Plankton

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Plankton

• drifting organisms
• Ch. 15 Marine Biology
• 5th ed. pp.310-318
• 6th ed. pp.324-332

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Size classification

• ultraplankton - bacteria and other very small
  plankton, lt5 µm (0.005 mm)
• nannoplankton - mostly phytoplankton, 5 - 70 µm
  (0.005-0.07 mm)
• microplankton - mostly zooplankton, 70 - 100 µm
  (0.07 - 0.1mm). Also called "net plankton"
• macroplankton - not microscopic, for example
• jellyfish
• Sargassum (a type of seaweed that floats at the
  sea surface)
• gtSizegt
• ultragtnannogtmicrogtmacro

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Another classification of marine organisms is

• (4) Nekton - Not plankton. Swimming organisms,
  mostly high trophic level carnivores, but a few
  are herbivores (e.g.,anchovy). All are
  heterotrophs.
• Examples fish, squid, marine mammals

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Another classification of marine organisms is

• (5) Benthos - Not plankton. Bottom-dwelling
  plants and animals. These can be any size and
  have any degree of mobility.

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Another classification of marine organisms is

• (6) Intertidal and coastal organisms - Not
  plankton. These plants and animals are often
  closely related to benthos living in deeper
  water some are land organisms adapted to
  tolerate salt. Primary producers include seaweeds
  of coastal areas, sea grasses, mangroves, and
  other coastal plants

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Another classification of marine organisms is

• (1) Phytoplankton - plants, primary producers or
  autotrophs.
• The most important primary producers of the sea.
• In general, phytoplankton can grow only in the
  photic zone, but living phytoplankton can be
  found in deeper water.
• Most phytoplankton are microscopic algae, and the
  vast majority are single-celled (unicellular) or
  colonial (made up of many, identical cells).

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2. Major Phytoplankton Groups

• 2.1 Diatoms
• 2.2 Dinoflagellates
• 2.3 Coccolithophores

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2.1 Diatoms

• Characteristics
• Golden-brown color due to a pigment fucoxanthin
  in addition to chlorophyll.
• Diatoms have a frustule (shell-like covering)
  made of an organic matrix or framework
  impregnated with silica (SiO2)
• Diatoms have 2 basic shapes centric and pennate
• Habitat
• Ubiquitous, but most abundant in cold,
  nutrient-rich water. Often make up gt45 of
  phytoplankton biomass in such waters. Often
  responsible for spring phytoplankton blooms in
  temperate and polar oceans. Also abundant in
  upwelling regions at low latitudes.
• Siliceous sediments are often found under regions
  of high diatom productivity.

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2.2 Dinoflagellates

• Characteristics
• Usually red or red-brown in color, due to
  carotene and xanthophyll pigments.
• Have flagella, and are motile. (Move vertically
  in response to light).
• Some can absorb organic substances from solution
  (heterotrophy).
• Most have "armor" made of cellulose.
• Many are bioluminescent (glow, especially when
  agitated).
• Habitat
• Ubiquitous, favor warmer and more
  nutrient-depleted water than diatoms.
• In temperate regions, often "bloom" in late
  summer or early fall.

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Dinoflagellates Cont.

• Dinoflagellates and "Red Tides"
• Blooms of certain species of dinoflagellates give
  reddish or brownish color to the water.
• Some of these dinoflagellates produce toxins
  responsible for PSP (paralytic shellfish
  poisoning) or NSP (neurotoxic shellfish
  poisoning).For example Gonyaulax and
  Ptychodiscus are major toxic species in U.S.
  waters.
• Shellfish accumulate the toxin as they
  filter-feed on algae. They are not affected by
  the toxin. Crabs, shrimp, fish, marine mammals,
  and humans are affected.
• The human lethal dose is 1mg.
• Occurrence and Causes of Harmful Algal Blooms
• Worldwide, harmful algal blooms (HABs) appear to
  be increasing in frequency or duration. Many of
  these are due to dinoflagellates, although other
  organisms, including diatoms, are involved.
  Possible causes of increased HABs are
• Excessive nutrient input to coastal due to
  agricultural fertilizers, sewage
• Transport of new species from their habitat to
  new locations, mostly in ships ballast water
• Climatic warming

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2.3 Coccolithophores

• Characteristics
• Occur as single cells.
• Covered by plates made of calcite (calcium
  carbonate) called coccoliths which make up some
  calcareous sediments on the sea floor.
• Have 2 flagella.
• Are smaller in size than most diatoms or
  dinoflagellates.
• Habitat
• Dominate in warm, low nutrient, low productivity
  waters of the oceans.
• However, blooms occur in colder waters as well,
  e.g., Bering Sea since 1997, North Atlantic

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Another classification of marine organisms is

• (2) Bacterioplankton - Bacteria
• Some are primary producers or autotrophs
• Blue-green "algae" or cyanobacteria may be
  responsible for most primary production in some
  areas of the open sea
• Some other bacterioplankton, such as sulfur
  oxidizing bacteria, are important primary
  producers in specific locations
• Some are heterotrophs and decompose the remains
  of dead organisms, excreta, etc.

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3. Bacterioplankton

• The most abundant organisms in the ocean
  (1,000,000 per ml). Have the greatest "standing
  stock" of biomass in low-productivity regions of
  the ocean

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Bacterioplankton Cont.

• Characteristics
• Very small (usually lt1µm in diameter).
  Prokaryotes (lack nuclear membrane). Come in many
  shapes
• May be either free or attached to surfaces,
  including other organisms.
• Habitat
• Everywhere.
• Cyanobacteria are more numerous than other
  primary producers where nutrient concentrations
  are very low, because they have the ability to
  fix nitrogen.
• Heterotrophic bacteria are more numerous where
  there is a lot of organic material, i.e., areas
  of high primary productivity
• Role
• Primary producers or decomposers of organic
  matter and recyclers of nutrients.
• "Blue-green algae" are actually prokaryotic
  organisms that are bacteria, not algae. They are
  photosynthetic (autotrophic) primary producers.
• Heterotrophic bacteria are the main decomposers
  of the sea, and are responsible for most nutrient
  recycling and oxygen consumption in the oceans.

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Another classification of marine organisms is

• (3) Zooplankton - Animals, may be either
  herbivores (eat plants) or carnivores (eat other
  animals) or bacteriovores (eat bacteria) or
  omnivores (eat plants or animals). All are
  heterotrophs.
• Examples copepods, euphausiids, jellyfish

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Zooplankton

• Heterotrophs- consume organic matter
• Zooplankton can be Herbivores, carnivores,
  detritus feeders, omnivores
• Zooplankton includes
• Crustaceans
• Chaetognaths
• Protozoan
• Gelatinous zooplankton
• Pteropods
• Meroplankton

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1. Crustaceans- include shrimp, copepods,
euphausiids ("krill")

• Characteristics Copepods, euphausiids and shrimp
  superficially resemble one another. All have
• exoskeletons of chitin
• jointed appendages
• 2 pair of antennae
• complex body structure, with well developed
  internal organs and sensory organs
• Habitats Ubiquitous.
• Euphausiids predominate in the Antarctic Ocean,
  but are common in most temperate and polar
  oceans.
• Copepods are found everywhere, but are less
  important in low-productivity areas of the ocean
  - the "central ocean gyres". They are found at
  all depths but are more abundant near the
  surface.
• Role in food webs
• Euphausiids and copepods are filter-feeders.
  Copepods are usually herbivores, while the larger
  euphausiids consume both phytoplankton and other
  zooplankton.
• Shrimp are usually carnivores or scavengers.

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2. Chaetognaths - ("Arrow worms")

• Characteristics
• 2-3 cm long
• wormlike, but non-segmented
• no appendages (legs or antennae)
• complex body structure with internal organs
• Habitat Ubiquitous
• Role in food web Carnivore feeding on small
  zooplankton such as copepods.

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3. Protozoan - Include foraminifera,
radiolarians, tintinnids and "microflagellates"
ca. 0.002 mm

• Characteristics
• Single-celled animals.
• Forams have calcareous shell
• Radiolarians have siliceous shell.
• Both Forams and Radiolarians have spines.
• Habitat Ubiquitous
• Radiolarians are especially abundant in the
  Pacific equatorial upwelling region.
• Protozoa are especially important components of
  the food web in low-productivity ocean areas.
• Both are found in sediments as well as in the
  water column.
• Role in food web Feed on small phytoplankton,
  bacterioplankton, and other protozoans. They can
  be bacteriovores, herbivores, or carnivores.

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4. Gelatinous Zooplankton includes a variety of
fragile, jelly-like organisms which are not
closely related taxonomically.

• Cnidarians jellyfish
• Characteristics
• Very simple body structure, with 3 layers inner
  membrane, jelly, and outer membrane.
• No internal organs but have a digestive cavity.
• Have stinging cells on their tentacles called
  nematocysts.
• Habitat Found everywhere and at all depths. More
  abundant in surface waters.
• Role in food web Carnivores, trap prey in
  tentacles.
• Ctenophores "comb jellies".
• Characteristics
• Also have a simple body structure without
  internal organs.
• Move by means of cilia,.
• Sometimes have 2 long tentacles.
• Are often bioluminescent.
• Habitat Found everywhere
• Role in food web Carnivores, predators.
• Salps A type of tunicate.
• Characteristics
• Members of the phylum Chordata.
• Have a complex body structure including internal
  organs and a nervous system as larvae but are
  "degenerate" as adults.

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5. Pteropods

• Characteristics
• Mollusks related to snails.
• Small, 1 cm long.
• May or may not have a conical shell.
• Move by means of "wings" (modified foot).
• Habitat Found everywhere
• Role in food web May be herbivores or
  carnivores. Filter-feed using a "mucous net".

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6. Meroplankton

• Meroplankton are organisms which are part of the
  plankton for only part of their life cycle,
  usually an early, larval stage.
• As adults the meroplankton are benthos (including
  intertidal organisms) or nekton.
• The meroplankton often do not resemble the adult
  forms, to the extent that some were once thought
  to be separate species.
• Meroplanktonic larvae promote survival of the
  species
• Currents carry the offspring to new areas,
  especially important for sessile (immobile)
  benthic animals. Thus, the offspring do not
  compete with the parents for scarce resources
  such as food or space. Also, local "disasters"
  will not wipe out all close relatives.
• Meroplankton live in surface waters where food is
  abundant. Sometimes, the habitat of the adult
  would not have enough food, especially for a very
  small organism that could not effectively use the
  feeding strategy (for example, predation, filter
  feeding) of the adult.
• Meroplanktonic larvae also have disadvantages
• Often, reproduction occurs to coincide with the
  spring bloom and abundant food. If the spring
  bloom is not "on time", meroplankton may starve.
• Meroplankton are food for the many predators on
  plankton.
• The currents may not carry the meroplankton to an
  area that provides suitable conditions for
  adults.
• Therefore, organisms which have meroplanktonic
  larvae usually produce hundreds or thousands of
  eggs, so that a few will survive.

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4. Summary

• (1) Plankton are drifting organisms at the mercy
  of the currents.
• (2) There are 3major groups of plankton,
  phytoplankton, the main primary producers of the
  ocean bacterioplankton, which can be either
  primary producers or decomposers and
  zooplankton, which are animals.
• (3) The four major groups of primary producers
  (autotrophs) in the ocean are
• diatoms, golden-brown algae with siliceous
  frustules that are commonest in cold,
  nutrient-rich water
• coccolithophores, algae that are covered with
  small, calcareous plates (coccoliths) and are
  commonest in warm, tropical waters.
• dinoflagellates, red or brown algae that usually
  have hard coverings of cellulose and are motile
  by means of a flagellum. They are commonest in
  summer and fall in the temperate zone of the
  oceans, and can cause PSP.
• cyanobacteria (blue-green algae) are really
  bacteria that are photosynthetic primary
  producers, commonest in nutrient-depleted areas
  of the open ocean.

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Copepod

• http//www.bigelow.org/amt/copepod.jpg

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Naupilus Larva

• http//www.onlineenzyklopaedie.de/Images/1/180px-n
  aupilus.jpg

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Oyster Trocophore Larva

• http//www3.csc.noaa.gov/scoysters/images/bio/life
  cycl.gif

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Polychaete Larva

• http//www.amonline.net.au/exhibitions/beyond/imag
  es/400/d020.jpg

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Horseshoe crab larva