There is a misconception that the rainforests contribute significantly to the oxygen we breathe. In reality, the animals and microscopic life living in the rainforest consume most of the oxygen. As a result, the net production of oxygen by the rainforest or any forest is actually close to zero. The commonly reported figure of the rainforests contributing 20% of the Earth’s oxygen supply is definitely a misrepresentation. The Amazon rainforest has also been affected by human-caused with annual fires that reduce the oxygen it can supply for the ecosystem.
However, phytoplankton in the ocean can also produce oxygen. Phytoplankton are microscopic marine algae that have chlorophyll, rely on the sun to live, and grow in the upper part of the ocean. They are essential to the food chain of the marine animals. Scientist have agreed that 50-80% of the oxygen in the Earth’s atmosphere comes from phytoplankton carrying out photosynthesis.
So yes, phytoplankton do produce more oxygen than a rainforest! The reason for this 30% range of difference is the fact that phytoplankton concentration varies depending on the time of the year. With more sunlight in spring and summer, there will be more phytoplankton blooms (shown as an areas of paler blue and green in the satellite image). Conversely in winter, there will be fewer phytoplankton blooms with the reduced sunlight and availability of nutrients.
How are phytoplankton being affected by climate change?
So what does this have to do with climate change? Phytoplankton photosynthesize in the upper layer of the ocean where sunlight can penetrate. Warming waters and warming atmospheric temperatures can accelerate phytoplankton growth. Additionally, rates of precipitation are increasing with the warming climate, causing more rainfall that can flood rivers and cause increased river runoff. With the combination of warmer water, bright sunlight, and increased nutrients, some phytoplankton habitats are a little too suitable. With these changes occurring more frequently and with longer duration, algal blooms now sometimes last longer and become toxic. This can have devastating effects, for example by creating dead zones and fish kills. Instead of enabling primary production at a healthy rate, HABs can deplete the water column of oxygen, causing mortality among organisms such as fish that depend on it.
Other climate-change induced effects on phytoplankton include increased ice melt causing earlier or multiple blooms in the polar region, and stronger stratification that suppresses mixing in the water column. In polar regions, the formation of seasonal sea ice is a prominent phenomenon. Historically overlooked, phytoplankton blooms can occur under the ice where light is limiting. With the temperature of the polar regions warming, much of the seasonal ice is not as thick as in years past, potentially augmenting the frequency and/or strength of blooms in the region.
…so what?
At this point, I think it’s safe to say that you now think phytoplankton are extremely cool, though you might be wondering, “so what?” Since we know they are the foundation of the marine ecosystem, any change in phytoplankton’s natural processes has a ripple effect for other organisms, thus potentially changing the dynamic of the marine ecosystems where phytoplankton are present.
Since phytoplankton are oceanic microorganisms, they often escape our immediate thought of climate change, but preserving phytoplankton is the key to preserving life on this planet and it’s essential that they are included in the conversation. Whether it’s talking about marine food webs or climate change impacts, make sure you’re not leaving out these little creatures! They provide half of our planet’s oxygen – so take a breath, now take another. You owe that to phytoplankton!
