ENVI 21 Life in the Ocean

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Fig. 2.46
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• Zooplankton
• Holoplankton
• Spend entire lives as plankton
• Historically, epipelagic plankton moderately well
  sampled, especially within areas covered by
  commercial shipping lanes (CPR, LHPR)
• Heterotrophic Protista
• Among most important holoplanktonic grazers in
  terms of numbers and influence
• Dinoflagellates
• Heterotrophic or mixotrophic
• May reach 1 mm or more in size
• Feed on bacteria, diatoms, ciliates and other
  flagellates, either by using flagella to generate
  feeding currents or producing sticky cytoplasmic
  extensions that trap prey
• Ex - Noctiluca

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• Zooplankton
• Holoplankton
• Heterotrophic Protista
• Zooflagellates
• Lack chloroplasts strictly heterotrophic
• Feed primarily on bacteria and detritus
• Small (typically 2-5 µm in diameter) but may have
  high reproductive rates
• Can become extremely abundant under favorable
  circumstances (20-80 of nanoplankton abundance
  by count)
• May be important food source for larger secondary
  consumers

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• Zooplankton
• Holoplankton
• Heterotrophic Protista
• Foraminifera
• Unicellular, amoeboid
• Produce perforated calcareous tests typically
  composed of a series of chambers
• Planktonic species range from ca. 30 µm to a few
  mm, smaller than benthic species
• Capture food using slender pseudopodia
  (rhizopodia) that project through pores in test
  and trap small particles and organisms (bacteria,
  phytoplankton, small zooplankton)
• Especially abundant in surface waters between
  40oN and 40oS, and tests may form important
  components of calcareous sediments (foraminiferan
  oozes)
• Ex - Globigerina

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Globigerinoides ruber
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• Zooplankton
• Holoplankton
• Heterotrophic Protista
• Radiolaria
• Unicellular, ameboid
• Similar to forams but tests composed of silica
  (SiO2) instead of CaCO3
• Range from ca. 50 µm to a few mm
• Some species form gelatinous colonies up to 1 m
  across
• Produce porous mineral tests through which
  branched pseudopodia (axopodia) are extended to
  feed on bacteria, other protists, phytoplankton
  (esp diatoms - why??) and even small crustaceans
• Common in all oceanic regions but especially
  abundant in cold waters, including deep sea
• Sediments may consist of radiolarian oozes

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• Zooplankton
• Holoplankton
• Heterotrophic Protista
• Ciliophora
• Present in all parts of ocean
• May be extremely abundant in some areas
• Cilia may be used for both locomotion and feeding
  
• Typically prey on small phytoplankton,
  zooflagellates, small diatoms, bacteria
• Tintinnids ciliates with vase-shaped,
  proteinaceous external shells that arent found
  in sediments because of degradable nature
• Relatively small (20-640 µm) but may be important
  because of wide distribution
• Tintinnids feed primarily on nanoplanktonic
  diatoms and photosynthetic flagellates
• May consume up to 60 of primary production in
  some coastal waters

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• Zooplankton
• Holoplankton
• Cnidaria
• Includes medusae and siphonophores
• Medusae range from a few mm to 2 m across
  (Tentacles of Cyanea capillata may be 30-60 m
  long) and feed using tentacles with
  cnidocytes/nematocysts
• Siphonophores are colonial cnidarians
  individuals perform specialized functions (e.g.
  swimming, feeding, reproduction) that benefit
  colony
• Ex - Portugese man-of-war (Physalia) portion
  floats on sea surface and tentacles may extend 10
  m into water
• Siphonophores may reach 50-70 m in length
• Feed primarily on zooplankton and
  appropriately-sized nekton

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Cyanea capillata
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• Zooplankton
• Holoplankton
• Ctenophora
• Carnivorous eat fish eggs and larvae as well as
  smaller zooplankton
• Feed using paired, sticky tentacles (tentaculate)
  or large, ciliated oral lobes (lobate)
• May be ecologically significant as competitors
  for food resources
• Populations may increase explosively at certain
  times of year in certain areas

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Pleurobrachia
Tentaculate
Beroe
Lobate
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• Zooplankton
• Holoplankton
• Chaetognatha
• Among the most abundant carnivorous plankton,
  worldwide
• Exclusively marine and found over a wide depth
  range
• Relatively small (max. length ca. 4 cm) but
  voracious predators
• Sit-and-wait predators
• Primary food item small zooplankton

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• Zooplankton
• Holoplankton
• Annelida
• Relatively few known holoplanktonic annelids, all
  in class Polychaeta
• Planktonic polychaetes present throughout ocean
• Prey most frequently on small zooplankton
• Typically small (up to 20 cm) some may be bigger

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• Zooplankton
• Holoplankton
• Mollusca
• Relatively few holoplanktonic mollusks
• Ex - Janthina
• Heteropoda
• Small group closely related to snails
• Swim by undulating fin (modified gastropod foot)
• Some species have a small calcium carbonate shell
  into which a portion of body can withdraw
  defensively lost in many species
• Visual predators on planktonic molluscs,
  copepods, chaetognaths, salps and siphonophores
• Well-developed eyes
• Most common in tropical waters

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• Zooplankton
• Holoplankton
• Mollusca
• Pteropoda
• Two forms thecate (thecosome shelled) and
  athecate (gymnosome - no shell)
• Thecate forms have calcareous shells that may be
  coiled or cup-shaped.
• Thecosomes swim using paired wings (modified
  gastropod foot)
• Thecosomes suspension feeders, trapping particles
  using large mucus webs
• Typical diet includes phytoplankton, small
  zooplankton and detrital material
• Some thecosomes may be important food items for
  pelagic fishes, including some commercially
  important species (e.g. herring, etc.).
• Shells of thecate pteropods may accumulate in
  sediments (pteropod oozes)
• Gymnosomes typically predatory, often feeding on
  other pteropods
• May get quite large (to 8.5 cm) and are common
  throughout the oceans

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• Zooplankton
• Holoplankton
• Arthropoda
• Major group subphylum Crustacea
• Copepoda
• Predominant class of holoplanktonic crustaceans
  is the Copepoda
• Calanoida
• Most common group of copepods with nearly 2000
  described species
• Present throughout ocean and comprise a major
  proportion of planktonic biomass in many areas
• Typically small (lt 6 mm) though some large
  species may exceed 1 cm
• Most are primary consumers, feeding on
  phytoplankton
• Some may be carnivorous on small zooplankton
• Development involves 12 different stages, 6
  naupliar stages (NI - NVI) and 6 copepodite (CI -
  CVI) stages, last of which is mature adult

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Herbivorous vs. Predatory Copepod
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Copepod Suspension Feeding Mechanism
Selective Particle Sorting
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Calanoid
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• Zooplankton
• Holoplankton
• Arthropoda
• Major group subphylum Crustacea
• Copepoda
• Predominant class of holoplanktonic crustaceans
  is the Copepoda
• Calanoida
• Most common group of copepods with nearly 2000
  described species
• Present throughout ocean and comprise a major
  proportion of planktonic biomass in many areas
• Typically small (lt 6 mm) though some large
  species may exceed 1 cm
• Most are primary consumers, feeding on
  phytoplankton
• Some may be carnivorous on small zooplankton
• Development involves 12 different stages, 6
  naupliar stages (NI - NVI) and 6 copepodite (CI -
  CVI) stages, last of which is mature adult

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Fig. 2.7
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• Zooplankton
• Holoplankton
• Arthropoda
• Copepoda
• Cyclopoida
• Differ from calanoids shorter antennae (used by
  some species to capture prey), more segments in
  abdomen
• Over 1000 species but most are benthic
• About 250 planktonic species and some (e.g.
  Oithona) may be abundant locally

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Calanoid
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• Zooplankton
• Holoplankton
• Arthropoda
• Copepoda
• Harpacticoida
• Predominantly benthic
• Typically small
• Seldom important elements of zooplankton

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• Zooplankton
• Holoplankton
• Arthropoda
• Euphausiacea (Krill)
• Shrimp-like organisms typically 15-20 mm long but
  exceeding 10 cm in some species
• Generally omnivorous may consume both plant and
  animal material but prefer phytoplankton and
  phytoplankton detritus when available
• May be extremely important ecologically Keystone
  species in Southern Ocean E. superba
• May be very abundant, e.g. Euphausia superba
  super-swarms in the Southern Ocean have been
  estimated at 450 sq km x 200 m _at_ gt1000 m-3
• Typically very mobile, and most net-based surveys
  may underestimate abundance ? recent switch to
  use of acoustic techniques for surveys

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• Zooplankton
• Holoplankton
• Arthropoda
• Amphipoda
• Typically small animals, though some species may
  exceed 10 cm
• Planktonic forms typically free-living
  carnivores, but some species live in close
  association with salps, medusae and other
  gelatinous zooplankton
• Typically constitute a minor component of
  zooplankton, gravimetrically
• Unlike most planktonic crustaceans, amphipods
  brood their young

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• Zooplankton
• Holoplankton
• Arthropoda
• Ostracoda
• Typically minor components of zooplankton
  community
• Most species quite small (few mm), though
  Gigantocypris can exceed 2 cm in diameter
• Some important as food sources for other species,
  notably small fishes

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• Zooplankton
• Holoplankton
• Arthropoda
• Mysidacea
• Closely related to amphipods
• Seldom important components of planktonic
  communities
• Some species are diel vertical migrators and
  important food items for certain species (e.g.
  fishes living on shallow banks)

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• Zooplankton
• Holoplankton
• Arthropoda
• Decapoda
• Among largest zooplankton May reach 10 cm
• Many species are diel vertical migrators and
  often exhibit net avoidance
• Often omnivores or predators, feeding primarily
  on smaller planktonic crustaceans (e.g. copepods,
  euphausiids)

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• Zooplankton
• Holoplankton
• Chordata
• Appendicularians/Larvaceans
• Closely related to sea squirts
• Referred to as Larvaceans because of resemblance
  to tadpole larvae of sea squirts
• Most species produce spherical mucus houses
• Typical larvacean bodies are a few mm long
  houses may reach a meter in diameter
• Movements of animals tail pump water through
  house across a series of mucus mesh filters that
  strain particles from water
• Link
• Periodically, filters become clogged and
  larvacean abandons house and builds a new one
  takes a few minutes and may be repeated more than
  10 times a day
• Larvaceans grow rapidly, may have generation
  times of only a few weeks and are among the most
  abundant zooplankton in some coastal regions
  (e.g. up to 5000 m-3 in Monterey Bay)
• Abandoned larvacean houses may be important
  components of marine snow in some areas

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• Zooplankton
• Holoplankton
• Chordata
• Thaliacea (Salps)
• Common in near-surface waters, though some
  deep-living forms
• Swim using radial bands of muscle to pump water
  through central body cavity
• Same stream of water passed through mucus net
  that filters out food particles
• Food particles consist primarily of bacteria and
  phytoplankton, ranging from 1 µm to 1 mm
• May bloom to form dense aggregations
• High abundance and high feeding rates may reduce
  abundance of small particles/organisms in water
  column and effectively outcompete other consumers
  for food resources (e.g. krill in Southern Ocean)

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• Zooplankton
• Meroplankton
• Meroplankton spend portion of life in plankton
  adult stage typically non-planktonic
• About 70 of benthic marine species have a
  planktonic stage in their life cycle
• Planktonic stage of a benthic organisms life may
  last minutes to months
• Presence of particular species in meroplankton
  typically related to spawning events, often in
  response to environmental cues (e.g. warmer
  temperatures in temperate latitudes, rainfall or
  lunar cycles in tropical waters)
• Important component of meroplankton is
  ichthyoplankton, fish eggs and larvae
• Some fish eggs may be extremely abundant (e.g. 4
  x 1014 pilchard eggs in English Channel) and
  energetically important as food sources for other
  pelagic organisms
• Marine organisms with pelagic larvae exhibit two
  basic strategies for nourishing larval stages

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Fig. 2.25
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• Zooplankton
• Meroplankton
• Meroplankton spend portion of life in plankton
  adult stage typically non-planktonic
• About 70 of benthic marine species have a
  planktonic stage in their life cycle
• Planktonic stage of a benthic organisms life may
  last minutes to months
• Presence of particular species in meroplankton
  typically related to spawning events, often in
  response to environmental cues (e.g. warmer
  temperatures in temperate latitudes, rainfall or
  lunar cycles in tropical waters)
• Important component of meroplankton is
  ichthyoplankton, fish eggs and larvae
• Some fish eggs may be extremely abundant (e.g. 4
  x 1014 pilchard eggs in English Channel) and
  energetically important as food sources for other
  pelagic organisms
• Marine organisms with pelagic larvae exhibit two
  basic strategies for nourishing larval stages

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• Zooplankton
• Meroplankton
• Planktotrophic
• Eggs relatively small and contain little stored
  energy
• Species with planktotrophic development have
  higher fecundities than species with
  lecithotrophic development (e.g. plaice - 250,000
  eggs, haddock - 500,000 eggs, cod - gt1,000,000
  eggs)
• Low per-egg energy investment ? lower per-egg
  survivorship but vastly greater numbers of
  propagules for a given reproductive energy
  investment
• Survivorship typically very low (e.g. early life
  mortality in cod estimated at around 99.999).
• Planktotrophic larvae feed in plankton, typically
  have long larval life spans, and may travel very
  long distances (teleplanic larvae - e.g. coral
  planula larvae)

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• Zooplankton
• Meroplankton
• Lecithotrophic
• Eggs relatively large and contain substantial
  stored energy
• Species with lecithotrophic development have
  lower fecundities than species with
  planktotrophic development (typically lt1000)
• High per-egg energy investment ? higher per-egg
  survivorship but fewer propagules for a given
  reproductive energy investment
• Yolk sac typically used to sustain larva while
  mouth and gut finish developing
• Lecithotrophic larvae typically do not feed in
  plankton (though many do), have short larval life
  spans (generally less than a week and sometimes a
  few hours), and generally dont disperse very
  long distances
• Often lecithotrophic eggs are buoyant and species
  exhibit ontogenetic vertical migration within
  water column (e.g. Sebastolobus altivelis)

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• Zooplankton
• Vertical Distribution
• Planktocline
• In stable water columns with very shallow mixed
  layers, e.g. at low latitudes in eastern parts of
  oceans or mid-latitudes toward end of summer,
  zooplankton abundance may be much higher in mixed
  layer than below it, with highest abundances just
  above thermocline
• Abundance typically declines sharply near bottom
  of thermocline planktocline
• Some controversy Does zone of maximum
  zooplankton biomass coincides with region of
  maximum phytoplankton biomass or productivity?
• Recent evidence macrozooplankton feed at or near
  productivity maximum microzooplankton feed at or
  near phytoplankton biomass maximum

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• Zooplankton
• Vertical Distribution
• Diel Vertical Migration (DVM)
• Patterns
• Nocturnal Surface at night, depth during day
• Twilight Sunset ascent, midnight sink, dawn
  descent
• Reverse Surface during day, depth at night
• Nature
• Different species and life stages exhibit
  different vertical migration patterns and depth
  ranges
• Major trigger Light
• Solar eclipse ? Premature migration

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• Zooplankton
• Vertical Distribution
• Diel Vertical Migration (DVM)
• Value
• Access to food in surface waters at night with
  reduced vulnerability to visual predators
• Daytime depths of predators not dark enough to
  prevent predation
• Some zooplankton migrate deeper than necessary to
  avoid high predation
• Many predators also migrate
• Tested experimentally in a limited way by
  studying DVM in response to different predation
  pressures
• Ohman (1990) Pseudocalanus newmani undergoes
  migration, reverse migration or no migration when
  major predators are visually hunting
  planktivorous fishes, nocturnally feeding
  nonvisual zooplankton, or absent

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• Zooplankton
• Vertical Distribution
• Diel Vertical Migration (DVM)
• Value
• Energetic benefits
• Descending into cooler waters during day reduces
  metabolic rates and makes more efficient use of
  food
• Support DVM less common in polar waters
• Question Do energetic benefits exceed costs of
  migration?
• Replenishment of food supply
• No conclusive evidence
• Low food may enhance or suppress DVM
• Consequences
• Mixing of populations enhances gene flow
• Active transport of organic material to sea floor
  through trophic ladder

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• Zooplankton
• Vertical Distribution
• Seasonal Vertical Migration
• Seasonal patterns in vertical distribution
  relatively common among species in temperate and
  polar regions as well as upwelling zones, but
  generally not in tropical species

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Fig. 2.42
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Fig. 2.43
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• Zooplankton
• Horizontal Distribution
• Wide range of spatial scales
• Water Mass Affiliations
• Cosmopolitan species have wide or even global
  distributions
• Other species are local or closely associated
  with a particular set of hydrographic conditions
• Some highly specific species can be indicators
  for a particular water mass
• Concept of indicator species most commonly
  applied to foraminifera, copepods and
  chaetognaths (sufficiently abundant)
• Ex Omori (1965) used distributions of copepod
  species assemblages to identify three major
  oceanic regions in North Pacific
• Cold offshore region characterized by Neocalanus
  plumchrus and Calanus cristatus
• Warm offshore region characterized by Calanus
  pacificus
• Neritic region characterized by Pseudocalanus
  minutus and Acartia longiremis

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• Zooplankton
• Horizontal Distribution
• Latitudinal Patterns
• Strong N-S temperature gradient ? distributional
  affinities related to water temperature
• About 50 of all epipelagic zooplankton spp. have
  distributional centers in tropical and
  subtropical waters with some presence in
  temperate waters
• About one-third of epipelagic holoplankton are
  restricted to tropical and subtropical waters
• Other species restricted to cold waters at high
  latitudes
• Some species endemic to either Arctic or Antarctic

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• Zooplankton
• Horizontal Distribution
• Latitudinal Patterns
• Some species have bipolar distribution
• Ex Pteropods - Limacina helicina and L.
  retroversa, Amphipod - Parathemisto gaudichaudii,
  Siphonophore - Dimophyes arctica
• Arctic-Antarctic species pairs have bipolar
  distributions and occupy similar niches within
  communities at both poles
• Ex Gymnosome pteropods, Clione limacina
  (Northern Hemisphere) and C. antarctica (Southern
  Hemisphere), are morphologically similar and both
  feed on two Limacina species
• Bipolarity may have arisen through
• Polar emergence
• Relict distributions
• General trend toward decreasing species diversity
  with latitude
• Groups that occur at low and high latitudes
  typically have fewer high-latitude species, while
  some groups (e.g. heteropod mollusks) have no
  high-latitude representatives
• Many circumglobal tropical-subtropical species
  occur in warm waters of Atlantic, Pacific and
  Indian oceans (e.g. Janthina, Glaucus, some
  euphausiids, chaetognaths and amphipods)
• Tethyan Distribution