A comparison of pCO2 patterns and variability in local waters with the flowing seawater system at Shannon Point Marine Center
Loraine Martell-Bonet1 and Brooke Love2
1University of Puerto Rico at Humacao, 2Western Washington University
CO2 in seawater
In the atmosphere CO2 is inert, but can change the chemistry of water when dissolved. Dissolved inorganic carbon (DIC) exists in the ocean as three forms: CO2, bicarbonate (HCO3-) and carbonate ions (CO32-) (The Royal Society, 2005). High concentrations of CO2 can cause a decrease in pH, making the water acidic. When CO2 reacts with seawater the result is bicarbonate (HCO3-) and hydrogen ions (H+). The increase of H+ make the water acidic. Processes affecting the carbon cycle fluxes in coastal regions include upwelling (bringing CO2-rich deep water to the surface), river influxes, primary production (carbon fixation), respiration (release CO2) and sediment burial. Changes in ocean chemistry can impact marine organisms and ecosystems. Calcification rate in marine organisms that produce calcium carbonate (CaCO3) shells or skeletons can decrease with acidified water (Dooney, 2010). On the other hand, high reproduction, increase in biomass below the ground, and proliferation was observed in the eelgrass Zostera marina in high CO2 and light environment (Palacios and Zimmerman, 2007). Changes in species can modify the food webs. Species that are not directly impacted by high levels of CO2 can be indirectly impacted by changes in their food sources, competitors or predators (Harrould-Kolieb et al., 2010).
Sea tables at Shannon Point Marine Center
Shannon Point Marine Center (SPMC) is equipped with sea tables where we hold organisms for research. The system circulates seawater through a feed line from an intake that is 30 m from the beach and 10 m deep. The water is stored in a 30,320 liter holding tanks for approximately two hours and then goes to the sea tables. The seawater for the sea tables is monitored for temperature, dissolved oxygen, salinity and nutrients, but measurements of pH or CO2 are not taken. Trying to recreate the natural environment is difficult and it is possible that the organisms that we keep in the sea tables are in different CO2 conditions from the natural environment. Changes in seawater pH can affect CO2 fixation or respiration, regulation of internal pH, and uptake of nutrients (The National Academy of Science, 2010).
Comparison of natural habitat with the sea tables
In this study we analyzed samples from the beach and the sea tables, and in situ pH measurements from the sea tables and the intake to compare the partial pressure of CO2 (p CO2) and pH from intertidal seawater (Shannon Point Beach) and SPMC sea tables to see if the sea tables are a good representation of local waters. We expected that the seawater from the sea tables would be more acidic than the beach because the water in the sea tables is stored in tanks where respiration might be greater than photosynthesis.
