The pros and cons of algal blooms, high concentrations of phytoplankton in the oceans, are a subject of much debate. But several studies in recent months have examined links between changing polar environments, exponential growth of algal blooms, and potential for carbon reduction.
One study, appearing in the journal Nature Communications in May 2014, suggests that ocean iron from glacial melt could have positive effects for polar regions in the face of global warming because of the nutrient quality for algae. “The theory goes that the more iron you add, the more productive these plankton are,” John Hawking, a doctoral student at the University of Bristol and lead author of the study, told Scientific American in May.
The University of Bristol study examined the amount of a specific type of iron (bioavailable ferrihydrite) released in glacial melt water from the Leverett Glacier in Greenland. The levels of this form of iron found in the glacier allowed Hawking to estimate that an iron flux of up to 400,000 to 2.5 million metric tons could be flowing from Greenland annually. These releases have the potential to be transported up to 900 km from the site of origin and to greatly affect the global iron cycle.
New findings coming out of a NASA-sponsored expedition off the coasts of Alaska discovered a massive algal bloom in this polar region as well. Contrary to Hawking’s study, the ICESCAPE expedition conducted by NASA in the Beaufort and Chukchi seas determined the growth in algae was a product of younger and thinning ice. Because of the changes in ice density due to Alaska’s warming climate, more sunlight is able to reach the water underneath the ice packs, according to researchers on the expedition. Therefore, the environment is more favorable for the phytoplankton.
Historically, expanding algae populations in other parts of the globe have generated many negative side effects. For example, the decay of algae during a bloom can suck nutrients and oxygen out of the water creating a dead zone. These low-oxygen areas reduce the productivity of wildlife, decrease their productive capacity, and can even kill them. Further, humans experience the effects of algal blooms through the ingestion of toxic substances via shellfish.
Yet, in the wake of information about the connection of algae growth and a warming world, studies are taking more effort to explore the positive consequences of algal blooms. A study conducted by the USGS Woods Hole Oceanographic Institution proposes that increases of phytoplankton in polar regions will serve as a new food source for wildlife and will offer increased carbon capture in these areas. The greater numbers of phytoplankton, the greater volume of carbon the population will consume during photosynthesis. Some scientists believe an increasing number of algal blooms will deplete carbon stores in the ocean, resulting in greater absorption of atmospheric carbon by the sea. Additionally, when the phytoplankton die, they often retain much of the stored carbon and carry it down to the ocean floor.
Scientists are not certain how the interplay between phytoplankton and ocean carbon will develop because ocean uptake of carbon (especially, in the deep water) can occur on a long timescale, and because it is not yet clear how much carbon is retained versus released during algae death.
With all of this in mind, scientists are hopeful that the correlation of glacial melt, encouraging environments, and algal growth will have a net-positive effect. Further study of this natural bioengineering project will definitely aide scientists in understanding climate change trends.