Meet the plankton

Question 1

What are marine plankton? Give an overview

Answer 1

Marine plankton are microscopic organisms with the ability to convert sunlight into organic matter and are thought to have been ‘the beginnings of life on earth’.

Question 2

How much oxygen does phytoplankton photosynthesis produce?

Answer 2

50%

Question 3

Why are photosynthetic organisms important for the basis of ecosystems?

Answer 3

Because photosynthetic organisms of the open oceans are the fundamental food source on which marine ecosystems are based.

Question 4

Describe the trophic levels of a marine ecosystem

Answer 4

Carnivores;

• Quaternary consumers
• Tertiary consumers
• Secondary consumers

Herbivores (zooplankton)
-Primary consumers

Phytoplankton
-Producers

Question 5

How are phytoplankton involved with carbon?

Answer 5

Phytoplankton are fixers and transporters of carbon (vectors of carbon)

They fix carbon in the water from the atmosphere and during vertical migrations pr when they die they move carbon from the surface waters to deeper waters

Question 6

What types of marine plankton are there?

Answer 6

Plankton include plants (phytoplankton) and animals (zooplankton)

More than 90% of marine plants are algae.

There are also many planktonic stages early in life for marine species. E.g - polychaete larva, brittle star larve, snail larva and blue crab larva.

Question 7

How can you divide planktonic members?

Answer 7

You can divide plankton on how they feed or whether they are permenant members of the plankton group. Majority larval plankton is temporary. Certainly in zooplankton.

Question 8

What is the definition for phytoplankton?

Answer 8

Photosynthetic protists and plants. Usually single celled or chains of cells.

Question 9

What is the definition for zooplankton?

Answer 9

Non-photosynthetic protists and animals (wide range from single celled to larval fish to large jellyfish. But can’t swim against currents)

Question 10

What is the definition for mesoplankton?

Answer 10

Temporary plankton (zooplankton that spend part of their life in the plankton i.e; larvae of benthos and nekton

Question 11

What is the definition for holoplankton?

Answer 11

Permanent plankton (organisms that spend their whole life as plankton)

Question 12

What is the definition for Neuston?

Answer 12

Plankton that associate with the surface microlayer e.g bacterial films

Question 13

What is the definition for pleuston?

Answer 13

Plankton that live at the surface but protrude into the air e.g portugese manowar

Question 14

Describe the classification of plankton by size

Answer 14

ultraplankton - <2 nanometres

Nanoplankton - 2-20 nanometres

Microplankton - 20-200 nanometres

Macroplankton - 200 nanometres - 2mm

Megaplankton - >2mm

Question 15

What are the advantages of being small like plankton?

Answer 15

-slow rate of sinking (Phytoplankton need light, so are always towards the surface in the shallow waters.

They will sink due to being a higher density of water but it is very slow due to size.)

• rapid regeneration rate (Rapid regeneration is important due to high mortality rate.)
• easy uptake of nutrients

Question 16

Give some examples in the way plankton stay suspended in the water column.

Answer 16

• Density; Regulate ions to make them less dense. Some species produce oils or lipids which help them to be more buoyant reducing density.
• Shape; having appendages reduces drag
• Mobility
• Turbulence; use turbulence in water to move and use structures like flagella or antennae to move within the current.

Question 17

What do settling rates in plankton depend on?

Answer 17

Body size and frictional drag.

A small cell settles slowly - has a large surface area to volume ratio, maximising friction with water.

Question 18

Why do phytoplankton want to stay suspended in the photic zone?

Answer 18

So they can absorb nutrients through the cell wall more easily.