Toxins as a measure of Ecological Function
What are toxins?
Toxins are substances that can be harmful or cause death to plants, animals
and humans, usually in an increased amount. There are naturally occurring
toxins in the environment: metals such as copper, lead, zinc mercury, cadmium
and nickel. Toxic metals are naturally in relatively low concentrations in
the Puget Sound lowland streams and lakes.
There are also human-produced toxins such as manufactured herbicides and pesticides and vehicle emissions like gasoline and oil. Other human products, such as antibiotics and artificial hormones, are proving to have toxic effects in aquatic water bodies, as well.
What increases toxins in our environment?
Agriculture, urban development sewage outfalls and internal combustion motor
boats can increase concentrations of toxins. Impervious surface and population
concentrations contributes to the rate at which toxins move into an aquatic
ecosystem.
Toxins come from the application of pesticides, herbicides and other chemicals. Others are associated with motorized vehicles (toxins from internal combustion engines, brake pads, oil leaks, and other vehicles emissions). Sewer outfalls and combined sewer overflows (CSO) also contribute toxins by transporting toxins not treated by sewage plants or collected through stormwater runoff from impervious surfaces such as roads and driveways.
How are toxins naturally prevented from entering our water?
Wetlands slow down water allowing plants to absorb many of the toxins found
in aquatic ecosystems. When wetlands are lost, that ability to remove toxins
from the system is taken away. (See information about detention ponds under
phosphorus.)
References: Stanley
et al. 2005.