Chapter 7

Multicellular Primary Producers

Seaweeds

• Most found attached to a substrate• Inhibit 2% of seafloor• Life in the inner continental shelf depend upon

seaweeds for food• Abiotic Factors most influential are

– Light *****– Temp***** (most diverse in tropical waters)– Tidal exposure– Salinity– Availability of nutrients

Seaweed Structure

• Thallus-body

• Lack vascular tissue -Do not have roots, stems, or leaves

• Holdfast -The structure that attaches the seaweed to the substrate

• Stipe-stem-like structure

Phylum Chlorophyta (green algae)

• Contain chlorophylls a and b for photosynthesis

• Most are freshwater

• Ecologically important

– food source

– Contribute to coral reef formation

– Some are invasive

Green algae structure

• Most unicellular

• Marine species have coenocytic thallus-containing more than 1 nucleus

– Occurs by cell growing nucleus divides but cell never divides

Reproduction

• Sexual

• Gametes released from gametophyte 2 flagella

• spores released from sporophyte-4 flagella

Representative species

• Halimeda

• Caluerpa-invasive

Phylum Rhodophyta (red algae)

• Primarily marine

• Most diverse among seaweeds

• Cholorphylls a and d, pigments: phycoerythrins and phycocyanins

• Not always red in color- can appear yellow to black

Structure

• Multicellular and less than 1 meter long

• Wide variety of shapes and organization among species

Reproduction

• Can vary from simple to complex…but 2 unique features………..

1. Lack flagella on spores and gametes

2. 3 multicellular stages1. Carpospore-unique

to red

algae

Ecological Roles

• Porphyra- used as food in oriental dishes

• Seasonal food source for urchins, mollusks, fish, and crustaceans

• Some grow on other plants or animals

• Help form base of coral reef

• Agar- used as a thickening agent in foods such as ice cream, pudding, and salad dressings

• Used in cosmetics for creamy foundations

Phaeophyta (brown algae)

• Mostly marine

• Higher diversity than green but less diverse than red

• Size: from microscopic to kelps (100 meters)

• Chlorophylls a and c and pigment fucoxanthin

• Mostly in high latitudes

• Large flat leaf-like blades with bladders help bouy plant toward light

• Representative species Sargassum, Fucus

reproduction

• Gametophyte is eliminated from life cycle (difference from Chlorophyta and

Rhodophyta)

• Egg develops root-like structures (rhizoids) after fertilization

Ecological role

• Habitats for a variety of marine life

• Harvested for thickening agents used in dentistry, cosmetic, and food industries

• Previously iodine was extracted and put into table salt (iodized salt) to prevent a goiter

Phylum Anthophyta

• Seagrasses, salt marsh plants, mangroves

• Ecological Roles- Primary producers, habitats, stabilizing sediments

Sea grasses (marine flowering plants)

• Related to lilies

• Reproduce by pollination of seed; Male and female flowers on separate plants contain pollen

• 12 genra– Genra native to Florida

• Syringodium -manateegrass

• Halophila-paddlegrass

• Thalassia- turtlegrass

• Ruppia-

• Halodule- shoalgrass

Salt Marsh Plants• Adapted to high levels of salinity and tidal action• Found in estuaries – level of succession based on salinity and tidal

tolerance• Species native to Jacksonville

– Spartina Alternaflora– Batis Maritima– Spartina patens– Juncus– Salicornia virginica

Mangroves

• Found in south of St. Augustine to Key West

• 3 genra local to Florida

– Rhizophora mangle –red mangle-----prop roots

– Avicennia germinans – black mangle---pneumatophores

– Laguncularia racemosa- white mangle

• Distinctive by their root system and pods

Mangrove reproduction

• Flowers pollinated by wind or bees

• Embryo grows on the plant in a propagule (similar to seed)

• Propagule eventually falls from parent and is carried by current until it settles and takes root

Black Mangrove

Red Mangrove

Red, White, and Black mangrove leaves

White Mangrove