Saturday, July 31, 2010
Day 3 - The Barking Crab
Species we examined today:
Before leaving Long Wharf, we described two types of seaweed on the seawall. The first was a green grassy seaweed which clung to the rocks like moss when dry and drifted in the waves like grass underwater. We did not examine it up close but based on the NE Aquarium Seaside Educator's Guide descriptions this was probably Cladophora sp.
Also on the seawall was a greenish-brown seaweed which Professor Berman referred to as rockweed. Later, at the Barking Crab, we pulled up a piece of what I believe to be the same seaweed. Prominent features I noticed included a well-defined vein or rib running down the center of the leaf and air-filled bladders at some of the ends. This is certainly some type of Fucus, probably Fucus gardneri.
There was a fairly sharp line between where the green Cladophora grew on the seawall and where the rockweed grew, with the Cladophora higher. The Cladophora can probably survive with less exposure to the water than the rockweed.
At the Barking Crab, we pulled out a ribbon of red seaweed, about 8 inches long and 2 inches wide. It was slimy to the touch. I think it was a piece of Irish Moss, Chondrus crispus.
There was also a wide, thin leaf of bright green seaweed which appeared to be Sea Lettuce, Ulva lactuca.
The Blue Mussel (Mytilus edulis) was the predominant and most easily identified animal living on the float. The clumps of mussels formed a sort of substrate on which many of the other plants and animals lived.
The first thing we noticed about the clumps of mussels we pulled off the dock, other than the terrible smell, was that they were teeming with small animals running around on them. On closer inspection many of them appeared to be small shrimp-like creatures, probably amphipods.
There were some rather curious insect-like that were attached to the mussels at one end and sort of curled or waved through the air (presumably they did the same thing in the water. The were sort of reddish-brown, and mostly under an inch long. They had segm
ented bodies and small hooked claws similar to those you would see on a mantis. This is certainly some sort of skeleton shrimp, probably the long-horn skeleton shrimp, Aeginella longicornis.
On some of the mussels there was a sort of orange gooey spongey stuff which probably was some kind of sponge, but it's difficult to identify which.
Some of the mussels were covered in orange flower-shaped colonies about a centimeter across. I also saw a piece of seaweed that appeared to be encrusted with this. The NEAQ guide indicates these are probably Golden Star Tunicate, Botryllus scholsseri.
One of the more mysterious things we found were what at first appeared to be brownish sacs, about an inch in size, containing a clear mucous with various organs embedded inside. Closer inspection of the outside showed that it was in some instances translucent, and the brown may have been algae or dirt encrusted on the outside. Several of these sacs were attached to each other, like pods on a string. Although we siphons weren't particularly evident in any of those we examined, the field guide seemed to indicate that a sea squirt or tunicate was the most likely identification, and the NEAQ guide calls them Sea Grapes (Molgula sp.), which are a type of tunicate. It seems surprising to me that these creatures would belong to the same group as the star tunicate colonies found on the mussels. Some reading shows that there is a lot of diversity within the tunicates, and even within individual species they have surprising (to me, at least) life cycles.
We caught a small crab, about an inch wide, brownish with white tips of its appendages. It looks like a shore crab from the Hitchhiker's Guide.
We caught a small fish as well, which I drew a pretty sad picture of but haven't been able toidentify.