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2010 Science Project                2011 Science Project
Kids do Ecology, 2011

This year, Christine Lindblad's 5th grade class at Peabody Charter School carried out a beach hopper experiment with help from Drs. Jarrett Byrnes and Carol Adair of NCEAS.

Jarrett and I first introduced the class to beach ecology, food webs and beach hoppers. Beach hoppers are decomposers that voraciously eat kelp. They breathe through gills and therefore have to stay wet to survive. They are also a main food


Beach hopper on kelp

Kelp washed up after a storm
           
source for birds. Perhaps for both of these reasons (to avoid preditors and stay moist) beach hoppers avoid sunlight by staying in burrows or under piles of kelp until dusk (watch a short video about kelp and beach hoppers by local beach hopper expert Dr. Jenny Dugan). After learning about beach hoppers, the students came up with a hypothesis to test:

Because beach hoppers feed at night (or dusk) and avoid sunlight to stay moist and hide from preditors, they expected that beach hoppers would eat more in the dark than in the light.



A dark beach - hoppers should eat more here

A lit beach - hoppers should eat less here

To test this hypothesis, we collected beach hoppers and made containers to keep them in overnight. The tupperware containers were filled with sand and roughly 30-40 beach hoppers. We also collected fresh kelp that the students dried (in a salad spinner), weighed, and traced on paper before adding it to the beach hopper containers. We made 6 beach hopper containers. Three were kept overnight in the dark, and three were kept overnight under bright lights.


Removing kelp from the hopper containers



Kelp tracings before and after
The next morning the students (carefully!) removed the kelp from the beach hopper containers, washed, dried, and weighed it, and then traced it on a peice of paper. Both tracings (from before and after) were cut out and weighed to provide a standardized measure of kelp weight loss.

The students found that, on average kelp lost more weight overnight in the dark. However, some of the kelp had gained weight overnight, even though it had clearly been eaten. After weighing the paper tracings of the kelp, the students confirmed that the kelp lost more weight in the dark than in the light.

The students thought that maybe the weighing the kelp provided a less accurate measurement of how much kelp was eaten than weighing the paper, since the kelp might have had more water or sand on it after removing it from the beach hopper containers than before placing it in the containers. They decided that the paper tracings probably provided a better measure of how much kelp the beach hoppers ate.

The students also counted beach hopper burrows (holes in the sand) as a measure of beach hopper activity, and found that beach hoppers were more active (made more burrows) in the dark than the light.


Kelp after removing it from the hopper containers

The students concluded that beach hoppers were more active and ate more kelp in the dark than in the light.
They presented their results to other scientists and scientists-in-training at NCEAS on March 15.
Weighing kelp

Looking for burrowing hoppers


Materials:
  • Beach hoppers (collected by scooping sand from below kelp piles into fine mesh bags and then washing out the sand with seawater in a bucket)
  • Fresh kelp
  • Sand
  • 6 tupperware containers (3 in light; 3 in dark)
  • 5 gallon buckets for collecting and transfering beach hoppers into tupperware containers (the sides are too high for them to jump out of)
  • Paper, pencils & scissors for kelp tracings
  • Scales for weighing kelp and paper tracings
  • Bright lights for overnight










Banner photo: Mt. Massive in Colorado, 2009