Temperatures rising - Shauna Murray
Associate Professor Shauna Murray: What I want to talk about tonight, Bill’s just given you a synopsis; those of us who live in Sydney know we’re very, very lucky to live along such a beautiful coastline. What I’m going to talk about tonight is some of the processes that are happening underneath the water here, processes that we’re probably not so aware of because they’re happening at scales that we’re not used to paying attention to. So they’re either very, very tiny things happening at millimetre scales or they’re happening over decade or time scales, so scales that we don’t routinely pay attention to.
If we were to go off the coast of Sydney for example and take a litre of water, what would we find? If we look at that under a microscope we’d probably see something like this, which is in the order of a million cells, single cells of tiny microscopic organisms. This is what I’m basically researching; phytoplankton. Bill basically gave you an introduction to phytoplankton. So they're a group of organisms that are more diverse than plants, animals and fungi all put together. They’re extremely diverse genetically, even though they might all look in some ways similar. Each of these is a separate organism; a lot of them contain chloroplasts, mitochondria and many of them also have flagella and can swim around.
Those of us who understand a little bit about photosynthesis might know the importance of the Amazon rainforest in providing oxygen for us to breathe, but what we might not be so aware of is, for example, the importance of diatoms. This is one group of marine phytoplankton. These cells are about a twentieth of a millimetre in size but they’re so abundant in the ocean and they photosynthesise at such a level that they’re providing about four times as much oxygen to us as the Amazon rainforest.
You’re probably also aware of the term fossil fuels. What you may not know is that the fossils in fossil fuels are actually fossilised diatoms and other types of phytoplankton, so we are also dependent upon them for that - for the fuels that we use.
What we’ve been discovering in the last few years is that they’ve also a lot more going on amongst the different phytoplankton then we were previously aware of. You may be aware of the term plant chemical defenses, so ecological chemical defenses. What this usually means to people is, for example, a plant which is being attacked by a certain predator and so developed some sort of compound or some sort of method so that that predator then won’t eat it.
A classic example might be a chili pepper which produces a compound called capsaicin which is also a capsicum, which deters a fungus from attacking it. This is actually quite common in the plant world and I’m sure Andy can tell us all about it. But it turns out that it’s actually very, very common in the sea as well. It’s been called the watery arms race and what this actually refers to is the production of toxic compounds by certain species of phytoplankton and the production of strange surface features that might deter predators, all of which will act to firstly deter predators but also to inhibit competitors and in some cases even to help phytoplankton species in their own predation on other phytoplankton species.
There are some groups of phytoplankton in particular that seem to produce a lot of these various toxic chemical compounds. One of them is called the dinoflagellates. I’ve got an image here of a dinoflagellate cell and this is similar to the diatoms, about a twentieth the size of a millimetre, very abundant in the world’s oceans. It produces a range of different toxic chemical compounds and I’ll just show you some of them.
These are long-chain carbon backbone compounds so they’re extremely high molecular rate compounds, many of them. This one at the top here, for example, is called palytoxin and palytoxin is actually one of the most toxic substances that we know on a per weight basis. It turns out it’s about 7,000 times more toxic than mercury. Other compounds, for example, this one down here, ciguatoxin that I’m going to talk about a little bit later, and this one down here saxitoxin that I work with a lot because it’s very commonly produced by phytoplankton and is actually a real pain to work with because I have to get a permit from the Department of Defence.
Apart from that, there’s also a range of other compounds that are produced by these organisms. For example, this one down here is called [anthidionide H] and it’s currently being investigated for treatments against cancer.
We’ve probably have only chemically categorised a very small proportion of the actual compounds that are produced by these organisms. Given that phytoplankton likely produces in miniscule quantities, how are they affecting us? The process that’s been happening above the water that we’re probably all very well aware of is the increasing growth worldwide in aquaculture. This has been particularly pronounced over the past 30 to 40 years, so I’ve got a graph here that shows from 1950 to 2010.
So down here is the wild capture fisheries and you might be aware that about at least 30 percent of our wild captive fisheries are currently over-fished around the world. The top part here is aquaculture production. We’re now about here and it’s now reaching about 50 percent. About 50 percent of our seafood’s actually coming from aquaculture these days. You can see that we’re in here for a perfect storm and that’s actually exactly what’s happened.
This is an example of the growing problem of harmful algal blooms affecting aquaculture around the world. This is an example of the species, of a group of species, of genus Alexandrian that I discussed before that’s producing saxitoxins, the toxin that I need the permit from the Department of Defence for. That one is - you can see its distribution in 1970 is given by these blue dots, so you can see in 1970 it was present in a few places in North America, Japan, a couple of places in Europe, South Africa and that was it.
This red is the Pacific Oyster, the countries with an active Pacific Oyster aquaculture industry and here it is in 2014, so it’s basically now everywhere. All down the US coasts, in South America, all around Australia, New Zealand and all over Asia. You can see that it’s becoming more and more in conflict.
There are quite a few different reasons for this increasing occurrence of harmful algal blooms around the world and one of the reasons relates to increasing nutrient run-off from land. Another reason is increasing shipping around the world which is transporting species into new areas and a third reason, which is particularly pertinent to us living on the eastern seaboard of Australia, is changes that’ve happened to the east Australian current region.
For those of you that’s seen the film Finding Nemo you probably know everything there is to know about the east Australian current. For people who haven’t seen it, it’s a very cute kids film that shows of a tropical fish species swimming down the south - the east coast of Australia from tropical Queensland, the Great Barrier Reef and ending up in Sydney. So that’s actually relatively accurate. It gets a lift on the east Australian current and that’s actually exactly what the east Australian current does. It brings this warm water from the Great Barrier Reef region down to Sydney.
What we’ve seen over the past 70 years is that the east Australian current region has been warming at a rate about double the global rate of temperature increase in sea surface temperatures. It’s about 1.4 degrees over the past 70 years, the rate of warming. That’s been due to this warmer water penetrating further down south and it’s also the currents become stronger and it’s become saltier. All those things have had a combined affect.
For those of you who might be following, for example, the climate talks that are happening in the lead up to the talks in Paris later this year, will know that the intent of that agreement is to try to limit climate warming globally to two degrees. So that’s obviously a mean air temperature rise and you can see from this that it’s going to be highly variable around the world, depending on the systems and also different again in the sea, what the actual temperature rise will be. By midcentury it’s predicted that this will already be more than a two degree rise.
So what might that mean in terms of phytoplankton species? This is an example species that might, for example, have a certain temperature threshold at which it grows best. You can see here the different months of the year and if that temperature, in this example for a cold water species, might be 13 degrees, if that is then increased by two degrees, the number of days that it’s then able to bloom, so that means proliferate in large numbers, is essentially doubled so the chances of a bloom happening in certain areas is greatly increased.
Another change that can happen with changes in the east Australian current is actually tropical species moving further down south. This is something that we have in fact seen. There are others in our department at UTS who’ve extensively researched tropical fish species, for example, being found further down our coast. We’ve also found this tropical species gambierdiscus for the first time in southern New South Wales waters.
Some species of gambierdiscus can produce this toxin that I mentioned earlier called ciguatoxin. Now ciguatoxin can accumulate in fish and when it does in sufficient quantities and people eat the fish, it can produce a syndrome called Ciguatera Fish Poisoning. This can be fatal in extreme cases but in generally, it produces an acute, or sometimes a chronic condition and it’s actually fairly common in tropical regions around the world.
For example in New Caledonian over someone’s lifetime, there’s a 70 percent chance that they will get Ciguatera Fish Poisoning and that appears to be increasing in most tropical countries around the world. It’s relevant for us in Australia because it’s been found in Queensland for many, many years and then recently in the last two years, or in the last 18 months to be exact, we’ve seen the first cases occurring in New South Wales from fish caught from New South Wales waters. So there are about 16 cases from fish that were caught in the Evans Head region in northern New South Wales.
Given that harmful algal blooms are on the increase worldwide, what can we do to detect these and what improvements can we develop? One of the answers to this kind of question I think has got something to do with something called citizen science and by that I mean a method which allows, for example, an aquaculture farmer or another person who had a need to study the phytoplankton, to be able to use a device which will tell them, for example, something that they need to know. Are the waters at the moment full of this particular toxic species that, if I waited a week to harvest my oysters, they might be clear. This is the kind of thing I’ve been working on.
To explain how I’m doing it, I’ll just give you a very brief history of how we study phytoplankton. When I started studying phytoplankton about 15 or more years ago, we used to do things like look down electron microscopes. An electron microscope is a type of microscope that uses a beam of electrons rather than a beam of light to give you a nice illuminated picture. All of the pictures that I’ve been showing here have been electron microscope pictures which are why they have such lovely resolution and detail for something that’s only 50 microns in size.
So that was great while it lasted but it was extremely labour intensive and time consuming to study something using that sort of equipment. Also in the meantime, we’ve seen the amazing advances in molecular genetics. Over the last 15 years we’ve sequenced the human genome. We’re suddenly able to do so much more with molecular genetics methods. These are the methods that I’ve been applying to phytoplankton.
It’s not without its difficulties because here’s an example, for example, of the genome size. Here we have a phytoplankton cell, a human cell and if we were then to take the chromosomes from that and sequence strands of DNA, we would find that in the human genome there is approximately three billion base pairs, but in the dinoflagellate genome we’ve got up to 40 times larger genomes, so we’ve got a lot more material to play with.
Based on this, we’ve been identifying market areas that we can use to detect these toxic species and then using that to design tools that we can then apply in a semi-automated way so that an aquaculture farmer might be able to then detect in his own farm whether or not a certain toxic species is found or not.
I hope that I’ve been able to explain this, some of the wonders that are happening beneath the ocean and some of the complexities that has turned out to be a lot more complex than we first realised when we started looking into this about 15 or more years ago. I’ve also described some of the molecular genetic tools that we’re now using to approach these kinds of problems as the harmful algal blooms become more and more common along our coastlines.
Thank you.
12 May 2015
16:32
marine ecology, climate change, microbiology, seafood, fish poisoning, seafood farming, biotoxins
Shauna Murray looks at developing novel genetic tools to monitoring marine biotoxins in the seafood farming industry.
About the speaker
Associate Professor Shauna Murray
Shauna Murray is a marine microbial ecologist. Her research looks at marine toxins that affect seafood and humans with ciguatera or scombroid fish poisoning. Shauna is currently working on developing novel genetic tools for the monitoring of marine biotoxins in the seafood farming industry.
UTS Science in Focus is a free public lecture series showcasing the latest research from prominent UTS scientists and researchers.
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