1. Plankton

2. Marine life 3 categories:
Benthos: bottom dwellers; sponges, crabs
Nekton: strong swimmers- whales, fish, squid
Plankton: animal/plants that drift in water. The have little control over their movement.
Includes: diatoms, dinoflagellates, larvae, jellyfish, bacteria.

3. What physical factors are plankton subject to?
Waves
Tides
Currents

4. Plankton classified by:
Size
Habitat
Taxonomy

5. Size: Picoplankton (.2-2 µm) bacterioplankton
Nanoplankton ( µm) protozoans
Microplankton ( µm) diatoms, eggs, larvae
Macroplankton (200-2,000 µm) some eggs, juvenile fish
Megaplankton (> 2,000 µm) includes jellyfish, ctenophores, Mola mola

6. Habitat: Holoplankton- spends entire lifecycle as plankton
Ex. Jellyfish, diatoms, copepods
Meroplankton- spend part of lifecycle as plankton
Ex. fish and crab larvae, eggs
lobster
snail
fish

7. Habitat: Pleuston- organisms that float passively at the seas surface
Ex. Physalia, Velella
Neuston – organisms that inhabit the uppermost few mm of the surface water
Ex. bacteria, protozoa, larvae; light intensity too high for phytoplankton
Neuston net

8. Taxonomy

9. Blooms: High nutrients Upwelling Seasonal conditions
Phytoplankton- restricted to the euphotic zone where light is available for photosynthesis.
Blooms:
High nutrients
Upwelling
Seasonal conditions

10. Some important types of phytoplankton
Diatoms: temperate and polar waters, silica case or shell
Dinoflagellates: tropical and subtropical waters.... also summer in temperate
Coccolithophores: tropical, calcium carbonate shells or "tests"
Silicoflagellates: silica internal skeleton... found world wide, particularly in Antarctic
Cyanobacteria (blue-green algae): not true algae, often in brackish nearshore waters and warm water gyres
Green Algae: not common except in lagoons and estuaries
Some important types of phytoplankton
Diatoms: Phylum Chrysophyta Dominant in temperate and polar waters Silica case or shell looks like a "pill box“; Found singly or in chains; Planktonic forms are radially symmetrical
Can reproduce very quickly, up to 6x/day via asexual reproduction (also have sexual reproduction)
Dinoflagellates
Dominant in tropical and subtropical waters.... also summer in temperate areas they have two flagella and a shell of cellulose plates (called theca)
Asexual reproduction and fast population growth can lead to "red tides"
They secrete a neurotoxin called saxitoxin: bioaccumulates in shell fish and other filter feeders... can be fatal
Coccolithophores
Tropical... often very common Calcium carbonate shells or "tests"
Their skeletons make important depositional structures, but "naked" forms are not preserved
Silicoflagellates: Biflagellated, silica internal skeleton... found world wide, particularly in Antarctic Cyanobacteria: "Blue-green algae" but not true algae: often in brackish nearshore waters and warm water gyres these bacteria can fix gaseous nitrogen into NH4
Green Algae
Not common except in lagoons and estuaries... often associated with coastal pollution Cryptomonad Flagellates: have chlorophyll a and c... adapted for turbid waters

11. Some important types of zooplankton
Crustaceans: Copepods
Krill
Cladocera
Mysids
Ostracods
Jellies
Coelenterates (True jellies, Man-of-wars, By-the-wind-sailors)
Ctenophores (comb jellies)
Urochordates (salps and larvacea)
Worms (Arrow worms, polychaetes)
Pteropods (planktonic snails)

12. Chaetognath

13. Copepod

14. Fish larvae

15. tunicate
Jelly-like house
Oikopleura
Marine snow

16. Marine snow

17. Zooplankton: larvae, copepods. Some produce oil to help them float
Zooplankton: larvae, copepods. Some produce oil to help them float. Smaller population size than the phytoplanktoton. Zooplankton population size increases after phytoplankton size increases.
zooplankton
phytoplankton
Winter Spring Summer Fall

18. Nutritional modes of zooplankton:
Herbivores: feed primarily on phytoplankton
Carnivores: feed primarily on other zooplankton (animals)
Detrivores: feed primarily on dead organic matter (detritus) 
Omnivores: feed on mixed diet of plants and animals and detritus

19. Diurnal vertical migration

20. Vertical Migration

21. Diel vertical Migration
Each species has its own preferred day and night depth range, which may vary with lifecycle.
Nocturnal Migration
single daily ascent near sunset
Twilight migration (crepuscular period)
two ascents and two descents
Reverse migration
rise during day and descend at night

22. Advantages for Diurnal vertical migration
An antipredator strategy; less visual to predators
Zooplankton migrate to the surface at night and below during the day to the mesopelagic zone. Copepods avoid euphasiids which avoid chaetognaths.

23. Advantages for DVM Energy conservation Encounter new feeding areas
Get genetic mixing of populations
Hastens transfer of organic material produced in the euphotic zone to the deep sea

24. Plankton Patchiness Zooplankton not distributed uniformly or randomly
Aggregated into patches of variable size
Difficult to detect with plankton nets
- Nets “average” the catch over the length of the tow
May explain enormous variability in catches from net tows at close distances apart
Plankton Patchiness
In the ocean, zooplankton do not occur evenly or randomly. The are aggregated into patches that occur in both the horizontal and vertical.
These patches may be a few centimeters in scale or s of kilometers.
Traditional sampling tools do a poor job of detecting this patchiness because they average the catch over the length of the tow.
This patchiness may explain why there is so much variability in repeated net tows taken in close proximity to each other.