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Types of Sea Algae

Algae are plant-like organisms that live in watery habitats. They contain chlorophyll and photosynthetic chloroplasts, but lack the root, stem and leaf structure of plants. Many different types of organisms from several different phylogenies and taxonomies are called algae. The aquatic life forms inhabit all the oceans of the world. The majority of algae are microscopic, but some are marine seaweeds growing over 150 feet long.

Diatoms
- Diatoms are tiny, single-celled yellow or brown organisms. They build highly detailed and intricate silicate shells and reproduce asexually by cell division. Most people know diatoms in the form of diatomaceous earth, used as a filter or abrasive. As diatoms die, their shells drop to the bottom of the ocean and accumulate as sediment. Diatom deposits have created most of the world's limestone and much of its petroleum. Huge groups of diatoms appear early in the year during their annual spring bloom.
Green Algae
- Green algae are the most diverse of the algaes. They belong to the division Chlorophyta, with 9,000 to 12,000 species. While most Chlorophyta live in fresh water, there are many marine species, such as sea cabbage, that provide food and oxygen for other ocean dwellers. Green algae species may be single-celled, multicelled or colonial. The organisms reproduce both sexually and asexually. They sometimes are coenocytic, having more than one nucleus per cell. A type of green algae was likely the ancestor of land plants.
Red Algae
- Red algae are marine Rhodophyta that contain pigments called phycobilins, giving them their reddish or purple coloration. They're multicellular branching organisms included in the kingdom Protista. Most sea weeds are a form of red algae and live at greater depths than other algae types. Red algae prefer to live in warmer climates and some species produce calcium carbonate, which plays a major role in reef building. There are 4,000 ocean dwelling species of red algae.
Blue-Green Algae
- Blue-green algae, or cyanobacteria, are genetically unrelated to the other types of algae. Cyanobacteria are prokaryotic (lacking a nucleus) unlike all the rest of the algal groups, which are eukaryotic, with membrane-bound nuclei. The various species can be single-celled or colonial, red, yellow or blue, and may form filaments, sheets or hollow balls. Cyanobacteria contain chlorophyll and are autotrophs, producing their own food, unlike bacteria, which are heterotrophic and must ingest organic material for their nutrition.

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