Transcript Document

Zooplankton
http://www.microscopy-uk.org.uk
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)
Herbivorous zooplankton: Grazers
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
Feeding modes in Zooplankton
• Filter feeders
• Predators – catch individual particles
Filter Feeder
Copepod
Ctenophore
Filter Feeder
Chaetognath
Arrow Worm
Predator
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
Holoplankton
Copepods
Planktonic crustaceans
Barnacles: benthic sessile crustacean
http://science.whoi.edu/labs/pinedalab/
Meroplankton
Nauplius larva
http://www.microscopy-uk.org.uk
Meroplankton
Cypris larva
http://www.microscopy-uk.org.uk
http://science.whoi.edu/labs/pinedalab/
Cypris larva and metamorphosed juveniles
http://science.whoi.edu/labs/pinedalab/
Barnacle population regulation
http://science.whoi.edu/labs/pinedalab/
Ichthyoplankton
Gadidae
Gadus morhua
Gadidae
Gadus morhua
Ichthyoplankton
Gadidae
Gadus morhua
Ichthyoplankton
Gadidae
Atlantic cod
Gadus morhua
Demersal Adult
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 40°N – 40°S
Dinoflagellates
Noctiluca miliaris
Colonial choanoflagellates
Bacteriofages (Ross Sea)
http://www.nsf.gov/pubs/1999/nsf98106/98106htm/ht-015.gif
Foraminifera (calcareous – all latitudes)
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
Figure 3.21b
Radiolarians (siliceous – low latitudes)
http://www.jochemnet.de/fiu/
Live Radiolarian
http://www-odp.tamu.edu/public/life/199/radiolaria.jpg
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)
Cnidaria (medusae)
Cnidaria (medusae)
Cnidaria (siphonophora)
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, <4 cm
Polychaets: Tomopteris spp. only important
planktonic genus
Ctenophora (comb jellies)
Ctenophora (comb jellies)
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
Heteropod (Predates on Ctenophores)
Pteropod
•http://www.mbari.org/expeditions/
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
Appendicularia
Pelagic Salps
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)
Amphipoda
Amphipoda (parasites of gelatinous plankton)
•http://www.imagequest3d.com/catalogue/deepsea/images/l038_jpg.jpg
Euphasids (krill)
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)
Copepods
http://www.jochemnet.de/fiu/
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
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
Meroplankton
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
Molluscs:
Meroplankonic Veliger larvae
PLANKTOTROPHIC
http://www.pbs.org/wgbh/nova/sharks/island/images/veliger.jpeg
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
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
Scattering Layer
Horizontal distribution: patchiness
Exotic Planktonic species
New England Ctenophore  Black Sea
Water Tank Ballast
•Holoplankton
•Meroplankton
Black Sea Ballast Invasions
Mnemiopsis
Black Sea Ballast Invasions
Mnemiopsis
Beroe ovata
European Green Crab – Carcinus maenas