add ocean acidification monitoring to its ongoing observations of the coastal ocean. Sensors that monitor pH, CO2, and dissolved oxygen can be added to pier stations and gliders. These observations will allow for continuous measurements of acidification in the Southern California Bight and will allow for improvements to be made to the models that forecast climate change.
SPRAY UNDERWATER GLIDERS
SCCOOS maintains a network of gliders in the waters off California to monitor climate and ecosystem change. This glider network has been in operation continuously for over 5 years, with data updates on the SCCOOS web site in near real time. Measured variables include pressure, temperature, salinity, and currents. In addition, chlorophyll fluorescence provides a measure of phytoplankton, and acoustic backscatter in sensitive to zooplankton abundance. The integration of dissolved oxygen sensors on the gliders is proceeding for the purpose of monitoring hypoxia in coastal waters. The dissolved oxygen data also allow an estimate of parameters relevant to ocean acidification through proxy relationships.
Using relationships developed by scientists at Scripps Institution of Oceanography, NOAA Pacific Marine Environmental Laboratory, Universidad Autonoma de Baja California, and University of Washington, the glider data have been used to estimate pH and aragonite saturation. Aragonite is important to organisms that form shells, as saturation levels below one may lead to dissolution of the shells.
The sections below were occupied by a Spray glider during February 2011. Dissolved oxygen and aragonite saturation are contoured from profiles every 3 km as a function of depth and distance along the glider’s path. The shore is to the right of the sections and the open Pacific is to the left. Dissolved oxygen concentrations of less than 60 µmol/kg (heavy black line) are considered hypoxic. During this section, hypoxic conditions were as shallow as 200 m. Near the coast the level of aragonite saturation reached one (heavy black line) at 50 m depth close to the coast. The shoaling of these surfaces towards the coast may be caused by upwelling, which also brings needed nutrients to the surface. Monitoring changes in the supply of deep waters to the surface is a goal of the SCCOOS glider network.
SCCOOS supports nine nearshore stations of the California Cooperative Oceanic Fisheries Investigations (CalCOFI). The CalCOFI group collects samples to characterize the inorganic carbon system at selected locations along its research cruise tracks. Total inorganic carbon and alkalinity are measured which allows for the calculation of pH and pCO2: http://calcofi.org/field-program/rosette-sampling/454-under-co2.html
The National Oceanic and Atmospheric Administration (NOAA) Pacific Marine Environmental Laboratory (PMEL) Carbon Program measures ocean carbon levels and ocean acidification with a series pCO2 measurements, from moorings and underway platforms, together with other ancillary measurements such as pH and oxygen levels.
The California Current Acidification Network (C-CAN) is a collaborative effort between the West Coast shellfish industry and scientists to explore what is causing shellfish losses, the role of ocean acidification, and how to adapt to these changes in order to sustain shellfish resources.
The Ocean Margin Ecosystems Group for Acidification Studies (OMEGAS) project seeks to meet society’s demands for scientific information on ocean acidification across the California Current Large Marine Ecosystem: OMEGAS maintains eight moorings on the 15 m isobath to measure water properties including pH, dissolved oxygen, and for some locations pCO2.
OMEGAS also maintains pH and temperature sensors at seven intertidal sites.
SANTA BARBARA COASTAL LTER
The Santa Barbara Coastal Long Term Ecological Research Project (SBC LTER) will soon install a pH sensor on its Mohawk Reef site near Santa Barbara; pCO2 and oxygen sensors will be added with support from the OMEGAS project. The SBC-LTER is also collaborating with OMEGAS in maintaining a mooring equipped with a pH sensor at Alegria near Gaviota, California.
Southern California Coastal Ocean Observing System (SCCOOS). Web page.