Biotic and abiotic factors decrease the levels of CO sequestered

Three clusters of bacteria which have no phylogenetic relationship to any other bacteria have been discovered serendipitously by Indian scientists.

The discovery happened during LOHAFEX (Loha means iron in Hindi while Fex is an acronym for fertilisation) experiment in the Southern Ocean, Antarctica, which was aimed at increasing CO sequestration through ocean iron fertilisation as part of studies on global warming mitigation. Though a group of German scientists were also part of the experiment, the discovery was made by Indian scientists, according to one of the investigators and former Scientist of Centre for Cellular and Molecular Biology (CCMB), Dr. S. Shivaji.

Director of National Institute of Oceanography, S.W.A. Naqvi was the principal investigator of the experiment, the results of which were published a few months ago in an open access journal, Frontiers in Microbiology.

In the article, the authors pointed out that oceans are a major source and sink for carbon with the marine phytoplankton fixing up to 40 per cent CO. “Thus factors that hinder CO fixation by marine phytoplankton would impact global climate due to increase in the levels of CO in the atmosphere. Both biotic (grazing of phytoplankton by microzooplankton) and abiotic factors (deficiency in the micronutrient iron) could decrease the levels of CO sequestered. Therefore, the assumption is that if iron deficiency is overcome by exogenous addition of iron, it would facilitate a phytoplankton bloom and thus lead to CO sequestration”, it was noted.

In order to get a better insight into bacteria-phytoplankton relationship in the context of iron fertilisation, the experiment looked at the effect of iron addition on bacterial community structure in the Southern Ocean, Antarctica.

Dr. Shivaji said that upon addition of iron, phytoplankton increased by two-fold and concomitantly a change in the biomass of bacterial community was also noticed.

Among the three new LOHAFEX clusters that were discovered, the first was related to class of Bacteroidetes while the second and third belonged to Firmicutes. A unique and distinct feature of the three clusters was their differentiated response to the presence of iron in the ocean.

While organisms in cluster-1 did not respond to increase or decrease in iron levels, bacterial community in cluster-2 increased with addition of iron and those in cluster-3 disappeared on addition of iron. Thus, organisms in cluster-2 and cluster-3 could be indicators of iron in the ocean.