Eelgrass response to carbon dioxide enrichment (Zostera marina)

Projected increases in dissolved aqueous carbon dioxide concentrations, [CO2(aq)], from fossil fuel combustion may have significant impacts on photosynthesis of CO2-limited organisms, including seagrasses. This study examined the impacts of long-term CO2(aq) enrichment on the performance of eelgrass (Zostera marina L.) growing under light replete and light limited conditions for one year. Eelgrass shoots were grown at four CO2(aq) concentrations in outdoor flow-through seawater aquaria bubbled with industrial flue gas containing 10% CO2 . Vegetative and flowering shoot counts, and rhizome biomass increased in proportion to CO2(aq) enrichment in light replete conditions. CO2(aq) enrichment did not affect eelgrass performance in light limited conditions. CO2(aq) enrichment did not alter growth rates, leaf size, or leaf sugar of individual shoots in either light treatment. Thus, CO2(aq) enrichment had a significant positive impact on shoot populations, but not on individual shoot performance. Increased CO2 availability may enhance productivity, density, and distribution of seagrass meadows.