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Chemistry
We test the following every time we go to the stream:
(1) Dissolved Oxygen: Fish and other aquatic critters require oxygen, the same as we do, it's just dissolved in water. We test the creek at 6 am, when oxygen is at its lowest, before the sun comes up and the algae and other green plants in the water start pumping oxygen back into the stream. Some fish and aquatic insects need more oxygen than others. A reading below 4 ppm is dangerously low for most fish.
(2) pH: This simple test, similar to those used in swimming pools, determines how acidic or basic the water is. A range between 6 and 9 is tolerable to most aquatic life.
(3) Temperature and Flow Rate: The warmer the water, the less oxygen it contains. During summer droughts when the river is ponded, or when trees are not present to shade the stream, low flow and high temperatures place stress on all creatures.
We submit water samples to the lab to test the following:
(1) Herbicides/Pesticides (May): indicates the presence of chemicals like atrazine and 2,4-D.
(2) Fecal Coliform (July): shows the concentration of bacteria in the water from human or other animal waste, which can be dangerous to swimmers and waders.
(3) Chemicals/Heavy Metals: (September): includes nitrates, ammonia, phosphorus, total suspended solids and metals like aluminum, magnesium, iron and lead.
Biology
Who is making a living in the river? There are many ways to study life in a creek but we use a simple method that looks at the macroinvertebrates living at the creek bottom. The term means "critters without a backbone, large enough to see with the naked eye." These critters are at the bottom of the food web, and fish, frogs and birds all ultimately depend on them.
If we find in our nets only a few species that are very tolerant of pollution (like leeches and bloodworms), we know right away the stream has a problem. If there are a wide variety of species like mayflies, stoneflies, water pennies, dragonflies and mussels- we know the water quality must be pretty good. This is especially fun for kids who learn how to use a key for identifying species.
Habitat
Is there food? Are there tree trunks, leaves, and living plants growing in shallow water to provide food, shelter and places to lay eggs? Are there trees overhanging, providing shade to keep the water from being too warm? Has so much sediment run off into the river that the bottom is coated, which smothers the life in a stream?
In the habitat survey we also look at the shape of the stream, the stability of the banks, and the presence of riffles that pump oxygen into the water. We consider the land uses next to the stream and what impacts roads, houses, farms, construction projects, and utility lines may have. The presence of a buffer of trees and other vegetation along the stream banks is a very important filter that can protect a stream from all these impacts.
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