Plastic Podcast Episode 25: Neuston: Life on an Ocean Garbage Patch

 Discover the fascinating world of neuston—tiny organisms living on the ocean's surface—and how they interact with plastic pollution in the South Indian Ocean subtropical gyre. In this episode of the Plastic Podcast, host Clark Marchese is joined by marine ecologist Dr. Mark Gibbons from the University of the Western Cape. Together, they delve into the unique dynamics of neuston communities, their role in the marine ecosystem, and the implications of plastic pollution on these delicate life forms. Learn why understanding these interactions is vital for future ocean cleanup efforts and the preservation of marine biodiversity.

Episode Guests:  Dr. Mark Gibbons

Find more information about Dr. Gibbons here. 

Find a link to Dr. Gibbon’s article here.

Find more of Dr. Gibbon’s research on Google Scholar

Find images of all the cool neuston we talked about today here. 

More information about the episode and the Plastic Podcast

Episode Transcript and more information on the Pine Forest Media Website.

Follow Pine Forest Media on Instagram @pineforestmedia

Hosted, produced, and edited by Clark Marchese 

Cover art and PFM logo by Laurel Wong. 

Theme music by Tadeo Cabellos

Transcript:

[00:00:09.680] - Clark Marchese

Hello, and welcome back to another episode of Plastic Podcast, the show that tells the science and the story of our relationship with plastic. I am your host, Clark Marchese, and today we are talking about jellyfish, neuston, plankton, ocean currents, and the South Indian Ocean plastic gyre. All right. Welcome back to all of you lovely listeners, and hello to all the newcomers. Now, two weeks ago, we had an episode where we spoke to two researchers from Germany about hotspots of micro and microplastics in the ocean. If you didn't listen to that one, it's okay to start with this one and then go back if you're curious for more. But in that episode, we talked about where plastics in the ocean get concentrated. We touched a little bit about the five major ocean plastic gyres. Today, we're talking about the little ocean critters that live on and around these gyres and what we know about how they interact. The word for these ocean critters is neuston, and we're going to get a more a normal definition of that in just a moment. But essentially, it's an umbrella term for a group of organisms that live on or just below the surface of the ocean, and obviously, they are increasingly encountering plastic.

[00:01:27.620] - Clark Marchese

We know that obviously, plastic in the ocean environment is harmful to lots of wildlife. You also might remember the episode we had with Dr. Christine Figgener a couple of months back, who was the person who took that viral video, pulling a straw out of a turtle's nose about 10 years ago. But at the same time, we also have some examples of organisms using plastic to their benefit, as Dr. Yvonne Shashoua explained to us in episode seven. I've also been seeing more and more articles that talk about these plastic gyres mentioning Houston. So the point of this episode is to figure out what's going on there, or at least to figure out as much as we do know. Thankfully, a Dr. Mark Gibbons was kind enough to come on the podcast and answer all of my questions about Houston. Dr. Gibbons is a professor in the Department of Biodiversity and Conservation Biology at the University of the Western Cape in Cape Town, South Africa. He also completed a pretty adventurous ocean research project that aimed to gain a better understanding of which types of neuston are living in and around the Southern Indian Ocean subtropical gyre, which is one of the least understood of all the plaster gyres.

[00:02:28.260] - Clark Marchese

Without further ado, let's talk to Mark Gibbons and learn everything there is to know about neuston and plastic. All right, we are recording. Hello, Dr. Mark Gibbons. Welcome to the show. The first question I have is if you could just introduce yourself and tell us a bit about your research.

[00:02:59.890] - Dr. Mark Gibbons

My name is Mark Gibbons. I am a lecturer at the University of the Western Cape here in South Africa, one of four universities in and around the Cape Town area, though. I am a marine ecologist with a special interest in plankton, the animals and algae that float freely in the water column in the open ocean, with a special interest within that in jellyfish, and Most of my research at the moment is focused on jellyfish. But I've also, in recent years, have been given an opportunity to work with neuston, which is what we're going to talk about in just a moment.

[00:03:44.890] - Clark Marchese

Wonderful. It is great to have you here. Now, as I've been looking more and more into how plastic is operating in the ocean, I'm seeing recent publications about Neuston. I guess the best place for us to start is by me asking you, what is a Neuston?

[00:03:59.560] - Dr. Mark Gibbons

So Neuston is a community of organisms that live at the air-sea interface. So it's sitting at the very surface of the open bodies of water. So we get Neuston in fresh water as well as in the ocean itself. It's those organisms that live either on the top of the sea surface, things like blue bottles, which have a big gas bladder. We call them blue bottles here, elsewhere they may be called Portuguese manipul. It's a siphonophore with long trading tentacles, but it's effectively, it's a balloon of gas that sits on the sea surface. There are a couple of other organisms that are tied to the sea surface in that way. Then there are organisms that sit below the sea surface but are nevertheless associated very closely with the sea surface. This includes things like porpita, which is, I can't remember it's more common name.

[00:05:01.570] - Clark Marchese

Okay, I could be wrong, but I googled it after the interview, and I believe that would be the scientific name for what some of us might know as blue buttons. I hadn't heard of these little guys before, but they are quite beautiful, and they look almost like they could be a piece of jewelry.

[00:05:14.990] - Dr. Mark Gibbons

Then there are things like Janfina, which is a very fine, oval gastropod, which produces a series of bubbles, which then allows it to sit right underneath the sea surface.

[00:05:32.130] - Clark Marchese

Yes. Lots of species names are getting mentioned, and I will put a link in the episode description to our website where you'll be able to find photos of everything we talked about today.

[00:05:41.060] - Dr. Mark Gibbons

These are organisms which we refer to as obligate use, They are completely tied to the surface, the surface of the sea. But then we get what we refer to as facultative neustons, which sit just below those and may come in and may move out of the layers of the water column. Some of these are copapods, which are small crustations, and they are generally bright blue in color. In fact, most of the neustons is bright blue in color. Whether that's a response to camouflage or whether that's a response to ultraviolet light, I'm not sure. So these organisms are very tightly, closely linked to that upper layer of the sea. A number of things, commercially important fish species, their eggs and larvae may float for periods of time within this layer as well.

[00:06:39.990] - Clark Marchese

Can you tell me a little bit about the role or the function of Neustin in the ecosystem?

[00:06:45.590] - Dr. Mark Gibbons

An important player in an ecosystem is one through which large quantities of materials or energy flow and which play a very important role in either influencing the numbers of predators above them or influencing the number of prey items below them. I think it's fairly clear that Houston are not big players in the global ocean context if we look at things like that. But as a system, as a component of a system, they play an important role within that system so that there will be things that will eat them, and in turn, they will be eating other things. That said, a lot of the predators in the neustons themselves eat other members of the neustons. On the surface of the water, you've got Vallella, which is by the Wind sailor, which is both a carnivore, and it's got a symbiotic zoo Xantheli, so it's also able to photosynthesize, if you like. It in turn is preyed upon by what we refer to either as a sea dragon or as a sea swallow, Nudibranche, which is a species of Nudibranche, carnivorous Nudibranch, which hangs just underneath the surface of the sea, and it in turn feeds on things like Balela.

[00:08:10.860] - Dr. Mark Gibbons

It will feed on Janthana, the bubble shell, and it will feed on poppita. A lot of the interactions within the obligate Houston, they're eating each other. But as I said, they are in turn eaten by other things, and they in turn will eat other things themselves.

[00:08:30.390] - Clark Marchese

Okay, so lots of food chains are playing out in this quite broad group of species. And since they're also hanging out at the surface of the water, we know one thing that they are probably interacting with more and more plastic. Maybe there might be a problem for a jellyfish if it encounters a plastic water bottle or a grocery bag floating around. But we know that these plastic items in the ocean aren't so isolated. As we discussed in a previous episode about how plastic has been accumulating in these five massive gyres and also many smaller ones around the world, we might start to ask ourselves questions like, what can we do about them? Can we clean them up? How do we respond? And I've been seeing more and more publications saying, hang on a minute, we are finding that there are significant neustonic communities living on and around these patches, maybe we should figure out a little bit more about their relationship first. So can you tell me a little bit about how this neustonic life is interacting with these garbage patches?

[00:09:29.700] - Dr. Mark Gibbons

The amount of work that is being conducted on Houston, you're right, is increasing, but it's increasing at a very slow rate by comparison with the work that is being done on plastics. So yes, these organisms are being found together in the same areas at the same time. But the research that's being done is focusing on the plastics to try and quantify and understand the of material that are out there. Counting Houston and identifying Houston is not easy. It's very time-consuming. I guess that's part of the reason why the amount of work on Houston lags behind that of plastics and micro plastics at that same level of the environment. Our understanding of the interactions between these things is at this stage unclear. There are papers that have been published recently which suggests that some species of obligate neuston may be concentrated in the same places as the plastic is being concentrated in the center of gyras. But then there are other papers that are saying, no, these things are not being found in largest numbers in the same area. I think it's very early days to say exactly. It will come, providing people to prepare to put the time and effort into examining the organisms that are found there.

[00:11:02.510] - Dr. Mark Gibbons

In terms of the interactions between these organisms and plastics, again, it's early days. There are some species of organisms which will use this additional substrate, the plastic, on which to lay eggs. For example, there is only one group of truly marine insects. In freshwater environments, we would refer to them as pond skaters or water skimmers. These are bugs that live on the surface of the water. They stand on the water using the surface tension of the water to support themselves, and they detect disturbances to that surface tension, which allows them to hone in on prey items. These exclusively marine insects, under normal circumstances, would be laying their eggs on floating seaweeds and pieces of wood and natural flocks and jets in the water column. Or at the surface of the water. But now with the advent of all the plastics, they've now got an additional substrate on which to deposit their eggs. In terms of ingestion, most of these species are carnivorous. Cocopods, which are herbivorous or omnivirus, may well be eating microplastics. So if fish come along and they start eating large numbers of cocopots that have themselves been eating microplastics, then there is a possibility that there is an accumulation of plastics at high atrophic levels.

[00:12:32.960] - Dr. Mark Gibbons

That evidence is there, but what the long term effects of those plastics on the life or the physiology or the behavior of those organisms is, it's early days. It's early days, unfortunately.

[00:12:47.680] - Clark Marchese

Yeah, I think, unfortunately, that also applies to us humans as well. We know we're consuming large amounts of plastic, but not necessarily how it's going to impact our health in the long term. It stands to reason that we wouldn't exactly know how it would impact fish either. But in any case, we did learn in an episode two weeks back that microplastic hotspots exist in these same areas where large amounts of visible plastic end up. So these organisms that also find themselves in these spaces will have lots of exposure. And then you also mentioned the insects being able to lay their eggs on the plastic. Is that something that we might be able to understand as something that's helpful to them to have more places to lay their eggs? Or is there any evidence showing that there is a benefit or a detriment that comes with that?

[00:13:30.410] - Dr. Mark Gibbons

There's no evidence, but intuitively, one would imagine that with a greater amount of substrate available for them to lay their eggs on, all other things being equal, then their populations should benefit from that.

[00:13:44.600] - Clark Marchese

Okay. Then I also heard you mention a slight bit of contestation in the literature, but there have been some articles that did identify higher concentrations of Neuston in these same places with high concentrations of plastic. For those papers that came to those results, what might possibly explain that?

[00:14:04.190] - Dr. Mark Gibbons

What you have to realize is that all of these organisms that occupy the the Neuston, they're generally small organisms. They're what we would refer to as plankton. Which means that they don't have the ability to move against prevailing circulation. So the same physical processes, winds and currents that are focusing the plastics into ocean gyras and certain areas of the sea will also be passively accumulating the nuisance in the same area. So intuitively, one would expect that areas that have large amounts of floating macroplastics, certainly those macroplastics that are projecting above the sea surface, will catch the winds. They'll be concentrated by the currents in particular areas. And so, two, intuitively, you would expect those Houston members that have also projected above the surface of the sea to be similarly concentrated. That seems to be the case, as I said, in some of the papers, but in some of the other papers, that doesn't seem to be the case. That probably reflects local peculiarities in the ocean-air interactions, leading to patches where animals are being concentrated in a different way to the plastic.

[00:15:23.800] - Clark Marchese

Okay, so then it might be the case that in some plastic areas, we see high concentrations of new Sonic life. When that is the case, it has more to do with oceanographic systems or processes rather than these species searching out this type of plastic environment on which they may or may not thrive.

[00:15:42.010] - Dr. Mark Gibbons

A number of the studies, the most recent studies, have also used particle tracking software to try and understand the movement of plastics and at the same time understand the movement of nuisance, because it's effectively the same driving factors that are influencing the distribution.

[00:16:00.510] - Clark Marchese

As we know, it is early days as far as the literature is concerned. But to get a sense of what is already out there in terms of research, I know that you worked on a study that was trying to look at Houston assemblages in the Southern Indian Ocean tropical gyre. Can you tell me about what research questions were attached to this project? What were you trying to find out? Just tell us, I guess, a little bit about this project.

[00:16:22.810] - Dr. Mark Gibbons

The project, I was taking advantage of samples that were being collected to monitor microplastics. I have been working for the last 20 odd years, I guess, with the EAF Nanssen program, which is an ecosystem approach to fisheries program funded by the Norwegian government with support and managed by the FAO, Food and Agriculture Organization of the United Nations. One of the things that we're trying to do with that program is to develop capacity in countries around Africa and in Southeast Asia, the border in the Indian Ocean. We had a survey that was crossing from Jakarta in Indonesia through to Mauritius in the Southwest Indian Ocean. It was looking at the environment and it was looking at resources. We were also collecting samples using Mantenets for microplastics. Then I asked them, Well, if they're collecting the Mantenet samples and they're counting the plastics in them, rather than throwing the animals over, let's keep the animals and let's look at them. This was an attempt to try and understand the communities that were present and how those communities changed as you moved across the Southern Indian Ocean, as I said, from Jakarta to Mauritius, because the transect crossed through a portion of the Southern Indian Ocean Jira.

[00:17:58.990] - Dr. Mark Gibbons

I was keen I wanted to see whether the central parts of the gyro, which are characteristically oligotrophic, there's not much chlorophyll there, which means food chains are going to be much longer because the food part, the particles are going to be smaller. I was curious to see whether the communities in the center of the gyro were going to be different from those at the edges. Then I wanted to see, obviously, as you're moving from east to west, there is a big input into that region from water flowing out of the Banda and some the seas into that area, warm, relatively fresh water, and how that would influence the communities that we see. The focus was very much on trying to understand what was present and what was influencing the communities that we're seeing rather than the interactions with the plastics.

[00:18:53.710] - Clark Marchese

Okay, so then I guess the obvious question is, after you collected the data, did any trends emerge?

[00:18:59.440] - Dr. Mark Gibbons

The biggest take homes for us were that the communities in the center of the gyra are different from those at the edges. The communities at the edges have a large number of what we refer to as mirror plankton. Mirror plankton are planktonic animals that don't spend their whole lives in the plankton. A bivalve spends its life on the seabed. Its eggs and sperm are shed into the water. The fertilized eggs develop into larvae. Those larvae join the plankton for a short period of time before they are the size, they settle down and metamorphose into bivalves. The same is true for benthic crabs and shrimp and a whole bunch of other animals that as adults either live on the seabed or they're necotonic like fish. But there is a portion of their lifespan that is spent in the plankton. What we were able to see is that those communities at the sides of the ocean basin had significantly greater numbers of mirror plankton than those in the middle. Not surprising, perhaps, given the proximity to land and to shallow waters where benthos is more likely to release their offspring into the plankton. But that was nice to see, and the diversity was much greater on the Eastern side than it was on the Western side, which reflects it's the proximity of that area to the Coral Triangle, which is an area of extremely high diversity situated in the area between Indonesia, Philippines, and Malaysia.

[00:20:44.090] - Dr. Mark Gibbons

That was great to see. It was an interesting study simply because it allowed us to get some detailed information on the taxa that were present. The other thing that we noticed is that the greatest abundances of these things were actually being found towards the west, which reflects the role that the wind plays in that area. The Jari in the Southern Indian Ocean is one of the least well understood, and it seems to be structured in a slightly different way to those in the other major ocean places.

[00:21:23.490] - Clark Marchese

What I'm hearing is that the variants and the trends that you identified in the data is attributable to factors outside of the plastic itself.

[00:21:33.100] - Dr. Mark Gibbons

Yeah, absolutely.

[00:21:34.610] - Clark Marchese

Then we still don't exactly understand what happens at their convergence as far as Neuston are concerned. My next question would be then, How do you think we should go about trying to learn more about this topic? What research questions do you still have that would be helpful for us to understand this relationship?

[00:21:54.850] - Dr. Mark Gibbons

Insofar as Neuston and plastics go, I think we still need to understand in greater detail and with a greater temporal understanding, because all the work that's been done on Houston and plastic to date has been once-off surveys. What would be very useful, it would be to have a greater understanding of changes through time because the plastics are not constant in concentrations. They're being added to and they're being lost as they drop out into the seabed all the time. That's the one thing. The other thing that would be useful would be to better understand the interactions between Houston and plastics, both from a predator-prey perspective, but also as a habitat. Because one of the other concerns that plastics are having from a marine point of view is that plastics that are dropped off Cape Town may get colonized by South African animals, and then they get swept off into the middle of the ocean. If the animals don't die, then they can persist and potentially spread from one piece of plastic to the next piece of plastic. Then you're dealing potentially with a source of aliens for other areas should the winds change and the plastics get dispersed and they get moved on to a different area.

[00:23:17.060] - Dr. Mark Gibbons

We need to understand a little bit more about that.

[00:23:23.950] - Clark Marchese

Got it. Okay. When we're mentioning perhaps species from Cape Town attaching themselves to plastics and getting dragged to new environments, I know that sometimes in the ocean, plastics can be encased in a biofilm or carry some bacteria. Was that what you were referring to, or could there be other examples as well?

[00:23:40.440] - Dr. Mark Gibbons

I was referring to larger organisms, things like Bryozoans and things like that.

[00:23:45.140] - Clark Marchese

Wait, what are Bryozoans?

[00:23:46.830] - Dr. Mark Gibbons

Bryozoans are what we refer to as moss animals. They are encrusting… They look like moss, hence the name. They settle onto substrates like that. They will potentially proliferate. But It will also be Nidarians and Polychids and organisms like that which will settle onto the plastics, potentially. Then as those plastics drift off, so these things will move to different parts of the world. From an evolutionary perspective, that's how we understand the diversity of sun taxa on some of the islands. They rafted there originally, and then once they got there, they were isolated, and then they diversified diversified quite extensively. It's not a new phenomenon. It would just be with today's burden of plastics, this increased opportunity for colonization. It's something that we should perhaps be concerned about. I mean, in the case of the North Atlantic, we've got these massive washups of sargasm in Florida and the East Coast of Southern USA. That sargasm has come from Africa and elsewhere in the world, and it's causing huge problems. But that could equally be plastic.

[00:25:06.870] - Clark Marchese

I think we have lots of examples throughout, I guess, the history of evolution on this planet where one species getting introduced to another. Well, it could be really great for both. It could be really horrible for both. It could be great for one and horrible for the other, or there could be no impact on either. I guess it just will depend on case by case. But that said, there's also lots of different cases that will be going at one time because the ocean is enormous, which also speaks, I guess, to the importance of more longitudinal studies to understand how these things are changing over time. But I'm curious about any cleanup efforts that are being proposed for these oceans garbage patches. Do you think that the research that we have on neuston now could potentially influence any of these efforts, or do you think that we should go find out more information about neuston before we engage in any type of large scale cleanup effort?

[00:26:00.790] - Dr. Mark Gibbons

So interestingly, you say that two of the most recent papers that have come out on this subject have been generated by authors who are affiliated with one of those operations that's trying to clean up the North Pacific Garbage Patch. Their latest data suggests that, well, maybe it's not as… Maybe there aren't as many in Houston. In some of the tax are there. I am cautious until such stage as we more information. The reason I'm cautious is that the Houston environment is massively important for some species at some points in their life. Some fish species, their offspring, live in this system for a period of time that we don't fully understand how long it is. Maybe it's weeks, maybe it's months, maybe it's days. We don't know. But the point is they are found there, and they can be found there. We found off the West Coast of Africa, huge numbers of juvenile fish in that area, in the Houston. If you're going to go in as a cleaning operation and clean it up with all the best intentions in the world, you need to understand the impacts of that.

[00:27:12.110] - Clark Marchese

Sure. We just need to make sure we know exactly what the impact of a cleanup effort would be and do a cost-benefit analysis. Because unfortunately, there's no really way around the harm that we've already done. We just want to make sure we don't make things even worse.

[00:27:29.250] - Dr. Mark Gibbons

I think that I think that is the right approach to have. We have to sit down and we have to measure all these things. But before we can measure, we have to have the data. We need to encourage more scientists to start looking at Houston.

[00:27:44.280] - Clark Marchese

Okay. Well, as we start to wrap up this conversation, I want to ask, is there anything that we didn't discuss about Houston that you think is important to mention in this conversation?

[00:27:55.980] - Dr. Mark Gibbons

I don't think so. I think we've covered all the bases. We've covered all the bases.

[00:28:01.490] - Clark Marchese

Okay, that just means we did our job. But since we have the extra time, I will ask you, do you have a favorite Neuston?

[00:28:08.270] - Dr. Mark Gibbons

Do I have a favorite Neuston? I have to say I like the Water Strider. I just love the idea that this is an insect, that it's the only truly marine insect, and it just sits there skimming around on the surface of the water, just like a pond skater does on a freshwater lake. It's a beautiful animal. I mean, it sits there and it's listening and it's feeling for what's happening around it. Yeah, it's a cool animal. The interesting thing is it's using its eyes. In our survey in the Southern Indian Ocean, we caught more of these things at night in night surveys than we did during the day. It's because these things can see the nets coming and they were skitting out of the way. No, they're cool animals. They're cool animals. I think that's my favorite.

[00:28:54.350] - Clark Marchese

I'm going to have to Google these guys, too, because that sounds pretty cool. Well, then the last question I have for you is, where can people find you and follow your work?

[00:29:02.050] - Dr. Mark Gibbons

I'm an old man. I don't do Twitter or X, and I don't have a Facebook page, and I don't have an Instagram handle or whatever it is. They just have to Go to the university's website, www. Uwc. Ac. Z a, and they can find out a little bit about what I'm doing there, or they can just Google Scholar me.

[00:29:26.170] - Clark Marchese

Wonderful. I will make sure to include a link to that in the episode description so people can find it easily. This is the part where I say thank you so much for coming on the show today. Thank you for teaching us about neuston and also for your research in this space.

[00:29:39.190] - Dr. Mark Gibbons

Thank you. It's been a real pleasure, Claire. It's been a real pleasure.

[00:29:51.740] - Clark Marchese

You've been listening to Plastic Podcast. You can find more information about this week's guest and links to their work in the episode description. Cover art for the show was done by Laurel Wong and the music you're listening to was done by Tadeo Kbejas. I am your host, Clark Markezi, and this episode was produced and engineered by me. If you loved it, one of the best things you can do to support the show is to give us a one-tap five-star rating across platforms or review on Apple podcasts. Plastic Podcasts is part of a larger network of sciencey podcast called Pine Forest Media. You can find more information about us in the episode description as well or on our website at pineforestpods. Com. We've got some exciting science podcasts coming out this-star rating is also one of the best things you can do to help the entire network to grow and for science communication like this to reach more people. All right, that is all I have for you today. Thank you so much for listening, and we will be right back here next week.