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? Slough Cycles ?

This activity explores the relationships between nitrate levels, salinity, and tidal cycles in Elkhorn Slough in California. Students will analyze data and graphs to understand the influence of tidal changes on nutrient and salinity levels, as well as the effects of human activity on aquatic ecosystems.

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? Slough Cycles ?

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  1. ? Slough Cycles ? Summer 2005 Lisa Adams, Rhonda Artho, Katie Lodes, Adele Quintana, Kevin Vincent and Barbara Waters

  2. Objectives • Graphing and interpreting graphs • Comparing and contrasting relationships among salinity, nitrogen levels and tidal changes • Explaining the influence of the tidal cycle on nutrient and salinity levels • Analyzing the effects of human activity on aquatic ecosystems

  3. Location of Elkhorn Slough

  4. Activity 1 24 hour analysis of nitrate vs salinity at LO3 mooring Go to: Data Visualization for the LOBO Moorings Click on L03 ISUS Data Visualization. You will see the following screen (go to next slide)

  5. Select date at least 24 hours prior to current time Start time should be 0 and 0 Data span should be 1.0

  6. Your graph will look similar to this

  7. Questions • What variable is on each axis? • What is the title of the graph? • What are the units? • Which line represents nitrogen levels? • Which line represents salinity levels? • Explain the relationship between the two. • With your group, develop a hypothesis to explain this relationship.

  8. Activity 2Four-day analysis of nitrate vs salinity at LO3 mooring • GO back to L03 ISUS Data Visualization. • Change Data Span to 4.0

  9. Questions • Is the relationship between nitrogen levels and salinity consistent over a longer period of time? • Does this graph support or refute your earlier hypothesis? • Keeping in mind the location of the LO3 mooring, what factor(s) might be contributing to the observed cycling patterns?

  10. Activity 3Tidal pattern analysis for LO3 mooring • Go to WWW Tide and Current Predictor • Locate tide data for Elkhorn Slough at Elkhorn, CA • Scroll down to Prediction Options and select the following…..

  11. Select Graphic Plot size Select 4 days Start date needs to match previous graph select

  12. Tidal Data Elkhorn Slough At Elkhorn, CA 3 July 2005 - 6 July 2005

  13. Questions • What are the axes showing? • What are the units of measurements for each axis? • For one day, at what times do the low tides occur ? • For the same day, what is the time difference between the low tides? • For one day, at what times do the high tides occur ? • For the same day, what is the time difference between the high tides? • Is the time difference between high tides and low tides the same?

  14. Questions • Do you see a relationship between the tidal graph and the four-day analysis of nitrate vs salinity at LO3 mooring? • Does your analysis support or refute your previous hypothesis?

  15. Conclusion • Briefly, summarize the relationships among nitrate levels, salinity and tidal cycles in Elkhorn Slough in California.

  16. Extensions • Graph the coordinates of the moorings in Elkhorn Slough using data given on the website • Analyze possible sources of nitrates using a land use map of the Elkhorn Slough watershed (possible links USGS…) • Analyze tidal patterns (mixed semidiurnal…) • Compare different moorings data • Evaluate seasonal changes in data • Look at the flow of the Salinas River and how it is influenced by the tides and the resulting changes in nitrate levels • Investigate the effects of excess nitrates on other aquatic ecosystems (Gulf Dead Zone, etc)

  17. Extension 1

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