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