Zooplankton

Question 1

What are meroplankton and what are the advantages?

Answer 1

Meroplankton are species that have part of their lifecycle in the planktonic stage.

Approx. 80% benthic species have a larval stage. Some stay in the planktonic stages for weeks or months depending in advantageous conditions of the species.

Benefits of small planktonic stage – develop to sexual maturity faster, drift further from colonies

Question 2

What are some of the adaptations in the blue crab larva?

Answer 2

See through, can’t be seen.

Star shape to stop settling.

In early larval stages (top right) large spines stops predation from smaller predators.

Question 3

What are some of the adaptations in larval fish?

Answer 3

Yolk sac

Transparancy

Fish eggs have lipids and oils to aid buoyancy

Question 4

What are the two larval stages of a crab?

Answer 4

Megalopa – later laval crab stage

Zoeal – early larval crab stage

Question 5

List categories of holoplankton (permanant residents) in terms of their size

Answer 5

Smallest - protists (micro-organisms)

Medium - Chaetognatha/arrow worms (1-4cm)

Large - Comb jellies, jellyfish (many metres wide and long)

Question 6

Give examples of two gelatinous zooplankton

Answer 6

medusa and siphonophore

Question 7

Give some examples of holoplankton

Answer 7

Portugese man o war – colonial hydroid, class next to jellyfish. Gas bladder projects above the water – neuston category

Moon jellyfish

Teptroptimous – long antennae and chaete

Copepods

Question 8

What are some adaptations of arrow worms?

Answer 8

Strong hooks around the mouth to catch prey.

Good at picking up vibration in the water

Question 9

What are some adaptations of Ctenophores?

Answer 9

Cone rows of scilia

Trailing tentacles with adhesive cells to catch prey – often copepods.

Question 10

What species dominates the plankton group?

Answer 10

The copepods make up 70% of net-collected plankton.

Question 11

Describe the body organisation of the Copepods

Answer 11

Head and first body segment are fused together and contain antennae and mouth parts.

Body segment contains swimming legs and lastly the tail which has no appendages.

Question 12

How do copeppods feed?

Answer 12

Antennae swoop once food is deteced on the hairs of the antennae bringing in water and maxillipeds make a circular movement grabbing food with maxillary setules.

Diet preference; two celled chains to single cells and prefer larger diatoms.

Question 13

Why do zooplankton undertake a diurnal vertical migration, ascending to surface at dusk and descending to depths at dawn?

Answer 13

• Avoid strong uv radiation
• allow phytoplankton to recover
• avoid predation
• conserve energy
• optimal foraging

Question 14

What is the match/mismatch hypothesis and who proposed it?

Answer 14

D.H Cushing proposed the hypothesis.

He noted that climatic factors control the timing and strength of phytoplankton blooms which affects zooplankton feeding and larval fish.

‘Mismatch’ phytoplankton blooms occur earlier/later/reduced than expected.

Question 15

What affects can be caused due to phytoplankton mismatch?

Answer 15

When zooplankton and phytoplankton align, you get very good fish stocks. However if PP blooms earlier or later than zooplankton alignment, fish stocks tend to be strongly influenced by timing of prey. Not only for prey but for food for fish offspring.

Plankton mismatch means that prey can differ in size and species which can affect those dependant on them for food.