Phaeophyta Brown algae, Kelp, and Seaweeds – Protista

Lauren Ord

Interesting Facts The giant kelps are the largest of the Phaeophyta and can growth over 100

meters long. Other examples of Phaeophyta include many types of seaweed. Phaeophyta live in marine habitats and grow in the colder parts of the ocean

and in the rocky intertidal zone. Phaeophyta are used in foods, animal feeds, and fertilizers and as a source

for alginate, a chemical emulsifier added to ice cream, salad dressing, and candy.

Phaeophyta have the brown accessory pigment fucoxanthin and store sugar as the carbohydrate laminarin. They also contain both chlorophylls a and c.

A typical heterokont eyespot is present in most, but a few species lack this eyespot.

Fucus

Macrocystis - Giant kelps

Sargassum

Key Features

The thallus or body of kelp includes the holdfast, which anchors the plant, the stipe which supports the blades, and the blades or fronds, which are used for photosynthesis.

Phaeophyta has a cell wall with an inner cellulose layer, gelatinous pectic layer, containing algin which absorbs and retains water. This is vital to Phaeophyta that live in intertidal zones.

Many large kelps use gas-filled floatation bladders to keep their large blades near the surface so that they can perform photosynthesis.

Structure of Kelp

The Life Cycle

Reproduction can occur in three different ways with Phaeophyta. It is either isogamous, anisogamous, or oogamous.

The life cycle of most Phaeophyta is alternation of generations where physiologically independent haploid gametophyte plants produce gametes. When these gametes fuse, the diploid sporophyte generation begins. The sporophyte produces haploid spores which develop into new gametophytes. The two generations could be indistinguishable in size and form or they might be very different.

Uses of PhaeophtyaPhaeophyta are used by humans as a

source of food and to make products. Phaeophyta are also an important part of food chain and provide fish and animals a marine habitat.

From the cell wall of Phaeophyta, a gel forming substance is obtained called algin. Algin is used to manufacture chemicals. Alginates are used as thickening agents and stabilizers in the production of food and drugs in industries such as food, paper, pharmaceutical, textile, and welding.

Brown algae such as rockweed or Fucus and Sargassum float in a thick tangled mass through the Sargasso Sea, which supports a variety of marine organisms.

Sargassum and Young Loggerhead Turtle

Phaeophtya Uses