Coral bleaching

Coral Bleaching

Facilitator: Dr Ross Hill is a marine scientist in the School of Environmental Sciences at UTS. He's looking into the impacts of climate change on photosynthetic marine organisms. So your work comes under the umbrella of marine climate change. That seems like a very big issue to be tackling. Can you break it down for me as to what your research involves?

Ross: The main focus of the research I'm doing at UTS is coming under the umbrella of climate change and marine systems but there are two big problems which we're looking at. The first being global warming. Now that's happening because of there's more CO2 in the atmosphere. Through the greenhouse effect we're getting a warm atmosphere and as result the oceans are also warming.

The second big problem, thanks to CO2 again, is it's dissolving into oceans and the result that has is more acidic oceans. So all the CO2 that's in the atmosphere coming from human activities such as burning of fossil fuels, driving cars, agricultural activities, we're seeing an increase in the atmosphere.

So from the pre-industrial levels of about 280 parts per million of CO2 in the atmosphere, we're now up to almost 400 parts per million. That's higher than a level that's been seen in about the last 650,000 years and the rate it's increasing is also about 100 times faster in about the last 650,000 years.

Facilitator: Why is that dangerous for a reef?

Ross: As temperatures continue to increase, we see more frequent and more intense and often more widespread bleaching events. Now this bleaching is to do with the loss of the symbiotic algae which live within the animal tissue.

The corals rely upon the symbiotic algae for their nutrition so in open oceans especially where we find large areas of coral reefs, there are very little nutrients. So these algae which live inside the animal tissue are able to harvest sunlight through photosynthesis and give nutrients back to the animal; therefore this close symbiotic relationship enabling the coral to survive in an otherwise nutrient desert.

Facilitator: So why is this a worry for coral reefs?

Ross: So this is a problem because what we're beginning to see is these bleaching events occurring more frequently. Without these algae inside of the animal tissue of the coral, the coral can't survive. We often see large mass mortalities of coral following a bleaching event.

Facilitator: So how does your research then fit into this?

Ross: So we know that warmer temperatures in the oceans cause coral bleaching events. What we want to understand is what is the actual photosynthetic trigger within the algae that causes them to be expelled from the animal tissue.

The work we do up on Heron Island and in the lab at UTS looks at individual coral species to understand - is there a difference between different coral species and the type of symbiont that lives within them that controls their susceptibility to future climate change, warming oceans - that sort of thing.

Facilitator: How would you go about researching that?

Ross: We use a whole range of different types of equipment. Usually up on the reef, we can work in the field or we can work back in the lab. The type of field instruments we can use are portable chlorophyll fluorometers. These instruments measure the photosynthetic capacity of anything photosynthetic.

So we can use these instruments in the field; take them under water with us and determine the health of the coral through quite simple measurements. Back in the lab, we can look at the oxygen production and the consumption of carbon dioxide in the process of photosynthesis to try and understand which side of impact within the whole chain of photosynthesis is actually being affected.

Facilitator: It sounds to me a little bit like it's just an excuse to go scuba diving.

Ross: Well it definitely has its perks. We actually do a lot of the work just by going out onto the reef flat and collecting samples. So at low tide you can just walk out and there are large expanses of reef which are exposed and you can easily get your samples.

Or you can go out snorkelling at high tide. These corals are cultured in coral tanks here at UTS and we grow up these corals to be used for a whole bunch of different experiments within the lab here.

Facilitator: So in all of this research, what's new that we haven't known before?

Ross: What we're beginning to see and realise is that the whole coral organism which previously has just been assumed to be the animal tissue and the algae, it also contains a really important third component. These are the bacteria and microorganisms which live within and one the coral. Now these microorganisms are very important for maintaining the health of the coral by providing nutrition and also protection from other bacteria and invasive microorganisms.

We're beginning to look at how corals with or without certain types of bacteria are more or less susceptible to climate change. So we're beginning to understand that the types of organisms that live on and within corals that we can't see with our own eyes - beginning to understand that they are really important and play a major role in maintaining the health and fitness of corals on the reef.

Facilitator: What do you have to say to climate change sceptics?

Ross: I get a lot of people saying to me that they don't necessarily believe climate change is happening. It comes as quite a shock to me because I've worked on climate change and I've seen the impacts that it can have. In my mind, there's no question. Climate change is happening and it's because of human activity.
Most of the people who say that they don't believe in climate change really don't understand the changes in the carbon dioxide concentrations that we're seeing in the atmosphere. The huge increases that we've seen in such a short time frame, we can't expect those to not have consequences on our atmosphere; on our climate.

We're seeing these changes in warming oceans and warming atmospheres; more acidic oceans. These are having direct effects and they are because of human activities.

Facilitator: You seem very passionate about this. Why is that?

Ross: I've been up to Heron Island many times and it's an incredible place. Like many places on the Great Barrier Reef, the diversity on the reef is incredible. They've been compared to the rainforests and the sea but they actually contain many more and more diverse organisms than any other place on earth. So they really are worth conserving and protecting. With global warming and also ocean acidification, we're seeing the destruction and loss of many of these ecosystems which are really fragile but play an important role, not only ecologically, but also socially and for the economy.

About half a billion people around the world rely on coral reefs for their livelihood and, from the perspective of tourism and fisheries, they need healthy coral reefs for their income.