Unicellular Marine Organisms

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

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

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

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

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

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

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

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

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

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