The kids play by it, the dogs jump in it, the salmon swim with it and you occasionally go to dip your finger in and see how cold it is – it’s your friendly neighborhood stream! Have you visited it lately? Do you wonder how it’s doing? Is it well and healthy? You need answers! WE need answers! But who should we ask? Whose wisdom should we seek?
Let’s investigate! To the literature!
You see, it’s really tough being a stream in this day and age! Human activity is constantly introducing pollutants and contaminated run-offs. Ranging from biological waste and sewage to petroleum products and fertilizers, the fresh water systems near us can become a chemical cocktail due to our activities. The storm drains that you see around the city often lead to a nearby stream and they can carry chemicals of all sorts (including engine-oil or cleaning products from when we wash something outside). Rain water run-offs can wash out fertilizers from nearby lawns and gardens and bring chemical contaminants into the stream. So, one thing is for sure: our local streams have likely seen some rough days.
These intrusions often lead to changes in the composition and content of the water that make it toxic for the organisms that inhabit these systems to survive. Some species radically reduce in numbers or even disappear completely, if the water pollution reaches critical thresholds. Different organisms can have different sensitivities to these contaminants and it is often the smallest organisms that are affected first and hit the hardest by water contaminants.
So, we have our first hint! if we wisdom about your stream’s water quality you seek, it’s small freshwater creatures you need.
How do we find them, you ask? With kick-nets – a small net attached to a stick. First, we go to a local stream that is relatively undisturbed by human activity to see whether we can find these small creatures. Having the kick-net in the water, we kick water from the stream into the net to catch some of these creatures.
Well, I did this and….surprise! we caught some of these small guys! Looking at them under the magnifier, we’d see that they are invertebrates! Small invertebrates such as stoneflies! You can identify stoneflies by their two-tales and they are only a few mm long so look carefully at what you catch in the net.
Our next step would be to do this in potentially contaminated stream and see whether we can still find freshwater invertebrates there – get a kick-net and try it out! Based on work by other scientists, freshwater invertebrates are very sensitive to pollutants and should be one of the first species to be affected by traces of contamination.
So, the rest of this scientific investigation can be up to you! But for a start, at least we know: who is wise enough to tell you how polluted your stream is? The freshwater invertebrates, of course! They can tell you how your stream is doing – such wisdom!