When in Earth’s history did the ‘rise of the algae’ occur, i.e. the basic element of modern marine ecosystems? A new study uses a mathematical model of the ancient ocean ecosystem to explore a one-billion-year gap in the geological record.
When in geological times did modern algae begin to dominate the ocean? While we know that modern eukaryotic algae evolved about two billion years ago, we have, so far, been unable to find solid evidence of them in the geological record until almost another billion years later.
Is that because they left no trace, or did it take a billion years for them to dominate?
This question is at the heart of a recent scientific study that uses a mathematical model of the ancient ocean ecosystem to explore this one-billion-year gap in the geological record. The study is led by the NordCee group at University of Southern Denmark and in collaboration with DTU Aqua.
The study is published in PNAS under the heading: A case for an active eukaryotic marine biosphere during the Proterozoic era
The same constraints as two billion years ago
The mathematical model of the ancient ocean ecosystem, developed at the Center for Ocean Life at DTU Aqua, is unique by being based upon the physical constraints of the unicellular organisms. Constraints which have been unaltered throughout the Earth’s geological history.
According to the model, microbial ecosystems similar to modern ecosystems could indeed have appeared in the ancient Proterozoic ocean.
This is the case if the ancient eukaryotic algae were also able to perform photosynthesis.
We therefore have reason to believe that modern food chains with primary producers, green algae, predators, and decomposers have been present on Earth for more than 1 billion years.
Thus, the new study shows that marine ecosystems from 1,700 to 780 Ma were far more active and diverse than generally thought.
Predicting climate change
Eukaryotes dominate marine ecosystems today, driving carbon and nutrient cycles. Understanding the Earth’s ancient ecosystems is helpful for our ability to predict how the Earth’s ecosystems will develop under climate change.
FOTO: Mikael Van Deurs