Tuesday, August 3, 2010

Class #4

I had so much fun at Lovells! I’m already planning my next trip back, hopefully to camp. The island and the shoreline habitats seemed to be typical of a Massachusetts harbor, with marsh grass in some areas and a rocky shoreline. When we arrived at the island, it was around 11 in the morning and the tide was extremely low. Mostly the water was clear so I could see right down to the bottom, but in some areas dust had settled on the top so clarity was a little less. I noticed that the temperature changed dramatically between tide pools, with shallower water and water closest to shore being the warmest, and the water closest to the open ocean was the coldest because of the incoming tide.

In general, I noticed that the habitat of the tide pools was very different than the habitat of the Barking Crab piers. There was noticeably less seaweed, and instead of amphipods I mostly saw crabs, periwinkles, hermit crabs, and sea shells. The tide pool habitat clearly supported a much greater amount of species than the underside of the pier. I assumed the difference came from the fact that the tide pools are constantly being altered as the tide comes in and goes out, whereas the creatures living under the dock seemed to live amongst the seaweed attached to the floats. What was similar between the two habitats was that they both provided intricate ecosystems for the creatures living there. Under the dock, much of the life seemed dependent on seaweed and created a small habitat within itself. In the tide pools, I noticed that on most of the large rocks, entire ecosystems had formed to look like small reefs. On these rocks were periwinkles, tunicates, many different kinds of shells, seaweed, and crabs.

Green crab: dark in color, like a deep green. Small (body about ½ inch in length) with ten total legs. It had two front pinches, and its two back legs were a little thicker and pointed straight back instead of to the side.

Wharf crab? Different colors of green, looking almost like camouflage. Ten legs total with two front pinchers , a flat, squared face with its eyes pointing sideways. It looks most similar to the Wharf crab but the tide pool habitat isn’t completely conducive to its habitat described in the guidebook. Since I couldn’t find any other similar crab in the guidebook, I turned to the internet to find it. Looking up “crabs with square fronts” I came upon the Asian Shore crab which seems to match the description. Living in intertidal zones, matching in color and size, this crab is also invasive to the area and as an omnivore not only eats the food of native species but also displaces the habitat of the native mud crabs.

Source: http://fl.biology.usgs.gov/Nonindigenous_Species/Asian_shore_crab/asian_shore_crab.html

Say’s Mud Crab? This crab is about an inch in length, lightly-colored green and brown, with a rounded front and eight total legs. I could not find an exact match to this crab, but I think it may be some sort of mud crab based on the description and appearance of the Say’s Mud Crab.

Orange Sheath Tunicate? I saw a lot of bright orange tunicates covering rocks and even floating in a piece that looked like coral. This tunicate was different than the ones we saw at the Barking Crab because instead of having a flower-like pattern, I could see small pores covering the surface.

I also saw a few birds either in the tide pools or flying in the area. One flock of birds in particular circled the area a few times and I managed to get a picture of them. From what I can see, they have orange bills, a black head and neck, a dark grey body with white patches on the wings. Looking at the Reader’s Digest Book of North American Birds I think the birds were American Oystercatchers which eat mollusks, starfish, and marine worms. The other birds I saw were seagulls, and looking at the pictures I have of them I think they were Ring-billed Gulls. The seagulls were most interesting to me because I thought following them in the tide pools might lead me to finding crabs in the water.

The small lobster we saw looks like it could have been a Northern Lobster based on the description in the guide book.

The two most prevalent animals in the tide pools were probably the periwinkles and hermit crabs. Though I never saw a periwinkle come out of its shell, I did see a hermit crab change shells which was really cool. I got a picture of the un-shelled crab where it looks like a tiny lobster.

Moving on to the snails, I have always seen the Common periwinkle on the beaches of Massachusetts but never paid them much attention. Learning that they’re an invasive species makes sense of the fact that they spread so easily and seem to be everywhere. The periwinkles were much smaller than the land snails, they did not easily come out of their shells, and they were clustered in much larger groups than the land snails. The Common Periwinkle (the marine snail) and the Brown-lipped snail (the land snail) were both likely introduced to the U.S. from Europe. Seeing as they live in two entirely different ecosystems, I hypothesize that the relationship between the two snails is relatively small because they are not competing for resources in the same habitat, and are therefore probably having a small effect on the survival of each other’s species. As for how those five snails got on the beach, I at first thought that snails were possibly exothermic and were sitting in the sun to gain energy but I think we would have seen more snails sitting in the sun for this to be true. Another possibility would be that those snails had been on a nearby tree and could have been blown on to the beach by a heavy wind, or that a predator of theirs had taken the snails from their habitat to eat them on the sand.

-Lydia T

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