IB 362 Lecture 16 Seaweeds, algae, marine grasses

IB 362 Lecture 16Seaweeds, algae, marine grasses

Algae – a diversity of protist organisms, the most conspicuous of which are called seaweeds

Others can be single celled, or they can form an encrusting layer on rocks

Marine Biology: Function, Biodiversity, Ecology, 3/e

Levinton Copyright © 2009 by Oxford University Press, Inc.

FIG. 12.1 Some of the diversity of form of seaweeds: (a) the green seaweed Ulva (ca. 25 cm high), (b) the green seaweed Codium fragile (ca. 30 cm high), (c) the red coralline alga Corallina (ca. 1 cm tall), (d) the red seaweed Polysiphonia (ca. 25 cm high), and (e) the brown seaweed Laminaria (ca. 2 m long).

Seaweeds – actually are PROTISTS but are colonial and look plantlike

Green seaweeds (Chlorophyta)

Sea lettuce (Ulva)Codium (invasive via oyster culture)

Brown seaweeds (Phaeophyta)especially kelps (Laminaria and Macrocystis)Fucus (intertidal)Sargasso weed

Red seaweeds (Rhodophyta)

Ulva(sea lettuce)



FIG. 12.6 The green seaweed Codium fragile, attached to a stack of the snail Crepidula fornicata, and stranded on a beach on Long Island, New York. (Photograph by Jeffrey Levinton.)



FIG. 12.2 The intertidal brown seaweed Fucus gardneri often completely dominates protected rocky shores of the Pacific coast of the United States and Canada. (Photograph by Jeffrey Levinton.)



FIG. 15.1 A bed of Zostera marina in Padilla Bay, Washington. Blades of this sea grass are 50–100 cm high. (Photograph courtesy of Charles Simenstad.)



FIG. 15.8 A kelp forest in the Aleutian Islands: Cymathere triplicata (foreground); Alaria fistulosa (rear). (Courtesy of David Duggins.)



FIG. 15.18 Succession in an Alaskan kelp forest. Eventually (bottom) the kelp Laminaria groenlandica dominated the forest and prevented taller species from reinvading by shading out juveniles. (Courtesy of David Duggins.)



FIG. 15.14 Two alternative stable states in kelp forests. (a) Luxuriant kelp growth, with urchins that are sedentary and trap drift algae on the dorsal surface. (b) A storm has stripped the kelps, and urchins rove about the bed, denuding the bottom of all potential new recruiting kelps.

Some commercially important seaweeds

Ulva – sea lettuce (can be eaten fresh in salads

Purple laver (Porphyra)– boiled and made into cakes in UK, or cooked as a vegetable

Dulse (Rhodymenia) – used in cooking

Irish moss (Chondrus) – used in cooking (carageenin – emulsifier – esp. dairy products)

Kelps (especially Japan) – called kombu, wakame (also for algin, used as a stabilizer and emulsifier)

Nori (Porphyra) – used to make sushi (and also in soups)

Sea grasses – actually ARE flowering plants – can be dominant organisms in some area, not only as primary producers but as stabilizers of sediment and also providers of cover for small (especially juvenile) animals

Pollen transported by water



FIG. 12.8 The surf grass Phyllospadix sp. on the outer coast of British Columbia. (Photograph by Jeffrey Levinton.)



FIG. 12.9 A turtle grass (Thalassia testudinum) bed, Florida. (Photo by Jeffrey Levinton.)



FIG. 15.3 The scallop Argopecten irradians lives as a juvenile attached to eelgrass blades, which reduces predation by crabs.



FIG. 12.10 Pollen release by sea grass, Zostera marina. (Photo by Paul Cox.)



FIG. 15.2 Scheme of succession from bare sand to a Thalassia testudinum sea grass bed in coastal Florida waters. (Courtesy of Susan Williams.)

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IB 362 Lecture 16 Seaweeds, algae, marine grasses