Episode 18: Get the Muck Outta Here: Why Muck Removal is Important to IRL Restoration

Low oxygen levels, fish kills and harmful alga blooms. What do all of these things have in common?

Muck. 

On this episode we discuss muck and all the problems this substance can cause in the lagoon and how important it is to remove it. 

What is muck and how do we get the muck out of here? Next, on One Lagoon – One voice. 

Hi, I am Duane De Freese, executive director of the IRL Council and the Indian River Lagoon National Estuary Program. Welcome to our One Lagoon, One Voice Podcast.

Each week, myself or one of my staff members will host leaders in the community, scientists along the lagoon, people who know a lot about the system to talk about some of the problems.

And most importantly, some of the solutions to solve the Indian River Lagoon’s health and make sure it’s great for future generations. So let’s get the show started and let’s talk a little lagoon.

Alright, to help discuss muck and some of the really important things that we have just recently learned about its properties, I’m going to have Dr. Austin Fox from the Florida Institute of Technology with me today. Austin’s a biochemist and specializes in the chemical processes of muck, sediments and the water column. Welcome, Austin.

Thanks for having me. Great to be here.

So, Austin, can you tell us a little bit about the organization you represent and give us a brief hello to all our listeners?

I’m an assistant professor of ocean sciences at Florida Institute of Technology, or Florida Tech. We have some really great programs and one of the really cool things about Florida Tech is we have oceanographers, environment scientists and we also have an ocean engineering program. So we have this kind of interplay between research and engineering.

When we need some equipment or something made that we don’t have, we can solve problems pretty easily here — some really great opportunities to do research. We’re located kind of right in the center of the IRL so we have this great base of operations at our new Merton Center. We have great access to the lagoon, which kind of puts this great laboratory in our back yard where we can jump on a boat, go out [for] a day and learn a whole lot about our lagoon.

One of the things I love about it is, I’m a process scientist, right? I’m looking at chemical processes and biogeochemistry, and [there isn’t] only stuff happening here. There are other places on Earth experiencing the same problems we’re having — there are other places that have already experienced these problems. So we can learn from what other people have done.

And the things that we’re learning have applications beyond just our engineering of the lagoon, right? So, [we have a] great backyard laboratory where you can study these things. We can help our local area, but there are also some broader implications.

Thank you. So, before we jump into muck — and you just mentioned something about jumping on a boat — I kind of want to reminisce a little bit about how you and I met and tell our listeners some of this.

So about 10 years ago now, Austin, I remember being a grad student and you, I think, were getting your doctorate under Trephery. And my wife who was my girlfriend at the time says, “Hey, there’s this great college role position available, you should go check it out.” And I walked into Trephery’s office and I think you were bouncing around.

It was a job to do mapping of muck in the IRL. So [we’ve] come full circle here — whereas back then I was doing some probing, taking the FIT boat out, driving it around and testing for muck. You were wrapping up your doctorate. It’s funny how small of a world it is.

Now that we’re talking about muck, let’s have you kind of explain what muck is. You know, what is it in its simplest form? Where does it come from?

That’s a great question and I think there’s a few different kinds of perceptions of muck, right?

As scientists, we have this very specific definition. But to the public — to most people in the lagoon — you step in this gooey, smelly stuff, right? That’s muck. That’s kind of that everyday definition where I don’t need fancy equipment to tell you it’s muck.

And then we have the compositional definition, right? We take some samples, we bring them back and we analyze [them]. And there’s three things that we’re looking for. The first one is that it’s greater than 75% water by weight. So if you actually take the muck and you dry it out, it will shrink a lot and you’re left with actually very few solids. so it’s mostly water, which we can probably come back to in this discussion.

It’s mostly water and 10% or more of the mass of the dry solids is organic matter. Then 60% of the particles are small enough to be considered silt or clay, right? So [muck is] mostly water, greater than 10% organic matter, and silt and clay-sized particles are those compositional definitions.

Again, that black gooey stuff is kind of the easiest [way to] explain [muck] to somebody. It’s been described as black mayonnaise. Most people have probably smelled that hydrogen sulfite or that rotten egg smell that comes from it, and that’s the anaerobic decomposition that occurs in that muck.

As we start to map it — you mentioned our work 10 years ago, it’s kind of funny – I was out on the boat this afternoon with one of those same poles.

In the muck.

Cool how life comes full circle. And that’s actually yet another definition, right? It’s a lot of work and a lot of cost to go out and collect and analyze these physical samples in the lab. And so, just poking it with these sticks, it’s a process. You get good at it and it’s pretty precise. But that’s yet another definition.

One of the things we’ve worked really hard to do is link these definitions, right? How much can that probe go in before it actually fits that compositional definition? And it’s interesting. If the probe goes in more than about 30 centimeters, it’s very likely to be muck. When the probe goes in less than about 30 centimeters (for most people, that’s a foot), then it’s actually likely to be some kind of gooey sediment, but not quite fitting those definitions that we call muck.

That’s interesting because I remember when I was probing, sometimes just the very bottom of the probe would come up with a little stickiness on it — and it was black. You’d think it was muck, but per this definition, [it] might not have been muck.

Could [there] have been some spreading out from these places where [muck] comes from? We’ll talk about that in a minute. So, where does this stuff come from? I’m sure it’s not a natural bottom. It shouldn’t be in the lagoon, but where is it coming from?

So, that’s a great question. There are natural components to muck — and I’ll come back to that. But most of what we think of muck today has come from over a century of human activities. It kind of began in the 1920s. I mean, there’s some evidence of redirecting water and adjusting our watershed before then, but [it was] really in the 1920s [that] we started to dig channels and drain the wetlands near the St. John’s River for agricultural purposes.

This redirection of stormwater brought with it fine particles that are both naturally occurring in the soils. And as we disturb those soils, we’re causing those fines to be released, and they wash into the water body. So that’s part of it.

Remember, 60% of this stuff is just that fine-grained — only 10% is organic matter. Those fine grained particles that are disrupted by moving of soils are a large contributor. Then the organic matter that’s in it has come from over 100 years of human activity adding nutrients to the system, right? Adding organic material to the system.

So if I tell you [muck is] 10% organic matter, you might think of sticks and leaves and twigs. But if we actually look at muck, the organics aren’t discrete pieces of organic matter. It’s these organic molecules that have coated the surface of those inorganic particles, which causes some challenges when we think of mitigating this stuff because you can’t just go pull out the organic piece of it. It’s intermixed with those inorganics. Over time, those inorganic particles have become coated with the organics and they’re very fine.

If you imagine you go to the beach and you stir up the sand, the large particles are going to settle out quickly and the finer the material, the longer it stays re-suspended in the solution. This stuff is easily re-suspended. So if it’s in shallow areas, it gets mixed back up relatively easily, and slowly migrates and accumulates in these really deep deposits. The deeper areas of the lagoon are where we tend to find this muck.

You just hit the nail on the head on my next question. I was going to say, where do we find a lot of this stuff?

But it seems like the deeper stuff [is probably in] the canals where a lot of the [stormwater] outfalls — because that’s kind of the transportation, right? All these stormwater outfalls is where a lot of these fine sediments are coming from, right?

Absolutely. So, we see a lot of it in canals and in places where there’s an outfall that this material is coming in. Fertilizer and basically any sources of nutrients or organic matter. Then it migrates to the deep areas.

Some of the recent work that we’ve been trying to identify is if muck is all the same? It turns out that it exists on a gradient, like many things do. If you had to break it down into two broad categories, we’ve termed these discrete and continuous muck deposits. Those are terms from the geological literature. But continuous is where we have basically a really broad, deep area of the lagoon, where it’s naturally deep, and we’ve accumulated the fines.

So they’ve accumulated in the deepest spots, and then as you move to shallower water, the grain size tends to increase [because of] higher wave energy. This muck, in these continuous deposits, tends to be less organic rich. It tends to have more coarse-grained material intermixed and the benthic fluxes. The adverse impacts of it tend to be a little bit less, right?

Then we have what we call the discreet deposits. These tend to be in anthropogenically created deep areas, right? So if we’ve dug a canal or we’ve dug a hole to take the dirt to fill land or to build a causeway, those are these really nice, deep areas, and they’ve accumulated those fine-grained materials.

And the muck that we find in those areas tends to be a lot finer-grained. It tends to have a much higher organic content. We’re often seeing up to 20% organic material in those muck deposits, and the adverse impacts tend to be a little bit greater in those discreet deposits.

Perfect. Let’s talk about impacts because you just mentioned them. You know, why is muck such a problem? How does it influence the system? Tell our listeners why it’s so bad.

The best way to visualize this is… I think a lot of people have had a compost pile at some point in their life and that’s effectively what muck is, right?

It’s this organic-rich material that is sitting there decomposing, and as it decomposes, it’s releasing the nutrients. If you have a compost pile at home, you’re breaking down the organics to release the nutrients to then put on your plants.

In this case, it’s just sitting in the bottom, decomposing, releasing nutrients, feeding all of the different things in a lagoon. Hopefully it would be seagrasses and all that stuff. But unfortunately, when there’s too many nutrients, we start to see things like algae and vital plankton dominating and that can contribute to some of the poor water quality.

Sure. So you touched on nutrient fluxes or nutrients. I know these things also flux these nutrients. They’re not just steadily releasing them, they can have massive pulses. Can you touch a little bit on what that means and that process?

That’s a great question with a lot of little rabbit holes we could go down. In essence, this muck is (to some extent) continuously decomposing and releasing nitrogen and phosphorus.

But if we look at sediments in general, we move to something that’s not muck yet. If we look at healthy sediments in the lagoon, we do see them behaving as a sink, right?

In a healthy estuary, the sediments house bacteria that actually carry out a series of processes that remove nutrients. This is termed nitrification, which takes the reduced forms of nitrogen that come out of organic matter as it decomposes and oxidizes it to nitrate, which is probably a form of nitrogen a lot of people have heard of.

Once we’ve gone to nitrate, we can carry out a different process [with a] different set of bacteria that carry out denitrification and they can convert that nitrate into N2 gas. And N2 gas is inert. It’s not bioavailable and it will diffuse back into the atmosphere, not leading to any adverse problems — this is the hope. This is what estuaries are supposed to do, and in healthy estuaries, this process actually helps to remove a large fraction of the nutrients that come in through storm water before that water is discharged into the coastal ocean. Because estuaries are just that area where rivers empty before it goes into the coastal ocean.

What we’re seeing here and what people have seen in other places is as the sediments become less healthy, we start to see chances in the bacterial populations within the sediments. We’re seeing less nitrification happening, right? And that’s the aerobic bacteria. We’re seeing less of those aerobic bacteria that kind of kick off that process of nitrogen removal. As we see less of those, that nitrogen is staying in the lagoon as bioavailable forms that are able to feed algae and those kinds of things.

So as much as I talk about muck and muck being a problem, the thing that I’m worried about is as we see the muck becoming intermixed with those healthy sediments, we’re going to start to lose the ecosystem services that are carried out by those sediments.

Gotcha. And so you just touched on a couple of words and something else that muck is really bad for [that] I want to touch on. You mentioned aerobic bacteria — they use oxygen, right? So then there’s anaerobic, which is no oxygen. And one of the other side effects of muck is hypoxia.

Can you talk a little bit about how that occurs in muck?

Yes, great question. This has been kind of an iterative process in my life here. I started out studying muck and we’ve spent a lot of time learning and understanding the muck. That’s how we started to think about those healthy sediments, right?

I mentioned that as we lose those nitrifying bacteria, we start to recycle nitrogen within the system. Those aerobic bacteria are dependent on the availability of oxygen. And as we have more organic matter entering the lagoon and being recycled through bacterial processes, they’re consuming oxygen.

When we have the water column running low on oxygen, that’s what we call hypoxia. It can be two or three milligrams [of oxygen] per liter, depending on which process you’re interested in. But in essence, it’s just low oxygen that causes problems in the environment with the fish. If we have low oxygen for a couple of days, we’ll start to see fish kills.

My interests are the things that don’t make the news. So, the fish can get up and swim away, and it takes a relatively large area going hypoxic for us to actually see a fish kill. But it’s the things that can’t get up and move that I’m worried about.

Right.

So I’m looking at the infauna and even the epifauna — the crabs and the things.

I’ll go to a site and I just see dead crabs, right? I see dead infauna, dead whelks. Those things don’t make the news. That’s pretty telling, to me. That tells me we’ve seen a pretty significant hypoxic event that may have come on slowly enough [that] the fish could have left and new infauna might come in.

But it does take a toll on the bacterial populations, right? We’re going to see a change in the geochemistry, the bacterially mediated geochemistry happening within those sediments, and it can cause the nitrogen to be recycled versus removed.

So that’s really interesting and I’m glad you were able to elaborate on that. What I’d like to do now is to kind of talk about some of the new projects or the new information, cutting edge stuff, that you just mentioned. Stuff that doesn’t make the news but some of this stuff may be because it’s really important and really interesting.

We’re funding a lot of projects with you and we’ve been looking at this hypoxia and we’ve watched some of these events over the last couple of summers. And last summer in particular, with the big pyrodinium that’s really kind of helped shape some of our knowledge about this subject.

So what I want you to kind of tell us about is some of that work and what you’re learning that’s kind of a big “ah-ha” moment. You know, kind of teasing sediment oxygen demand is a big one that you’ve been really looking into and changes in sediment chemistry. Go ahead and tell us about some of that new work that you’ve been doing the last couple of years and the big “ah-ha” moments from it.

We started out looking at benthic fluxes and that’s the nitrogen and phosphorus. As part of that, we were looking at how much oxygen is being consumed as we decompose this muck. We got what we call sediment oxygen demand. A measure of just how much oxygen are the sediments consuming? It can be really high.

If we look at the sediments, if we take a really mucky deposit, it could consume all of the oxygen from the water column. It depends on where we are and how deep the water column is — but it can be as little as a few hours or as long as a couple of days. And the reason we don’t run out of oxygen is because there’s photosynthesis in the overlying water and there’s wind mixing oxygen back into this water column.

But that really got me thinking, is the organic matter in the lagoon causing us to see hypoxia? There’s some readily available data out there measuring de-O in the middle of the water column, trying to get a good idea of what the oxic conditions of the lagoon look like.

So we started measuring oxygen at the bottom of a few of our sites that we were studying the nutrient fluxes at, and we started to notice that the de-O at the bottom looked a lot different than the dissolved oxygen at that mid-water column. It makes sense because if you think about what is using the oxygen, the bacteria that are decomposing things are really concentrated at the bottom.

But it’s interesting… because if we take a YSI or a sond — or just an instrument that measures dissolved oxygen and you lower it from the boat – we lower it, and it takes a couple of minutes to do it right. It may look like the oxygen’s pretty well mixed. But if you actually let that instrument sit on the bottom for a few minutes, we actually start to see that oxygen tick downwards, which is really interesting to me.

And what we’re learning is just as that instrument goes down through the water column, it’s causing some turbulent mixing and it’s bringing oxygen from the surface down with it. We’re seeing this kind of boundary layer that exists towards the bottom of the lagoon. We realized that you can’t use just this single moment deployment of a YSI or an instrument to track this hypoxia.

So we started using these bottom water dissolved oxygen loggers and deploying them in as many places as we could. It was kind of shocking to us how often we were seeing hypoxia. When we talk about hypoxia and fish kills and things, I think most people are aware of the dead zone in the gulf of Mexico.

Right.

So for a few months each year — most years — the farmers are applying fertilizers to the crops in [kind of] the Mississippi watershed. It rains a lot in the spring. That washes nutrients down, bringing a lot of nitrate into the Gulf of Mexico, and then all of that decomposing organic matter leads to hypoxia — or a lack of oxygen in the bottom water in the Gulf of Mexico.

This wreaks havoc on the fishing there. But that lack of oxygen lasts a few months, so you can take a ship and you can drop these YSIs down and then move to the next site and a few hours later, drop it down again. Over a couple of weeks, you can map the aerial extent of this hypoxia.

As we move into estuaries, we’re noticing you can’t even drop it at a single place and get a good reading, so how are you going to do this all over the place? We’re building this network of these sensors and it’s expanding at any given moment. But we have more than 20 sensors out there now and we plan to pretty significantly increase that number in the coming months.

The really cool thing is, we’re seeing these daily changes in oxygen. So in the middle of the day the sun’s up, we have photosynthesis occurring and we’re seeing the oxygen increasing, as you’d expect. Then at night, the bacterial respiration and even respiration from the phytoplankton lead to this oxygen going back down. This happens every day. That’s what we call diurnal or dial hypoxia — and it’s interesting.

As we see algae blooms happening, we’re actually seeing the oxygen go way up and maybe way higher than we would expect it to be during the day because there’s so much production in the water column. Then at night, that oxygen is consumed and it gets lower than we might expect. In many places in the lagoon, especially during the summer months, we’re seeing diurnal hypoxia almost every single night.

A lot of places in the lagoon are seeing at least a couple of hours of hypoxia, and that’s concerning, right? Because again, the fish can swim up, they can swim away, but the infauna — the things that can’t get up and move — how are they being influenced by that? That’s really what we’re starting to dig into.

At this moment, our real question is how big is that aerial extent of hypoxia? How long does it last and what are the implications of these chronic short-term hypoxic events?

Yeah, that’s really interesting. I wouldn’t have even imagined for an estuary (that’s on average four feet deep) to have these really stratified heterogeneous levels of de-O, and that you could change it just by dropping your sond in. That’s pretty wild.

You mentioned this — and I guess we’re still at the beginning stage of it — what does this all mean to the healthy sediments and eventual restoration that’s going to start ongoing with seagrass planting? How impactful are these chronic, as you say, chronic-acute hypoxic events that are happening almost every day. How is this going to impact those efforts?

I think it’s going to be huge, right? Because until recently, most research is done during the day. Most people are going out and dropping their YSI and they’re seeing that the oxygen’s high.

Now, by being able to say there is this hypoxic event occurring, that’s really informative. We’ve started to think about, okay, what are the implications of hypoxia? Obviously other places have gone through hypoxic events and seen the impacts on seagrasses. Hydrogen sulfide, which we’ve touched on earlier, is toxic to humans. It’s toxic to fish, it’s toxic to infauna and it’s toxic to seagrasses. Right?

It’s formed, again, in anaerobic sediments where just bacteria are carrying out their normal metabolism. And when there’s no oxygen, they use alternate oxidizing agents, one of those being sulfate, which is salt? It’s using one of the salts that make up 8% of the salt in seawater, and it’s converting that sulfate to hydrogen sulfide. That’s that rotten egg smell. Totally naturally occurring. It just means that we have a lot of organic matter decomposition. But that’s toxic, right?

And if that’s becoming more present in the sediments, that can actually make sediments toxic to seagrasses. If we look at some of the approaches to seagrass — where we should expect seagrass to come back — we’re often thinking we may see it recovering in areas where it used to be. It is possible that an area where the seagrass used to be has now experienced enough hypoxia that the seagrasses have gone away and the depth at which we find sulfide is actually migrating upwards. That may make it much more difficult for seagrasses to recolonize those areas.

This is something that’s been seen in other places. There’s models from Laguna Madre in Texas where they’re imaging that a relatively significant portion of their seagrass was lost due to the initial light limitation from algae. But then they’re thinking that the majority of the biomass loss was actually resulting from the hydrogen sulfide that resulted from it.

I was just going to say, that’s huge. I mean, everybody kind of blames these algae blooms. And like you said, that was probably the initial shock that knocked all our seagrass back.

But from what you’re telling me, this muck and this organic matter, this hypoxia is really what’s keeping it from coming back. It kind of tells me this is a huge problem and segues into my next thing. How do we mitigate this stuff? How do we get it out? Are there ways to stop it at the source? What do we do?

So, that is a great question, and I stop and ask myself that all the time, right? I say, “We’re identifying these issues,” and sulfide is one of the issues that we see happening with hypoxia and with the problems we’ve seen in the lagoon. I stop and I say, “How do we remedy this?”

And if we just go back to the seagrass example, seagrasses actually help to mitigate the sulfide in the sediments that they’re living in. Sea grasses create this relatively low-energy environment between their roots, so they actually contribute to the accumulation of fine sediments in the seagrass beds. If you talk to seagrass scientists, they’ll talk about how the sediments used to be squishy and organic rich where the seagrass was.

And when we lost the seagrass, it actually got harder, right? We actually lost some of that organic material. But the seagrasses photosynthesize, they create oxygen, and they actually pump some of that into the sediments using the roots and rhizomes. That actually helps to detoxify the sulfide. It’s interesting, just the presence of seagrasses can help to detoxify the sulfide that might be occurring for a variety of reasons.

This is why we’re looking at the impacts of chronic short-term hypoxia. One of the other things that detoxifies sulfide is reactions with metals. There’s iron that comes into our lagoon through groundwater and surface water. If you’ve seen a fence around Florida and the yard’s watered with groundwater, it’s stained red because there’s so much iron in our water.

But when we see hypoxia, we talked about this anaerobic bacteria. One of the types is using that sulfate. There are other types that use iron and they effectively take an iron 3 that exists as this or amorphous iron complex that actually has charged sites that can bind things like phosphorus, right. It changes and it becomes reduced to an iron 2. Iron 2 reacts very strongly with sulfur (with hydrogen sulfide) to form FeS or Fe2S — a couple of different iron sulfides that can precipitate into the sediments.

That process — the iron reacting with the sulfur — actually helps to remove and mitigate the toxicity of that sulfur. But at some point, the iron that is contained in those sediments can run out.

Gotcha.

If we have chronic hypoxia that’s happening for just a short period of time each night, is it possible that we’re just losing small amounts of iron over time, or iron and other metals that are capable of absorbing it. And eventually, we’ve lost that capacity to detoxify sulfide.

We’ve started down that road, so you’re seeing that there’s lots of questions coming out of this.

Sure. Oh, yeah.

We’ve started down that road and it’s kind of shocking how there’s very little bioavailable or labile iron to be found in lagoon sediments. That’s very likely the result of chronic, short-term hypoxia.

Hmm. So, what everybody thinks about and they hear about is dredging. You know? Let’s dredge it, which is an effective method for removing muck, but you’re not stopping it at the source, so it’s going to keep accumulating eventually.

And now we need this iron source. So there’s another innovative idea out there that some people may have heard about, some may not. Do you want you to touch on capping? Could you put iron in that cap to help maybe facilitate this process?

So that’s a fantastic question and I think we have many tools available to us for restoration. I don’t think there’s any single right answer, right?

I think dredging has some real benefits. I think capping can be a great addition to that. There’s a few capping projects that have happened in the Southern Lagoon. They’ve been pretty successful and there’s been capping — a little tiny project up near Titusville. There’s been capping done in other places, right? It’s not this new idea.

Mm-hmm.

And there’s many different ways you can do it — there’s different additives people can add. So people can add iron, people add … you name it, people have tried to add it to solve some of these problems. But absolutely, I think [there’s] some amendment to the capping.

Normally they’re using quarry sand — basically sand from a place like the lagoon that’s now up on land that they dig out and spread it over the top. It’s interesting because the specific quarry that sand came from may have an impact on its ability to absorb things like phosphorus. That’s just something we should be considering. Then, absolutely, I do think there’s amendments that we can add.

I will be the first person to tell you, I don’t like the idea of adding artificial stuff to try to solve a problem — that’s going to cause different problems later on. But the really cool thing is that iron and these iron oxides are a naturally occurring mineral that is found in our soils. We can basically select a more iron-rich naturally occurring sand for these capping-type projects.

Or, we can supplement the sand that’s available locally with something that would contain something like iron or something else that’s totally natural.

Gotcha. Just for our listeners who may not know what capping is, it’s essentially like beach renourishment. You take in sand and you’re putting it on top of the muck, kind of burying it underneath and as Austin just mentioned, you can have different types of sand and different characteristics. It all depends on what you choose to put out there.

So, interesting stuff. Is there anything else that can be done for muck? I know back in the day, we were typically dredging it out and putting it into what’s called a DMMA, or a dredged material managed area. You were doing some work on trying to increase the efficiency of the nutrient removal from the water.

As we know, [muck is] mostly water and we pump a DMMA full – it’s eventually going to overflow because it can’t carry all the water. So we want to try to clean that water that’s coming out [before] it goes back into the lagoon. So, talk a little bit about that work that you did in the DMMAs.

We were, again, trying to understand the natural processes that happen in the lagoon and how they’re influenced by changes in the availability of oxygen. We’re trying to understand how increasing the oxygen concentration would promote those natural processes and see if we could have the largest improvement possible.

So the lagoon has a lot of nutrients in it — but it sounds weird to say. It’s relatively small, but if we’re testing how much nitrogen we can remove — and the lagoon might have one milligram per liter — then we can only remove one, right? But if we go to these DMMAs, they may have higher concentrations in that water, which they’re treating.

So we went to one of these DMMAs where we could get the highest concentrations of nitrogen we could find to see how effectively we could remove it. We were just testing it, and then a DMMA contractor was like, “Well, can you remove this much?” And we said, “You know, we’re not really trying, we’re just trying to understand the system, but we could help the system and actually probably do that.”

So what does it take for these bacteria that live naturally in the sediments to do their job? They need food, right? They need some kind of carbon source. They need nutrients, which is what we’re trying to deal with in the water. So, that’s available. And they need oxygen. And the other thing they need is somewhere to live, right? And they live on surfaces — they live on the particles of the sand. They live on pretty much any surface you give them. So we started to look for surfaces.

If you look at a bioreactor, it is just promoting these natural processes. They use a type of “media,” which is just the material that you’re giving them to live on. We searched high and low for what the best media was. We tested all kinds of different compounds — things that had been used before. Wood chips, zeolite, perlite, biochar, maize cob, all kinds of different stuff. It turned out that when we used a plastic material — which is what is used in commercial bioreactors…

Bio balls, that’s right. Yeah.

Bio balls, right, it worked really well. The problem is, as an environmental scientist, I’m not going to purchase plastic to be manufactured to throw into our water treatment system.

Yeah.

So we brainstormed and eventually the idea came out. One of my students came up with the idea of using plastic bottle caps.

We tried the bottles themselves but it’s just not the right plastic and there’s potential for degradation. It turns out the bottle caps are actually made out of the same material, polypropylene and high-density polyethylene, which are the same materials used in these bio balls.

And they’re, in theory, free. It’s repurposed, which, if we go back to our reduce, recycle… or reduce, reuse, recycle.

There we go.

Repurposing is actually better than recycling because there’s no energy involved in that repurposing. So we went to the public and we said, “We need help collecting these things,” and it turned out to be a fantastic outreach program.

We were able to connect with the public and most importantly to me [were the] people who wanted to help the lagoon. But they might not have had the ability to go walk in the lagoon and help with some of these restoration projects. It might have been people who just didn’t have the ability to actually go get their feet wet, but it was still a mechanism for them to help.

We collected tons of bottle caps and we were using them as a substrate to grow the bacteria that would naturally be living in the sand. Then we created an environment where they had all the oxygen they needed. We gave them all of the carbon they needed. We let them process the nutrients. And it turns out that when you give them all the things they need, they do their job really well. Right?

From my perspective, we’re using this to understand how to restore the natural sediments. I would love to not have to have a substrate. We just use the sediments as a substrate and we figure out how to make that happen. But we were able to put this in a water treatment system, pump water through it, add the right amount of carbon, add the right amount of oxygen and remove over 95% of that nitrogen in as little as five minutes.

That’s amazing.

It’s just unbelievable how well nature works when it has the tools it needs. So how do we make the sediments? How do we restore that ability to our sediments? That’s kind of the mission that we’ve been on. Why have our sediments lost that ability, right?

Because when we do the calculations — and stop me if I’m going on too long here — but we were like, “This is great. We can treat the whole lagoon using bottle caps. People love it.” At a million gallons per day (which is like a full-size wastewater treatment plant), it would take about 400 years to process the water in the lagoon.

That’s a long time. I’m not going to be around for that.

All of a sudden, it’s just not this practical, large-scale solution. There are absolutely applications to water treatment on small scales in localized places, right? There’s absolutely solutions for those issues.

But we need to be thinking bigger and we need to think about if we have the whole bottom of the lagoon — 400 square kilometers of lagoon bottom and we can restore these ecosystem services to those sediments, that’s huge. We could be processing the whole lagoon in a matter of hours if we’re able to restore those natural processes. And that’s the dream.

Yeah, for sure. So what can our listeners do? Obviously bottle caps are great, but is there something they could do in their house to stop their input of muck? Because I’m sure everybody’s got a playing role to that input of muck — a little bit.

That’s a great question and I guess I have to give a shout out to all our outreach partners and people. The NEP is doing a fantastic job getting those messages out.

Same things you’re hearing, right? Fertilizer, you don’t need it, that’s just a huge one. I think about how much work it is to remove a pound of nitrogen, and then I just cry to see that you can run over to Home Depot or Lowe’s (not being partial to any place) and you can get it. It’s just so easy to get. It’s so unnecessary for lawns and those kinds of things.

I’m working in my yard to get natural vegetation. So we just shouldn’t perpetuate that green lawn idea. I think that’s kind of on the extreme end. And we’re seeing projects to remove some of these normal lawns and put in new bioswales or natural kinds of vegetation — I think that’s really helpful.

Then check your septic systems, check all that stuff. Then, support science, right? I think that’s a huge one.

Sure, we’re learning so much just [from] what you’ve told me today. I’m sure a lot of people have never heard this information. So, definitely, science matters. And it’s going to hopefully give us the tools to right these wrongs down the road — so awesome.

So just touching on that, we’re doing science and there’s actually applications of this. So we’re saying, “How do we fix these sediments?” How do we make them do the job they’re supposed to do?

And one of the things that we’re realizing is that we’re losing [infauna] through these hypoxic events. If we can restore the infauna populations, they dig, right? And it’s really easy to overlook the importance of those diggers. But things that stick their little paws in the sediments — I know they’re not paws — actually help to pump oxygen through that boundary layer at that sediment-water interface.

That can help get that oxygen into the sediments to promote that decomposition of muck, to promote those healthy bacteria and to promote these processes over large expanses of the lagoon. This is something that we wouldn’t know anything about had it not been for research.

Then the really cool thing that I’m more excited than probably anything about is working with our restoration partners. You’re hearing about people starting to do clam restoration, you’re starting to hear people put things back in the sediments that are going to disturb those sediments, and I’m really excited for that potential.

The science can help us figure out where to put those things to be most effective. So we can use the science to help the restoration that will then help the science and it’s this feedback loop that I think has incredible potential. I think just really supporting those efforts is great. We’re learning so much, so much is being done, and I really feel like that there’s hope. I mean, the sea grass that I’m seeing right now is pretty amazing.

That’s great that you mention that because I think a lot of us are starting to see those little signs of hope. And after a decade of pretty bad times, that’s great.

You just gave me an idea, too, for our next podcast. We get to talk to Holly Sweat over at the Smithsonian because she does a lot of work on that infaunal community. There’s a good idea there.

And then you talked about feedback loops — and we obviously touched earlier on these negative feedback loops — with muck and then hydrogen sulfide and death and decay and all this stuff. Seeing these positive feedback loops would be good stuff to see.

[I] just want to say thank you for your time. This has been an awesome discussion and I’m super stoked. I really want to see the new stuff and keep learning about the sediments and the lagoon and how that can play a role in restoration. So, thanks, Austin. Really appreciate it.

No, thank you for having me. This was great, and we enjoy being able to share the work we’ve been doing, so thank you.

Great.

And you should talk to Holly.

For sure.

I’ve been talking to her for years about how we can connect the geochemistry to the infauna. We just got a project through DEP going where we’re actually going to look at infauna and hypoxia and geochemistry at the same sites.