1. Aquatic Ecology Course Zoo 374

2. النظام البيئى Aquatic ecosystem
An aquatic ecosystem is an ecosystem located in a body of water. Communities of organisms that are dependent on each other and on their environment live in aquatic ecosystems. The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems.

3. Marine ecosystem
Marine ecosystems cover approximately 71% of the Earth's surface and contain approximately 97% of the planet's water. They generate 32% of the world's net primary production الأنتاجية الأولية. They are distinguished from freshwater ecosystems by the presence of dissolved compounds, especially salts, in the water. Approximately 85% of the dissolved materials in seawater are sodium and chlorine. Seawater has an average salinity of 35 (ppt).

4. Marine ecosystem (cont.)
Fish caught in marine ecosystems are the biggest source of commercial foods obtained from wild populations.
Environmental problems concerning marine ecosystems include unsustainable exploitation of marine resources (for example overfishing of certain species), marine pollution, climate change, and building on coastal areas.

5. Freshwater ecosystem
Freshwater ecosystems cover 0.8% of the earth's surface. They generate nearly 3% of its net primary production. Freshwater ecosystems contain 41% of the world's known fish sp.
There are 3 types of freshwater ecosystems:
Lentic: slow-moving water, including pools, ponds and lakes.
Lotic: rapidly-moving water: streams & rivers.
Wetlands: areas where the soil is saturated or inundated for at least part of the time.

6. Biological aspects of sea
The resources of the sea are:
Living Non-Living
(Biological) (Physical)
الحية (البيولوجية) الغير حية (الفيزيائية)

7. Biological (Living) resources
Are living animals and plants collected for human use
It is the main reserve of protein
food either from fisheries
or aquaculture.

8. Non-living resources Physical resources
Result from the deposition, precipitation, or accumulation of useful substances in the ocean or seabed.

9. 1) Oil and gases About 1/3 rd of the world oil and gas is pumped out of the ocean floor. 2) Minerals: salts. 3) Desalination as source of freshwater Only 0.017% of Earth’s water is fresh and about 0.6% is available as ground water. 4) Marine Energy Result from the extraction of energy directly from the heat or motion of ocean floor.