Aquatic Species Diversity and Water Quality

Transcription

1 Aquatic Species Diversity and Water Quality Reference: Wagner & Sanford. Environmental Science. Wiley & Sons, 2005 Introduction: Freshwater is only a small part of the Earth s supply of water, yet it is a vitally important resource. Lakes, ponds, rivers, and streams provide habitats for many types of organisms, and they provide drinking water, food, recreation, and aesthetic experiences for people. Rivers and streams carry nutrients and minerals vital to life in the oceans, and throughout history they have been important for transportation. Biodiversity is a popular term used by politicians, the media, the public, and environmentalists. What exactly does it mean? Biodiversity (or biological diversity) is defined as the different life forms (species) and life-sustaining processes that can best survive the variety of conditions found on earth. More specifically, biodiversity includes genetic diversity (variety in genetic makeup within a species), species diversity (variety among species in habitats), ecological diversity (variety of habitats such as forests, grasslands, streams, etc), and functional diversity (biological and chemical processes or functions). Human actions, such as agriculture, elimination of species, pollution, deforestation, war, and settlement, can reduce biodiversity. This reduction in diversity has both known and unforeseen consequences as ecosystems react to these disturbances. Loss of biodiversity can increase the vulnerability of an ecosystem to further perturbations by reducing stability and functionality. Each freshwater species is adapted to arrange of conditions temperature, dissolved oxygen, and ph being the most important. While some organisms have a wide tolerance, many can survive only within a narrow range of environmental conditions. Key organisms, adapted to different conditions, can be used as indicators of water quality. When organisms that require a ph range of 7 to 8 are not found, it may indicate that the water is more acidic or basic. For example, carp are able to live in water that is too warm and too turbid for many other fish species, whereas trout prefer cold, clear water. During this study you will be evaluating the species diversity of macroinvertebrates in a creek ecosystem. Macroinvertebrates are animals that do not have backbones, but are visible to the naked eye. Many of these organisms live on the stream bottom or on other substrates. Many of the macroinvertebrates we will find are insects, but many others are represented by freshwater aquatic worms, snails, clams, crustaceans, and arachnids. This lab s focus is species diversity. Natural ecosystems contain a wide variety of species, which interact to form stable and functional communities. As discussed above, the numbers and proportions of different species found in an ecosystem are referred to as species diversity. There are two components to measure this diversity: species richness and species evenness. Species richness is the number of different species. Species evenness is the relative proportion of each species. Materials Needed: Kick nets dip nets 5 gallon buckets waders and boots shallow white trays Petri dishes plastic spoons medicine droppers magnifying lens field manuals for macroinvertebrates

2 Collection Procedures: 1. Invertebrates will be caught will be caught in dip nets and in kick nets. 2. Approach the riffle (moving water) from downstream and place the kick net at the downstream edge of the area you wish to sample. The net should be perpendicular to the flow and lay firmly on the stream bottom. Tilt it back at a slight downstream angle, but not so much that water flows over the top of the net. Anchor the bottom with cobbles to prevent macroinvertebrates from escaping. Kick net sampling should be done in parts of the creek that contain riffles. 3. After the kick net is in place, pick up the large rocks inside the sample area and wash organisms from them into the kick net. After the rocks have been cleaned and discarded, churn the bottom pebbles and sand with your hands and feet several times to dislodge any additional residents. 4. Raise the kick net from the stream with a forward scooping motion and invert the net into a 5-gallon bucket containing water. Rinse the net carefully in the water to remove all of its contents. 5. Use the dip nets in and around the stream bank. Scrape the bottom of the creek and sample in around exposed roots. Invert the net into a 5-gallon bucket containing water. 6. Repeat the collecting process several times. Take new samples from undisturbed areas of the riffles. Do not walk in areas intended for collection work. Macroinvertebrate Identification Procedure: 7. Pour some of the creek water from the collection buckets to the white trays. 8. Captured animals can be easily seen as they move against the white background of the tray. Suck individual animals up into a turkey baster or medicine dropper and then transfer them into Petri dishes. 9. Transfer larger animals (fish, Crayfish, etc.) caught in the net back into the creek. 10. Identify and count the number of stream organisms captured. Use the magnifying glass (if needed) and the picture key to identify and record each of the animals present on your data sheet. Repeat this process until all of the animals captured at the stream have been identified and counted. Complete the worksheet on the next page using class data to determine the water quality of Deer creek.

3 Caddisfly Larvae Hellgrammites Mayfly Nymphs Gilled Snails (right) Riffle Beetles Stonefly Nymphs Water Penny Larvae Somewhat Tolerant Other Beetle Larvae Clams/Mussels Crane Fly Larvae Crayfish Dragonfly Nymphs Damselfly Nymphs Scuds Sowbugs Fishfly Larvae Alderfly Larvae Watersnipe Fly Tolerant Aquatic Worms Black Fly Larvae Leeches Midge Larvae Pouch Snails (left) Other Snails (flat) Macroinvertebrate Personal Count

4 Analysis & Questions 1. What factors (e.g., during collection) may have skewed the number and/or diversity of macroinvertebrates observed? 2. Were some macroinvertebrates more abundant in a particular area? Why? 3. What conclusions can you make about the diversity of this creek? 4. What conclusions can you make about the water quality of this creek? 5. What other data would you want to collect to determine the ecological and environmental health of the creek? 6. What human activities could adversely affect species diversity in this creek?

5 7. Why are mayflies, stoneflies, and caddisflies worth three points while aquatic worms, black fly larva, and leeches are worth one point in your data sheet to determine water quality? 8. Compare the Deer Creek data collected with that of Sinkin Creek (Drey Land) data collected during Biology Drey Land last spring. Describe three factors that might account for the differences? 9. Go to How does the Missouri Stream Team gather its data? What are the three goals of MO Stream Team? Describe two other activities the MO Stream Team sponsors. Why does MO Stream Team sponsor these activities?