Understanding Zooplankton and Their Distribution

Understanding Zooplankton and Their Distribution

Zooplankton are a diverse group of heterotrophic plankton that play a critical role in marine food webs. This article discusses their distribution, behavior, and classification, with a focus on herbivorous zooplankton grazers.

About Understanding Zooplankton and Their Distribution

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1. Zooplankton http://www.microscopy-uk.org.uk

2. 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 m (heterotrophic flagellates, protists) up to several meters (jellyfish)

3. Herbivorous zooplankton: Grazers

4. 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

5. Feeding modes in Zooplankton Filter feeders Predators catch individual particles

6. Filter Feeder Copepod

8. Filter Feeder Ctenophore

9. Predator Chaetognath Arrow Worm

10. 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

11. Holoplankton Copepods Planktonic crustaceans

13. Barnacles: benthic sessile crustacean http://science.whoi.edu/labs/pinedalab/

14. Meroplankton Nauplius larva http://www.microscopy-uk.org.uk

15. Meroplankton http://www.microscopy-uk.org.uk Cypris larva

16. http://science.whoi.edu/labs/p inedalab/

17. Cypris larva and metamorphosed juveniles http://science.whoi.edu/labs/pinedalab/

18. Barnacle population regulation http://science.whoi.edu/labs/pinedalab/

19. Gadidae Gadus morhua Ichthyoplankton

20. Gadidae Gadus morhua Ichthyoplankton

21. Gadidae Gadus morhua Ichthyoplankton

22. Gadidae Atlantic cod Gadus morhua Demersal Adult

23. 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 m to 1-2 mm, bacteriovores; most abundant 40N 40S

24. Dinoflagellates Noctiluca miliaris

25. http://www.nsf.gov/pubs/1999/n sf98106/98106htm/ht-015.gif Colonial choanoflagellates Bacteriofages (Ross Sea)

26. Foraminifera (calcareous all latitudes)

27. Radiolaria: spherical, amoeboid cells with silica capsule; 50 m 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 Protists: Protozooplankton

28. Figure 3.21b Radiolarians (siliceous low latitudes)

29. http://www.jochemnet.de/fiu/

30. http://www-odp.tamu.edu/public /life/199/radiolaria.jpg Live Radiolarian

31. 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) Invertebrate Holoplankton

32. Cnidaria (medusae)

33. Cnidaria (medusae)

34. Cnidaria (siphonophora)

35. 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, <4 cm Polychaets: Tomopteris spp. only important planktonic genus Invertebrate Holoplankton

36. Ctenophora (comb jellies)

37. Ctenophora (comb jellies)

38. 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

39. Heteropod (Predates on Ctenophores)

40. Pteropod http://www.mbari.org/expeditions/

41. 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

42. Appendicularia

43. Pelagic Salps

44. 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)

45. Amphipoda

46. Amphipoda (parasites of gelatinous plankton)

47. http://www.imagequest3d.com/c atalogue/deepsea/images/l038_jpg.jpg

48. Euphasids (krill)

49. 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)

50. Copepods

51. http://www.jochemnet.de/fiu/

52. 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 Common Meroplankton

53. Decapoda: shrimps and crabs produce zoa 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 Common Meroplankton

54. Meroplankton

55. 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

56. http://www.pbs.org/wgbh/nova/s harks/island/images/veliger.jpeg Molluscs: Meroplankonic Veliger larvae PLANKTOTROPHIC

57. 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 < 2 mg l-1 Bathypelagic: 1000 3000 m depth, many dark red colored, smaller eyes Abyssopelagic: > 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

58. Diel Vertical Migration DAILY (diel) vertical migrations over distances of <100 to >800 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

63. Scattering Layer

64. Horizontal distribution: patchiness

65. Exotic Planktonic species New England Ctenophore Black Sea

66. Water Tank Ballast Holoplankton Meroplankton

68. Black Sea Ballast Invasions Mnemiopsis

69. Black Sea Ballast Invasions Mnemiopsis Beroe ovata

70. European Green Crab Carcinus maenas