New progress has been made in the study of bacterial particles and organic matter in the upper layer of the West Pacific Nuan Pond area

Recently, the team of Song Jinming, a researcher at the Institute of Oceanology, Chinese Academy of Sciences, cooperated with the Helmholtz Center for Ocean Research in Germany to publish research results in the international geoscience nature index journal Geophysical Research Letters, reporting new insights into the abundance and activity of bacterial particles in the West Pacific Warm Pool area and their contribution to carbon storage by marine carbon pumps. 

The ocean is the largest reservoir of carbon in the earth’s surface system and plays an important role in the global carbon cycle and climate change. Phytoplankton on the surface of the ocean convert carbon dioxide into granular organic carbon through photosynthesis, which sinks to the interior of the ocean under gravity after undergoing a series of complex processes, which is vividly summarized as a biocarbon pump and is one of the most important marine carbon storage mechanisms.

Biochar pumps are generally less efficient, with most of the particulate organic matter being degraded by bacteria in the upper ocean, with only about 10% being exported below about 1,000 meters below the middle ocean, and less than 1% eventually reaching sediment for burial. However, the mechanism of degradation and transformation of organic matter by bacteria is not clear, bacteria are both degraders and contributors of organic matter, and the important function of bacteria can also convert active organic matter into inert bacterial debris, thereby helping carbon sequestration and increasing marine carbon sink.

Therefore, the abundance and activity of organic matter of bacterial particles have become key factors affecting the carbon storage efficiency of biocarbon pumps. But until now, little is known about the bacterial organic matter cycling process in the water column and its contribution to the biochar pump.

Degradation and transformation of particulate organic carbon by bacteria Photo courtesy of the Institute of Oceanography

Based on this, Song Jinming’s research team explored the abundance and activity of bacterial particle organic matter by analyzing the changes of bacterial biomarker D-amino acids on two water-column suspended particulate matter collected in the West Pacific Nuanchi area.

The study found that about 27% of the particulate organic carbon and about 39% of the particulate nitrogen in the surface layer of the West Pacific warm pond came from bacteria. However, about 87% of most bacterial particle organic matter has easily degradable or semi-degradable characteristics, and about 85% of bacterial particle organic matter is removed between 100~300 meters depth. The rapid removal of bacterial particulate organic matter in the upper ocean may be related to the oligotrophic characteristics of the Western Pacific warm pond area. Under oligotrophic conditions, large amounts of bacterial organic matter are consumed by respiration for energy supply rather than bacterial biomass production.

In addition, the high temperature in the West Pacific Warm Pool area further enhances the respiratory consumption of bacterial organic matter, resulting in only ~8% bacterial organic matter contributing to long-term carbon sequestration. This result shows that bacterial granular organic matter may contribute limited to carbon storage by biocarbon pumps in oligotrophic sea areas, which has important scientific value for the analysis of the open ocean carbon sequestration process and the accurate assessment of ocean carbon sequestration potential. 

The research was supported by the National Natural Science Foundation of China and the Category A Pilot Special Project of the Chinese Academy of Sciences. (Source: China Science News, Liao Yang, Wang Min)

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