AME prepress abstract  -  DOI:

Elevated toxic effect of sediments on growth of the harmful dinoflagellate Cochlodinium polykrikoides under high CO2

Alexandra R. Bausch*, Fulvio Boatta, Peter L. Morton, Kali T. McKee, Robert F. Anderson, Helga R. Gomes, Joaquim I. Goes


ABSTRACT: Ocean acidification will likely have significant impacts on phytoplankton growth in marine ecosystems over the course of this century. Coastal waters, which can be strongly influenced by suspended sediments, can also be particularly sensitive to ocean acidification. While the individual effects of trace metal inputs and ocean acidification have each been well documented, the combined effects of high trace metal concentrations due to mobilization from sediments and high dissolved carbon dioxide (CO2) concentrations (low seawater pH) on the growth of marine phytoplankton are not known. In this study, a batch culture experiment was performed using the model organism Cochlodinium polykrikoides over 35 days under a range of CO2 (400, 800, and 1200 ppmv) following sediment additions. At high CO2, dissolved iron (Fe) and nickel (Ni) concentrations increased over time. Dissolved Ni concentrations were significantly higher after 35 days at 1200 ppmv CO2 compared to the other treatments and corresponded to significant decreases in C. polykrikoides growth rates. In addition, a toxicity bioassay experiment was performed over 29 days under a range of Ni or Cd concentrations at ambient CO2. The growth responses of C. polykrikoides were dose-dependent and were significantly lower under increasing Ni or Cd concentrations. The findings suggest that a combination of elevated total dissolved Ni supplied from sediments and high CO2 conditions could suppress the growth rates and photosynthesis of C. polykrikoides in coastal marine ecosystems. This is the first study to examine the synergistic, toxic effects of lithogenic trace metals and CO2 on phytoplankton growth.