[Facilitator] This conference will now be recorded.

[Deana Crouser] All right... Well, good morning, everyone, and welcome to another EcoFOCI Seminar Series. I am Deana Crouser, co-lead of the Seminar Series, with Heather Tabisola. This seminar is part of NOAA's EcoFOCI Bi-annual Seminar Series, focused on the ecosystems of the North Pacific Ocean, Bering Sea, and US Arctic, to improve understanding of ecosystem-dynamics, and applications of that understanding to the management of living marine resources. Since 1986, the Seminar has provided an opportunity for research scientists and practitioners to meet, present, and provoke conversation, on subjects pertaining to Fisheries Oceanography, or regional issues in Alaska's marine ecosystems. Visit the EcoFOCI webpage, for more information, at www.ecofoci.noaa.gov. We sincerely thank you, today, for joining us today, as we continue our all-virtual Series. Look for our speaker-lineup, via the OneNOAA Seminar Series, and on the NOAA/PMEL calendar of events. Did you miss a seminar? Catch up on PMEL's YouTube page, it takes a few weeks to get these posted, but all seminars will be posted. Please check that your microphones are muted, and you're not using video, and, during the talk, please feel free to type your questions into the chat. We'll be monitoring these questions, and we'll address them at the end of the talk. Today, I am pleased to introduce Michael Lomas. He is a senior research scientist, and Director of the National Center for Marine Algae and Microbiota, at the Bigelow Laboratory of Ocean Sciences. As a marine biogeochemist, he has a broad interest in the role that phytoplankton diversity and physiology plays in mediating the key process of the biological carbon-pump, and associated micronutrients, macronutrient cycles. And, with that, let's begin.

[Michael Lomas] Wonderful. Thank you everyone for, for coming out, today, it's great to see, at least, names on boxes, of so many people I know. Aah, come on... Why aren't we advancing? There we go. So, today, I'm gonna talk about Synechococcus, a particular type of phytoplankton that's near and dear to my heart, and it's abundance and biomass patterns in the Bering and the Chukchi Seas, and I hope, by the end of this talk, you start to gain an appreciation for why it's important to understand whether or not this phytoplankton group is, or is not, actually, in these regions. Before I get into the data, I really do need to thank a long list of people. In particular, I wanna give a shout out to Pri, who's on, I saw her name on a box, Priscila Lange. She works at the Department of Meteorology, in Brazil, and has provided some of the slides for this talk, and so, I wanted to, specifically, include her as a co-author, tagline. A huge number of co-authors, over the last 14 or so years, from Cal to Lisa, to folks at UAF, Brad and Seth, and former postdocs of mine, other folks at PMEL, Phyllis, Dave, Carol, and some folks at NC State, plus a lot of other ones I haven't had time to list, as well as funding. So, let's jump into the talk. You know our sub-Arctic and Arctic systems support high-value fisheries, in large part, because, the food chains that exist in these systems efficiently utilize those nutrient inputs, and efficiently channel that carbon and energy to higher trophic levels. Now, there's seasonal patterns, and there's benthic systems, benthic productivities, and water column productivities, and the like, but, the whole goal, of, the reason why these are so efficient, is they are efficient at channeling energy. Part of the way in which that energy is efficiently channeled, is because the chlorophyll, the phytoplankton that grow, go through large seasonal amplitudes, and reach very high levels, and therefore they can support high levels of productivity. This is very different than the open ocean systems, where I spend the other half of my time doing research. When we look at the systems in the sub-Arctic, when we have elevated chlorophyll, we tend to find very high percentages of large diatoms. So, there's this nice positive relationship between total chlorophyll, on the X, and the fraction greater than 20 microns on the Y, going from large diatoms. Now, that being said, it's a line, so, at the other end of the scale, where integrated chlorophyll is lower, you tend to have a greater dominance, by either picophytoplankton, or nanophytoplankton. And, just for context, the Synechococcus data, that I'll show you today... Synechococcus is a picophytoplankton, it's less than two microns. Okay, come on... Come on... Why aren't we movin'? There we go. So... But, what we do know, is that the Arctic is a dynamic, changing system, right? It's warming rapidly, perhaps more rapidly than many other places on Earth, yet we still really don't have a good understanding, yet. That is to say, our understanding of what's gonna be the impact on the lower tropic levels, is still fairly limited. However, we do know that there's different patterns, so, in the... No, that's fine. So, in the, in the Chukchi Sea, when we use model data, the Northern Bering and Chuckchi Seas, we see that the temperature anomaly tends to be more of a longer-term trend, of colder than average, prior to the '70s, or so, and then warmer than average, in the '80s, onward, whereas in the Bering Sea, which is in the bottom panel, there, you can see that it's more of an oscillation, at least, during the record that we have, that I show, here, where the early 2000s are warmer than average, and the later 2000s are colder than average. And, the data I'm gonna show, today, fall in the timeframes outlined by these turquoise-colored boxes. So, our data from the Northern Bering and Chukchi Seas comes from the 2017, '18, '19 timeframe, with one cruise in 2021, which is "hot off the presses", as it were, and our data for the Bering Sea comes from 2008, '09 and '10. Now, why do we think there might be changes, in the lower trophic levels, as a result of these temperature patterns, which are both the global increase, as well as these different patterns in increase? Well, the big reason, is, because other sub-Arctic systems have shown that phytoplankton community-size structure changes in relationship to temperature. So, here's two sets of data, from the published literature. In the middle graph, data from the east and the west North Atlantic, in the range of 43 to 60 degrees north. You can see that on the Y axis, picophytoplankton, so, small things, like Synechococcus, as a percentage of the total phytoplankton biomass, increases positively with temperature, on the X, so much so, that by the time it reaches the maximum temperature of the data set, 80%, or so, of the population is these picophytoplankton. The data on the far right is from the Canadian High Arctic, greater than 70 degrees north, and I've outlined in color codes the real lines I want to draw your attention to. One is, that, for this five-year period, from 2004 to 2008, temperature was increasing. Chlorophyll, in green, here, wasn't changing, so the biomass wasn't changing, but who made up the biomass was changing, and that's this blue line, right here, which represents the picoplankton fraction. So, their absolute abundance is increasing, and changing, therefore, the size structure of the chlorophyll, which isn't changing. So, phytoplankton niche models, right? So, the armchair oceanographers or internet oceanographers, whatever we wish to call them, these days, have tried to make predictions about what the world is gonna look like, 10, 20, 100 years, from now, with regard to phytoplankton size structure, and one of them, one of these models by Flombaum, et al., suggests that the cyanobacteria Synechococcus will increase dramatically, most dramatically, in the equator and the subtropics, but within the polar to sub-polar regions, there seems to be some poleward shift, so extending their range, closer to the geographic poles, and also, at least, within the model constructs, potential for higher abundances. That's what all these, sort of, faded lines are, all the different model runs, that suggest, in some cases, there could actually be a lot more Synechococcus biomass, much shifted, much further poleward. The more recent paper, by Visintini, suggests that, again, looking forward, that the magnitude of this response is dependent upon which climate warming scenario we enable, whether we use the RCP 2.6 or 8.5. But the key part is, is that it's these temperature-related changes seem to be specific to Synechococcus and similar organisms, not all the eukaryotes that do really well at driving energy and carbon into fish. So, there's three questions I wanna take and address, today. One is, is the baseline picophytoplankton community increasing, or changing at all, in the Bering and Chuckchi Seas, as they warm? What are the potential broader implications of this rearrangement of the phytoplankton community size structure? And, a recent addition, is, can we assess or predict these changes at a larger scale, so we can try to better understand how these systems are shifting? So, let's start with, well, how do we actually quantify Synechococcus? For the past 14, or so, years, my lab has been getting samples, or participating on cruises up in the Bering Sea, Chukchi Sea region. We have about 13 cruises worth of data, now. And, on the right, I just show various maps from science reports, showing where we've sampled. So, basically, everywhere, there's a dot, we have at least some samples, at some season. So, it's a pretty extensive data set that we can now start to interrogate, and use for development of novel ideas, which I'll get to, at the end. So, how do we actually do this? Well, the use of a flow cytometer is, as I tell all my undergrads, really it's an expensive laser-lit squirt gun. Expensive, meaning it's more than my house mortgage. But the way this really works, is, you can see that we actually will inject... Oops. If I can get my pointer to work... That we run a sample through a nozzle, and we intersect it with a laser beam. That laser will excite pigments in the cells, those pigments will then fluoresce back some of that absorbed light, and so, by looking at the spectra of the emitted light, and running it through gating schemes, we can, basically, chop up the population that we interrogate into different types of cells. So, for example, in this bottom graphic, here, all cells that absor- All particles will scatter light, so, if we take, and try to separate, those particles that emit chlorophyll fluorescence from those that don't, we can separate living cells from dead cells, within the living cells, we can then go on, and say, well do they have phycoerythrin, which is an orange pigment, and if they do, we can gate them out, and do further analyses on those. So, for example, we can take and separate, by size, cyanobacteria Synechococcus, which is small, and phycoerythrin-containing, from cryptophytes, which are large, and phycoerythrin-containing. For those that don't have phycoerythrin, we can then take, and then, also, structure them by size. And, the result being, is that we can create lots of different populations, within this pico/nano community, phytoplankton community, very quickly. And, as one would expect, the Bering Sea is a lot... Or the Chukchi Sea, as well is a bit messier, with lots of detrital particles kicking around. So, what you can see, here, is bivariate plots, of red fluorescence, or chlorophyll fluorescence, as a function of size, on the left-hand graph, and then orange fluorescence, or phycoerythrin, and size on the right, and I've just drawn gates around how we decide who is who, right? So the red dots are Synechococcus, because they are small, and they have phycoerythrin. Cryptophytes, here, in the blue, are bigger, and also have phycoerythrin. So, that's just an example of what the base data looks like. We, then, take that data, and now we have a count, and we can relate that count to the volume we analyzed, and, then, we can create these interesting maps, of what the cell abundance is, in different places. So I won't bore you with many, many of these, because, they start to blur together, after a little while, but, here's an example of what we, commonly, see the southeast Bering Sea looking like. The top two graphs are section plots, going, on the map, along the middle from Nunivak Island, across the width of the shelf. The data are from April of 2008, remember that 2008 was a cold year, and July of 2008. So, April is on the left-hand side of these graphs, and July is on the right. And so, the only things I really wanna call your attention to are that Synechococcus is, as most phytoplankton, concentrated in the upper 20, 30 meters, for the most part. They tend to be closer to shore. When we look at them in a spatial plot, which are the bottom sets of graphs, you can see that, interestingly, regardless of whether it's April or July, we don't see Synechococcus north of about 60 degrees, in the southeast Bering Sea. Sometimes we don't see them south of 60 degrees north, but, oftentimes, that's where we do see them, and so, we can see lots of spatial distributions. Now, just a, sort of, a general picture, of what the Chukchi, Northern Bering and Chukchi Sea looks like, from a seasonal point of view, here's data from 2017, June, which was the ASGARD 2017 cruises, it's here, on the left, and September, the Arctic EIS cruises, on the right. Again, section plot, up at the top, again, showing that Synechococcus is closer to shore, just not right on the shore. When we look at it in a spatial plot, again, if we look at just the ASGARD data, that was encouraging, because we didn't see it north of 60 degrees, in the Bering Sea, and that continues into the north Bering and into the southern Chukchi, all these concentration, cell abundances, are nice and low. What was surprising, is, that when we went and sampled, late in the year... So this is our September cruise, the Arctic EIS cruise, actually, we saw massive amounts of Synechococcus. For the purposes of being consistent, I kept the scale the same between these two. So, if you were to take, and compare, the ASGARD cruise with the EIS cruise, that's the net accumulation of Synechococcus, from June to September. Because I don't like seeing a bunch of off-scale dots, I, actually, increased the scale by a factor of 10, so, this is now up to about 15,000 cells. And so, we can, still, start to see some of these northernmost samples, actually coming on scale, but still, all of this region, from Kotzebue Sound, around Point Hope, Point Lay, sort of, approaching in on Icy Cape, all still are off scale, so, this was very surprising, to us, because we didn't see a seasonal signal, in Synechococcus abundance in the southeast Bering Sea, but we're seeing a very clear seasonal signal, even though it's further north, in the Chukchi Sea, or northern Bering and Chukchi Seas. So, well, why is that? Well, of course, as every phytoplankton person does, we just start correlating everything to everything, and it seems that temperature is the most interesting correlate, with Synechococcus abundance. I guess, if you were paying attention to the first few slides, you, probably, would've guessed that that's where I was gonna end up, is, that temperature warms, Synechococcus increases in abundance. On the left graph, that's all of our data, so the whole water column. On the right is just the surface 10 meters. There is a moderate difference, in the ability to explain the data, but the reality is that there's a very strong relationship between increasing temperatures and increasing Synechococcus abundance, even in, now, in the Bering and Chukchi Sea regions. But, it's not all temperature. Temperature's just the dominant driver, it appears. So, here, I've taken and plotted the abundances of Synechococcus, they're the dots with the color scale as their abundance, on salinity-temperature space, and I've drawn in the warm coastal water, and the warm shelf water, water-masses, that, as defined by Seth Danielson, in his 2020 paper. And, so, what you can see is that, as expected, there's no Synechococcus when the water's really cold, less than about 3 degrees, or so, maybe even, a threshold closer to 5, and they see them most frequently in the lower-salinity waters, again, consistent with the fact that we find them closer to shore, and not in the Anadyr Current, and other areas, offshore. The right, the graph on the right, is a dissolved inorganic nitrogen-versus-temperature plot. Again, the color of dot is Synechococcus abundance, and, as expected, you see all of your Synechococcus down here, where it's warmest, in the most deplete in dissolved inorganic nitrogen. So, we're suggesting, as a hypothesis, that Synechococcus may be a good biological proxy for coastal water influence, and when we see it further offshore, it may be a, sort of, a tracer, in a sense of offshore movement of these coastal waters. Although, to really assess this, we need to find water with higher temperature and higher salinity values, and see whether or not Synechococcus is there, or not. But, it does seem that it is growing quite healthily, in these coastal waters, in Alaska. But, if you remember back to one of the earlier slides, I said we have large diatoms, on one end, and really tiny Synechococcus on the other, and it, probably, doesn't take a rocket scientist to see that it takes a lot of Synechococcus to be the same amount of carbon as diatoms. So, how do we, actually, try to put these on the same scale, now? So, we can, actually, get carbon from our flow cytometric data, as well. I won't go into the gory details of physics of light scattering, but, the reality is, that, as cells go from being small to bigger, they change the way in which they scatter light, so, a bigger cell scatters more light forward, than a smaller cell does. So, what we can do, then, with our flow cytometric data, is we can take and relate that forward scatter signal, here on the X, to the carbon content in particular cell types, on the Y, and we get a really nice relationship across a very large range of cell carbon, and cell scattered signal, both for field samples, as well as cultured samples. So, what we can do, then, is we can take our abundance maps, and we can multiply them by this carbon conversion value, and now, we can create carbon biomass maps, associated with Synechococcus. This is where it becomes really interesting, because, now, we can start to compare them on the same units, carbon, as the diatoms. And so, in this plot, we're looking at the integrated Synechococcus biomass, which shows an increasing seasonal amplitude over back-to-back warm years. So, first, start by looking at the leftmost graphs, These are the ASGARD 2017 data, and the Arctic EIS 2017 data, it's the surface plot, now, the Synechococcus is presented as carbon units, so this is their mass, in carbon per meter squared. All of the color scales on all 5 plots are the same, so you can directly compare them all to each other. Starts off with very, very low carbon biomasses in the June of 2017. By the end of the summer, September timeframe, you can start to see the ingrowth of Synechococcus, here, in Kotzebue Sound, is, sort of, working its way, ever so slightly, around Point Hope. When we look at 2018, interestingly enough, that, all that biomass goes away, right? It resets itself, almost to the same biomass-level, in spring of 2018, as it was in spring of, of 2017. We were fortunate enough, with Phyllis' help, to get some samples from the Healy 1801 cruise, that summer. So, it was a little bit earlier in the season than the Arctic EIS cruises, but, what you can see, is, that there's a greater expansion of the spatial extent of high Synechococcus biomass. It's still in the same region, right? It's still around Kotzebue Sound, it's still going around Point Hope, maybe, going a little bit further north, now, but the spatial extent and the seasonal magnitude is increasing. We don't have data for the spring of June, of 2019. For this talk, because I don't have any data, I'm gonna assume that they reset, back, to the same levels, like they did in '17 and '18, but now, when we look at the end of the season, September Arctic EIS 2019 cruises, that spatial extent and biomass-levels have, yet, further increased. So, the seasonal amplitude is increasing, from 2017 to 2019, as we have 3 years of continuously warm water. So, what does that mean, in terms relative to diatoms? 'Cause diatoms are what fuel fish, or so we've... We are trained, as biological oceanographers, that "all fish are diatoms", I think is the exact quote from Cushing, from 60 years ago. Diatom biomass, in the spring, has a huge range, anywhere from zero to 4,000 millimoles carbon, but the average is about 21. That 21 is down in the bluish color, on these scales, so, in the spring, there's no blue, so diatoms are clearly more important. When we look at the end of season, the diatom biomass is much reduced, it's from 0 to 300, in its range, but it's about 18 millimoles carbon, in the mean. Again, that's in the blue color, and you can see, that, everywhere where it's this sort of yellow, red and peach color, Synechococcus is, actually, more abundant in a biomass framework than diatoms are. So, to think, now, about what their relative contributions are, not just, sort of, a Synechococcus-versus-diatom war, here, because there's lots of other phytoplankton, right? There's dinoflagellates, there's other flagellates, etc. So, these two plots, I've looked at Synechococcus biomass, as a percent of total phytoplankton on the Y, and total phytoplankton on the X, and the color-coding on the dots are temperature, on the left, and salinity, on the right, and what you can see, is, that, when you have really high biomass values, there's very few, if any, Synechococcus biomass, hanging around. Which is what we'd expect, right? Our blooms are dominated by diatoms. However, as you start to get to values that are only a factor of 2, maybe a factor of 3 below the maximum, Synechococcus biomass really starts to take off, as a fraction of the total, oftentimes getting upwards of 40, 50%. And, what you can see, is, in the left panel, it's the red dot, so, it's the warmer temperatures, or where they're most abundant, relatively speaking, and on the salinity plot, it's the yellows to greens, right? The lower salinity is where they're most abundant. But, thinking about phytoplankton and carbon, while it works for me, it doesn't always work for those folks that measure chlorophyll. So, let's try to, sort of, put this in chlorophyll space. These blue dashed lines, represent the amount of phytoplankton carbon that one would be associated with. One microgram of chlorophyll, the long dashed line, and two micrograms of chlorophyll, the dash-dot line, and it's in the same, in both panels. So, you can see, that once you get to about 2, down 2, or up to 2 micrograms chlorophyll, Synechococcus, really, starts to become a meaningfully important component of the community. Spending most of my time, prior to working in the Arctic, in the Sargasso Sea, we never see chlorophyll values this high. So, to see Synechococcus becoming important at such a high chlorophyll, is really interesting, to me. But it is important to note, that, much of the year, chlorophyll values are down in this range, of one to two micrograms, and so, Synechococcus is becoming a real important player, in the biomass. So, now, the question is, as well, has it always been there, and we just didn't see it? Is it changing, over time, increasing, decreasing? And, to try to answer that question, I'm trying to pull some data from the literature, and so, there's a long list of caveats, like, methods are all slightly different, they're all slightly different stations, etc. But, I've tried to capture, at least, most of those caveats in what I'll talk about. So, here we're looking at data in the Bering Sea, and, again, at the top is that temperature anomaly plot, that Phyllis put together, all those years ago. There's data from Lu, et al., from a cruise in 1999, in July, and shown by the gray dashed line, here. It's a cold, that portion, was a cold anomaly period, and what they found, was, that Synechococcus biomass was low, less than a millimole, so, at the very, very low end, like we saw in the Chukchi Sea, during June of 2017 and '18. Their cell abundances were all very low, a thousand, again, at the very low end. Our Bering Sea data, which was compiled over 6 cruises, again, shown by the gray dashed lines, here, between 2008 and 2010, show, also, during a cold portion of the record, show very similar maximum values. All of our biomass estimates were less than a millimole of carbon per meter squared. I think there was only one or two samples, where we had more than a thousand cells per mil. So, very similar to the Lu, et al. study, from, roughly, a decade earlier. Fortunately, we had the opportunity to get some samples from a cruise of opportunity in 2021, which we were all excited about, because, after we sampled, as part of the Bering Sea ecosystem study, a few of those, later, started to warm up. Interestingly enough, 2021 was back as a below-average temperature year. This is data from the NOAA ERSST version 5 data, just chopped it down, to not be overwhelming, but the black dot, here, is temperature in '21, and so, it's a little bit lower than the mean, in a sense, and, interestingly enough, our Synechococcus biomass and abundance values were the same. So, we really can't answer this question for the Bering Sea, because, by fate, dumb luck, choose your framework, we always seem to be sampling in cold years, or cold periods, and so, we don't really know what would've happened, in, let's say, the early 2000s, when there was a period of 4, 5 five years, when it was warm, or, in the late 2010s, again, when there's multiple years of warm water. So, Bering Sea, we really can't answer that question, of, is it changing over time? The Chukchi Sea, however, I think we can answer that question, and the punchline is, it looks like it is incr- The Synechococcus abundance is increasing, over time. So, again, going through the literature, pulling out the data that I could find, one of the caveats was, again, is station, and so, the data that I've compiled, in these two graphs, the top graph is Synechococcus biomass, the bottom graph is temperature of the water, at the time, all fall in the region of the Chukchi Sea, that's bounded by this black box, whether it's our data, or data from these other studies, I was able to find. And so, we can go back, about, to 2008 or so, when Matt Cottrell and Dave Kirchman made some observations of Synechococcus, biomass was very, very low, temperatures were cold. There was a paper by Lee, et al., of 2010, again, very, very low biomass, very low temperatures. Thankfully, Sam Laney and others made measurements, during the ICESCAPE program, biomass is starting to get a little bit higher, in it's range, right? It's still sitting, you know? Values are at zero, but there's other values that are positive. Digging temperature outta the ICESCAPE data has proved elusive, to this point, so, I don't know exactly what the temperature is, but it was, again, starting to show an increase, just from the broader patterns that we see. The blue dots, here, are all of the Arctic program data, so whether it's ASGARD or Arctic EIS, they're all here by these, sort of, mid-blue dots, and, you can see that, again, while we do see, in some stations, no or very low contributions of Synechococcus biomass, the range over which they're extending is greatly enhanced, relative to the data from a decade prior, and the temperature ranges are also much, much greater. So, what happens? We go out, in 2021, and we're all excited, except, we, now, don't see nearly as large a range. Again, we see values close to zero, and they are off the... There are positive values, right? We do see cases where their biomasses is reasonable. It's just not nearly as high as during the Arctic program, during 2017, '18, and '19. And so, what we can't resolve, yet, is that, because 2021 was an anomalous year, so, this is a temperature anomaly plot, looking at August 2021, subtracted from August 2020, showing that the Chukchi Sea region is in blue, which means it was colder than in 2020. So, is this reduction in biomass because it's colder, that year? Or, is it because that cruise happened to be in November, versus September? So, there's a temporal pattern we can't resolve, either, as well as it, now, dropping down in temperature, relative to the longer-term trends. But, at least, for the decade of 2008 to 2019, it seemed like Synechococcus abundance was increasing, lockstep with increases in temperature in the Chukchi system. So, what does that mean for the broader impacts? Well, first of all, smaller cells are less nutrient-rich than diatoms, even if they are the same size as a diatom. So, here's some culture data that we published a few years ago. On the top are data for diatom cultures, grown at 2 degrees. The bottom 3 graphs are flagellates, grown at 2 degrees. We don't, yet, have a Synechococcus polar isolate, to do this with, so we're using other non-diatoms as a proxy for what Synechococcus would taste like, and each of the graphs. going from left to right, are carbon content, nitrogen content in the middle, phosphorus content on the right. The red... Oh, sorry. The black dashed line is, actually, the Redfield ratio, as a biogeochemist, that's something we're all sworn to uphold. In diatoms, all of the data fall above that dashed line, that Redfield ratio, which means they're all enriched in carbon, nitrogen and phosphorus, much more so than flagellates are, for each of those elements. So, if a copepod were to sit there, and eat a 1,000 cubic micron cell, it's gonna get a lot less nutrition out of a flagellate, than a diatom. Again, thinking to what that means for biogeochemistry, in these systems, the biology, now, is uncoupling in a way that the nitrogen and the phosphorus cycles... In a way that's different than it had in the past, when diatoms dominated, right? And so, when we look at, here, on the far right side of this, this left-hand graph, this is the ratio of carbon-to-nitrogen, carbon-to-phosphorus, and nitrogen-to-phosphorus, where diatoms were abundant. Again, all well below the, the Redfield ratio, especially for the carbon-to-phosphorus and nitrogen-to-phosphorus. And, for the most part, we don't see that in flagellates. So, again, the implications of biology doing elemental cycling differently will ripple through to the biochemistry of the system. So, we may need to recal- And I may need to rethink, how that works. What that means to the cycling in the system. So, that's the Bering Sea, but, the Chukchi Sea doesn't seem to show that same pattern, when we try to look at how elemental cycling of carbon and phosphorus in the Chukchi Sea behaves. When we see large fractions, due to diatoms, all of these peach-colored, and yellow, and green dots, when diatoms are really abundant, they're all enriched in carbon, relative to phosphorus. So, the opposite of the case that we saw in the Bering Sea. And, so, we don't know why this is, it could be a fundamentally different nutrient environment, but, it could also be that the diatoms are adjusting to that new thermal regime. What I mean by that, is, that work that Jeff Krause and I published, a couple years ago, even if diatoms don't change their size, even if they're still present in the system, their nutrient content will decrease, as a function of temperature. That means that diatoms sticking around in a warm environment, is less good for fish, than it is diatom sticking around in a cold environment, right? You know, they start to look much more like flagellates, even though they're still a diatom. And so, because our data in the Chukchi Sea, was, you know, in the middle of a multiple, multi-year period of warm temperature, was the physiology of the diatoms changing? And we don't have an answer for that, so that, really, sits as a hypothesis, but that, definitely, will have an impact on all the higher trophic levels. As an example of what that means to higher trophic levels, and I apologize, these axes are backwards, these are because our modelers always think in limiting elements first, but the reality is that global models predict that the Arctic regions will become deplete in phosphorus, there'll be a decrease in the phosphorus-to-carbon ratio, in the phytoplankton community. Others have looked at at zooplankton growth, granted, Daphnia is not the best proxy for Arctic zooplankton, but at least Daphnia's growth is related inversely to food quality. As food quality goes down, so does its growth. So, there's the potential for these ripple-on effects, whether they be changes in the type of community, or the size structure, or just changes in the quality within a given diatom, that likely are to have negative impacts on higher trophic levels. So, can we think about how to take this data set, and expand it to make better predictions, or, just any predictions, at all, of larger-scale patterns? This is work that is actively ongoing, under our newly funded JPSS project. Satellite retrievals, here, on the left, have shown that in, basically, the 2000s to 2010, chlorophyll wasn't, really, changing much, in the Arctic, but, after 2010, or so, the chlorophyll started changing, right? And so, there's a fundamental change in the driver of primary production, but, we also know, that, somewhere in there, there's also changes in the underlying phytoplankton community composition, which impacts chlorophyll. And, so, the goal for our JPSS project, is to try to look at refining, developing algorithms, for Synechococcus prediction, and improving our diatom algorithms. This is the work that Pri and Jens Nielsen are leading, and, it works from the base premise that phytoplankton have different types, have different spectral absorption, and therefore you get differences in reflectant spectra, based upon who is in the water-column, and so, we can take and use those differences in reflectant spectra, and with temperature, primarily, to try to build these algorithms for Synechococcus abundance. So, these are, quite literally, data hot off the press, I think Pri sent these to me, either Monday or Tuesday night, I forget exactly which night, but, these are plots of our estimate, on the Y axes of predicted, in this case, chlorophyll, from the reflectant spectra, and from the temperature in situ for the ARC ICESCAPE data, where we have that reflectance data, plotted, as a function of our observations of direct extraction chlorophyll. And, we can see that, whether it's with our reflectance in a PCA model, or reflectance PCA model and sea surface temperature, we get very similar levels of predictability, and they're good levels of predictability. One of the nice things about the ICESCAPE data, is, we have lots of pigment data. One of the pigments is zeaxanthin, which is a proxy for, or which can be a proxy for cyanobacteria, of which Synechococcus is, and, so, we tried the same thing, of using reflectance in a PCA model, or reflectance combined with a sea surface temperature model, trying to predict, again, on the Y, and compare with our observations on the X, for zeaxanthin concentration. and again, you can see that we, actually, do a pretty good job of predicting the zeaxanthin concentrations, and it's improved, slightly, when we use sea surface temperature. Again, consistent with our observations that temperature seems to be a dominant environmental driver. So, with that, I just wanna leave you a few take-home messages. One is that Synechococcus is not the trivial component of the sub-Arctic community that we previously thought, at least during warm periods. Synechococcus biomass can be high, both in absolute and relative terms. It seems to be the biomass is highest when it's warm, less saline and nutrient-depleted coastal water conditions, at least, within the Chukchi, where we had back-to-back-to-back years of warm, or increasingly warm, water temperatures. Their net increase, net seasonal increase in biomass was growing, and their spatial extent was expanding, and our initial algorithm development attempts, to, actually, try and back-predict where Synechococcus may be, are starting to look to be promising. But, those are, quite literally, very new, so there's a lot of work, yet, to be done on our prediction abilities. And so, with that, I thank everyone for listening, and I'll stop sharing my screen, and I'll take questions.

[Heather Tabisola] Thank you so much, Mike. [muffled clapping] I'll clap [audio distorting]. [chuckling]

[Michael Lomas] Clapping loses something when everybody's on mute, I get it. [chuckling]

[audio distorting] 

[Heather Tabisola] Calvin.... Already had a question. My camera thing really slows, I'm sorry about that. I may just turn it off. Go ahead, Deana, read the question.

[Deana Crouser] Okay. Regarding cyano... [garbled] [chuckling] carbon content, [garbled] in summer 2018, 2019, what is a driving and dramatic increase, across the Bering Strait?

[Michael Lomas] That's an excellent question, Cal. Yeah, I think, in part, it is... You know, we haven't, sort of, laid out how far from the US side to the Russian side of the Bering Strait, you know the ACC extends, and things like that. All right. Now let me share, let me see if I can move that figure back, 'cause Cal wants to see the picture, again. There we go, all right. Come on. So, so yeah. No, I think, part of... No, too far, there we go. Get rid of this thing. So, you're talking about, like, down here, Cal? Is that what you're talking about? Oh, Cal, yeah. Now Cal's just being a punk. So, I think, part of this is just the slow expansion, in the Alaska Coastal Current, sort of wrapping around, here. [chuckling] Sorry, I'm trying to keep up with Cal's commentary, in questions. But, I think, part of this, is, this whole region is warming, a little bit, and so, it's creating an environment that's much more conducive to Synechococcus growth, is my hypothesis, for now.

[Deana Crouser] All right. Great question. Any other questions? All right. Looks like we've got a question from Ryan. "Hey Mike, great presentation. What was the source of the satellite chlorophyll data, showing the increase in the Arctic? OCCCI, Hermes, NASA?"

[Michael Lomas] Yeah, so... Ah, that's the Lewis, et al. 2020 paper, I am 90% sure. Or 95% sure, to be statistically accurate, that it was MODIS data, but, you know, I'd have to go back to the paper to actually refresh my memory of the exact source. So, that data, because it covers such a long span, there's also a change in data sources, from the early part, to the latter part, and so, whether or not some of that change is due to data source is a question, but, assuming that it's not a data issue, or things like that, that pattern, that flat chlorophyll, to increasing chlorophyll, while primary production was increasing, fundamentally suggests there was a change in phytoplankton physiology, right? It suggests that, in the early part, they weren't accumulating their biomass, but they were continuing to grow. And, in the latter part of that time record, they're now accumulating their biomass, but, because the productivity rate hasn't changed, they're not... They're slowing down their growth rate, so, there's some really interesting physiological adjustments, that are just hidden within satellite data that would be really worth exploring.

[Deana Crouser] All right. Now, let's see if we can get one more question, and then we can close it up. "Thank you so much for presenting, Mike." Ah, we got another comment from Calvin. Let's see, he says "New PACE satellite will present new opportunities for exploring phytostructure."

[Michael Lomas] Yeah, no, absolutely. So, I'm working with Antonio Mannino, and other members associated with the PACE science team, to try to develop better phytoplankton structure algorithms. Obviously there'll still be some regionality, but that's something we're trying to address, is, is the regionality of these algorithms, as well as just improved algorithms. So, I absolutely agree, that's gonna be a great opportunity, when it gets here, and, hopefully, we can... We were prepared to better understand the data.

[Deana Crouser] Can you elaborate on what PACE is?

[Michael Lomas] So, PACE is, what? The P is Pri, it's Aerosol, Clouds, and I forget what the E is. It's a new satellite ocean color mission.

[Deana Crouser] Oh, awesome.

[Michael Lomas] It is hyperspectral versus multispectral, so it'll allow better resolution, optically, which means that we'll be able to tell, better, similar phytoplankton groups from other phytoplankton groups, because we just have that hyperspectral aspects of their absorption spectrum, reflectance.

[Deana Crouser] Great, and we got two more questions, one from...

Thank you. [Deana chuckling]

[Michael Lomas] Pri just wrote the ecosystem is the E.

[Deana Crouser] Oh, there you go. [chuckling] A question from Libby: "Do you know if there have been any changes in the zooplankton size spectrum?" Thank you, Libby, for representing the zoo team. [chuckling]

[Michael Lomas] That is an awesome question. Isn't that what we're gonna explore, as part of our Arctic synthesis project? [Deana chuckling] I honestly don't know, mostly 'cause I haven't spent the time to look at the zooplankton data. But, yes, Libby answered her own question, and said, "Yes", so... [Deana chuckling] Now, at least, in the Bering Sea we're seeing those changes, but we don't have good phytoplankton size structure, necessarily, to line up with the zooplankton size structure, so... But I, definitely, think, now, with a better view of the phytoplankton community in the Chukchi, we should be able to take, and start to explore those connections, and the impacts of size structure changes, as well as potential quality, due to some of the other variables measured.

[Deana Crouser] Oh, how exciting. All right. One more question from Emily: "It sounds like there's some uncertainty in the influence of temperature versus timing of the samples. Do you have a hypothesis about the role of inner [indistinct] variability versus seasonality?"

[Michael Lomas] Yeah, so... The uncertainty, there, comes from the fact that our 2021 cruise, which was the most recent data, was not at the same time of year, right? So, it was two, a month-and-half, or so, after the Arctic EIS cruises. So, that's the only reason why I can't separate it out, is because I now have two variables, changing, you know, it's colder, so I would expect it to be lower, but it's also later, so, I was also expectin' it to be reduced, because of that. You know, we can look at the interannual variability, but, from the data we have, it does, indeed, show that their abundance, the net accumulation, over the season, is increasing from 2017, '18 to '19, and their spatial extent is going up, is increasing, as well. So, I think, it's safe to say, that, the interannual variability is at least as great as the, you know, seasonal changes, of whether or not you're beginning, or end of the fall season. But, I think, you know, in part 2, it's whether or not you have a series of years that are continually warming on each other, or if the system is resetting itself, at a much higher frequency. Like what the Bering Sea did, right? It was... started up, back in 2... Before 2000, it was roughly every year, there was... It was warm, then cold, warm, then cold, then, it moved to this pentannual structure, of roughly 5 years that were warm, roughly 5 years that were cold. You know, ecologically, those have very different impacts on how phytoplankton structure assembles itself.

[Deana Crouser] All right. We've got time for, maybe, one more question, and then we'll conclude. Let's see, this is Synechococcus... I'm struggling with this word. [chuckling]

[Michael Lomas] You can just say Syn.

[Deana Crouser] Thank you. "It is more abundant in higher temperatures, which is more straightforward, and, in fresher waters, which I didn't quite understand. Will you explain this a bit more?"

[Michael Lomas] Yeah. Yeah, so, I think the salinity aspect is, actually, really, really interesting, because it's not a variable we generally associate with Synechococcus, it's mostly temperature, right? Whether it's these global transects that have been done, looking at Synechococcus abundance, you know, temperature is a primary driver. My estim- My hypothesis, is, that, because Synechococcus actually does better in nutrient-deplete waters, really, the salinity is, sort of a, covariant, with low-nutrient waters, which are coming with the Alaska Coastal Current, and things like that. So, that's my guess of why there's a relationship to salinity, that it just is, really, a mirrored reflection of the low-nutrient environment in which it likes to exist, versus the Anadyr Current, right? That's cold, and salty, and nutrient-rich, where Synechococcus just, simply, gets outcompeted.

[Deana Crouser] Wonderful. Thank you so much for that question, Jiaxu. Well, I encourage everyone to reach out to Mike, if you have any questions, but we're gonna go ahead and close the meeting, we have meetings, following this. Thank you so much for coming, it was a great talk, thank you so much, Mike, for presenting. We'll go ahead, and...

Well, thank you all, for the opportunity to present the work that we have all been up to. I appreciate it.

[Deana Crouser] Yeah, absolutely.

[Michael Lomas] Cool. Have a wonderful day, everyone. Hey, Cal.

Hey Mike, it's Cal.

Yep?

Have we stopped?