phytoplankton Flashcards
what are plankton
Any organisms that live in the water column and are incapable of swimming against a current
what are nekton
able to swim independently of the current
what are Phytoplankton
‘Plants’ – photosynthesisers – producers (major autotrophs at the base of marine foodwebs) - refered to as algae
what are zooplankton
‘Animals’ – consumers – food web
what are mixotrophs
Do a bit of both production and consumption
3 major importances of plankton
Food production
climate change
eutrophication
why is plankton important in food production
- Base of marine food web
- Major role in production of fish stocks, including shellfish – main source of protein
why is plankton important in climate change
- Remove CO2 from surface waters
- Transfer to deep ocean
- Ocean = important sink for atmospheric CO2-
what is the claw hypothesis
1.Phytoplankton create DMS when stressed (ocean warming)
2.DMS dissolves into water and enters atmos to create cloud condensation nuclei
3.Amount of sun that gets into water is reduced – negative feedback loop
why is plankton important in eutrophication
Toxic
Harmful algal blooms
Fish, marine mammal & human mortalities
how did phytoplanktons evolution start
All started in same way with chloroplasts – then organisms developed a different way they are able to photosynthesise
an important group of autotrophic plankton in the ocean
cyanobacteria (formerly called blue-green algae)
what are the two possible morphologies of phytoplankton
unicellular or colonial
how can phytoplankton increase their niches
contain accessory pigments as well as chlorophyll that give them different colors (different in different plankton – determine where they can most effectively live)
6 main phytoplankton groups
Diatoms
Dinoflagellates
Noctiluca
Coccolithophores
Nanoflagellates
Prokaryotes
diatom characteristics
- Bacillariophyceae
- Non-motile
- cellulose cell wall + Silica cell wall (frustule - top bit slides over bottom bit)
- If no mixing -> sink
- Grow well in mixed conditions - High growth rates
- Dominate spring blooms
- Centric diatoms- radial symmetry
- Pennate diatoms- lateral symmetry
- Siliceous frustule - contribute silica to deep-sea sediments
- Many have beautiful ornamentation that can be used in species identification
What kind of symmetry do centric and pennate diatoms have
- Centric diatoms- radial symmetry
- Pennate diatoms- lateral symmetry
diatom reproduction characteristics
Asexual – mitosis
- Large and small bits are generated in the mitosis splitting – if left with the small parts, diatom size will shrink – results in big range of size in species
- When diatoms get too small to undergo biological processes, they use sexual reproduction
dinoflagellate characteristics
- Successful in stratified water
- Migrate: light – nutrients
- Some species toxic
- ~50% heterotrophic
- Possess flagella (hence motility)
- Can tolerate low light level
- Some are mixotrophic; i.e., they can be autotrophic and heterotrophic at the same time
- Some have cellulosic thecate plates in specific number and arrangement that can be used in species identification
Noctiluca characteristics
- Autotrophs - but do feed aswell
- Responsible for biolumenecense
explain how some dinoflagellates and diatoms are responsible for causing Ciguatera Fish Poisoning: CFP
- When fish pick up macroalgae to feed on, they eat these dinoflagellates aswell
- Dinoflagellate toxins will build up in their flesh and be passed to other fish that eat those fish aka fish sold to us
- Can also cause numerous Shellfish Poisonings (PSP, NSP, DSP, ASP) - europe require standard testing for these
Coccolithophores characteristics
- Unicellular phytoplankton covered in coccoliths (made of calcium carbonate)
- Subset of dinoflagellates (still have flagella)
- Prymnesiophyceae
- CaCO3 scales = coccoliths
- A globally significant species = Emiliania huxleyi
Important role in marine carbon + sulphur cycles
Nanoflagellates characteristics
- 2-20 mm
- HNAN (heterotrophic) & PNAN (photosynthetic)
- Prymnesiophytes, chrysophytes, cryptophytes, chlorophytes etc
- Successful in oligotrophic waters - smaller size (+ high surface area:volume ratio) - able to take in the small amounts of nutrients
- Grazed on by protozoan predators
what phytoplankton are prokaryotic
Cyanobacteria
viruses
prokaryote cyanobacteria characteristics
- Formerly called blue-green algae
- Dominate oligotrophic waters
- Prochlorococcus:
smallest phototroph
30-80% PP oligotrophic - Trichodesmium: fix N
- Synechococcus
prokaryote viruses characteristics
- Live off other organisms
- Latch onto cell, inject copies of themselves into cell + take over to make more copies of themselves until they rupture and release them
- Proper recognition: 1990’s
- Small, C & N rich particles
- Infect & lyse specific host organisms
- Cell lyses: divert particulate production of hosts into DOM
- Bacteriophages: impact on bacterial community
what was found in Mesocosm experiments - Bratbak et al. (1992)
- 72% of bacterial production removed by viral lysis
- Loss rate exceeded grazing by flagellates
- Cell lysis resulted in release of proteins, nucleic acids & organic compounds
- After extracellular breakdown: DOM (nutrients) released and available to sustain bact & phyto
Important:
1) May be of quantitative sig: nutrient flow
2) Exert a species specific control: structure food web
