Canadian researchers have uncovered new clues about ancient marine life by investigating the Lake Kivu in the Democratic Republic of Congo and reveal that quantity of nitrogen in ocean between one and two billion years ago may have been greater than previously thought.

Researchers published their findings in journal Nature Geoscience wherein they have noted that the abundance of nitrogen during the Proterozoic eon, some 2.3 to 0.5 billion years ago could have been the reason why marine organisms proliferated at a time when multi-cellularity and eukaryotic life first emerged.

For the purpose of the study University of British Columbia scientists travelled to Lake Kivu in the Democratic Republic of Congo because the lake bears similarity in chemistry to the oceans of the Proterozoic eon. The deep waters of part of the lake have no oxygen and are one of the few places on Earth where dissolved iron is present at high concentrations.

Céline Michiels, lead author of the study and PhD student at UBC, says they have observed microbes recycling nitrogen by reacting it with iron in such a body of water for the first time. Though in lab conditions such an activity has been observed, the activity in the natural setting provides us with clues that they can play an important role in natural ecosystems. The findings enabled scientists to build math models that can describe these reactions in oceans of the past.

Michiels and her colleagues found that when microorganisms from Lake Kivu react iron with nitrogen in the form of nitrate, some of this nitrogen is converted to gas, which is lost to the atmosphere, but the rest of the nitrogen is recycled from nitrate to ammonium, which remains dissolved and available for diverse microorganisms to use as a nutrient.

The research team used math models, informed by data collected from lake Kivu, to learn more about how this recycling could have affected life in the oceans during the Proterozoic eon. They learned that biological activity was not limited by the availability of nitrogen, as previously thought, but rather was likely limited by another key nutrient, phosphorous. Nutrient availability would have played an important role in shaping the nature and activity of life in the oceans at this time, thus setting the stage for the evolution of multicellular life and Eukaryotes.

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