Overview
During this interactive experience, students will explore how the actions of an agricultural farmer and an oyster aquaculture farmer impact the health of eelgrass in Malpeque Bay, and therefore the survival of other species in the habitat.
Background
Habitats can be very sensitive — even a small change such as a change of temperature or the availability of nutrients can alter the habitat. These changes can occur naturally, but humans also cause changes to occur.
Coastal runoff is a major source of nutrients in the ocean. When nutrients (nitrogen and phosphorus) are used as fertilizers on agricultural farms, water runoff can cause nutrient pollution in the water. Eutrophication occurs when an excess of nutrients leads to excessive plant and algal growth.
Ulva (sea lettuce) is a green seaweed that uses photosynthesis to make food. When there are lots of nutrients in the water, ulva grow and grow, both on the bottom and floating in the water. Too much growth in the water column creates so much shade that other Ulva and other species cannot get enough sunlight. Once the ulva start to die because of shading, bacteria and other organisms begin to decompose the dead organic matter. Their activity uses up a lot of the oxygen, creating areas of hypoxia (very low oxygen) on the seafloor. The areas of low oxygen make the habitat unsuitable for fish that live near the sea bottom: they either find another habitat or they die.
Eelgrass is a seagrass that is an important habitat-forming species. Its thick, long, green blades of grass make excellent habitat for small juvenile fish to hide in. Eelgrass also photosynthesizes, so when the ulva grows too thick, the eelgrass also cannot get enough sunlight. As the eelgrass dies, the fish lose their habitat.
Oyster aquaculture also affects the eelgrass in the Bay. The oysters are cultivated on floating platforms. Platforms cause a significant amount of shading on the coastal seafloor, limiting the amount of sunlight available for the eelgrass.
Related links
Learning outcomes
Explore how changes in one variable (nutrients) impact another habitat variable (O2) and the number of species in a habitat.
Competencies
Critical thinker, Collaborator, Communicator
Focus question
What are the relationships between marine species and their habitats?
Learning objectives
Make and record observations.
Explain how the agricultural farm and the aquaculture farm in Malpeque Bay impact the number of species in the habitat.
Use the power of observation to determine the ultimate balance between nutrients, oysters and species.
Time
45 min
Before you start the workshop
Charge your devices (tablets and phones).
Connect all the devices to wifi.
We recommend adding this link as a shortcut on the screen of the devices you will be using in the workshop: https://bit.ly/2sOEt2l .
How to guide
Set up the computer/projector to display Bay Watch.
Load the video Ulva Overload in one tab. Test your sound.
In a second tab, load Bay Watch. Test to make sure it is working.
Workshop
Introduction
15 min
Welcome!
Explain to the group they are going to learn how farming can impact marine habitats, and that they will be challenged to help farmers balance their needs with keeping the marine ecosystem healthy.
Video: Ulva overload
Ask students:
What do you know about how farms affect water systems?
What do you know about how farms affect marine habitats?
Explain that they will start by watching a short video to learn a bit more about how farms can impact the Bay.
Play video.
Have a brief discussion using the questions below as a guide. You can find support in the background information above.
What did you learn about farming and marine habitats?
What species did they talk about?
What impacts can farms have on marine habitats?
Bay Watch
10 min
Explain the premise of the interactive, including the variables, and do a short demo on how to use it.
Action: Slide the nutrients up and down and change the number of oysters in the bay.
What to say: “Here is our Bay. We are going to try and figure out what the ultimate balance between nutrients, oysters and species is. In your pairs, one of you will be the farmer. The farmer controls how much nutrients goes onto the farm and how many oyster platforms are in the bay.”
Action: Set nutrients back to 0. Go to goggles in top right corner to change view to underwater.
What to say: “The other person will be the scientist underwater. Their job is to observe what is happening to the species, habitat and oxygen level and communicate their observations to the farmer.”
Pass out the devices you have prepared.
If you have two devices per pair (tablet or computer and a headset) instruct students to follow the prompts at the beginning of the experience to pair their devices.
Invite students to explore Bay Watch for 5 mins in pairs.
Call students back together.
Ask the to share their observations so far.
Challenge
10 min
Present the challenge:
“Farmers need to eat! Species need to thrive!”
“What is the ultimate balance between nutrients, oysters and species?!”
“In your pairs, decide on the best amount of nutrients and oyster platforms that still result in a healthy habitat. Be prepared to defend your rationale.”
Share and discuss
10 min
Provide each pair of students with a sticky note.
Ask students to record their names and the amount of nutrients and oyster platforms they decided on the sticky note and bring it to the board.
Group similar answers together.
Invite students to share their rationale. Use the discussion points below as a guide.
What is your rationale for the ultimate balance between nutrients, oysters and species?!
What steps did you take to figure it out?
“What factors are essential for a healthy marine habitat?” Ask students to give specific examples based on their observations.
The agricultural farmer and oyster farmer need to make a living by producing crops, cows and oysters, but the impacts are not always positive. Suggest some ways to balance the needs of the habitat and its species with the needs of the farmers.