Chlorophyll a is the green pigment in plants that is used for photosynthesis. Chlorophyll a is a good indicator of the total amount of algae in a lake. Large amounts of algae in a lake can:
- decrease the clarity of the water
- alter the colour of the water (making it greener)
- form surface scums
- reduce dissolved oxygen
- alter the pH of the water
- produce unpleasant tastes and smells.