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Overview

Brief Summary

Brown seaweeds get their color because they contain a brown pigment which dominates over the green chlorophyll. They are generally large sturdy plants and don't grow in warmer waters. They are tough and easily withstand lots of wave motion. Brown seaweed can form unique underwater habitats. Some species have bladders filled with air, helping them to float or stand up straight. They often wash ashore in large bunches. All kinds of smaller seaweed species and marine animals live among these bunches. There are around eigthy species of brown seaweed found in the Netherlands. Brown seaweed in the flood mark makes good fertilizer for orache species, such as frosted orache.
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Distribution

Phaeophyceae can dominate the rocky subtidal and intertidal of temperate regions, where, though the species diversity is lower than that of the red algae, their numbers are much higher. The “Sargasso Sea” is the only area in warm waters where Phaeophyceae is abundant – as large “rafts” of floating Sargassum. (Lee, 1999).

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Physical Description

Morphology

“There are no unicellular or colonial organisms in the order, and the algae are basically filamentous, pseudoparenchymatous, or parenchymatous.” (Lee, 1999)

See also: algaebase.org Phaeophyceae

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Size

Visible thalli range from a few centimeters to over 45 m (150 ft), depending on species and environmental conditions. The gametophytes of species with heteromorphic alternation of generations are microscopic. (Connor & Baxter, 1989).

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Ecology

Habitat

Phaeophyceae are nearly all marine and most occur on rocky substrates in the upper littoral zone and the low to mid intertidal. There are only four genera with freshwater species, however, several marine taxa can also occur in the brackish water of saltmarshes. (Lee, 1999)

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Life History and Behavior

Life Cycle

There are three general types of life history among the Phaeophyaceae: isomorphic alternation of generations, heteromorphic alternation of generations, and diplontic (see diagrams among images). (Graham & Wilcox, 2000)

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Reproduction

Sexual and vegetative, with three general life history classes: isomorphic alteration of generations, heteromorphic alternation of generations, and diplontic. Populations occurring in brackish waters have almost totally lost their ability for sexual reproduction. Their primary method of propagation is vegetative.

(Lee, 1999; Graham & Wilcox, 2000).

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Evolution and Systematics

Evolution

Systematics and Taxonomy

This is still debated. Some classify Phaeophyceae as a phylum (aka “division”) within the kingdom Plantae, whereas others place it in the taxonomically narrower kingdom “Chromista.” Some algal biologists use the term “Phaeophycean” and place that in the higher taxon “Ochrophytes.” Others classify Phaeophyceae within the “Heterokontophyta.”

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Physiology and Cell Biology

Cell Biology

Cytology

Cell wall: generally contains cellulose (1-10% of thallus dry-weight), alginic acid, and sulfated polysaccharides

Plastids: varies among genera – may be from one to many per cell; typically have a girdle lamella; have a periplastidal endoplasmic reticulum, which is continuous with the nuclear envelope

Pigments: fucoxanthin, which gives the algae their characteristic greenish-brown color; chlorophyll a; chlorophylls c1 and c2; beta-carotene; and violaxanthin

Photosynthetic reserve product: laminarian

(Lee, 1999; Graham & Wilcox, 2000)

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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage

Barcode of Life Data Systems (BOLD) Stats
                                        
Specimen Records:6,693Public Records:2,979
Specimens with Sequences:3,338Public Species:99
Specimens with Barcodes:3,185Public BINs:372
Species:612         
Species With Barcodes:369         
          
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Barcode data

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Locations of barcode samples

Collection Sites: world map showing specimen collection locations for Phaeophyceae

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