Plankton Marine life is classified into three groups: Plankton, Nekton, and Benthos Plankton: the drifters Nekton: the active swimmers Benthos: the bottom dwellers

Plankton live in the pelagic zone Benthic

Plankton Plankton refers to the drifting organisms within the pelagic zone Phytoplankton are autotrophic, photosynthetic algae, which form the base of the marine food web Zooplankton are heterotrophic; the primary (and in some cases secondary and tertiary) consumers of the marine food web

‘Bottom’ of the Food Chain

Radiolarian trapping a copepod with its pseudopodia Zooplankton Zooplankton are the most numerous primary consumers in the ocean The most important source of protein in the oceans! Zooplankton eat bacteria, phytoplankton, & other zooplankton! Nearly every major animal phylum is represented in the zooplankton Radiolarian trapping a copepod with its pseudopodia

Zooplankton Zooplankton are classified as either: Holoplankton Meroplankton Holoplankton are always plankton – they live and die in the water column Meroplankton are only plankton for part of their lives; many marine organisms begin their lives as small planktonic organisms, but gain the ability to swim or metamorphose into a benthic organism

Holoplankton http://www.whoi.edu/annualreport02/highlights/globec_en3.html http://www.arcodiv.org/copepod.html Holoplanktonic organisms are ALWAYS planktonic – they live and die in the water column

Meroplankton Meroplanktonic organisms are only planktonic for a part of their lives (usually the beginning) Many marine organisms begin their lives too small to swim against a current, and as such are planktonic! Meroplankton can grow up to become nekton or benthos!

Meroplankton Includes larval (very young) fish, crabs, clams, squid, lobsters, starfish, etc. and jellyfish!

Squid have planktonic, nektonic, and benthic life stages! Squid larvae are meroplankton

Types of Zooplankton: Copepods Copepods are the most abundant of all the zooplankton, typically numbering 70% or more of the plankton community Holoplanktonic Crustaceous Herbivorous, Omnivorous, Carnivorous, and/or Parasitic Marine and freshwater 14,000 species globally

Copepods Important source of protein for secondary consumers! You too can be a copepodologist!!!

Parasitic Copepods http://www.biol.vt.edu/faculty/benfield/freshwater/freshwaterlocked/figures/animals/parasiticcopepods.jpg

Krill Krill are shrimp-like crustaceans that aggregate into huge, dense swarms Often dominate in cold, polar seas Holoplanktonic http://www.krillcount.org/krill.html

Antarctic Krill Critically important food source for fish, seabirds, seals, penguins, and whales Antarctic krill live for up to 7 years and survive in crevices beneath sea ice, feed on ice algae Global warming and overfishing are major threats to krill, and the Antarctic ecosystem

Crabeater seals have specialized teeth for feeding on krill

Pteropods: Planktonic snails

Pteropods Pteropods are Molluscs (planktonic snails) Holoplanktonic Many possess a shell, while others are “naked” Shelled pteropods create a mucus-laced feeding web to trap detritus Naked (shell-less) pteropods are predatory and feed on other (shelled) pteropods

Pteropods Shelled pteropods are called “sea butterflies” Naked pteropods are called “sea angels” Growing concern over fate of shelled pteropods with increasing ocean acidification Sea angel Sea butterflies

Gelatinous Zooplankton

Gelatinous Zooplankton: “Jellyfish” Jellyfish typically refer to members of the Phylum Cnidaria; benthic polyp stage, meroplanktonic Planktonic Cnidarians are drifting animals with nematocysts, or stinging cells

Jellyfish Life Cycle

Gelatinous Zooplankton: Ctenophores Ctenophores are not Cnidarians – belong to the Phylum Ctenophora (“comb-bearer”); holoplanktonic Voracious predators of other zooplankton Sticky cells, not stinging cells!

Gelatinous Zooplankton: Salps Salps are relatives of sea squirts, or tunicates Salps are herbivores, filter phytoplankton out of the water column with a mucus net (yum!) Holoplanktonic Sinking fecal pellets remove carbon from the surface waters (Carbon pump)

Chaetognaths: Arrow worms Chaetognaths are predatory marine worms Feed largely on copepods Distinctive phylum; “hair jaws” Holoplanktonic Copepod (i.e., “lunch”)

The biggest zooplankton of them all The oceanic sunfish, Mola mola, is actually considered by many to be planktonic, since it swims weakly and may not be able to swim against a strong current Largest of the bony fish grows to 5,000 lbs Common off Long Island in summer http://www.q-divebali.com/info.html

Staying Afloat In order to avoid sinking out of the pelagic zone, organisms employ numerous adaptations for staying afloat These include: Increased Resistance: The greater the surface area, the greater the drag or resistance Increased Buoyancy: Gas-filled bladders or floats, lipid storage

http://www.freakingnews.com/Jellyfish-Parachute-Pics-10690.asp

The Greatest Migration on Earth Every night at dusk, swarms of zooplankton migrate to the surface, and return to depth again at dawn Increasing Depth