Ocean Microorganisms: Diversity and Impacts

1. Unicellular Marine Organisms

2. Bacteria • Most abundant organisms on earth • Widely distributed in the ocean • Microscopic single-celled organisms • Three basic shapes: • Coccus = round • Bacilli = rod shaped • Spirilla = corkscrew

4. Decay bacteria • Bacteria break down organic matter into smaller molecules that are released into the ocean • Called “Decomposers” • Most abundant in bottom sediments where dead matter accumulates • Thrive in warm, moist, dark and nutrient rich environments • Chemosynthesis- process by which sulfur bacteria derive energy from chemicals

5. Blue-Green Bacteria • Cyanobacteria- type of bacteria that contain chlorophyll and lack a membrane bound nucleus • The only bacteria that are photosynthetic • Found throughout the oceans and are very hardy

7. Diatoms • Among the most common organisms in the ocean • Single-celled protists that usually float or drift near the surface • Classified as phytoplankton (“plant wanderers”) • Contain chlorophyll and perform photosynthesis • Have cell walls made of silica

8. Diatom Diversity and Life Functions • Over 25,000 species of diatoms • Most are found in the cold waters of the world • Classified in phylum Chrysophyta (“golden algae”) • Classified according to their shape • Round = centric diatoms • Pen-shaped = pennate • Spines = shape that prevent sinking

9. Can reproduce asexually or sexually • When diatoms die, their glassy cell walls remain and accumulate on the sea floor • Layer of these deposits are called diatomaceous earth (excellent filtering material) • Almost all animals in the sea ultimately depend on diatoms for food

11. Problems from Diatoms • Algal blooms- sudden increase in diatom populations • Brown tide- water becomes so clouded with algae that the waters turn brown

12. Dinoflagellates • Another group of protists often found near the surface • Classified in phylum Pyrrophyta “red (or fire) algae” • Have two flagella that help move the dinoflagellate along (diatoms cannot propel themselves at all) • Contain chloroplasts and can make their own food • Have cell walls made of cellulose like plants

14. Effects of dinoflagellates • Bioluminescence- ability of an organism to produce light • Noctiluca have the ability to emit a greenish-blue light when stimulated

18. Red Tide • Water suddenly turns a reddish color with no warning • Occurs because of a sudden explosion of the Gymnodinium dinoflagellate population • Toxins released by the organisms accumulate in shellfish that eat the algae • In turn, the organisms that feed on the shellfish (fish, marine birds, humans) are poisoned • Algal bloom also reduces oxygen levels in the water which contributes to a fish kill