Download Chapter 4 Unicellular Marine Organisms

Unicellular Marine
Organisms
Bacteria
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Most abundant organisms on earth
Widely distributed in the ocean
Microscopic single-celled organisms
Three basic shapes:
Coccus = round
 Bacilli = rod shaped
 Spirilla = corkscrew
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Decay bacteria
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Bacteria break down organic matter into smaller
molecules that are released into the ocean
Called “Decomposers”
Most abundant in bottom sediments where dead
matter accumulates
Thrive in warm, moist, dark and nutrient rich
environments
Chemosynthesis- process by which sulfur
bacteria derive energy from chemicals
Blue-Green Bacteria
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Cyanobacteria- type of bacteria that contain
chlorophyll and lack a membrane bound nucleus
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The only bacteria that are photosynthetic
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Found throughout the oceans and are very hardy
Diatoms
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Among the most common organisms in the
ocean
Single-celled protists that usually float or drift
near the surface
Classified as phytoplankton (“plant wanderers”)
Contain chlorophyll and perform photosynthesis
Have cell walls made of silica
Diatom Diversity and Life Functions
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Over 25,000 species of diatoms
Most are found in the cold waters of the world
Classified in phylum Chrysophyta (“golden algae”)
Classified according to their shape
Round = centric diatoms
 Pen-shaped = pennate
 Spines = shape that prevent sinking
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Can reproduce asexually or sexually
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When diatoms die, their glassy cell walls remain and
accumulate on the sea floor
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Layer of these deposits are called diatomaceous
earth (excellent filtering material)
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Almost all animals in the sea ultimately depend on
diatoms for food
Problems from Diatoms
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Algal blooms- sudden increase in diatom
populations
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Brown tide- water becomes so clouded with
algae that the waters turn brown
Dinoflagellates
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Another group of protists often found near the
surface
Classified in phylum Pyrrophyta “red (or fire) algae”
Have two flagella that help move the dinoflagellate
along (diatoms cannot propel themselves at all)
Contain chloroplasts and can make their own food
Have cell walls made of cellulose like plants
Effects of dinoflagellates
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Bioluminescence- ability of an organism to
produce light
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Noctiluca have the ability to emit a greenish-blue
light when stimulated
Red Tide
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Water suddenly turns a reddish color with no
warning
Occurs because of a sudden explosion of the
Gymnodinium dinoflagellate population
Toxins released by the organisms accumulate in
shellfish that eat the algae
In turn, the organisms that feed on the shellfish
(fish, marine birds, humans) are poisoned
Algal bloom also reduces oxygen levels in the water
which contributes to a fish kill