ENVI 21 Life in the Ocean

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• Phytoplankton
• Over 4000 described species
• Bacillariophyceae (Diatoms)
• Dominant in temperate and high-latitude waters
• Prefer well-mixed, nutrient-rich conditions
• Pelagic and benthic forms
• Pelagic forms generally non-motile
• Unicellular, though some may form chains, which
  then may form mats
• Test composed of two silica valves
• Tests are important components of marine
  sediments in some areas - diatomaceous oozes
• An ooze is any sediment that contains more than
  30 tests, the rest typically terrigenous

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Fig. 2.1
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• Phytoplankton
• Bacillariophyceae (Diatoms)
• Two basic body shapes
• Pennate Elongate, typically motile, mostly
  benthic (Exception Nitzschia)
• Centric Mostly planktonic (Ex Coscinodiscus,
  Chaetoceros)

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• Phytoplankton
• Bacillariophyceae (Diatoms)
• Planktonic forms typically non-motile with
  anti-sinking mechanisms
• Reduced body size
• Structural elaborations increase drag
• Formation of chains
• Reduction of internal ion concentration
• Sequestration of low-density ions, e.g. NH4
• Production and storage of oils
• Many of these mechanisms are generally applicable
  to planktonic organisms
• Living cells typically sink 0-30 m d-1, while
  dead cells may sink twice as rapidly
• Senescent or near-senescent cells may
• Lose ability to regulate ion content or sequester
  low-density ions
• Lose ability to produce and store oils
• Release a chemical (e.g. a polysaccharide) that
  lowers viscosity of water immediately surrounding
  cell

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• Phytoplankton
• Dinophyceae (Dinoflagellates)
• Motile forms possess two flagella
• Not all dinoflagellates are motile and not all
  are autotrophic
• Some lack flagella
• Some heterotrophic (50)
• Some mixotrophic (auto- and heterotrophic)
• Some symbiotic (e.g. zooxanthellae)
• Two basic forms
• Thecate Covered with theca made of cellulose
  plates
• Theca may have spines
• Athecate Less common

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Fig. 2.3
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• Phytoplankton
• Dinophyceae (Dinoflagellates)
• Important open-water primary producers,
  especially in tropical regions
• More tolerant of low nutrients and low light than
  diatoms
• Advantage for thriving under post-diatom-bloom
  conditions
• Often abundant in summer/autumn following spring
  and summer blooms of diatoms
• Motility allows individuals to maintain position
  in water column under low-turbulence conditions
• Motility also allows individuals to spend
  daylight hours in surface waters (light for
  photosynthesis) and night hours in deeper waters
  (nutrients more plentiful)
• Most abundant phytoplankton in stratified,
  nutrient-poor tropical and subtropical waters

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Thecate species of heterotrophic dinoflagellates
use pallium feeding
Feed on other plankton with a pallium (sac)
extruded from a microtubular basket. Siana and
Montrasor (Eur. J. Phycol. 2005) reported
ingestion rates up to 36 diatoms/ Protoperidinium
vorax /hr Other reports are lower
http//chbr.noaa.gov/pmn/images/PhytoplanktonPics/
Protoperidinium/ProtoperidiniumSEM02.jpg
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• Protoperidinum feeding on Ceratium furca
• Arrow shows pallium
• Arrowheads show multiple Protoperidinium feeding
  on the same prey
• Olseng, et al. 2002 Mar Ecol Prog Series
• Other species of dinoflagellates use a tube
  inserted into prey to consume the cytoplasm
• Only naked dinoflagellate species engulf prey

Olseng, et al. (2002) Mar Ecol Prog Series
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Swimming with bioluminescent dinoflagellates
Campbell and Reece Figure 28.12x2
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Dinoflagellates often cause Harmful Algal Blooms
http//www.whoi.edu/redtide/
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• Phytoplankton
• Haptophyceae (Coccolithophorids)
• Very small (typically less than 20 µm)
• Covered by calcium carbonate coccoliths
• Coccoliths may be important components of
  sediments
• Typically motile at some life stage (have
  flagella)
• Most species occur in warm water at relatively
  low light intensities
• Most abundant at depths of ca. 100 m in clear,
  tropical, oceanic water
• Blooms may cover extensive areas
• Ex Bloom covering 1000 x 500 km of sea surface
  in North Atlantic (area roughly equivalent in
  size to Great Britain)

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• Phytoplankton
• Chrysophyceae (Silicoflagellates)
• Silica test, usually with spines
• Single flagellum
• Relatively rare but more common in colder water
  than tropics
• Cyanobacteria (Blue-Green Bacteria)
• Most relatively minor primary producers
• Certain species may be important in particular
  areas for limited periods of time
• Some can fix nitrogen (e.g. mats of Oscillatoria)
• Attribute may explain relatively high abundances
  of Oscillatoria in tropical waters which often
  have low concentrations of nitrogen sources
  generally used by algae (e.g. ammonia, nitrite,
  nitrate)

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Cyanophyceae (Cyanobacteria)

• Phycoerythrin and phycobilin
• accesory pigments.
• Nitrogen Fixation
• Some symbiotic
• Some filamentous or colonial

• Katagnymene spiralis
• Two colonies of Trichodesmium
• Aphanizomenon sp. colony note heterocyst (H)
• Benthic Rivularia atra
• Lichen Lichina confinis
• Diatom with cyanobacterial symbiont Richelia
  intracellularis (R)
• Dinoflagellate with a "collar" specialised for
  Synechococcus (S) cyanobionts.

http//www.bom.hik.se/njasv/mcb.htmlpics20cyano
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• Phytoplankton
• Prochlorophytes
• Very small (0.6-0.8 µm diameter)
• Components of nanoplankton and picoplankton
• Resemble bacteria in some respects and algae in
  others
• Structurally, resemble large chloroplasts with
  internal membranes that facilitate photosynthesis
• Appear to be closely related to cyanobacteria and
  may be ancestors of modern algae
• In some areas, e.g. oceanic equatorial Pacific,
  production by prochlorophytes may constitute a
  substantial fraction of total phytoplankton
  chlorophyll (up to 60) and primary production
• Cell densities may be comparable to those for
  bacteria (ca. 106 ml-1)
• Phytoplankton community in some areas may change
  from diatom- or dinoflagellate-dominated
  assemblages to prochlorophyte-dominated
  assemblages
• Shift has profound consequences for entire food
  web

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• Phytoplankton
• Prochlorophytes
• Very small (0.6-0.8 µm diameter)
• Components of nanoplankton and picoplankton
• Resemble bacteria in some respects and algae in
  others
• Structurally, resemble large chloroplasts with
  internal membranes that facilitate photosynthesis
• Appear to be closely related to cyanobacteria and
  may be ancestors of modern algae
• In some areas, e.g. oceanic equatorial Pacific,
  production by prochlorophytes may constitute a
  substantial fraction of total phytoplankton
  chlorophyll (up to 60) and primary production
• Cell densities may be comparable to those for
  bacteria (ca. 106 ml-1)
• Phytoplankton community in some areas may change
  from diatom- or dinoflagellate-dominated
  assemblages to prochlorophyte-dominated
  assemblages
• Shift has profound consequences for entire food
  web

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• Phytoplankton
• Blooms
• Occur when conditions become favorable for one
  species or group of phytoplankton
• Population of that species or group increases
  rapidly and suddenly
• If bloom species is a dinoflagellate, densities
  sometimes increase so rapidly and reach such high
  levels that reddish-brown pigment they produce
  may color the water and cause a red tide

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http//www.whoi.edu/redtide/
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• Phytoplankton
• Blooms
• Red tides typically become visibly apparent when
  cell concentrations reach 2-8 x 106 cells l-1
• Cell concentrations may exceed 108 cells l-1
• As nutrients are depleted and bloom begins to
  break down, bacteria begin to decompose the
  remaining organic material
• If material is sufficiently abundant, bacterial
  decomposition may deplete oxygen in surface
  waters, negatively impacting local fauna
• Phenomenon applies to any large phytoplankton
  bloom, not just red tides
• Red tides may involve species that produce
  pigments but are not toxic or may involve species
  that produce compounds that are toxic to marine
  life

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• Phytoplankton
• Blooms
• Toxin (Saxitoxin) may be
• Released into water, where it may be consumed
  directly by organisms that graze on phytoplankton
  (e.g. zooplankton) and indirectly at higher
  trophic levels
• Transmitted from dinoflagellates directly to
  higher organisms, e.g. clams, mussels, scallops,
  oysters, which then may be food for larger
  animals
• Result of consuming tainted fish or bivalves is
  Paralytic Shellfish Poisoning (PSP) - may be
  fatal
• Some forms can be extremely toxic
• Ex Pfiesteria
• Blooms triggered by coastal pollution
• Causes extensive fish kills
• Toxin can cause memory loss in humans

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