Marine phytoplankton are an important component of our oceans. Not only do they act as the base of many marine food chains, fueling important fisheries and ecosystems, but they also contribute greatly to our global oxygen supply and draw down atmospheric CO2 during photosynthesis. This newly fixed carbon can eventually sink to the deep ocean, where it is stored for long periods of time before returning to the atmosphere. This process, known as the "biological pump", is critical to maintaining our current climate conditions.
Climate change, however, is expected to have major consequences for ocean productivity. Although increasing temperatures and CO2 concentrations would seem to be a boost for these organisms, research has shown that these changes may be much more complex. For example, a climate-induced shift towards greater nutrient limitation has been shown to favor small species over larger species such as diatoms. These larger species, naturally, are more efficient at transporting carbon downward. Therefore, a shift in the dominant phytoplankton community could also negatively impact the "biological pump." New research published in Frontiers of Marine Science seems to add to this troubling theory.
An international group of researchers wanted to test whether increasing CO2 levels could have a a similar impact on the phytoplankton community in a Norwegian fjord. They used mesocosms to simulate an increase in inorganic carbon as well as an "upwelling" period part-way through the experiment by adding nutrients. During the course of monitoring the composition of their simulated blooms, they sampled for dissolved and organic nutrient concentrations. Interestingly, the authors did not see a strong negative impact on their diatom community like in other studies. However, it was evident that small-celled algae (e.g. cyanobacteria like Synechococcus) were favored at the expense of coccolithophores, algae that use calcium carbonate to build their bodies.
The authors noted that this trend is consistent with previous research and has major implications for the cycling of elements in the oceans in the future. It has been widely hypothesized andeven observed that increasing ocean CO 2 and decreasing pH (i.e. acidification) will harm calcifying organisms. They found that organic carbon caught at the bottom of their mesocosms decreased by 25% throughout the course of the experiment. A shift from coccolithophores to picophytoplankton in the community may result in carbon recycled in surface waters rather than drifting into the deeper ocean for storage. The extent of these shifts in the context of increasing CO2, as well as changes to nutrient supplies, temperature, and light availability, could have significant impacts to ocean productivity and our climate.
An international group of researchers wanted to test whether increasing CO2 levels could have a a similar impact on the phytoplankton community in a Norwegian fjord. They used mesocosms to simulate an increase in inorganic carbon as well as an "upwelling" period part-way through the experiment by adding nutrients. During the course of monitoring the composition of their simulated blooms, they sampled for dissolved and organic nutrient concentrations. Interestingly, the authors did not see a strong negative impact on their diatom community like in other studies. However, it was evident that small-celled algae (e.g. cyanobacteria like Synechococcus) were favored at the expense of coccolithophores, algae that use calcium carbonate to build their bodies.
The authors noted that this trend is consistent with previous research and has major implications for the cycling of elements in the oceans in the future. It has been widely hypothesized and