I'm Jonathan Shurin. I'm a Professor of Ecology, Behavior, and Evolution at the University of California in San Diego. And I'm going to talk today about the ecology of algae in relation to their use as a bioenergy crop. And so, when most people think of ecology, they think of something like this pristine, beautiful mountain lake at the bottom of the slide there, some sort of natural undisturbed ecosystem, but ecology is something that happens everywhere in cities, and that happens particularly in agriculture. So, this farm field in the lower left of your screen there, or in ponds for growing algae like in the lower right here. Our crops interact with a whole bunch of different native species, things like pathogens, bacteria, viruses, fungi, grazers like insects, and other kinds of species, and these interactions can have a tremendous effect on the productivity of our agricultural systems, and for reasons I'll explain in a minute, for algae in particular. Okay. So what is ecology? Ecology is this branch of science that studies the interactions among organisms and between organisms and their environment that determine the kinds and numbers of species that we find in any particular habitat, and also how these things determine things like the productivity of ecosystems, how much biomass they produce, and what happens to that biomass. The reason ecology is relevant to algae biotechnology is that many species like weedy algae, pests like diseases, or grazers can limit algae growth, and so, the ecology can place a constraint on the productivity of algae bioenergy systems. But there's also an upside to this in that diversity can often be used as a tool to increase production. So, diversity, so by manipulating ecological interactions and things like probiotic bacteria or kinds of algae that might facilitate one another, we may be able to enhance the yield of our systems and make them more stable against fluctuations that take place in the environment. Okay. So, the first thing you need to know about algae is that they are extremely diverse. So, this slide on the upper left, if you take a teaspoon, or a few drops of water from anywhere in the ocean, or in a lake, or anywhere, and look under the microscope, you'll find probably somewhere between tens and dozens of kinds of algae. If you look over time, you might find hundreds or thousands of different recognizable types of algae. And if you look on the upper right here, the Eukaryotic Tree of Life. I've circled six different branches on this tree that include things that we call algae, so algae is a catch all category for photosynthetic microorganisms. So, single-celled organisms undergo photosynthesis, and different kinds of algae are found in each of these six different branches of the tree here, and so, different groups of algae like diatoms or dinoflagellate, it's a green algae are more different from each other or have divided off from each other deeper in the evolutionary past, then for instance, a whale is from a mushroom. So, many of these things that we call algae are in fact very very different. And not just in terms of their evolutionary relationships but if you take their biological traits, so for instance, just something like cell size here on this graph on the bottom, algae range are about four orders of magnitude from the smallest Prochlorococcus, Synechococcus, Cynobacteria to big things like Trichodesmium there. They range in size by about four orders of magnitude, and that may not sound too impressive until you realize that that is the difference in size between a fish and the island of Manhattan. So, that is a tremendous range in terms of just size alone and other sorts of traits. Algae are also very very different from one another. Algae are of interest to us because they are the most productive "plants" in the world, and I put plants in quote here because they're not really biologically plants, they're plants in the sense that they're photosynthetic. But because they're small and unicellular and don't make a bunch of complicated structures, algae grow very very quickly. So, this table over here on the left shows the oil yield in liters per hectare from different crops from corn, and soybeans, canola, jatropha up to microalgae under two different sort of conditions, and you can see that microalgae ranged from about one to three orders of magnitude more productive than any of these different terrestrial crops. And what that means is that you can produce the same amount of energy on vastly less smaller amount of land. So, this graph on the bottom shows the area of the United States, and then the amount of area you'd have to farm with different crops to produce a given amount of energy. You can see that for soybeans, you have to plant three United States area size fields of soybeans, whereas with algae, you'd could hypothetically do that with a much smaller amount of land. So, at their peak, when they're doing their best, algae are clearly the undisputed growth champions of the world. They produce biomass at a tremendous pace. But that productivity is actually highly variable. So, algae under different circumstances can be much more or much less productive, and so, that raises the question of what controls algal productivity, and the productivity of algae is under control by two different categories of processes. So processes that limit the growth, the production of new biomass, the rates of photosynthesis, the acquisition of resources, and these can include things like nutrients like nitrogen, phosphorous, iron, things are required for building a cell, light that provides the energy for photosynthesis, temperature, water chemistry things like ph or salinity that affect the growth rate of algae. And then, the other categories, things that impose death on algae and things that impose losses and remove biomass things like grazers, diseases like viruses or bacteria, or sinking if you're in the ocean or in a column of water. And so, the growth factors limit the input of energy and death affects the rate at which that energy is lost. And the other sort of unseen or less well recognized thing that limits productivity is algal diversity. And so, there's various reasons to suspect that more diverse algal communities may be better at growing. They may be able to acquire nutrients, or light more effectively, or grow under a wider range of temperature or chemistry conditions, and they may be more resistance to grazers or diseases. For instance, if an epidemic comes through and wipes out one species of algae, if there's another species present to take its place, then productivity may be maintained, even though you've lost one species and gained another. So, algal diversity may be a sort of tool or a mechanism that we can use to manage the productivity of bioenergy production systems. So why can't we just ignore ecology so we could just wall out the rest of the world and focus only on the algae that we're interested in growing? Well, one reason for that is that algae and their enemies disperse very very widely throughout the world. They're very very good at getting around. There's a saying in microbial ecology that everything is everywhere. This idea that there's just this continual rain of cells and any available habitat will be quickly colonized by different species. And we found that that is true. This picture on the lower left is an experiment, and we did measuring the dispersal rate through over land of some algae that we were growing in tanks. We have those green tubs that are measuring the movement or dispersal of algae from those big concrete tanks there. And we found is that dozens or hundreds of other recognizable types of algae also colonized these tubs just out of the atmosphere. And so, there's this constant rain of different species coming down. The other reason is that the enemies of algae can wipe them out very very quickly. So booms and busts happen very quickly with single-celled species. So an epidemic can sweep through an algal population and cause it to crash and kill off all of the members of that population in a matter of a day or two before you've even realize that something has come along and just annihilated your algae population. And so, things can happen very very quickly. We have lots of examples of this. So on the bottom here, I have photos of a couple of different grazers. On the lower left, there's daphnia. Lower right, there's a rotifers. There's also a fungal pathogen. In the a cell in the middle has a bunch of fungi cells attached to the outside of it that are infecting it. And this graph in the middle shows populations of algae and a fungi in a pond that we monitored over time where you see the algae population is that solid line, the fungal population is that dash line. You can see the algae abundance goes up, fungi increase as well. Eventually, algae sort of reached their peak. And then when the fungi reach their peak, the algae decline a little bit. The fungal population crashes, and then eventually the algae population recovers. And so this is an example of what's called a predator prey cycle. So we see a lot of these in ecology where you have populations of predators and prey that fluctuate with each other, and they go up and down in synchrony together. And this has shows that these sort of predators of algae, these pathogens or diseases can cause crashes or declines in algal populations, and therefore loss of productivity in our bio energy systems. Okay, so how can algal diversity help benefit productivity? Well, algae vary tremendously in what we call their ecological niches. This is an example with stream algae that grow on rocks at the bottom of streams. It's showing which species dominate under which kinds of environmental conditions. On the y-axis, we have flow velocity going from slow moving water to a fast moving water. And on the x-axis, we have patch age or days since the scouring flood has come through and wiped all these algae off the rocks. And you can see that some species at the top there, do very well in fast moving water, some do well and slow moving water. Some algae colonize rocks very quickly after disturbance, others take longer to show up. And so this diverse community, if you imagine an environment where the conditions are fluctuating through time, you can imagine that sometimes the environment might be suitable for one of these species but not for others. And as the environment changes through times, you might have replacement of one species by another. And so the productivity of the whole community might require to maintain that productivity might require that you have all of these different species present in this environment in order to achieve maximal productivity. And if we think about how the productivity of an ecosystem is related to its diversity, we might imagine there's a positive relationship, but that positive relationship could look very different in different circumstances. So this graph is showing extinctions or loss of species going from high diversity or high number of species on the x-axis to a low number on the left side there. And on the y-axis, we have ecosystem functioning which would be something like biomass per activity. So we might have a situation like this proportional loss line whereas we remove or add species. Every time we remove or add a species, we get the same increase or decrease in ecosystem functioning. So if we have more species, we'll just have the ecosystem productivity being just in direct proportion to the number of species. We might have something like this. Immediate catastrophe where in order to have a highly functioning ecosystem, we have to have lots of species. And if we lose any species at all, the ecosystem function declines precipitously right as soon as we begin to lose species. So if we have this rapid drop and then functioning being very low. We might have something like this top line called rivet redundancy where you can lose or add, where you only get increases in ecosystem functioning when you add species when there's very few species present. And once you reach some critical number of species, adding more species does not give you any increase in functioning. So this is called rivet redundancy. It's an analogy to something like an airplane where if you remove one rivet from an airplane, the whole airplane probably isn't going to fall apart. But as it remove more and more rivets eventually, your airplane will suffer some sort of catastrophic failure or functioning. We don't know what this looks like, but we have some examples to work from. This is an example from a study we did on the ecology of algae and bacteria in one bio energy pond studied over a year. So we monitored this pond repeatedly through time over year. We sequenced DNA of the organisms in that pond and looked at what species were present at different times and how productive that pond was in terms of biomass. And so on this top graph on the upper left, you have time on the x-axis there. And on the y-axis, you have the relative abundance of different algal groups. And you can see, there's a couple of different periods in this year long study. So up to about 200 days, there was one dominant species, this green species called coelastrum, and then there was a whole bunch of other rare species that were really low in abundance. There is sort of very low diversity because there's one dominant species in just a few other rare species. And then around day 200, things changed and that dominant species declined, and it was replaced by a large number of other species. So the diversity of the pond increased because we've lost that dominant species or had a large decline, and then had a increase in a bunch of different species. So in that second period, we have a lot of different species and no one single species that's dominating the community. And in this bottom graph, you can see that diversity is a very low up to about day 200. And then after day 200, diversity increased a lot. When we look at the productivity of a pond in relation to these different periods, this graph now on the right shows algal diversity on the x-axis plotted against the productivity of the pond, the mean and this red line. So mean biomass productivity, and then the variance through time is this green line. And you can see that periods when algae diversity was higher tended to show higher biomass productivity in keeping with our theory for how diversity should affect productivity. So on average, we had more biomass produced. But that wasn't all, we also saw there was less variance through time in this productivity, so times of high diversity tended to have very little fluctuation in biomass. So that biomass was more productive, but it was also more stable and it didn't tend to go up and down. And for any sort of agricultural system, that's what you want. You want things to be productive, but you also want them to be very reliable and dependable and to give you a sort of steady productivity not one that's wildly fluctuating, going up and down through time all the time. So this supports the idea that diversity is one factor that affects algal productivity, and that algal communities manipulating our co-communities and poly cultures of multiple species maybe one way to ensure more productivity and more reliable productivity. So I hope I have convinced you then that ecological interactions can work to either increase or decrease bioenergy productivity in algae bio energy systems. The colonisation by wild pathogens, grazers and weeds can place major constraints on productivity, can reduce your productivity. But the diversity of algae may be managed in various ways to enhance yield and try and maintain productive reliable systems. And therefore, understanding the ecology biology is key to the success of algae bio energy as a commercial venture and as a technology that might eventually be able to provide a reliable source of energy for people. Thanks.
