The Effects of Ocean Acidification on the Nutritional Composition of Phytoplankton for Fishery-Based Foodwebs

Phytoplankton require carbon dioxide (CO₂) as the primary substrate for carbon fixation and therefore growth.  The response of phytoplankton to variability in partial pressure of CO₂ (pCO₂) depends upon inorganic carbon acquisition and the efficiency of these process.  Shifts in phytoplankton community structure are expected, but it is unclear whether these shifts will favor more- or less-nutritious phytoplankton to support fisheries and aquaculture production of human food.

To anticipate how both natural and anthropogenic changes in ocean pCO₂ (a predicted doubling in atmospheric pCO₂ over the next century) will affect the base of the marine food web, we have begun efforts to determine competitive interactions between phytoplankton species under experimentally-simulated ocean-acidification conditions.  We will characterize physiological (i.e., lipid and fatty acid composition) and growth responses to different pCO₂/pH conditions of species representing main phytoplankton functional groups (e.g., coastal and oceanic diatoms, dinoflagellates, and calcifying prymnesiophytes) in CO₂-manipulated, laboratory cultures.  A primary goal of this research is to determine if changes in pCO₂/pH may bestow competitive advantages on certain phytoplankton taxa or species that may have better or worse nutritional profiles for aquacultured organisms and other grazers in marine ecosystems.