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Polar Plankton: indicators of environmental change

Updated Thursday 6th October 2011

The Saving Species team talks to Chris Reid and Graham Hosie about studying microscopic polar plankton - the source of all food in the oceans

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Chris Reid
Chris Reid, from the Sir Alister Hardy Foundation for Ocean Science, and the University of Plymouth.

Interviewer
Most people will have heard of plankton, but, you know, very briefly, what is plankton?  What’s the definition and what does it contain?

Chris Reid
Plankton are free floating organisms in the sea, made up of both plants and animals.  They vary very much in size.  The vast majority of them are microscopic, so you have to look at them under a microscope, but they can grow to a very large size like some of the very big jellyfish.

Interviewer
But I guess the key thing is that they're drifting, aren’t they?

Chris Reid
They're freely drifting, the majority of them.  Some of them can swim but not a great deal, but the majority are freely drifting with the ocean currents.

Interviewer
And again, when we look out at the sea, it tends to look like a pretty uniform place, so are plankton spread pretty evenly across the globe?

Chris Reid
No, they are extremely variable in their distribution, to a large extent depending on what we call the stratification of the water column, this is the layering of the water, so the upper layer of the ocean is warmer than the deeper, colder layer.  But also they're very strongly affected by tides in the shelf regions of the world, which are the shallow areas going down to about 200 metres, below which there’s a drop to a very deep ocean.

Interviewer
And across the surface of the globe, are we finding different if you like communities of plankton in different temperature regimes, different latitudes and so on?

Chris Reid
Yeah, there’s a great difference in the communities that you see between the Polar seas and the Tropics, and also in the size of the plankton.  So in the Tropics you will tend to get much smaller species, whereas they tend to grow bigger in the Polar Regions.

Interviewer
So knowing there is this diversity of plankton then, it becomes, I won't say relatively easy, but it helps to understand if any changes are taking place.

Chris Reid
They are great indicators of environmental change, but also they're hugely important for the carbon cycle in that the phytoplankton and in turn the zooplankton take out carbon dioxide from the atmosphere, and a proportion of that is transferred to the deep ocean, in what we call the biological pump, and that’s crucial to the carbon cycle.  But they're also the source of all food in the oceans.

Interviewer
And for us selfishly for ourselves as well.

Chris Reid
And for eating, for humans, I mean when I say the source of all food, but also for other living, what we call the living marine resources of the world, the fish and the aquaculture of the oceans.

Interviewer
So it’s absolutely imperative that we understand plankton, if changes are taking place, we need to know what those changes are.

Chris Reid
Well, one, we know that changes are taking place, and this is shown particularly from the symposium which we’re at, at the moment.  This survey has demonstrated very pronounced changes which seem to be associated with climate change and global warming.

Interviewer
I know you’ve been working globally, but let’s stay pretty close to home, and you have been concentrating some of your research in the North Sea, what’s been happening there?

Chris Reid
In the North Sea we've seen very sharp changes around about the mid-1980s, ’88, when the phytoplankton, the plants in the North Sea, have changed from a spring and an autumn bloom to appearing throughout the whole of the year, and a virtual step change and an increase in, a very marked increase in chlorophyll which has more than doubled.

Interviewer
So I mean you talk about chlorophyll, of course plankton isn’t just the chlorophyll, the plants, it’s the animals as well, the zooplankton, and then whatever eats that is going to be affected.  What are the kind of knock-on effects, are we seeing them or what can we expect?

Chris Reid
We are already seeing them, and this is demonstrated particularly from one of the most important small animals in the plankton, a copepod, Calinus finmarchicus, that has moved out of the North Sea because the North Sea has warmed by over a degree, and as a result this is impacting the fisheries.  Cod are declining and we’re seeing a northerly movement of warmer water plankton at the same time, and colder water species are moving to the north, and the same is happening to the fish.

Interviewer
So the whole complexion is changing?

Chris Reid
The whole ecosystem around the British Isles and in North West Europe is changing.

Interviewer
Taking that geography a little bit further, going up into Polar waters, are they being affected?

Chris Reid
Yes, we’re already starting to see a movement of warmer water species into Polar regions.  The ice is retreating and plankton are starting to grow in areas where they weren’t found before, and we’re seeing lots of warmer water species or species from furthest to the south are now penetrating into the Arctic Ocean, and this seems to go in pulses and is increasing every decade.

Interviewer
But it seems like that’s an exchange.  I mean is it a fair exchange, should we be worried about it?

Chris Reid
I think we should be worried about it in that it will impact the fisheries in a very great way so that the fisheries in the North Sea will become more like the fisheries in the Mediterranean in decades’ time.  But perhaps more importantly we should be worried about the potential feedbacks that there may be to climate from the plankton, if this, what we call the biological pump slows down in the world’s ocean then a lot more carbon will be released to the atmosphere and the greenhouse effect will be accelerated, and so the level of warming of the world will increase even greater than it is at the moment.

Interviewer
So climate change is causing these changes in the first place, and then that’s having a feedback and just exacerbating the whole thing.

Chris Reid
At this moment in time, we know the feedbacks take place, but we don’t know which way they're going, so it could be a positive or it could be a negative feedback.  But we really need to understand that and at the moment we’re only sampling a very small part of the world’s ocean so we don’t know what is happening throughout the greater part of ocean.  In the South Pacific for example there’s virtually nothing known about how the plankton is changing.

Interviewer
Now this isn’t just a south to north, as far as we’re concerned in the northern hemisphere, a south to north movement of species following presumably the water temperatures.  We hear in the news increasingly about the way that the ice cap is receding and the fact that we’re now starting to get sea connections between the North Atlantic and the North Pacific, two oceans that have been held apart for many, many, many, many thousands of years.

Chris Reid
Well we’re seeing again with data from the continuous plankton recorder a transfer of an organism from the North Pacific, which is really abundant in the North Pacific, it’s a diatom called Neodenticula.  We found it in the North West Atlantic in 1999 for the first time in over 800,000 years.  We know it was present in the Atlantic before because we found it in deep, well not us personally but it has been found in deep sea cores, and it looks as if it has come through because of the melting of the ice to the north of Alaska and Canada, which two years prior to that opened up for the first time.  And we now know that there’s also a grey whale has been found in the North Atlantic in the Mediterranean, which also likely came through because of the melting of the ice, and we know that there is a parasite of seabirds which has also been found in the North East Atlantic which was never found before, and it looks as if it has come through because one of the vectors is a euphausiid, another small planktonic organism.

Interviewer
So sticking with those plankton moving in from the Pacific into the Atlantic, again if it’s, if some of those have been here before in the past, does it really matter?

Chris Reid
It matters hugely, potentially, because the last time there was a major incursion of species from the Pacific was in the Pliocene which is over two million, probably about four million years ago, and when that happened many of the species which we now see in the, particularly in the North West Atlantic, and these are primarily organisms that live on the bottom, these are now the species that are present in the North Atlantic.  And they will have exterminated some of the other species which would have been native to the Atlantic at that time.  We will see a huge change potentially in the biodiversity of the North Atlantic.

Interviewer
So what are your thoughts for the future as a result of these changes in the plankton south to north and west to east?

Chris Reid
Well I think we need to understand more what is happening, but perhaps they are giving us a warning of the speed of change that is taking place in our world and that our politicians should take note and that we need to take action on greenhouse gasses, carbon dioxide so that we stabilise the world’s climate system.

9’15”

* * * * * * *

Graham Hosie
Well here I'm representing the Southern Ocean CPR survey, which is organised through SCAR and my name’s Graham Hosie, I'm the Director of the Ocean CPR survey.

Interviewer
And when it comes to the Antarctic waters, they appear to be facing a multiple threat.

Graham Hosie
I think it’s pretty true of all oceans.  We’re only just starting to get into ourselves, we’ve realised that global warming was an issue and we've noticed sea ice reduction over years.  Some threats, we've not been so familiar with.  Ocean solidification wasn’t on the radar when I started work in the Antarctic, and there’s other issues which are slowly coming to the fore, but we need to consider all of them because my personal belief is that a lot of these are acting synergistically, working together.  And it’s not a question of just a slight increase in temperature or a major increase, a lot of these things could be working together in concert with even the small drops of UV or increases in UV that could actually be working together that it’s like bit by bit, it’s sort of one plus one plus one makes ten, and has a much greater effect.

Interviewer
And it’s particularly worrying for us in the colder waters of the planet, they're much more productive.

Graham Hosie
Parts of the Southern Ocean are extremely productive.  We’re noticing some cases a lot of increase in phytoplankton.  Using satellite imagery we can see it happening.  Certainly about 40% of the productivity of the region produces the oxygen that’s why phytoplankton comes from the Southern Ocean, and that’s sort of very interesting for us.  But at the same time, that’s also a major, or seen as a major sink for all CO2 at the same time, and also supports a massive amount of life in the region.  Most people are familiar with the iconic species like penguins, seals and whales, but there is a massive amount of krill in that region as well, perhaps 200 and as much as 500 million tonnes.

Interviewer
I guess most people have heard of krill and do realise its importance, particularly when it comes to whales, so how are krill being affected?  What is this link with krill and the plankton, how does that work?

Graham Hosie
Well krill are much dependent on the phytoplankton and what they're doing, and they can eat other zooplankton at times, but they're a sea-ice creature primarily.  They like to live in cold water and our concern is that with the reduction of sea ice that you're going to see less habitat for the krill and less ice algae production for krill.  And as the sea ice retreats towards the Antarctic continent, there is actually realises a point where there’s nowhere else for krill to go because they'll run out of habitat.

Interviewer
Is there a timescale for this, have you got any idea?  Is that happening already?

Graham Hosie
We’re seeing quite a reduction in sea ice from about the 1960s to 1970s.  There was a stepwise reduction that seems to be holding steady, although the SCAR report on the state of the environment that was published recently, I think just last year, was showing that overall we expect about a 30% reduction in sea ice over time.  We've already seen substantial loss of ice around the Antarctic Peninsula with the loss of the Larsen Ice Shelves.  The western side has warmed by about five degrees.  The Ross Sea is actually showing some increase in sea ice, but in turn overall we expect to see a reduction. 

Interviewer
And this obviously, as you say, impacting the krill itself - can a creature like krill, can it adapt to these changes?

Graham Hosie
Well surprisingly enough they may well do.  It’s very easy to take an organism, well take myself, if you drop me into the middle of Singapore in high summer with 90% humidity, I'm not going to feel too well, but give me time and I will adapt.  And I think we shouldn’t ignore the possibility that some species have immense resilience and can adapt.  Only time will tell, but you’ve got to be careful when you do laboratory experiments you're not just throwing things into conditions they don’t like immediately; give them time, they may well adapt.

Interviewer
But one of the key things of course is the food supply of the krill, the phytoplankton, the plant plankton, and we keep hearing that the makeup of that plankton is changing, so that’s going to affect the krill?

Graham Hosie
It may well do.  It may add some competition.  If we’re seeing, what we think we’re seeing is some of the smaller species becoming a little bit more dominant, that will put pressure on, and copepods are a small species, they're only about two or three millimetres, they're sort of like the sheep of the sea if you like, and krill the cows of the sea, and they can eat a lot more of the phytoplankton.  But we also are going to be very careful when we’re doing this analysis that we don’t dismiss the fact that what we’re seeing could be a completely natural cycle, and this is the things we've got to tease out.  If there’s anything detrimental, we've got to make sure that it is actually a genuine effect and not a cyclic pattern.

Interviewer
So plenty more work to do.

Chris Reid
Plenty more work to do, and so considering in the context of the CPR surveys, which we’re sort of celebrating eighty years, Sir Alister Hardy did his first test tows in, across Drake Passage in 1925/26, and it’s a pity he didn’t continue that because the information that he could have gathered over what would be nearly hundred years would have been absolutely perfect to answer some of the questions that we need to address.

Interviewer
But you’ve picked it up and you're continuing the good work.

Chris Reid
Well, hopefully, we've celebrated our twenty years and we hope someone will be around to celebrate the twenty years from now in another twenty years.

Interviewer
And we should be concerned about this, we should be worried, I mean, you know, it isn’t just about wildlife, that’s massively important; it isn’t just about whales; it’s about human beings as well.

Chris Reid
It is, yes.  I mean we’re part of the system.  We have interests in the sum notion that’s growing, more and more people seem to be enamoured with it, and they see the films like Happy Feet and they take interest, and they are slowly understanding the importance of phytoplankton, and as we talk to more children about the importance of phytoplankton and zooplankton, they're starting to understand that this is a watery planet and the major component of that water and the life is plankton.

14’57” 

zooplankton Creative commons image Icon idua_japan under CC-BY-NC-ND under Creative-Commons license Polar plankton
 

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