DR HELGA DO ROSARIO GOMES is a Research Scientist at Lamont-Doherty Earth Observatory, Columbia Climate School. Her research interests are on impact of climate change on marine ecosystems and ocean biogeochemistry. Hailing from Goa, she graduated with a PhD in Biological Oceanography from Bombay University and after research positions in Japan and in Maine, joined Columbia University in New York. Though based in the United States, Dr Gomes has conducted research on the Arabian Sea. She spoke to ALEXANDRE MONIZ BARBOSA on her perspectives on climate change, changes in the Arabian Sea and the possible effects on Goa.
Excerpts from the interview:
You've been in Goa for some weeks now, do you think that this heat wave with yellow warnings was unusual for March? Is it early warnings of climate change?
I think we are seeing unstable systems everywhere in the world. It will not be persistently heat, but very unstable systems. It’s already been predicted that we would have less rain, but then we will have incidences of very strong rainfall. We will not have persistent rainfall like how we used to have, we will have massive dry spells and then events of extreme rainfall and you've seen that already, last year I think, or the year before. What it will be is such instability already being experienced everywhere in the world.
Talking about instability, the Arabian Sea was very stable with cyclones rarely arising in it. Yet, in the last decade we have seen more cyclones on the west coast of India.
Two or three years ago, my husband Joaquim Goes went on a cruise with the University of Massachusetts and I think the US Navy was involved. Their aim was to predict the cyclones, because the waters have changed, the atmosphere has changed, the heat, where even one to two degrees makes a big difference, so that the existing model for prediction of cyclones may not hold now. There is this whirlpool of water that accumulates off Kerala, and they think that the intensity and the spread of the whirlpool may be able to help predict the monsoons, so they went to that whirlpool. That is the year the cyclone struck and they were in the eye of that cyclone but the cyclone pulled all the heat from the whirlpool. So they were not able to really tell what happened.
In our childhood, we heard of the cyclones in the Bay of Bengal, not in the Arabian Sea.
Exactly. Earlier when we went to sea, everybody wanted to avoid the Bay of Bengal and here, in the Arabian Sea, it was like going for a picnic because it was so calm. That’s one of our studies that we are doing about the changing biodiversity with climate change.
You have done much research on the Arabian Sea and made some interesting discoveries. What are those?
I did my PhD at NIO and a lot of my thesis work was in the Arabian Sea. At that time it was very steady. When we went to the United States, we decided to revisit our earlier studies and so we talked to some of our old colleagues from NIO and they told us they were seeing interesting things happening. We shared data and one of the things we noticed was that the biodiversity, the biology of the Arabian Sea, especially the base of the protein, which is the plant-like structures of the Arabian Sea had changed completely.
Anything specific that was noticed?
Generally, the base of the food chain, the plants of the ocean, are called phytoplankton. They photosynthesize, take carbon dioxide, take nutrients and make food and then everything else eats them. The phytoplankton are the base of the food chain of the oceans. When we started looking at the data, we saw that there were very unusual organisms. When we asked our colleagues about them about them, they said they were seeing them very much. We know them as noctiluca and it’s called noctiluca scintillans. We started researching this noctiluca and we saw that there were giant massive blooms generally found only during the winter monsoon. When the Himalayas cool, they also cool the water adjacent to the mountains. So, cold water sinks, the warm water comes up and that deeper water is full of nutrients. That is the way phytoplankton get food and nutrients. The phytoplankton need nitrate and phosphate and all these nutrients to grow. And that is the mechanism, especially in the Arabian Sea, when water is churned and water is moved, and deeper waters come to the top, everything gets fertilized. That’s why in the monsoon season, when winds come and pick up, they remove the top layers of the ocean, other richer or nutrient-richer water comes to the surface. In the same way, this was happening. But generally, we saw very classic phytoplankton during the winter monsoon.
This was not the condition earlier?
It was not. We saw this very classic change of phytoplankton called diatoms and some other phytoplankton, generally diatoms, which are very popular, well-known, when there are a lot of nutrients. But we never saw this noctiluca in millions.
What do you conclude by this?
Noctiluca are called mixotrophs. In this case, noctiluca is like a big sack that has tiny little green organisms that are photosynthesizing and giving it food. At the same time, when there are not many nutrients, these noctiluca are able to eat things. So, they have now become also plant-like. So, there are tiny little, they don't even need to eat live material. They can also eat dead material, detritus, eggs, anything that they find. So, that gives them a massive advantage. Now, what is happening is the waters are getting warmer. When the waters are getting warmer at the surface, there is this thing called stratification, which means that the bottom layers are not able to come to the top and fertilize. So, in this case, with the stratification there are no nutrients. So, on one side, they are taking whatever nutrients there are in the water, they are taking away a lot of the nutrients, and at the same time, they are feeding on little, little things. Those little, little things were food for other little, little things. So, they have taken away another food source, they have taken away another nitrogen source. They have a tremendous advantage in this. And we are seeing this not only in India, we are also seeing it off the coast of Oman.
What is the impact of the noctiluca?
They impact the food chain because nobody eats them as they store a lot of ammonia in their cells. Since they have a lot of ammonia, fish and other creatures are not going to bite. Now you have this big mass at the bottom of the food chain, taking away food from little, little organisms, taking nutrients from other phytoplankton, and now nobody likes to eat it except scalps and jellyfish. Who is eating jellyfish and salps? Only turtles and all. So, you are seeing a growth of jellyfish in many areas, especially here. You also have these mega cities around the Arabian Sea and nobody has sewage treatment plants. I have read that our Goa sewage plants are working at like 20 to 40 percent of their capacity. So, imagine the amount of organic matter that we are dumping into the oceans. Bacteria are very happy to eat that. And when they eat that, they take oxygen because bacteria respire like us. The oxygen minimum role of this particular one that I was talking about, is expanding. It's a great environment for noctiluca, for scalps and jellyfish. So, everything is working like in their favour. Based on whatever studies we had, we know that the biodiversity of the Arabian Sea has changed drastically.
On a different note, there was this NASA study that predicted a lot of coastal areas, including some in Goa, going underwater by 2.7 feet.
That is very concerning because that is based on the fact that warm water expands and so it rises. We don’t study rising sea level, but our studies are related to that because we know that if there is a rising sea level, there could be other noxious groups that can come about. We haven't done much work with rising sea level, but I'm working with Dr Peter Ronnie D'Souza on this project about the Mhadei River and what will be the repercussions for, like, the dams. I think one thing that will happen is that when the sea level rises, saline water will enter the rivers. Right now, our rivers have got such amazing biodiversity, especially at the mouth. We can study how fisheries will be impacted if the mouth of the river biodiversity changes. Right now if saline waters from rising sea level, and we are seeing that already, enter the mouth of the river, these delicate organisms shift. A sudden massive influx of saline water will not only impact the plankton, but impact other organisms that are on the banks, like, these tisreo, khube, all our fisheries. There’s already the worry that the dams will reduce the water, so there will be this shortage of water and also saline water will enter.
The mangroves that are growing around the riverine islands of Mandovi River, could it be due to the incursion of saline water?
Yes, because they (mangroves) can tolerate much salinity. Therivers are also no longer flowing the way they used to. There’s a lot of river networks, rivulets that keep the water flow nicely and keep the ecosystem in balance. But now the ecosystem is already out of balance, both in the Arabian Sea, and in these riverine systems, especially at the mouth of the estuary. What is happening at the top and what is happening here, is going to impact the estuary. And that is where our fish is.
How does one contain the salt water ingress into the rivers?
Make sure that the network of water is flowing, there are some breaches, some blocks, some bundhs cemented, cement is not the right material, so we have to go back and check what are the things that work. I think we are smart enough to figure out that maybe this river, this rivulet has to be cleaned, or this water has to exit the system. I think that’s the only solution, how can you otherwise stop so much salt water from entering? For saltwater to enter an estuary is, I think, nearly the death of the estuary as it is, then it just becomes an oceanic system and as salt intrusion goes up, the organisms are not able to withstand that as they are purely fresh water.
Have you worked with the local fishermen, on how the changes are affecting them?
No, not so much, but we have developed a tool for fishermen and for many stakeholders in Oman, where we have a decision support system. That decision support system, takes data from NASA, like chlorophyll, hydroplankton data, temperature and winds, and we have a modeler, who develops a model, plugs the data into the system and then based on that gives an early warning, including on whether there will be salt water intrusion.
Could something similar be developed for Goa?
Yes, because we already have the tools, we just need to fine tune it for Goa and the model actually runs very well for the Arabian Sea. It was started by the Navy for the Arabian Sea, so we don’t have to even fine tune, we just have to get it going.
Coming to the soil erosion along the coast, have you done any studies on that?
No, because we are not geologists, but you can see that soil erosion impacts all the biodiversity – the fauna and the flora, the things growing there, and also the fact that they, supply nutrients, and are protection of land.
Given that Goa is a very narrow land and has such a long coast, would it be more susceptible to any rise in sea water?
Of course. We all live along the coast and the coast is where the most economically-advantaged lands are. All our fishing industries and other industries, our tourism is dependent on the coast, even those casinos are dependent on the water, although I don't know how good they are for our system, because I don’t even know where they dump their garbage and sewage.
What should be Goa’s strategy on climate change?
You should concentrate on having long term studies, understand why these blooms are happening. We know why they are happening, but often Indian scientists try to contradict us but there hasn’t really been a concerted study on why these new organisms are appearing. There is no long term study on the impact of rising sea level on this. When I was doing some research for the Mhadei, there was nothing, absolutely nothing, it is so hard to get information. I think we should have a network of universities, maybe of colleges, masters students in science researching on how and why is salt water intruding into our systems. They can use remote sensing. There is free satellite data, all provided by NASA, free software. That could help us to determine which side should we divert our water so that we have a good flow of water. We don't have that kind of study. Why not give projects like this? The Goa government and Goa University should take this up.