Geoffrey Schladow
Description: Today we talk with Geoffrey Schladow, Director of TERC, the Tahoe Environmental Research Center and Professor in the Department of Civil and Environmental Engineering at UC Davis. His work looks at the interaction between fluid transport and mixing processes with water quality in both natural and engineered systems. In this episode we talk about all things Lake Tahoe, from invasive species, the range of ecosystems, to it being the clearest it's been in over 40 years. Additionally, we unpack the research being conducted at TERC and the various methods we use to keep Lake Tahoe healthy.
Websites: Geoffrey Schladow's Page
Resources:
Show Notes:
[0:00:02] Introduction and Background Story of Professor Geoff Schladow
[0:03:40] Evolution of Research Interests and Importance of Funding
[0:05:28] Balancing Research and Center Management at Tahoe Environmental Research Center
[0:08:55] Lake Tahoe's Inspiring Environment and Collaborative Research Opportunities
[0:13:32] Monitoring and Research Funding at Lake Tahoe
[0:18:06] Balancing Development and Environmental Impact at Lake Tahoe
[0:21:30] Understanding Watersheds and Their Impact on Lakes
[0:24:58] Addressing Eutrophication: Examples and Potential Solutions
[0:29:54] Introduction to Hypolimnion and Oxygenation Technology
[0:34:09] Microplastics Research and Surprising Findings at Tahoe
[0:37:10] Downstream Effects of Microplastics and Ongoing Research
[0:39:42] Microplastics: How do they get into the water?
[0:42:48] Microplastics: A problem in all drinking water reservoirs.
[0:43:59] The Three Aspects of Lake Study: Chemistry, Biology, and Physics
[0:47:31] Vatican's Aggressive Fleet and Chiaudi's Innovations
[0:50:43] Clarity vs. Blueness: Understanding the Difference
[0:50:52] The Goal: Keeping Tahoe Clear
[0:51:32] The Science Behind Tahoe's Blueness
[0:54:26] Efforts to Improve Tahoe's Clarity
[0:54:37] Engineering approaches to particle clarity management
[0:59:23] Discovery of the impact of mysis shrimp on clarity
[1:04:40] Traits and Backgrounds Beneficial for Internship Positions
Unedited AI Generated Transcript
Introduction and Background Story of Professor Geoff Schladow
Brent:
[0:02] Welcome, Professor Geoff Schladow. Thank you for coming on today.
Geoff:
[0:05] Well, thank you. This is going to be fun.
Brent:
[0:07] Yeah.
Keller:
[0:09] We'd love to start off by hearing a little bit more about your story.
How'd you get to Davis and what got you interested in environmental engineering? Yeah.
Geoff:
[0:16] Well, that's a long story. So I'm glad we have an hour.
I guess I came to Davis sort of after a pretty circuitous path.
For a number of years, I'd been, I guess, a soft money researcher So I'd been working prior to that in Australia for about four or five years.
And then prior to that, I'd been at Stanford for four years.
And then prior to that, Australia.
So it was in some ways, Davis was when that opportunity came up, it was almost like a dream opportunity for me.
It was just, I was reaching a point where I was making, I guess, life-changing decisions.
Would I stay in Australia? Would I have a number of job offers working for government research labs?
And then the Davis, I guess, it starts off as an advertisement.
Yeah, there's a position. Should I apply? Yeah, why not?", And it just worked out, I guess. There was a lot of people applied for it, and I was the lucky one. Got the job.
Brent:
[1:31] Yeah. Could you define your role that you initially applied for and what you're doing now?
Geoff:
[1:39] Well, I guess faculty positions are very – I guess they're a lot broader than people sometimes think.
So certainly with students, they just think of professors as, well, he or she teaches these classes, and they were hired to teach those classes.
Well, that's only part of it. so you're hired into a department and you are responsible for teaching 102.
Three classes in different areas, but you're also given the opportunity to develop your own class, something or maybe two classes that follow your own interests.
So, the required, say, rigid undergraduate classes is just a very small part of what you do.
And then a large part of what you do is research. And so, again, from the point of view of an undergraduate.
They think the professors are all there just to teach.
In some ways, although most of us love teaching, we get most of our advancement and our thrills and recognition from our colleagues by the research.
[2:57] And even with the research, it isn't like you are hired to do research in this field A or B or C, you never know. When you hire somebody, their experiences in one area and their qualifications are there.
But if they suddenly take a tangent and go off, nobody can stop them.
As long as they keep teaching and teaching well and they keep bringing in the resources they need for their research, they're pretty much free agents.
So we're kind of like a marketplace.
We're sort of independent vendors with our stalls doing sort of what we want, taking us where our curiosity leads.
Evolution of Research Interests and Importance of Funding
Keller:
[3:40] Did you have a continual research theme throughout your career?
Or did you have different interests when you're working on Australian at Stanford?
Geoff:
[3:48] Yeah, it's evolved a lot. And a lot of it evolved because of the realization that to do what I want to do, I need to bring in money, funding.
I mean, funding to support the research and then eventually to support graduate students and postdocs and things like that.
So, early on, I was, I guess, interested in slightly more esoteric things.
You know, more the physics of fluids, what happens when you heat them a certain way, you know, what kind of motions does that produce.
And it was interesting. It was fascinating. I loved it. I was doing probably less fieldwork but more laboratory work and I was doing some pretty intensive computer simulations.
[4:42] And I guess over time, I started to realize, well, it's a pretty narrow field and it's sometimes hard to get funding in that.
And so, I started branching out more into, well, what are the water quality impacts of these motions?
What are the ecological impacts? And suddenly connecting these underlying physical processes with things that matter to people.
Even though my passion was with the, say, the fluid mechanics, it was these other things that make getting funding easier, how it affects health and the environment.
Balancing Research and Center Management at Tahoe Environmental Research Center
Brent:
[5:28] Sorry, this slipped down.
So now as you're the director of Tahoe Environmental Research Center, how much are you able to still continue doing the research while also running the entire center?
Geoff:
[5:44] Well, a lot less than I'd hoped.
I've been doing this for, I think, 19 years, which is a long time, probably longer than I thought it would be.
During that time, the center's grown a lot bigger.
The world has grown a lot more bureaucratic, and the university along with it.
Every year, it seems that there's more and more administration happening.
Takes away from what I'd hoped I'd be doing more of. But I still do it.
I sort of do it more and more through surrogates, through advising students and postdocs and working with colleagues. So that does get a bit frustrating.
So we were out on the boat yesterday and I hadn't been out on the boat for a few months.
And every time that happens, I think, I shouldn't let that happen. But then it happens.
[6:53] So, I mean, it's a trade-off. Somebody has to do it. And I just think, you know, I'm at a pretty senior point in my career.
I would rather do that administrative legwork and...
Creating an environment for new faculty and postdocs and students to work in and get my, to live vicariously through them.
Keller:
[7:19] Paul Yeah, yeah. What kind of graduate students typically come through the program?
Can it be isolated to a certain few majors or does it tend to be pretty widespread?
Geoff:
[7:28] RL It is really widespread. So, I mean, we don't have faculty associated with us directly.
So we're not allowed to hire faculty directly.
So we offer a facility, we have research labs, we have housing, we have boats.
We have to find funding to support, but then we try to encourage people at UC Davis, faculty, graduate students, colleagues from other institutions to come and work. Hey, we have this here.
Hey, we have this interesting problem.
Your expertise is just what we need.
We rarely can, we can't fund them.
But what happens is sometimes we write proposals together and that funds them.
So it's it's really trying to whip up interest and enthusiasm.
And then once you're here, I mean, Tahoe sort of takes over.
It's really, it's an inspiring place.
As I said, I used to work sort of in a laboratory more, but now when you go out on the lake and you just sort of look around 360 degrees, that's the laboratory.
Yeah. It's, it's, it is amazing. And I've never met anybody, at least anybody I want to work with, who isn't inspired by that.
Brent:
[8:55] Yeah.
Lake Tahoe's Inspiring Environment and Collaborative Research Opportunities
Geoff:
[8:55] And come, they leave with more enthusiasm than they often arrive with.
Brent:
[9:01] Could you expand on just why Lake Tahoe is so important?
Geoff:
[9:08] Yeah, well, yeah, it's beautiful.
It's unique but there are lots of beautiful and unique places.
In some ways, it's very symbolic. It's recognized not just in California and the Western US and all of the US as being special but people have heard of it around the world.
And because of this interest and because of the funding that that's attracted over half century now.
It sort of begs the question, well, if we can't understand Lake Tahoe or help Lake Tahoe, what hope is there for every other lake and stream and wetland that doesn't get nearly the attention?
I mean, they should all get as much attention as Tahoe, but that's not going to happen.
So the fact that there is a lot of attention here, that there are resources, puts this onus on us to say, well, what are we doing with our funding?
Where's this research leading to? And so, we've been, I don't know if it's fortunate, but you know, we've had the opportunity, I think, to make some pretty fundamental discoveries here that have inspired changes here, but also changes in other places, because people look to what's happening at Tahoe.
Brent:
[10:34] What were some of those discoveries?
Geoff:
[10:37] Oh man, you're getting technical.
Okay, so one of the big ones, this is going back about 20-25 years now.
So the belief back then was that the decline of clarity in Lake Tahoe, so clarity is I mean, it's something everybody can appreciate, how far down into the lake you can see.
But it's also more representative of just the general health of the lake.
So the belief back then, because it was reflected in lots of places around the world, it was the input of nutrients, things like nitrogen and phosphorus from fertilizers that people use on their lawn, some of it from atmospheric deposition, that it was nutrients stimulating algal growth.
[11:35] Controlled Lake Tahoe's clarity. So what we were able to show by we, and talking about a whole lot of people, students, researchers, and even myself, was that probably a more important factor were things that weren't alive. They weren't phytoplankton.
It was very fine particles that get washed into the lake, probably because of all the urbanization that has happened around Lake Tahoe. So- CB1 When did that start?
Keller:
[12:09] Like the urbanization trend?
Geoff:
[12:11] LRT That sort of started, say, in the 1960s. CB1 Okay. LRT And there was a lot of unregulated growth then, which has now become far more regulated.
So, what we're able to show pretty convincingly is that the majority of the clarity decline was due to this non-living thing that wasn't related directly to nutrients.
And so, that suddenly changed the whole approach to the restoration efforts.
So, that's pretty major. Because a lot of money has been spent at Tahoe and the idea that a lot of it may have been spent on things that weren't that important.
It was good to find that out at an early stage.
Keller:
[13:03] CB And to some of the institutions or organizations that are a part of the development, do they fund any of this research? Do they work with you guys?
Geoff:
[13:11] LW Well, yeah. We try to do that.
We certainly look to some of these management agencies that sort of institutions of government in California and Nevada.
Lake Tahoe embraces two states.
Monitoring and Research Funding at Lake Tahoe
[13:32] Yeah, they fund much of the monitoring that's going on.
So we basically, since 1968, we've been monitoring year-round nutrient levels, these fine particle levels, clarity, the phytoplankton, things like that in the lake.
And that's in large part funded by them.
And there are more sort of fundamental research questions. I mean, monitoring is, strictly speaking, it isn't research.
It's sort of like just keeping tabs on the sort of the vitals of the system.
But then as you look at that monitoring data, some interesting questions arise.
Then these local agencies, state agencies, that's not really their jurisdiction as to fund research.
They just can't get that funding very often. And that's where we go to places like the National Science Foundation or the EPA and other groups to say, here's an interesting physical, chemical, biological problem, we like to study it for this reason.
And it has application, not just at Lake Tahoe, but similar systems in other places.
Brent:
[14:58] Could you maybe expand on how the research done here in Tahoe has helped other people around the world?
Geoff:
[15:06] Well, sure. So, I mean, there are lots of examples like that.
One of the early things that was done at Tahoe, And by early, I mean decades before I'd been involved, was the realization that no matter how highly we treat wastewater, we can never remove enough of the nutrients in it to not have an impact on the lake.
So the decision was made in the 1960s not to discharge treated wastewater into Tahoe.
And that's had an immense impact. So there's a deep sewage system, there are no septic tanks, it's collected at multiple points around the lake, has some treatment, but then it's pumped out of the basin.
So that, and that example has been followed in lots of other places, not enough, possibly.
The others is, another example is, because of the research we're doing and the fact that.
[16:11] The tahoe has this reputation and we always get groups coming in from from different countries i wanna see what we do they want to learn what the problem is.
And i mean in a normal year we may have half a dozen different groups coming in from bolivia japan or somewhere and usually they come and they go but once every couple of years.
You know, a year or two later, they come back or contact us again.
And so, one of the more recent examples was a group from Chile.
[16:49] And the southern part of Chile, say, northern Patagonia, it's pretty much in a state where Tahoe was 40 or 50 years ago. So, they have these beautiful pristine lakes. You got the Andes in the background.
[17:06] And they have a relatively low population, but there's this southward migration in Chile, people leaving Santiago, going to the south, and they could see, well, isn't that what happened to Tahoe?
People came and the lake's quality, clarity started to degrade.
And so, we've been working with them for about the last five years now.
Well, we created a non-profit down there, Chile Lagos Limpios, so Chile's clear lakes or clean lakes.
And they have been supporting monitoring programs, the development of computer models, education programs.
So in some ways, initially, it was trying to replicate the approach we've taken here. you know, over time, it's sort of taking on its own unique Chilean aspect.
Balancing Development and Environmental Impact at Lake Tahoe
[18:06] I mean, And they're doing it in their way that resonates with people there.
Keller:
[18:11] And can development be done in a way that doesn't have a net negative on the lake?
Geoff:
[18:16] Yeah. Well, I mean, that's the fundamental question there.
I mean, it took us- by the time we realized what we should have done, a lot of the damage had been done.
So, they're at the beginning of the process and they're also far more keenly aware than we were 50 years ago of climate change.
So, you got this sort of dual thing happening, population growth, land use change with it, and then climate change.
So, the whole focus for them has been what are the impacts of that likely to be and how can they influence decision makers at the federal level in and at the local level to start, I guess, developing regulations or guidance that makes sense so you don't have development in sensitive areas.
[19:16] Nobody really wants to shut down development. People need jobs.
People need livelihoods.
But whether you build a pulp and paper plant in this particular watershed, or whether you have intensive animal rearing in this part of the basin or this close to a stream or a lake, are the sorts of things that they're working on, and making, I mean, those sorts of examples of intensive animal husbandry and, I mean, they're the big things. But there's also...
People. And people can be very careless in what they do. And cumulatively, that can be a very large effect.
And so, having people be aware of the impact they could have and how they can maybe do things a little differently.
So yeah, there are things that can be done. And in some ways, that's going to be a better test case than Tahoe.
Because yeah, they hopefully caught it early enough.
Brent:
[20:19] Is this research center one of the largest freshwater lakes research centers in the world?
Geoff:
[20:28] Um, I, I'm not sure. Um, I mean, because sometimes they're, I would say at the Great Lakes. Okay. Yeah. And there you have, often you have with, you know, multiple universities, you have, federal agencies co-located.
So yeah, we're not on that scale.
But as far as an individual lake, yeah, I think we're certainly up there with some of the largest. CB.
Keller:
[20:57] Could you give us a brief definition before we keep going on limnology? Limnology.
Geoff:
[21:04] The queen of the sciences. Limnology is pretty simply the study of lakes.
Lakes are are very special because in some ways, that's where things often end.
Been talking about things taking place in the watershed. Well, a lake is usually at the bottom of the watershed.
Brent:
[21:26] That's where all the- Could you give a brief background of what a watershed
Understanding Watersheds and Their Impact on Lakes
[21:30] is and how people should think about it?
Geoff:
[21:31] Okay. So, if we think of a watershed as literally being a basin within which all the water that falls within it focuses down to one point.
So if we think of the Sierra Nevada in California, everything on the west side of that, that's a watershed that flows towards the Central Valley and eventually goes out to the Pacific.
The east side of the Sierra, especially where we are in the sort of central northern Sierra, it flows to the east.
Lake Tahoe is surrounded by mountains of Sierra Nevada on one side and other ranges elsewhere.
So, we're like a basin, a bowl. And so, for us, we have a relatively small watershed.
And then whatever rain, whatever snow falls there either infiltrates into the ground, soaks into the ground, runs off into the lake, or it actually evaporates or transpires and leaves through the air.
[22:44] So, everything we do in a watershed, not just our watershed, but anywhere, all of that gets transported to the lake eventually, so the lake, and in particular, its sediments are like a repository of all the deeds and the misdeeds of what's happened for thousands, well, forever, really, millions of years.
Brent:
[23:07] And then how does eutrophication play into that?
Geoff:
[23:11] Okay, so eutrophication is this process of nutrient enrichment, so algae, phytoplankton, they need nutrients to grow, just like lawns need nutrients to grow.
So they're like grass, except they're microscopic and they float around.
And we need algae. It's the base of the food web.
So having nutrients flow into a lake, stimulate algal growth is good.
[23:45] Eutrophication is just too much of a good thing. Too many nutrients, too high levels.
And so that's when you get.
Too many algae, the algae die, they fall to the bottom, they decompose, they use oxygen, the oxygen drops, that promotes fish.
There's a whole cascade of events that take place.
So, eutrophication is actually a very natural process. As I said, everything comes into a lake and over thousands of millions of years, lakes become what we would say is more eutrophic.
Eventually a lake stops being a lake, it becomes a wetland, and then it becomes a bog, and then it becomes sort of squishy land, if you will.
But that can take thousands and thousands of years.
What the concern is all around the world is something termed cultural eutrophication, which is because of land use decisions that are being made, we're accelerating that process.
And so we're getting enrichment of lakes far quicker than it would naturally occur.
Keller:
[24:54] Paul Are there any prominent examples of that occurring?
Addressing Eutrophication: Examples and Potential Solutions
Geoff:
[24:58] Richard Well, I mean, at Lake, what do you mean, at Tahoe or?
Keller:
[25:01] Paul Just generally, like are there examples where that eutrophication has gone to a point where it really is beyond repair?
Geoff:
[25:09] Richard Well, I guess my job, not just at Tahoe, but say I'm in the Department of Civil and Environmental Engineering as well.
I'll, part of what myself and my colleagues do is work with lake managers and reservoir managers to help them better manage systems.
So to say where, to say it's beyond the point of no return is bad for business.
I'm not going to say that.
But yeah, some places, yeah, have gone to very bad places.
But it's through this kind of study, through limnology, the study of lakes, the physics, the biology, the chemistry, that as you understand the processes, you can at least present options.
And often, those options aren't taken up. They say, well, that's too expensive or it's not worth it.
But I mean, an example is another lake, I guess, about the same distance from Davis as Tahoe is.
And it's in the coastal range, so northwest of Davis. It's called Clear Lake.
[26:24] And it's sort of almost, in some ways, the opposite of Tahoe.
I mean, it's a very large lake, but instead of being sort of oval-shaped, it's got three distinct basins.
So, it's sort of very complex. There's a volcano there. Yeah.
[26:44] It's a shallow lake, and it's far richer in nutrients naturally than Tahoe would ever be or has ever been.
And it has lots of challenges because of all the nutrients that come in.
There are very, very high, a lot of algal blooms.
A lot of these algal blooms are what we call cyanobacteria.
So they're termed harmful algal blooms because they produce toxins.
And so it has multiple issues.
Mercury mining there is another one. So it's a case of it has a lot of problems, but we and others are working to address those problems and to actually come up with what we believe are manageable, affordable solutions.
But again, it's not our lake. I mean, and those decisions have to be made locally.
Keller:
[27:43] And we talked a little bit, and I'm sure we'll talk later on the talk about some of the ecological solutions.
What are some of the engineering solutions that you've worked on?
Geoff:
[27:53] Okay, well, continuing with Clear Lake, we've been running a monitoring program there for the last five years.
Probably a far more intensive monitoring program than we have at Tahoe.
And so what we've been able to determine is that the biggest issue, biggest challenge they're facing is the fact that many times throughout each summer, the bottom waters of the lake lose their oxygen, because it's so organic rich that just a few warm days, things quieten down and the oxygen just rapidly gets depleted. So.
Chemically, when that happens, it's the nutrients that are locked up in the sediments solubilize, meaning they come out of the sediments into the water, so suddenly you're adding huge amount of nutrients to stimulate even more algal growth.
You have mercury that's sort of locked up in the sediments.
Again, when oxygen is at low levels, it transforms to something called methylmercury, which is almost like an organic compound that can be taken up by organisms.
[29:19] And suddenly, once it gets into the zooplankton, and then the little fish eat it, and eventually people eat the fish.
And so, you have just those two problems alone.
If you could keep the oxygen always elevated, then a lot of those issues would, we believe, go away or at least be greatly diminished.
So the solution that we're proposing is something called, wait for this, hypolimnetic oxygenation.
Introduction to Hypolimnion and Oxygenation Technology
[29:54] CB So hypolimnion is the bottom waters of the lake and oxygenation is adding oxygen.
So the The idea is that as oxygen approaches zero, you turn on the system, it injects pure oxygen into the bottom of the lake via very fine bubbles, and they dissolve and they keep the oxygen up high.
It's actually an incredibly simple technology.
[30:25] So you may be familiar with these things you can buy at the hardware store, soaker hoses.
So yeah, those sort of rubbery, spongy thing.
So literally, if you pump gas or oxygen into that, you're going to get a lot of heat.
Comes out as a mist of very fine bubbles that literally dissolve within a few feet.
And so that's what it entails. I mean, it's not us sort of going there and connecting hoses.
There are companies that have done this on a huge scale around the country.
But that's something that I think is very affordable.
And we actually have a proposal in to fund a pilot project in one of the three arms of Clear Lake to do it, to monitor it, working with collaborators from the U.S.
Geological Survey, looking at the effects on mercury there, working with local tribes and the county looking at the effect on the algal blooms.
So, if that funding comes through, it'll be a I mean, a very tangible example of monitoring and research leading to an action that we can test whether it works or whether it needs refinement or not.
Brent:
[31:45] Yeah. And then when you talked about the methylmercury, is that the similar process to why a lot of the ocean fish are getting mercury poisoning?
That's why people are concerned about eating a large amount of ocean fish?
Geoff:
[32:00] The source of it, of the mercury, is maybe different.
So, for many places, the mercury is coming from atmospheric deposition because of things coming out of smokestacks from coal burning, stuff like that.
But the human health problem is that as mercury is ingested by the the smallest organisms, every time you go up in the food web, you get a 10 to 20 times multiplying factor.
So, by the time you get to a swordfish, for example, there are multiple things that have been eaten along the way, a lot of focusing of the mercury and then swordfish live for a long time, so they have very high body burdens.
So that's, yeah, that's sort of, Yeah, that's the underlying issue. Well, yeah, whether.
Where the mercury comes from is sort of a bigger question, but it's this food web focusing that's driving it.
Brent:
[33:08] And in order for the bacteria, the zooplankton to eat it or to take it up, it needs to just add a methyl group and then it becomes biologically available to those?
Geoff:
[33:17] It'd be certainly easier for it to assimilate.
Brent:
[33:19] Yeah.
Geoff:
[33:21] So it's, I mean, it's basically like methane is CH4, Mercury is CH3 with a Mercury replacing one of the H's. CB Yeah.
Brent:
[33:32] That was my point, just like how just four atoms can completely alter how it happened. LR It is.
Geoff:
[33:39] So, I mean, things like elemental Mercury really, well, sorry, well, cinnabar ore, which is where you get what Mercury is mined from.
I mean, that's basically holds the Mercury very tightly. So, it doesn't present any major environmental risk.
It's only when it's chemical form changes that suddenly it goes from being somewhat inert to being very dangerous. CB.
Brent:
[34:08] Yeah.
Microplastics Research and Surprising Findings at Tahoe
Keller:
[34:09] In regards to contaminants, is there research being done on microplastics at all? LR.
Geoff:
[34:14] Yeah. So, we started that about three or four years ago.
This was great because every summer we we employ interns, or sorry, I use the word employ loosely because we used to offer positions and students, some from UC Davis, some from elsewhere would volunteer and they would start that work or do that work.
And microplastics was one of those areas. I should say this summer we've started a more formalized internship program, we're actually paying a $3,000 stipend for eight weeks of work because we want everybody to have the opportunity without only those who don't need the money having it.
Anyway, so we started off a few years ago.
[35:04] Very simply, they just go along to beaches with a mark off an area and sieve the sand.
And everybody was shocked at just how much plastic was there.
Just leftover scraps from people's picnics on the beaches or stuff that are washed up.
So then, I guess two years ago, we sort of took it to the next step and we started doing measurements of microplastics in the water.
So measuring with these nets that are used to skim the surface and then taking water samples from different depths, measuring water that was being drawn out of the lake for people to drink and also looking at the sort of organisms, and clams that may have taken it up.
[35:56] And we were shocked at how much was there. So remember, as we said earlier, Tahoe doesn't get any wastewater.
A lot of plastics, microplastics in San Francisco Bay, stuff that's sort of been put in there from wastewater.
Microplastics go through the wastewater treatment and they're put back in.
We don't have that, that major conduit.
So, what we found is there were similar amounts of microplastics at Tahoe as there are in San Francisco Bay, which was just stunning to us.
Yeah, it was, yeah, it was just, it just blew us away.
And maybe part of the reason is that San Francisco Bay has this huge amount coming in, but it also has tides that are taking it out to sea.
We're very much a very closed system. We have one stream that goes out, and on average, every year, it takes out about 1 500th of the volume of Tahoe's.
Microplastics have a long, long life here, and they, seemingly, they accumulate.
Downstream Effects of Microplastics and Ongoing Research
Brent:
[37:11] And then, could you talk to some of the downstream effects of microplastics.
Geoff:
[37:17] Yeah. Well, I think that's something that's a really hot topic everywhere.
So even the work we were doing, much of it, we were, the sieve, this trawl we were using to skim particles, it has a mesh size, I think it's something like 250 microns or 150 microns.
[37:41] So we were only capturing things that were smaller than that.
There were very large plastic pieces, relatively large plastic pieces.
The things that we weren't measuring were things that were smaller than that.
The things that you could ingest. And so, we did a bit of work on that, but this seems to be a frontier everywhere.
It's when instead of it being several millimeters in size. What happens if it's several nanometers in size?
It's in the drinking water you use or it's- CB And you can't see it, right? LRM Oh, no, you can't see it.
Measuring it is difficult. So we just got a little bit more funding to just look at the final things.
Not much funding, just enough to do a pilot study to say, well, how much- when we compare what we get in this net we were using with what we missed, you know, just the pure water, we can measure the microplastics down to about one or two nanometers.
[38:55] And so, essentially we'll do this and hopefully in about six months, we'll be able to say, yeah, there are lots of these particles.
My guess is that there will be lots of them, because everything else we've studied, as things get smaller and smaller, there are just more and more and more of them.
And the other thing with these sort of nanoscale particles is that even mass-wise and volumetrically they're tiny, if you sum up all the surface areas of them, It's huge.
And so they become, they become...
Microplastics: How do they get into the water?
[39:42] I guess, what's the word? They become a substrate for other things to grow.
So anyway, it's hard to know how the micro, how the plastics get in there.
I'd like to think a lot of it is just from our carelessness.
People just throwing away stuff and maybe, yeah, things that we could control, we could greatly reduce if people were made aware of it.
But we're still not even sure of that. people swim in the lake, and many of our clothes are treated now with microplastics.
The rubber tires on our cars are not rubber, they're plastic.
And when you have 15 million visitors a year to the Tahoe Basin, to the watershed, that's a lot of tire wear.
And as the vehicles get electrified, and are carrying around lots of batteries, tire wear will increase.
So the problems, we do all this research thinking we're ticking off the problems, but in many ways, the problems are outpacing the rate at which scientists everywhere are working.
Brent:
[40:54] And then, have you looked at microplastics in the snow to see if it's coming from like the sky and like snow melt and then into the basin?
Geoff:
[41:05] No, we haven't, but that would be interesting. As I said, many of the nutrients, especially the nitrogen part of the nutrients, comes from atmospheric depositions.
So yeah, maybe there are microplastics that are just caught up in the air and we can blame San Francisco or the Central Valley.
But again, Again, it's a collective thing, and coming back to solutions, once you know what the the sauce is.
Then you can start thinking of solutions.
Brent:
[41:38] Yeah.
Keller:
[41:39] Are there any effective filters to collect these microplastics?
Geoff:
[41:45] Not that I'm aware of, but I haven't really sort of looked at it.
I mean, traditional filtration, running things across a mesh, this is just way too fine for that.
I mean, certainly in the case of Lake Tahoe, there's a huge volume of water in Lake Tahoe.
I mean, I think in our education center, we have this thing, if you were to empty Lake Tahoe and spread it out over California, the water depth would be sort of up to your knees. I mean, it's staggering.
Somebody was telling me the other day, this year in this record snowpack year, that the snowpack, the water equivalent of the snowpack was 50 cubic kilometers, something like that.
Well, Tahoe's volume is about 10 times that. So even all this snow, a huge amount of snow across all the Sierra, I mean, this volume is is huge.
Microplastics: A problem in all drinking water reservoirs.
[42:48] But again, it isn't just a Tahoe problem.
Every drinking water reservoir likely has microplastics and our bodies are taking them in and people are, I think, really interested and really studying what effects they have.
Keller:
[43:06] What are some of the ways that you guys are looking at water quality broadly?
I know there's some metrics that you guys have been keeping up since 1968, but what are those factors that you're putting in or looking at rather?
Geoff:
[43:20] Well, we do the basic things like, I mean, we measure water chemistry and that's sort of one of the specialties that we have here because the levels, the concentrations of nutrients are incredibly low here.
I mean, compatible with, you know, the middle of the Pacific.
And so, most commercial chemistry labs, it's way below their detection limits.
So, this is sort of one of our specialties.
So, we do that routinely down at different depths, once a month, actually twice a month.
The Three Aspects of Lake Study: Chemistry, Biology, and Physics
[44:00] And so, yeah, we do the chemistry. We sample the phytoplankton, the algae.
And surprisingly, that's an evolving story. No two years are the same.
Some years, one species dominates for strange reasons.
So we have the chemistry, we have the biology, and we also do the physics, and the physics is...
I find particularly interesting because that's sort of really my background, my specialty.
And that's evolving in large part because of climate change.
And so, what we've found, I mean, the typical pattern of all lakes is that in summer they get warm on top as you would expect, but that warm water is less dense, is lighter than, say, the cold water deep down.
And so when that happens, it makes it difficult for the lake to mix. It doesn't mix.
Brent:
[44:58] Oh, OK.
Geoff:
[44:59] And so, you know, one of the things we've been working on by sort of taking continuous measurements of temperature at all depth as well, is climate change impacting that, the amount of mixing that takes place.
So what we've found is that effectively what we would call summer, when the lake is warm on top and cool at the bottom, is getting longer.
So, probably in the last 60 years.
That, we call it a stratified period, maybe two or three weeks longer than it was previously.
And models for the impacts of climate change show that by the end of the century, it's going to be something like two months longer.
Wow. Which means, well, some people would say, that's great.
I can go to the snow, it'll be warm. And And yeah, can't argue with that. That's true.
But it means that winter is correspondingly shorter.
And winter is the time when more mixing takes place because it's cold and a lot of renewal, carrying oxygen down to the deeper parts of the lake takes place.
So you're suddenly getting less of that.
It's like, yeah, you're having parties at your house more months of the year, but there's less time to clean up.
And it's, there are consequences to that, we believe.
Brent:
[46:27] Yeah.
Geoff:
[46:28] And it's not, this isn't just a Tahoe thing. This is, you know, all lakes.
I mean, we're working in Chile, as we said before. And that's sort of one of the key questions there, in projecting, you know, what will happen there with climate change and with changing land use.
Brent:
[46:46] And then what are some of the other key metrics to determine lake water quality?
Geoff:
[46:53] Well, I guess the one Tahoe is synonymous with is clarity.
And we measure that using something called a Secchi disk.
So, Secchi was – Angelo Secchi was not a limnologist.
He was actually a Jesuit priest and an astronomer back in the 19th century and he was he founded the Vatican Observatory, and I guess he had a buddy of his, Admiral.
Vatican's Aggressive Fleet and Chiaudi's Innovations
[47:31] Chiaudi, who was in charge of the Vatican fleet. So, the Vatican was pretty aggressive in those days. It would go to war, things like that.
And Chiaudi was very, you know, R. Seki, who was a pretty smart guy.
How do I know if my warship is going to run aground?
Because I don't have a depth finder. And a lot of countries, a lot of ports would put chains across their harbors.
And these chains were designed to rip the bottom off a wooden vessel.
So, Seki came up with this disk to say, well, you know how deep the bottom of your ship is, it's 12 foot.
If you can see this white disc down 14 feet means, well, you can see a chain.
You keep centuries posted to look for it.
If you can only see this disc four or five feet down, then you're sailing blind.
And so, this weapon of war, I'd say, has now become the most widely used limnological instrument around the world.
And what's great is that everybody understands it.
Brent:
[48:48] Yeah.
Geoff:
[48:49] It's basically a disc. How far can I see down? We have probably, if we were to add up the inventory of equipment we have, we probably have a couple of million dollars worth of equipment.
All of it has to be recalibrated, it breaks, it's sent to the manufacturer.
I mean, it's a seccy disc, This 10-inch wide disc doesn't need any of that.
When we come back into the marina, up, people say, what was the clarity? And you say, 84 feet.
They say thanks and they go away. And so, it's really effective as a communication device, but it also integrates everything that's happening in the lake.
If it's very low, if you can only see down 40 feet, which for many lakes is good, but for Tahoe it's bad, then something's happening.
Is there a lot of runoff coming? Are there a lot of very fine algae, what is it?
[49:59] So, it's almost an instantaneous measurement for us telling us something is amiss. Every year, we put out this sort of clarity report. We did it like a month ago.
And I mean, it's very easy to average 25 numbers, but we have to work for a couple of months because as soon as we say, this is what the number is, the next question is, well, why?
And so, it takes us two months to figure out why. Was it a drought year, a wet year? What was coming in on the streams? Has the food web changed? Things like that.
So, yeah, that's probably sort of certainly the signature metric for Lake Tahoe and everybody looks forward to it.
Clarity vs. Blueness: Understanding the Difference
Keller:
[50:43] Yeah, could you explain the difference between clarity and blueness?
Geoff:
[50:52] Yeah. That's hard. So, you've probably seen those bumper stickers, keep Tahoe blue.
Well, really I think that was, that's supposed to be keep Tahoe clear.
Because I mean, that's what we'd be measuring, is the clarity, not the blueness, at least through the Secchi disk.
[51:32] This was a few years ago. So one of our researchers, Dr.
Shohei Watanabe, he came up with the precise wavelength of what Tahoe's blueness is. I forget what it is. It's 570 nanometers.
So, like, keep Tahoe at 570 nanometers doesn't have the same… CB2 The brain to it, yeah.
LRB But it's, I mean, it has to do with light scattering.
And basically, light scattering and light absorption. And so, if you have a lot of say algae at Tahoe, essentially the light that is scattered and the absorption of certain wavelengths of light start rendering it greener and greener.
If you had water that was totally devoid of anything, if you'd taken your earlier suggestion and filtered all of the water in Lake Tahoe, it would still be blue.
Because it's a reflection of the sky. But it's just not, that reflection isn't being affected by the scattering and absorption that's taking place.
So it's actually, I'm waffling a bit because it's a very simple question without a simple answer.
Brent:
[52:58] And then, what are the biggest things impacting the clarity now?
Geoff:
[53:05] Well, we were talking earlier, we found that it was the scattering of light by these inorganic particles that's the largest factor.
The nutrients do impact phytoplankton, and they do play a role.
It turns out that it's the very smallest phytoplankton that have the largest role, mainly because their size interferes with the wavelength of light.
So, historically at Tahoe, the phytoplankton were quite large.
And so, they didn't really impact clarity at all.
Over time, and this is sort of another sort of area of research, they've gotten smaller and smaller.
And so, there are years in which for whatever reason, phytoplankton are relatively high in abundance.
And we can see that, yeah, they may have clarity is really low that year on account of the phytoplankton.
More years than not, they're low and it's sort of things that are coming in from the watershed, very fine particles that are the dominant factor there.
Brent:
[54:26] And then, are you actively trying to...
Make Tahoe clearer, or are you kind of measuring it more?
Engineering approaches to particle clarity management
Geoff:
[54:37] Well, well, we are measuring it more, but we are actively making it clearer.
So when we found, for example, that it was the particles that are being washed in that were the major factor for clarity, that changed the whole management.
And so for the last 15 or so years, 15, 20 years, there's been a push to apply engineering approaches to keeping these fine particles out.
I think what's, I think the conclusion that I've come to anyway, and I think it's slowly being realized is that that isn't working.
Because one way of keeping particles out of something is you build what's known as a detention basin.
Basically, it's a hole in the ground. The water flows in and it stays in there long enough for the particles to settle out and it overflows and clear water leaves.
Well, the particles we're talking about are so fine that they're not gonna settle out in a few hours or a few days.
So even though there was good intentions, people were trying different things, it hasn't worked.
[56:01] Because over the last 20 years, despite the expenditure of billions, with a B, billions of dollars, the clarity has stayed the same when the effort or the goal was to to improve it by 10 meters, so...
[56:18] A sort of an interesting thing happened a few years ago is that Emerald Bay is sort of an embayment in the southwest corner of Lake Tahoe.
In some ways, it's a separate lake because there's only about a two-meter sill that divides the two. So, there's not a lot of cross movement.
So, one of the things we started measuring, this was around 2012, again, because one of our postdocs was interested.
In a weak moment, I said, sure, because I had to pay for it. There was no funding.
So, they went down, and she was interested in something called a Misa shrimp.
This is something she'd done her doctoral research on, and she just wanted to continue studying it. So, the Misa shrimp had been introduced to Tahu in the 60s.
[57:13] And for many, many years, people had been studying it, and it was there.
It had taken over. It had changed the system.
And yeah, people lost interest. It wasn't going anywhere. It was there.
So, she went down to Emerald Bay. You have to sample these at night.
You drag a net vertically through the water.
And they went out, and the net came up, and it was empty.
There were no mysis. And did the same thing in Tahu and yeah, there were lots of mysis.
So, three months later, they went back. I mean, and sometimes this is a natural system. There's lots of variability.
So, one zero reading is just noise.
Went out three months later, same thing, zero Misa shrimp.
And so, I started getting interested at this point.
And then they'd also go out during the day and they started to notice there was a return of these other zooplankton called Daphnia.
So, when the Misa shrimp had been introduced in the 60s, what was observed is that they immediately devoured the Daphnia. The Daphnia were gone.
And that sort of thing had been seen in other lakes where the mysis had been introduced.
[58:40] So, one of the things they started doing when they were there during the day is taking the Secchi depth measurement.
And they found in Emerald Bay over the next two and a half years as the numbers of Daphnia grew, you, and mysis was still zero, the clarity improved.
So, it improved about 10 meters, over 30 feet. It was huge.
[59:11] And at Tahoe, clarity varies year to year, but nothing like that.
And so, I guess what was born out of that was this- sorry, I should finish the story.
Discovery of the impact of mysis shrimp on clarity
[59:23] Eventually, the mysis came back, ate the Daphnia again, and the clarity returned to what it was.
So, what was born out of that was this idea that maybe the mysis are the problem.
We didn't realize they're affecting clarity. And so, there's been a lot of attention since then on, well, maybe we could remove the mysis because when they're absent, the system seems to heal itself.
Keller:
[59:49] CB are Daphnia present, like can they coexist at all over long periods of time?
Geoff:
[59:58] LR No, well, sorry, yes or no. So, this was some of the work done in the 70s and 80s where they found that if the Mises numbers was sufficiently low, I think the goes like, let's say, 27 per square meter.
Below that level, they can coexist. But normally, the MISIS numbers are 100, 150, 200 and they just- we just never catch Daphnia normally.
So that was the goal. It wasn't to eradicate MISIS because it's impossible, we believe.
But to keep the numbers low so they could coexist.
And suddenly, the idea was, well, we could do it in Tahoe and maybe we could get these large improvements in clarity. Yeah.
Keller:
[1:00:54] CB What is the significance of Tahoe being the clearest it's been in 40 years? LR.
Geoff:
[1:01:00] Okay. I was hoping you'd ask me that.
The significance is that about two, three years ago, what we noticed through this routine monitoring, and that's the value of monitoring.
It isn't a scientific experiment with a hypothesis. It's just keeping track.
Is the system changing? So, we went out and we were doing our usual monitoring of zooplankton, which I should say is funded purely through philanthropy.
We don't have agency funding for it. So, it's people who support our mission that pays for it. We pay for it.
We suddenly, we, they, notice that the zooplankton, were gone. Like, wow, I mean, they measure it during the day and boy, they've just disappeared.
And then they'd also go out at night and a few months later, they noticed the mysis have disappeared.
[1:02:15] So, extrapolating from what we'd seen years earlier in Emerald Bay, we made this prediction, we bet Daphnia will come back and clarity will improve.
And so, that's exactly what happened.
Six months later, we started seeing Daphnia and we started seeing the data shows starting in about July or August of 2022, the clarity in Tahoe went from being as as bad as it's ever been to suddenly the best it's been in 40 years. I mean, it's that clear.
And so, because it started in the latter part of the year, when you average it over the whole year, it doesn't really seem like a big change.
But when you look, when you compare that August to December period, with all the data before, we've never had that period as clear since the 1980s. Wow.
Brent:
[1:03:16] It's just amazing how quickly nature will fix itself.
Geoff:
[1:03:22] It is. And I mean, if I haven't said it already, I'm not an ecologist.
And it seems that, I guess, what I appreciated.
And I think people who know more about this subject that I do have also, some agree, some are still very skeptical that zooplankton can change things very quickly.
I mean, in a matter of months.
I mean, as I said, clarity hasn't changed here in 20 years.
And then to suddenly go back to better clarity than anything since the 80s is amazing.
But again, the question is, well, how do you keep that going?
Because the Mises will come back, the Daphnia will go, and the clarity will return.
So, my big push in the last year or two while this has all been happening is we should be out there studying this because there are lots of things we don't know.
This is the opportunity to see the system when it's rapidly changing and try to to fill in those knowledge gaps. Certainly.
Traits and Backgrounds Beneficial for Internship Positions
Keller:
[1:04:40] What are some of the like main- because you're talking about how you have positions open for interns coming in for this summer.
What are- and you have these questions that you want to have answered.
What are some of the, I guess, traits or backgrounds that you guys could benefit from?
Geoff:
[1:04:57] Well, we consider ourselves sort of quite multidisciplinary.
So, you know, we have staff and faculty who are working on forest health.
So, you would say, well, that's got nothing to do with the lake.
Well, it does because that's part of the watershed and the watershed feeds the lake. But there are people, so I know one of the interns who is coming in, that's what he is interested in.
And they're thrilled to have this guy, he's actually from Sacramento, coming up here.
And yeah, he's going to be looking at sort of things like the water demand of trees, which changes as the health of the forest changes, as it gets things, trees get stressed by drought or by insect infestation, things like that.
We have somebody, one of the interns is looking at microplastics.
We have another program where we're using drones and helicopters to take images of the whole nearshore of Lake Tahoe every month.
And with a drone, we can stitch together these images very neatly.
There's just some great software.
You're interested in that?
Keller:
[1:06:13] I think we saw one of them when we were looking at it.
Geoff:
[1:06:17] Yeah. But with a helicopter, that's a lot harder.
And so, that's gonna be the intern, that a particular intern who's coming in, she's really interested in...
In tackling that problem. I mean, she's here for eight weeks.
She may not get to the final solution, but she's certainly going to contribute to it.
So, you know, they're just three examples. So, we have people, another one working in the chemistry lab. We do a lot of public education.
So, one of the interns will be working and maybe developing a new exhibit for our outreach center.
Brent:
[1:06:55] Yeah.
Keller:
[1:06:56] But they're coming in with their own questions or these questions that are already out there that they're assisting on?
Geoff:
[1:07:01] Well, that's it. At the end of the day, we need them to do stuff.
And this is the first year we've had them paid. So, they're going to have to do horrible things, like washing bottles, because our paid staff have to wash bottles too.
So, yeah, there's things they have to do. But when we told all the staff, hey, here are the interns, you can choose as many as you want.
But they can't just be washing bottles or just doing routine things.
You have to work with them. You have to mentor them.
They have a research project. At the end of the eight weeks, they're going to be making a public presentation.
They're going to have a poster. We're going to have people there, and they're going to be explaining themselves, which I think is a great conclusion to the summer. And I think it's a tremendous growth opportunity.
Not all undergraduates can get.
Brent:
[1:08:02] Trevor Burrus Definitely. And then, as we kind of wrap up here, could you talk about the State of the Lake report and what that kind of synopsis is?
Geoff:
[1:08:13] Dr. Richard D. Grover Yeah. So, I mean, for many, many years, we're associated with this clarity reading, with the Secchi depth.
And it sort of occurred to me, well, the center opened in 2006.
And you bump into people and they say, oh yeah, UC Davis, you do that disc thing.
And it occurred to me that, wow, we've got this $13 million center and all people think we do is sort of go out and look at a white disc.
Because we're our own worst enemy in saying what we do. I mean, we do this low-level chemistry. We do a tremendous amount of things.
So the State of the Lake Report.
[1:08:58] Was an attempt to let's look at all this monitoring data, this routine data, let's plot it up, let's say very succinctly, written not for scientists, but written for the general public.
You know, what's the long-term trend? How was this last year different?
Did it buck the trend in some way? And I naively, I was a lot younger there.
First one was 2007. I thought, well, Yeah, it'll be hard the first year, but after that, it's just adding another point.
What could be so hard? But it's taken more time, but it's been incredibly rewarding.
Because in some ways, we collect so much data that a big challenge is actually looking at it.
You sort of think, oh, we've got it, we've got it. But this way, it forces you to plot it, and look at it, and try to explain what's happening.
So, it's been, I think, a huge success, I think, for publicity for us, but also advancing what we do.
And so, yeah, it's sort of a love-hate thing. I mean, where are we now?
We're in midway through May. I need to start working on it.
It takes a a little bit of time, but it's not, yeah, it's worth it.
Brent:
[1:10:21] Definitely.
Keller:
[1:10:22] Do you have any parting words of wisdom or any advice for people listening?
Geoff:
[1:10:27] Yeah, well, if there are students listening, then think about limnology, not just the physics, physical limnology, the biological.
I mean, they're all important. How they interact is important.
But basically, lakes, reservoirs are just central to our communities, to our lives, to our well-being and so you know one of the things we actually lack is people working in the social sciences.
There's a lot of questions on, one of the big questions of Tahoe now is is recreation and you would think a tourist-oriented place like Tahoe would like you know bring it on But certainly during COVID, when there were lots of people up here, that was – the basin couldn't handle that amount of recreation.
So, how do you manage that on public lands?
What's too much? What's enough? What do people want?
So, there are lots of questions outside the hard sciences that anybody – not anybody, but people from a whole range of backgrounds can deal with.
That it's sort of very local.
It can be an international problem, it can be a challenge, a problem in a very small community. So yeah, limnology, it's where it's happening.
Brent:
[1:11:53] There you have it.
Keller:
[1:11:54] Thank you very much Professor Schladow. Thank Thank you.
Geoff:
[1:11:56] This has been a lot of fun.
Brent:
[1:11:57] Yeah.