Deciphering how life worked on this planet during its different epochs is one of the things that Dalton Hardisty works on at Michigan State University.
In fact, he's part of an international research collaboration that recently published work in the prestigious journal Nature, sharing a new approach for studying important chemical and biochemical processes in the Earth's prehistoric past.
He does this as part of a community of paleoceanographers, researchers who can examine ocean sediment like a record book that stretches back nearly 4 billion years.
Hardisty, a Geological Sciences Endowed Professor in the Department of Earth and Environmental Sciences, shared some insights about his new work and his area of study.
What is paleoceanography?
Paleoceanography is the study of the evolution of Earth's oceans through time.
Here at MSU, we focus on the biological and chemical evolution of the ocean. And it's hard to distinguish between the two in lots of cases because they're so intermingled. As life has evolved, it has changed the chemistry of the ocean in dramatic ways and vice versa.
A great example of that is oxygen in our atmosphere and how it has accumulated in the oceans. The evolution of photosynthesis has had major changes on ocean chemistry, but also the evolution of life in certain time periods.
How can paleoceanography help us understand the planet today?
Things used to look very different from today, but they do matter for our present.
Right now, we can go out and observe and sample our oceans and atmosphere in amazing ways. But most observations of the chemistry of the oceans and the atmosphere don't date back much beyond 100 years.
From there, we're really relying on paleoceanography. That's taking sediment records and reconstructing the changes in the chemistry of our oceans and atmosphere over natural warming events and natural increases in carbon dioxide. Then we can understand the baselines to expect and how to separate that noise out from what humans are driving currently.
It also lets us ask really basic questions about how life evolved. Why is Earth special? Is it special? We know that life exists here, and we're curious about where it could exist elsewhere.
As we think about exoplanets and the search for life beyond Earth, the ancient Earth can tell us about planetary conditions that sustain life that are very different from what we see today.
Can you tell us a little bit more about the work that you were part of that was recently published in Nature?
The time period for this publication is around 600 million years ago, and this paper is interesting because there are two key periods, two key events that it looks at.
One is that there is a large change in Earth's carbon budget. Across that same event, there is evidence for a diversification of some of the earliest animal life in the fossil record.
This paper also looks at oxygen and mechanisms that change oxygen, particularly phosphorus. We know that phosphorus is an important control on the availability of oxygen today, so we're asking how important it was across some of these geologic events.
What makes phosphorus important?
Phosphorus is thought to be one of the limiting nutrients for photosynthesis through a lot of Earth's history.
We see this even today with nutrients from fertilizer for our gardens like nitrogen, phosphorus and potassium that can run off into lakes, rivers and oceans. Those nutrients and their availability have long limited the growth of primary producers, organisms that do photosynthesis like algae and cyanobacteria.
For example, in Lake Erie, there are large inputs of phosphorus and, every summer, there are these large algal blooms that change the oxygen concentration in the lake. These are big hypoxic events where a lot of oxygen is lost in the water column and that's linked to phosphorus.
What were the results of your paper?
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What we published is a new geochemical approach in which we looked at phosphorus across those key events in the past. That let us develop a model to look at the impacts of phosphorus on oxygenation, play with it and ask, "Okay, can we actually mimic what we see?"
So there will be a need for some validation that this approach is working across other events. But it's a way to mechanistically understand how phosphorus has changed through Earth's history and how it has - or has not - impacted oxygen accumulation and photosynthesis broadly.
Research Report:Uncovering the Ediacaran phosphorus cycle
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