Phytoplankton’s demise from global warming is bad news if you like oxygen and seafood


The population of phytoplankton in the Indian Ocean has fallen 30 percent in the last 16 years.

Phytoplankton’s demise from global warming is bad news if you like oxygen and seafood

By Sean Hodell

Humans have to eat and breathe, but the fate of a tiny plant in the world’s oceans might affect our ability to do both. A recent study on the Indian Ocean published in Geophysical Research Letters showed that there is an “alarming decrease” in phytoplankton in this region over the past six decades. In fact, the  population fell 30 percent in the last 16 years, in large part because of global warming.

Peter Franks, a professor at the Scripps Institution of Oceanography at UC San Diego, says even “though there are regional differences due to different physical systems in different parts of the world ocean, global warming is expected to lead to a general decrease in the amount of phytoplankton.” Researchers pointed out that previous studies of the Indian Ocean that had reported a growth in phytoplankton had not looked at long-term trends and therefore did not make accurate predictions for changes in phytoplankton concentrations.

Phytoplankton are microscopic plants that reside in the upper layer of ocean water where they are able to receive adequate sunlight. They produce as much as half of all the oxygen on the planet through photosynthesis. The researchers analyzed the color of ocean surface waters from satellite images taken over decades. Like plants on land, phytoplankton contain chlorophyll that gives off a green color. The higher the concentration of phytoplankton in the ocean, the greener the water will be. This allowed the researchers to easily distinguish that the phytoplankton population has fallen.

This reduction in phytoplankton concentrations can be attributed to increases in the temperature of ocean water brought about by global warming. As the air is heated from greenhouse gases, the oceans warm along with it. Warmer waters lead to stratification of the ocean layers, which prevents subsurface nutrients such as nitrates from mixing with surface waters. Phytoplankton depend on these nutrients for survival.

Phytoplankton serve as the base of the ocean food chain and are the food source “for a wide range of sea creatures including whales, shrimp, snails, and jellyfish.” Disrupting the food chain can have devastating consequences for all marine animals, not just the ones that directly depend on phytoplankton as their main food source.

Humans will also be heavily affected by the loss of these tiny plants. Many who live on the coast of the Indian Ocean could lose their livelihoods because of a shortage in the supply of fish. Fishermen are already having to venture further and longer to catch increasingly smaller amounts of fish. Overfishing can be attributed to the shortage, but the main contributor is climate change and the ever-increasing ocean temperatures. It has already been measured that the rate of ocean heat storage has doubled in the last 18 years, which means oceans are now absorbing heat twice as fast as they were only two decades ago. Many coastal countries that border the Indian Ocean depend on the seafood industry, not just for economic means, but also for their diet.

Further research is needed to prove the findings, as the study mentioned above discloses. A five-year research vessel will be sent out into the Indian Ocean later this year to verify the results. However, this is not a problem that can be overlooked in the present, as climate models predict further warming throughout this century. The reduction in phytoplankton concentrations are a great example of unintended consequences of climate change.

Like many other consequences — sea level rise, food shortages, storm damage, etc. — the impact and severity will depend on how quickly we can reduce greenhouse gas emissions that are heating up our biosphere. Those reductions will occur faster with efficient and effective carbon pricing like Carbon Fee-and-Dividend.

Sean Hodell
Sean Hodell is currently a student at Georgia Tech in Atlanta, GA studying Public Policy. When he's not interning for CCL, you can find him writing grants for Engineers Without Borders - Georgia Tech, reading science fiction, or enjoying the great outdoors.