Class from the Field: Green Crab Surveys
I've been waiting for our class time to correspond with a low tide for a few weeks now! I Zoomed from a rocky beach in Salisbury Cove, and walked around the different intertidal zones (lower, middle and upper). All together, we reviewed the special adaptations that have evolved in intertidal life forms in order to survive their constantly changing environment. Shells protect clams, crabs and periwinkles from predators and churning waters, and retain moisture during the low tides; various anchoring mechanisms root creatures like mussels and barnacles to the rocks to resist the constant motion of their environment.
We then switched our focus to the invasive European green crab, and took a look at the havoc they are wreaking on Maine's coast. These little crabs tend to dominate native ecosystems, because they reproduce at high rates and eat up many vulnerable organisms in the intertidal zone, including eelgrass and soft shell clams. In response to this problem, there have been many ecological initiatives to track green crab populations, and even attempts to reduce them.
For any interested volunteers - there are currently open citizen science projects that offer training to identify green crabs and conduct methodical counts! I demonstrated one method for sampling green crab populations, using a randomly placed quadrat, or measured frame that defines a small area of study. By counting the number of green crabs in small defined areas, chosen randomly across a beach, scientists can draw conclusions about the green crab population on the beach as a whole. We also learned about the importance of collecting data in a random, objective way, without the opportunity for individual biases to influence the results.
A blown-up screen capture from our Zoom class of me teaching in the field. I am holding up a PVC quadrat!
Get Involved!
After today's class, we are all nearly equipped to go out and do green crab surveys as solo citizen scientists! Here is the online project that still collects green crab counts, hosted on a crowd-sourced data website called Anecdata.org:
https://www.anecdata.org/projects/view/34.
You can become a contributing member to this project, as well as review other people's data. Let me know if you'd like support in getting involved, and I will link you with further training!
Challenge for Further Learning:
Want to practice ecological sampling? This activity will give you a picture of the diversity of plant species growing in your yard. We will return to this method in future classes!
1. Watch this video on using quadrats to sample your lawn: https://www.youtube.com/watch?v=KuG-UjpQzm0
2. Make a quadrat by stretching a coat hanger into a square shape, and sample ten spots on your lawn. Write down the different species you see, noting which ones occupy the most space in the quadrat.
3. Add up your data from your ten samples. What is the most common plant in your yard?
Until next time!
Maddy
