August 2, 2009
Lovell's Island, Boston
The first stop on our tour was a gravely beach with a small central patch of sand. This type of beach is known as a 'cobble beach'. Asked to search within the rocks of the last high tide swash, we found the discarded shells of the 'common periwinkle', blue mussel, and what I believe to be either the 'eastern white slipper snail' or the 'common Atlantic slipper snail'. Their size, shape, colour and location are both quite similar, unfortunately my rudimentary drawing and lack of sample or photo preclude me from a deeper identification.
After our seashell hunt, we were asked to find a periwinkle shell with a hole drilled into it, I was unable to do so, but I did manage to look at some that other members of our group located. After looking for an answer as to how these little holes were bored through such a tough shell, I believe that the culprit may be the 'green crab', based on an article written for the Northeastern Naturalist that states:
The green crab (Carcinus maenus), an introduced species originally from Europe, has been common in New England for a century or more (Bertness 1999). It occurs in almost all intertidal habitats in Boston Harbor, from mudflats to salt marsh to rocky tide pools and is a major predator on small “seed” clams and periwinkle snails. (source)
Our next task was the finding of a live periwinkle snail in the midst of all the rocks....harder than it sounded. Unearthing (unwatering?) the snails was a difficult task due to their inherent ability to blend in. I found that instead of looking for pebbles that could be snails, look for pebbles that are housing snails. Jackpot!
I named this little guy Herbie! The rock I found him on was just a shade bigger than he was! SO CUTE!
Anyway...Herbie has two antennae and a little flap that covers his aperture when he isn't out feeding. This also protects him from drying out should he get caught when low tide rolls in (out). Herbie likes to snack on the algae that grows on the beach and rocks, good for Herbie, bad for the beach. It is believed that Herbie and his friends are a major force in the 'altering' of the beach face....and not for the better. BAD HERBIE!
From our cobble beach we hiked over to a rocky clearing for a much needed lunch break! Of course, there is no rest for the weary, and Bruce called us all over to examine a find of discarded shells that did not look like they belonged on the beach.
Our mission...identify them! I have come to the conclusion that the shells are that of the grove snail or brown-lipped snail. The markings and size are in line with that of the grove snail, along with the distinctive 'brown-lip' around the base and opening of the shell. Hey...this science thing is quite intuitive!
After lunch we walked through a former salt marsh that is now overrun by phragmites and pepper weed. We used this new pathway to gain access to a tide pool where we snuck up on some birds! An array of gulls, sand pipers and oyster catchers were waiting for the ebbing tide so they could take advantage of the bounty the retreating seas would expose!
After giving the birds a wide berth, we proceeded to wade in the water looking for green crabs and attempt to catch some...scary right? Well this is how its done...
Props to Alexandra for catching the crab and Han for modeling the crab! This little guy, Gaston, only had one pincer claw and was missing a few of his legs...methinks he may have been prey to the birds we saw! Lucky to have rescued him, or sad that an invasive species did not get eaten? YOU DECIDE!
It was difficult to observe much in the tide pool since the water was still fairly high. We took that as a sign to explore the island further. We hiked along the paths and found an abundance of wild blackberry brambles! Not at all ripe yet, but we were able to find the odd berry ready for the picking
Thinking we were just taking a leisurely stroll through the woods, we were greeted with a hello from our old friend the brown-lipped snail! Bruce triumphantly displayed the find and then instructed us all to find them....
Now...there is a big difference between sifting through rocks and picking up shells, but we now have to essentially become birds of prey and seek out an animal designed to camouflage... apparently it is easier than I thought. Within moments I had spotted one clinging on to a dying leaf!
Notice how yellow Buddy is (that is his name, I asked him)...I was able to spot him through all the brown and green due to his garish colouring. You can also notice that the leaves around Buddy are all eaten, looks like he was a hungry boy!
We continued on collecting snails and shells as best as possible, taking a detour through an old fort made of concrete. Bruce mentioned that some snails liked to live in the calcium deposits leeching out of the mortar. I was able to spot a lot of the brown-lipped snails just hanging out in the nooks and crannies in the place.
I think we did okay considering this was our first snail hunting expedition!
Finally we had a choice, wander back to the tide pools, which at this point were at ideal low tide viewing, or someplace else...which I didn't even hear Bruce suggest because I was too excited about the prospect of returning to the tide pool...
When we got to the water, the landscape had changed drastically. Now there were more exposed rocks, small standing pools of water nestled in natural rock enclosures. Hundreds upon hundreds of periwinkles exposed and left clinging to rocks. It was literally as though the sea retreated exposing the underbelly of the ocean! Amazing!
Not content with what was just left on the surface, some of us schlepped into the water to see what we could find below the surface and below the rocks!
First attempt at overturning a rock proved to be quite abundant with life! There were several sea quirts attached to the rock, which, when used strategically can hit a person at 10 paces! There was also a tiny lobster under the rock...that got away...This discovery only fueled our resolve to find and catch one of these aggressive crustaceans. Wait. Did I just say aggressive? And did I also say I wanted to catch one?? Well..lets just say that after a couple of attempts to nab a lobster who is bent on fighting back, we were indeed successful in catching one! It was a smallish lobster with a soft shell, so I was reluctant to manhandle it too much. Hubert seemed to be in good enough spirits when we let him go. I think he enjoyed his time in the limelight.
That really concluded our field work right there. An exciting end to an exciting day!
Observed animals of note:
- Periwinkles one pair antennae
- Green crabs are non-native but eat the periwinkles
- Brown-lipped snails two pair antennae
- Sea Squirt
- Oyster Catcher
How did the land snails end up on the sea shore...
Well...At the end of the day I noticed a small grey bird foraging in the underbrush by the pavilion. I took note of its size, colour, beak and tail. I spoke to the friend of snails lady (name totally escapes me) and between us determined that it may be a catbird. When I came home I consulted my Sibley Field Guide To Birds of Eastern North America (what...you don't own one??) and it confirmed our suspicions. This type of bird likes to forage on the forest floor and eats insects and occasionally frogs and other types of smallish animals. I believe that this bird may have been responsible for the consumption and transportation of the land snail to the sea area.
The distribution of colour within the live snails looks a bit skewed. There seems to be more brownish shells and shells with thicker bands which leads me to believe that the brown is a better blender in this wooded environment.
That being said, when examining the empty snail shells, the distribution of colours seemed fairly even between light and dark shells.
Maybe the lighter ones did blend in more so we were unable to pick them out of the trees. Maybe the brown shells are older than the lighter ones. Maybe the snails have already begun breeding so their shells are darker and now the majority of the dead ones are going to be brown because of such. Based on the small sample it is difficult to determine what the correlation between shell colour and living/dead distribution is.
I re-read everyone's blog posts from our Saturday excursion, and I am pleased to see a coroborating guess to my thoughts on this plant:
I thought it to be Grinnell's Pink Leaf, but was not too sure. As far as other observations, I am still not quite sure about a lot of the organisms, but Bruce did mention the Colonial Tunicate (Metandrocarpa taylori). So I did some looking and I found one referred to as the 'orange social sea squirt' which strongly resembled the orangy organisms found on the side of the Barking Crab docks. The only solution to this problem...revisit the Barking Crab, grab a nosh, and reobserve the findings!