Transcript Plankton_15
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 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 Increasing Depth Every night at dusk, swarms of zooplankton migrate to the surface, and return to depth again at dawn