Marine microbiology

• The Earth is ~4.5B years old
• Microbes are 3.5-4.1B years old, and likely evolved in the oceans
• Simple eukaryotes (algae) evolved ~2.2-2.7B years ago
• Fungi evolved ~1.4B years ago
• Marine animals evolved ~580-790M years ago
• Land plants evolved ~450M years ago
• The majority of life's history is in the oceans, and most of that is microbial
• Oceans cover 71% of the Earth's surface. Taking into account volume, the oceans hold ~99% of "living space" on Earth
• Marine microbes play key roles in maintaining a healthy Earth
• Marine organisms are poorly understood
• Marine organisms are a rich source of enzymes, bioactives, and anti-cancer/fungals/bacterials (blue biotech)
• Paradigms of marine microbiology have gone through significant change in the past ~50 years
• Oceans were seen as low-nutrient deserts with little activity or nutrient cycling compared to terrestrial ecosystems – in short, that not much was happening there
• Marine bacteria were considered minor players in the ocean
• Eukaryotic plankton were thought to fix most of the carbon and then fed larger creatures. Microbes were viewed as "just" decomposers
• Archaea hadn't been discovered
• Today we know that oceans process huge quantities of nutrients and influence global life
• ~50% of oxygen production and carbon fixation, largely by microbes
• We now know that oceans are far more biodiverse than previously thought
• Largely thanks to molecular techniques which identify microbes, but also new techniques for exploring the oceans which find fish, plants, molluscs, arthropods and more
• Microbes are the most diverse and abundant living things in aquatic habitats
• The total mass of the bacterium Pelagibacter ubique in the oceans is greater than the combined weight of all the fish in the oceans
• Life is driven by the need to get hold of nutrients for growth and reproduction. The size of the oceans creates some unique obstacles to microbes getting hold of these, which they must overcome (they're the base of the food web!)
• CO2 and N2 are captured by phototrophic and diazotrophic plankton. This creates a food web on which other marine life depends
• Carbon is easy to get from the atmosphere
• Hydrogen and oxygen are abundant in water
• Nitrogen and phosphorus are hard to obtain
• The sheer size of the oceans means that nutrients are often not equally distributed around the water column
• The Mariana Trench is deeper (~11 Km) than Mount Everest is tall (~8.8 Km), so think of the gradients that creates
• Vertical gradients form as particles sink, or due to an inability to reach the depths
• Sunlight is mostly absorbed by (and therefore heats) the top of the water column. Deeper waters are dark and cold
• Nutrients from the surface sink/diffuse slowly, and are processed into different forms as they go
• Different types of life consume different nutrients, and so also separate into layers in the water column
• Lateral gradients often form because of the slow diffusion of nutrients from land masses out to the deep oceans
• These gradients of nutrients, light, temperature and other conditions affect the distribution of living things
• As living things transform chemicals between different forms, this in turn affects biomass and biodiversity, as well as the chemical composition of the oceans
• This interaction between microbes, chemicals, and local geology explains much about why the oceans (and the rest of the world!) are the way they are
• Biogeochemical cycling


  The processes which drive the flow of elements between soils, sediments, water, life, and the atmosphere
• Coastal systems tend to be a lot more nutrient rich than the remote ocean
• Natural runoff, rivers, anthropogenic input etc. carry nutrients to coastal waters