ZOOPLANKTON Flashcards
What are zooplankton?
- animals that are severely limited in their ability to overcome ocean currents and drift
Distinguish between holoplankton and meroplankton
HOLO - do this for all of their life
MERO - subset of life history stages
SIZE
- v v small
- 0.5mm to 15mm
ACTIVITY LEVELS
- some simply drift in currents
- can control depths, many make vertical migrations
Why vertically migrate?
1) Predator avoidance hypothesis
2) energy conservation hypothesis
- colder waters
3) current exploitation hypothesis
- allow water to refreshed
Issues with predator avoidance hypothesis
still enough light for vision; bioluminescence, too deep
Issues with energy conservation hypothesis
not held up by lab experiments
Why is current exploitation hypothesis fairly accurate?
supported by patchiness of phytoplankton and zooplankton
DISTRIBUTION
- mostly concentrated in photic zone because there will be lots of photosynthesising prey
How do zooplankton remain buoyant?
1) add lighter-than-water material (gas, oil, fat)
2) replace heavier ions with lighter ones
eg. SO4- with Cl-
3) Increase surface area to volume ratio
(overall size, be flat, make projections)
2 different forms for zooplankton to avoid predation
- PASSIVELY
- using spines
- transparency
- spines
- appendages to increase apparent size - ACTIVELY
- using nematocysts
What are copepods? What are their lifecycles?
form of crustacean, the most abundant zooplankton
- graze bloom forming phytoplankton
- only adults at ocean surface
- development occurs at depth
Give an example of a meroplankton
A jellyfish (Class Scyphozoa/ Phylum Cnidaria)
Define larvae
Independent entities that develop from fertilised eggs and must undergo a drastic morphological change in order to become the adult form
1) Example of herbivorous larvae
2) Example of carnivorous larvae
1) The veliger larvae of a marine snail
2) The zoea larvae of a shore crab
Why have planktonic larvae?
- advantageous feeding + growth as planktonic environments are nutrient rich
- dispersal to new settling areas
- reduces competition intraspecifically
- increases species gene flow
3 sources of primary production
1) phytoplankton (single celled algae)
2) macroalgae on shore
3) chemosynthetic bacteria
What to phytoplankton provide energy for?
- pelagic communities
- shallow water benthic communities
- deep sea communities
give an equation for primary production
primary production = light and warmth + inorganic nutrients
Define Thermocline, a high one means what in terms of nutrient content…
Steep density gradient
- low nutrients, eg. when temp and light levels are high
- hence why algae bloom in spring
Zooplankton predictions
- Zooplankton no. will increase to take advantage of _____
- Decreases in phytoplankton will lead to a decrease in _____
- More species will produce planktonic larvae where…
- increase in primary productivity
- zooplankton
- phytoplankton production is predictable
What are the largest zooplankton?
scyphozoa, jellyfish
