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Home My WebLink About2024-03-22-SAC Meeting SummaryNC Nutrient Criteria Development Plan – Scientific Advisory Council (SAC) 3/22/2024 Page 1 of 16 Attendees SAC members in attendance: Hans Paerl (SAC Co-Chair) Jud Kenworthy (SAC Co- Chair) Martin Lebo Lauren Petter Michael O’Driscoll Marcelo Ardon Jim Bowen NCDEQ staff in attendance: Note: may not have captured all DEQ staff in attendance Elizabeth Liebig Paul Wojoski Susie Meadows (note taker) Pam Behm Karen Higgins Charlie Deaton Nora Deamer Mark Vander Borgh Elizabeth Fensin Dan Wiltsie Cam McNutt Chris Ventaloro Tim Ellis Guests in attendance: Anne Coan Clifton Bell Andy McDaniels Doug Durbin Jay Sauber Theodore Lynch SAC meeting facilitator: Paul Wojoski Meeting notes ***All questions, comments and answers are paraphrased*** 1) Convene (Paul Wojoski) • SAC, DWR and guest introductions. • Show agenda, mentioned SAC’s charter of decision-making process. 2) Approval of Minutes (Hans Paerl / Paul Wojoski): • Hans Paerl made a motion to approve the minutes, Jud Kenworthy seconded. The motion passed unanimously. 3) Questions #1 and #2 - Are the EPA recreational criteria magnitudes of 8 µg/L for microcystin and 15 µg/L for cylindrospermopsin appropriate for North Carolina? (Jud Kenworthy / Hans Paerl): • Hans: The 2 values come from EPA’s technical document. Both about microcystin and cylindrospermopsin. My feeling is that I think it is safe to use those values that EPA put out. Want to stress these are for recreational exposures and not drinking waters. I back EPA’s value for microcystin and not as sure about cylindrospermopsin; I know we have issues with it in NC waters. NC Nutrient Criteria Development Plan – Scientific Advisory Council (SAC) 3/22/2024 Page 2 of 16 • Jud: Do we have any monitoring data in NC that we’ve ever exceeded these values? • Mark: We have been monitoring for microcystin for a couple of years now in the Albemarle and the Chowan, but Dan would know. • Dan: We’ve been running samples since about 2017 for microcystin. We have routine lakes monitoring on a 5-year rotating basin schedule, the samplers will collect microcystin samples and we'll run those and any blooms. We’ve had values above 8 µg/l and some lower, but I need to dig through the data. There have been microcystin values way above that 8 µg/l value, like 100 over the past 5-6 years. We have data on other toxins as well. There is no EPA approved method for testing cylindrospermopsin. The methodology that we use is the Eliza method. I do want to quickly point out that DHS has a study that we collaborated with them on last year and we also will be doing it again this year in which they are testing for different toxins across NC besides microcystin and cylindrospermopsin is included. • Marcelo: Going through the notes from the last meeting, in 2021 there are samples from the Chowan with values in the 300’s µg/l (350 µg/L). In 2019, when there was a bloom, microcystin in the area was 620 µg/L. • Hans: Those were probably from Astrid and not DEQ. • Dan: That’s true she did and DEQ also collected samples then as well and I think those values were from DEQ. • Hans: These numbers jump depending on when and where you are sampling. There is a high amount of variability in microcystins, for example I know from other places where I’ve been involved in work on cyano blooms like Lake Erie, Florida, San Francisco, and China we see this. And this is one of the frustrating things about these cyanotoxins is that it’s very difficult to point to any particular causative factor, except for the fact that your trophic systems are more heavily impacted, and you know this gets into the nutrient issue as well. • Nora: Sharing a map from the Chowan River Basin. Values ranged from 620 to 0.44 from 2018-2019. • Hans: Yes, so there is tremendous variability. • Jim: Was a similar plot made for the Chowan? • Hans: The relationship between chl-a and microcystin is pretty good in Tahoe and that’s because Microcystis is such a dominant sign of bacteria in that system. So, you know you’re going get a reasonably good correlation, but it’s not perfect. There are other factors that influence the production of microcystin. You need to have nutrients to support the production of microcystin and in the other papers that were sent around by Libby, nitrogen comes up as being a really important constituent. We don’t know why microcystin are produced. But, maybe to protect NC Nutrient Criteria Development Plan – Scientific Advisory Council (SAC) 3/22/2024 Page 3 of 16 themselves from environmental extremes, including things like excessive UV irradiation, the production of reactive oxygen species which microcystin can neutralize so you know there are just these other factors that control how much microcystin is produced. • Jim: Why not use these values since EPA has recommended them? Lauren are other states using different numbers? • Lauren: Haven’t really looked into it, but I don’t think that other states have chosen different numbers. Some are understaffed and can’t do additional analysis, but EPA put these numbers together as what we think is the base, best available science out there. • Clifton: I don’t think there are other states using different numbers. • Hans: I think California is a little lower at about 5. But, I agree, I think the EPA’s values are good. • Marcelo: I like the why not approach. We spend a lot of time looking at individual waterbodies and EPA’s guideline seems to suggest it for all water bodies, and I was wondering what are your opinions on that? • Hans: These are recreational. Drinking water would be very different. We're talking about the Chowan and Albemarle, which are largely recreational exposure, although there have been poisonings of animals, dogs, for example, and other domestic animals. But I would think, for lakes it's the same number for recreational exposure. • Marcelo: Is it a single exceedance or growing season? • Hans: I think a lot of that has to do with monitoring. • Paul: Responding to Marcelo, the recommendation from EPA is a health exposure scenario based on a criteria for the most susceptible population; children 6-10 years old. Toxicity is developed on a standard equation. Really the question that the division wanted to pose back to this group, is there a reason to doubt the exposure risk? I encourage the group to separate that from the implementation of the criteria. It’s not for all water across the board in all scenarios. This is specific to waters that are classified as recreational. Is there any reason to tweak this with regards to exposure risk and not to compliance. • Lauren: The factsheet that went around does give details for duration and frequency Marcello. And so, I think questions one and two, to me, was do we agree that the numbers for those two toxins are appropriate? And then I think there's a secondary question that we’ll get to which is, should it be a criterion? The fact sheet lays out exactly how you would phrase the details behind that. They could then be used for monitoring or if you choose to go to the NC Nutrient Criteria Development Plan – Scientific Advisory Council (SAC) 3/22/2024 Page 4 of 16 swimming advisory, it has a description for that purpose which would then be implemented for monitoring. So, I think questions one and two are asking if 8 and 15 are appropriate for NC? • Jim: Standards are in total microcystin, is there any info about congeners that would suggest a different limit than 8? • Mark: That kind of research is just being developed. Astrid’s lab is looking at that. But we’re just looking at total microcystin in the State labs. Astrid is finding toxins without blooms, and they can be persistent in the waters so that's why it's really good to measure for both chlorophyll and toxins. • Hans: Good points. Work in China that’s been done, shows that toxins can persist and there have been toxins found over winter in sediments. • Mark: There was a lake in NC where it was in the sediment. • Hans: Setting a threshold level is very important because it allows the monitoring to assess system level issues with toxicity. And EPA’s levels are pretty reasonable. Let me ask another question to Paul. We need to institute some sort of monitoring regularity for these toxins, including the ones in reservoirs that are used for drinking water? • Paul: Agreed for what it’s worth. I recommend that if there’s a form of consensus to make a motion of yes. • Hans: I think it’s good to move ahead with something like that. I know there’s lots of uncertainty with the cylindrospermopsin, but we should vote on it. • Jud: Do you feel this is a precautionary number? Knowing what you know from the limited amount of data there is. • Jay: I think it's very important for you all to remember that EPA is required under the Clean Water Act to develop criteria, but they were very specific when they put forward this criteria in the context of adopting information suitable for establishing advisories, the language in the forward of the document very clearly states that that was the intent of these numbers and the approach. It was debated heavily whether or not EPA would be publishing criteria for the adoption of water quality standards and the science involved in these discussions. We're not pushing this as a water quality standard. What they suggested, in the forward to the document, is this is for advisories which is typically done by county health departments in a different agency altogether than DEQ. They felt very comfortable using this information to provide education to the health assessors and the epidemiologist in the health departments and the county health departments. That would therefore tell the public do or do not go swimming in these areas and then they left it open to the States to decide individually as to whether or not they want to adopt it as water quality standard criteria. So, there were so many NC Nutrient Criteria Development Plan – Scientific Advisory Council (SAC) 3/22/2024 Page 5 of 16 variables in so many issues when all of the public comments were submitted, EPA came back and virtually doubled these advisory levels from what they had previously proposed because there were so many comments on the number of factors that control the actual numbers. I'm not sure if you're voting on whether or not it's appropriate to use these numbers for health advisory decisions or whether it's appropriate to use these numbers for the adoption of water quality standards criteria. I think those are maybe preamble questions to what you're voting on. • Hans: Good points, but I think we are talking about advisories. We’re not going to get very far if we left it up to the individual counties. • Jay: Over the past few decades, the health advisories come from the health departments and not DEQ. • Paul: So, to refocus, we are wanting scientific consensus from our own scientific group to review this. As far as the health exposure risk associated with the EPA's national recommendation and again, I don't want the group to get too bogged down with implementation of that or whether this would come out as specific water quality standard criteria versus swim advisory criteria. So, it's not adopting this kind of criteria for all purposes under the Clean Water Act, meaning water quality standards, a number of them have implemented this through recreational swimming advisory programs. But don’t get bogged down with implementation, but does this EPA recommendation for health risk exposure makes sense for NC? • Hans: We have focus now, which is do we agree with the recommendations of the EPA as it applies to NC and from a scientific consensus perspective? • Elizabeth F: I’ve seen HABs all around the state throughout the year. DHHS has stepped up the past few years with algal toxin testing, but historically, they weren’t doing advisories, so Mark started the toxins program. I think we should keep toxins in the mix. • Mark: I agree with Elizabeth. Through the toxin testing program we can establish what the levels are and how much. • Dan: It’s a good summary. It helps us figure out these locations and where we might expect a higher level. I also want to talk about how we work closely with DHHS on these issues. The EPA has guidelines right now. We unofficially use 8 µg/l microcystin as a guideline and if we have values over that, we can issue a press release. We don’t have authority to issue advisories, but we can let people know where things are in a press release as soon as possible. The bloom is in this area and that we advised the public to avoid those areas. • Hans: Any other comments? NC Nutrient Criteria Development Plan – Scientific Advisory Council (SAC) 3/22/2024 Page 6 of 16 • Jud: Sounds to me that DEQ has a track record of using this number and implementing it, so it seems like what we’ll be doing is voting on endorsing that. They aren’t pulling it out of the sky. We’re scientists giving an endorsement and I feel a lot more comfortable casting a vote. • Hans: I feel comfortable voting on this and sending it forward. The monitoring will be DEQs next step with regard to recreational exposure. Does anyone have an objection? We can say “yay” or “nay.” • Paul: If the group is ready to vote, then I invite everyone to vote yay/nay to EPA’s recommended recreational criteria of 8 µg/l microcystin and 15 µg/L cylindrospermopsin: o Marcelo Arden: yay for both o Jim Bowen: yay for both o Michael O’Driscoll: yay for both o Lauren Petter: yay for both o Jud Kenworthy: yay for both o Hans Paerl: yay for both o Marty Lebo: yay for both 4) Question #3 - What microcystin / cylindrospermopsin criteria levels are appropriate for swimming advisories? (Jud Kenworthy / Hans Paerl) • Hans: Do we need to have a specific advisory for swimming only or I guess the recreational exposure would include anything from fishing and touching the water to swimming in it? • Paul: Yeah, contact and recreational activities on and around the water. This may be more of an open-ended question to capture any kind of thoughts or information around that specific application. Is there anything that we need to consider differently with the swimming advisory or applying this criteria to a swimming advisory approach? • Hans: One thing is when swimming, you might ingest some of the water, so then that might get into the drinking water criteria. • Paul: EPA’s recreational advisories do take into account that type of contact, the swimming contact, recreator swimming in the water, paddling on the water, splashing around the water. That's how they developed that exposure consideration of that risk exposure pathway. • Lauren: Yeah, incidental exposure of water intake is what’s covered and not getting drinking water from it. The phrasing is different from incidental ingestion and drinking water. • Hans: I don’t think we’re proposing it be a water quality criteria. Jay? NC Nutrient Criteria Development Plan – Scientific Advisory Council (SAC) 3/22/2024 Page 7 of 16 • Jay: The purpose of your vote should be very clear to you. • Paul: Process-wise, endorsement of EPA’s national recommendation would have to take a large secondary step of the division actually proposing this and recommending this to our Environmental Management Commission for adoption as specific water quality criteria. It would come under their review and in the public input process before it is actually codified into rule as criteria and the details of that which I don't want to forecast or predict what that would look like because it would be specific to how the standard is proposed. The intent of this question is to capture any comments from the SAC on applying it as a swimming advisory approach as it is or is there other things to consider as we move forward to develop this as a recommendation for our EMC review? • Jay: My only point to your discussion, Hans, was the wording of what you all just voted on. Can it be interpreted by different people for different purposes? It should be clear what you voted on and leaving it uncertain. • Hans: Does anyone feel there is uncertainty? • Jud: Hard for me to distinguish recreational criteria and swimming. Swimming is recreational. • Hans: Lauren clarified that. • Jay: The document that EPA published clearly states the EPA is publishing these recommended values under Clean Water Act 304 A for states to consider as the basis for swimming advisories for notification purposes and recreational waters to protect the public. I mean, I totally agree with that. I do not agree that these numbers should be used for regulatory water quality standards. • Hans/Jud: Yes, the language is for swim advisory and not WQC. • Jud: We should just use that language as a preference or somehow weaving it into the recommendations we made today to be certain that it's clear that they can look at that and say that's what they meant. • Paul: Lauren may want to also comment, but I encourage the SAC members not to focus on the implementation/application, but instead do we get a thumbs up or thumbs down as far as the risk exposure in EPA’s national recommendation? I want to acknowledge that maybe this question about specifically a swim advisory approach was probably poorly posed to the SAC, it was not meant to say that this is a separate and different consideration for questions. Really, it’s wrapped in implementation. • Lauren: Yeah, the science is good and we’re in agreement on that. The fact sheet that went around does highlight that the duration and frequency depend on the application as to whether you’re calling it a criterion or swimming advisory. So, I don't know if it's helpful to at least pull up that fact sheet and just say if there's NC Nutrient Criteria Development Plan – Scientific Advisory Council (SAC) 3/22/2024 Page 8 of 16 any scientific information that the SAC wants to add to help support the State as you go forward with whatever you can based on the recommendations, maybe that's the point to document. • Hans: The numbers can always change as we gather more info on exposure and effects. Maybe that should be put in there, our wording that we agree with the current threshold set by the EPA, but they could change depending on further findings. • Paul: We are charged under the CWA to follow periodic review and that would include the latest science. • Hans: Yeah, when we get more info on congeners. • Mark: Astrid got a grant to study these things over the next 5 years and these questions will be a part of that research. • Hans: The OHHS? • Mark: Yes, for 5 years, $6.9 million, so these questions will be part of the research. • Paul: We don’t need any further discussion on it then on to the next question. • Hans: I don’t have any objections to that. 5) Guided discussion of questions #4 and #5 (#4 - What levels of nitrogen and phosphorus can foster the harmful algal blooms? #5 - What data is needed (or questions to be answered) in order to determine the correlation between harmful algal blooms and nitrogen and phosphorus?) (Paul / Hans / Jud): • Paul: Regarding these questions, #4 is an attempt to get at the SAC’s charge under the nutrient criteria development plan, which is really trying to drill down to the extremely challenging question of numeric nutrient criteria related to nitrogen and phosphorus levels. We recognize that this is a challenging question to answer. So, we're hoping that we can move towards identifying questions that we need to answer or data gaps that we need to fill in order to get to some type of numeric nutrient criteria. • Hans: I sent around a presentation back in November that sort of dealt with historic and what do we know about nutrients. Eutrophication in bloom relationships in the Chowan Albemarle continuum. In a nutshell, I think some of the results that we got back in the early 80s pretty much gave us the same impression that we have now and that is that both nutrients are important in terms of sustaining and, in the case of enhanced loading, accelerating, eutrophication along the entire continuum. But I think that recently, over the last decade or two, it has turned out that experimental work and also some modeling and geometric relationships, pointed to nitrogen being really the key nutrient in terms of being most limiting at most times, and that's because there's already a lot of phosphorus in the system, some of it naturally, some of it that's been loaded in NC Nutrient Criteria Development Plan – Scientific Advisory Council (SAC) 3/22/2024 Page 9 of 16 the system and is now kind of what's called legacy nutrient loading in the system. DWR did a report on the Chowan which was really good and showed this. Right now, the nitrogen loading question is a very important one. Collaborative work that's gone on between NC State, Chris Osburn’s lab and our lab, has pointed out that organic nitrogen is another factor that needs to be considered in terms of the total nitrogen loads that we’re considering in these questions because it's increased, and it has increased pretty significantly in coastal systems in general. It's thought that it's related to a combination of more human disturbance in the watershed, leading to release of organic nitrogen, but also climate change issues like more extreme events washing out, greater amounts of terrestrial material into our waterways. The bottom line is nitrogen ends up being the most limiting nutrient most of the time. Both nutrients are important, but I think there's an increased focus here on nitrogen as we move into the marine environment. The real question here in terms of levels is considering loads that could lead to different levels in the system. Levels is a tricky word because what's there that hasn't been taken up very often like the residual amount of nutrients in the water versus the total amounts of concentrations of nutrients that are in the water itself, including what's already in the algae itself. I’m going to open up this conversation but (1) with somewhat a bit of skepticism, because I think levels depend on what's been used versus what's not been used and what's coming in the system and (2) the levels that affect the growth of algae, are going to be dependent on other factors, particularly the physics of the system, including residence time, mixing, so on. So, I think it's very difficult to come up with numbers that just say, yeah, this level. Yeah, it should be the threshold for the Chowan or Albemarle or even any other estuarine or coastal system that we're going to be considering. I’ll stop there and open it up. • Marty: When you get to the nutrient levels, each system is its own thing. Not easy to get to levels. I am a load person. I go both ways on N & P. • Hans: One thing we have tried to do, and I think Nathan Hall is actually doing some of these on his current research in Albemarle Sound is to do what are called dilution bioassays. In these instead of adding nutrients to see which nutrients stimulate, we dilute the waters to certain levels using a solution that has everything in it except for N & P. (These are done in conjunction with nutrient addition experiments.) You’ll get to a point where chlorophyll production is stopped or inhibited and then add nutrients back. That’s one experiment being done in the Albemarle Sound and lower Chowan. We really need to look at this in terms of different years and under different hydrologic conditions because the NC Nutrient Criteria Development Plan – Scientific Advisory Council (SAC) 3/22/2024 Page 10 of 16 excess of the nutrient that's limiting is going to vary depending on how much it's being diluted in the system to begin with, forcing features such as residence time. • Marty: In the dilution bioassays, do you track the species that emerge with chlorophyll growth in those? • Hans: We do HPLC to separate the diagnostic pigments for different algal groups. • Marty: Do you notice a different effect as you get to dilution where you get less of the blue greens that were present as proliferating? • Hans: Yes, in the summertime when the blue greens tend to be more dominant dilutions definitely reduce their relative biomass, but it can vary and that variability has to do again with physical factors such as temperature, light, residence time. We’re doing this in Lake Erie too and we’re further along, putting together a paper on it where there’s a 40% reduction in phosphorus that’s been mandated for Lake Erie. One thing that makes it a little tricky to interpret is that as you reduce the nutrients and the nutrient concentrations become lower, there are other issues in the phytoplankton like the small guys tend to dominate more relative to the big ones because they have a high surface to volume ratio and can do better under reduced nutrient load and ultimately concentration conditions. But the good thing is that the small bacteria are a lot less problematic than the big ones that formed the blooms. As you reduce nutrients small guys do better under reduced nutrient load. They are useful to be predictive tools. • Marty: How are you separating for assays? • Hans: There are different ways to separate that size. Ion chromatography and tracking the total pool of nitrogen using fluorescence methods that Chris has developed to see what has actually happened to the organic nitrogen. We don't do anything to manipulate it. We just track what's happened with the fluorescent signal from the organic nitrogen sources relative to other nitrogen sources. • Marty: When I was working with the mills, there was a fraction that generally was reactive and stimulatory and then a fraction that was sort of resistant and so there may be different pools within the organic and we obviously have had a boost of organic in the systems across eastern North Carolina. • Hans: How long do you expose the nutrients to the phytoplankton? • Marty: We allowed the bacteria to chew it up and make available since it was a wastewater treatment just as an analog to whether it would be available in the system, usually 30-45 days. • Hans: We’re also working with a chemical engineer who works on landfill leachate that has quite an organic nitrogen component. This is leachate that would come off the landfill site and leach its way down into the receiving waters. They are NC Nutrient Criteria Development Plan – Scientific Advisory Council (SAC) 3/22/2024 Page 11 of 16 required to treat that, but there's quite a bit that actually gets through the treatment. • Marcelo: All is interesting, but in terms of the question we have in front of us, talking about what levels of N & P can foster the harmful algal blooms, right? I feel like you guys have done so much work and you probably have numbers for N & P for algal blooms. Do you think you have numbers for harmful algal blooms? • Hans: That’s tricky because what makes them harmful is food web issues. We have not made those distinctions in our bioassays. • Marcelo: So, based on all the work you guys have done, do you know concentrations or loading numbers for the algal blooms with the assumption that some of those are going to be harmful and some are not? • Hans: Yeah, I think the best we can do on that is come up with data from our experiments in the summertime when the cyanobacterial taxa are more dominant; they tend to do well with reduced nitrogen. The question of levels really bothers me because levels change really fast, maybe loads is a better word to use. But I would say stay tuned on that question, because Nathan’s student is putting together a paper on that. To make absolutely clear, in a dilution experiment we’re offering the natural phytoplankton concentration differences at an instantaneous time. If we reduce the concentrations by X amount, what's the growth potential during that period that we run the bioassay, which is about a week? We did that work in the Neuse a long time ago and that’s why reductions and that info went into the TMDL of the Neuse and it seemed as though that was pretty successful in reducing the blooms in the riverine portion of the system. So, it has been useful using these kind of dilution bioassays, but you have to run them quite often because things change in terms of the levels and loads that are coming into the system. That’s where that 30% reduction came from the Neuse TMDL. • Michael: Loading is a better perspective like light limitation too with nutrients and concentration, but I was curious if we’re thinking microcystin where they talk about it being more sensitive, maybe to salinity. I'm just thinking what your perspective is if you have the same amount of nutrients but in saltier or brackish water versus fresh. If there's issues there if you use a concentration? • Hans: Well, there are going to be differences in terms of the community because some of those bloom forming cyanobacteria that we see in a Chowan River don't make it into Albemarle Sound or at salinities of say, 5 or higher. But there are other ones that actually replace them in the system which can be harmful and produce toxins. A good example is anabena. How do others feel about the load vs levels for DEQ? NC Nutrient Criteria Development Plan – Scientific Advisory Council (SAC) 3/22/2024 Page 12 of 16 • Jud: Have there been any opportunistic studies that have been able to look closely at evolution of a bloom and nutrient dynamics? A sampling regime that allowed the data to reveal a time series of the growth of the bloom and expiration. • Hans: We have those data from the bioassays for over a week or so. When you put phytoplankton in a bottle some algae like to grow in the surface of these containers, some don’t like containers at all and like to move around. You go longer than a week, you run into these other complications. Intensive monitoring would be another approach. At a site where we know blooms are frequent, like in the lower Chowan. DEQ samples monthly in most places. • Jud: We can look at the molar ratios of CNP in the tissue, preferably the leaf tissue, and you know there's been a fairly reasonable estimate of the Redfield ratio, you know under different conditions for vascular plants. So, in the natural environment, looking at the molar ratios of CNP to see what the limiting nutrient might be? • Hans: Yeah, that’s been done. We haven’t routinely done that here, but the issue with ratios is in shallow systems there is so much exchange going on between the sediments in the water column and it’s very difficult to use that as a predictive tool. Because turnover of N&P being really dynamic in shallow systems and I did have a student ages ago who looked at that in the Neuse and we eventually gave up on it because the changes were so dynamic that there wasn't any real long- term trend that you could see that parallel. • Jud: I don't know enough about their Physiology and dynamics and whether anyone had done that. • Hans: Well, the open ocean, of course, you've minimized the sediment water column exchange, so that gets rid of a lot of complications in terms of interpreting the Redfield ratio. • Jud: With vascular plants, of course, they're integrating the environment over a longer period of time. • Hans: Yep. • Marcello: I’m trying to figure out, how do we provide feedback to #4 & #5? • Hans: I propose we really look at load for starters because concentrations are so dynamic. • Marcello: I agree, do we need to make a vote? • Hans: I’d like to hear from others. I’d like to hear arguments both ways. Look at it from the SAV perspective. • Jud: Most of the coastal ecosystem management programs are really addressing this for SAV or are really leaning towards loads and not concentrations. NC Nutrient Criteria Development Plan – Scientific Advisory Council (SAC) 3/22/2024 Page 13 of 16 • Hans: Also, from the management perspective it’s hard to target concentrations. It’s much more direct to target loads. Concentrations vary a lot and loads give you the total amount. • Elizabeth F: Hans, you wrote a bunch of stuff about N & P and toxic cyanobacteria and over the course of your career you’ve answered questions #4 and #5. • Hans: Well, what we were looking for is how much do we need to reduce the loads in order to get below the threshold. I mean, I think that was the question that was asked ages ago in the Neuse. And I remember Bev Perdue at the time, locking us all up in the room in Raleigh and asking what's really important to know here. And we all agreed that we needed to consider reduction in loads and then we came up with that 30% reduction that was based on a combination of modeling and some stochiometric stuff and experimental work. Same thing needs to be done for the Chowan. Early on in the 80’s we recommended reductions of both N & P, the blooms went away and we all patted ourselves on the back and said, we solved this problem and went home, then in the 90’s they came back. We've found out that we need to look at organic forms as well, for example, and maybe other things have changed, including flow and residence time issues that are involved in either promoting or mitigating blooms. And that's a tough one, including flow in this prediction of whether or not the system's going to have a bloom is very difficult to mimic experimentally. • Elizabeth F: Does the council need to come up with actual numbers for N & P? • Hans: Well, I think that there will be more meaningful numbers that will come out of the dilution bioassays that we've been doing. So, you know, we could provide a range of what the nutrient dilution tells us at certain times of the year. Under bloom and non-bloom conditions, but again those are a series of snapshots, but I think they'll be useful in terms of at least starting to come up with some targets. The 30% - 40% reduction seems to come up in many other places, for example in Chesapeake Bay. And the other thing I should mention is the Neuse TMDL. There was also good historic data of how much the loads actually increased over time. • Elizabeth F: Since the 30% reduction came out in the 1990’s, should that be updated now? • Hans: For the Neuse? • Elizabeth F: For anywhere because it seems like 30% is so 1990’s. • Hans: Well, it is and we didn’t consider organic nitrogen. • Marty: On the Neuse, I don’t think we’re attaining the total nitrogen TMDL with the organic coming up. Attaining the 30% would need to be achieved before we would know whether we need to go beyond that because we’re not there yet. Looking at nutrient levels, we need to keep in mind that they provide food for fish. NC Nutrient Criteria Development Plan – Scientific Advisory Council (SAC) 3/22/2024 Page 14 of 16 We have to be careful reducing concentrations and try to restore to a healthy nutrient level. • Michael: I think the loading approach is most appropriate, but I was wondering what people thought of dissolved oxygen impacts when looking at water clarity. But if you get the right loadings for those to be protective enough for HABs, is there a difference? If we worked it out for water clarity is that appropriate for HABs? • Hans: Good question. If you increase clarity, then you might actually increase the potential for some phytoplankton to do better. Especially the ones that are non- modal (can’t come to the surface). But by and large, I think clear conditions do favor HABs. Cyanobacteria can alter their buoyancy depending on the clarity of the water, so they don’t mind it being turbid. • Jud: Based on history of everyone’s experience in the Neuse, what part of the system responded the most? Realizing the 30% might not be enough? • Hans: The 30% hasn’t been reached. But, things improved in the riverine portion and they actually got worse in the estuarine segment of the system. So, pointing to that we need to stay the course and get that 30% reduction in place. But you know, we're going to have to tackle where that organic nitrogen is coming from. • Marty: The TMDL was a late 90’s and early 2000’s, and so from a timing side this success on knocking that down is the phosphorus, putting limits on dischargers and banning phosphorus detergent? • Hans: By reducing P and not N… by reducing one nutrient you solve one problem, but maybe the other one is worse downstream, which was more nitrogen limited and in fact that was one of the major factors for the TMDL for the nitrogen reduction. • Pam: There is a watershed model being developed for the Neuse River basin right now and we hope to have those results later on in the early summer and we're hoping that it might give us some idea on the sources of those organic nitrogen increases. Second, this is more of a question when you're talking about targeting loads and load reductions in the past, those have been when we've developed TMDL's and load reductions, they have been targeted for meeting chlorophyll standard. For example, in this case I don't know that the Chowan is really showing chlorophyll impairment. What would be the instream target that would drive calculating what those load reductions need to be? • Hans: Well, I know we have data, I know we have nutrient addition data that our students have done in the Chowan part of the system. I'd have to look that up to see if dilution biases have been done there, but that would be an obvious thing to do initially. NC Nutrient Criteria Development Plan – Scientific Advisory Council (SAC) 3/22/2024 Page 15 of 16 • Marty: I guess the question Pam, are you really getting around to the regulatory trigger that justifies that kind of management? • Pam: Yeah, pretty much. • Marty: I guess the question would be whether because it's blue green toxins, whether the narrative would be sufficient to justify a load reduction because I don't think a hard and fast number (a concentration) is going to be a very difficult one to get. • Hans: Pam, does Chris Osburn know about this modeling effort? • Pam: Not sure, we have a 300-person stakeholder list, so I'm not sure if he's on there or not, but I can double check. • Hans: If you want to give me the information, I can share that with him. • Pam: I will put the link to what we have so far in the chat: https://www.deq.nc.gov/about/divisions/water-resources/water-planning/modeling-assessment/special-studies#NeuseWatershedModel-12492 • Hans: Anyone have a strong feeling about loads versus concentrations? Or have we convinced everyone that concentrations are too tough to get at? Well, Paul, I think to some extent we made some progress, right. We knocked out the concentration part of that. • Paul: Yeah, I think it's been some really good discussion here and there's a lot that I've got down in our notes and again just to remind the group of where we hope to take this is to document some of this, maybe a white paper or some written documentation. In that paper it would be nice to discuss other factors that would affect the concentrations turning into blooms - things like residence time, temperature, vertical mixing, flushing, salinity, and other physical parameters too. There’s been a lot covered here. • Hans: I think one thing that would be useful is to see if anyone has the ability to track flow conditions in the context of residence time over the years in the Chowan. I think that’s in a report that Nora had. • Nora: Well, the problem being we don't have any flow gauges in the main stem of Chowan River to know how loading has changed. I do want to note that I added a link to the nutrient chapter for the Chowan for folks to go in and look at and you can see we've got several different types of graphs in there that allow you to see the changes in both the nitrate and the organic nitrogen. And looking at it and how they've changed going from the stations from the top of the watershed to the bottom of the watershed. https://edocs.deq.nc.gov/WaterResources/DocView.aspx?dbid=0&id=2707831 So, while loading might be the right response, I'm not sure how we can take the current data and understand how load has changed in the main stem at this point. NC Nutrient Criteria Development Plan – Scientific Advisory Council (SAC) 3/22/2024 Page 16 of 16 (Nora shared her screen to show the chapter and areas where there are gauges.) So, there's not a whole lot of data to make any kind of flow estimates. There's a lot of graphs in here that would give you some ideas of how the nutrients have changed over time. So, I advise you all to go back here if you're interested to really understand what has changed. And again, in the main stem, it's all concentration. • Hans: Well, the closer we can get to some estimate, the better our estimates over time. • Marty: But it may be a water balance on not necessarily a daily basis, but weekly to monthly. Be able to be used with the concentration data. If there's enough of the flow gauges to give that confidence that the engaged areas are represented by prorating. • Hans: Well, I could see another Lebo et al paper coming out of that. I think it's got to be the next step in terms of understanding how loading may have changed over time. I think the other thing to keep in mind is the more extreme events that have occurred, either drought or wet periods. I'm working on a paper with my colleagues at Lake Erie on the application of these dilution bioassays. • Jud: Have we made enough progress to guide us? • Paul: Yeah, absolutely. • Marcello placed a link in the chat about a paper that talks about using remote sensing to estimate: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2023GL105839 • Michael placed a link in the chat: https://waterdata.usgs.gov/nwis/inventory?site_no=02053244&agency_cd=USGS 6) Next Steps (Paul Wojoski) • Paul: Yes, we’ll work with you, Hans and Jud, to document some of the discussion here today specific to these data gaps and these questions that have been asked and trying to whittle down and identify more clearly what kind of questions we need to address and hopefully put together a draft document. And hopefully have this ready for the SAC to review and react to for our final meeting. 7) Closing/Housekeeping Remarks (Paul Wojoski / Hans Paerl) • Next and last scheduled meeting is May 31, 1-4 pm. • SAC would like comments on the next steps of clarity standard. • We are looking at the Middle Cape Fear River next. • We’d like to outline where things are going moving forward. 8) Meeting Adjourned (Paul Wojoski)