week 3- planktonic organisms Flashcards
what does benthic mean?
the substrate (mud, rock, sand)
what does pelagic mean?
the water column (the watery bit)
what is Nekton?
Pelagic organisms that can maintain their position against water currents
what is plankton?
Pelagic organisms that cannot maintain their position against currents
what are phytoplankton?
Plant-like (i.e., capable of primary production via photosynthesis)
what are zooplankton?
Animal-like (i.e., derive nutrition by consuming other organisms)
what are the terms to categorize planktonic organisms by size?
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
name the Phytoplanktonic organisms
Diatoms
Dinoflagellates
Coccolithophorids
Cyanobacteria
give some information on cyanobacteria
-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
why is cyanobacteria ecologically important?
- 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
what are coccolithophorid?
The coccolithophorids are single celled eukaryotes (aka protists) capable of photosynthesis
- Coccolithophorids are typically small (<20 µm) and are characterised by calcium carbonate coccoliths
why are Coccolithophorids ecologically important
- Form blooms that look chalky white in open ocean
- Major contribution to calcium carbonate sedimentation
what are diatoms?
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
why are diatoms ecologically important?
- Important food source for zooplankton and larval fish
- On Geological timescales sedimentation of dead
diatoms leads large silica deposits (diatomaceous
earth)
why else are diatoms important?
- Forensics (diagnose location of drowning)
- Diatomaceous earth used as abrasive in toothpaste and polishes, absorbent for nitroglycerin, filtration
of liquids (e.g., beer)
what are Dinoflagellates?
Also single celled eukaryotes. Typically 10- 200 µm and characterised by two whip-like flagella
why are Dinoflagellates ecologically important?
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
name the zooplanktonic organisms?
- Viruses &bacteria (pico-)
- Ciliates, dinoflagellates and metazoan larvae (micro-)
- Copepods (meso-)
- Gelatinous zooplankton (macro-)
what is the difference between zooplanktonic and planktonic organisms?
Whilst the phytoplankton are typically unicellular the zooplankton span microbes to metazoans
explain viruses and bacteria?
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
why are Bacteria are important heterotrophic decomposers
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)
what are Microzooplankton
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
what are ciliates?
- Characterised by ‘hair-like’ cilia on the cell surface associated with movement and feeding
- Important grazers in the marine plankton
what are Mesozooplankton?
- 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
what are coepods?
Copepod crustaceans are the dominant
taxonomic group in the plankton
