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Aquatic ecosystem health
Healthy aquatic ecosystems are those where human disturbances have not impaired the natural functioning (e.g., nutrient cycling) nor appreciably altered the structure (e.g., species composition) of the system. An unhealthy aquatic ecosystem is one where the natural state is out of balance.
These disturbances can be physical (e.g., injection of abnormally hot water into a stream), chemical (e.g., introduction of toxic wastes at concentrations harmful to the organisms), or biological (e.g., introduction and propagation of non-native animal or plant species). Symptoms of poor ecosystem health include the following:
- The loss of species.
- The accelerated proliferation of organisms. One example is algae blooms caused by an excess of phosphorous and nitrogen compounds in the water. This condition is called "eutrophication".
- Increased incidences of tumours or deformities in animals.
- A change in chemical properties. Perhaps one of the most significant has been a reduction of pH in water caused by acid rain.
- The presence of certain organisms that indicate unsanitary conditions. Coliform bacteria, for example, are a sign that the system may contain organisms that cause a variety of human diseases such as diarrhea, typhoid, and cholera.
- The loss of traditional Aboriginal culture associated with the ecosystem.
Many symptoms of poor ecosystem health occur simultaneously. For instance, increased lake acidity may kill certain species, thereby allowing the temporary proliferation of species more tolerant of acidity.
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