The Oxygen CycleThe Oxygen Cycle

oxygen

Plant release oxygen into the atmosphere as a by-product of h t th i

STEP ONE OF OXYGEN CYCLE

photosynthesis.

STEP ONE OF OXYGEN CYCLE

Animals take in oxygen through the process of respiration.

STEP TWO OF OXYGEN

Animals take in oxygen through the process of respiration.Animals then break down sugars and food.

STEP TWO OF OXYGEN CYCLE

St Th O C lStep Three in Oxygen Cycle

• Carbon dioxide is released by animals and used in plants in photosynthesis. p p y

Soil and rockSoil and rock

T dTodayThe Earth’s atmosphere The Earth s atmosphere

consists of:• 21% Oxygen

h h l h hThe Earth’s lithosphere consists of:

• 99.5% Oxygen99 % yg nThe Earth’s hydrosphere

consists of:• 46 60% O g• 46.60% Oxygen

The Earth’s biosphere consists of:

• 0.01% Oxygen

Biological Importance of Biological Importance of Oxygen

• Humans need it to breathe• Needed for decomposition of organic • Needed for decomposition of organic

wastel• Water can dissolve oxygen and it is

this dissolved oxygen that supports d d yg ppaquatic life.

Ecological Importance of Ecological Importance of Oxygen

• Without oxygen at the bottom of the water body, anaerobic bacteria (those that live without oxygen) produce acids. These acids not only increase acidity, but p d a d a d n n y n a a d y,also cause a massive release of phosphorus and nitrogen, two major fertilizers, from the organic sediment and into the water column.into the water column.

• These same anaerobic bacteria put toxic gases in the water including hydrogen sulfide (that rotten egg water including hydrogen sulfide (that rotten egg smell), ammonia, carbon dioxide and methane. These gases are all toxic to fish, beneficial bacteria and insects.

Ecological Importance of Oxygen Ecological Importance of Oxygen Cont.

• Lack of fish enables disease-hosting mosquitoes to thrive, as it t l f d f fi hmosquitoes are natural food for fish.

• Without oxygen at the bottom at all times, beneficial bacteria and i t t bi d d th i di t L insects cannot biodegrade the organic sediment. Large accumulations of organic sediment follow.

Take home message

• Portal pond needs lots of oxygen!