Monday, August 3, 2009

Lovells Island

Hey Everyone!
Today was a very interesting day out on Lovells Island. The weather was slightly overcast and the areas where we observed today had a lot less human traffic than the area around the Barking Crab from yesterday. We started out with a boat ride over to the Island during which Bruce explained how new species are introduced to the ecosystem. He explained that the new species must adapt, otherwise over time they will become extinct due to natural selection. We learned that that only thing that differentiates exotic species from invasive species is our opinion about the species and how it interacts with the native ecosystem. Once we arrived at Lovells Island, we were given a quick overview of the island by park ranger Chris. He attempted to show us that the island looks like the shape of a ram, but it requires some imagination to actually see it. First stop on the island was the cobble beach, a beach which has both rock and sand. We learned about the “Brazil Nut Phenomenon” as an explanation of why when you have a group of solids, the larger object would be on top (i.e. rocks and a sandy beach).
Next we proceeded to collect some shells mainly blue mussels, common periwinkles (Littorina Littorea), and shells that I have identified to be cockles. We went into some discussion over what the periwinkles predators are and I have come to the conclusion that other than starfish the green crab is a predator of the periwinkle which causes the wholes in the periwinkles shell ( Next after Bruce bet us we couldn’t find a snail shell other than a periwinkle I found one (but apparently the time frame of the bet had expired… sure sure). I think it may be an Oval Marsh Snail based on my research, but I will attach the picture I took so you can check it out yourselves (sorry my picture is poor quality, I took it with my phone). The Atlantic Seashore Guide describes Oval Marsh Snails as “columella (central column) distinctly toothed. To ¼ in.”.

Next, during out lunch break Bruce showed us some terrestrial snails. I belive these snails are a mixture of white-lipped snail (Cepaea hortensis) and the grove snail (C. nemoralis), which are very similar snail species ( I believe these terrestrial snail shells can be seen on the beach due to either a predatory bird that may have eaten the snail and dropped the shell on the beach, or small children and college science Professors playing with them and moving them. Later on we spotted many more in the sumac trees in the center of the island.
Next we went and looked for crabs and other sea creatures in the tide pools, though it was still somewhat high tide so our sightings were limited. Most of us found crabs underneath rocks, the one I found was smaller which leads me to believe it was a juvenile green crab (carcinus maenas) since the crabs seen today meet the description in the Atlantic Seashore Guide of color, location, size and habitat. Later in the tide pool we spotted a lobster, a sea squirt, and long-clawed hermit crab.

As for the final question regarding the differing variations of snail shells found, I believe over time the snails have adapted to different environments causing their shells to change colors to protect themselves. The snail shells with living snails inside appear to be darker than the shells alone which I believe could be due to bleaching in the sun while the living ones are hiding in shady trees.

No comments: