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Assessing Aquatic Ecosystems

Assessing Aquatic Ecosystems. Aquatic Ecosystem Assessment. The health of an aquatic ecosystem can be determined by examining a variety of factors, including: Water quality (physical & chemical parameters) Aquatic macroinvertebrates Habitat.

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Assessing Aquatic Ecosystems

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  1. Assessing Aquatic Ecosystems

  2. Aquatic Ecosystem Assessment • The health of an aquatic ecosystem can be determined by examining a variety of factors, including: • Water quality (physical & chemical parameters) • Aquatic macroinvertebrates • Habitat

  3. USGS: Water Science for Schools - http://ga.water.usgs.gov/edu/waterquality.html Sources of Contamination

  4. Water Quality • Physical • Flow, turbidity, temperature • Chemical • Dissolved oxygen (D.O.) • pH • Alkalinity • Conductivity • Phosphorous • Nitrates • Chlorine and chloride

  5. Stream flow • Volume of water moving across a specific point over a period of time (ft3/sec) • Related to amount of water moving off the watershed into stream

  6. Stream flow • Affected by: • Weather • Seasons (usually lowest in Aug. & Sept.) • Water withdrawal • Stream flow affects: • Ability to dilute pollution • Kinds of organisms living in stream

  7. Measuring Stream Flow

  8. Measuring Stream Flow

  9. Turbidity • Measure of water clarity • Based on suspended material in water (soil, plankton, microbes, etc.)

  10. Turbidity • Affected by: • Weather • Stream flow & velocity • Erosion • Run-off & discharge • Excessive algal growth

  11. Turbidity • Turbidity has an effect on: • Water color & light penetration • Temperature & dissolved oxygen • Survival of fish & invertebrates

  12. Measuring Turbidity • Measured using Secchi disk or transparency tube

  13. Temperature • Optimal temp. range depends on species • Temp. of lower order streams is usually < 20°C • Affected by: • Weather & seasons • Riparian vegetation • Water sources & discharges

  14. Temperature • Temp. affects: • Rate of biological & chemical reactions • Dissolved oxygen levels • Sensitivity of aquatic life

  15. Dissolved Oxygen (DO) • Affected by: • Temperature • Stream flow • Turbidity • Photosynthesis & Respiration • Decomposition • Input of organic material

  16. Dissolved Oxygen (DO) • Most aquatic life requires DO levels of 5 - 6 ppm to thrive • Levels < 3 ppm are stressful

  17. Biological Oxygen Demand (BOD) • Measure of: • oxygen consumed by microbes for decomposition • oxygen required for oxidation of inorganic matter • High BOD  rapid oxygen depletion  death of organisms • Levels of 1-2 ppm are very good • Sources: organic matter, effluent, and runoff

  18. pH • Measure of the alkalinity or acidity of the water • Tolerance varies based on species • Optimal range for most aquatic life is a pH of 6.5 – 8.0

  19. pH • Affected by: • Stream geology • Alkalinity • Acid precipitation • Wastewater discharges • Mining of coal or metals

  20. pH • pH has an effect on: • Biological and chemical processes • Solubility of elements & compounds • Survival of aquatic life

  21. Alkalinity • Measure of the buffering capacity • Helps maintain pH of stream • Highly dependent on stream geology • Produced by leaching of carbonate/bicarbonate from rocks • Levels between 100 – 200 ppm will stabilize pH

  22. Conductivity • General measure of water quality • Related to ion concentration • Affected by: • Geology of stream • Discharges to stream (ex: sewage) • U.S. streams range from 50–1500 µs/cm • 150–500 µs/cm good range for most fish & macroinvertebrates

  23. Phosphorous • Essential nutrient for plants, algae, and animals • Phosphorous is usually found as part of phosphate (PO4) • Aquatic ecosystems have both inorganic and organic PO4 • Plants require inorganic PO4; animals can use both

  24. The Phosphorous Cycle Tri-C Eastern Campus BIO 2806 - Environmental Science for Educators: Promoting Watershed Stewardship July 2007

  25. Phosphorous • Usually in short supply in aquatic ecosystems • Unpolluted waters < 0.03 mg/L • Critical level is 0.1 mg/L • Sources of phosphorous: • Soils and rocks • Decomposition • Wastewater • Run-off (fertilizers and waste)

  26. Eutrophication • Increased phosphorous can lead to overgrowth of algae & aquatic plants… …which leads to a chain of events that ends in oxygen depletion.

  27. Nitrates • A form of nitrogen found in aquatic ecosystems in the following forms: ammonia (NH3), nitrates (NO3), nitrites (NO2) • Nitrates are an essential nutrient for plants and algae • Natural levels in water < 1 mg/L

  28. The Nitrogen Cycle Tri-C Eastern Campus BIO 2806 - Environmental Science for Educators: Promoting Watershed Stewardship July 2008

  29. High levels along w/ phosphorous can lead to eutrophication Sources of nitrates: Decomposition & wastes Wastewater Run-off (waste & fertilizers) Nitrates

  30. Chlorine & Chloride • Low levels of chloride may be found naturally (<16 mg/L is normal) • Sources of chloride: • Soil & rocks • Decomposition & wastes • Street salt, wastewater, industry • Chlorine should not be present • Indicates input from municipal water source

  31. Other Water Quality Concerns • Metals (copper, iron, mercury, etc.) • Pesticides • Organics (PCBs, PAHs, etc.) • Fecal coliform bacteria

  32. Macroinvertebrates as Indicators of Watershed Health • Why macroinvertebrates? • Live in water most/all of their lives • Important part of an aquatic ecosystem • Provide water quality info. over time • Easy to collect and identify • Have varying levels of tolerance to pollution • “Canaries of the stream”

  33. Levels of Tolerance • Level 1 - Pollution Sensitive (“Indicator Species”) • Level 2 - Moderately Tolerant • Level 3 - Pollution Tolerant • EPA – Invertebrates as Indicators

  34. Identifying Aquatic Macroinvertebrates • Key to Macroinvert. Life in the River • Key to the Orders of Benthic Insects • Aquatic Macroinvertebrate Key • EEK! – Water Critter Key Tri-C Eastern Campus BIO 2806 - Environmental Science for Educators: Promoting Watershed Stewardship July 2008

  35. Assessing Water Quality using Aquatic Macroinvertebrates • Simplified Stream Biota Test (SSBT) • Simplest method for assessing health • Looks for sensitive benthos (stoneflies, mayflies, & caddisflies) Tri-C Eastern Campus BIO 2806 - Environmental Science for Educators: Promoting Watershed Stewardship July 2008

  36. Assessing Water Quality using Aquatic Macroinvertebrates • Index of Biotic Integrity (IBI) • More involved, but more precise • Requires more organisms (~100) • Based on species richness, species dominance, and indicator species Tri-C Eastern Campus BIO 2806 - Environmental Science for Educators: Promoting Watershed Stewardship July 2008

  37. Alternative Macroinvertebrate Activities • Leaf Pack Network • Diversity: A Stream Study Environmental Impact Simulation • Is There Mine Drainage Impacting This Stream? Tri-C Eastern Campus BIO 2806 - Environmental Science for Educators: Promoting Watershed Stewardship July 2008

  38. Habitat Assessment • Should be performed along with biological sampling • Habitat diversity is linked to biological diversity • Can provide clues about macroinvertebrates • Both instream and riparian habitat should be examined

  39. Habitat Assessment • Virginia Save Our Streams Habitat Assessment • EPA Habitat Assessment

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