Tuesday, August 5, 2008

Lovells Island, Observations of Tide pools and Lands Snails

1. Tide pool observations:
Upon arrival at Lovells Island we were guided to a secluded tide pool ideal for investigation during low tide. The low tide had caused piles of seaweed to accumulate just out of reach of the lapping waves. I attempted to identify four of the varieties of seaweed I saw in the seaweed carpet.
Referring to the small sketches I drew on site I have attempted to identify these seaweeds as rockweed (Fucus sp.), sea lettuce (Ulva lactuca), brown kelp (Laminaria agardhii) and Irish moss (Chondrus crispus). The rockweed is brownish green, very abundant and most easily recognisable by the air bladders located throughout the "body" of the algae. Sea lettuce is a striking almost neon green and was one of the less common seaweed varieties I observed. Sea lettuce is very thin and almost translucent. The leaves are broad and felt fragile out of water. I believe I observed brown kelp which is a dark brown color, long and leafy. I observed some pinhead-sized dots scattered on the leaf. These which grew more frequent towards the bottom of the brown kelp leaf. Lastly, I believe there was abundant Irish moss along the beach and in the water. Irish moss is very leafy. The sample I looked at had three branches growing out from the base, each of these branches branched off into three or four more and on and on...much like the the capillaries of the circulatory system. 
Periwinkles were abundant in the tide pool. I think that they were either common periwinkles (Littorina littorea) or rough periwinkles (Littorina saxatilis), both of which are common on the rocky shores of the Atlantic coast. They were often in clusters on the rocks and when I picked them up and out of the water for a closer look, they would fall off and splash back into the tide pool. Perhaps they fall so easily as a defense mechanism. According to the New York Times article, periwinkles eat almost entirely algae. I noticed that there was a lot of algae on rock, they were very slippery. The periwinkle's shells were a dark brown and spiralled to a point at the top. They smallest periwinkle I observed was about half an inch long and the largest was about 2 inches long (length of the shell, not the soft body).
Other notable creatures I observed in the tide pools were Asian shore crabs which were very abundant and found under rocks. Asian shore crabs are an non-native species to the rocky shore of the Northeast but they have apparently created a thriving community. I also observed a school of small gray fish about 2 inches long darting through the tide pool, but I cant identify them because they were so fast.

2. Land snail observations
Our afternoon on Lovells Island was spent searching for and observing land snails. We collected samples of empty shells and samples of living snails. We soon found out that the snails have an affinity for Sumac trees, as almost every living snail was found on a Sumac leaf. They were often found on the bottom of the leaves which I think might be a mechanism for protection, they are less visible to predatory birds on the underside of leaves. We were told that land snails generally move in two directions: down and up. The move down during or after recent rain, and up when it is dry. Accordingly, we found most of our snails up above head level as it was a dry day with no precipitation. We also noticed that as we lost elevation and the path began to slope down that we instantly we able to find more snails. The abundance of empty snail shells also grew as we moved down the hill. 
Once we finished collecting our living samples and our empty shells we gathered as one group and discussed the different ways to categorize the shells in attempt to decipher how many species might inhabit the island. We all had different ideas of how they should be grouped and the possibilities were endless. Our class came to no consensus as to how many species inhabit the island or as to the correct method to categorize our shells. We later were informed that we had been looking at two species of land snails, the brown-lipped snail (Cepaea nemoralis) which has a brown lip at the opening of the shell, and the white-lipped snail (Cepaea hortensis) which has a white lip at the opening of the shell. 

While I was wading through the tide pools early in the day I was struck by how many more living organisms I saw on the Barking Crab wharf compared to the healthy tide pools of Lovells island. This disparity might be due to the fact that we spend over an hour examining one hand-full of mussels and seaweed on the wharf and about 20 minutes peering into the tide pools, but I think that I am beginning to hypothesize that the wharf was more biodiverse that the Islands.

Overall it was a beautiful day out in the field and I left feeling very knowledgeable about snails. 

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