pick one of the five lakes from around the world: Annie, Balaton, Kentucky, Muggelsee, and Sunapee. You can find sensor data for each of these lakes in an Excel file available on Canvas.

Environmental Science by Geoffrey

Assignment 2: Eutrophication and Metabolism1

 

Learning objectives:

  • Discuss eutrophication of aquatic ecosystems
  • Compare and contrast structural vs. functional ecosystem metrics
  • Explain the drivers of diel variation in sensor data
  • Calculate metabolism rates (GPP and R) from high-frequency data
  • Compare rates of GPP and R from lakes with different trophic status

 

Why this matters: Different lakes (and lagoons) exhibit a range of catchment sizes, morphometry, and land use that contribute to differences in ecological function. These functional differences mean that water bodies vary in ecosystem services such as habitat quality and recreational value. In this assignment, we will explore high-frequency water quality datasets from several lakes around the world, graph high-frequency data, and use simple conceptual and mathematical models to calculate estimates of metabolism (gross primary production and respiration). Finally, we will compare metabolism rates across different lakes to examine gradients of eutrophication.

 

 

Helpful reading (files are on Canvas):

  • Solomon, C. T., Bruesewitz, D. A., Richardson, D. C., Rose, K. C., Van de Bogert, M. C., et al. 2013. Ecosystem respiration: drivers of daily variability and background respiration in lakes around the globe. Limnology and Oceanography 58(3): 849-866. Use specifically for the metadata in Table 1.
  • Palmer, M. A. and Febria, C. M. 2012. The heartbeat of ecosystems. Science 336(6087): 1393-1394.
  • Odum, H. T. 1956. Primary Production in Flowing Waters. Limnology and Oceanography 1(2):102-117. Open access

Task 1: Graphing high frequency data

  1. In a group of 2-3, pick one of the five lakes from around the world: Annie, Balaton, Kentucky, Muggelsee, and Sunapee. You can find sensor data for each of these lakes in an Excel file available on Canvas.

 

  1. Do some research on your lake. Where is it located in the world? What type of lake is it (e.g., naturally-formed or manmade, geological formation)? How big is it? What is the average and maximum depth? Hint: Check out: Solomon et al. (2013) Table 1.

 

  1. Graph each of the three variables (O2, PAR, and wind speed) on three separate figures.
    1. Make your figure have all the information needed to interpret the data being presented (i.e., include axis labels, units, adjust the axes to maximize the space used by the data, etc.)

 

  1. What patterns do you observe in PAR, O2, and wind for the 4 days in your dataset?
    1. Based on your data, predict whether your lake is oligotrophic or eutrophic.

 

  1. For your O2 data, describe the shape of the curve. When does oxygen increase and decrease? Can you explain any irregularities in the O2 curve using wind data?

 

 

Task 2: Calculating metabolism (see “Task 2 Example” tab in Excel file for assistance)

  1. For your lake, examine the PAR values from your graph – use this figure and the data in the Excel spreadsheet to identify the sunrise and sunset times for all 4 days.
  2. find the initial oxygen concentration (at sunset) and the final oxygen concentration (at sunrise) for each day and night period in your record (record it in columns F and G).
  3. Calculate the change in oxygen concentration over each day and night period. Note the signs, are organisms producing or consuming oxygen during the day and night periods?

 

  1. Calculate respiration for each nighttime period.

 

  1. Calculate the rate of oxygen change per hour for each nighttime period. Be careful with units and signs. (Column J)

 

  1. Calculate the respiration rate (R) over 24 hours for each nightime period (Column K)

 

  1. Calculate the gross primary production for each daytime period. Be careful with units and time periods. They matter!

 

  1. Find the average respiration rate (R) for that daytime period using the average respiration rate from the preceding and following night (see 7b above).

 

  1. Determine how much oxygen was respired over each daytime period by scaling your answer in 8a for the number of daylight hours.

 

  1. What is the gross primary production (GPP) rate for each of the four 24-hour periods? Remember, GPP = Change in O2 – R (minus a negative!).

 

  1. Create a bar graph of your 4 days of GPP and 3 days of R data.

 

 

Task 3: Comparison of lakes of different trophic status

  1. After calculating the GPP and R rates over several days, calculate the mean (average) GPP and R rates for your lake. Please share your results with these to the rest of the class.

 

Once the class data is compiled, your group will answer the following questions:

 

  1. How do the rates in your lake compare with the other lakes in the class data set?

 

  1. Which lakes are oligotrophic and which are eutrophic? Is your lake green or blue?

 

  1. Look at Figure 4 from Solomon et al. (2013) (below). How do the rates in your lake compare with other lakes in this dataset? Which lakes have the highest metabolic rates? Which have the lowest rates? What do the lakes with high metabolism rates have in common?

 

 

 

Data used in this module were collated and quality checked by:

  • Solomon, CT, Bruesewitz, DA, Richardson, DC, et al. Ecosystem respiration: Drivers of daily variability and background respiration in lakes around the globe. Limnology and Oceanography 58(3): 849-866.