Ocean plankton absorb less CO2
According to the researchers, the actual amount of carbon dioxide absorbed by the plant plankton in the large portion of the Pacific Ocean is significantly lower than the previous estimates.
Scientists from the United States say that the minute oceanic plants were sequestering almost two billion tons lesser amount of the greenhouse gas. The primary reason for this is the limited content of iron that limits their growth.
The iron deposits give the necessary nutrients to these microorganisms. These in turn grow further by absorbing the carbon dioxide from the atmosphere.
These observations are published in the science journal called Nature.
Roughly fifty billion tons of CO2 is estimated as the amount that is absorbed by the all the ocean bodies across the world. Therefore, the reduced amount may imply almost a four percent decrease in the carbon dioxide that is absorbed, said a team of USA experts.
The tiny plants, known as phytoplankton are an important part of the global carbon dioxide cycle due to their involvement in almost fifty percent of the Earth’s photosynthesis process. Along with the zooplankton, which is minute animals, the phytoplankton forms the foundation of the entire oceanic food ecology.
The lead author Michael Behrenfeld, who is from the Oregon State University mentioned, that the stress created on the phytoplankton due to limited iron made extra glowing green pigments, which were not similar to the normal pigments created.
Dust storms deposit iron particles in the oceans
However, according to him, the satellite images that were used to examine the oceanic plankton blooms were unable to make the distinction. The green color was not indicating the health of the plankton but indicated the stress that was created due to the limited iron content in the oceanic waters.
Professor Behrenfeld along with his colleagues studied information collected over twelve years from thirty-six thousand miles of ships sailing through the tropical part of the Pacific Ocean.
This information enabled them to determine the fluorescent fingerprint on those parts of the sea that was lacking in the required amount of iron. In addition, the locations that were lacking in the nitrogen (which is another key component) were identified.
The professor mentioned that nutrients like nitrogen and phosphorous rise from the bottom of the oceans to feed the upper waters.
In comparison, iron can arise from the depth of the ocean but can also enter the waters from the dust that is deposited by the winds. Behrenfeld added that the windstorms that blew sand and dust from the large deserts were a huge source of iron to the global seas.
Three locations on the Pacific Ocean where phytoplankton was suffering due to limited iron were observed by the scientists. These include the southern ocean around the Antarctica, the sub-arctic region north below Alaska, and a huge area in the tropical Pacific around the equator.
Professor Peter Burkill from the National Oceanography Centre in Southampton, UK welcomed the study. He said that the findings would contribute to the growing understanding of the global waters in the world’s carbon cycle.
The oceanographic research ships that are used for the studies are limited in the operational capacities and are extremely expensive.
Therefore, other options like satellite images were being used. Although, these are not as perfect, however, they do provide the benefits of letting the researchers observe large portions of the oceans.
Several similar types of studies assist in calibrating the models, however, numerous questions, such as the physics of the oceans, and the effects on the carbon that is absorbed, remain unanswered.
Professor Behrenfeld has been a part of other similar studies that involved addition of iron to the oceanic waters to increase its productivity levels.
Although, the iron increased the phytoplankton growth, the results that were observed were not as good as expected.
According to the Professor, inputting iron was a complicated process that results in an explosive growth during the initial phase.
As the iron quantity input increases, the growth of phytoplankton also increases. However, as the plankton grows, the grazers feeding on the phytoplankton also increase because of the increase in the supply of their food.