PLANTLIKE PROTISTS: UNICELLULAR ALGAE

§    plantlike protists are commonly called "algae"

§    contain the green pigment chlorophyll and carry out photosynthesis

§    highly motile or are able to move about freely

Chlorophyll and Accessory Pigments

§    classified by the type of photosynthetic pigments they contain

§    a shortage of light is a major problem for deep water algae

§    sea water absorbs large amounts of red and violet light

§    chlorophyll a is the best at capturing red and violet light

§    forms of chlorophyll include:

►       chlorophyll a

►       chlorophyll b

►       chlorophyll c

§    accessory pigments are compounds that absorb light at different wavelengths than chlorophyll

►       give algae a wide range of colors

Chrysophytes

§    phylum Chrysophyta includes the yellow-green algae and the golden-brown algae.

§    contain bright yellow pigments

§    means "golden plants"

§    cell walls contain pectin rather than cellulose

§    store food in the form of oil rather than starch

§    reproduce both asexually and sexually; most are solitary

Diatoms

§    phylum Bacillariophyta or diatoms are most abundant and beautiful organisms on Earth

§    cell walls are rich in  silicon (main component of glass)

§    form diatomaceous earth used in polishing metals or insulation/filtration

                        Two groups:  Centric - circular, common in oceans

                                               Pennate - rectangular, common in fresh                                                                       water ponds and lakes

Dinoflagellates

§    phylum Pyrrophyta are dinoflagellates

§    half are photosynthetic and half are heterotrophic

§    2 flagella that wrap around the organism in cellulose grooves that protect the cell

§    luminescent and when agitated by sudden movement give off light, hence the name "fire plants"

Ecology of Unicellular Algae

§    common in both fresh and salt water

§    make up a considerable part of the phytoplankton

§    phytoplankton are small, photosynthetic organisms found near the surface of the ocean.

§    half of the photosynthesis is carried out by phytoplankton

§    nourishment for shrimp and whales

Algal Blooms

§    many protists grow rapidly in regions where sewage is discharged

§    when waste is excessive, algae may grow in enormous masses known as blooms

§    blooms deplete the water of nutrients, and cells die in great numbers

§    decomposition of dead algae robs water of oxygen, choking resident fish and invertebrates

►       great blooms of the dinoflagellates Gonyaulax and Karenia have recently occurred on the east coast of the US.

►       known as "red tide"

►       produce a potentially dangerous toxin

►       filter-feeding shellfish such as clams eat the algae and become filled with the toxin humans and fish can become seriously ill, paralyzed or even die from eating shellfish infected with red tide