Phytoplankton

Written by: Priyam

Image of a Phytoplankton

Climate change affects every breath we take, every glass we drink, and even the weather we experience. However, we tend to focus on the effects we can feel, smell, and touch while neglecting our actions' consequences on the rest of this planet’s inhabitants. One such inhabitant is the microscopic phytoplankton (which comes from the Greek roots phyton, "plant," and plankton, "wandering or drifting"), which is the foundation of a majority of aquatic ecosystems and produces 70% of the planet’s oxygen. Climate change presents a significant risk to our phytoplankton populations, threatening far-reaching consequences that extend to our atmosphere, human health, and all organisms worldwide. Ocean phytoplankton numbers have reduced by an incredibly alarming 40% from 1950 to 2010, and they continue to decline at a terrifyingly rapid rate of 1% per year. Here’s why you should care.

Phytoplankton, mainly tiny photosynthetic algae and cyanobacteria, are the leading producers of marine food webs. They convert sunlight and carbon dioxide into organic compounds through photosynthesis, sustaining diverse aquatic species. However, this foundation is disrupted as phytoplankton populations plummet due to climate change. According to Science Journal, reduced phytoplankton numbers have cascading effects on marine ecosystems, leading to diminished fish stocks, which can affect the livelihoods of millions of people who depend on fishing, not to mention the detrimental effects on marine food webs that depend on these fish.

Some climate models project that warming temperatures will alter ocean currents, reducing the amount of nutrients that well up from the deep ocean, resulting in fewer phytoplankton as the microscopic organisms are deprived of essential nutrients and starve. Fewer phytoplankton will, in turn, decrease the amount of carbon dioxide that is converted into oxygen in our atmosphere, which, in addition to the constant increase of carbon dioxide due to human activities, contributes to the greenhouse effect, trapping heat within the atmosphere, further raising the temperature of the ocean in a vicious cycle.

Diagram of “Ocean Acidification”

This excess carbon dioxide results in acidification, whereas the increased levels of the gas react with water, carbonic acid is formed, lowering the pH of the world’s oceans. This is another obstacle phytoplankton populations must face, as a 2015 MIT study predicted that some species will die out entirely while others will flourish, changing the balance of plankton species worldwide. Acidification impairs phytoplankton’s ability to create strong cell walls, making them physically smaller and less effective at storing carbon, resulting in more carbon being released into the ocean rather than being used as biomass. 

Near human settlements, however, phytoplankton flourish in the presence of nitrogen and phosphorus-containing compounds that we dump into the ocean. While this sounds positive, the phytoplankton that thrives in these artificial conditions creates an utter absence of resources for other aquatic flora and fauna. As these algae die, their cells are broken down by bacteria in the water, consuming massive amounts of oxygen, lowering oxygen levels in these bodies of water to a point where animals like fish find it impossible to survive. Researchers have found that phytoplankton that grow near human settlements have populations that increase dramatically to harmful levels. In contrast, the populations of phytoplankton that grow in the open ocean have drastically declined, with an overall global downward trend in phytoplankton populations. 

While we usually think of trees, shrubs, grasses, and other terrestrial flora as our primary source of oxygen, the microscopic phytoplankton that are the foundation of nearly every single marine ecosystem are some of the most significant contributors to the life-giving O2 in our atmosphere. As climate change worsens, this plankton, and as a result, every organism that breathes oxygen, are sent down an artificial spiral of doom as human activity increases the temperature of the water they live in, acidifies their water, and disrupts their food webs. At the same time, excesses of them suffocate coastal ecosystems. Our best option to help alleviate the consequences of our actions is to do as much as we can to reduce the amount of carbon dioxide and other pollutants that are released into our precious atmosphere from industrial and agricultural practices and try our best to restore our phytoplankton populations to what they used to be.