Diversity of Aquatic Organisms Phytoplankton (Photosynthetic plankton, Mostly algae) Part 2

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Diversity of Aquatic OrganismsPhytoplankton
(Photosynthetic plankton, Mostly algae) Part 2
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Characteristics of Algae

• Eukaryotic cells
• Single Cellular or Multi-cellular
• Colonies, cells have limited coordination and
  specialization
• Most are aquatic but, some are not
• Lichen (fungus algae)

webs.wichita.edu/mschneegurt/biol103/lecture08/lic
hen_micro.jpg
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Characteristics of Algae

• Most are are non-vascular and do not have tissues
  but
• Kelps and other seaweeds may have some degree of
  specialization in structures. Still, they do not
  have roots, stems, or leaves

http//www.onr.navy.mil/Focus/ocean/images/habitat
s/kelpai.jpg

• Most are photosynthetic, but
• some are heterotrophic (colorless, parasitic)
• Simple reproductive cells

Pfiesteria
www.pfiesteria.seagrant.org/
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Where is algae found in lakes?

• On the bottom (Benthic or epipelic algae)
• Good access to nutrients in sediments, but can
  only be in shallow water due to light limitation
• epilithic - rock
• epipsammic - sand
• Attached to aquatic macrophytes (Periphyton)
• Algae and animals form a community (the Aufwuchs)
  in the slime on stems of aquatic plants
• In the water column (Phytoplankton)

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A Note On Terminology

• Seston - all particulate matter
• bioseston - living
• tripton (detritus) - non living
• Nekton - organisms that create turbulence - fish
• Plankton - organisms that are influenced by
  turbulence
• Euplankton (truly planktonic)
• phytoplankton (i.e., planktonic algae)
• zooplankton - protozoans, arthropods, rotifers

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A Note On Terminology

• meroplankton - periodically enter the plankton.
  Cant pass whole life history in the water
  column, live also in benthic habitats - (insect
  larvae, dreissenid veliger larvae)
• Benthos
• phytobenthos
• zoobenthos

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Phytoplankton

• Pigments
• Often used to categorize phytoplankton
• All photosynthetic algae possess photosynthetic
  pigments.
• Chlorophylls - Chla in all algae also b and c
  (green pigment)
• Carotenoids - carotenes, xanthophylls (brown,
  gold, red)
• Phycobilins - pigment - protein complexes (blue
  and red)
• Similar pigments usually indicates evolutionary
  relationships
• Special adaptations
• Flagellae
• motility (slight) and feeding current generation

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Phytoplankton

• Gas vacuoles
• Buoyancy control (especially in blue-green algae)
• Modes of feeding
• Photosynthesis (autotrophy)
• Heterotrophy (metabolism of organic substrates)
• Mixotrophy - both occur in the same organism.
• Some algae graze on bacteria, then switch to
  photosynthesis.
• Nutrition
• General need for nitrogen and phosphorus.
• Si required by diatoms
• N-fixation in blue-green algae
• vitamins - many have a requirements for B12
• These requirements help determine where and when
  certain algae occur

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Taxonomic Survey of Algae

• Blue-Green Algae
• Division Cyanobacteria
• Oldest photosynthetic organisms on Earth
• Prokaryotic
• No organelles (organized nucleus, mitochondria,
  chloroplasts, etc)
• Functionally and physically similar to algae
• Cellular structure similar to bacteria
• Nutrition
• Need 6 mg/L Na
• Do well at high pH
• Some can fix molecular nitrogen (N2)
• May produce toxins (hepatoxins, PSTs)
• Pigments
• Chlorophyll a,
• Phycobilins - Phycoerythrin (red), Phycocyanin
  (blue)

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Blue-green Algae (Cyanobacteria)

• Important Structures
• Akinites
• Thick-walled resting stage, daughter colony
  inside
• Heterocysts
• Chlopophyll-free cells for N2 fixation
• Gas Vacuoles
• Can be produced or destroyed to change cell
  buoyancy

Akinite
Gas Vacuoles
Heterocyst
expasy.org/spotlight/images/sptlt023.jpg
www.bact.wisc.edu/Microtextbook
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Blue-green Algae (Cyanobacteria)

• Common Genera

Oscillatoria
Aphanizomenon
www.micrographia.com
Anabaena
Microcystis
Chroococus
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Cyanobacteria Blooms in Lake Erie

• Lyngbya wollei
• Recent problem in Lake Erie (2006)
• Grows on bottom in shallow waters
• May Produce PSTs
• Mats float to surface and wash ashore
• Severe disruption of shoreline, nuisance to
  property owners and beach users

• Microcystis sp.
• Blooms form in June-Sept
• Produces Microcystin toxin
• Disrupt recreational use of lake
• Algae washes ashore and decays
• City of Toledo spends 4K/ day to remove
  Microcystis from drinking water supply

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Green Algae (Chlorophyta)

• Characteristics
• Eukaryotic
• Divide by mitosis, may undergo sexual
  reproduction
• produce haploid gametes (flagellated male and
  female cells)
• Pigments
• Chlorophyll a and b organized in chloroplasts
• Carotenoids in some species
• Very Diverse
• Typical lake may have 80-100 phytoplankton
  species (1/2 of them are green algae)
• Most similar to higher plants

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Green Algae (Chlorophyta)

• Examples
• Volvox sp.
• colonial
• Flagellated cells in mucilage matrix
• Daughter colonies within parent colony

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Colonies in black dye to highlight mucilage
matrix