Marine Algae

1. Marine Algae A Broadly Applied Name

2. What are algae? How many phyla of algae are there? • 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

3. Phylum: Bacillariophyta: The Diatoms • 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

4. Phylum Dinophyta: The Dinoflagellates • 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: autotrophicdinoflagellates; 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

5. Dinoflagellates: Cont’ • 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

6. 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

8. Phylum Rhodophyta: Red Algae • 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: phycoerythrinswhich 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

10. Phylum Phaeophyta: Brown 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

11. Why is kelp important? • Giant kelp can grow more than 30 cm per day and reach the surface from 79ft 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