Lab 12 – Instructor Guide

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Lab 12 – Wildfires
Instructor Guide

In this activity, students will investigate time series data related to deposition from a wildfire ash plume.

Approximate time involved: 45-50 minutes for each of the three activities

Learning outcomes

  • LO1. Describe the connection between climate change and wildfires.
  • LO2. Investigate patterns in individual data sets (relative humidity, shortwave irradiance, wind direction, air temperature) to identify the arrival date of the smoke plume. 
  • LO3. Investigate patterns in individual data sets (sea surface temperature, backscatter, CDOM) to identify the ocean response to the smoke plume. 
  • LO4. Make connections between wildfires and algal blooms (chlorophyll a, dissolved oxygen) and explore the consequences of these blooms for the ocean and society.

 

Learning outcome Activity 1 Activity 2 Activity 3
Outcome 1 Introduced Introduced Applied
Outcome 2 Introduced Guided practice Applied
Outcome 3 Introduced, guided practice

Materials needed

None

LAB 8 student Answer Sheet form

What students should know before this activity

We assume students have been introduced to the following basic concepts:

  • Describing wind direction
  • Factors affecting primary productivity
  • Identifying key components of a scientific graph (axes scales, legends, multiple y-axes)
  • Describing data patterns such as minimum and maximum values, trends over time or distance

What instructors should know before this activity

This activity allows students to observe connections in Earth’s systems and to understand how events that occur on land can impact the ocean. In this lab, students will be exposed to noisy data, and be asked to understand that in some cases, data cannot be used due to sensor error

Scientific Background

2020 Oregon Labor Day Fire:

In September 2020, a wildfire outbreak spread quickly across western Oregon causing significant damage and shrouding the region in smoke for more than a week. Smoke from these fires, driven by an easterly wind event, could be seen from satellites (see Figure 12.0.2). The smoky air was measured by the Coastal Endurance Array’s Oregon Shelf Surface Mooring (CE02SHSM) 10 nautical miles west of Newport, Oregon, which measured the lowest relative humidity values (<18%) since it was first deployed in April 2015. These winds and the associated smoke plume were followed by a week of reduced sunlight. Six meters below the surface, sunlight was reduced by the red smoke. Closer to shore at the Oregon Inshore site (CE01ISSP), light levels were measured throughout the water column by an OOI coastal surface piercing profiler. The smoky air had relatively high concentrations of carbon dioxide and other ocean nutrients capable of producing an algal bloom.

One of the concepts explored in this lab is corrupted data. The signals produced by all optical sensors show evidence of a plankton bloom immediately when the ash begins to be deposited. It is actually highly unlikely that the ash plume immediately triggered a significant increase in DO, chlorophyll a, and parameters examined. Physiologically, phytoplankton do not have the capacity to  grow and accumulate that quickly. So, why do these parameters show DO and chlorophyll increased so rapidly when the ash plume arrives?

DO, chlorophyll a, and backscatter instruments use optical sensors to make their measurements. Recall that vegetation was burning in the fire, and the plume likely contained ash and residual organic material from the plants themselves. Ash particles that were deposited in the water column can block light or coat the sensor surface, which may reduce the amount of light reaching the sensor or distort the sensor’s ability to detect it properly. In addition, certain chemical compounds in the ash might absorb or scatter light in ways that confuse the sensor. As a result, the readings likely do not indicate an immediate algal bloom on the day the ash plume arrived. Rather, is likely that the optical sensors were unable to take accurate measurements and relying on this data could cause us to draw misleading conclusions about phytoplankton productivity.

Therefore, these immediate spikes in chlorophyll a, DO, and backscatter that occur on the day the smoke plume arrives over the mooring should be disregarded, and we need to look for a more subtle response in these productivity metrics in the days and weeks to follow to properly understand the impact of wildfires on phytoplankton

 

Teaching Notes

TBD

Optional Pre-Lab Activities:

Students will benefit from completing Lab 2.1 (time series), Lab 2.5 (wind velocity), and Lab 9 (Primary Production)

Pre/post-lab Assessment Questions:
  1. TBD
Extensions:

Stimulation of phytoplankton blooms by wildfire deposition provides an opportunity to talk about the causes and impacts of harmful algal blooms. Most of the time, algal blooms simply fuel the ocean food web, which is especially important in offshore waters and the open ocean. However, sometimes algal blooms can be harmful to marine ecosystems. As very large algal blooms die-off, their decomposition by aerobic respiration removes oxygen from the water column, causing suffocation to fish and other aerobic organisms. In other blooms, the blooming species of algae is capable of producing toxins that can cause harm or death to marine organisms and humans. These types of blooms are often referred to as harmful algal blooms (HABs) or ‘red tide.

This video from Popular Science presents a compelling case study of HAB neurotoxins impacting seabirds: The True Story of Hitchcock’s The Birds

Associated Resources:

  • TBD