Researchers Dr. Leila Kittu, Dr.Giulia Faucher, and Dr. Charly Moras discuss Ocean Alk-Align’s global research of OAE safety

In this episode of Plan Sea, hosts Anna Madlener and Wil Burns sit down with researchers Dr. Leila Kittu, Dr. Giulia Faucher, and Dr. Charly Moras to discuss the latest updates from the Ocean Alk-Align consortium’s exploration of ocean alkalinity enhancement’s (OAE) environmental safety and efficiency. Representing expertise from the GEOMAR Helmholtz Centre for Ocean Research and the University of Hamburg, Leila, Giulia, and Charly join Anna and Wil to share valuable insights on what’s needed for monitoring, reporting, and verification (MRV) and environmental safety assessments.

Ocean Alk-Align is dedicated to evaluating the efficacy and durability of carbon uptake and storage;  environmental safety and potential co-benefits; and MRV requirements of various OAE approaches. Leila, Giulia, and Charly discuss how understanding OAE’s efficiency — commonly measured by how many tons of carbon dioxide is removed per ton of material added to the ocean — is incredibly nuanced. The group’s research suggests we must also consider factors such as dilution, sinking, and horizontal mixing when discussing the efficiency of various OAE approaches in different real-world settings.

To evaluate OAE’s environmental safety and better understand how scientists can protect living ecosystems without sacrificing efficiency, Leila, Giulia, and Charly discuss mesocosm experiments that were conducted. The team gradually included multiple species of plankton to identify how biological life responds to seawater changes. Mesocosm research is advantageous for breaking down complex problems into manageable pieces — but is limited in terms of scale, duration, and ability to capture higher trophic levels.

Looking ahead, the group called for more robust frameworks for environmental safety assessment and thresholds as OAE projects move towards field research. The group argues that the broader benefit of carbon removal seeks to outweigh the potential risk of interfering in delicate ocean environments, and requires careful consideration and standardization across these frameworks. Ocean Alk-Align’s work aims to provide a scientifically-rigorous, informed pathway to weighing this “give and take” decision.

Plan Sea is a semi-weekly podcast exploring ocean-based climate solutions, brought to you by the Carbon to Sea Initiative and the American University Institute for Responsible Carbon Removal.

ACRONYMS/CONCEPTS:

• OAE: ocean alkalinity enhancement
• MRV: monitoring, reporting, and verification
• mCDR: marine carbon dioxide removal
• OAE-PIIP: Ocean Alkalinity Enhancement Pelagic Impact Intercomparison Project

Plan Sea is a semi-weekly podcast exploring ocean-based climate solutions, brought to you by the Carbon to Sea Initiative & the American University Institute for Responsible Carbon Removal.

Transcript

00:13: Welcome & What Ocean AlkAlign Studies

Wil (00:13): Hello and welcome to a new episode of the Plan C Ocean Interventions to Address Climate Change podcast. As always, I'm your host, Will Burns. I'm co-executive director of the Institute for Responsible Carbon Removal at American University. And I'm joined by my co-host, Anna Madlener, who is senior manager for MRV at the Carbon to Sea Initiative. Hi, Anna. 

Anna (00:33): Hi Wil. Good morning. 

Wil (00:35): So today we're focusing on how to study the environmental safety and efficiency of ocean alkalinity enhancement through the lens of the Ocean AlkAlign Research Consortium, which is a research project designed to investigate the efficiency and durability, environmental safety, and monitoring, reporting, and verification requirements of ocean alkalinity enhancements. We're joined in today's episode by three postdoctoral researchers from the consortium. Leila Kittu, Giulia Faucher, and Charly Moras, who are all engaged in laboratory and mesocosm studies of ocean alkalinity enhancement. Together, we're hoping to unpack how to design good environmental studies, what mesocosm experiments can tell us and what they can't tell us, and which processes really drive how much carbon the ocean can lock away and for how long. What are you looking forward to in the episode, Anna? 

Anna (1:32):  I'm very excited to talk to these three fantastic researchers. I had the pleasure of meeting a number of them before we actually visited the research site in Kiel last fall. And one of the things that stood out to me was that that's something we talk about a lot and reference a lot in other episodes, the fact that there is foundational research or that there is evidence from mesocosm studies that, you know, something is true or not true in OAE, and I think that many people don't know what it takes necessarily to conduct a mesocosm experiment, what that might even be. And so I'm really looking forward to unpacking those mechanistic aspects of this foundational research. And yeah, we should also say that it's just a subset of the AlkAlign. It's a research project conducted at five different institutions. So this is just a small glimpse, but a mighty glimpse into all of the work that they're doing. How about you Wil? 

Wil (2:36): Yeah, I'm interested in unpacking the role of mesocosm studies also in more detail than we have in the past. And I'm interested in determining whether the researchers found substantial differences in organism responses across the test regions that they were focused on and what the implications of that might be for wide-scale deployment of OAE in the future. 

Anna (2:59): Cool. All right, shall we bring them in to discuss more of that? 

03:03: Meet the Researchers & Inside AlkAlign

Wil (3:03): Sounds great. So let's start with introductions and we'll start with Giulia. And could you also introduce the AlkAlign project a bit for us? 

Giulia (3:19): Yes, first of all, thank you very much for inviting us. I think we are all very happy to share our research. My name is Giulia Faucher. I am a postdoc at GEOMAR, which is an ocean institute in Germany based in Kiel, so on the Baltic. And my research is focused, I mean, I might say that I am a phytoplankton lover. So this is the core of my research. And in ocean alkalinity enhancement, I mainly try to assess how to apply ocean alkaline enhancement in the safest way possible for the ecosystem. And yes, I'm part of Ocean AlkAlign. I'm also a Marie Curie fellow with part of my work. And Ocean AlkAlign is an international project where different groups work together. We are coming from not only different countries, but different continents. So the lead person is Katja Fennell from the Dalhousie University in Canada, but there are other groups in Tasmania, in Australia, in Germany. And we try to work at different levels looking at efficiency, but also durability of ocean alginate enhancement, environmental impact and also MRV. So we kind of work together at different levels to try to find a way to fight to reply to the question if OAE is actually possible to be applied and to be deployed at a larger scale. 

Charly (4:59): Yeah, hi, everyone. Thanks, Anna, thanks, Wil, for having us today. I'm Chary Moras. I'm a postdoctoral research associate at the University of Hamburg in Germany, so kind of a neighbor of where Giulia is working as of now. And I completed my PhD about two years ago now in Australia, where I worked on ocean air quality enhancement and the dissolution of different materials, basically for the carbon dioxide removal strategy. And since I moved to Hamburg, we've been working a lot on dissolution of materials, understanding how to apply oceanic energy enhancement, trying to understand thresholds and see basically how feasible it is from a carbonate chemistry point of view. And of course, we had the opportunity to collaborate a lot with Giulia, Leila and the greater group at the GEOMAR on several field campaigns. 

Leila (5:58):  Hi everyone, hi Anna, hi Wil. Thanks so much for having us. Just a little bit about myself. My name is Leila Kittu and I am a researcher, specifically a marine biogeochemist at GEOMAR Helmholtz Center for Ocean Research in Germany. And yeah, I'm here today because for the past two years, I have been working on. environmental impacts of ocean ecology enhancement, and I'm excited for this discussion. Thank you. 

06:30: How to Design Environmental Safety Research for OAE

Anna (6:30): Great, thanks for the introductions. We're super excited to have you all here. And Leila, I wanna kick it off with a bit of a high level philosophical question, I suppose. We often talk about this concept of environmental safety of ocean alkalinity enhancement. And I'm wondering if you want to share broadly how you approach the design of research around this topic. 

Leila (6:53): Yeah, thanks. Thanks so much for the question. I think so, when we think about environmental safety and how to design experiments, we have to go back to the fundamental question, which is the basic idea of what ocean alkalinity enhancement exactly is. And so when we think about designing experiments, I first of all have to say that the ocean is huge, and it's incredibly complex. And oceanic alkalinity enhancement will probably operate on scales we've never tested before. So the way we tackle this is we try to break down the concept of alkalinity into manageable pieces, at least from an ecological perspective. And we really simply start by asking, if we add alkalinity, what changes? What actually changes in seawater? So things like pH increase or the concentration of CO2 or carbon dioxide decreases in some cases, and so we actually change the seawater carbon chemistry, and therefore we expect that marine organisms will react to these changes. So that's the basic idea. We need to understand what alkalinity actually does to seawater, and so, we design the experiments at multiple scales and in our work we've mostly used a phased approach. That means we start small in the lab where we have everything controlled and we test or simulate different minerals, for example, which are relevant for the application of alkalinity enhancement. And then we start by testing at individual levels. So that means, for example, how single species or a specific process like calcification will actually respond to ocean alkalinity enhancement. And the idea of using this phased approach is that when we start at a small scale we gain a mechanistic understanding of what specific organisms are sensitive or at what concentrations those impacts are actually seen. And then once we understand the basics we start to move on small complex setups such as microcosms or mesocosms. So, microcosms are just a little bit smaller. You have about 60 meters of water while mesocosms are much, much larger. And the idea here is that we start to include multiple species. So we go from a single species to multiple species, where we try to catch or watch how communities or plankton communities will actually respond to sea water changes. And at each step, we set clear questions and measurable endpoints. What I mean is that that might be things like species abundances, which is an endpoint. So we manipulate the seawater and we see how do those abundances actually change, or how do the growth of certain species actually change? And that tells us whether the system is actually being impacted or not. So one important feature of our experiment so far, what we've done in our experimental design. We've tried to use alkalinity gradients. That is, we start from low doses to actually very high doses so that we can see not just if things are changing, but when they start to change. And that's really important. And that helps us to identify things like thresholds or nonlinear responses that we might not be able to capture in the real world. So in a nutshell, studying environmental safety in OAE is really about breaking down the problem into manageable pieces and then scaling up step by step. 

Anna (10:35): That's super interesting, I love that, thank you. You already alluded to it, but I wonder if you want to share a little bit more about specific hypotheses that sort of guided your research the past four or five years. And you mentioned, for example, that you anticipate that there's perhaps varying levels of alkalinity where varying species start to change. Curious if you want to share a bit more about those hypotheses. 

Leila (11:01): Yeah, so we've started doing research on ocean alkalinity enhancements. I think we're about four years in, if I'm not mistaken. And the key questions that have really shaped our research, there are many, but they really come from trying to understand not just if biology responds to ocean alkalinity enhancement, but how and under what conditions. And so if I would highlight, for example, a few questions with our hypothesis that have to research. The first one, it's quite simple, but it opens a very huge door, and that is how biology responds when we increase alkalinity, and whether it matters how that alkalinity is actually increased. So we have two scenarios that we've studied so far, which are using an equilibrated alkaline solution. That means basically that the alkaline solution has actually equilibrated with the atmosphere. Versus if you would add alkalinity solution that has not equilibrated, so the intended CO2 has not actually been taken up. And so those two scenarios, for example, are things that could inform us about the environmental safety of how we should apply alkalinity in a safe way. And that's because in real OAE scenarios sometimes the added alkalinity will mix much slowly, meaning the water might temporarily experience a really high pH or carbonate chemistry shift. And it's important to understand how organisms react. And maybe the second question that we've also tackled is, are any of these biological responses, for example, predictable? And in other words, is there a clear, for example, are there clear thresholds where we start seeing changes, or do organisms actually adapt or recover once conditions kind of go back to optimal? So these are some of the questions that we've currently tackled. 

Anna (13:05): And somewhat related to that, when you do see changes in a system, how do you decide whether to call it an impact? You know, an impact can be positive or negative. So I'm curious, how do you categorize or analyze these responses? 

Leila (13:22): Yeah, that's the fundamental question of our research, right? Trying to decipher, is what we see really an impact? Does it really make sense from an ecological perspective or not? And we go about it by thinking in different ways. So one is that we ask simple questions like, is this change actually caused by the alkalinity addition, right. And to discern this, we employ different tools. For example, we look at controls. So controls are basically the same experiments where we didn't change alkalinity. We also, as I said earlier, we've used in most cases alkalinity gradients. And so we check along that gradient to see whether the response scales with the treatment of alkalinity that we've actually applied. And if the change doesn't track the gradient or actually we also see a similar response in the controls, then it's more that it's not an OAE effect and there's some other confounding variables, right? The second step is also the magnitude of the change, right? How big is the change that we see in a second plankton community and also how persistent is that change? And this is because some responses are actually very small and they're actually within like natural variability. So one needs to be careful about calling those impacts because you actually need to quantify that change in a certain response, you know? But if a change is large or it's consistent across the gradient that we are looking at, or even persists after certain conditions, then we start to think of it as a potential impact, right? And we start to dig deeper into it. The other aspect is about characterizing the change. So you might have things like, is it a direct impact of the alkalinity treatment that we've added? And this has to do with not just their alkalinity but several components of the seawater chemistry that we change, things like pH that are actually changing or concentration of CO2 that might be relevant for phytoplankton, for example. And so we start to characterize those changes as direct if they are directly reducing things like growth or they could also be indirect in a case where a phytoplankton is actually impacted directly but because it's eaten by a zooplankton and we actually see that the plankton is affected somehow because they're eating a phytoplankton that is also affected, then that would constitute an indirect impact, right? So those are the kind of ways that we try to decipher what is really an impact and what is not. So it's really about the magnitude, but also the ecological application of it. Does it really matter for the ecosystem? 

Anna (16:12): Awesome, thank you so much for that overview. I'm sure we could dive deeper endlessly, but I want to hand it over to Wil to share more about and ask more about the mesocosms. 

16:19:  Mesocosms’ Usefulness & Limits 

Wil (16:19): So Giulia, why are mesocosms particularly useful for OAE research compared with, say, purely lab work or field trials? 

Giulia (16:30): I mean, I would say that mesocosms are experimental enclosures, but they are the most similar ones we can get to compared to a natural system, because they are deployed in the water, so they have very similar light conditions, temperature conditions, and then we enclose a natural community. And they are very useful. Because we look at, we enclose a community like an almost not disturbed plant and community and we can look at different levels in the trophic level. We can look at the interaction from microbes up to with the very, very large mesocosm up to the fish larvae, so the highest trophic levels. And we look at how the ecosystem responds to the perturbation induced by ocean alkalinity enhancement, but also if the system is able to, how resilient the system is. And as Leila mentioned before, somehow we can also look at if, you know, one change that we see at the very beginning of the experiment goes on, or if it's just transient, and if there is some kind of compensation. So they're really a perfect tool for gaining lots of information at different trophic levels and how these interact one with each other. And also I would say that in this time where it's quite hard to get a permit for doing field trials, the mesocosms are, you know, of course we follow some rules and protocols, but they are very safe because this is just water that is enclosed in these bags. But this water that we manipulate is not in contact with the water mass outside. So it's very safe. And therefore we just have to be careful when we finish the experiment to follow the protocol to release this water, but we are not modifying anything outside. And then it's also true that these studies are for an institute, they are quite expensive but so we spend lots of our resources for performing this experiment. But they are definitely much cheaper compared to field trials.

Wil (19:10): And what's the flip side of this? What are the main limitations of these studies? What can't they tell us? 

Giulia (19:19): Of course, since they are enclosures, by definition, we cannot gain information about mixing and dilution. So this is the main difference compared to field experiments. And as Leila said before, we normally work with gradients. So we have a control and then we have progressive increase in alkalinity. This is how, in the last year, we are doing our experimental design. And so we use gradients to somehow identify when we see some changes. But it's not like looking at dilution and mixing. And it's a very stable system, since we enclosed this water mass for some time, so with the offshore mesocosm our experiments last two months or so, and with the onshore mesocosm around one month. Sometimes you can get away from reality because it's the same body of water that you're looking at, so maybe some processes are enhanced because of that, because the zooplankton is there, is eating the same phytoplanktons and maybe in a natural context they will have a chance to move around and so on. So this, I guess, is the main limitation of the mesocosm. But you have to consider that it's an experimental setup. It's not what is happening naturally in nature. So, it's a compromise that we have to take into account. 

21:08: Efficiency Drivers and What Really Controls CO₂ Removal

Anna (21:08): Yeah, and a really important compromise on the way to a field trial, right? [It’s a] very important groundstone to lay. I want to shift from the environmental safety to the efficiency aspect of mesocosm studies. And Charly, this is obviously your arena. Before we dive a bit deeper into your work, specifically with the AlkAlign group, I wonder if you can lay out the main efficiency drivers of OAE. So the, you know, big levers that matter for how much carbon is actually removed on , more physical and chemical level.

Charly (21:47):  Thanks, Anna. Yeah, I mean, it's good because it follows a little bit with what Giulia was discussing about the mesocosms and the limitations compared to open oceans. I mean currently the concept of efficiency mostly stems from the amount of CO2 removed per amount of material added basically. Like everyone is interested in how many tons of CO2 is removed per ton of material. And this is, I think, the general understanding of what efficiency stands for. But with all the work that has gone into OAE over the past five years, there's more concepts and ideas that came out about efficiency and that goes from – I mean, there's different groups of efficiency, let's put it that way. Where mainly loss of efficiency we will talk about in the way that it's not just about how much material has been added, but rather how much of the material that has been added, the alkalinity that is being generated, remains in contact with the atmosphere for capture. And in those pathways, we have, of course, everything that has to do with the material that may not be pure, might be only, you know, 99, 98%, which means that it also will decrease that overall efficiency. Then you run into the situation where you put it in the ocean, you wonder whether it actually has fully dissolved. Did it actually, for whatever reason, thermodynamically only dissolve at 90%? So you lose already a bit of potential. You have the sinking problem, which is something that we don't have in the mesocosm because they are closed. That's why I was like, it's a cool link. Then you run into the other thing where talking about dilution and horizontal mixing or subduction, it's all about how long does that alkaline energy stay in the surface to basically exchange with the CO2 and capture that CO2. Then you have that last efficiency that was basically most of what we've done over the past few years, which is understanding what we now frame as the stability of alkalinity, which is does it stay dissolved in water or is it lost to secondary mineral precipitation, for example. So it's not just anymore, like I have added one ton of whatever material and I'm expecting one ton of CO2 captured. It is actually, I have done that in an ideal scenario would be one ton. But realistically what is happening and there's different little pathways of efficiency losses. Let's put it that way. 

Anna (24:10): Great, and so in your work with the mesocosms, what have you been looking at so far? 

Charly (24:16): Well, so the past few years, like the mesocosm, we mostly look at the role of different materials or how different materials could have an effect on living organisms, essentially. And more recently, over the past two years, we've been interested in actually using solid feedstock. So it really started with not a safe approach, but we used an equilibrated approach, liquid feedstocks, which are easy to manipulate, easy to mix, and there are very few things that can go wrong in the way that whenever you're going to add one kilogram of feedstock, you will have most likely one kilogram of alkalinity generation if it is a one-to-one ratio. Over the past two years, basically, the last two mesocosm campaigns, we're looking at solid feedstock. So you bring into that dimension, into that context, the dimension of sinking and the dimension of potential precipitation, like that formation of secondary mineral phases. So it is always present when we have liquid or solid, but it's true that over the past few years, that's what we've been looking at, whether, you know, when we've expected, I don't know, like, that 10 grams would have made a difference. Maybe we only measure that actually seven grams made the difference. And trying to understand where are those missing points going, basically. 

Anna (25:33): Super interesting. Sort of in that vein, over the past few years, was there anything that has surprised you about these efficiency drivers, either from the models perhaps that you've been working with as well, or from the experiments themselves? 

Charly (25:47): I mean, from a personal point of view, the one thing that really surprised me was that secondary mineral precipitation, because when we started our PhD - because we started at the same time with Leila about - the literature available by the way was quite limited and was mostly modeling studies that were very like encouraging, had tremendous numbers of carbon capture potential, it was really exciting stuff. But no one really ever put like the rock in the water and just assumed that things were happening there. And so one surprise was that actually it's not as easy as just pouring particles in the ocean. There's a whole dimension to it, which is, does it dissolve? Does it sink? Does it co-precipitate? And what's happening? So that was probably the most surprising aspect of it. 

Anna (26:35):  And how do you then connect what you see in the mesocosm studies to the real world application of OAE and the design of field trials potentially as well? Is there anything that really stood out to you so far where you thought, oh, I want to make sure that everybody knows about this because it's relevant for the non-mesocosom implementation? 

Charly (26:58): Yeah. I mean, I've always seen it where you have, you know, the difference in between a lab scale study and a mesocosm study is quite similar to what a mesocosm is to a field trial. At the end of the day, it's essentially just, I mean I should not downgrade mesocosm to that, but it's just basically one big beaker that we put in situ and instead of having it in a water bath, we have the ocean. So it is a very similar approach. And so it was quite interesting because the research that we did, so we were quite lucky to be invited by the GEOMAR team to join them on mesocosms, especially like, for example, the University of Hamburg or the group I work with has been invited since 2021. And the field research that we did early on kind of helped later on design the next mesocosm study. So what we saw on the side experiments while they were doing mesocosm study led to basically designing the next one. So I can clearly see that link that is happening on one way from lab scale to mesocosm scale. So I definitely see the link from mesocosm scale to field trials as well. And what is nice is that what we see in the lab is less likely to happen in a mesocosm already, given that we have dilution, we have a lot of interactions with biology that makes a big difference. So most of the processes that we see in the lab are less likely to happen, you know, in mesocosm experiments, which also hint towards the fact that what we would see in a mesocosm is less likely to happen in a field trial, because you bring that dimension of, you know, horizontal vertical mixing CO2 exchange that would be potentially higher because there's wall around the ocean. So that's basically the kind of the flow that I've always seen and that kind of makes the extrapolation or basically like the thinking of how they link together quite interesting. 

Anna (28:42): Yeah, I can imagine also that if something doesn't happen in a mesocosm study, would you say that you can be safe to assume that it won't happen in the field trial and sort of the opposite?

Charly (28:53): Yeah, or you would say that it would be less likely to happen, unlikely to happen, I would say. I don't, I never want to say yes or no, because who knows, but realistically it's unlikely to happen. Like I mean, we've seen it also with the bigger mesocosms where we actually have some more room to do stuff, at least the effects that we see in ones are not the same than the smaller ones. And that could potentially be because it's more concentrated as well, the same way we see when we have an experiment run in a small beaker compared to a big beaker, there's like this pressure of the vessel and the environment that is different. So it is easy to think that what we see in the mesocosms is less likely to happen in the open ocean. 

Anna (29:36): Has there been, I guess I'm sort of rephrasing my previous question a bit, but have there been any sort of early conclusions or indicators for specific feedstocks, taller feedstock that you've added where you can sort of already draw some conclusions, or where you have some hypotheses for how they should be applied in field trials or should not be applied and field trials?

Charly (30:01):  I mean, an easy answer would be yes. I don't want to get anyone on my back for stanning for one feedstock over the other, but it's true that it all comes to how you implement it, right? So one feedstock may be suitable for a coastal application, but won't be suitable for open ocean. I can think of any feedstock that takes longer to dissolve than it takes to sink, should not be considered for open-ocean. The same with the other way around, where if there is a feedstock, that, I don't know, that could be a lot of turbidity, may not be considered in a place too concentrated or a basin, but probably somewhere where the turbidity can be diluted quickly. And there's been a lot of research with plenty of feedstock, I can think, just in my case I probably studied already like eight, six, seven different ones. So that gives already a big, broad spectrum of feedstocks. And overall, the one that comes back the most often, let's put it that way, would be mostly hydroxide. So anything that has to do with sodium hydroxide, calcium hydroxide and magnesium hydroxide which are fast dissolving, which means that they're probably suitable for open ocean. One could consider also in a coastal setting or in a reactor with a discharge, the slurry and so on. And they've been the ones that are the more understood and considered as of now. 

Anna (31:18): Yeah, very, very interesting. I think it's going to be valuable to see more outcomes from that. We, in our previous episode, talked with Phil Renforth and Mijndert Van der Spek about their lifecycle assessment and technoeconomic assessment framework, and anecdotally, I think we mentioned in that episode that they identified 54 variations of OAE pathways, right? Like from point of addition, method of addition type of feedstock and there was one other category that I forget now, but you're already alluding to something similar, right? There's so many considerations about where and how to do OAE if we want to do it. And so, yeah, very curious to hear more about those outcomes eventually. 

32:02: Key Findings So Far & Why Location/Season Matters

Wil (32:02): Let's circle back a bit and talk about some of the environmental findings from these studies. So Giulia, looking back over roughly the last five years, what are some of the main insights on the environmental safety of OAE that you've gleaned from the last five mesocosm campaigns? 

Giulia (32:21): I think there are three things that I learned in the last experiment which I think is already quite a lot. First of all, the first experiment that our group at GEOMAR has done was in Gran Canaria in 2021. And as someone mentioned before, it was an equilibrated ocean alkalinity enhancement approach. So we introduce inside our mesocosm a solution that was already equilibrated. And therefore the organisms were not subjected to extreme carbonate chemistry conditions in terms of pH or they were not experiencing CO2 limitations. And in this experiment what came out from the paper that has been already published is that there's almost no impact or very limited impact on the organisms for a very short time, so it's quite promising. Let's say that an equilibrated OAE approach should not be negative for the ecosystem, and this, I think, is the first lesson. The second lesson is a bit more complicated, and we learned that there are many differences when you perform an experiment in terms of location and time. So it matters a lot, depending on the environmental conditions, like temperature, for example, or the community, of course, that is enclosed in our experiment. The outcome could be different. But it's not only that. Last year, within the project Ocean AlkAlign, our group performed three experiments in Kiel, so here at home somehow, at three different seasons, one in spring, one in summer, and one in autumn. We are still looking at the data, but the idea was to apply the same experimental design in different conditions that were different conditions of nutrients, for example. The natural cycle here in Kiel, we have high nutrient in spring and then low nutrient in summer and in autumn before the nutrients are coming back again. And the temperature was, of course, very different in spring. The water temperature was around six degrees and then it was much higher in summer but also in autumn. And we apply the same experimental design and we expect to obtain very similar results. They're awesome. I'm not going to say much about it, because as I said, we are still looking at the data. But it's kind of, you know, something important to keep in mind that it is not that if you apply the same approach in different locations or at different time, the outcome is going to be the same. And then the third thing that I learned, it's about higher trophic levels. Because nowadays there's lots of initiative towards looking at higher trophic level, fish for example, fish in particular, and they are new studies and new, as I said, initiative. But I think that this comes from one of our mesocosm studies that we did in Bergen in 2022. And there is this paper by one of our colleagues, Silvan Goldenberg in 2024, in which for the first time he's talking about fish, because we introduced in our mesocosm fish larvae. And before that, all the research was, you know, in the direction of phytoplankton up to zooplanktons. So it was really the first time that someone kind of said, hey, we should also consider higher trophic levels because it's not only about the low ones. So I think these are the three main lessons that I learned in the last five years. 

Wil (36:55): Yeah, I think that focus on higher trophic levels is going to be extremely important, obviously, for a lot of stakeholders, right, that might ultimately be engaged in determining whether we move forward. So that's very interesting. What makes this mesocosm work in this context of environmental impacts particularly challenging? Is it about endpoints or the higher trophic levels that we talked about or time scales? What creates kind of intrinsic, if there are intrinsic, limitations to the kind of conclusions that you can draw about environmental impacts? 

Giulia (37:35): I mean, higher trophic level for sure, because you can add, as I said, fish larvae inside our mesocosms only, by the way, on the large one. So the one that contains around 30 to 60 cubic meters of water, so the offshore mesocosms. But it's still limited, right? Because it's fish larva, it's always very complicated. There's always lots of big question marks about if it's going to work or not. So there are different set ups that should be used, which are not the mesocosm, to understand what is also the physiological response of fish. Is it a matter of change in pH or presence of particles in the water or anything else? So for sure, for higher trophic levels mesocosm can be not enough. And then I would say that with the mesocosms, the mesocosm can give us information about short-term or middle-term responses because they cannot last too long, because we have a certain volume and also because it's just the same volume of water. So, you know, you're just looking at the same thing somehow. So the small mesocosm, the experiment, they last around a month. With the big one you can go up to two months maybe. And so you can just gain information about short or middle term. And then if you want to understand if OAE might impact an ecosystem on a longer term, you have to think about different approaches. So these, I think, are the two main limitations. 

39:20: OAEPIIP & What’s Next for MRV and Risk Frameworks

Anna (39:20): That's a very important point, I think, again, similarly to Charlie pointing to the fact that we need to always transition between these different stages and you're learning important things that will then sort of inform the next one. I want to work it back one scale actually in the opposite direction and talk about the OAE PIIP exercises that Leila, you are currently running. You are in Kenya, as we speak, running experiments linked to the OAE PIIP exercise, which listeners may actually remember from our episode with Tyler Cyroneck and Lydia Kapsenberg. He briefly introduced these. Do you want to quickly share more about what you're doing and how these experiments fit into the broader picture here? 

Leila (40:05): Yeah, I can do that. So maybe just shortly, OAE PIIP stands for Ocean Alkalinity Enhancement Pelagic Impact Intercomparison Project. And it's basically a globally coordinated research effort to study how natural plankton communities respond when seawater quality is actually increased, so similar to oceanic quality enhancement, right? And this global project, shortly OAE PIIP, we are about 17 research groups participating. And we are distributed actually in all continents, which is a really great effort on this side. And each participating research group conducts basically the same experiment in their own local environments, following a common protocol, right? And so the project, what we use is a standardized microcosm unit, which is a 60 liter seawater tank, simply, that encloses a natural plankton community. And each group basically adds the same amount of alkalinity under controlled conditions and then measures the same suit of responses in plankton and in seawater. So it's really an experiment that is tackling the ecological aspect of OAE. And the idea is that these individual studies, once we are all done, can later be combined into sort of our global synthesis that we hope can hopefully reveal patterns that are consistent across different regions or even across different plankton communities. And this is especially important because we are moving away from relying on single experiments in one place isolated in one location. And apart from the fact that it's meant to build the scientific consensus about the potential ecological impacts of OAE because the experiments are relatively cheap and they're also very simple, the project is also trying to basically promote participation from scientists worldwide by also building expertise and supporting inclusive research from diverse economic backgrounds or even geographical backgrounds in places where OAE research has not actually started yet. So, for example, as you alluded to, Anna, I'm currently in Kenya to conduct this experiment with colleagues from the Marine Institute here in Kenya. And it's very exciting because I also get to transfer the knowledge, but also we help to establish a new area of research here with the hope that once I leave, they are able to tailor their own OAE research to locally important questions on the applicability of OAE, for example, African waters, which is a very big open question currently. So OAE PIIP is really an amazing research effort that tries to  bring together all the scientists to understand ecological aspects of OAE.

Anna (43:26): That's really cool, especially because both Charly and Giulia also alluded to the fact that you learned how important different locations are, right? And that the reactions or impacts can vary quite significantly in different places. So very, very cool to hear that this is an experiment that tries to sort of find the underlying joint sort of drivers. Do you see other areas where such tangible, scalable and accessible experiments could play a role in your research next, or across the field of OAE generally?

Leila (43:59): Yeah, I mean, so as much as OAE PIIP is really related to OAE, I think it's also creating a template for how we can actually rapidly assess emerging technologies and environmental changes in the ocean before we can deploy at scale. And that's actually the kind of proactive science that we need at this moment. Because it's really powerful for tackling globally relevant environmental questions. So the most obvious extension of such models of experiments would be, for example, I can think of using the same model to other marine CDR approaches, so other carbon dioxide removal approaches that are actually still in their early stages. I think we would all benefit from having globally coordinated research efforts to actually speed up our understanding. But we can also use this, and I think it's something that we need to start thinking about, is looking at combined stresses and that's because OAE it will not happen in isolation or in some cases it might not be deployed in a pristine ocean, because climate change is still ongoing, and so there is a regulatory need or relevance. Therefore, if we're making decisions about OAEl deployment, regulators would need to know, will this be safe in a warming or acidifying ocean? And not just is it safe today in controlled lab conditions, right? So we need to test interventions under conditions that they'll actually face and that is a changing stressed ocean. I think such globally coordinated efforts would be good to integrate other stressors to create some kind of ecosystem predictive capacity, so to say, for real-world applications of marine carbon  dioxide removal technologies. 

Wil (46:07): That's really interesting and yet another layer of complication, of course, but I think a really important aspect of this. You're all spread across institutions and disciplines. How do you make sure that results from one group within the consortium actually reach and influence what others are doing? And do you have any concrete examples of that? 

Giulia (46:35): Maybe I can reply to that, and maybe the others can say also something else. I think that the mesocosm experiments are really one of the places where we discuss the most, because you have to consider that during this experiment we are around 40 people between technicians, scientists, and students that are helping us. I think that Anna, you've been there last year in Kiel and you've seen that, you know, it's really a big group of people working together. And because we spend so much time in the lab and outside, it's a perfect moment where we can discuss the data and we can reply to some of the questions because there are people who are experts in carbonate chemistry and I can ask a question about it and vice versa. So it's really the moment where we kind of discuss the most and decide the most. And also, we use the expertise of each other to also design our experiments. We were talking actually yesterday about this podcast and Leila was mentioning that she remembers when we were in Helgeland during an experiment a few years ago. And we designed our experiment after some tests that a PhD student from Hamburg University, so from Charly’s group, he did some tests on the carbonate chemistry, he found out some threshold values for precipitation, and then we discussed it, and then, we designed our experiment. So, I think that, of course, it's not only during mesocosm experiments, but this is really the time where different expertise are coming together and we are able to find the time to decide how to proceed and what is needed in the consortium. And everyone can participate because, you know, there are longer experiments and there's room for everyone to reply to their own questions, so this is a good example. 

Charly (48:43): Yeah, and actually what was funny is that I actually joined the first mesocosm in 2022 in Bergen, where I was still a PhD student in Australia at the time. I didn't know anything about, well, I never been to Germany before, I've never been to Norway before, so that was kind of a first for me. I had to learn to communicate in German with a couple of colleagues from the GEOMAR, which was fun. And it actually opened a lot of opportunities workwise, because I actually met then my current boss there, and that's how I got to exchange with them and we got to design all the way that we're doing now on top of that, given that Giulia and I are like technically neighbors because we're like 45 minutes an hour away. I mean, of course we discussed data, but also it opened a lot of doors for friendship in our case. And that was quite nice to have that kind of opportunity to be able to, and that proximity. And it's true like Giulia was saying that you have so many brains in the search, a confined area that, I mean, it is exhausting. It is not denying that, you know, the days are not counted in hours, but just in T1, T2, T3 after addition. So there's no even concept of hours anymore. But it really leads to very proactive research. And yeah, really good conversation and really good ideas that come out of it. 

Anna (50:06): Perfect commercial for going into science and doing field research. 

Giulia (50:10): And Charly, are you Germanized now? You're saying T, because it's tag, not day, you know?. T1, T2, T3... 

Charly (50:20):  No, time point one, time point two, ahhhh! 

Giulia (50:23): No, no, no. This is tag. 

Anna (50:27): Well, I want to wrap it up and close up the episode a bit by talking about the future and how you're adapting your research to potentially a lot of the real world activity that's ramping up around OAE. I mean, you already alluded to, of course, you have that feedback loop sort of within your own consortia, but I'm curious how you think about the value proposition and the speed at which I'm sure people are craving to receive your results. Also, as you see the activity in the real world unfolding. I mean, that's maybe a question for each of you, probably. 

Leila (51:02): Yeah, I can also jump in and I think that's a really important aspect that you bring because the pace of real world OAE interest is definitely going really fast. And we also want our research to stay relevant, but also useful, right, as that happens. And so one way is that we are paying close attention to, for example, discussions on the type of minerals. All the alkaline materials that are actually in discussion to be used, for example, and this is important from an ecological perspective, but also from an efficiency perspective in terms of Charly's work, because these alkaline mineral sources are associated with their onset of other conditions that have, on one hand, ecological relevance, but also efficiency, right? And then the other aspect is we try to stay very much connected with a broader OAE community. So projects like OAE PIIP or even ocean alkalinity, where we have, you know, sort of say monthly meetings, for example, they also help us align our experiments with actually what is being discussed or tested in field pilot studies, for example. And that way the data that we produce are not just academically interesting. But they also directly inform environmental risk assessments, for example, from a regulatory perspective or monitoring aspects and things like best practices for responsible research. So in short, I think we try to adapt by keeping our experiments realistic, by testing relevant materials and conditions and making sure that our work fits directly into the global conversation about safety and effectiveness. 

Charly (52:54): Yeah, and it's quite interesting to have seen the shift, like we were discussing. It started kind of with modeling and then a couple of experiments that started with olivine-rich materials like dunite and so on in very specific experimental design that shifted towards different materials, calcium hydroxide, magnesium hydroxide. Lately, there's been a little bit of a focus on industry byproducts as well, steel slag and kiln dust. So there's been a lot of shift and this shift is happening. I don't know how much it would have happened in other contexts, but it's true that in the context of OAE, it changes very fast. It is undeniably a sexy topic as of now. So a lot of people are putting a lot of energy, a lot of effort into it. So it brings a lot of research and a lot of focus. So, it's quite interesting to see how the momentum is shifting every year, essentially, from this type of material to that type of material to this type of phytoplankton and that type of zooplanktons. And now we're even discussing, like there's been recently a couple of field trials by colleagues of the Carbon to Sea Initiative. So it's really nice to see such a shift in that whole research and it's quite encouraging in the way that you have really smart brains sitting together on one great solution or this one great approach which is quite interesting to see. 

Anna (54:14): Okay, well, alluded to that one last question from each of you. I'm curious to hear your sort of go-to favorite R&D question that you really hope to see answered next, either your personal one or have someone else answer it. 

Leila (54:32): Maybe I'll try to link it directly to the ecological aspect, because I think this is something that we don't talk about often. And I think we need better frameworks for risk assessments and also defining acceptable impacts thresholds from an ecological perspective. And this is because, I mean, we need to know how much ecological change is actually acceptable, with how much carbon that has been removed, right? And who decides that? We need to develop these frameworks, I think, in partnership with stakeholders or things like indigenous communities and the broader public. And I think when we start understanding how these frameworks can actually help, I think science can inform a lot of decisions, better decisions for society. But we know that science cannot make those decisions alone, so we need a community to actually help us figure out these frameworks for risk assessment. And I would like to see more R&D going into those frameworks. 

Giulia (55:40):  If I can maybe add to that, I mean, there's MRV, Monitoring, Reporting, and Verification. It's quite a complicated topic already. But I would like to see an E in front of that, so to consider also the environmental impact into that. It is, you know, I think it's a direction of many discussions. But I think it's also quite important to consider. I don't think it's quite important, it is fundamental to consider that. 

Anna (56:18): Just shortly on that, do you mean more specific targeted monitoring prescriptions or requirements that are sort of bespoke to certain pathways, that sort of go beyond what is currently…?

Giulia (56:37): Yes, exactly. 

Charly (56:39): I mean, and as a follow up, I think the MRV is also quite, I mean it is undeniably a tricky topic given the changing states of the ocean and how much of a difference it can make from, you know, day to night already in terms of measuring CO2 and so on. In my case, because I'm more of a lab person, you have to spend a lot. When we talk about carbon in chemistry, we take the time to take a sample a certain way, to have a measurement that is then really good, but it's something that is really involved. And we don't have the kind of instrumentation to have a quick and easy measurement that is highly reliable or that can pick those small differences that we want to work with. So I think that R&D part has to come into play. I think as of now, we can probably like Leila mentioned, it would be nice to have everyone on the same page and agree on the same approach so that everyone does exactly the same thing in terms of measurements, at least the M part of the MRV is out. So that's one big thing out. We all agree on the same approach. We'll agree on the same number. Everything is inter-comparable and the rest can come. But yeah, unfortunately, if we had the chance to have super high quality instruments in a controlled environment, then we could probably more easily do the MRV task. 

Anna (58:03): I think there's also the challenge of, from the opposite angle or direction to identify the potential parameters that maybe do not require the very expensive, highly accurate, highly detailed measurements that you just described, if there is a sort of agreed upon tested approach, if they're agreed upon sort of list of proxy parameters or so where where you then know if if a change occurs, you have to look deeper into the system. But that link, I agree, is something that is a real challenge and something to look forward to or look into. 

Charly (58:39): Yeah, what I've always wondered, like, I mean, correct me Giulia, and Leila, if I say something wrong, but, you know, we talk about alkalinity and alkalinity, and alkalinity, but realistically the alkalinity is just a concept. It doesn't really do anything to living organisms per se. It's rather what comes with alkalinity addition, which is why when we talk about an equilibrated approach, well, surprisingly, there's little effect because the real part that would become problematic for living organisms is this change in pH, this change of CO2. And so I could even consider not measuring alkalinity at all and just focusing on that pH and CO2. 

Anna (59:17): Which would be great for the environmental aspect, right? But then for the efficiency…Yeah, we have to measure many things. We could probably go on for, for a long time, and we just got to the good part, which is MRV. 

Wil (59:37): Yeah, well that seems like a good place for us to wrap it up. Leila, Giulia and Charlie, thank you very much for this incredibly detailed sort of work. 

Charly (59:50): Yeah, thanks for the time guys. I’m looking forward to our next meeting, and yeah, good luck with the rest.

Giulia (59:56): Thanks so much for having us. It was very, very fun.

Leila (1:00:00): Thanks as well from me. It has been really, really great. 

Wil (1:00:04): Thanks to our listeners. If you enjoyed this episode, please leave a comment or a review and share this episode with others. If you want to suggest a specific topic for a future episode, please feel free to reach out to us through LinkedIn or via our email address, plansea@carbontosea.org And with that, we say thank you and hear you next time. Goodbye all.