Lab 12.6

Lab 12.6 – Ash Plume and Algal Bloom

Fundamental concept: Describe variations in atmospheric conditions indicative of wildfire ash plumes and identify the arrival date/time of the plume over the Endurance Array. 
Estimated time to complete: 30 minutes
Data skills Preparation: Lab 2
Materials needed: None

Productivity in the post-depositional environment:

In lab section 12.5, we discovered that the arrival and deposition of the ash plume over the Endurance Array likely created a false signal of an algal bloom. We can now shift our focus to the days following the plume’s arrival—when it delivered carbon and other micronutrients—to look for evidence of a real increase in primary productivity.

Recall that during wildfire ash plume deposition in the ocean, dissolved nitrogen concentrations can increase significantly. Among lots of other chemical compounds, wildfire ash contains various forms of nitrogen, such as nitrate (NO₃⁻), which can dissolve into seawater when ash settles on the ocean surface. This sudden influx of nutrients can act as a fertilizer, potentially stimulating phytoplankton growth.

Add Quick Check Questions here

Now use the data below to help you explore the impact of the ash deposition event on the phytoplankton community. You can interact with the data by switching among productivity variables and nitrate.

Orientation Questions:

Select Chlorophyll a as the parameter for Graph 1.

 

Interpretation Questions

Use the interactive graphs to answer the questions below.

 

Select Chlorophyll a as the parameter for Graph 1 and select post-depositional period in the blue boxes just below the graphs.

1. What is the date and time of the lowest chlorophyll reading at the start of the post-depositional period?
2. What is the date and time of the highest chlorophyll concentration in the post-depositional period?
3. Calculate the percent change in chlorophyll concentrations between the dates. Show your work.
4. Now select dissolved oxygen as the parameter for Graph 2. Describe the correlation between DO and chlorophyll. Is this the result you would expect? Explain why or why not.
5. Manipulate the other parameters presented in the graph above. What additional evidence suggests that ash deposition stimulated phytoplankton growth?

Reflection Question

1. As discussed in 12.0, the occurrence of wildfires is increasing globally. Given what you learned about the result of the Oregon and Australia fires, make two predictions about how wildfires will impact the ocean environment.