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Invasive Species

Diving Deeper: Episode 59

underwater image of invasive seagrass

Can you find the invasive species?

Did you know an invasive species can be a plant? In this photo, non-native seagrass species Halophila stipulacea (long, oval blades) is mixed with native Syringodium filiforme (cylindrical, spaghetti-like blades). This non-native seagrass is now found in the shallow waters of 19 Caribbean islands. It is native to the Indian Ocean.


HOST: Today on Diving Deeper, we will explore invasive species. Joining us by phone today is Amy Uhrin, a research ecologist with NOAA's National Centers for Coastal Ocean Science. Hi Amy, thanks for joining us today!

AMY UHRIN: Hi, it's great to be here.

HOST: Amy, let's just start off with the basics here first, what is an invasive species?

AMY UHRIN: That's a really good question Kate. There are some divergent perceptions on exactly what constitutes an invasive species, but most federal organizations follow a definition that goes something like this, it would be any living organism, it can be plant or animal, that is not native to the particular area under consideration, the species has been introduced or is non-native, and the species has a tendency to spread very rapidly, and can cause economic or environmental harm or harm to human beings or animals or other plants. So to be considered invasive, the negative impacts that are caused by the particular non-native species have to outweigh any benefits that that species may be providing in an area.

HOST: Amy, can you give us a few examples of an invasive species that our listeners may be familiar with?

AMY UHRIN: Absolutely. So probably one that most listeners would be most familiar with would be the invasive lionfish. So this is a fish species that is native to the Indo-Pacific region that has now invaded the East Coast of the United States and parts of the Caribbean. Another species that folks might be familiar with, particularly in the northern part of the United States is the zebra mussel, which is common to Europe in the Black and Caspian Seas, and has invaded the Great Lakes areas in the United States.

HOST: And Amy, I'm sure this varies for each instance, but can you share with us some ways that an invasive species might be introduced into an area?

AMY UHRIN: Sure, one of the major pathways for the introduction of invasive species comes through shipping, particularly ships that are crossing oceans. In their homeport, ships take on water, they take on ballast water, and that is to offset the way that the cargo of the ship is distributed throughout the ship, like a weight balancing game. But then when the ship crosses and gets to its destination point, that ballast water is typically just released from the ship into the waterway that it is transited to. So that is one of the major pathways of the introduction of invasive species.

Another way that species could be introduced is accidental or intentional releases from the aquaculture industry. So many aquaculture species, particularly many shellfish species are actually not native. So for example, here in the U.S., there are a lot of aquaculture facilities for Pacific oysters, so those oysters somehow spawn and the spawn escapes from a contained area, those species could be introduced accidentally.

Another common way people might hear about is the aquarium trade or people have particular fish species in their aquarium that they don't want anymore or are becoming a nuisance in the aquarium and they just release them into a local waterway.

Species can get here also by hitchhiking on marine debris. Particularly for some marine plants, just floating fragments can invade another area. And an interesting mechanism, and this is a mechanism how an invasive seagrass got to the West Coast of the United States and that was it was used in packing oysters from Asia that were sent over to the West Coast for aquaculture there and the seagrass seedlings and fragments in that packing material actually got released when the oysters were unpacked and that seagrass was able to invade parts of the West Coast of the United States.

HOST: OK, I'm probably most familiar with the ballast water that ships are taking on like you just explained to us there, but I wasn't aware of so many of these other different instances. What kinds of impacts does an invasive species have on the existing plants and animals that are already there and already living in that area, living in that habitat?

AMY UHRIN: Right, so many different impacts. But I think that first it's important to point out why some of these invasive species are so successful at invading. So, often times these species are taking advantage of some kind of disruption or some kind of disturbance that has happened in a local ecosystem. So on land there might have been a fire, if you think of coastal environments, there might have been a hurricane or coastal development, and somehow that ecosystem becomes disrupted and oftentimes it's easier for invasive species to survive or take advantage of those types of disturbances than it is for the native species. And there are several characteristics of that invasive species that lead to it being able to take advantage of disturbances. They typically can reproduce very rapidly, they grow very fast, they have high dispersal capabilities which means that they can just move pretty easily from one place to another so they are very mobile, they are often generalists and what that means is they can use a wide variety of different resources in an area. So people tend to think of generalists in terms of diet, so typically they can eat a variety of other different species, they don't have a specific diet that they can take advantage of that.

Oftentimes these species can alter their growth form or alter the way they look to suit their new conditions and they are also often able to tolerate a wide range of environmental conditions and because they're introduced in an area, often they don't have natural predators in that area. So that's kind of a long-winded explanation, but some characteristics of why these types of species do very well when they invade an area.

So when you want to talk about then, what are the impacts of the invasion. To go back to the lionfish, because folks are probably familiar with that, they tend to crowd out native species and to exclude native species from the same types of prey items. So lionfish, and I can speak directly from the lionfish that have invaded here in North Carolina, but they tend to consume the same types of prey fish as grouper and snapper, which are very important here commercially and recreationally, so that’s a big problem if lionfish are consuming the majority of the prey items available to other native species.

I mentioned zebra mussels before in the Great Lakes. Interesting about zebra mussels, if you think of oyster reefs along the coast here in North Carolina, zebra mussels can also form reefs on the bottom of rivers and lakes, and this can actually result in changes in water flow and altered habitat structure for native species. So that's an interesting way that folks might not think about.

There's also an invasive green algae, if you're a marine botantist, everybody knows about Caulerpa taxifolia, or the killer green algae that invaded the Mediterranean Sea, and what's interesting about that particular algae is that, where its native, it actually occurs in small patches and clumps, but when it invades an area, it tends to overgrow everything and it forms really large meadows and it was actually beginning to choke out the native seagrass species in the Mediterranean. And that particular algae was also toxic to some herbivores in the area, and those herbivores obviously are at the low end of the food chain, they're serving as prey items to fish higher up in the food chain, and if those herbivores can't exist where that green algae in the area, then that creates a problem for like I said fish higher up in the food chain. So there are a lot of things to consider about the impacts of a species and as I mentioned at the beginning, whether or not they are really detrimental.

HOST: Are there economic impacts that we can see from invasive species, so for these communities that just are living and working around these areas are they economically impacted by invasives?

AMY UHRIN: Oh absolutely. And I can't actually give you any dollar figures, but I can explain generally what can happen in some of these areas. I talked at length about this killer green algae in the Mediterranean Sea, so fishermen were beginning to complain that as they were dragging their nets to catch fish, the nets were getting clogged with this algae getting caught on the algae and so if your gear breaks or you lose it obviously you have to spend money to replace your gear and that can come at a significant cost to the individual fisherman.

So we talked about the zebra mussel in the Great Lakes. With the zebra mussel, fouling was a big issue. Mussels started growing on water intake pipes and things of that nature that are associated with power plants and water purification facilities, they would start to grow on the hulls or the bottom of ships and foul the ships that way and the ships had to be cleaned so that costs money.

We talked about the green crab preying on native shellfish, so that reduces the native shellfish population and that reduces the catch in those particular fisheries so that can have an economic cost. And then we mentioned the lionfish, how they tend to eat the same types of fish species as the other fish eat and those other fish are commercially and recreationally important, so that's reducing the number of prey that those species can utilize.

And we talked a little bit about seagrass. One thing we didn't mention is that there is the possibility that a non-native seagrass species could come in and fauna could utilize that particular seagrass differently than the natives, so if the non-native seagrass comes in and maybe it supports fewer juvenile fish species, well that's a problem because seagrasses tend to be areas where juveniles hang out before they migrate off to a rocky ledge or a coral reef, so if for some reason the juvenile fish aren't utilizing this non-native seagrass species, that could be a problem later on in their life stages.

HOST: Amy, is it possible to remove an invasive species once it's been introduced?

AMY UHRIN: That is a really good question. For marine habitats, once a non-native species comes in and establishes, it can be extremely costly and extraordinarily difficult to control or eliminate them, if not nearly impossible. And really, early detection and rapid response is key and controlling these invasives really I think needs to focus on intersecting them before they become established and removing the pathways of how they are getting to a location. So for example, we mentioned shipping as a major global pathway for invasive species and there are ongoing efforts on how to improve the management of ballast water in these trans-Atlantic shipping pathways.

Another thing that we mentioned was species escaping from the aquaculture industry. I know currently folks are working on improving federal oversight and having stricter control measures on the industry to try to limit the accidental escape of those species.

HOST: What is NOAA's role in respect to invasive species?

AMY UHRIN: So NOAA actually is engaged in a couple of intergovernmental organizations that are tasked with dealing with invasive species and one is the Aquatic Nuisance Species Task Force and NOAA is also involved with National Invasive Species Council. Part of our involvement would include sharing results of research that was specifically directed toward invasive species, part of that involvement would also include perhaps helping to better define or clarify what an invasive species is, and also developing guidelines for early detection and rapid response protocols.

Folks may have also heard of a program called Mussel Watch, this is a national program that NOAA is involved that actually can involve citizen science, but what happens is samples are taken from the sediment and tissue samples can be taken from shellfish, bivalves, and mollusks, and those samples are analyzed for contaminants. And the focus initially for this program was in the Great Lakes, so by default, people were collecting the zebra mussels that we talked about, so it did give us some good data on the distribution and abundance of that type of invasive species because folks were already out there collecting samples for this Mussel Watch program. And the program has been extended, it's on both coasts of the United States now, it's not limited to the Great Lakes anymore.

And then in terms of invasive species research, I can't speak for all of NOAA, but in my particular office, I'm in Beaufort, North Carolina, at the Center for Coastal Fisheries and Habitat Research, and staff in my office were really instrumental in tracking the initial spread of the lionfish invasion when it began on the East Coast of the United States. And researchers here at my lab continue to investigate many aspects of the biology and ecology of the species as well as develop tools for early detection and response.

HOST: Do you have any final, closing words to leave our listeners with today?

AMY UHRIN: Sure, so in this podcast we have primarily focused on marine invasive species and some large-scale processes or drivers that lead to invasions and how these species get here, but it's also important to point out as this is Invasive Species Week, there are obviously numerous invasive species on land and in freshwater systems, so no matter where you live, as an individual, you can take action against invasive species, first by learning what invasive species are in your area and perhaps get involved in projects that aim to try to eliminate or eradicate the species from an area. A lot of time, national parks, state parks, county parks will look for volunteers to participate in an eradication project and oftentimes, for obvious reasons, this will focus around plant species because they're not particularly mobile and can easily be pulled out from the roots and discarded and as I mentioned early detection and rapid response is really important for invasives, so it would give us a chance to maybe be involved in controlling an invasive species perhaps in an area, the first instance of the species has been found, and it might give them an opportunity to participate in the early stages of an invasion and actually help to control the species.

Additionally, a lot of people are avid boaters, it's really important if you take your boat to many different waterways and waterbodies, perhaps if you like to fish and you're going from lake to lake, it's really important to clean, drain, and dry your boat after each use particularly when you're going to go from different bodies of water. Perhaps one that would be really important for people, are folks who like to maintain aquarium, we talked about the aquaria trade earlier, but it's really important if you decide, I don't like this particular fish in my aquarium or he's making a mess or he's bullying the other fish in the tank, it’s really important to contact the retailor or the person you bought the fish from because oftentimes those companies or those people will offer a buy-back program. It's really important just to not release that fish or any animal into the wild. You can possibly trade your fish with someone, you can possibly donate the fish or animal to an aquarium or a zoo, there are many alternatives.

And a couple other things, people who are avid hikers, campers, or just like to be outdoors and again are traveling outside their region, perhaps to another state or another country, it's really important to clean dirt from your shoes after you're finished hiking and you're going to go back home. Another thing campers might not think about is, especially if you're trying to save money, and bring your firewood with you to go camping, what's important to think about if you're traveling any big distance out of your home region is you actually use or utilize firewood in the area that you’re going to be camping in.

And of course, if you're going to garden or landscape around your home using native plants is key. And then just taking the things that we've talked about today and what you’ve learned today in this podcast and then encouraging others about invasive species.

Host: Thanks Amy for joining us today on Diving Deeper to explore invasive species and really provide us with a lot of great tips and things we can all do ourselves in our everyday lives as we look to hopefully help combat this problem of invasive species.

That's all for today's show. For more information, check out our show notes on oceanservice.noaa.gov/podcasts.html. And remember, you can follow the National Ocean Service on social media. We're at noaaocean on Twitter and Pinterest or check out usoceangov on Facebook, Flickr, and YouTube. Be sure to tune in next month!

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