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Using Invertebrates as Environmental Indicators Devils River West Texas What is a watershed? • A watershed is a geographic area in which water, sediments and dissolved materials drain into a common outlet. • Watersheds are affected by all of the activities that take place within its boundaries. San Antonio River Watershed Pollution • Pollution is the introduction of a contaminant into the environment • Can you name some types of water pollutants? • Fertilizers, bacteria, silt, chemicals • What about sources of pollution? • Sources can include wastewater treatment plants, parking lots, construction sites, factories, agricultural areas, urban areas. Types of Pollution • Point Source Pollution--Point source refers to a specific discharge location such as a wastewater treatment plant or discharge from a factory Types of Pollution Non-Point Source Pollution--Non-point source pollution is a pollutant that does not have a single point of origin, for example the parking lot from the school How do we know if a stream is polluted? We could conduct a test! Biological Testing • Scientist use macroinvertebrates as one tool to assess the overall health of a stream • Macroinvertebrates-- Small animals without backbones that live in the stream • These insects are usually the larval or nymph stage of terrestrial insects such as mayflies and dragonflies. Benthic(bottom) insects are used for biological testing Why - Abundant - Small - Sensitive to the Environment - Short generation times - Easy to collect - Not very mobile ? Biological Testing Use Benthic Macroinvertebrates as indicators Advantages: Inexpensive, gives information about past & present water quality Disadvantages: Time, identification can be difficult Macroinvertebrates Aquatic macroinvertebrates feed in many different ways, some are predators, while others are filter feeders or plant consumers https://www.youtube.com/watch?v =RD5wsoycsqI Stream Habitats • Pools—areas of slow moving water generally containing lower concentrations of dissolved oxygen • Riffles—areas of faster moving water with generally higher concentrations of dissolved oxygen Pools Riffles Procedure 1) Collect a sample from a body of water: a) D-nets b) around riffles (where water flows around rocks) c) under rocks and plant debris( pool areas) 100 organisms would be a good sample size to represent community diversity A D-Net Being Used For Collection Types of Pollution Sensitivity • Sensitive or intolerant---These types of Macroinverts are very intolerant of poor water conditions. • Somewhat sensitive or intermediate—can live in moderately degraded conditions • Tolerant—can live in most conditions in a stream unless severely polluted Very Sensitive • • • • • • Mayflies Stoneflies Dobsonflies Caddisflies Riffle Beetles Water Pennies Somewhat Sensitive • • • • • Crayfish Damselflies Dragonflies Diving Beetles Water Scavenger Beetle • Right-handed snail • • • • Tolerant Black Flies Midge Larvae Mosquitoes Left-handed/ pouch Snails Why are some sensitive? • Insects breathe in different ways- some breathe through their skin, some with gills, and some use the air from the surface. • Which do you think are most tolerant of pollution? The beetle, can move long distances and breathes surface O2 Practice Your Identification Skills! Open the following link and practice identifying some of the common benthic macroinvertebrates: - Identifying Benthic Macroinvertebrates Activity