Human ImpactUnit 3

Algae

Algae basics

• the base of the food chain (largest producer)

•produces 70-75% of O2 for the earth’s atmosphere and earth’s water

•can be unicellular (1 cell) or multicellular

Normal algae cycle

reproduce + create O2

nutrients released by bacteria, reabsorbed by algae, cleans water, causes succession

% die in winter, aerobic bacteria break down the dead material, use up O2

algae grow, photosynthesize to create O2

Plenty of O2 for aquatic life, and releases into air

lakes/ponds are transformed

A healthy pond begins to have aquatic vegetation; other inhabitants die, increasing organic matter, and it becomes shallower.

possibly a marsh

Algae cycle + human impact = eutrophication

eutrophication – too much algae, sometimes called “bloom”

How humans add nutrients:1. wastewater, septic2. farming waste3. fertilizer (golf courses, residential)4. car washes, soap5. composting (leaves, grass) → good thing

Algae reproduce + create O2

nutrients released by bacteria, reabsorbed by algae, toxic stuff added, succession

% die in winter, aerobic bacteria use up all of O2

Too much algae grows, photosynthesize to create O2

No O2 left for fish and toxic gases

Algae cycle + human impact = eutrophication

Toxic anaerobic bacteria take over, create CH4 and H2S

Nutrients added by human activities

Tons of dead algae

• new• bigger, deeper• low nutrients• low biodiversity• cold, clear• EX: great lakes

• old• shallow• warmer, cloudier• green algae• high nutrients• high biodiversity• EX: farm pond

Classifying water sources

Eutrophication

Eutrophication

Eutrophication

Eutrophication

Eutrophication

Different Types of Algae

• green algaegreen algae– contains chlorophyll a, b (green color) which

captures light to create energy

• brown algae– do photosynthesis, but use chlorophyll c

(brown)– diatoms (unicellular) are similar

• Diatoms– unicellular organisms with yellow-brown

chloroplast that enables them to photosynthesize.

• red algae– found in the oceans– use chlorophyll a, but have red pigment– sushi wraps, thickening agents (ice cream)