Wednesday, August 4, 2010
Lovell's Island - Experience, Observations, and Research
The trip to Lovell's island was the first opportunity I had in my life to visit an island in the middle of an ocean. As we left Boston Harbor at around 9.30 am, the tide was at the lowest level approximately. We took a ferry to the Spectacle Island from where we boarded a water taxi that dropped us on Lovell's Island at around 10.30 am.
Having a look at the beach, I could see that there were cobbled areas as well as sandy areas. The water clarity was about 8/10. There were wrack lines which probably were a result of the moon tides that hit the beach. I could see a lot of rockweed all around the beach which was left behind when the tide levels dropped.
We took a small trail and arrived at the beach. There were numerous tidal pools that were representative of the sub-tidal zones that were completely submerged in water when the tide was low. As we stepped in the tidal pools in search of the various species that were present, we toppled rocks in search of crabs. For the first time in my life, I went into the sea and also, for the first time in my life, I touched and picked up a crab. The experience was unique and frightening at times too when the crabs moved around my hand, poking me with its legs at times.
When we moved into the first shallow pool, the water was pretty warm as it was stagnant and there was a lot of sun falling on it, raising its temperature. The shallow tidal pools were rocky and had a lot of crabs as well as periwinkle snails. The rocks were mostly covered with tunicates and barnacles. As we moved along to the deeper tidal pools, the water got colder as due to it mixing with the sea water directly. I could see the water moving towards the shallower areas and starting to fill them up as an indication of the high tide levels starting to kick in. The deeper areas were filled with mussels, crabs, tunicates, barnacles, and periwinkle snails as well. We even managed to capture a small lobster.
After, we moved out from the sea and the high tide filled the shallow pools, we decended back towards the forest in search of land snails. We saw some empty shells of snails alongside one of the seashore rocks near the wrack line. We also noticed some shells in the water that had holes in them as if something drilled into the shells and sucked the living material out of them. Following this, we separated in groups to search for the different varieties of snails present in the woods. We examined their intricate structures and noted the differences between them. Finally, after having to catch some of the land snails and having a fun adventure in searching for them, we took the taxi back to George's Island from where we returned back to Boston.
Observations and Research:
I was able to see a lot of species in the tidal pools on the Lovell's Island. Small creatures and living organisms like snails, crabs, tunicates, barnacles, and weed were abundant in these tidal pools. There were some small fish, worms, sea squirts, and lobster present as well. They were different from the organisms we saw at the Barking Crab docks. The Barking Crab organisms mainly included weeds and very tiny creatures like very small fish and minute shrimp varieties. The habitat was very small in comparison to the tidal pools at the beach and the water at the Barking Crab was brackish with the docks mostly submerged in clear water. However, the tidal pools at the beach had salty sea water and it was mainly stagnant in many areas in times of low tides. The Barking Crab water was moving and it was much colder in comparison making it difficult for many creatures to survive. As the tidal pools were much warmer in comparison with minimal human impact or disturbance, there was probably much more bio-diversity found in them.
Species Observed at Lovell's Beach Tidal Pools:
1) Periwinkle Snails - There were a lot of periwinkle snails and they were spread across the rocky sub-tidal zone floors. They seemed to be black in color and have smooth oval shells on the top in which they hid themselves. They seemed to be about an inch in length.
These were most likely the 'smooth periwinkle snails' and were not found anywhere in the Barking Crab area probably due to the lack of rocky sea beds and few sea weeds. However, some could have been the 'rough periwinkle snails' as well depending on their shell texture. I only examined a few and found them to be smooth.
2) Hermit Crab - Cylindrical in shape. Many of the crabs actually occupied the shells of the periwinkle snails. They had fine thin legs with 2 pairs mainly visible. The body seemed to be in a brownish to blackish shade and seemed to have a smooth texture. They were almost 1.5 - 2 inches long.
This hermit crab seems to resemble the long-clawed hermit crab as due to its cylindrical shape and also the narrow major claw. It is hairless and smooth too with a dark brownish color. I think there was some kind of a crab spotted in the Barking Crab area by someone. But, I did not seem to find or see any out there. The Lovell tidal pools were full of the hermit crabs.
3) Green Crabs - These crabs were greenish in color and were 3-4 times bigger in size than the hermit crabs. They were seen around in both the sandy and the rocky parts of the sub tidal beds. They were around 3.5 - 4 inches in length with a flat and broad upper body. They also were smooth and had around 4 pairs of legs. Some were greenish in the bottom and some were pearlish white in the bottom.
It seems like these crabs were the rock crab or maybe the green crab species. Some of the bigger ones seem to have 9 frontal teeth and some smaller ones has 4-5 frontal teeth as seen pictures. They are found in sub-tidal waters in Mass Bay areas also and hence, it makes them a perfect match to the green crabs or the rock crabs. They may be blue crabs too howeveras due to bluish-green top color as well as claws bluish in color like in the middle picture above.
4) Barnacles - The rocks in the tidal zones were mostly covered with white colored barnacles. They were hard and pointy on the shells and had 4 -5 blackish stripes across. They were found in clusters of mostly and were very abundant.
It seems like the barnacles were the northern rock barnacles and the rough barnacles as many of them had 5-6 plates and a very rough texture. They could also be the down- under barnacles which have 4 plates and came from Europe. They were also present in plenty in the inter-tidal areas of the Barking Crab docks.
5) Tunicates - There were a number of tunicates present in the sub tidal waters of the Lovell's Island. They were in many different forms and in many different colors ranging from yellow to orange to deep red, purple, and green also. They were mostly found on many rocks in the rocky areas of the tidal zone and also near many sea weeds.
The tunicates probably included a the golden star tunicates, the orange/red sheath tunicates, or club tunicates. They could however even be orange sponges or even rubbery bryozoans rather than being tunicates. The golden star tunicates were abundant in the docks of the Barking Crab also indicating no preference for brackish or salty waters and also the size of the habitat. They only require sub-tidal zones to survive.
6) Squirts - There were bud like squirts that appeared on many of the rocks alongside the tunicates and the sea weeds. They were plump and looked spongy. However, they were rough on the surface and seemed to have tough layers of skin on them. On compressing, they squirted out water. They were approximately 1.5 -2 inches long and about an inch wide when dilated.
This squirting object is probably the rough sea squirt due to its rough texture. It seems to grow in clumped areas just like the above, and is about 1.5 inches in length as when observed. It was not seen in the Barking Crab area due to the lack of heavy clusters of weed and other organisms. However, it may be the stalked sea squirt also as due to its stalk that makes it pop out of the cluster of weed and also the yellowish color.
7) Lobster - We found a brown lobster which was almost 6 - 7 inches in length. It seemed to have 3 pairs of legs and had 2 lobes protruding from the front. The body surface looked to be smooth and ringed towards the middle and the back section.
This lobster was most likely the Northern Lobster. The small ones are mainly found in the sub-tidal zones with shallow waters. They have 3 pairs of legs and can be distinguished easily. Even though sometimes they have been seen in slightly brackish waters, they were not spotted at the Barking Crab docks.
8) Mussels - We encountered numerous different mussels with stripes along them and also with plain smooth surfaces. They were in black/blue colors to pale grayish shades. Their average length was about 2 inches long and about 1 inch wide.
I think that the striped mussels were the ribbed mussels or maybe the horse mussels and the plain smooth ones were the blue mussels. The ribbed mussels are generally found in salty marshes and are abundant in tidal banks. The blue mussels have bluish/blackish finish and are also characteristic of the the inter-tidal and sub-tidal zones. the horse mussels share characteristics with both the blue mussels and the ribbed mussels and are also found mainly in the sub-tidal zones. Horse mussels and Blue mussels were present in abundance at the docks of the Barking Crab.
9) Marking of Worm - We noticed certain markings made by a worm in the muddy sea bed of the tidal beds. They were swirly and seemed to have occurred when the worm would have dug into the ground.
They seem to be caused by the red sand worm which occurs typically around the area. It may also be due to a different worm like red-lined worm or even one of the mud worms or flat worms.
We initially saw the periwinkle snails in the tidal beds, especially in the rocky areas as discussed earlier. After identification we were able to conclude that they resembled the smooth periwinkle snails.
After, we observed the periwinkles, we observed the different kinds of land snails on the Lovell's island. We found snails with yellow shells and brown rings and also brown shells and black rings. There were some snails with whitish shells and multiple small brown rings on them.
The marine snails (periwinkles) were different from the land snails in terms of their lengths. The marine snails were much smaller than the land snails. The diameter of the shells of the marine snails were somewhere around 1/2 inch to an inch. However, the land snails ranged from a diameter of 1 inch to almost 1.5 inches.
Also, the marine snails has a smooth blackish shell without any stripes and the land snails has multicolored shells with brown and black circular stripes. The land snails can regrow some of the parts of their body if they are cut and they are attached to their shells permanently. Their breathing mechanism allows them to breathe through the pores in their lobes. Whereas, the marine snails intake the air mixed in the water in order to perform body processes. The land snails hibernate during the winter and their shells protect them from the cold. However, the temperature under the sea water remains fairly stable as due to ocean currents.
Periwinkle snails have a small body which is mainly confined inside the shell. They barely come out of the shell. They have really small lobes as seen in the picture. On the other hand, the land snails are move more vigorously than the marine snails. They have bigger lobes and on contact with water they come out of their shells.
The relationship that the marine snails and the land snails share is that they both have shells which have developed in order for them to accustom themselves to their surroundings. The marine snails have black smooth shells and smaller lobes in order to look like small black stones on the ocean beds and hence, prevent themselves from predators like the hermit crabs. Similarly, the land snails are larger in size in order to sustain their movements on land. They have larger shells with colored coils in order to camouflage in their surroundings like on leaves, tree barks etc. This helps them be safe from their predators. Hence, the both marine snails and land snails have similar but distinguished characters in order for them to adapt to their environments.
Snail Observations and Research:
1) Types of Snails - The land snails that we saw on the Lovell's Island had white colored lobes and black - brown colored lobes. Thus, they most closely resembled the white-lipped snails (Helix albolabris) as well as the brown-lipped snails or grove snails (Cepaea nemoralis). The shells colors and the rings do not seems to classify them in different groups. The colors are merely a way of adapting to the surroundings. However, the color of their lobes are important in determining the kind of snails they are and the group they belong to.
2) 5 Snail Shells - Big Rock Hypothesis - The 5 snail shells that seemed to have ended up near the big rock on the beach is most likely due to a predator of the snails. The predator hunted them down and brought them near the rock where it most likely broke their shells against the rock and ate the lobes.
After conducting research, it seems like the predator was a bird that feeds on small insects and snails. Also, Prof. Berman mentioned that the timing of our visit to the Lovell's island was towards the end of the bird breeding season suggesting that there was a lot of bird activity around the area in the recent past.
It seems that the bird was a thrush bird, particularly a hermit thrush and/or a song thrush. These birds build their nests in and around mud or use mud to build their nests. Hence, they are popular around muddy beach areas. Also, they are very common in the North Eastern US, hinting that it was this bird which probably brought the snails to the rock and ate its lobes after breaking open the shells on the rock.
However, there is another predator bird who could have possibly caused the latter. It is the snail kite. It exhibits similar characteristics as the thrush birds but, it is not very common in the north-eastern regions of the US.
I guess, thats the end of my blog post for our visit to the Lovell's Island on August 1, 2010. I had a lot of fun and bagged valuable once in a lifetime experience. I got an opportunity to do unique things which I had never done in my life and probably would never get a chance to do. I await the exiting experiences I will have in the next 3 days remaining in the course.
Snails - Pearce, Timothy, and Orstan Aydin. The Mollusks: A Guide to Their Study, Collection, and Preservation. American Malacological Society, 2006
Periwinkle - Dean, Cory. "Tiny Snail is Credited as a Force Shaping the Coast". NY Times Aug 23, 1988
White Lipped Snail - http://en.wikipedia.org/wiki/White-lipped_snail
White Lipped Snail - Morse, E.S.. "Plate 1". The Land Snails of New England'
Grove Snail - http://en.wikipedia.org/wiki/Grove_snail
Thrush Bird - http://en.wikipedia.org/wiki/Thrush_(bird)
Hermit Thrush - http://en.wikipedia.org/wiki/Hermit_Thrush
Song Thrush - http://en.wikipedia.org/wiki/Song_Thrush
Snail Kite - http://en.wikipedia.org/wiki/Snail_Kite#Description