1. Plankton and Plankton Communities
MARE 444 Lecture 1

2. Plankton Nekton - Move against prevailing water currents
Plankton - Free floaters of the world
Phytoplankton - Free floating plants, primary producers
Bacterio - Free floating bacteria
Viro - Free floating viruses
Myco - Free floating fungi
Zooplankton - Free floating animals
(herbivores & carnivores)
Proto - Free floating single-celled animals
Meta - Free floating multi-cellular animals

3. Terms and Size Classes Meroplankton -Part-time free floaters
e.g. crustacean, fish larvae
Haloplankton -Free float entire life
e.g. diatoms, copepods, ctenophores

4. Megaplankton Macroplankton Mesoplankton Microplankton Nanoplankton
Net Plankton
Microplankton
Nanoplankton
“Microbial Loop”
Picoplankton

5. Phytoplankton Diatoms Dinoflagellates Coccolithophores Silicon dioxide
glass “pill boxes” (single & chains)
Dominate coastal waters (cold waters)
Planktonic & benthic
Coscinodiscus Chaetoceros
Dinoflagellates
No external skeleton of silicon
Mostly solitary (chains rare)
Photosynthetic, parasitic, grazer, symbiotic
Proportions increase offshore; blooms
Ceratium Peridinium
Coccolithophores
Tropical, pelagic
CaC03 plates
Coccolithus

6. Phytoplankton Cyanobacteria “blue-green algae”
dominate brackish, nearshore waters
often undergo nitrogen fixation
N is converted to NH4+
Tricodesmuim
Silicoflagellates
unicellular and biflagellate
chloroplasts, internal silica skeleton
less abundant than diatoms
high in Antarctic and open ocean
Isochrisis
Chlorophytes
true green algae
rare in marine waters
often dominate estuaries and lagoons
Chlamydomonas colony

7. I’m Spatial

8. The Temp

9. Life in the open ocean: sinking in the drink!
A particle will remain suspended in seawater:
Less dense than seawater
Shape that  drag
It can swim
Water turbulence keeps it suspended
Density of most plankton > seawater…..sink!
Negative effect: beneath light penetration (photosynthesis)
Positive effect: nutrients (regulate biochemcial composition

10. Staying afloat Principles of density and viscosity:
Water density a function of: Temparature & Salinity
Viscosity as Temparature and Salinity
Principal of shape:
objects of ~ weight but different shapes fall at different rates; fall rate related to the amount of resistance shape offers
More surface area ~ more resistance to sinking
Surface area increases as square of linear dimension of the object

11. Buoyancy more important in areas of higher temp and salinity
Smaller objects with same shape have larger SVR

12. Reducing Density Change composition of body fluids
replace heavy ions with light ions (= solute conc)
NH4Cl (ammonium chloride)
Physalia
Gas-filled floats (gas < water)
Excess food as oil droplets under carapace
Incorporate low density body fluids
Oils & Fats (food reserves)

13. Surface Area To Volume Ratio

14. Reducing Surface Resistance
Small body size = (high SVR)
Change shape….flatten or add spines/body projections
Small size….more important in tropics???

15. Floating and Water Movement
Day
Night
Surface waters
Heats
Cools
Alternating heating/cooling--convection cells
Langmuir Convection Cells
Creation of vortices caused by wind driven movement
Wind induced
Plankton may be caught in convergence zones
Small units of water
either sinking or rising

16. Patchiness of the Plankton
Plankton are extremely patchy…more frequently
together than expected by chance
Net tow
Why?
1) Spatial changes in physical conditions (T, S, Light)
2) Current transport & water turbulence (Langmuir converg)
3) Grazing activity (or lack of)
4) Localized reproduction
5) Social aggregating behavior (Deep scattering layer)

17. Patchiness of the Plankton
However…difficult to quantify
Net tow
Result