Lab 7.3

Lab 7.3 – Can you make predictions for patterns of variation for other years?

Fundamental concept: Apply interpretation of one year of data to predict patterns over multiple years
Estimated time to complete: 45 minutes
Data skills preparation: Lab 2.1 – Time series
Materials needed: None

In the previous two activities, you looked at data from one year to investigate how seasonal changes in abiotic factors such as irradiance, temperature, and nitrate concentration influence phytoplankton abundance (chlorophyll). Here, you will use the knowledge gained during these activities to predict the multi-year pattern of nitrate and phytoplankton abundance (chlorophyll) based on the irradiance and surface water temperature data in the temperate Atlantic Ocean.

You can interact with the data by

• Adjusting the date range shown by using the slider bar to zoom in and out
• Hovering over a data point to view the data values of the different variables on that day
• On Graph 3, using your cursor to draw your prediction of how nitrate would vary over the four-year period (make sure you adjust the slider to show the full date range before drawing your prediction)
• On Graph 4, using your cursor to draw your prediction of how chlorophyll would vary over the same time frame
• If needed, you can adjust your prediction (or portions of your prediction) by redrawing your new prediction over the original drawing; the original drawing will automatically convert to your new drawing
• Once you’re happy with your prediction, click the “check prediction” box

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Interpretation questions

Answer these questions after drawing, then checking, your predictions in Graphs 3 & 4.

Take a screenshot of your predictions for nitrate and chlorophyll (to include in your lab assignment if requested by your instructor).

1. Because of the lack of nitrate data for much of the time period examined here, you were unable to check your nitrate prediction. As frustrating as this might be, scientists do not always have access to all necessary data. However, by carefully examining the available data and applying scientific knowledge, reasonable predictions can still be made. Explain your thinking behind your prediction of nitrate concentration over the four years. When did you predict nitrate to be high, low, intermediate, increasing, decreasing, etc… ? Why did you predict nitrate concentration to vary in this manner? Use your prior knowledge of the relationships between irradiance, temperature, nitrate, and chlorophyll concentration from Activity 7.2 to explain and justify your prediction.
2. Consider your prediction for chlorophyll and compare it to the actual chlorophyll values. For either 2017 or 2018 (choose one), how well did your prediction match the actual values? Note any similarities and differences with respect to magnitude of chlorophyll values throughout the year, timing of spring and fall blooms, and anything else you notice.
3. Discuss some possible explanations for any discrepancies between the predicted and actual chlorophyll patterns. In your explanation, consider other factors that might influence the amount of chlorophyll and timing of blooms, and might cause them to vary from year to year.

Application questions

Earlier, you took a detailed look at how and why chlorophyll varies over the course of a single year (Activities 7.1 & 7.2). In Activity 7.3, you now have four years of data available for most variables. Despite slight variations in magnitude and timing of peaks from year to year, the seasonal changes in chlorophyll are in general agreement with what is expected to occur in temperate oceans.

4. Use the complete data set spanning all four years to explain how the combination of irradiance, temperature, and nitrate results in the seasonal patterns of chlorophyll concentrations:
   1. In all four years, chlorophyll concentrations were lowest during the summer. Explain why that is the case, using evidence from the four-year irradiance, temperature, and nitrate graphs, and concepts from Activity 7.2.
   2. Chlorophyll concentrations also were generally low during the winter of all four years. Explain why that is the case, again using evidence from the four-year irradiance, temperature, and nitrate graphs, and concepts from Activity 7.2.
   3. In all four years, chlorophyll concentrations peaked during the spring and again in the fall. Explain what happens during those seasons to result in increased chlorophyll concentrations. Support your explanation with evidence from the four-year irradiance, temperature, and nitrate graphs, and concepts from Activity 7.2.

Reflection questions

5. Over the next few decades, surface water temperature is predicted to increase. Discuss the changes in magnitude of chlorophyll concentrations and timing of blooms that are expected to occur due to this warming, and explain why you expect those changes to occur.
6. How might these shifts in magnitude and timing of phytoplankton blooms affect the migration patterns of North Atlantic right whales? Explain your reasoning.