Monday, August 3, 2009
I had so much fun on Lovells Island Yesterday! First we started at the pier on the Island and quickly found our first observation stop, a cobble beach. I learned a little more about ocean terminology, like that the wrack line is the top of the tide line (where all the seaweed is left) which I can add to my vocabulary. There we learned about the Brazil nut phenomenon which has to do with physics and how bigger things, rocks and such, collect on top of the smaller things such as sand and smaller rocks. I thought this was really interesting. We collected a lot of shells including blue shell mussels and even a striped, spiral shaped shell that is definitely not native to this area. We then moved on to learn about the Periwinkle Shell, also a shell that is not native, though there is some controversy over that. This particular type of shell has really taken over beaches, meaning it has literally turned sandy beaches into rocky ones, by being able to hold onto the sand. This process happened over hundreds of years so it took people a long time to notice that these little shells were literally sucking the sand out of beaches. We then were told to find a shell that had a hole in it, as if something drilled in it, which I will later come back to some of my ideas as to what could have done that. Our second observation was a stunning view of the Brewster Island where we sat on a lot of much larger rocks then what was found in our first observation. Here was where I decided I would take a trip to the lighthouse before I leave Boston, thanks to Bruce! The third observation stop was at a salt marsh, or what was left of it. Unfortunatly, the marsh doesn't get any more water and has been taken over by two invasive species. The most disaterous one is the pepperweed, which covers the marsh and has literally pushed out all of the native species so there is a movement right now to erradicate the pepperweed. We found some pepperweed which is actually kind of pretty, with little white flowers on the top of it and whose root smells a lot like horseradish! Our last stop was where we observed some canadian geese and different birds which we confirmed were oyster catchers. Here we were told to go and turn over different rocks looking for a very small crab, with a very aggressive personality so we could later identify them.
1. What caused the holes in the Periwinkles?
After doing some research I found that the Moon Snail is the cause of the drill like holes. This website explained that they use a part of their mouth called a radule to drill a hole in their pray, and eat it. This website explained that the radula is kind of similar to a tongue with teeth making it possible to hold on until a hole is made. The source I used to find this was http://home.gwi.net/~allwet1/moonsnails.html.
2. What were the unusual snales?
My best guess, thanks to Bruce's helpful hints, is that the snales were dropped from the sky by a bird that preyed on them.
3. What kind of crabs were they?
I used google to help me figure out what kind of aggressive crab this could be. I came across this website http://aquanic.org/species/shellfish/documents/shellfishpredators.pdf which led me to believe that this crab is the "Blue Crab". This website pointed out that they are great in water and are very aggresive, and they also looked like the crab we saw, which led me to believe I found it!