Brown Algae Sargassum wightii Phaeophyta

Introduction to Algae Algae are grouped as photosynthetic organisms that are not quite plants. They belong to the Sub-Kingdom Thallophyta They lack organized tissues, like leaves, roots and the complex vascular structure of higher plants.

Algae are divided into several phyla on the basis of several characteristics There are three groups that are distinguished based on their color. Green algae Phylum Chlorophyta Red algae Phylum Rhodophyta Brown algae Phylum Phaeophyta

Characteristics of the Group

Brown Algae (Phaeophyta) are the largest and most complex of algae. are multicellular. are macroscopic with no unicellular or colonial forms. belong to a very large eukaryotic group of organisms that are distinguished by having chloroplasts surrounded by four membranes called Heterokontophyta.

Almost all brown algae are attached. Phaeophytes contain the requisite photosynthetic pigments, chlorophyll a and c. They are characteristically brown due to the accessory carotenoid pigment fucoxanthin.

Characteristic Structures

- Thallus – refers to the whole algal body - Holdfast – attaches the thallus to the substrate; like the root - Stipe – flattened, erect stem-like stalk

- Blades – leaf- like structures - Frond – leaf- like structures - Bladders – gas-filled swellings which float and keep the algae upright in water

Habitat

Habitat Brown algae have adapted to a wide variety of marine ecological niches including the tidal splash zone, rock pools, the whole intertidal zone and relatively deep near shore waters.

Habitat Most brown algae are marine, commonly found in cool, shallow coastal waters of temperate of arctic areas. Many brown algae grow along rocky seashores.

Nutrition

Nutrition Brown algae are photosynthetic. They absorb nutrients from the water.

Reproduction

Reproduction Brown algae do not produce flowers, which is why they reproduce instead through variations on alternating between generations of sexual and asexual spore reproduction “alternation of generations” They reproduce by means of flagellated spores and gametes that closely resemble cells of other heterokonts.

 Ectocarpus  life cycle At right are sporophyte generations exhibiting two types of sporangia: (c) unilocular and (j) plurilocular. In the unilocular form, (a), meiosis occurs, (b), followed by mitotic divisions, (c). Haploid meiospores (d) are released, producing gametophytes, (e) and (f). Gametes fuse, (g), producinag zygote, (h), which grows intoa new sporophyte plant, (i).T he sporophyte at (i) is diploid and may produce a plurilocular sporangium (j). This sporangium produces diploid spores, (k) , which grow to new sporophytes, (I), thus circumventing alternation of generations. http://www.eplantscience.com/botanical_biotechnology_biology_chemistry/introduction_to_botany/reproduction_in_brown_algae.php

Ecology

Ecology They stabilize the captive environment by introducing beneficial microbes, absorbing nutrients, and producing metabolites that mediate systems biologically. They are good as bio-indicators, showing signs of degrading water quality.

Ecology Food; almost all fishes and invertebrates eat algae. They play the role of producers in many marine ecosystems. They may serve as habitat/ornament to break up the environment physically, providing hiding space and beauty.

Three Species

Ascophyllum nodosum Rockweed/Norwegian Kelp/Knotted Kelp/Knotted Wrack/Egg Wrack

Ascophyllum nodosum - is a large common brown alga in the family Fucaceae - is the only species in the genus Ascophyllum - is seaweed of the northern Atlantic Ocean - has long fronds with large egg-shaped air- bladders set in series at regular intervals in the fronds and not stalked.

Durvillaea antarctica Cochayuyo

Durvillaea antarctica - is a large bull kelp species - is the dominant seaweed in southern New Zealand and Chile - is found on exposed shores, especially in the northern parts of its range

Durvillaea antarctica - attaches itself with a strong holdfast - does not have air bladders, but floats due to a unique honeycomb structure within the alga’s blades

Macrocystis pyrifera Giant Kelp/Giant Bladder Kelp

Macrocystis pyrifera - a species of kelp - one of four species in the genus Macrocystis - perhaps the largest, fastest growing organism on the planet - up to two hundred or so feet long - grows up to two feet more a day

Trivias

The legendary Sargasso Sea in the middle of the North Atlantic is characterized by the presence of brown algae from the genus Sargassum that floats in masses on the surface.

Sargasso Sea

The oldest examples of fossilized brown algae date back to the Mesozoic Era (251 to 180 million years ago). The 1,500 species of brown algae are almost exclusively found in marine habitats. The brown algae include the largest of the seaweeds, Durvillea and the kelps, found in cold waters. 

Sources http://en.wikipedia.org/wiki/Brown_algae http://www.wetwebmedia.com/brnalgae.htm http://en.wikipedia.org/wiki/Ascophyllum http://en.wikipedia.org/wiki/Durvillaea_antarctica http://www.mbari.org/staff/conn/botany/flora/br owns.htm http://www.aquaticcommunity.com/algae- control/brown.php Biology by Miller and Levine