Season 3/Episode 4: Nancy Rabalais: A Deep Dive into the Dead Zone
Nancy Rabalais
Listen
Nancy Rabalais, Professor and Shell Endowed Chair in Oceanography and Wetland Studies at Louisiana State University and the lead scientist on the recent 2023 dead zone cruise, talks with John about the current state of the Gulf of Mexico dead zone, why it matters to the Gulf economy, what it might take to reverse it.
Show Notes
Nancy says that the Dead Zone is second largest human-caused dead zone area in the world's oceans. Read more here.
Nancy shares that the Mississippi River delivers a lot of nutrients such as nitrogen and phosphorus. More here.
More on how nitrogen and phosphorus are critical to the growth of phytoplankton in the Gulf.
Nancy mentions how nitrogen and phosphorus are creating problems massive algal blooms. Read more.
John discusses how the Mississippi River system connects over thirty states. Read more facts about the Mississippi River.
Nancy mentions other areas with dead zones: Changjiang River, the Long Island sound, the Hudson River, and rivers in France. See a map highlighting dead zones around the world.
Nancy discusses how many organisms will be stressed or die off in areas of hypoxia. Read how the Dead Zone impacts the shrimp industry.
Nancy mentions that before Covid, there was an exchange of shrimpers and farmers that would meet in the Gulf Coast. Read about one meeting between a Louisiana shrimper and a Minnesota farmer.
Listen to Episode 1 of Season 3 of Audacious Water, where Lisa Schulte Moore discusses her innovative work with prairie strips as a management technique to reduce nitrogen inputs to Mississippi River.
Nancy shares that the EPA’s Science Advisory Board predicted that it would take 40 to 50% reduction in the nitrogen load to the river to reduce the dead zone. See a 2017 study that provided nutrient reduction targets for reducing the dead zone.
John mentions the interview with Todd Bridges on Audacious Water about nature-based solutions. Listen here.
Transcript
START (NANCY RABALAIS INTERVIEW)
[MUSIC]
JOHN: Welcome to Audacious Water, the podcast about how to create a world of water abundance for everyone. I'm John Sabo, director of the ByWater Institute at Tulane University.
[MUSIC]
JOHN: On today's show, a deep dive into the Dead Zone. My guest is Nancy Rabalais, professor and Shell-endowed chair in oceanography and wetland studies, a member of the U.S. National Academy of Science, and lead scientist on the recent 2023 Dead Zone Cruise. Coming up I talk with Nancy about the Dead Zone and what causes it, its current state based on her recent report, and how climate change might effect it.
JOHN: Nancy, welcome to the show.
NANCY: Thank you. It's nice to be invited and talk about many things that I care about.
JOHN: That's great. It's great to have you. So we're going to start out with a personal question, because I get the boy version of this question a lot. When you were a girl, like, maybe in high school did you think that you'd be where you are today, doing what you're doing today, having the impact that you're having today?
NANCY: Not at all. I thought even in college - I mean, I had no idea where I would end up. But now that I am where I am it's difficult to say what the evolution of all this was, other than I'm a good scientist and I'm very persistent.
JOHN: I like that, especially the last part of that answer. I ask this question a lot when we have speakers of your stature in the university setting, because I think it's important for graduate students to hear it. And I think even at the the stage of graduate school you sometimes can't see that, although some people do. You know, some people know they want to be in position X in 10 years, and they get there. But I think there are many also non-linear paths to that same stage, if you will.
NANCY: Right. I knew I always wanted to study biology; it was my favorite subject in high school and then in college. And got my master's in it, and then my PhD, and it was just always something I was attracted to. And then the coastal part of it came into being when I went to school in Texas and picked up a lot of field work, field trips into the coastal bend area of Texas, and then offshore, and then my first job at Louisiana University's Marine Consortium really got me immersed in physical and biological oceanography. And it's just all - it's all been great.
JOHN: That's great. Yeah, I mean, to give you my - the boy version of this, I was a fly fisherman as a kid, grew up on rivers. I'm a river ecologist now. But I never knew that was a career path, right? So I went to college, pre-med track, did really well, was on track to do something different with medicine. Like, I didn't want to just go be a doctor; I wanted to do something with medicine like Doctors without Borders or something like that. And then by happenstance I saw a flyer in the stairwell from an ecologist from my university, which was the University of Notre Dame, offering a field position for a certain salary for three months in the field in Wisconsin. And they would teach you how to scuba dive. And the scuba dive, like, that was all I needed. I, like, tore that flyer off and went straight to the office of that professor, David Lodge was his name, and knocked on the door. And it turned out I was the only applicant. So I got the job and that's all she wrote. I mean, from there on I knew that I was going to do that for my career. But it took that - you know, that kind of, like, chance event to get there.
NANCY: Right. I started scuba diving when I was 19, so I was still in college, and it was just recreational. But then it became part of my professional career as well, putting instruments on and off platforms in the Gulf of Mexico. And it's just always been part of my life. I don't dive anymore now; I'm just not as strong as I used to be and as good of a swimmer. So I've kind of decided that's not safe.
JOHN: Well, good for you. I mean, 19, that's about the same time I learned how to scuba dive. And I think one of my post-doc mentors used to call--kind of what you just described--he used to call it--and he's a desert ecologist--but he used to call it "cowboy biology," which I think is interesting. All right, so let's dig in. What is the Dead Zone? What causes it? And why is it so important for the gulf ecosystem and economy?
NANCY: So you want Dead Zone 101 right now? [LAUGHTER]
JOHN: Yeah, give it to me. But let's - just tell me what the Dead Zone is first.
NANCY: Yeah. The area called the "Dead Zone" is not completely dead, so I try to avoid using that, certainly professionally. Although the public understands that word; they know what it means and they're used to hearing it. But not everything is dead. The area in the Gulf of Mexico off of Louisiana and adjacent to the Mississippi River, along the Louisiana Coast and into Texas, and often into Mississippi, is an area with very low oxygen. And the technical word for that is "hypoxia." But I try to stick with "low oxygen," because people can understand that better. The area of low oxygen is large. It's the second largest human-caused area in the world's oceans, at least in the coastal areas. There are natural areas of low oxygen in the open ocean, but this results from human activity in the watershed. The area is what we call "stratified," which means the water column is layered, and the Mississippi River delivers a lot of fresh water which is less dense than the saltier Gulf of Mexico water. And there's a layered system through much of the year. And that layered system prevents oxygen from the surface from reaching the bottom. And it gets depleted because of the biology of the system is that the Mississippi River also delivers a lot of nutrients such as nitrogen and phosphorous, which are critical to the growth of phytoplankton, single-celled plants in the Gulf. And the concentration of the nutrients, nitrogen and phosphorous, have gone up over time related to changes in the watershed, and particularly since the 1950s when there was the beginning of artificial fertilizers put on the land. And there's basically too much of what is good for agriculture getting into the Gulf of Mexico and creating problems with massive algal blooms, not necessarily toxic algal blooms or harmful algal blooms, but phytoplankton blooms that are not completely consumed by the zooplankton, or many of the cells will die and sink to the bottom. There's a lot of organic matter from the surface that reaches the bottom, the seabed, in 5 to 30 meters of water, and the bacteria love this organic matter. They can consume it, and in the process they use up oxygen. And without that resupply of oxygen from the surface the bottom waters become depleted in oxygen. That's the science behind it.
JOHN: It's a big system. Let me play that back for you just to make sure that I have it and the listeners have it. So you've got the Mississippi Basin, which has a lot of agriculture--and we'll come back to that--uses a lot of fertilizers that have nutrients like nitrogen and phosphorous, and the river takes those to the nearshore ocean, shallower ocean. And that fuels phytoplankton production. Those phytoplankton don't all get eaten and they sink along with organic matter between the freshwater layer that's on top into the saltwater layer that's on bottom. And that saltwater layer has a limited amount of oxygen for microbes to eat that. And so that just chows the oxygen levels down in that lower layer. Is that a decent summary?
NANCY: Right. The layering is not just fresh and salt. The freshwater dilutes with the more saline water, the saltier water, in the surface. And so that surface water is less salty. And the bottom water, if it's not mixed, remains saltier than the bottom. So that's the difference in salinity, the salt levels from the surface to the bottom. And the temperature is also important. The areas responsive to surface water temperature, which is hotter in the summer than it is on the bottom... So you have both temperature and salinity creating this - and organic production creating this area of low oxygen.
JOHN: Got it. So interesting. And I think - you know, I think it's interesting in the context of this series, which is on the Mississippi River, to think about this as a system that is really enormous, you know, covers, you know, more than 30 states, the Mississippi Basin of the United States. And then has this relatively local impact, right? So let's talk about that impact. Why is this Dead Zone or area of hypoxia, low oxygen, important for Gulf ecosystems and the economy?
NANCY: I look at the Mississippi River watershed and the coastal waters in the Gulf of Mexico as one ecosystem that is joined or linked by the Mississippi River discharge. Because both of the ecosystems respond to each - most of the water - precipitation that falls on the agriculture fields in the Midwest is generated in the Gulf of Mexico. And most of the nutrients that are reaching the area where the low oxygen is generated come from the Mississippi River. It's the overwhelming source. The area of low oxygen can be very large, up to 22,000 square kilometers, or it can be - and especially when the river is delivering more nutrients and more fresh water, such as in flood conditions. It'll be smaller when the amount of nutrients delivered to the river are less, and that's usually during lower river discharge. So the river has a lot to do with the size, which can be up to 22,000 square kilometers, and almost negligible this last summer at 7,900 square kilometers. And it was the sixth-smallest area we've documented since we started doing this in (1985), if you can believe that. That's how - I like to say I started doing this in kindergarten, because it's been a long time. But (1995). The area is considered, as I mentioned earlier, the second-largest such coastal area that's human-caused in the world's oceans. And there are a lot of these areas around the globe in the coastal ocean that have very similar problems, such as the East China Sea off of the Chang Jiang River, the Long Island Sound that received the effluent of New York City, the Hudson River and other rivers in the sound, off of France - lots of areas have this. And it's usually related not only to the physics which is needed to support it, but having too many nutrients delivered to the coastal zone. And that's consistent...
JOHN: That piece is interesting, because I always thought that it was probably the nutrients, the supply. But you need the physical conditions, the physics as you said, to make that happen as well.
NANCY: If it's not layered of stratified then there's no obstruction of oxygen getting to the bottom. And it will diffuse from higher surface oxygen because of the production of oxygen by phytoplankton to a lower level, which is more at the bottom. So the oxygen will get to the bottom if it's not layered, and will alleviate the low oxygen. The low oxygen occurs mostly in the spring through late summer, early fall, and the temperature makes a big difference in the layering of the system. But the system is layered most of the year anyway, unless there's a cold front or tropical storm just because of the differences in the water column.
JOHN: Yeah, that makes sense. That's an excellent science background. Let's transition. You kind of started into the 2023 report on the Dead Zone that has recently come out, and it was I think you said the 6th lowest since you've been measuring since 1995.
NANCY: That's correct, yes.
JOHN: Last year was also low.
NANCY: Last year was the 8th lowest.
JOHN: Both years were years with low discharge. How do you view discharge - obviously discharge is a driver of this big coastal issue. How should we think about the Dead Zone in the context of climate change and changing discharge in the Mississippi?
NANCY: The basics of the size is not just the fresh water that's delivered to the coastal ocean, but also the nutrients, the nitrogen and phosphorous that are in that water that support the phytoplankton. The physics is driven by temperature and salinity. The biology is driven by phytoplankton-enriched coastal waters because of nutrient delivery in that fresh water. The best predictor for the size that the low oxygen area is going to be in the summer is the May nitrate load, or nitrogen load, through the system, and the phosphorous load that - nitrogen really dictates the size of the low oxygen. And the prediction in May based on the load of Nitrogen that's going to reach the river during that month is displaced in time from our survey of the low oxygen. And the water will come in, it'll stimulate phytoplankton. The phytoplankton will grow. Some will support the food web, some will sink to the bottom. But that takes a long time. And the area of low oxygen is most prevalent in the summer, but the May nitrate load and the subsequent carbon flux to the bottom, organic matter, is what drives the low oxygen, not just in May but also in the summer. There's enough carbon reaching the bottom that in the summer with layering of the system there will still be low oxygen. But if the fresh water decreases substantially in the month of July there's less layering, and so there's less physics supporting the development of the low oxygen.
JOHN: So interesting. It's, you know, a much more complex system than just delivery from ag lands.
NANCY: And the physics of the continental shelf is also - is very important. There are gradients in depth, there are distances from the discharge, there are differences in time of delivery of the nutrients and the freshwater discharge. There are differences from year to year, depending on how the coastal winds are blowing from the offshore, or from the north, or from the west, or from the southeast. So most of the time the winds are from the southeast, and most of the organic matter that's produced goes from the east to the west, and then falls out.
JOHN: That was my next question is - is exactly that. Like, when you look at the map it drifts west of the mouth. And so that's mainly wind action and direction of wind?
NANCY: And the currents, right. The coastal winds dictate the coastal currents. And for most of the year the currents move from the east to the west, and carries nutrients that are diluted along the way, but also regenerated by living organisms. So there's sort of a constant supply of nitrogen. Phosphorous will fall out closer to the river because it's more associated with sediment particles, but not always. There's inorganic or non-sediment phosphorous that also is important. And the Atchafalaya River carries about one-third of the total discharge of the Mississippi River. In years with higher discharge you can see in the maps that we generate areas west of the Mississippi and west of the Atchafalaya that are not always connected. But some years you have a continuous band of this low oxygen. And that's when you get the much higher areas calculated. The winds on the continental shelf blow mostly from the southeast, especially during the period of high discharge of the Mississippi River. And a lot of the high nutrients and organic matter moves from the east to the west. In the summer the winds reverse and come mostly from the south or the southwest, which pushes the mass of low-oxygen water from the west to the east. So it can be configured on the bottom very differently depending on both the amount of water and the wind directions. The area is also affected by the discharge and nutrients from the Atchafalaya River, which carries about one-third of the Mississippi River total discharge, and it affects the area, again, west often into Texas. And sometimes those areas are disjunct, they're not continuous along the continental shelf, but in some years you can have low oxygen on the bottom from the Mississippi River Delta well into Texas waters off Galveston or Freeport. Those are very large years. But if you get a hurricane that comes through during any of the time that we're mapping the low oxygen, it'll force oxygen from the surface to the bottom, and the area at the bottom will be smaller. So some of our smaller years are because we've had tropical storms or hurricanes come through the study area. And it takes a while for the system to settle back down and develop that layering system (for) the low oxygen can begin to be consumed again.
JOHN: That's interesting.
[MUSIC]
JOHN: Coming up I talk with Nancy about how the Dead Zone impacts the economy, how our lives would be better if the Dead Zone disappeared, and what it might take to reverse it.
[MUSIC]
JOHN: Let's talk about people and the economy, and what's the impact of low oxygen or the dead zone on communities and the economy in the gulf?
NANCY: The area of low oxygen can be quite large, as large as the State of New Jersey at times, or 10 times the size of Lake Pontchartrain, which we know better it can be 10 times the size of Lake Pontchartrain. So it's a large area. And when the oxygen falls below 2, which is our cutoff for hypoxia or low oxygen, organisms that live in the bottom layer have to escape or die. The fish and shrimp, most crabs, can swim out of the area, but the organisms that remain there will be stressed or die off. And that's not good for the environment and it's not good for nutrient and carbon cycling in the sea. It also causes the organisms that fishers or trawlers are trying to catch to move out of a very large area in the Gulf of Mexico. So there is habitat that is reduced in the summer when the Dead Zone occurs. Now, shrimp are very prolific spawners, and we have seen a decadal decrease in the brown shrimp catch, not the white shrimp, just because of where the low oxygen occurs and the lifecycle of the brown shrimp. They spawn offshore when it might be enough oxygen, but then when the post-larval forms, the shrimp, the juvenile shrimp, or the real shrimp start to migrate offshore, they hit - it's like hitting a blockade of low oxygen. And they have to go up in the water column or move to the east or the west, and get out of that area. So that reduces the suitable habitat considerably. The catch though remains high because it's such a productive system, and because many of these fish are prolific in the amount of larvae that they generate and the juvenile fish that come from them, and the shrimp. But the ecosystem functioning is really very important for sequestration of carbon, or generation of carbon, or ocean acidification, which may affect other organisms. So there's a lot of environmental impacts that we haven't really quantified yet. The shrimp industry is still strong, but because of this mass of low oxygen the shrimp that move offshore in the summer when the hypoxia is present are a lot smaller because they haven't made it offshore yet to grow big. They are sort of corralled into the inshore waters and they can be caught very easily by trawlers. But they're small so they don't bring in as much value as the larger shrimp offshore. If the shrimp can get to the offshore side of the low oxygen they can grow into much bigger size, and can be captured at a bigger size, and can be sold on the market for much greater profit than the small ones they catch on the inshore edge. The economic value of that, however productive it is, is threatened by the import of foreign shrimp, which are usually cultured in ponds that have replaced productive coastal habitats such as marshes or mangrove swamps. So it's not only bad for the local shrimpers, but also bad for the environments where they're being grown. There's a big push to eat Louisiana seafood, and the brown shrimp is a good example of trying to eat local shrimp instead of imported shrimp.
JOHN: So it's a complex problem, and it's - I mean, there are multiple stressors on shrimp, one of which is the dead zone, which seems to affect the location and size of shrimp caught, which has an impact on profit for shrimp trawlers. And then there's this external pressure, which is foreign imports and aquaculture I guess, right?
NANCY: Right. There's also an international economic effect on growing agricultural products in the Midwest, because they're tired to loans that might be tied to commodities that are owned by somebody else, and they can't get a good price for their corn products. So there's economic effect both in the Midwest and in the Gulf of Mexico.
JOHN: So let's dig into that a little bit. Is there a connection between the economics in the Midwest and what shrimp trawlers can catch and profit on? Or are they both driven by the same process?
NANCY: I'd say they're driven by different processes economically, and meteorologically, and biological. But they do make an end-to-end ecosystem from North Dakota to Galveston, Texas.
JOHN: Right. No, I like that concept--it's a good visual, and it's comprehensive. Because I think a lot of people think, oh, there's land, there's fresh water, there's the ocean, and your concept is that that's all one ecosystem.
NANCY: Right. Another issue about the nutrients in the river, many of which end up in the Gulf of Mexico, is that they also affect freshwater environments up in the watershed in the Midwest with--and this is more of a phosphorous issue--with the generation of toxic cyanobacterial blooms often called "blue-green algae," and they're toxic. And they can close swimming areas, they can kill small animals, pets that might get into them, and even human beings. And the nitrate levels in some of the rivers in the watershed are too high for drinking water, and nitrate can cause problems - health problems.
JOHN: Interesting. Yeah, I like that kind of - thinking about that as a connected challenge. Because I think it's hard for people--you know, I'm just going to spit this out and say it out loud--I think it's hard for people in Louisiana, living in Louisiana, to think about--and I live there--thinking - to think about problems that people are having in Iowa being connected, and vice versa.
NANCY: Some of the people around the Gulf do understand the connection to their watershed, but a lot don't. But with regards to hypoxia there's been some really good exchange of information between the agriculture community and the fishing community. They don't do it now, but they used to before COVID, have an exchange of shrimpers and farmers that would meet in the Gulf Coast and eat shrimp, or steaks that came from the Midwest. And then there are times when the fishers go to the Midwest and see their economy, and eat their food, which is mostly steaks.
JOHN: Yeah, we'll come back to that in a sec, because I think the shared visioning is important. And on that note I want to vision with you a little bit. I would imagine you've thought about this quite a bit, but what would it be like if the Dead Zone were gone? What could we do better? How would our lives be better?
NANCY: The amount of nutrients reaching the Gulf may be less, because that's the basis for the productivity. And that might effect fish productivity or shrimp productivity if you cut the nutrients off. However, there have been still-high yields of fish, and still-high yields of shrimp so that just if the low oxygen were not there we may have a more productive system, but we have a productive system already. And it's hard to believe that it hasn't always been - the low oxygen in the Gulf has not always been this low. And we don't have data to take us back that far. But we collect sediments in the area of the Mississippi River discharge, or even farther away off of west Louisiana, and we can collect those sediments with core tubes in a big box corer, and slice them, and be able to date them with lead 210 and cesium, and know that the surface of the tube is more recent than the bottom of the tube. And you can look at indicators in those sediments cores for biological productivity, changes in chemical, changes in isotopes, changes in organisms that live in the sediments. And those cores tell us that the low oxygen in the Gulf was not always there in the area that it is now, or at least to the extent. And it's been human activities that have added to the productivity of the system, which in ways can be negative.
JOHN: Got it. Let's keep on this track of vision. So before industrial agriculture in the United States, or before large-scale let's just say, there was a lower impact of the Mississippi River discharge of nitrogen on oxygen-concentrations on the nearshore in the Gulf. What do we need to do to get back to that point? Like, what scale of investment in research or in projects - what do we need to do?
NANCY: There is a hypoxia action plan that ties the Mississippi River Watershed to the Gulf of Mexico. And the focus of that action plan is to reduce the nutrients to the level that the low oxygen would not be larger than five square kilometers over a five-year running average. And most of the actions that are being looked at in this action plan are tied to the states, that discharge into the mainstem of the Mississippi River, or the Ohio River, or the upper Mississippi, or the Missouri. And those are usually agriculturally-oriented activities such as working with tile drains, which facilitate the runoff of the water from the cornfields. Or buffer strips that keep nitrogen from getting into the nearest drain. Or alternating crops. Or having crops being present all year long instead of only when they're growing crops. Because otherwise the bare soils don't retain the nutrients the way that vegetated soils do. There's many agricultural practices that can be employed and still have productive agriculture.
JOHN: This is such a great link to the podcast that we had earlier with Lisa Schulte Moore, who has been innovating prairie strips--and I think you mentioned buffer strips before--in Iowa as a management technique to reduce nitrogen inputs to Mississippi River tributaries.
NANCY: Those buffer strips are very important. There's less nutrients to come off the agricultural fields when there's a buffer between the fields the river, and all the other practices that I mentioned can also reduce the nitrogen coming off of the land. The cover crops and diversified agriculture, or different kinds of crops being interspersed with the growth of corn, there's just all kinds of things that can be done. It's not the standard. It's not the usual for the Midwest since at least the beginning of the 19th Century, when bigger agriculture, and more tilling of the soil, and more use of artificial fertilizers, especially since the early 1950s, shifted to mass production of single agricultural products.
JOHN: Got it. Let's talk about scale. You compared the dead zone to the size of the State of New Jersey. And when you were mentioning those numbers I was thinking Rhode Island, but New Jersey is bigger. And so that's huge. So tell me in that context, like, the size of a state, what kind of scale of investment of these best-management practices, and prairie strips, and buffer strips do we need to invest in to get to this five-square-kilometer, much smaller area?
NANCY: The EPA had a science advisory board that looked at this question, and they came up with a percentage reduction, but they didn't put it in acreage and types of agricultural products. When we began the work we thought - and the low oxygen area was smaller at the time we started in 1985, not small-small, but big enough for us to be out there studying it, but not to the degree that it became beginning in the early 1990s. To reduce the area offshore the EPA science advisory board predicted that it would take 40% to 50% reduction in the nitrogen load to the river to reach that size. And that's a lot of reduction. And that's a lot of best-management practices and a lot of reduction in artificial fertilizer. So it's a huge issue.
JOHN: Probably an area greater than the size of the State of New Jersey, right? Like several ord- maybe even an order of magnitude bigger in terms of area of application of those practices.
NANCY: The low oxygen area can only be so big because of bathymetry of the Gulf of Mexico, the distance from the river. So there's a defined area where it can be physically supported, and that's not going to change much because the basic geology, and the currents, and the winds aren't going to change that much over scales of time that we would be able to detect a difference in the area of the low oxygen. Now, climate change is predicted to aggravate the low oxygen. And there are people that have looked at that, and we can talk about that if you want to.
JOHN: Well, let me just clarify my question. I like the answer because it tells us that at least if we set climate change aside there's a bound to how big it can be based on physics. And the question I was asking is, how much land area, not ocean area, how much land area under agriculture is required to change to best-management practices in order to get to this 50% nitrogen loading reduction and 5-square-kilometer Dead Zone? I mean, do you have a back-of-the-envelope guess? Is it bigger than a big Midwest state?
NANCY: I can't answer that question. We have equated the area of low oxygen to acres, and I can't - that one I can't do right now off the top of my head.
JOHN: That's fine. I think for all intents and purposes of this podcast my own personal opinion, and not yours Nancy, is that it's a huge area, much bigger than the State of New Jersey. And this is a good tie-back to the interview with Todd Bridges on nature-based solutions. And I think there Todd gives some numbers, some guesses, some back-of-the-envelope educated guesses I threw him based on science. But we can move on. I think one thing that I wanted to bring up is I just recently did a road trip from the mouth of the Mississippi to the headwaters in Minnesota. Took me a week to drive that. And one of the observations that I made, which was influenced by a discussion that we had before I left, was that the river is completely disconnected from land all the way from Louisiana to almost Minnesota. How are these nutrients getting into the river--tell me a little bit about that--if we get a levee all the way up?
NANCY: They come mostly - the nutrients come greater than 70% from agriculture activities, but there are cities that produce nitrogen and phosphorous products in atmospheric deposition, which can be tied to agriculture. I've thought of that before, and it doesn't really make that much sense except the levees aren't - they can be leaky, that water can run under them, and there are places where if there's floodwaters they an get pumped directly into the river to alleviate flooding. When the river was more free the water could expand into the floodplain and there would be natural assimilation of those nutrients. But now that it is particularly leveed then it's a straight shot to the Gulf of Mexico.
JOHN: Right. That part makes sense. And what I was thinking, and the idea came from - we actually visited Lisa and one of her experimental farms in Iowa, which is really far away from the river, you know, near Des Moines and Ames. And what I was thinking is that the tributaries are probably all those sources, right? So...
NANCY: Right. The tributaries as well, definitely. Most of the water comes from the upper Mississippi, second the Ohio system, Ohio River system, and then the Missouri River system is third, looking at those large amounts of land that are drained. The sediments that reach the Gulf of Mexico are primarily from the Missouri and not the upper Mississippi or the Ohio system. So different processes, or different human activities in those different large sub-watersheds are very important to the nutrients that get into the river. The Ohio, if you looked at a map of where the nutrients are located, there are hotspots in the area where the agriculture is highest, and not all of that is leveed.
JOHN: So we're both professors, we're both trained graduate students, undergrads. How do you train and how should we be training our students to make a difference for this big issue in the future?
NANCY: I think it's very important to combine the socioeconomics with the biology and the physical sciences. Because people are part of the ecosystems in both the watershed and in the Gulf of Mexico. So linking socioeconomics with physical and biological processes I think is very important, and it helps to understand better how ecosystems function, including the human part of those ecosystems. There's been a big push to integrate those types of science in the last 30, 50 years, which is very good. I also think that if you conduct science, like I do, you also need to communicate it to the public. And one of those ways is to be a good communicator or translator of the science, and preparing students as they come out of college or graduate school--they need to be able to communicate the science and have it make sense to the public from kindergartners to Presidents of the United States. And that is a skill that is not as well-developed in most of our graduates as it should be. And I teach a lot of communication of science, and I think that's very important that our scientists need to be able to translate their science to the public.
JOHN: Amen to that. That's the underlying motivation for doing this podcast and having great communicators like you on this show. Last question for you. This question is motivated by my uncle, who had a huge impact on water systems in California, and managed water systems in California. And the legacy of that is - will live on for more than a century I think, and that impact has always motivated me and what I do in my career. What do you want the legacy of your work to be?
NANCY: I would like my legacy to be carried on by other studies of the Gulf of Mexico. And I've been starting to transition some of my hypoxia research to an assistant professor at LSU who's taken over the grant. I'm still a PI and I'm very involved, but keeping the continuous watershed issue from the Mississippi to the coastal Gulf of Mexico is very important. And I would like for that information to be in the minds of people as they move forward into developing solutions as best as they can. I would also like the Gulf of Mexico to maybe be a cleaner body of water, because it's not just nutrients, it's chemicals that come into the Gulf of Mexico. I would like to see the water managed better across the U.S. and the globe, because it is a rare resource in some areas. And to protect that water is going to be very important for the economics and the biology of the systems.
JOHN: That's impressive. I mean, it's a great vision and I especially like the callout to young leaders and continuity of a knowledge base. That's super important for managing a system. And I want to thank you for the interview, and I also want to thank you for your work in this space, because it's super important.
NANCY: Well, thank you for having me and letting me talk about these things to the public in a different way possibly.
JOHN: Appreciate it, thank you.
NANCY: You're very welcome.
[MUSIC]
JOHN: I hope you enjoyed that interview; I sure did. Couple things I'm thinking after this interview. The first is this concept of an integrated ecosystem from land to fresh water to ocean. Thinking about the ecosystem this way really provides a nice framework for managing it better I think. And so I want to just stress that. The second point that I think is really important is this idea that the river has a levee from New Orleans all the way to Minnesota. How does the nitrogen get in there in the first place? This caused some pause for both of us, both ecologists, and I think it's an important point. The nitrate is probably getting in through tributaries and through groundwater, not to the mainstem of the river. And I think more importantly Nancy also showed some caution in advocating for coastal restoration as a tool for filtering nitrates going into the Gulf. The sheer discharge of the river just overwhelms what could be possible in Louisiana alone. And I think when we go back to that integrated ecosystem piece it suggests that we need to take a base-and-scale perspective on it. This is the land of clinical trials, which I've written about in Forbes. We need to generate a general set of principals for science that allow us to strategize where to do intervention with nature-based solutions in particular across the watershed, such that we can improve the integrated health of this ecosystem that starts at land and ends at ocean. Thanks for listening.
[MUSIC]
JOHN: That's it for this episode of Audacious Water. If you liked the show please rate or review us and tell your colleagues and friends. For more information about Audacious Water visit our website at AudaciousWater.org/podcast. Until next time I'm John Sabo.
[MUSIC]
[0:45:51]
END (NANCY RABALAIS INTERVIEW)