week 3- planktonic organisms

Question 1

what does benthic mean?

Answer 1

the substrate (mud, rock, sand)

Question 2

what does pelagic mean?

Answer 2

the water column (the watery bit)

Question 3

what is Nekton?

Answer 3

Pelagic organisms that can maintain their position against water currents

Question 4

what is plankton?

Answer 4

Pelagic organisms that cannot maintain their position against currents

Question 5

what are phytoplankton?

Answer 5

Plant-like (i.e., capable of primary production via photosynthesis)

Question 6

what are zooplankton?

Answer 6

Animal-like (i.e., derive nutrition by consuming other organisms)

Question 7

what are the terms to categorize planktonic organisms by size?

Answer 7

Mega-plankton 20 cm +
Macro-plankton 2cm – 20 cm
Meso-plankton 200 µm - 2cm
Micro-plankton 20-200 µm
Nano-plankton 2 - 20 µm
Pico-plankton 0.2 - 2 µm

Question 8

name the Phytoplanktonic organisms

Answer 8

Diatoms
Dinoflagellates
Coccolithophorids
Cyanobacteria

Question 9

give some information on cyanobacteria

Answer 9

-The cyanobacteria capable of photosynthesis and are
typically <1 to ~5 µm in size
- Many can use N2 gas as a source of nitrogen (i.e., they
‘fix nitrogen’)
- Cyanobacteria can occur as single cells, filaments, or
colonies

Question 10

why is cyanobacteria ecologically important?

Answer 10

• The dominant primary producer in the oceans
• Many are food for small zooplankton
• Some are toxic, and if they bloom they can impact whole ecosystems

Question 11

what are coccolithophorid?

Answer 11

The coccolithophorids are single celled eukaryotes (aka protists) capable of photosynthesis
- Coccolithophorids are typically small (<20 µm) and are characterised by calcium carbonate coccoliths

Question 12

why are Coccolithophorids ecologically important

Answer 12

• Form blooms that look chalky white in open ocean
• Major contribution to calcium carbonate sedimentation

Question 13

what are diatoms?

Answer 13

The diatoms are single celled eukaryotes (aka a protist) capable of photosynthesis
* Diatoms are typically 5- 200µm and fast growing (1-3
generations per day)
* Characterised by producing a silica ‘box’ around the cell The silica box is composed of two halves called ‘valves’ or ’frustules’
* Diatoms can also occur as single cells or chains

Question 14

why are diatoms ecologically important?

Answer 14

• Important food source for zooplankton and larval fish
• On Geological timescales sedimentation of dead
  diatoms leads large silica deposits (diatomaceous
  earth)

Question 15

why else are diatoms important?

Answer 15

• Forensics (diagnose location of drowning)
• Diatomaceous earth used as abrasive in toothpaste and polishes, absorbent for nitroglycerin, filtration
  of liquids (e.g., beer)

Question 16

what are Dinoflagellates?

Answer 16

Also single celled eukaryotes. Typically 10- 200 µm and characterised by two whip-like flagella

Question 17

why are Dinoflagellates ecologically important?

Answer 17

Some are phytoplankton, some zooplankton, some
are both (called mixotrophy)
* Can eat smaller cells and are food for larger
zooplankton
* Can form harmful blooms Bloom forming species can cause disease in wildlife and humans, e.g., Pfiesteria hysteria causes skin lesions and mass mortality in
many fish species

Question 18

name the zooplanktonic organisms?

Answer 18

• Viruses &bacteria (pico-)
• Ciliates, dinoflagellates and metazoan larvae (micro-)
• Copepods (meso-)
• Gelatinous zooplankton (macro-)

Question 19

what is the difference between zooplanktonic and planktonic organisms?

Answer 19

Whilst the phytoplankton are typically unicellular the zooplankton span microbes to metazoans

Question 20

explain viruses and bacteria?

Answer 20

Viruses are the most abundant ‘life form’ in the
ocean (estimated 1030 viruses)
* Every second, approximately 1023 viral infections occur in the ocean
* Major source of mortality and disease in organisms from phytoplankton to whales

Question 21

why are Bacteria are important heterotrophic decomposers

Answer 21

Bacteria are important heterotrophic decomposers
(although the cyanobacteria are important autotrophs)
* Bacteria play a critical role in major element cycles (e.g., the carbon and nitrogen cycles)

Question 22

what are Microzooplankton

Answer 22

Small metazoan and protozoa (i.e., heterotrophic unicellular eukaryotes) form a critical link in marine food webs
* Consume bacteria and nano-phytoplankton
* Feed mesozooplankton & larval fish

Question 23

what are ciliates?

Answer 23

• Characterised by ‘hair-like’ cilia on the cell surface associated with movement and feeding
• Important grazers in the marine plankton

Question 24

what are Mesozooplankton?

Answer 24

• The mesozooplankton are exclusively metazoan (i.e.,
  animals)
• Most animal phyla are represented in plankton,
  but one dominant group
• Copepods are small crustaceans and account for
  ~95% of the planktonic biomass

Question 25

what are coepods?

Answer 25

Copepod crustaceans are the dominant
taxonomic group in the plankton