Global warming could cause ocean plankton to stop absorbing CO2 and become one of the biggest sources of greenhouse gases. According to scientists from the U.S., this could lead to a 20-40% reduction in the number of inhabitants of the middle depths of the world’s oceans.
Mixotrophic forms of plankton, which can switch between photosynthesis and eating organics, have been found to play a far more important role in ecosystem responses to global warming than we have assumed in the past. These microbes can turn plankton communities from CO2 sinks into greenhouse gas emitters, further accelerating warming.
Mixotrophs are what biologists call a special category of microbes and phytoplankton that can obtain energy both through photosynthesis and by trapping and digesting organic particles and living cells. Climatologists were interested in how mixotrophs would respond to changes in ocean temperature and other ocean properties associated with global warming.
To do this, the scientists tracked the effects of these factors on the colonies of different types of myxotrophs and developed a mathematical model of their ecological communities based on these observations. It allowed them to calculate how the behavior of this form of plankton will change over the coming decades as global warming affects the world’s oceans.
These calculations showed that further increases in temperature and other changes in the properties of the hydrosphere will lead to strong destabilization of communities of myxotrophs, and in many cases these changes will occur very quickly and dramatically. Such shifts will, in most cases, lead to the “switching” of a significant part of surviving myxotrophs to the organic food regime.
As a result, plankton will begin to release large amounts of CO2, rather than absorb it, which will further accelerate global warming and force marine microbes to produce even more greenhouse gases. This peculiarity of plankton must be taken into account when predicting how the Earth’s climate will change in the near future.
Global warming, scientists suggest, will not only have a noticeable effect on ocean temperatures, but will also change the acid-alkaline balance, the movement of currents, and the oxygen concentration in the deep layers of the ocean. Such changes, as recently discovered by UK climatologists, could lead to a 20-40% reduction in the number of inhabitants of the middle depths of the world’s oceans.
Wieczynski and his colleagues found that global warming would affect phytoplankton, which inhabits the upper layers of the world’s oceans, just as badly, making it a new source of greenhouse gas emissions, rather than one of the world’s major CO2 sinks. Scientists came to this conclusion while studying the effects of high temperatures and other warming effects on the behavior of so-called mixotrophs.