Protists
• Dinoflagellates (Red tide, Zooxanthellae,
Pfisteria)
• Diatoms
• Cocolithophores
• Radiolarians
• Foraminiferans
• Algal blooms
Dinoflagellates
• marine protists, some freshwater
• mostly unicellular
• half are photosynthetic- primary producers of aquatic food
chains
• some live in mutualistic relationships with cnidarians,
some are parasitic, some are carnivorous
• two flagella- one transverse (lateral) and one longitudinal
(posterior)
• move in a whirling motion caused by transverse flagellum
• have a submembrane made of cellulose--makes an “armor”
Red Tide
• Certain dinoflagellates cause
large algal blooms in warm
coastal waters (such as along
the east coast and in the Gulf
of Mexico)
• turn the water reddish brown
because of xanthophylls in
the chloroplasts
• Shellfish eat the blooms and
concentrate toxic compounds
released by the dinoflagellate
cells--toxic to other
organisms
Zooxanthellae
• golden-brown endosymbiont (lives inside) of marine
organisms, especially anthozoans (coral)
• typically dinoflagellate algae, but sometimes diatoms
• aquired by ingestion
• reproduce asexually by budding
• autotrophs
• gives coral 98% of its energy--in return is given protection,
shelter, CO2 for photosynthesis- symbiosis
Pfisteria
• found in Pamlico and
Neuse Rivers in NC
• complicated life cycle- 24
physical forms, and can
change forms quickly
• most are non-toxic, but
some have forms in their
life cycles that are toxic
• two toxins have been
identified that can cause
skin lesions and are
neurotoxins
Diatoms
•
•
•
•
phylum Bacillariophyta
eukaryotic algae
unicellular, but some form colonies
cell wall made of hydrated silica in organic matrix
called a frustule
• marine and freshwater
• yellow or brown in color
• asexual or sexual reproduction- sperm only flagellated
cells in this phylum
Cocolithophores
• algae, protists, and
phytoplankton in class
haptophytes
• have calcareous (calcium
carbonate) shells- called
cocoliths
• index fossils- used to
solve stratigraphic
problems
• also nanofossilsindicators of salinity and
temp. changes on ocean
surface
Radiolarians
• phylum Actinopoda- “ray
feet”
• marine
• shells made of silica
(glass)
• after radiolarians die, their
shells settle on the sea
floor and decompose into
a siliceous ooze
• often contain symbiotic
algae like zooxanthellae
Foraminiferans
• marine-live in sand or attached to rocks and algaealso some families abundant in plankton
• have porous shells- “Foraminifera” means “to bear
little holes”
• shells are multichambered, made of organic material
hardened with CaCO3
• cytoplasm extends through pores- aids in swimming,
shell formation, feeding
• symbiotic algae often lives under shells
• 90% are fossils
Algal Blooms
• rapid increase in the
population of algae in an
aquatic system
• blooms of dinoflagellates
cause red tides- produce
neurotoxins
• some algal blooms caused
by an excess of nutrientsalgae uses up all O2 and
other organisms can’t
survive (eutrophication, in
freshwater lakes)
Sources
• Campbell, Neil A. Biology: Third Edition.
Benjamin/Cummings Publishing
Company: New York, 1993.
• Wikipedia.