EPS SCI 15 Lecture 11 Notes

Redfield Ratio

atomic ratio of carbon, nitrogen, and phosphorous found in phytoplankton and throughout the deep oceans

The Redfield Ratio (or Redfield stoichiometric ratio) is found to be:

C:N:P = 106:16:1

Key macro nutrients for phytoplankton:

Nitrate, phosphate, and (for diatoms) silicate. They are strongly reduced (bio-limiting) in the surface ocean

Why is primary production low compared to availibilty of macro nutrients in the Southern Ocean?

Lack of iron, a micro nutrient (trace element)

What is the main source of marine snow?

Phytoplankton

What delivers organic carbon to the deep ocean?

Marine snow

What is an important link between phytoplankton and higher consumer levels (predatory nekton)?

Zooplankton

The biomass of zooplankton is directly coupled to __________ ?

Phytoplankton (zooplankton biomass usually peaks shortly after phytoplankton blooms)

When does zooplankton conduct daily vertical migrations?

Surface at night, twilight zone during the day

What represents an important transport mechanism of organic matter into the deep ocean?

Sinking zooplankton fecal pellets

Nekton mainly consists of:

• vertebrates (fish, some reptiles, some birds, mammals)

• mollusks (squid)

• crustaceans (swim crab)

What/who occupies the higher consumer levels in food chains?

Nekton

If the top consumer feeds directly on the primary consumer, food chains can be ___________

Very short, i.e. phytoplankton → krill → baleen whale

• in other cases, food chains consist of severl levels of nektonic consumers

When nektonic animals die, they can:

sink fast to the deep ocean if not consumed by predators

Large food falls

An unusual large arrival of organic matter provided to the deep-sea community