Marine Microbiology 1 (Jason)

Question 1

Define biogeochemical cycling

Answer 1

The biological processes which drive the flow of elements between soils, sediments, water, and the atmosphere.

Question 2

What is the Redfield Ration

Answer 2

• The ratio of carbon to nitrogen to phosphorous in marine plankton.
• 106:16:1
• Used in generalised studies of the ocean to understand which nutrients may limit growth.

Question 3

Define biological stoichiometry

Answer 3

The study of the balance of energy and multiple chemical elements in living systems.

Question 4

Describe the marine carbon cycle

Answer 4

• CO2 from the air dissolves into the ocean which forms carbonic acid (H2O + CO2 = H2CO3).
• The carbonic acid can break down into bicarbonate and carbonate.
• The interchange of these forms of carbon creates a pH buffering system that leaves the ocean mildly alkaline.
• Autotrophic microbes absorb dissolved CO2 and convert it to organic carbon molecules such as DNA, lipids, and carbohydrates.
• In this way, marine microbes remove CO2 from the ocean and air.
• The fixed microbial carbon can then be eaten by heterotrophs, released as a gas, or released into the water in dissolved or particulate forms.
• These particles are called marine snow.
• Marine snow is colonised by microbes which break it down.
• This process continues until the carbon is released as a gas or reaches the deep ocean.
• Most of the carbon is stored in the deep waters but an upwelling of water can bring it back to the surface, creating microbial blooms.
• Snow that reaches the sea floor forms new sediment.

Question 5

What is the microbial carbon pump

Answer 5

The process where carbon is fixed from the air by microbes and then transported to the deep by marine snow.

Question 6

Which microbes are responsible for the majority of the ocean’s photosynthesis

Answer 6

• Half is carried out by the genera Prochlorococcus and Synechococcus (sometimes called nanoplankton).
• The rest is by larger cyanobacteria and eukaryotes such as Diatoms.

Question 7

What substance have marine microbes evolved to absorb blue light better

Answer 7

Divinylchlorophyll

Question 8

Define ecotype

Answer 8

A population of microbes that is genetically similar but ecologically distinct.

Question 9

What is viral shunt

Answer 9

Viruses kill about 20% of the ocean microbial biomass every day. This transfers microbial carbon to the water where it begins to fall as marine snow. This prevents the carbon passing to larger heterotrophs and instead accelerates the carbon pump.

Question 10

Describe how ocean acidification occurs and the impacts it can have

Answer 10

• As CO2 dissolves in seawater the protons it releases acidifies the ocean and converts carbonate to bicarbonate.
• Ocean acidification can prevent shell-formation and corrode shells which have already been built.
• However, some species may grow better in high CO2 environments. Rates of photosynthesis and calcification may increase, and the carbon may pass directly into the water as organic carbon, increasing the carbon pump effect.