Classification of plankton, Plankton diversity and Productivity. Two groups of organisms inhabit the oceanic zone: plankton and nekton Based on productivity, biomass, abundance and diversity, plankton far outweighs nekton in open ocean Plankton can be classified into logical groups based on: Taxonomy Motility Size Life history Spatial distribution

1. Plankton diversity and
Productivity, Classification of
plankton
Presentation by
C. Raja Samanth

2. Introduction
• Plankton range widely in size, taxonomic
diversity, and life style.
• Phytoplankton are the primary producers in
food web, and their productivity is limited
by the scarcity of nutrients.

3. • Bacteria provide a second base to food
webs, and they allow the scarce nutrients to
be efficiently recycled.
• Limited primary production and food webs
with several energy-wasting steps limit the
number of large animals.

4. • Gelatinous plankton such as ctenophores
play significant roles in open-ocean
ecosystems.
• Because of their efficient feeding
mechanisms, reduction of nutritional
quality, and provision as prey for specialist
carnivores.
• Several structural features and behaviors
have evolved to keep afloat organisms that
are not strong swimmers.

5. Classification of plankton
• Two groups of organisms inhabit the oceanic zone: plankton and
nekton
Based on productivity, biomass, abundance and diversity,
plankton far outweighs nekton in open ocean
• Plankton can be classified into logical groups based on:
Taxonomy
Motility
Size
Life history
Spatial distribution

6. Taxonomic groups
• Seston: particles suspended in the sea, include:
• Tripton: non-living seston
• Phytoplankton: primary producers
• Zooplankton: heterotrophic eukaryotic microbes that float
in the currents
• Bacterioplankton: archaeans and bacteria
• Viriplankton: free viruses (the most abundant plankton of
all)

7. Motility
• Akinetic: plankton that don’t move at all, e.g., viruses,
diatoms and forms
• Kinetic: plankton that can move (include majority of
plankton)
• Kinetic plankton move by use of flagella, jet propulsion,
undulation, swimming appendages

8. Size
• Original scheme (based on visibilty and collection
method):
– macroplankton – visible to the naked eye
– microplankton – caught with standard plankton net
– nanoplankton – concentrated by centrifugation
• Newer classifications: femtoplankton, picoplankton,
mesoplankton, macroplankton, megaplankton

10. Life history
• Holoplankton: organisms that are planktonic throughout
their lives, e.g., microbes, arrowworms, salps,
siphonophores, comb jellies, copepods, krill
• Meroplankton: planktonic larvae that will grow into
non-planktonic organisms
– in open ocean would include larvae of nektonic fish
and squid
– in coastal waters would also include larvae of
benthic invertebrates

11. Spatial distribution
• Neritic: distinguished by presence of meroplankton
and diverse diatoms
• Oceanic: less diverse in diatoms and invertebrate
meroplankton; more salps, larvaceans, arrowworms
and sea butterflies
• Neuston: plankton that life close to the water’s
surface
• Pleuston: plankton which break the surface of the
water with their gas bladders or bubbles, e.g., by-
the-wind sailor

12. • Megaplankton
– most organisms classified as megaplankton are animals
– cnidarian zooplankton
• largest members of the plankton are jellyfishes

14. Patchiness
Plankton occur in patches (localized aggregations), often around
upwellings
Patchiness can be caused by:
• upwelling
• localized variations in sea surface conditions
• vertical mixing
• downwelling
• waters of different densities coming together
• grazing by zooplankton

15. Ecology of the Open Sea
• Open sea is a pelagic ecosystem—one in which the inhabitants
live in the water column basis of food chain is many species of
small phytoplankton
• Small, primary producing organisms have a relatively high
surface area allows them to absorb more nutrients from
surrounding seawater
• Majority of herbivores in open ocean are zooplankton which
supply food for nekton

16. Productivity
– All higher forms of life rely on plankton
– Water near the surface receives plenty of sunlight, but few
nutrients from land or the sea bottom (except in rare areas
of upwelling)
– Phytoplankton productivity is low in tropical waters
• arrangement of water in layers with little circulation
between prevents nutrients from being brought from the
sea bottom
• low phytoplankton numbers support even fewer
numbers of zooplankton

17. Food web
Basis of food webs in open sea is formed by phytoplankton
and heterotrophic bacteria
Dissolved and particulate organic matter
• phytoplankton release photosynthetic products as DOM
into surrounding seawater
• heterotrophic bacteria recycle DOM as they eat it and then
are eaten by nanoflagellates
• bacterial loop: process in which bacteria metabolize DOM
and return it to the water in an inorganic form available to
phytoplankton
• lysis of bacteria by viruses releases DOM and particulate
organic matter (POM)

18. Dissolved
inorganic
nutrients
Shark
Squid
Tuna
Herring Ctenophores
Dolphin
Toothed
whale
Leatherback
turtle
Baleen whale
Jellyfish
Sardines
Tintinnids
Heterotrophic
nanoflagellates
Particulate organic
matter
Viruses
Dissolved
organic
matter
Free
heterotrophic
bacteria
(to deeper waters)
Meso- and
Microzooplankton
Phytoplankton
Stepped Art
Figure 17- 17, p. 481

19. Macrozooplankton (krill, shrimp)
Nanoplankton
(cyanobacteria,
small diatoms)
Microzooplankton
(foraminiferans, radiolarians)
Mesozooplankton
(copepods)
Nekton (fishes, squid, whales)
Phytoplankton (nanoplankton and smaller)
Mesozooplankton
Macrozooplankton
Large and medium
fishes, squid
Small fishes
Phytoplankton (nanoplankton and smaller)
Large and medium
fishes, squid
Microzooplankton
Mesozooplankton
Macrozooplankton
Small fishes
Microzooplankton
Stepped Art
Figure 17- 18, p. 482

20. • Food webs in the open sea (continued)
– efficiency of open-ocean food webs
• pyramid of production = diagram that indicates the rate
at which new biomass is produced at successive trophic
levels
• standing crop = amount of biomass of organisms in a
given area at a given time
• standing crop of phytoplankton in open ocean might be
very small, giving a pyramid of production that is partly
inverted
• The wealth of the open sea resides in its microscopic
inhabitants

21. Thank you