Marine Algae

A Broadly Applied Name

Algae are the ocean counterparts of plants,

accounting for as much as 90% of the Earth’s primary productivity and oxygen production. Algae are the foundation for all marine life.

Taxonomic Definition: those organisms that belong in one of seven specific phyla to classify algae.

Seven phyla of algae: Cholorphyta, Rhodophyta, Phaeophyta, Dinophyta, Bacillariophyta, Euglenophyta, Chrysophyta

What are algae? How many phyla of algae are there?

- Most productive phytoplankton; very

diverse group (5,000-50,000 species)- Larger than prokaryotes- Shell made of silicon that comes in an

array of shapes among the species- Relatively dormant through winter

months because they are photosynthesizers

- When sunlight levels rise in spring, they photosynthesize, grow, and reproduce

- Reproduce asexually: budding- Account for about 25% of all

photosynthetic biomass on Earth- Can cause: Harmful Algal Blooms

(HABs) by producing toxins

Phylum: Bacillariophyta: The Diatoms

Second most productive group of primary producers Use flagella to swim; just a little larger than diatoms;

still small enough to be classified as microplankton Noctiluca: heterotrophic dinoflagellate; capable of

bioluminescence: ability of an organism to emit light (firefly); contain chemicals in photophore that when mixed emit light;

Use this light to attract prey, fool predators, attract mates, and sometimes as light source for vision

Noctiluca emit light when agitated Genus Symbiodinium: autotrophic dinoflagellates; live

in coral polyps; provides food for the coral polyps; example of mutualism: two species live together and benefit from the relationship; coral could not exist without these dinoflagellates

Also live in giant clams and some species of sponge

Phylum Dinophyta: The Dinoflagellates

Dinoflagellates can also cause toxic red

tides (HABs) Toxins can be even more toxic than cyanide These toxins can accumulate over time in

shellfish and fish and can cause seafood poisoning

Fish at higher trophic levels have a higher toxin risk due to the accumulation of toxins with each level and more concentration as you go up

Dinoflagellates: Cont’

Phylum Chlorophyta: Green

Algae Macro Algae: applies to

several algae phyla, but refers to multicellular species

Share same green color as land plants

Share the same pigments and have many similar biochemical characteristics: chlorophyll a & b

Chlorophyll a: pigment directly involved with photosynthesis

Chlorophyll b: assists chlorophyll a in capturing light for use in photosynthesis

7,000 species of green algae Do not have system of roots,

veins, and stems that land plants have

Some species have holdfasts: appendages that look like roots, but simply anchor the algae to rocks; don’t carry nutrients

Green algae vary in complexity within the classification, ranging from single cell to multi cell varieties

Consists of freshwater and marine algae; 4,000 species; mostly macro algae; do not produce cellulose Have chlorophyll a but NOT chlorophyll b Have red pigments: phycoerythrins which give color This pigment has not been found in any other eukaryote; does exist

in cyanophytes This pigment allows red algae to live deeper than any other algae;

some as deep as 200 meters (656 ft) Also important for coral reefs; think of red algae as cement for

building coral reef wall Red algae secrete calcium carbonate shell which bond individual

coral colonies and debris together which in turn holds the coral reef structure together

Not all red algae do this Some eat red algae of certain genera; rich in protein and minerals

Phylum Rhodophyta: Red Algae

More complex than other algae Brown algae have holdfasts, blades (which are equivalent to

leaves) Many species live in the littoral zone, so stipes bend easily to

resist breakage by waves Pneumatocysts: natural gas-filled float structures that lift the

algae off the bottom; also resist drying out which helps them when stranded partially or wholly above surface during low tides.

1500 species with the largest and most impressive are the various species of kelp;

Not all Brown Algae live anchored by holdfasts For example: Sargassum genera: brown algae that thrives on the

surface of the Sargasso Sea

Phylum Phaeophyta: Brown Algae

Giant kelp can grow more than 30 cm per day

and reach the surface from 79 ft deep It is important because it is the foundation

for many temperate coastal ecosystems; much like coral is the foundation for many tropical marine ecosystems

Kelp forests dominate the coasts of California, Mediterranean, and New Zealand

Why is kelp important?