Welcome to BIO121/ESS120: Introduction to Environmental and Ecological Microbiology at UC Merced! This page provides additional online content associated with the course, including short video lectures by Professor Beman, additional videos and interactives, and additional reading materials.
Land to Sea
How does microbial ecology vary as we move from land out into the open ocean? As we will learn, there are consistent patterns that we see along this transition, and these patterns explain some fundamental aspects of all life — not just microbes — on land and in the ocean. In between, we will cover freshwater microbial ecology, as freshwater obviously connects land to sea.
One of the things that annoys me is that marine ecosystems are often a single chapter in ecology/biology textbooks, despite covering 70% of Earth’s surface! A lot of this simply has to do with traditional approaches to studying land versus sea, but this is changing, with microbiologists often leading the way. Not comparing land to ocean is a missed opportunity!
Obviously the major difference between land and aquatic ecosystems is the presence of water (duh)—but what are the implications of having so much water around? We have already touched on a few and will go into more detail this week.
6.1 From land to sea. In this video lecture we will start to think about some of the differences we see as we move from land to sea. This will help connect our thinking going forward. As always, pause, stop, rewind and take notes, and you can also change the playback speed as needed.
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6.2 Aquatic Primary Producers. One of the major differences we see from land to sea are the different types of primary producers, especially the organisms carrying out oxygenic photosynthesis. On land, this is obviously plants. In aquatic ecosystems and the coastal ocean, we see a mix of organisms: from specialized plants, to groups of algae, and down to different microbes. As we will learn next week, essentially the only primary producers in the open ocean are microbes, and they support the whole marine food web.
This webpage discusses some of these different groups and includes three videos that you should watch. The first may help you chill out and cool down, as it shows lots of marine producers waving in the waves and current. The second is more detailed and narrated by a familiar voice, so please watch it. There is a ton of great information in the second video. The third video is also interesting. Please read the remainder of the page and apologies for all the ads and such that show up!
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6.3 Nutrients and stoichiometry. As we learned and should be intuitive, water can be a key limiting factor on land. This the reason we see forests in certain places and deserts in others. Water obviously isn’t limiting in aquatic ecosystems, so what is?
Over the next few weeks, we will start to see the importance of nutrients in regulating microbial growth (and of other organisms). The two most important nutrients are nitrogen (N) and phosphorus (P). Interestingly, these two nutrients tend be found in very consistent proportions in many microbes, and this can actually shape entire ecosystems and biomes. This is the idea of ecological stoichiometry. I mentioned this briefly before and we will discuss this some more, as it links different materials and elements, and links large and small organisms.
Microbes are critically important in cycling N. Here you will read about the process of nitrogen fixation, which is important on land and in the ocean. This article focuses more on the land, and we will discuss this more next week:
https://www.nature.com/scitable/knowledge/library/biological-nitrogen-fixation-23570419/
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6.4 Freshwater Microbiology. In this video lecture we will learn about freshwater microbial ecology, including the idea of ‘typical freshwater bacteria,’ as well as the important role of methanotrophs. One way to think about this—now and going forward with the class—is that we often see a few dominant groups of bacteria in different habitats, and then a lot of variation in other, less common groups. We will see this in the ocean, and will think about it in an ecological context later on. In freshwater, there are dominant groups found worldwide, and then some variable groups such as the methanotrophs.
Apologies for the scratching sound during the first few minutes. As always, pause, stop, rewind and take notes, and you can also change the playback speed as needed.
Beman Lab, University of California, Merced 