Freshwater Biome, Estuaries,

Nitrogen Cycle

Aquatic Biomes• Freshwater• Marine• Estuaries

Freshwater Biomes• Rivers, streams, lakes• Organisms: fish, frogs, algae• Often surrounded by a variety of

plants.

Estuaries• Area where fresh and salt water mix (where

rivers enter ocean)• Examples: lagoons, mangrove swamps• Many species of plants, fish, crabs, shrimp,

and birds live here.• “Nurseries of the Sea” – many species

reproduce or raise young in estuaries.

Nitrogen Cycle1. Nitrogen is removed from the atmosphere

through nitrogen fixation (bacteria convert nitrogen gas to nitrates)

2. Plants use nitrates to make proteins.3. Animals get

nitrogen by eating plants (or animals that ate plants)

nitrogen inatmosphere

animals

denitrifyingbacteria

nitrifyingbacteria

nitrifyingbacteria

ammonium

ammonification

decomposers

plant

nitrogen-fixingbacteria in soil

nitrogen-fixingbacteria in

roots

nitrates

nitrites

Nitrogen Cycle (cont.)4. Animal waste and dead plant/animal

matter are decomposed by bacteria, nitrogen is returned to the soil.

5. Bacteria return nitrogen to atmosphere through the process of denitrification.

nitrogen inatmosphere

animals

denitrifyingbacteria

nitrifyingbacteria

nitrifyingbacteria

ammonium

ammonification

decomposers

plant

nitrogen-fixingbacteria in soil

nitrogen-fixingbacteria in

roots

nitrates

nitrites

Nitrogen Cycle

Nitrogen Fixation:Nitrogen is taken from the atmosphere and fixed as nitrates by bacteria

Nitrates are absorbed by plants from the soil and used to build proteins

Plants are eaten by consumers and nitrogen is taken up

Nitrogen is excreted by animals in the form of urine or feces

Nitrogen from dead plants and animals is broken down by bacteria returning nitrogen to the soil

Denitrification: Nitrogen is returned to the atmosphere by bacteria

Eutrophication • Increase of phosphorus and nitrogen concentrations in bodies of water, usually from run off

• Causes algal blooms • Leads to lack of oxygen in body of water

http://www.youtube.com/watch?v=6LAT1gLMPu4