Plankton Flashcards
Define planktonic
Wandering, that which is caused to wander.
Define plankton
Living organisms which drift in the pelagic zones of oceans and bodies of freshwater.
Why are plankton diverse?
There are a wide range of sizes and taxonomic groups.
What are the two broad functional groups of plankton?
Phytoplankton
Zooplankton
What are the features of phytoplankton?
-Predominantly autotrophic (photosynthetic)
-Prokaryotic or eukaryotic algae
-Base of aquatic food chains
What are the features of zooplankton?
-heterotrophic unicellular/multicellular organisms
-transfer energy from phytoplankton to higher trophic levels
What are holoplankton?
Organisms that spend their entire life cycles in the plankton
What are mecroplankton?
Organisms that only spend part of their life cycles in the plankton
What are examples of Megaplankton?
Jellyfish, Ctenophores
Plankton that are >20mm - 2m
What are examples of Macroplankton?
Fish larvae, krill
2-20 mm
What are examples of Mesoplankton?
Copepods, fish eggs
0.2-2mm
What are examples of Microplankton?
Rotifera
20-200um
What are examples of Nanoplankton?
Diatoms, dinoflagellates
2-20um
What are examples of pictoplankton?
Cyanobacteria
0.2-2um
What is an example of Femtoplankton?
Marine viruses
<0.2um
What are the plankton collection methods?
-Bottles
-Pumps
-Nets
Describe the bottle collection method?
In shallow waters, simple weighted bottles or tubes can be used to collect water (and plankton).
Van Dorn design allows sampling at specific depths.
What are the benefits of bottle sampling?
-Easy to operate
-Sampling depths are accurately known
-Sediment or filtration can be used to concentrate plankton from fixed water samples
What are the negatives about bottle sampling?
-Rare plankton are not usually collected
-Does not concentrate plankton
What is the process of net sampling?
Water is pumped on to boat or pier through a filtration net.
What is the benefit of net sampling? (V)
Volume of water filtered can be accurately quantified.
What are the negatives about net sampling?
-Larger zooplankton can be damaged by pumping.
-Not suitable for sampling deeper waters.
What are the benefits of net sampling?
- Quick way of obtaining the sample
- Range of designs from simple to complex
What are the negatives about net sampling?
- Quantification is difficult
- Fishing depth can be hard to control
- Selectivity- net mesh too large
What are the three directions a plankton net tow may be?
Horizontal, oblique and vertical
What is the speed required for horizontal or oblique tows with standard nets?
1.5 to 2.0 knots.
Filtration is less effective and risk of net damage at higher speeds.
When is the best time for horizontal net sampling?
Before dawn, after dusk or at night.
Zooplankton move to deeper layers during daylight hours.
What are depressors used for in net sampling?
Stabilising the net in strong currents.
Why is washing the net after every hauling important?
-Prevents clogging of the net.
- Prevents contamination
What are the closing mechanisms used on nets?
- messengers
- electric
- acoustic
-time
-pressure release mechanisms
What is the benefit of having a closing mechanisms on a net?
It allows to sample at selected depth.
What is a Nansen net?
Single closing net
What is a MOCNESS?
Multiple Opening/Closing Net and Environmental Sensing System.
What is a CUFES?
Continuous underway fish egg sampler
What does a CUFES consist of?
A machine that pumps a sample of water from the top 3 meters of the water continuously while the ship is moving.
A filtration system traps all of the floating fish eggs which are collected and identified on board.
How are fish eggs identified after collection by CUFES?
They can be identified manually or by a camera and image recognition system which also counts the eggs.
What are the types of fixatives for plankton?
-Formaldehyde
-Lugol’s Iodine
What are the methods for quantifying plankton in sample?
- volumetric method
- gravimetric method
- sedimentation chambers
Name the methods used for species identification of plankton samples
- sub-sampling
-using keys
-importance of taxonomic skills - technological aids: automated ID
What are the more specialised design plankton sampling methods?
-Nansen net
- MOCNESS
- Gulf VII sampler
- Bongo net
- Continous underway fish egg sampler