Ocean aliens - the problem of species in the wrong place
Why is it sometimes such a big deal when species end up in the wrong places? On Naked Oceans this month we explore marine invasions and find out how people shift species around the oceans, what problems this causes, and what can be done to stop them. We visit the Caribbean to get the lowdown on a notorious ocean alien, the lionfish, and find out how the best policy could be "Eat 'em to beat 'em". Janet Voight tells us about her recent report that warns deepsea explorers to be very careful not to pick up any unwanted hitchhikers. And in Critter of the Month we ask Miriam Goldstein to tell us if she were a marine species, which would she be and why.
In this episode
01:16 - Alien invasions in the ocean realm
Alien invasions in the ocean realm
with Boze Hancock and Mark Spalding, The Nature Conservancy
Helen - We often hear about invasive freshwater species wreaking ecological havoc in places they shouldn't be - things like Chinese mitten crabs and signal crayfish here in the UK, and zebra mussels all around the world. And invasive species are also causing problems in the marine realm. Later on we'll hear the story of lionfish causing problems in the Caribbean and how science could actually be contributing to species movement, but first, when we're talking about 'invasive' species, how do we define what they actually are?
Boze - An invasive species can go by a number of different definitions. A fairly broad definition would be any species that's living and persisting outside native range. For it to be invasive some people would impose on that definition another layer that it causes a problems, usually an economic problems. But at the most basic level it's a species that's been moved and is able to persist outside its native range.
Helen - That was Boze Hancock from the Nature Conservancy.
One of the key questions asked when it comes to invasive is about the scale of the problem. How many invasive species are there in the world and where are they localised? Back in 2008, Mark Spalding, also from the Nature Conservancy, was involved in the first quantitative study of marine invasive species around the globe ...
Mark - What we wanted to do was try to tease apart the challenges from marine invasions. Now, some species are moved - there are always species moving into new environments - some of those are far more threatening, far more problematic than others. So what we were trying to do was both to look at that geographic spread, where were these things happening, were there hotspots on invasion. And also trying to tease out how many of those invasions are actually posing problems either for people or for nature more widely.
And we showed that they were found in pretty much every kind of biogeographic region in the world. They're everywhere. And where we had gaps, chances are that no-one has data rather than they're not there. But there were huge hotspots, the Mediterranean being one, the Californian coast being another, Southern Australia. A lot of those hotspots are around ports or areas of dense, technologically advanced human populations.
Helen - And how are these species moving around?
Mark - You can have natural invasions. You can get species moving into a place naturally through some unusual weather event and so or. But invasions generally are humans bringing species into places. So we're introducing species all the time. The numbers are phenomenal. One estimate which is probably reasonable is that at any point in time at the moment there's 10,000 different species being carried around in boats. A boat will pick up ballast water in one port and carry it to another, and then lets that water out with a host of species, most of which won't invade, they'll die, the conditions are too cold, too hot, too fresh, too salty, and so the won't survive. But every now and then some will.
Helen - As well as shipping, aquaculture or fish farming can also be a major way for species to move about the globe...
Boze - There's a lot of movement of either the species that is being aquacultured itself, fish or shellfish, around the globe and also food. Some of the problems that have occurred have been with say fish pens and moving bait fish from one area to another to actually feed those farmed fish. Or alternatively in the NW of the US is a particularly high level of invasive species and a good many of those came from the days when there were large volumes of small Pacific oysters shipped in from China predominantly, and they were brought to the NW and grown out there for sale. So with boxes of oyster shells there are numerous hitchhikers that come along with them and a good percentage of those have actually stayed and found a new home. And cause a number of problems as a result.
Helen - Certainly aquaculture and shipping ballast water are two of the main routes of invasive transmission, but as we'll hear later, aquarium trade can also play a role, and a new study shows that scientific research could be helping to move species around too. Climate change may also have a role to play...
Mark - I think in the changing world, particularly with climate change, there's going to be natural movements that are going to look like invasions. It's already happening. We're watching the spread of species up coasts, as coasts get warmer, the warm water species are moving along and into new areas. So we're seeing that as a form of natural - semi natural - invasion.
It's not a nice neat movement that every species shifts its range at the same time at the same rate, so you're going to get species appearing that will then predate other species that they've never met before so you will get imbalances and changes and they will look like invasions in a more scary sense, they will be causing changes to ecosystems.
Helen - Yet another example of humans providing a route for species to move to new areas is the building of the Suez Canal. Built in the 1860s, this forms a link between the Eastern Mediterranean and the Red Sea, allowing goods to be transported from Europe to Asia without circumnavigating Africa. But, it also acted as a passage between two bodies of water that had been separated for tens of millions of years, allowing species to migrate between them. Especially from the Red Sea into the Med, where around 1000 species have been recorded. So what is the ecological reason for the success of this invasion? Mark Spalding again...
Mark - If you look at what's in an ocean evolution works its magic and species appear so on the eastern Mediterranean as always been a little bit depauperate, it's been lacking the number of species you'd expect in a body of water that warm in that location. And the reason for that if you look at it is the origins of those species, they've all had to come through colder water to get to the eastern Mediterranean. It's actually a kind of subtropical basin, the eastern Med, but the only route in for the last tens of millions of years has been through the straights of Gibraltar where waters are much colder.
And what happened when the Suez canal opened up and species started to come in a lot of fish, but a lot of other stuff too, and doing very well Interestingly they don't seem to have replaced or pushed out anything. So you've got suddenly a much more diverse array of species but nothing so far as been documented as disappearing.
Helen - So in this case, the invasions don't seem to have threatened the local ecosystem. But there are many more examples of species that have become a menace. Macro algae have been smothering reefs in Hawaii, and comb jellies caused a crash in the anchovy fishery in the Black Sea in the 1980s after being introduced there. And it's not just animals and plants that can be invasive, but diseases as well, that hitch a ride with transported species.
But is it all doom and gloom? Can anything be done to remove invasives? An eradication program to control the algae taking over Hawaiian reefs has had some success because of its whole ecosystem approach. Invasives are generally not just a threat on their own, but when taken together with other threats like pollution, nutrient runoff and overfishing of species that might eat the invasive, they present a problem.
In Hawaii, measures are being taken to improve the health of the ecosystem to help the fight against the algae - increasing the numbers of local herbivorous sea urchins, working with local government to reduce nutrient runoff, and physical removal of the algae using what are essentially giant ocean vacuum cleaners.
The idea of introducing additional species to control an invasive problem is one that has been used on land, but often with disastrous consequences. Could we see this kind of intervention in the sea? Boze Hancock...
Boze - We are newer at the impressive art of manipulating the marine environment. It's been done on land for a long time but we are still working to understand the ecosystems and the interactions in the ocean. So I don't think we are anywhere near as advanced and I would not advocate or encourage anybody to do that. The incidents of introductions going wrong outweigh the incidents of introductions doing what was intended by such an enormous amount that I think you'd be crazy to try.
Helen - So the key is really to prevent rather than treat. Equipment for testing ballast water, and cleaning it, is being developed, but it's really the increased awareness of the problem that is working in our favour, particularly when it comes to aquaculture...
Boze - It doesn't mean accidental introductions are not still possible. Wherever animals are moved around in our oceans there is a potential for invasive species but people are just far more aware of it now and aquaculture operations actually rely on a clean environment, that's what their business relies on, so the understanding of the impact of what has happened I think is one of the things we've got working in our favour at the moment.
Find out more:
The Nature Conservancy
Invasive species in the oceans
10:55 - Deepsea exploration spread species around
Deepsea exploration spread species around
A study published this month in Conservation Biology found that deep sea exploration vehicles like Alvin could be transporting species between different dive sites.
Janet Voight from the Field Museum of Natural History in Chicago had been leading an expedition to see if deep sea vent species would move to new habitats if they were available. And on one dive to the experimental habitat they'd created, they sampled 38 individuals of a species of deep sea limpet. The team were thrilled, until the morphology, isotope and genetic analysis came back showing that the limpets were identical to those from a population found at a vent system over 600km away from their experimental site that the team had visited 36 hours earlier. After getting in touch with Amanda Bates, who had been working on this species of limpet, Janet realised that the limpets they'd sampled were not in their experimental site naturally.
Janet - We concluded and I had my head in my hands at this point because my wonderful hypothesis was in the trash, I was ready to throw the whole thing in the garbage. Because it was contamination. I emailed Amanda just distraught and she wrote back and said Janet this is just so much more important because what we have here is a demonstrated means by which Alvin could transport species that might be invasive to an area where they do not normally occur and could be harbouring diseases and parasites.
As a deep sea biologist I had been to international vent biology work shops where people had cautioned us, we really don't want to introduce any species into new areas. And I had sat there in the audience and nodded by head thinking "well yeah, that'd be really awful, you shouldn't do that". And yet here I had led a cruise, as chief scientist I was responsible, that almost did that.
Helen - So how had they got there?
Janet - Somehow, those animals, there were 38 of them, had managed to hide inside the suction sampler for at least 36 hours while the ship transmitted those 640-50km north to our next dive site. I believed at one time that the exposure to the temperature shock, the exposure to the pressure differences from the seafloor to the surface were just, I mean if it different kill them outright the animals would be moribund unless they got comfort - they got cold water, and really were taken care of.
So our message to our colleagues who do deep sea research whether its biology or geology in many of its different guises, is to please be careful and to clean thing, to wash Alvin the sampler gear where animals may be hiding underwater with freshwater to make sure they can't infect a new site.
Find out more:
Voight et al (2012).
Scientific Gear as a Vector for Non-Native Species at Deep-Sea Hydrothermal Vents. Conservation Biology. (OPEN ACCESS)
14:20 - Tackling the problem of lionfish
Tackling the problem of lionfish
with Chris Flook, Ocean Support Foundation
Helen - Lionfish are beautiful but venomous fish that are native to reefs in the Indian and Pacific Oceans. They're also popular aquarium pets and it's thought that releases, either accidentally or perhaps on purpose, led to their introduction on the other side of the world.
Chris - One of the first reports of lionfish in the Atlantic dates back to the late 70s early 80s, and it was an anecdotal observation, somebody had seen one of these off the coast of Florida and nobody believed it.
Helen - That's Chris Flook from the Ocean Support Foundation in Bermuda.
Chris - Then in 1992 there was a confirmed accidental release after Huricane Andrew in the Biscagne Bay area or about 5-6 lionfish. People went there and took pictures and said, Oh that's beautiful, lionfish in the Atlantic, oh they're not really going to do much damage. Nobody knew or even predicted all that they would do as much damage as they have.
Helen - There are nine species of lionfish, and there are two that have become established in the Caribbean- Pterois volitans and Pterois miles.
Chris - What's really interesting is that everything north of Florida is both species, the volitans and miles. Everything south of the Bahamas seems to be mostly volitans which makes the researchers believe that basically there were potentially two points of the invasion, one off Florida because of the two species and one south of Florida which is just the volitans. To this point I believe everyone south of the Bahamas, from Curacao down to Colombia, Mexico and all that are all volitans.
Helen - Lionfish have also reached much further north, to Bermuda way out in the Sargasso sea, 1000km off the United States eastern seaboard. It was Chris Flook who reported spotting one in the water in Bermuda, ten years ago. Back then he was the head collector for the Bermuda aquarium and he noticed something was wrong at one of his top collecting spots ...
Chris - So the one year I went and all of a sudden I was very aware there were a lot less fish than usual. It raised some concerns to me and as I turned the corner, sure enough there was a lionfish. So I caught the lionfish brought it in and we starting figuring where this thing came from because Bermuda's so far out in the middle of nowhere it's not that we imported the fish, it's obviously come from somewhere else.
Helen - The major problem with lionfish getting established in the Caribbean is that they have really big appetites, and as soon as they set up home on a new reef they very quickly start munching their way through the native fish species.
Chris - Where they're from in the Pacific they've been programmed over millions of years to eat as much as they can whenever they can. Because the fish there see them as a threat, they've got to work really hard to eat, because they might not eat tomorrow. The fish in the Atlantic don't see them as a threat.
We did some early experiments when we first started seeing them here. I took a little lionfish and put him in one tank and I took a little black grouper from off the coast here in another tank. And I took some juvenile baitfish out of an enclosed bay that had never seen a grouper and put them in the tank with the grouper and they knew they had to stay away from that grouper because they knew that at some point that grouper would eat them. And then we put the small fish into the tanks with the lionfish and they actually swam up to the lionfish to try and hide next to him. And he ate every single one.
When you look head on at a lionfish it looks very similar to the soft corals that we have in tne Atlantic, so the fish haven't picked it up as a threat yet. They know groupers, they know sharks, they know bigger threats are threats. But just the way a lionfish looks, looking more like something they would want to hide in.
Every single lionfish that I've necropsied from Bermuda, Florida, through the Caribbean, every single one has fatty liver disease. Now, fatty liver disease is a classic captive problem and the fact that you're overfeeding them and the fish isn't working hard enough to get its food. So to see every single lionfish from the wild and cut open have fatty liver disease is very telling and the fact that they're just gorging.
Helen - Studies are showing just how much of an impact lionfish can have on Caribbean reef fish. In the Bahamas, a 5-week experiment showed that lionfish can reduced native juvenile fish by 79%. And one large lionfish has been observed eating 20 young fish in half an hour.
And one of the keys to the successful invasion of the Atlantic by lionfish is their immense reproductive captivity.
Chris - the females will dump 30,000 eggs every spawning cycle. Those eggs after about 30-40 days settle out as baby fish on the reef. And by about 6-7 months old they're old enough to spawn. The quick turnaround on the fish in terms of the spawning cycles have just made the population really boom.
Helen - And it's those eggs that Chris thinks invaded Bermuda from further south in the Caribbean:
Chris - The egg mass that the females dumps, not individual eggs or individual larval fish, what it is, it's a big gooey gelatinous ball that floats around or a couple of days before these fish hatch out. So with that gooey ball floating to the surface and floating around for a few days before they hatch, the ones that are spawning here close to shore, the potential is that the larval fish can't make it to shore but a few of them I'm sure are getting pushed out into the deep and further north in the cold and don't actually make it to adulthood. But there's not much doubt in my mind that all the breeding fish that are down in the Caribbean just because there are so many of them, for sure some of those eggs masses are making it to us.
Helen - And with the lionfish in the Atlantic eating so much, they're growing bigger and producing even more fish than they do in the Pacific.
Chris - In their native range they get to 13 inches or so. We've had them as big as 18 in the Atlantic.
Helen - After researching these fish and learning more about their ability to munch their way through native fish populations, Chris and his colleagues convinced the Bermuda government to try and tackle the problem of lionfish in Bermudian waters.
They came up with a plan to catch as many lionfish as possible - and the task force they've enlisted is made up local scuba divers.
Chris - They're fairly easy to catch. They really are bold and brave. They know that they have venom and nothing's going to eat them. There's two ways that we target them diving here. In most places I've been they do they same thing. They have some sort of small spear, that allows the diver to get up to the fish and whack him without getting too close. My personal favourite is using little collecting nets, little hand nets. With the fishermen, some guys are catching them on hook and lines, what I tell guys is when you get them in the boat just put it on ice and leave it til its dead, once it's dead just cut the top fins off, cut the bottom fins off and treat it like any other fish.
Helen - They are also working on novel ways of selectively trapping lionfish, while leaving other fish alone. One approach is to put some bait fish in a glass jar inside the trap to attract the predatory lionfish, and the other idea takes advantage of the fact that lionfish are social animals:
Chris - We're also using high resolution pictures of lionfish so that the lionfish will see them, see there's a group of them in there and want to go hang out. None of the other fish want to come and take a look at a picture of a lionfish but lionfish do for some reason. So, we're still in the early stages and working out the kinks in it but there is quite a bit of promise so far with it.
Helen - And the good news is that in areas where there's not too great a risk of ciguatera poisoning - a disease that people can catch by eating predatory fish in some tropical countries - then lionfish are really good to eat, even though they have venomous spines.
Chris - It's a true protein-based venom, it's not a toxin or a poison. And in heating the venom will denature so its inert. That's why if people are stung we say the first thing we do is put your hand or wherever you've been stung in as warm water without burning yourself. But for cooking, you can take a whole fish, as is, throw it in a frying pan, cook it all the way through, there's absolutely nothing on the fish you can't eat.
So the campaign Chris launched was called "Eat 'em to beat 'em"
Chris - I've always look at the lionfish issue as we need to make lemonade from lemons. We have this issue with lionfish in the Atlantic now, humans have caused it, there's no doubt there. But you know the seafood watch cards where you've got a green choice, a yellow choice and a red choice? The green choice is the best option, the yellow choice we should avoid and red choice we should definitely avoid. Those are all managed fisheries. With lionfish if we could start a commercial fishery for them, it's a greener than green choice. Because we're not removing healthy genetics from a managed fishery because we want to remove all of them. By targeting them as a food fish a) they're not out there eating, b) they're not out there spawning, they're not competing against the other native fish, but then also we're not pressuring the grouper and snapper species that aren't doing as well as we think they are. So there is some hope there if we can make a commercial fishery out of them.
Helen - Lionfish eradication programmes are being rolled out across their new range - if you're a diver, watch out for lionfish catching derbies if you ever visit the Caribbean.
And time will tell how well lionfish fisheries will take off to help control the invasion and minimise the impact on native species, but as Chris points out, lionfish are probably in the Caribbean for good.
Chris - for me it's never been an eradication issue it's always been a management issue because to think that we're going to remove every single one of these lionfish is a complete pipe dream.
Find out more:
Ocean Support Foundation
REEF Lionfish Programme
23:38 - Critter of the month - Bubble snail
Critter of the month - Bubble snail
with Miriam Goldstein, Scripps Institution of Oceanography
Miriam - My name is Miriam Goldstein. I'm a graduate student at Scripps Institution of Oceanography at the University of California at San Diego. For my research I work in the middle of the North Pacific, in the area called the North Pacific sub tropical gyre and I work on the surface of the ocean. And on the surface of the ocean lives what Sir Alistair Hardy called the Blue Fleet. There are all these animals that have made a living right at the very surface where the UV light is very strong so they're all blue and purple. And they're really wonderful creatures.
And of all those wonderful creatures one of my favourites is the bubble snail Janthina. And this is a little snail that has a lavender shell and it actually makes its living upside down on the surface on the water floating around on a raft of bubbles.
So it just drift along, it makes its own little raft, sort of just going with the wind with these other animals that live in this fleet feeding on the tentacles of jellyfish. That's what it does - it just drifts along. I always thought that sounded like a really nice life just rafting a long, just a little bit under the ocean, nibbling and having a good time for a snail.
Find out more: