More algae in the oceans

5. Red algae, or Rhodophyta, or Rhodophyceae.

a. Color striking red, sometimes iridescent due to combination of chlorophylls, carotenoids, xanthophylls, phycoerythrin, and often phycocyanin, leading to plant colorations of red, purple, pink, violet, brown, green, with the deeper species more purely red.

b. The reds live slightly deeper than the browns, down to 150 m (500'); does best in subdued lighting, hence "shade" plants.

c. Small in size, 25 cm (10") tall, with the largest ones up to 1 m (3') tall.

d. Complex life history, with no ciliated or flagellated swimming spores or gametes, which is unusal for an aquatic organism. Larvae dispersal and contact of reproductive cells are thus dependent on currents and/or chance.

e. Most abundant in the temperate seas; widely distributed.
f. Used commercially as a food item in Japan and Ireland, especially in the former.

1). Gelidium or agarweed is used in the production of nitrogen-free agar. 2). Porphyra, which is not quite as iodine-tasting as some of the other plants, is used as nori. Nori is grown on netting attached to poles submerged at high tides in shallow muddy bays; spores germinate and grow on to the netting, within a period of 6 months, when it is collected, chopped, washed, dried, and then pressed into flat sheets (approximately 12" squares); employs 400,000 workers with an annual production in excess of 4 billion sheets. This is the "black" seaweed that is wrapped around rice at sushi bars, known to those who order California rolls, especially. Sometimes, this nori is flavored with soy sauce, but not always. Excellent for the wrapping of rice and for garnishes in soups; not very great for simply eating by itself.

g. 3 lifestyles presented by the reds:

1). crustose (forming a hard, calcareous layer over rocks);
2). coralline, which are usually very short (no more than 10 cm/4 inches tall) looking like a bunch of wing nuts stacked on top of each other; gritty to the touch;

3). soft reds, which is what you would expect any decent plant to look like.

Yellow-green algae, Chrysophyta, Chrysophyceae. This group includes the diatoms, sometimes the dinoflagellates (most consider this a separate division), and the coccolithophores and silicoflagellates.
a. Diatoms are microscopic, unicellular plants that are probably the single most important plant in the ocean as per productivity. They are the main constituent of phytoplankton.
1). Shell, called a frustule, composed of translucent silica; since they are
so abundant, contributes to the depletion of silicon from the surface waters. The shells form a variety of shapes and are deposited in siliceous sediments called called "diatomaceous earth." More than 300 million tons per year are mined in the U.S., primarily in the SW parts. Used in filter ease, filter pads, insulation, tooth paste, tooth powder.

2). Yellow-green pigment called diatomin (may be equivalent of fucoxanthin).

3). Two major forms or types:

a). Pennales, exhibiting bilateral symmetry, characterized by the genus Navicula.

b). Centrales, exhibiting radial symmetry.

4). Reproduction:

a). Binary fission, with both elements of the shell of the mother cell becoming the epitheca (larger half) of each daughter cell; a new hypotheca (smaller half) is grown by each daughter cell.

b). This results in an ultimate reduction in the mean size of the population.

c). After a minimum size is reached, which is genetically
controlled, auxospores are formed, and when conditions are favorable, the diatom leaves the old frustule, expands to the original maximum size, and lays down a new shell of the original maximum size.

d). This might have developed as a response to the diminishing
concentrations of silicon in the upper waters as the population increases.

5). Benthic diatoms--contain heavier frustules; live primarily in shallow, littoral bottoms.

6). Examples: Chaetoceros, Thalassiosira, Nitzschia, Coscinodiscus,Rhizosolenia.

b. Coccolithophores and Silicoflagellates, usually placed with the diatoms under the yellow-green algae.
1). None too prominent, although recent indications are that they are
much more significant than formerly thought. Their small size led to their less than representative collection by standard size plankton nets.

2). Most common genus is Halosphaera