are regulated may be occurring naturally (iron, manganese, etc.) it is often the concentra-
tion of the substance that determines what is a natural component of water and what is a
contaminant.
In addition to toxic substances and disease-causing ones, alteration of water’s physical chem-
istry, including acidity, electrical conductivity, and temperature, can also have an effect.
Effects of Water Pollution on Living Things
Water pollutants can have an effect on both the ecology of aquatic ecosystems as well as on
human health. Let’s examine several types of pollution problems and how they affect both
the ecology and human health.
Polution Problem: Eutrophication
Definition: An increase in chemical nutrients, specifically compounds containing nitrogen
or phosphorus, in an ecosystem.
Causes:Frequently a result of nutrient pollution such as the release of sewage effluent and
run-off from lawn fertilizers into natural waters, such as rivers or coastal waters.
Effect on Ecology: Excessive growth of aquatic vegetation or phytoplankton (or algal
bloomand decay, and a lack of oxygen, the latter causing severe reductions in water quality,
fish, and shellfish.
Effect on Human Health and Well-Being:
- Decreasestheresourcevalueofrivers, lakes, andestuariestoadverselyaffectrecreation,
fishing, hunting, and aesthetic enjoyment. - Ifnitrogenisleachedintogroundwater, drinkingwatercanbeaffectedbecausenitrogen
concentrations are not filtered out. - Biotoxins created during algal blooms are taken up by shellfish, such as mussels or
oysters; if humans eat these shellfish, then shellfish poisoning can occur and you can
become extremely sick, including paralysis and other neurological conditions.
Polution Problem: Ocean Acidification
Definition: A process whereby the oceans’ uptake of anthropogenic carbon dioxide from
the atmosphere causes an ongoing decrease in pH of the oceans (see “Points to Consider,”
Lesson 25.1: Air Pollution, showing a possible link of air pollutants to water pollution).
Causes:Human actions such as land-use changes and the combustion of fossil fuels can lead
to an increase in carbon dioxide into the atmosphere, some of which is then absorbed by the
oceans