Tuesday, 29 September 2009 08:00 Carbonate Surprises
Written by Ava

He may be a geologist and carbonate sedimentologist who believes his PhD had a large focus on marine geology because the carbonate sediments he studied were the remains of an ancient marine environment.  But that's not all that's got us hooked on Suvrat Kher, the geology blogger who likes to write posts on his blog, Reporting on a Revolution, on everything from carbonate geology to climate change to evolution.  

He also speaks his mind on ocean acidification, which relate to his carbonate work, as an even a slight decrease in pH may cause a decrease in available carbonate ions used to build calcium carbonate skeletons. And of course, Suvrat is an avid believer that speaking your mind (whether by blog or other means) will help us change the marine world.  After all, he did help spark a change while blogging about the current water crises in India.  

We've always known a voice can make a different.  But who knew that voice would be one of a geologist--one who has proven the carbonate geology he studies relates so much to marine ecosystems. The Reef Tank is happy to learn all about it and Suvrat is here to tell us all he knows.

Tell me about your background in geology and if you have any specific research/stories of marine geology.

I have a dual specialization in carbonate sedimentology and geographic information systems / remote sensing. For a long time I could not decide which to take up for a PhD, but I finally settled on a problem in carbonate sedimentology. As it happened after I finished I could not get a job as a sedimentary geologist and ended up working in geographic information systems! So it’s been an interesting ride. 

In a sense my PhD was on marine geology since the carbonate sediments I studied are remnants of an ancient marine environment. Also I used to help my adviser teach a course on modern depositional systems. We used to take students to the Florida Keys and show them the various environments where sediments accumulate and then compare them to more ancient analogs exposed along the south Florida coast.

You don’t currently work in the field, but you avidly follow carbonate geology and have a PhD in the topic. Explain what it is and how it relates particularly to marine environments.

Yes, I have never been able to tear myself away from carbonates and I do try to keep up with the research literature as much as I can and blog about it (examples here and here). Carbonate geology or more specifically carbonate sedimentology is the study of the origin, deposition, distribution and post depositional changes to carbonate sediments i.e. sediment made up primarily of calcium carbonate and calcium magnesium carbonate. This would include skeletons of organisms, carbonate mud and chemical precipitates. 

The bulk of the accumulation of carbonate sediments throughout earth history has taken place in marine environments. Shallow tropical zone sea water is saturated with calcium carbonate and by latest Neoproterozoic - early Cambrian multicellular organisms evolved the ability to extract that calcium carbonate and build skeletons. This led to the establishment of a particular ecologic niche – the shallow shelf area which includes reefs- where prolific biological productivity leads to the accumulation of vast thickness of carbonate sediment. The deeper marine environments also accumulate carbonates mostly through the fallout of calcareous skeletons of plankton. Before skeletonization evolved in the earlier Proterozoic, marine shelf areas accumulated calcium carbonate microbial and chemical precipitates. So carbonates have always been a common feature of marine environments from the time stable continents formed by the late Archean.

What has your carbonate research told you about the current state of the marine world?

That it is likely to get damaged over the short term but will be resilient over a geological time scale! Observing the ancient carbonate rock record one cannot help feel impressed by the complexity of marine ecosystems. Reef and shelf communities evolve and persist for long periods. The same rock record also warns us that these long lasting communities can get wiped out by sudden disturbances. Usually in the ancient record that means a sudden sea level rise or fall. Looking at the modern seas I always think of the historical rise and fall of marine ecosystems. For example if you look at many of the modern reef and associated marine communities they have developed over only the last few  thousand years after the Holocene sea level rise inundated shallow shelf areas. Purely from a geological perspective that leaves room for optimism, since even after major community collapse, survivor fauna has rebuilt complex carbonate ecosystems relatively rapidly. But on a human time scale there is no comfort in that thought.

On your blog, you often write about climate change.  How has it affected the marine world, particularly through what you’ve noticed with carbonate systems? 

Marine ecosystems exist within particular ranges of water depth, temperature and water chemistry. All three will undergo changes with climate change. While the current marine communities might tolerate a 1-2 meter changes in water depth they may suffer damage due to small increase in temperature or changes in water chemistry for example acidification of the ocean. An increase in water temperature causes many species of corals to expel the symbiotic algae that live inside their skeletons. This causes the well known bleaching of corals. Symbiotic algae also supply many species of corals with the carbon used to build calcium carbonate skeletons. If that carbon supply dries up that makes the corals especially susceptible to ocean acidification. 

What are some other factors affecting the marine environment that you’ve notice through your research in carbonate sedimentology?

Not just my research, but a general awareness of the environment makes one notice the many problems marine ecosystems face. For example along the Indian coasts industrial effluents are polluting coastal marine communities. Increased ship traffic disturbs marine mammals and offshore drilling especially along the east coast of India is raising concerns for the safety of the migratory routes and nesting sites of the Olive Ridley Turtles. Along with this is the continuing larger tourist footprint in Andaman Nicobar islands and Lakshadweep, both of which are famous for coral reefs.

What are your thoughts on ocean acidification and underground CO2 storage, as you’ve mentioned in a recent post? 

Ocean acidification refers to a slight lowering of pH causing sea water to shift to the acidic end of the pH scale, although the actual pH may still be alkaline. Anyway, even a slight decrease in pH may cause a decrease in the availability of carbonate ions that are used to build calcium carbonate skeletons. Damage to coral reefs gets the most publicity but another potential and widespread problem may be caused by damage to calcareous plankton that is at the base of the food chain. If they suffer from de-skeletonization they would have no protection against protozoa who feed on them. That could change the dynamics of the ocean food chain. There may be groups of organisms that resist acidification to various extents. I expect conservation strategies to focus on identifying and protecting such species.

Regarding CO2 storage I had mentioned that idea more in the context of how geological knowledge is going to be of importance in tackling various climate related problems. I am not very knowledgeable about the complex economic arguments regarding the viability of CO2 storage. But I did read estimates that if the price of CO2 emissions realized through a carbon tax /quotas rose to about $ 40/- per ton then CCS (carbon capture and sequestration) may become feasible. Both China and India have plans to build several hundred coal fired power plants in the next two decades or so. A serious effort to increase solar and wind power will alleviate emissions to some extent, but will not solve the problem entirely. So CCS should not be discounted as low emissions strategy. 

You also blog on evolution. How important was/is marine life and marine ecosystems to the theory of evolution and why? 

Evolution is a topic I got interested in because of my PhD advisor. He works in both sedimentology and paleontology and uses foraminifera to understand evolution. 

Most of the record of ancient life is preserved in marine deposits. Terrestrial environments are not very conducive to the preservation of dead organisms. Marine environments are relatively better. Also before the Ordovician- Silurian the only record of macroscopic life is from marine deposits. That makes marine ecosystems of primary importance for studying the evolution of life.

Marine depositional basins may last for tens of millions of years. Within these basins sediments are deposited as packages during sea level rise and are separated by unconformities (periods of non deposition) that develop during sea level fall. If you take large enough time slices then these packets of sediment are roughly contemporaneous over large regions of the globe. In shallow water settings we thus have a fossil record of benthic ecosystems / communities which often persist for tens of thousands of years separated by gaps in the fossil record. So even though the shallow marine fossil record is incomplete it tends to be incomplete in a rather useful way. For example even though soft bodied organisms don’t get preserved commonly and there is a bias towards the preservation of only the skeletal remains, studies have shown that skeletal fossil communities are consistently representative of the living communities. This means we get a good understanding of biodiversity.  And having a fairly representative sample in successive time horizons lets us study macro evolutionary changes within any particular group of organisms. 

The plankton ecosystem offers an even better resolution. Since the calcareous skeletons of plankton settle often in deeper environments where the fossil preservation potential is better and the sediment record is more complete, we can often track the evolution of individual species through time by tracing lineages i.e. ancestor descendant populations. That allows us to recognize micro evolutionary trends and apply finer grained tests to the theory of evolution. See these examples of such work by my adviser – here and here.       

Has your geological findings helped you to uncover ways that the general public can help preserve marine environments for the future?

I will give an unusual example.  A couple of years ago a controversy erupted in India about a plan to dredge a shipping channel through the Palk Strait, a narrow body of water separating India and Sri Lanka. Now that strip of water is of religious significance to Hindus since many believe that King Ram (a very important Hindu deity) crossed over to Sri Lanka (about 3000 years ago the story goes) by building a causeway in the sea. Today there is a chain of coral islands that believers say are remnants of that bridge. I wrote a couple of posts (here and here) explaining the geology and found that many people were being swayed into protecting that environment not by religious sentiments but by appreciating that geological and biological processes have taken thousands of years to build that fragile complex ecosystem.

Tell me about some of the “water crises” you’ve blogged on (like India) and why they are happening.

India is facing a multitude of water problems. First there is the problem of water quality. Environmental regulation is new to India and is weakly implemented and that means that almost all the major rivers and lakes are polluted to unacceptable levels. Wetlands are disappearing through uncontrolled and unplanned development. Even an iconic wetland like the famous Bharatpur Bird Sanctuary is threatened.

Second is the impact of climate change on surficial water. If trends observed in the decline of Himalayan glaciers hold over the next couple of decades it would affect the summer runoff of Himalayan rivers that are a lifeline to hundreds of millions of people in northern India.

Finally there is the crisis facing groundwater. Unregulated extraction of this resource has lead to aquifer overdraft in many regions. This is a catastrophe in the making since groundwater irrigates over two thirds of arable land in India.

Have you done any research or blogging on hydrogeology? Cite examples.

I have not done any formal research on hydrogeology. But I do have colleagues who are hydrogeologists and doing field work with them has given me some idea about the hydrogeology of the Deccan Basalts. So I tend to blog about this topic. For example I wrote a post on the link between groundwater availability and farmer poverty in the central parts of India, a region that has seen a spate of farmer suicides in recent years. Another post deals with the aquifers underlying Rajasthan which is an arid region, and plans to exploit this resource. And I write about local problems like the groundwater usage in urban settings which is being done without a rigorous scientific assessment of the viability of the endeavor.        

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