[Podcast] Imprints: Sifting through microfossils with Rajani Panchang

Microfossils are fossils that need to be studied with the help of a microscope. They are an important feature of our geological record that help scientists reconstruct past climates. They are commonly found in marine environments, but also occur in brackish water, fresh water and terrestrial deposits. To understand the changing environment marine geologists, oceanographers and researchers use these micofossils as palaentological proxies.

Microorganisms are more sensitive to smallest changes in their environment. Since they are also found in abundance, they are good proxies for changing environments and changing climates.

In this episode of Imprints, Mongabay-India Contributing Editor and podcast host, Sahana Ghosh speaks with paleoclimate scientist, oceanographer and micropalaentologist Rajani Panchang from Savitribai Phule Pune University, to understand how the remains of tiny organisms give us ideas about the chemistry and temperature of the ocean, ocean currents, wind patterns of the past, human influence on the ecosystem and more. Panchang also talks about the challenges in her field visits, her sailing experiences and the interesting findings about changing mangrove ecosystems.

Listen here:

Full transcript:

Sahana Ghosh (SG): You are listening to Everything Environment by Mongabay-India. In a dot of sediment you may find thousands of tiny remains of bacteria, protists, fungi, animals and plants. All of these are microfossils. Looking at sediments under a microscope is a window into the past environments and climates.

Our guest today, is an oceanographer and micropaleontologist. She is Rajani Panchang. She uses microfossils from oceans, of tiny marine organisms, to interpret how the climate and environment may have been when they were alive. Her work gives us ideas about the chemistry and temperature of the ocean, ocean currents and wind patterns of the past.

One of the most widely studied microfossils belongs to organisms called, foramenifera, amoeba-like, single-celled organisms that have a protective shell enclosing a soft body. So, what makes them special and why do they become clue for Rajani? You’ll hear from her during this episode.

With the ocean as her field, Rajani is focused on understanding several pertinent issues – ocean acidification, environmental pollution and sea level fluctuations. Paleoclimate research eventually feed into reports that give us the large picture of climate change and our means to recovery. 

It starts with studying sediments.

In this episode of Imprints, we speak to Rajani at Savitribai Phule Pune University about her penchant to explore the oceans, from the coast to its deeps, looking for past climatic records. We’ll hear about her extensive sailing field trips and experiences on the field looking for microfossils, including how she aced walking on mudflats. What does the rich expertise of India’s fisher community teach us about our vast coast and how do results of paleoclimate science help human society in natural resource management?

A quick note before we begin – if you haven’t heard the previous episodes of Imprints, please listen to them and be amazed by the work of paleoscientists. The order of listening does not matter.

SG: Hi Rajani, welcome to our podcast Imprints.

Rajani Panchang (RP): Thank you. Thank you for having me.

SG: Rajani I am so glad to have an oceanographer and a micropalaeontologist in our midst. You look at remains of really tiny organisms in the seascapes. Reading about your research made me realise that we really need to focus on these very specific microfossils?  What is the reason that we need to focus on these microfossils and that too in the ocean?

RP: Okay, everyone knows about palaeontology. And we know that fossils or the study of fossils are called palaeontology, paleo and antos. Paleo is passed on to us as life or remains of bones. And micropaleontology is a branch of palaeontology. for a very long time, people just did palaeontology because they were fascinated by fossils. And you know, wanting to know something about this is what past life looks like. I think it was Jurassic Park, the movie, which actually made people understand more about dinosaur fossils, and know that the dinosaurs were not a myth. And it’s actually something. So somewhere, I think people who were trying to understand the evolution of life, for a very long time, have looked at palaeontology, just for the evolution of life. But in an era, when we are talking about climate change, where we are talking about how environments are changing, I think palaeontology has a very, very different dimension.

What you study in micropaleontology? You study small organisms, they could be unicellular, they could be multicellular, but they’re really microscopic. And the something that everyone should know is smaller organisms occur in more abundance, whereas bigger organisms occur in less abundance. So, if you’re looking for a mammoth, fossil mammoth, or fossil dinosaur, in a large area, you will probably find one or two of them. But when you go into micropaleontology, when you look for fossil remains of microscopic organisms in a small amount of sample, I would find thousands of them.

So, what happens is, you’re getting more observation points.

They’re statistically more reliable. You can see more data in a small amount of sample. That is one. Another thing that happens with micropaleontology is that it gives statistically reliable, more observable data points. Apart from that, whenever there is anything big, for example, a human body being preserved in sediments in rocks, with time, it can get disjointed. It would break apart into different bones, the fingers would move away from you know, the arm and the main body. So, these can get disintegrated and transported. But the same thing whenever there is an organism, which is very, very small, it has chances of being preserved in its entirety. Complete preservation is possible. And that’s the main reason that microfossils are more reliable, better proxies.

A proxy, it is something that vouches, or it gives us an indication of the environment which existed in the past.

Okay, now, why micropaleontology?

Another thing is, because a very small, they are more sensitive. Because they’re very, very small, they are more sensitive to smallest changes in their environment, for example, you and me, we are bigger organisms. So, small changes won’t affect us. But if there is a smaller organism, and there’s a very small change, they will detect faster, and they will also adapt or go extinct. And that’s why microfossils or microorganisms are better proxies for changing environments and changing climates. And that’s why people should know about it.

SG: Right, people should definitely know about microfossils. How can these tiny remains of these organisms be integrated with observations of Earth’s modern climate? How can we place them into a computer model to figure out past as well as predict future climate.

RP: Let us go about the different kinds of organisms. For example, the most widely microfossil proxy are foraminifera, okay, which are calcium carbonate shelled organisms, which are exclusively marine. Similarly, you have diatoms – they are unicellular algae, which have a skeleton which is made up of silica and they are found trans environments they are found right in freshwater lakes, to the mixed water system mixed salinity systems to oceanic systems. You have different organisms coming from different kinds of environments. They all are sensitive to something or the other. I’m going to mainly speak about foraminifera. I’m a foraminiferologist. So, I will have lots of examples to get from there.

Foraminifera for example, is made up of calcium carbonate. It’s like an amoeba. It’s like a unicellular organism which is an amoeba. It secretes its shell using calcium carbonate, which is there in the water. So, when it does that, what does it take in? It takes in calcium, and it takes in oxygen, and it takes in carbon dioxide and forms a calcium carbonate shell.

So, the shell chemistry is in equilibrium with the chemistry of the water during their lifetime.

It is not just their presence and absence. climate models need quantitative data. For example, whenever you’re doing computer simulation, you are saying if one degree temperature increases, how are the wind patterns going to change? How are the current patterns going to change? How is the marine resource going to change? So, all this when people do models, they put in variables, they put in variables like pH, they put in variables like temperature, salinity, wind force, wind strength, all these things. You can use these micro fossils, which have been deposited over time (Micro fossils are deposited at different times.) So, depending upon what is your time of interest, I’m trying to look at what happened 10,000 years ago, or I’m trying to look at what happened 1 million years ago, or what happened in the past 100 years — I choose my location of study. And there what happens is we know that sediments are deposited layer by layer with time.

Now, in these sediments… what are sediments when these microorganisms die, they behave like a sand grain, they are transported by water, right? So, they get deposited also. If 10,000 years ago, there was a sediment layer that was deposited, that is when even those micro fossils get deposited, along with time. This is how we get our data. These organisms, when they are alive, indicate the environment of when they were alive. So, geochemical markers within these microscopic shells are very, very helpful in providing quantitative data  – numbers –  which people need for modelling, and that is how these both are correlated.

If you look at India, Indian instrumental records exist of the past about 150- 200 years, on whatever meteorological data because most of our observation sites or climate observation sites, were started by the British. And that is what we have since the late 18th-century and early 19th century, IMD has records since 1900 – 1901, you will find records on their websites.

So, that’s why we are looking at data which can take us beyond the time of instruments, so that we can get long-term proxy records. What is the idea behind that? The idea is more the data points you have, the better the prediction. For example, if I have known you for 10 years, I can say with more reliability, that this is how Sahana’s nature is, or this is how she will react in this situation. Right? That is the same thing that we also want to do- the longer that I know, how is nature’s natural variability? On the basis of that I can be more reliable in my predictability. And that is why people have started looking at proxy reports.

SG: So, from what you spoke about foraminifera and other such microfossils, it looks like time is trapped in these sediments. That makes me wonder, what was the trigger or prompt for you to get into paleoclimate studies? What was that one reason that really provoked you to look into paleoclimate studies?

RP: I remember when I started working, I’ve always been interested in when humans started altering ecosystem. Because we’re all talking about anthropogenic pressures, human pressures. And as a geologist, when I speak in terms of millions of years, people are like Kya baat kar rahi hai, millions of years pahle ka kyu janna hai? (why do you want to know what happened millions of years ago?), you know, what’s going to happen after 1 million years. So, people are like, we don’t know if we are going to be existing 1 million years later, which I always found when I was working with Dr. Rajiv Nigam on my Ph.D. in the National Institute of Oceanography, the best part that I liked was this is a science which can help human society, it can help in resource management.

And because when we make budgets, when we make any constructions … when you build harbours, you build jetties. When we do that, we spend in crores and 1000s of crores of rupees in infrastructure development and in coastal development. So, you want the best quality you want the lowest bidder, but still even the lowest bidder is going to take thousands of crores of rupees. When we are developing something we say “agale 200 saal tak kuch nai karna padega, agale 50 saal tak kuch nai  karna padega, agale 100 saal tak kuch nai karna padega” (for the next 200 years nothing needs to be done, for the next 50 years nothing needs to be done, for next 100 years nothing needs to done).

But if we get to know what the IPCC report says that by 2050, Bombay (Mumbai) is going to be submerged underwater. By 2050 Chennai or Kolkata is going to be underwater. Then do we want to spend so much money? So, that is when I got attracted to this, and that’s the reason that I started working along the coastline of Maharashtra.

When I’m looking for paleoclimatic records, I need undisturbed records. Because they can’t be mixed up. If they’re mixed up, my dates will all be mixed up. So, wherever I have gone I have always seen that I’m going to locations which are pristine, where human intervention is the least.

SG: So, you really are trying to think about the future, right? And help in resource management. We are going to spend huge amounts of money in infrastructure and coastal development. So, how do we do it the best way? How do we ensure that they remain standing there for many decades? This is where all the drama plays out in the oceans, for you, as a career micropalaeontologist. And in your toolkit as you mentioned, undisturbed ocean sediments play an important role. What brought you to the Maharashtra coastline, as a researcher in the first place?

RP: So, I started looking at estuaries. Estuaries are river bodies, which go and meet the sea. And you have a lot of mangroves on either side. And there has been a lot of hue and cry about mangroves being cleared off especially in the name of industrialisation and exploitation of resources. So, yes, in the past, since about 2012, I have been working along a few estuaries of Maharashtra, especially the Kundalika, the Vashishti and Achra. Vashishti in Ratnagiri faces different pressures like construction of dams. And 64 villages along the Vashishti river, giving up inland fishing? There has been a dietary switch.

My main idea was when did this happened historically, when did this all start happening? So, dam construction as the major issue in Vashishti. Achra was the most pristine but a very small estuary. So, I was using it as a control estuary, whereas Kundalika was facing different kinds of problems from the chemical and fertilizer industry. So, they were all different.

I was trying to understand, especially since 1900, or the past 100 or 200 years, I was trying to understand, ‘can I set a boundary for the anthropocene?’ Because there are different definitions for the anthropocene, but I look at the Anthropocene as – ‘When did man start changing ecosystems? When did the natural climatic variability change?’

I’m working on two projects. One, I’m looking at ocean acidification in the Arabian Sea, where I’m collecting samples from offshore India around the Gulf of Kachchh and, Gulf of Cambay. And I’m also looking at the coast of Oman. I’m looking at samples from the coast of Oman (That is the Eastern Arabian Sea and Western Arabian Sea). I’m comparing them and looking at how ocean acidification varied over the past 30,000 years.

Okay, 30,000 years is because that is when the last ice age changed and came into the recent warming. So, our oldest civilisations are known to be around 7,000- 8,000 years old. So since then, how has the monsoon changed?

There are several factors which affect ocean acidification. I’m trying to see recent trends of ocean acidification, how are they different from historical trends? Another work that I’m doing is trying to understand sea level fluctuations along the Mahanadi delta. I’m also working along the Mahanadi delta, where I’m seeing how the Delta has changed and civilisations along the Delta have been affected because of sea level fluctuations.

SG: So, I remember from our earlier conversations, you’ve narrated your memories and experiences of sailing. Your memories of being in mangroves and working in these landscapes. Are there any specific field experiences that you think define your work?

RP: I’m a field person, okay. And I think I took up geology because it took me out into the field. I have sailed tremendously also. Right from the deep waters to shallow waters. My, my PhD area was Burma. I worked on the Burmese exclusive economic zone, and from there I have also worked in Lakshadweep islands. I have worked on mangrove ecosystems; I’ve worked on corals, and I’ve worked on mangroves both. I think I’ve really been lucky or maybe I’m a person who chooses things on my own. I like to explore things which are not always very common. And when I do this, yes, I go out and see.

And I think each experience has been different. You interact with people, especially when you’re working in the inland regions. For example, when I went into Chilika lake, it was the locals who helped me. When I was at National Institute of Oceanography, huge oceanographic Institutes have their own vessels (ships). So, the longest ship, my favourite ship has been Sagar Kanya – ORV Sagar Kanya, which is a Ministry of Earth Sciences (MoES) owned vessel. I have sailed a lot on her.  But it is it a 100-metre floating ship in the middle of the sea, okay. And that is when I can go in, I can collect six-metre to 12-metre-long sediment cores. But when you want to do the same in marshy areas, like the inland estuaries, which are not very deep – (these estuaries are like I have worked in four-metre depth to about 20 metres depth) – that is where your big ships can’t go. So, even that time I have used small boats, small fishermen trawlers.

I have built platforms, by tying two trawlers together or tying two boats together, constructed my own coring equipment to get shallow water cores. Because the equipment itself is about when you start constructing it comes up to 200- 300 kgs and your boat is very small (six metres to 10 metres). So, there is a fear of it being overturned. I have done a lot of interaction with local fishermen because they are the people who know their seas and their waters very, very well.

It was the fishermen who taught me how to walk in tidal flats. Tidal flats are marshy lands, when you walk into them, your foot sinks, right till your knee. Okay, so you go right in, and if you don’t walk properly, you will come out with a broken bone. Okay, so it is with them that I learned where to wade, where not to wade, how to pull yourself out, observe so much, which is even in the intertidal region, you don’t need to go deep.

SG: So, as a researcher working for a long time in these sites, you’ve really seen the changes that happen in the mangrove ecosystem. You’ve spoken about mangrove degradation due to development in one of your popular science writings. So, could you give us a snapshot of how these field sites have changed over the years that you’ve seen them in your fieldwork?

RP: Actually, if you go back and look at reports, whatever I’m talking to you about is very recently, I would say in the past about after 2014 or 2015, I see a change, okay. And I see a change in locals being involved in resource management. For example, when I went, it was very, very interesting to note, I worked in Lakshadweep. And it’s very interesting to know that local people there are employed, they may not be very educated, they would be in school, they would have passed their 10th or 12th grade, but they are involved in conservation activities. They are educated by the local science and technology departments that “if these corals don’t live, you won’t live. They are your resources. They are your source of life. So, you need to sustainably use them.”

Because I remember when I went to Lakshadweep in 2004 and 2005, they would cut out the dead coral and build houses. But now they look for different alternatives. But at least they know that “I shouldn’t dredge my lagoon. If I dredged my lagoon it’s going to destroy the coral reef habitat.”

They are involved in coral census. They are also involved; they see to it that no one is plucking the coral. No one is breaking the coral. And at least they themselves don’t offer any momento in the form of coral or coral organisms and shells. That is the same thing I think when I’m seeing Vashishti.

The problem with Vashishti, different. What I can see is I can see a lot of biofoulings. That was really sad that I saw. In the middle stretches of the Vashishti, I saw organisms which shouldn’t be there — that is Saccostrea cucullate. It is a kind of oyster which generally attaches itself to hard substratum, mainly rocks and you will very commonly see them along jetties and bridges and harbour or even any rocky substrates. I saw an abundant, abundant, abundant fouling on mangrove trees. This was in the middle of the estuary, which is a brackish water environment.

So, S. cucullate has higher salinity and finding them along the coastline was okay. But I was finding this almost 10 to 12 kilometres inland, in a brackish water system where I am expecting water to flush out all the impurities. But what is it? It’s a S. cucullate, these bivalves shells are bio accumulators. What do they do? They are filter feeders and when they feed phytoplankton from the water, they are also taking in a lot of metal. They are bio accumulating metal within them. So, they’re indicators of metal pollution.

They are present at a place where they shouldn’t be because they’re getting a lot of metal and you know, so they are tolerant to that. They’re indicating that they’re there. But when they start attaching themselves to mangroves, they reduce the physiological capacity of mangroves, and their soil holding capacity. So, because of that those mangroves start falling off, they can’t hold on to soil so much. Then along with the tide, the soil, which is being held on to by the mangroves, the mangroves dry out, their physiological capacities fall, they don’t hold on to the soils. Mangroves get washed away, along with the sediments. So that is one issue, that I’m seeing, which is happening. The metal is coming down from the different factories in that region, maybe. But I have no idea.

SG: You speak with a certain joy about samples, about undisturbed records of this past. And looking at the past through the lens of these microfossils. But you do have challenges when you want to access these specific samples. So, what are those challenges that you really want to circumvent to access these samples and keep your research going?

RP: Science needs access to samples, right? So, I’m not saying go rampantly and go and just collect samples from anywhere. If I didn’t have local people, I would never be able to collect cores and samples from these estuaries. So that’s one challenge that I face. If I want to go deep into the ocean, I have different vessels and ships. During the COVID pandemic, that was a big challenge. There were no vessels working even from the Government of India travel restrictions were there. So that is when I couldn’t sail. So yes, having opportunities to sail, having infrastructure to sail, be it in shallow water condition or deep-water conditions, they are available to very few people or with very few organisations. So that’s a big challenge that we do face.

For a person like me, who’s working in the ocean, if I will try to locate a region which is continuously going to be dredged for developmental activity, or if I’m going to lose it to any oil pipeline laying any developmental activity in the ocean, it could affect micro paleontological records.

SG: And in one of your articles you’ve so eloquently stated that sediments reveal the truth that humans lie about. So, what is the truth? And what are the lies?

RP: There is something which we have been talking about called Bio Monitoring. Long, long ago in 2003, I was presenting this work ‘fororaminifera, as a tool in ecotoxicology’ — That is environmental pollution or environmental toxicology. So, I was using the same microfossils and I was trying to show their potential in indicating environmental pollution.

If you go back and take a sediment core, it can actually help us pinpoint it — “Was it man? Which activity of man? Is it climate?” And I call this sediment forensics, okay, because the shells are nothing but biogenic sediments. And they can be used as a tool and they’re much cheaper. The main problem is like I was telling you, why would someone lie about it, it’s very easy to lie. For example, in my backyard, I have a river, which is a flowing river, right. So, I just go in and dump a lot of waste products there waste chemicals there. And when someone complains about me, they go and say, Oh, this lady is, you know, yesterday, she has dumped so many metric tons of chemicals in there. And the next day, the pollution control board comes, and it collects water. And the water is pristine, it’s clear, obviously, it’s going to be clear, because it’s a flowing water body.

It’s a flowing water body, the water has gone away, okay, and it has taken away all the pollutants along with that. But that doesn’t mean I keep polluting my water bodies. Because eventually these rivers and these estuaries are going to meet the sea. And the sea has a lot more resources, right, which is, so here, your microfossils can help because what happens to microfossils, they live and die, and they accumulate in the same environment. And that’s why I say that if you have these sediment cores, they can actually tell you what caused what event or what change in the environment.

If you understand processes which are ongoing today, this knowledge will help us when we are doing past climate reconstructions, because when you do past climate reconstructions, there are going to be times when abundance is increased, abundance is reduced. Diversities were completely switched over by some other diversity. I was telling you about these microscopic organisms, they are so sensitive, that if I start looking at the beach, in the intertidal zone, you have different species in just in the shallow water regions, you have different species, you go on to the open ocean, in the middle of the shelf, you have different species at 1,000-metre depth, you have different species.

So, you have these organisms, the number of species like for example, camels, found in deserts, polar bears, found in, you know, permafrost conditions. Similarly, these microscopic organisms are so sensitive, that they tell us about changes in the environment. And that is what only if you understand modern processes, what is happening today, you can use that knowledge in reconstructing the past.

SG: With the initiation of the UN Decade of Ecosystem Restoration, do you see more focus on oceans? Or to put it in another way, do you envision that oceans are going to become more prominent in the coming decades, in research and policy making?

RP: I must say that, when you go on and look at the mandate of the UN Decade, you will see that they keep on harping, or they keep on saying that, we need sustainable oceans, about sustainable development, we’re talking about sustainable oceans. And they talk about multiple stressors. They haven’t explicitly said anywhere that it’s the climate that we need to look at. But they surely keep talking about multiple stressors that are affecting. But when we are doing that, it is not very clearly spelled out. But I really do see a lot more funds coming in into ocean science. When you write research projects, when you have people working, more and more governments are putting in scholarships, funding research funds and conservation efforts in oceans.

I think paleoclimate is surely, if you look at the Ministry of Earth Sciences website, they do really fund… But if you come up with really, what are the questions which are not known? More and more people are trying to delve into this. Earlier people only talking about monsoons. Now people are looking at how the oceans, the Indian Ocean is connected to the North Atlantic. How are changes in the North Atlantic affecting climates In India? How is something happening in India affecting the Pacific? Because they all know that it is one ocean, and whatever is happening in India is an effect of something happening somewhere else. So yes, I surely do think that this is a great opportunity. And though it is not explicitly said anywhere, I know from experience that paleoclimate is being given a lot of impetus, and it has a lot of scope, a lot of projects being given out.

And it’s amazing to see how the newer generation thinks of, you know, better teleconnections between climate and they see that ocean sediments can have the signatures of these changing climates. So yes, I do think it’s a big impetus.

SG: I am loving your optimism about bringing oceans into focus. And I can see the reasons you’ve spelt out about why these oceans really needed to be brought under the radar, in terms of research and policy.

Someday, you’re going to have to show me the trick to walk along those mudflats.  You will have to divulge your secret soon! Thanks for the interesting chat, Rajini. And for taking us along these oceans and letting us glimpse these microfossils that tell us so much about our past. This will hopefully lead us to being better at policymaking as well.

RP: Thank you so much for having me on board.

SG: In our next episode, we’ll hike to the Himalayas and other remote regions in India with paleoclimatologist Anoop Ambili, to explore lakes and the climate stories they tell us.

Please share this episode and subscribe to our podcast, Everything Environment by Mongabay-India.

This episode was hosted and produced by me, Sahana Ghosh. Co-produced by Kartik Chandramouli. Edited by Tejas Dayanand Sagar. Cover art by Kartik Chandramouli. Copy edits by Sapna Verma and Priyanka Shankar.

Listen: [Podcast] Imprints: Finding molluscs with Devapriya Chattopadhyay

Banner image: Rajani Panchang and her team assembling a coring platform at sea and (right) pteropoda. Photos from Rajani Panchang.