Zooplankton

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Zooplankton
http//www.microscopy-uk.org.uk
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Planktos drifts in greek

• Their distribution depends on currents and gyres
• Certain zooplankton can swim well, but
  distribution controlled by current patterns
• Zooplankton all heterotrophic plankton except
  bacteria and viruses size range from 2 µm
  (heterotrophic flagellates, protists) up to
  several meters (jellyfish)

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Herbivorous zooplankton Grazers
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Nutritional modes in zooplankton

• Herbivores feed primarily on phytoplankton
• Carnivores feed primarily on other zooplankton
  (animals)
• Detrivores feed primarily on dead organic matter
  (detritus) 
• Omnivores feed on mixed diet of plants and
  animals and detritus

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Feeding modes in Zooplankton

• Filter feeders
• Predators catch individual particles

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Filter Feeder
Copepod
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Filter Feeder
Ctenophore
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Predator
Chaetognath Arrow Worm
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Life cycles in Zooplankton

• Holoplankton spend entire life in the water
  column (pelagic)
• Meroplankton spend only part of their life in
  the pelagic environment, mostly larval forms of
  invertebrates and fish
• Ichthyoplankton fish eggs and fish larvae

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Holoplankton
Copepods Planktonic crustaceans
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Barnacles benthic sessile crustacean
http//science.whoi.edu/labs/pinedalab/
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Meroplankton
Nauplius larva
http//www.microscopy-uk.org.uk
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Meroplankton
Cypris larva
http//www.microscopy-uk.org.uk
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http//science.whoi.edu/labs/pinedalab/
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Cypris larva and metamorphosed juveniles
http//science.whoi.edu/labs/pinedalab/
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Barnacle population regulation
http//science.whoi.edu/labs/pinedalab/
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Ichthyoplankton
Gadidae Gadus morhua
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Gadidae Gadus morhua
Ichthyoplankton
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Gadidae Gadus morhua
Ichthyoplankton
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Gadidae Atlantic cod Gadus morhua
Demersal Adult
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Protists Protozooplankton

• Dinoflagellates heterotrophic relatives to the
  phototrophic Dinophyceae naked and thecate
  forms. Noctiluca miliaris up to 1 mm or bigger,
  bioluminescence, prey on fish egg zooplankton
• Zooflagellates heterotrophic nanoflagellates
  (HNF) taxonomically mixed group of small, naked
  flagellates, feed on bacteria and small
  phytoplankton choanoflagellates collar around
  flagella
• Foraminifera relatives of amoeba with calcareous
  shell, which is composed of a series of chambers
  contribute to ooze sediments 30 µm to 1-2 mm,
  bacteriovores most abundant 40N 40S

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Dinoflagellates Noctiluca miliaris
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Colonial choanoflagellates Bacteriofages (Ross
Sea)
http//www.nsf.gov/pubs/1999/nsf98106/98106htm/ht-
015.gif
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Foraminifera (calcareous all latitudes)
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Protists Protozooplankton

• Radiolaria spherical, amoeboid cells with silica
  capsule 50 µm to several mm contribute to
  silica ooze sediments, feed on bacteria, small
  phyto- and zooplankton cold water and deep-sea
• Ciliates feed on bacteria, phytoplankton, HNF
  naked forms more abundant but hard to study
  (delicate!) tintinnids sub-group of ciliates
  with vase-like external shell made of protein
  herbivores

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Figure 3.21b
Radiolarians (siliceous low latitudes)
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http//www.jochemnet.de/fiu/
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Live Radiolarian
http//www-odp.tamu.edu/public/life/199/radiolaria
.jpg
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Invertebrate Holoplankton

• Cnidaria primitive group of metazoans some
  holoplanktonic, others have benthis stages
  carnivorous (crustaceans, fish) long tentacles
  carry nematocysts used to inject venoms into
  prey box jellyfish of Australia kills humans
  within minutes
• Medusae single organisms, few mm to several
  meters
• Siphonophores colonies of animals with
  specialization feeding polyps, reproductive
  polyps, swimming polyps Physalia physalis
  (Portuguese man-of-war), common in tropical
  waters, Gulf of Mexico, drifted by the wind and
  belong to the pleuston (live on top of water
  surface)

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Cnidaria (medusae)
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Cnidaria (medusae)
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Cnidaria (siphonophora)
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Invertebrate Holoplankton

• Ctenophores separate phylum, do not belong to
  Cnidaria transparent organisms, swimm with fused
  cilia no nematocysts prey on zooplankton, fish
  eggs, sometimes small fish important to
  fisheries due to grazing on fish eggs and
  competition for fish food
• Chaetognaths arrow worms, carnivorous, lt4 cm
  Polychaets Tomopteris spp. only important
  planktonic genus

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Ctenophora (comb jellies)
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Ctenophora (comb jellies)
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Invertebrate Holoplankton

• Mollusca 
• Heteropods small group of pelagic relatives of
  snails, snail foot developed into a single fin
  good eyes, visual predators
• Pteropods snail foot developed into paired
  wings suspension feeder produce large mucous
  nets to capture prey carbonate shells produce
  pteropod ooze on sea floor

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Heteropod (Predates on Ctenophores)
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Pteropod

• http//www.mbari.org/expeditions/

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Protochordate Holoplankton

• Appendicularia group of Chordata, live in
  gelatinous balloons (house) that are periodically
  abandoned empty houses provide valuable carbon
  source for bacteria and help to form marine snow
  filter feeders of nanoplankton
• Salps or Tunicates group of Chordata, mostly
  warm water typically barrel-form, filter
  feeders occur in swarms, which can wipe the
  water clean of nanoplankton large fecal bands,
  transport of nano- and picoplankton to deep-sea
  single or colonies

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Appendicularia
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Pelagic Salps
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Arthropoda crustacean zooplankton

• Cladocera (water fleas) six marine species
  (Podon spp., Evadne spp.), one brackish water
  species in the Baltic Sea fast reproduction by
  parthenogenesis (without males and egg
  fertilization) and pedogenesis (young embryos
  initiate parthenogenetic reproduction before
  hatching)
• Amphipoda less abundant in pelagic environment,
  common genus Themisto frequently found on
  siphonophores, medusae, ctenophores, salps
• Euphausiida krill 15-100 mm, pronounced
  vertical migration not plankton sensu strictu
  visual predators, fast swimmers, often
  undersampled because they escape plankton nets
  important as prey for commercial fish (herring,
  mackerel, salmon, tuna) and whales (Antarctica)

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Amphipoda
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Amphipoda (parasites of gelatinous plankton)
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• http//www.imagequest3d.com/catalogue/deepsea/imag
  es/l038_jpg.jpg

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Euphasids (krill)
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Arthropoda crustacean zooplankton

• Copepoda most abundant zooplankton in the
  oceans, insects of the sea herbivorous,
  carnivorous and omnivorous species
• Calanoida most of marine planktonic species
• Cyclopoida most of freshwater planktonic species
  
• Harpacticoida mostly benthic/near-bottom species
  
• Copepod development first six larval stages
  nauplius (pl. nauplii), followed by six copepodit
  stages (CI to CVI)
• Tropical species distinct by their long antennae
  and setae on antennae and legs (podi)

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Copepods
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http//www.jochemnet.de/fiu/
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Common Meroplankton

• Mollusca clams and snails produce shelled
  veliger larvae ciliated velum serves for
  locomotion and food collection
• Cirripedia barnacles produce nauplii, which turn
  to cypris 
• Echinodermata sea urchins, starfish and sea
  cucumber produce pluteus larvae of different
  shapes, which turn into brachiolaria larvae
  (starfish) metamorphosis to adult is very
  complex
• Polychaeta brittle worms and other worms produce
  trochophora larvae, mostly barrel- shaped with
  several bands of cilia

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Common Meroplankton

• Decapoda shrimps and crabs produce zoëa larvae
  they turn into megalopa larvae in crabs before
  settling to the sea floor
• Pisces fish eggs and larvae referred to as
  ichthyoplankton fish larvae retain part of the
  egg yolk in a sack below their body until mouth
  and stomach are fully developed

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Meroplankton
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Meroplanktonic Larvae

• Planktotrophic
• Feeding larvae
• Longer Planktonic Duration Times
• High dispersal potential
• Lecithotrophic (non-feeding)
• Non-feeding larvae
• Shorter planktonic Duration Times
• Low dispersal potential

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Molluscs Meroplankonic Veliger
larvae PLANKTOTROPHIC
http//www.pbs.org/wgbh/nova/sharks/island/images/
veliger.jpeg
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Vertical Distribution

• Epipelagic upper 200-300 m water column high
  diversity, mostly small and transparent
  organisms many herbivores
• Mesopelagic 300 1000 m larger than
  epipelagic relatives large forms of gelatinous
  zooplankton (jellyfish, appendicularians) due to
  lack of wave action some larger species (krill)
  partly herbivorous with nightly migration into
  epipelagic regimes 
• Oxygen Minimum Zone 400 800 m depth,
  accumulation of fecal material due to density
  gradient, attract high bacterial growth, which in
  turn attracts many bacterial and larger grazers
  strong respiration reduces O2 content from 4-6 mg
  l-1 to lt 2 mg l-1
• Bathypelagic 1000 3000 m depth, many dark red
  colored, smaller eyes
• Abyssopelagic gt 3000 m depth, low diversity and
  low abundance
• Demersal or epibenthic live near or temporarily
  on the seafloor mostly crustaceans (shrimp and
  mysids) and fish

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Diel Vertical Migration

• DAILY (diel) vertical migrations over distances
  of lt100 to gt800 m
• Nocturnal single daily ascent beginning at
  sunset, and single daily descent beginning at
  sunrise
• Twilight two ascents and descents per day (one
  each assoc. with each twilight period)
• Reversed single ascent to surface during day,
  and descent to max. depth during night

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Scattering Layer
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Horizontal distribution patchiness
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Exotic Planktonic species
New England Ctenophore ? Black Sea
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• Water Tank Ballast
• Holoplankton
• Meroplankton

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Black Sea Ballast Invasions
Mnemiopsis
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Black Sea Ballast Invasions
Mnemiopsis
Beroe ovata
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European Green Crab Carcinus maenas