Biotic Factors of Aquatic Ecosystems Aquatic Animals Representatives

Biotic Factors of Aquatic Ecosystems

Aquatic Animals Representatives of all taxonomic levels of animals (below) can be found in aquatic ecosystems from simple organisms such as - annelids to other invertebrate animals such as molluscs (snails and clams), and - arthropods (insects and crayfish).

The vertebrates are represented by fish, amphibians, and reptiles. Birds and mammals are found in association with fresh water aquatic ecosystems but do not actually live in the water.

Some of these animals can be classified as indicator species, keystone species or invasive species. Indicator species can be collected and observed to show the health of an aquatic ecosystem. Some indicate poor water quality, others indicate good water quality.

Keystone species play a significant role in an ecosystem. Removal of such species would have an impact on the ecosystem structure and other organisms living in the ecosystem. Can you think of a keystone species?

Beaver are an example of keystone species. Why? They alter an area by flooding land create surface water bodies in the form of larger streams or ponds that play host to aquatic organisms that would not otherwise live in that location.

Invasive Species expand their range when the opportunity arises. They out-compete other species that were in a location previously. What is an example of invasive species? What is an aquatic example of invasive species?

Zebra mussels are an example of invasive species. These mussels not only out compete native mussels for food and displace them, but they attach to man-made structures and filter huge quantities of water which makes the water very clear.

Protists - These include both producers and consumers. - Producers include green algae, which are immobile but can be carried by wave action or currents.

Bacteria Blue-green algae and cyanobacteria play significant roles in the nitrogen and carbon/oxygen cycles. Some are decomposers. Others attached themselves to rocks and form a biofilm that extracts nutrients from flowing water.

Archaea are specially adapted organisms that can be found in saline lakes and anoxic conditions. Methanogens live in anoxic conditions and produce methane gas.

Aquatic Plants Aquatic plants play a huge role in the aquatic ecosystem. They produce oxygen for the aquatic animals and convert glucose to more complex carbohydrate molecules for use by bacteria, protists and animals. Macrophytes are large aquatic plants that are rooted in the sediment then grow up through or float up to the surface to facilitate exposure to the sun for PS.

Pond Dipping You can determine the Water Quality Index by observing and counting the different species of benthic macro-invertebrates. Benthic: the ecological region at the lowest level of a body of water, including the sediment surface and some sub-surface layers.

Group 1 (These organisms are generally pollution-intolerant. Their dominance generally signifies GOOD WATER QUALITY. )

Group 2 (These organisms can exist in a wide range of water quality conditions. )

Group 3 (These organisms are generally tolerant of pollution. Their dominance usually signifies POOR WATER QUALITY. )

To determine the water quality index, you must: - Multiply the number of species of group 1 organisms by 3 - Multiply the number of species of group 2 organisms by 2 - Multiply the number of species of group 3 organisms by 1 - Add all three numbers together to determine the water quality index for that sample. - Find an average for the four samples taken at the site and determine the water quality rating.

State a conclusion regarding the surface water quality or the health of the aquatic ecosystem. Consider the watershed contributing to reach of the river investigated and suggest reasons for the findings.