Marine Algae Marine Biology Unit #2

Unicellular Algae  The unicellular algae show plant-like and animal-like characteristics.  Algae are eukaryotic, photosynthetic organisms.  Unicellular algae are included in the Kingdom Protista.

Unicellular Algae  Diatoms:  Diatoms are efficient photosynthetic factories, producing much-needed food, as well as oxygen for other forms of life.  They are very important open water primary producers in temperate and polar regions.

Unicellular Algae  Dinoflagellates:  They are more common in the tropics.  Responsible for huge blooms called red tides.  Dinoflagellates are also noted for the production of bioluminescence.

Multicellular Algae  Commonly called “Seaweeds.”  More complex than unicellular algae.  Being algae, seaweeds lack the true leaves, stems, and roots of the higher plants. Body is a thallus.  Three types of seaweeds are the green, brown, and red algae.

Seaweed Structure  The general structure of seaweed is analogous to land plants, but being algae, seaweed lack the true leaves, stems, and roots.  Blades –  huge surface are for photosyntesis  Pneumatocysts –  gas-filled bladders for bouyancy  Stipes –  growth and flexibility  Holdfast –  anchorage to substrate

Seaweed Structure

Division Chlorophyta  Green Algae (major oxygen producers)  Mostly freshwater and terrestrial  Most are unicellular and filamentous  Some marine species are multicellular  Found in shallows

Division Rhodophyta  Red algae.  Grow deeper than other algae.  There are more species of marine red algae than of green and brown algae combined.  Coralline red algae deposit calcium carbonate which helps form and develop coral reefs.

Division Phaeophyta  Brown Algae (commonly called “Kelp”)  Almost all marine.  Major primary producers on temperate rocky coasts.  Macrocystis – “giant kelp”  Form kelp forests.

Division Phaeophyta

Kelp Forests

 Enormous primary productivity, analogous to a terrestrial tropical rain forest in their complexity.  Kelp forests are the basis of recreation and fisheries on North America’s west coast.  In the colder waters of the north and south Atlantic and Pacific Oceans, kelp beds, or forests are formed when many plants, each with many fast-growing and intertwined stripes form dense and very productive regions.

Kelp Forests

Uses for Seaweeds  Harvested seaweed is used in many ways. The most obvious is as a food source.  The farming, or mariculture, of seaweed is big business in China, Japan, and Korea.  Alginates (from brown algae)  Carrageenan (from red algae)  These compounds are used as stabilizers and emulsifiers  ice cream, cheese, and topping  shampoo, shaving cream and cosmetics  plastics and pesticides