Wednesday, July 27, 2011

Tide Pool

Kathy Geoghegan-Barek


  1. To continue to sharpen observation skills
  2. Collect Data to support the our hypothesis that a greater diversity of life can be found in the tide pool on Lovells Island compared to the docks at the Barking Crab.

Specimen Collection

Date = 7/24/11, Time = approximately 12:00 pm – 1:30 pm

Tide = Coming in. Low tide was approximately 11:30 am, therefore close to low tide

Weather = Warm, briefly had rain earlier that morning and the morning of the day before. Prior to that weather had been hot and dry for several days.

Collection Location = The first tide pool if you head left from the boat dock on Lovells Island

Habitat = Sea Water,

Obsevations and Specimen Description

When we first arrived at the tide pool, I knew the tide would be coming in so I headed out to where the water was knee deep, for me that’s approximately 1.5 ft. deep. I noticed this area was a lot less rocky than at the shoreline. However there seemed to be less life in this area.

As I headed in closer to the shoreline, I found several different kinds of shell that contained hermit crabs. Although I wasn’t able to get a look at any of the hermit crabs completely out of the shell, I was able to see enough of them to realize there were different types. They also seem to come in different sizes and therefore occupied different size shells.

At one point I had a hermit crab and a periwinkle in a container together and it appeared that the hermit crab was trying to pull the periwinkle out of his shell. Why? Did he want the shell? I don’t think so, the shell he had was already bigger than the one the periwinkle had. If the hermit crab’s had been smaller I could understand him wanting to take the bigger shell if he was growing. Was he going to eat the periwinkle. That was a possibility. I had read that hermit crabs in the wild are omnivores. But then Bruce had suggested that perhaps the hermit crab was just stuck to the periwinkle due to the sticky substance the periwinkle produces. That seemed reasonable. If he were stuck and was fighting to get free this might look like an aggressive behavior.

I found several other organisms as well. But did I find enough different other organisms to support our hypothesis that there would be more diversity in the tide pool than at the docks? I haven’t finished analyzing the data yet to answer that question but my initial impression is no. There were a lot of different organisms at the docks.

On the way back to the boat we encountered grove snails. These snails had a thinner shell than the sea snails, 4 antenna and had shells that displayed a in a variety of colors and patterns. The snails themselves came in a light and dark variety and they lack an operculum.

The chapter on snails posted on blackbord states that “Land snails represent multiple invasions of land from marine snail ancestors.” Therefore these land snails, I’m calling Brown lipped grove snails, must have evolved from the sea snail. They are an invasive species from Europe (

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