Document Type

Master's Thesis

Degree Name

Master of Science (M.S.)


Moss Landing Marine Laboratories


It is shown here that carbon dioxide gas has dramatic inhibitory effects on photosynthesis in representative species from six divisions of marine phytoplankton and two natural sites. Oxygenic photosynthesis was inhibited as a function of increasing CO2 concentration in the seawater media. The cellular content of ATP also decreased after treatment with CO2. Photosystem II variable-fluorescence parameters were altered under high-concentrations of CO2; Fv/Fm decreased and non-photochemical quench (NPQ) increased. Increases in the concentration of CO2 gas promoted xanthophyll cycle pigment alteration to what is believed a photoprotective state. The effect of CO2 was reversible in all metrics by returning the media to air saturation. The CO2 effect was also light dependent and was induced far below the light compensation intensity for photosynthesis. It is suggested that the CO2 effects described here were not due pH per se.


Thesis (M.S.) Division of Science and Environmental Policy. Moss Landing Marine Laboratories