We have visiting us, doctor Alia Alas. Alla is currently a post doc at the Smithsonian Environmental Research Center right across Chesapeake Bay, down in Edgewater. She's doing some really cool work. Salt marshes and plants and how these coastal blue carbon heap assistants might also be greenhouse gas producers. Before starting this postdoc, Alia earned her PhD at Boston University and Wally Fowler's lab. So we were lab Mates there together and it's pretty fun to have Alia out here sharing her work that she's been doing since I've last known what you've been doing. Before Boston University, she was working at University of Virginia where she earned her undergrad and master's degree. Take it away. All right. Thanks, Nick. I kind of moved up from seagrass into salt marshes when I moved up the title area, I guess, F seagrasses into Salt marshes when I started at Circ and it's been a fun transition. Anyway, so if anybody else has sea grass questions, I'll love to talk about seagrass Cap too. All right. But today, I'm mostly going to focus on coastal wetlands. So salt marshes, brackish marshes, coastal freshwater marshes. No totally freshwater. Tidal marshes. And so we know that the coastal wetlands provide many ecosystem services to coastal areas. And some of the things I'm going to talk about today are carbon sequestration and storage, how they act as the nitrogen filter, and how they react to storm surge. And so we know that coastal wetlands bury a large amount of carbon, and that that carbon burial is actually pretty variable, which you can see here from this image from Rosener at all, 2021. So when we're thinking about carbon burial, these systems vary carbon because they're highly productive break. Super productive ecosystems, they perform photosynthesis, take up carbon dioxide, release oxygen into the atmosphere, but also into their sediments. And that oxygen, they also release organic matter to sediments. And that oxygen gets used really quickly during organic matter breakdown. Then we move down into anaerobic processes for organic matter breakdown, which is really what I think about most of the time. And one of those processes is denitrification, which can produce N two or nitrosoxide. I'll mention nitrosoxide today, and we can talk about nitro coxide after. But I don't have a lot of nitrosoxide data to show you at this point. I will soon if you're going to HU, we'll see some more nitrocoxide data. But today, I'm mostly going to focus on methane. And so methanogenesis is this lowest step in the redox ladder. It's the least energetically efficient way to break down organic matter and coastal systems. But we know that methane actually is a really important greenhouse gas. It does a stain fluxle boring potential 45 times out of carbon dioxide. It's really important that we understand how methane production or how methane emissions are impacting coastal ecosystems, and how they'll change with climate change. And so sorry, one of the controls on methane emissions in coastal systems is sulfate availability and or sulfate reduction because that's a directly competitive process with methanogenesis. So the methanogens directly compete for acetate and CO two and h24 with sulfate reducers. So sulfate reducers usually outcompete those methanogens. So when you have increases in sulfate concentration, like you do when you have higher salinities, you often see a decline in your methane emissions. And so that's pretty common across coastal marshes, coastal wetlands. And so that's one of the reasons why greenhouse gas emissions from coastal wetlands are one of the reasons why we have variable carbon storage and one of the reasons why we have these pretty variable greenhouse gas emissions from coastal wetlands. But right now, we really need to also think about the future and how these greenhouse gas emissions are going to change. Because when we're thinking about, especially methane emissions, we want to think about the balance of carbon being stored in marshes along with the amount of methane that's being released. Right? We need to know if our marshes will remain carbon stores or if they're going to become like releasers of carbon. Net, Yeah. And so the impacts of climate change that I'm going to talk about today are warming and sea level rise and how those impact our greenhouse gas emissions from Coastal Wands or methane emissions from Coastal Wlands mostly today. And those are like our longer term impacts of climate change. But you also want to think about the short term stressors. So heat waves and hurricanes and kind of how they'll impact our methane emissions from these systems. And so one of the reasons why I'm doing this is because a lot of the experiments at CRC use this like Mtex model experimentation model. So we to accurately actually predict future greenhouse gas emission and carbon storage and coastal s, we need to do a better job of modeling anaerobic biogeochemistry. And we need to know the interactive impacts of climate stressors. And we need to have models that are informed by experiments and experiments that are informed by models. We use this structure to answer this over arching question. How is climate change impacting coastal wetland, greenhouse gas emissions, and biogeochemistry? And I'm going to talk about three experiments that I've done at sir. What are the interactive impacts of warming sea level rise and salinity on methane emissions from coastal marshes? Is the first question we'll get at. Then we'll look at methane production pathways derm and sea level rise at two different salinity marshes. And then we'll get into our shorter term stressors. So how do these short term stressors impact hot moments of greenhouse gas emissions? Specifically, thinking about changes in inundation, solidity, warming, and nitrogen loading. I'm really interested in these iterative impacts of these stressors as well. So we'll start with our first question. And before we really get into that question, I want to talk about CRC a little bit. So especially for any students out there. Here in undergrad, there's lots of REU opportunities at CRC during the semester, during the summer, after you finish undergrad. And we have this really great place called the Global Change Research Wetland, which I feel really lucky to be able to work at. So the Global Change Research Wetland has had experiments looking at the impacts of climate change on marshes, going on for almost 40 years now. And so we have a lot of data from this on the impacts of climate change on Marsh carbon cycling. And so we know that vegetation biogeochemical feedback models, we're really lacking information on the iterative impacts of climate change on greenhouse gas emissions. So we've been using data from SRC to kind of improve these models. And one of the main models we work on is called P flow tran. And that's a reactive flow and transport model that was originally created for terrestrial ecosystems. And so Terry mira, who now works at the Oakridge National Lab has been doing a lot of work to modify this model so that we can also use it in coastal systems. Some of the first things she did with previous data from G crew were to add tidal variability into this model, and add in vegetation feedbacks and add in anaerobic biogeochemistry. Then in the second iteration, we've been doing experiments to help us improve this model since then. And in the second iteration, we have added diurnal variability of methane emissions, which we found by running auto chambers. We found that there's dinal variability of methane emissions by running auto chambers on our marshes. And have added the impact of warming. But with this, we haven't been able to really add impacts of climate change that would really stress our marsh. Like we can't just like dump a bunch of water to look at sea level rise on our marsh. We can't change the salinity of our marsh without ruining all of the 40 years of worth of experiments we've been doing. So In order to kind of figure out how climate change is impacting marshes other salinities and how sea level rise is impacting these marshes and greenhouse gas emissions. We did a marsh Oregan experiment at two places on Circ campus. So Sir kind of spans a very large area. And so we have freshwater Title creeks that are running into a brackish coastal system on the north part of the Chesapeake Bay, basically. And so throughout the experiment on the throughout this talk, on the left side will be brackish marsh, ten parts per thousand. And on the right side will be what I call freshwater marsh. So zero to three parts per thousand. Sorry to the actual freshwater people. And so with this experiment, we wanted to quantify the impacts of sea level rise and warming on methane fluxes from these two different types of systems. And so we know that individually. We know some of the individual impacts. So we know that methane emissions increase with temperature. We know those ten values, and we've seen on our Martha G crew, that our methane emissions increase when we warm the soil. We also, again, we know that methane emissions decline with salinity. And from another March organ experiment at G crew, we know that methane emissions increase with inundation. So for our experiment, again, we performed this smart organ experiment, and just going to quickly go through the design, I guess. So we had both vegetated and bare pots because we wanted to kind of get at that impact of vegetation as well. We heated half of these pots and we left half of them at ambient temperature, and we used a novel continuous heating feedback system so we could keep our temperatures six degrees Celsius above ambient consistently. And we also designed the experiments so that we looked at pots that are we 10 centimeters above the current marsh elevation at the current marsh elevation, and then 10 centimeters below the current marsh elevation. So kind of as a way to look into the past and the future. The sea level rise. And so we measured methane fluxes, as well as poor water constituents. And we like every three weeks for a year and a half, even in the winter. We couldn't measure the poor water in the winter because it froze, but we measure our methane fluxes for an entire year every three weeks. So we have data from the winter from Marsh organ, which is fun. Again, we hypothesize that our freshwater marsh would have greater methane emissions than our brackish marsh. That heating would increase those methane emissions, and that our lowest elevation site would have higher methane emissions than our higher elevation. And so just to get you kind of situated with my graphs before we start getting into the data on this graph, on the y axis, we have our methane flux. On the x axis, we have our vegetation, whether it's fair or vegetated. Again, our brackish sites is always going to stay on the left, and our freshwater sites is going to stay on the right. And then our colors represent season. So light green is spring, dark green is summer, fall is purple and winter is pink. And so like we predicted, we found that the freshwater site had higher methane emissions in the Bracy site, ten times higher. It's pretty crazy because the salinities don't vary that much between the sites like zero to three to about ten parts per thousand. It doesn't seem like a huge to me coming from working in 30 parts per thousand. It doesn't seem huge. But for methane batters. And then for our vegetated treatments had higher methane emissions that our bare treatments, which we would expect because there's a carbon source there from the plants. And our methane emissions were highest in the summer and fall. So for the rest of the talk, I'm going to show you mostly summer data. So what happens when we add in those heating and elevation stressors? So at our brackish site, we really saw what we would have expected. So we saw that heating increased methane emissions and that our lowest elevations or most inundated pots had higher methane emissions than our lowest elevation pots. So our highest elevation or lowest sorry. Highest elevation pots have lower methane emissions than our lowest bent pots, which had the highest. Anyway, so these are most inundated in dark orange, and then the light orange is least inundated. And so in our heated on the left. And so we thought, Okay, brackish site is what we expect. But then we go to our freshwater site and we see this impact of elevation, but not really the impact of heating. There's a few things that could happen there. We either have maybe different processes occurring for producing that methane. We're working in pots, so maybe we have carbon limitation occurring. Maybe our pots are just blowing through the carbon that they're using. Or maybe we have different redox conditions at our sites, which also has to do with different processes that same production processes occurring. So first, we looked at our redox data. And again, and so we have heated pots on this graph, we have heated pots on the left, ambient on the right, and our brackish is green, freshwater is orange. And so redox is reduction oxidation potential, higher redox, the more oxidizing it is, the lower, the more reducing. And you're probably like why are your redox numbers so high? This is normal for a marked organ, right? Because it's in a stream. It's not surrounded by other sediments. So these pots do get a little bit more, aerobic or a little bit more aerobic than you would see on the marsh. Yeah. So but we didn't really see that big of a difference between our sites in terms of redock. Our heated pots had slightly higher reduction oxidation potential, but it was not a statistically significant difference. And we did see this pattern with elevation, where our lowest elevation had the lowest redox, so it was more reducing. Makes sense. But that doesn't really explain why we didn't see a difference with heating at the freshwater site. So then we wanted to look at our biomass. Maybe we had we had relationships with biomass. And so this kind could get at that carbon limitation. So at our brackish site, we saw that there was a positive relationship between our methane flux and our above ground biomass. But we didn't see that relationship at the freshwater site. So that kind of indicates to me that there's carbon limitation occurring in those pots. Because really with more biomass, we should be seeing a relationship there because there should be more carbon in the soils. But yeah, to actually get at this question, what's happening, we performed an incubation experiment. And to perform this incubation experiment, we really wanted to look at these different substrates for bethanmissions. With the soils from marsh organs. And just to orient you here, we spiked our sediments in our incubation with different substrates for methane emission. So acetate to look at acetoclastic methanogenesis, CO two and H two mixture, to look at hydrogenatropic methanogenesis, control. And then we also looked at two different substrates to for methylatrophic methanogens, methanol and methylamine. And again, brackish on the left, Freshwater is on the right. They're also colored. And so We found, again, that our freshwater rates were higher than our freshwater methane production rates were higher than our brackish. And you can see that by looking at the y axis, our y axis on our brackish goes up to three PPM per gram per hour for methane or for freshwater goes up to 20. So we do have much higher rates at the freshwater site. Our heated rates at both sites were higher. So which we didn't see in the field. So that indicates to me that there was probably a carbon limitation occurring because we're giving all of these vials, the soil, the same amount of carbon. And we also saw that methanol had the highest methane production potential, indicating that we potentially have methylotrophic methanogenesis dominating if we have the substrate there. And so we also again, want to look at elevation, so we zoomed in our graphs. To get a chance to look at that elevation gradient. And you can see that at the freshwater site, there's very clear higher elevation has lower methane emissions. Yeah higher elevation has lower methane emissions and the most inundated have high methane emissions. Methane production, no matter the substrate. And then at our brackish site. The two lower elevation treatments have higher methane emissions than our lowest or highest elevation. So we're really seeing similar patterns to what we saw in the field for our brackish site, and our freshwater site, we're seeing the same patterns that we saw on our brachisit, indicating to me that there was probably carbon limitation in our pots, which makes sense to me. We had an insane amount of biomass. I should've put a picture of what the roots looked like when I We cut the pots in half. We had to use a sawsol, and it took forever to cut through all of the shooplects rhizomes. So those said rhizomes that we were we had the pots was insane. Yes, our highest methane production was in soils from the lowest elevation. Heating and sea level is should really increase these methane production methane production via all of these pathways. Is what we found. In conclusion for this part, this marsh organ, these two little experiments for the marsh organs. In the field, both heating and sea level rise, increased methane emission. From the brat site, but there was no impact of heating at the freshwater site. But in the lab, we did see an impact of heating. That indicates that we had substrate limitation in the field. And when we don't have substrate limitation, it seems that methylotropic methanogenesis will dominate. Now we've looked at these longer term impacts of climate change. Let's get into these shorter episodic events. Our main question for this was what mechanisms control hot moments of methane emissions in coastal wetlands. Before we get into the experiment, I just want to go over what hot moments are. Because even when I'm talking about hot moments in biogeochemistry, sometimes I confuse them with episodic events. Hot moments are defined as times that show disproportionately high reaction rates relative to longer intervening time periods. In orange here, we have a big increase in our methane flux. That would be a hot moment. And so episodic events are the short term changes in our environment. So like a heat wave in this image from Aokial 2021 shows a marine heat wave in the Virginia Coastal bays in this red area. We also see a lot of hurricanes in coastal areas, and Hurricanes can do a variety of things coastal ecosystems. So one of the things they can do is they can decrease the scalinity. And so this data from Hurricane Harvey shows that as precipitation increased during Hurricane Harvey, Galveston Bay freshened. So the scity of Galveston Bay went 30-0 part than. And then During hurricanes, you can also get the opposite occurring. You can also have a salinity increase due to storm surge. So this is an image from Hurricane Barry, Louisiana. And so before the hurricane, this freshwater wetland was green and beautiful and doing well. During the hurricane, there was a storm surge that hit this area and increased the salinity to greater than four parts thousand. And then one week after this hurricane, this wetland died or the plants in the Wetland died because they couldn't take the salinity increase. You can also see increases in nitrogen loading with hurricanes. This is another image from this is another study from Hurricane Harvey that shows in read here that we had an increasing ammonium and nitrate concentrations during and immediately after landfall. So H hurricanes can have really large impacts on these things that can change the biogeochemistry of our systems. And so we really wanted to dig into these things a little bit more. And so we built this mesocasm experiment or this mesocasm facility, at sir. The new facility, if anybody ever wants to use it, besides me. So we dug in all of these basically big barrels of PVC to use as our outer musicosms. And we basically made the rest of the experiment modular. So you can change around the configuration of where these chambers are, where all the infrastructure is in this area. Which is pretty fun. Anyway, So we performed six experiments during summer 2024 to look at the singular and then the singular impacts of inundation and salinity shifts, warming and nitrogen loading. Then we also did double crosses, which talk about a little bit. So We used different pots of plants for each of these six experiments because weren't looking at repeated events. We were just trying to get at what happens with one event to start for our models. You can see that over time, our music cousins got emptied from this is when we started. This was like our final experiment of the summer. And we built these automated flux chambers at SRC. We used linear actuators to get this automated b lid. And then within each chamber, we had a fan a BME, which measures air temperature, humidity and pressure, and then our sampling tubes, which were connected to likewise in and out sampling tubes, so we're putting air back in. Then we built this. We had our cores in a shed basically, our methane CO two and then our nitroxide core, and all of these control boxes which are fun to build. Then we built our own proprietary manifold, and that's because we found that the LGR manifolds not good for this. If anybody wants to talk about that later, happy to. So that we could have better control over flushing of our lines. And so again, we performed these six experiments during Summer 2024, where we did a flooding experiment, P N experiment, nitrogen loading, and then we crossed them. And so during our experiment, these were very short experiments. We were really just looking at the immediate impacts of these stressors. And so we did a pretreatment, which was three days. Then we treated treated our plants with our stressor, and then had a post treatment of three days. And during this time, we were continuously measuring our methane, CO two and nitrosoxide emissions, continuously measuring redox, continuously measuring soil temperatures and air temperatures. And we also took pore water samples during each period. So pretreatment, post treatment, and then biomass before and after. Which is a lot of different things, but very fun. And so before I actually talk about the data, I just wanted to get you oriented because these are a lot of factors to look at all at once. And so on the diagonal, we have our singular factors. This is like a grid. And then over here, we have double crosses. And then when we're talking about flooding treatments, our control is always going to be this green color. No matter the treatment. For flooding treatments, brackish is blue. Fresh is yellow, and Poly Halen is red. We started with a brackish ten parts per thousand water salinity in all of the experiments. All right. So for CO two, we didn't really see any differences, but these are all the CO two data combined. I just got finished. Well, just did the first analysis of the data like this past week. So this is all hot off the presses data. We don't really see anything with CO two, and we'll talk about that a little bit more later. But for methane, we didn't see any impact of our individual stressors. And we didn't really see any impact of our in addition by flooding in our addition by flooding experiment. So this is our pre treatment during treatment and post treatment. But when we double cross. So when we add when we did warming by flooding, we started to see increases in our methane fluxes. So we had this period where we were just warming the pots because we had to give it them time to warm up. We couldn't just warm them instantaneously. Now once they were at the right temperature, we flooded them as well. So as soon as we had our warming and flooding, we saw that our control again in green lowest. Our brackish flood, so we went from negative 5 centimeters, so 5 centimeters below the sediment surface to 5 centimeters above. We saw a slight increase in our methane flux. And then with our fresh, which was zero parts per thousand addition and our polyhalen, which is a 25 parts per thousand addition, we saw even more increase in our methane emissions. So we're starting to see the impact of these dressers. And it's not really what we would have expected, right? We would have expected that when we add salt to your water, we should have lower methane emissions. But that's not really what we saw here. And so we did we also saw differences in our warming by in addition. And so that really increased O warming by in addition, which is this is the treatment period in center. We saw an increase in methane emissions during that period as well, which is pretty interesting to think about. O in addition was ammonium. So we can talk a little bit more about why that might be b. And really, warming has a stronger impact on our methane fluxes when it's combined with another stressor and these short in these episodic event experiments. So far, we've found the episodic events do not cause hot moments of daily CO two fluxes. But really, we need to separate out our CO two fluxes by day at night to see if there are any impact, so that's the next step for CO two flux. Hopefully, we'll have that for AGU. You can see that there really is this big diurnal, like we would expect plants, this big diurnal change in our CO two with lower during the day, higher at night. So we also found that warming has a stronger impact on meth in fluxes when combined with another stressor. We also want to separate out our methane flexes because we said before, we found that G crew, that we did have diurnal variability in our methane fluxes. So we'd expect to see that in this experiment as well. We're using the same types of plants. So we should see that same type of diurnal variability. And then our NTO data I analyzed, and there was literally nothing. And so there was an issue in our source code that was taking the data from the experiment and putting it into a file that then I could use. So I have to go back and fix that. Fun, so I don't have that to show you today. But we also have a bunch of nitrogen data from our poor water samples that we took, and I know that we had nitrogen there, so we should have nitrosoxide. Great. So future work. So next summer, we're continuing this experiment. We're going to learn from some of our mistakes and also add in triple crosses. So we can really get at like, what's happening when a hurricane hits? We can't really simulate our wind situation. But we can simulate the storm surge. The storm surge and freshening, we can simulate that nitrogen loading, and we can simulate a heat wave occurring at the same time. So we're going to work on our triple crosses and then do some top tracing lab incubations with the soil from these experiments. So that we can then input some rates of these reactions in our models. And then hopefully come up with new questions that we can use for our next experiments. And so overall, we found that both long term and short term climate stressors have impacts on our methane emissions from coastal wetlands, and the interacting impacts of these stressors are really important to consider when we're modeling these climate stressor impacts on coastal wetlands biogeochemistry. I'll also help us predict where our wetlands will be at in the future in terms of their carbon budgets. And so with that? I would like to acknowledge all my collaborators, my funding sources, and then everybody that's helped a circ with this project. It's a truly a team effort. And thank you all for coming. Start with the question here I guess. Thanks. Let's talk. I've never seen the Marsh Organ. I actually seems really cool. But did you have to build that yourself could you build that and then next thing. Brown. How much money at to do you all get? A lot of our funding comes from the Department of Energy. So the two grants that funded those projects also actually built. Sorry. This experiment on our Marsh. This auto chamber experiment was actually built by the first experiment by the first DOE grant we had, as well as these auto chambers. We're built by the first DOE grant we had along with the Marsh Oregan experiment. So we had the infrastructure there. One good thing about working at CRC is that we have a lot of infrastructure. So I had to build the int to go into the Marsh organ, like, plop that in, which was fun. So a lot of my post has been building construction. But it's been fun to learn how to construct these type of experiments. Yeah. So with your March organ, I was asking because I wanted to make sure you not make sure, but just know how much water is actually getting through all of them. You said it was like an open system. So if you have the below 10 centimeters at zero and then above, that's the same amount of water. It's all of them. Do you all make sure of all of that, or are you depending on the tide cycles to act as like natural cycles for how much water is? So we're depending on the tidal cycle to act as a natural cycle. So some days obviously are drier than others. And that's why we tried to measure every three weeks so we could catch different tidal cycles throughout the time over that year and a half that we measured? And so yeah, that's kind of the cool thing about marsh organs is that you put them in a stream. So like I said, it changes the reduction oxidation potential. So it kind of increases it because you're in a stream, which is there's oxygen all around. Whereas in the marsh, there's hardly any oxygen just coming from the plants. That water brings in fresh oxygen, it raises your redox potential a little bit or raises it a lot, really. But in general, the patterns that we see are similar to the patterns that we're seeing in the marsh, so we can kind of then use these data and models to help us figure out what could be happening in the marsh. Okay. Do you have any idea of the oxygen penetration depths of any of these? So I took so I don't know the exact oxygen penetration depths, but there are there were holes So they're holes on the bottom of the marsh organs at the bottom of the organs, even though they're buried in the sediment. So these are 60 centimeter organs, and the bottom most. Row is buried pretty deep in the sediment, and there was a lot of sedimentation around this freshwater one, especially. Like, I had to dig them out, dig out the sediment before I started, and I dug out maybe like two, three like meter. Sediment to put them in, and then they filled back in. During the year and a half, which is pretty fun. So that's kind of a limit not great thing about these experiments. But yeah. So I to get at your question, Water penetrated from the both the top and likely from the bottom. So water coming in from the bottom was probably anoxic. But the water coming in from the top of the organs was probably aerobic. So I'm not exactly sure of the oxygen penetration depth, but I did do peepers on the side of the organs. Which you can see the peepers anywhere. So these arms I put peepers into like here. So we basically sealed the paper in for a few weeks. And with the DI water, and then we pull them out after a few weeks and measure the water oxygen, we'll measure poor water constituents as well, like as oxygen. So at the beginning of our experiment, we did have high oxygen concentrations in our poor water. And then over time, those went down to zero. So I'm not sure of the oxygen penetration depth. But I do know it got used up eventually as soon as our organs were established, which is why we ran it for so long, rig is supposed to run for three months. But there were too many potting effects to, like, actually see to have good data, so we ran it longer. Yes. Thanks for a nice presentation and congratulations for your experimental set because I imagine a lot of work to put everything together. It's amazing the way. My question is very basic because sometimes we struggle to define the salt level for freshwater. Really like to son better how to plasi the pacts, I play 0-3 0-6, Yeah. That's a hard one. Actually, because yeah, freshwater, freshwater biogeochemist wouldn't classify the system as a freshwater system. But in terms of the marshes that we work at that the labs that I working at Circ work at, this is one of the on the fresher side because it is zero to three parts than. So When we were deciding where to do this, a lot of it just had to do with where we could build something like this and really the only place in the area we could build something like this was on Sirk campus. So this is the freshest part of the stream that we could get to on Sirk campus. So that kind of dictated where we could go. But we still saw big differences in our two sites, and there are big differences in our plant communities in our actual plant communities at the sites. So this area is not actually shown a plects dominated the area around this or the freshwater marsh organ is not shown a plects dominated. You can see here, all this rag. At one point in time, apparently, it had some shoo plects, but now it's mostly frag dominated in this system. And then our Marsha G crew has frag and Iva and Shooplects, and spartana Patons. So it's pretty diverse plant community. So we really wanted to stay in the range for Shoo plects because the exp the auto chamber experiment, which is the sister experiment to this one, the one on the Marsh, not the one that use the cosm experiments. Um is the Shona plects dominated area on G crew Marsh. We also wanted to stick with that plant. And it is a plant that can go lower in salinity, but not too too much higher in salinity. So yeah, there are a lot of reasons why we defined it as freshwater and why we used that salinity. Yeah. This is also like a super basic question. I'm not very well versed with Modoc at all. But I know we're experiencing like a drought right now. Do you think that's impacting any of the processes that you spoke about through like ity changes or changes in nitrogen infuds? I don't know. Definitely, you can definitely see drought when you're measuring greenhouse gas concentrations and streams in tidal areas. So for methane, you would expect when you have a drought for your methane fluxes to get lower, right? Because you have a saltar system. There's less organic carbon being flushed into your system from your marshals, even though you still have that tidal variability, there's less rainfall happening. So yeah, you would expect for methane at least for those emissions to decline during a drought. Yeah. Thank you. Yes. That was a really great talk. Thank you. I have a kind this is a long recommended question. Because we had some undergrads over the summer or at least mylan, I head an undergrad in this summer that did some incubations of marsh mud with some of the same carbon additions that you did. And we got results that were different from your. So I wanted to ask you what you thought might have been related to the difference or caused the difference. So what we did was we took Marsh creek sediment, so there was no vegetation in there and out here, it's polyhalne, and we have spartana alternative rather than rose. But we also found methyltropic methanogenesis was the only thing that was really going on and methylamine was really the only carbon futate that was causing methane production. So you saw methanol. Mm hm. Well, that is a hard question. So I know other subtidal studies have found the same thing that you found. And I think maybe that because you use subtidal sediments, that's potentially why. We did take all the plant like all the rhizomes and as many large roots as we could out of our soil before we incubated it just because Some of the shown a plectterisomes can be like gigantic and wouldn't fit into our incubation bottle, so we just decided to take them out. And it would just made our data easier to look at anyway. So yeah, I'm not really sure at this point. So that's kind of why I want to I'm not really sure why methanol was higher than methylamine because I expected also to see methylamine, but I'm also coming from a subtidal background. I know that in other Marsh studies or yeah. In some mangrove studies. There's a mangrove study from a while ago that found that methanol was highest as well. So it could have to do maybe with the tidal variability, maybe it has to do with the variability and salinity or like that oxic and oxic interface. Changing. But yeah, I'm not sure. Nick, do you have you have to ask how long your incubations ran? So these were 72 hour incubations, yes. Word. That's right. Yeah. 30 days. Okay. Yeah. These were pretty short as well. I wonder short, long term. Could be. The thing that we fed them was pretty much consumed in the first 15 days. Just kind of let them go for longer. I was wondering whether it's a plant like what are the plants feeding the like what kind of organic carbon is going into the anoxic part of the sediment, and is that driving which methanogens? Are there? Because the methanogens are free subs substrate specific. Yeah. I haven't had a chance to actually look at the organic carbon constituents in the in the sediments yet that we have. So that could be it. We have, DOC from our poor water, and we have organic better content from our soils, but we didn't get into the actual sub amount of substrate in the soil. That's kind of like next steps for this new experiment we're working on hopefully. Interesting puzzle though. Dell, along that line. So when you first showed your model, right? You said, like, Oh, we're measuring acet H two CO two. But you did not mention anything about methylated compounds, but yet, you know, you definitely proved that they're really impactful. Yes. So there any thought about incorporating them back in the model? Yes. So that's one of the things that I've I've been super interested in methyl methyltrophic methanogenesis for a long time, like, since I learned about me like methyltrophic methanogenesis during my PhD. Wow, that's really cool. I think it's really important in plants or in vegetated systems. So that is something that now Terry and Alex, the post doc that's working on the P flo trans side of this project are starting to incorporate into the model, because, yes, that model only included acetoclastic and hydrogen trophic methanogenesis to start. So those are part of the next steps, but in order to get at better rates, we need to do more hope tracing. Let me see if there's a question from New York. Man. Yes. So I'm trying to get a sense of how big these combined defects are across all the channels that you've shown meta for climate change? Do you have a sense of, you know, later in the century, when we have an extra one degree of warming and 28 30 centimeters of sea level rise, for your cruces, is this, you know, 10% of methane. So 50%, what are we talking about? So I haven't calculated that out yet, but that is something that I'm going to do soon. So based on what we saw for G crew, if we just look at the brackish sites, which are go back. We just look at the brackish site from G crew. So we kind of, like, maxed out our warming based on that he, whatever climate change. Yeah. Based on the highest at of CO two, we could release into the atmosphere. And so with our sea level rise, we really could only go like, 1 centimeter of sea level rise is, like, basically relative sea level rise from Maryland in a year, the rate of relative sea level rise from Maryland in a year, which is crazy. But so We could really only get at ten years in the future for sea level rise, but we could go to a crazy long way for warming or docentry, in the worst scenario for warming. It's a little hard to predict. I need to think about the data more and probably work with the modelers more to get at a more realistic rate of warming and sea level rise for the same time period would be for methane for changing our methane emissions. Does that make sense? Thank you. Yeah. So one of the reasons why we chose you're probably like, why did you choose these temperatures is because we wanted to be able to compare this experiment to the experiment on the marsh. And so when they built that automated chamber experiment on the marsh, it's a warming experiment. So in the experiment, they go from six degree or ambient to six degree Celsius warming over heating field in the soil. And so we wanted these data to be comparable. But we could only really have plants survive. At that ten centimeter level below. Otherwise, we would just killed all our plants and would have seen nothing. Yeah. Yes. So how do your rates of methane compare to the plots? I mean, not the plots. The Yeah, your field data. The field data from Gene. Yeah. So our rates are actually lower, and that's because of that change that redo. We had a lot higher redox in the Marsh organ. So when we're thinking about Marsh organ experiments, also, we have to consider that. So what we're hoping to do with this Marsh organ experiment and the field data are to be able to put both of those into our model and kind of figure it out from there. I'm not well versed in the modeling side, but Terry and Alex have a way of kind of reducing the redox in this experiment and seeing how our rates will change based on that. Sorry. You're bring you back. So I'll study micros in sediment. I'm trying not to be biased. But is there any future insight for, what these microbes look like during your incubations or with next incubations, especially that can help answer the question of if your organs are doing some form of aerobic methanogenesis very early on and then switching to anaerobic methanogenesis. So Most methanogenesis is anaerobic. There's like a paper that just came out that shows aerobic methagenesis, which is kind of fun to think about. But again, it's one paper that just came out, so I don't know. But typically, methanogenesis is like what we know about metho anaerobic process. So what we saw early on in our Mrsorgans and why we continued the experiment for longer was that we didn't really have very high methane emissions. Our plants were still, like, getting situated in the organs reduction oxidation potential for the first, like month and a half was all over the place. And so we didn't really start to see redox gradients from the surface of the soil down to the 20 centimeters as deep as we want for redox. Until a month and a half after we put the marsh organs in. So in terms of what microbes are there, and like, what they're actually doing, like, if we wanted to do like transcript obi, we don't have like, we don't have any data on what microbes are there at this point. We didn't take any samples, any microbial samples. But what we can say is that we did have a time when things were still establishing. And then after that establishment period is the data that I'm showing you. And and yeah. So I think that the soils were anaerobic or they were anaerobic. I know that they were anaerobic because the poor water is anaerobic. But I do think that some of them had longer periods of being of, like, maybe hypoxic conditions than others. So like the lower elevation or the higher elevation, sorry, the least inundated had probably longer time periods of being hypo hypoxic and dry than those lower elevations, where we would have, like, probably more anoxic conditions occurring. Okay. So more methanogenesis? Yeah. Any other questions? Thank you, Al. Thank you.
Alia Al-Haj - SMSP Fall Seminar Series 2024
From Taylor Link November 08, 2024
2 plays
2
0 comments
0
You unliked the media.
Alia Al-Haj
Postdoctoral Fellow
Smithsonian Environmental Research Center
November 8, 2024, 12:00 PM
Cannon 202 and via ITV in Robinson 206
Hosted by Nicholas Ray
Abstract: Vegetated coastal ecosystems (e.g., seagrasses, marshes, and mangroves) play a key role in C and N cycling at the terrestrial aquatic interface and can help to mitigate global change by storing C in their soils and filtering N out of water. However, the same characteristics that cause vegetated coastal ecosystems to have high C sequestration rates and high N removal rates (e.g., saturated soils and variable salinity) can also lead to methane (CH4) and nitrous oxide (N2O) emissions. In fact, vegetated coastal ecosystems were identified as the largest source of uncertainty in the global CH4 budget and contribute to both naturally- and anthropogenically-derived N2O emissions. Vegetated coastal ecosystems are also subject to both longer term, climate-change driven stressors, such as warming and sea level rise, and more episodic stressors, such as changes in inundation, salinity, temperature, and nitrogen (N) loading, caused by heat waves and hurricanes. These stressors can alter greenhouse gas (GHG) emissions and can have a disproportionate effect on the annual GHG budget in vegetated coastal ecosystems. We will discuss the interactive impact of multiple short-term stressors and multiple longer-term stressors on GHG emissions from coastal marshes using several mesocosm experiments as case studies.
Zoom Recording ID: 99179954296 UUID: 019GHduGSHiMYBmt1qNxLw== Meeting Time: 2024-11-08 04:29:46pmGMT
- Tags
- Department Name
- School of Marine Science and Policy
- Appears In
Link to Media Page
Loading