Download Review sheet – Chapters 13 and 14 (Plankton)

Review sheet – Plankton

Understand that plankton refers to drifting organisms within the pelagic zone

Know that phytoplankton are autotrophic (producers) and zooplankton are heterotrophic
(consumers)

Understand that blooms of phytoplankton occur in upwelling regions where cold, nutrient-rich
water is brought up to the photic zone

Know that primary productivity is limited in tropical regions by nutrients (which remain
‘trapped’ beneath a permanent thermocline)

Know that primary productivity is limited in polar regions by sunlight and mixing (sinking)

Know that primary productivity is limited in temperate regions only seasonally: by light (and
mixing) in winter and by nutrients in summer

Know that peak abundance of phytoplankton occurs in spring in temperate regions

Understand that primary productivity is constant year-round in tropical regions (because there
is no seasonality)

Know that net primary productivity is the amount of carbon dioxide removed via photosynthesis
minus the amount of carbon dioxide released by respiration

Understand that the compensation depth is the depth in the water column where the rate of
photosynthesis equals the rate of respiration (net productivity is zero)

Know that phytoplankton will survive above the compensation depth, but will die beneath the
compensation depth

Know that diatoms are the dominant species of phytoplankton and are made up of silica shells

Know that dinoflagellates are also a major group of phytoplankton, but can be autotrophic or
heterotrophic!

Understand that red tides are caused by dinoflagellates

Know that zooplankton are the most numerous consumers in the ocean

Understand that zooplankton are classified as meroplankton – which are only planktonic for part
of their lives, and holoplankton – which are always planktonic

Know that copepods are holoplanktonic crustaceans and are the most abundant of all
zooplankton

Know that zooplankton avoid predation (or try to!) by being translucent (clear), possessing
outward spines and by migrating into and out of the photic zone every night and day,
respectively

Know that zooplankton migrate en masse towards the surface every dusk, and back to the
darker depths at dawn to avoid predation

Understand that this mass migration is referred to as the “deep scattering layer” for its ability to
be detected by echo-sounding equipment as a distinct layer deep in the water column during
the day

Know that Reynold’s number is the measure of inertial forces divided by viscous forces

Know that viscous forces dominate for small organisms such as plankton (if Reynold’s number is
less than 1) and that inertial forces dominate for large organisms (Reynold’s number is greater
than 1)

Understand that phytoplankton have developed adaptations to prevent sinking out of the photic
zone by increasing their surface area via external projections or overall changes in body shape