Transcript Marine Ecology 2011, final lecture 8 Zooplankton

Plankton Summary
• Plankton can’t control their location and are moved about by
wind, waves, currents and tides. Plankton are usually grouped by
size, ranging from femtoplankton to megaplankton
• Diatoms are dominant phytoplankton in estuaries while
dinoflagellates (some of which are harmful) and coccolithophores
dominate surface waters offshore (i.e., nanoplankton are most
abundant inshore and picoplankton most abundant offshore)
• Prochlorophytes are tiny, extremely abundant picoplankters that
occur near the base of the sunlit layer in offshore waters
• Cyanobacteria (e.g., Trichodesmium) are nitrogen fixers and can
be limited by iron
Plankton Summary
• Half of all primary production occurs in shallow waters of the
continental shelf, while the other half is distributed over the rest of
the entire ocean.
• Net primary production equals gross primary production (total
production) minus respiration, which is the amount available for
consumption by herbivores
• The euphotic zone is the depth to which light penetrates and
photosynthesis can occur
• Four methods of measuring primary production are: oxygen
evolution, 14C uptake, satellite sensing, and fluorometry
Plankton Summary
• Light and nutrients are major factors controlling primary
production (p.p.). Photoinhibition occurs when there is too much
light, and for this reason the max p.p. occurs below the surface
• Compensation depth is the depth where for a given algal cell,
photosynthesis = respiration
• Ocean water has much less nitrogen than soil, which is why N is
often limiting in the ocean
• Thermoclines prevent mixing of surface and bottom waters and
prevents nutrients from re-entering surface waters
• High nutrient low chlorophyll (HNLC) zones are limited by iron
Plankton Summary
• Critical Depth is the point at which Gross Photosynthesis = Total
Plant Respiration, and is a characteristic of the population
• Zooplankton regenerate nutrients by sloppy feeding and excretion,
and can control phytoplankton abundance. The polar, temperate
and tropical regions have characteristic seasonal patterns of
phytoplankton and zooplankton abundance
• Bacterial cells are 5 orders of magnitude more abundant than algal
cells and have been high growth rates. They use DOC as an
energy source and can outcompete phytoplankton for nutrients.
• Original microbial loop concerned DOC, bacteria, flagellates and
ciliates. The microbial web also includes the small phytoplankton
that cannot be consumed by large zooplankton
Plankton Summary
• Viruses are an order of magnitude more abundant than bacteria,
and cause them significant mortality. Virus also transmit genetic
material to their hosts and can be imporant agents of
evolutionary change for them.
• When bacterial consumption of DOC exceeds primary
production this is NET HETEROTRPHY. When production
exceeds bacterial consumption this is NET AUTOTROPHY
•
Zooplankton
http://www.microscopy-uk.org.uk
Planktos: “drifts” in greek
• Their distribution depends on currents and gyres
• Certain zooplankton can swim well, but their
distribution is controlled by current patterns
• Zooplankton: all heterotrophic 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
Filter Feeder
Ctenophore
Predator
Chaetognath
Arrow Worm
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
Holoplankton
Copepods
Planktonic crustaceans
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/
Ichthyoplankton
Cod, Gadus morhua
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 metazoans; some holoplanktonic,
others have benthic stages; carnivorous (crustaceans, fish);
long tentacles carry nematocysts used to inject venoms into
prey
– Medusae: single organisms, few mm to several meters
– Siphonophores: colonies of animals with specialized
polyps for feeding, reproduction and swimming;
Physalia physalis (Portuguese man-of-war), common in
tropical waters, GoM, drift with the wind and belong to
the pleuston (live on top of water surface)
Cnidarian (medusa)
Cnidarian (medusa)
Cnidarian (siphonophore)
Invertebrate Holoplankton
• Ctenophores: separate phylum (not Cnidarians;
transparent organisms, swim 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 with foot developed into paired
“wings”; suspension feeders – produce large mucous
nets to capture prey; carbonate shells produce pteropod
ooze on sea floor
Heteropod (Preys 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
Appendicularian
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
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
Three explanations for the
existence of vertical migrations
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
• http://web.me.com/russellkelley/rk/The_pla
nkton.html
• http://www.youtube.com/watch?v=HSPxX
Cq9krU&feature=list_related&playnext=1
&list=SP3A32768200CED51C
Marine Snow
Composition of Marine Snow
Once living material (detrital) that is large enough to
be seen by the unaided eye.
Described first by Suzuki and Kato (1955)
High C:N makes for poor food quality.
• Senescent phytoplankton
• Feeding webs (e.g., pteropods,
larvaceans)
• Fecal pellets
• Zooplankton molts
Formation of Marine Snow
Type A: Mucous feeding webs are discarded
individually.
Type B: Smaller particles aggregate into larger,
faster sinking particles.
Aggregates
Marine Snow Particles
Marine Snow Particles
Discarded feeding houses
Marine Snow Particles
‘Comets’
Aggregates
Contribution of Marine Snow to Vertical Flux
Narrow window of particle sizes which are large
enough to sink but numerous enough to be widely
distributed.
Cells
Snow
Bodies
2
200
20,000 (um)
cell
chain
plankton
feces
aggregates
Willie
X
1-10 m
50 m
Available to
water column
processes
100 m
2000 m
Reduction in Vertical Flux over Depth
1
The Martin Curve
50% losses by 300 m
75% losses by 500 m
90% losses by 1500 m
Martin and Knauer 1981
2
3
Extreme Deposition: Food Falls
• Rare events (not recorded in traps)
• Deposit large amounts of high quality organic
materials to sea floor (low C:N)
• Rapid sinking, reach 1000s of meters in few days
• Large bodies that remain intact (whales, fish,
macroalgae, etc)
Amount of nutrients at
different depths is
controlled by
photosynthesis,
respiration, and
the sinking of
organic particles.
Nutrients are
recycled but sink!