Saturday, August 2, 2008

Saturday observations - Ann

Observations of biodiversity in Boston’s Inner Harbor

Location: Barking Crab floating pier, collections were made from the subtidal zone less than 6 inches from the surface

Observing conditions: sunny, about 75 degrees, effectively no waves; water visibility to about 1 foot
Location 1 is likely permanently in the shade (under bridge)
Location 2 was sunny at 10:30am, and likely at least half of the day

Methods: Observation using visual inspection, drawing and attempted identification using Peterson’s Field Guide to the Atlantic Seashore. Tools: penknife, pen, paper

Location 1
Pre-collection observations: mussels, sea anenomes, flat green seaweed

Collection 1 was of a mussel shell that had a number of baby mussels attached to it and a number of small (~3-5mm) creatures that we initially identified as being cumaceans.

Collection 2 was also of a mussel shell and was targeted because it had a number of sea anemones on it. It also was found to have baby mussels and many of the apparent cumaceans on it, as well as what may have been a tiny starfish (~2mm across).

The tentacles of the anemones, which were floating open under water, immediately contracted in when removed from the water so that the animals looked like soft columns stuck to the shell. They opened up again within 10 seconds of being re-submerged. Tentative ID based on book description and ruling out other options: Frilled anemone (Metridium senile)

Collections 3-4 were all of the jelly-like orange stuff, which we were very curious about but had a difficult time identifying. Each of the three collections had a slightly different appearance. They were similar in that they were all bright orange with semi-regular patterns (dots on one and kidney bean shaped sets of dots on another) and had a jelly/gummi-like consistency. The side that attached to the underlying substrate was opaque but uncolored. We speculated at the time that they could have been sea pork, boring sponges or colonies of young sea squirts.

Location 2

A single collection was taken in this location to determine whether the mystery orange stuff had a different morphology in a sunnier environment. The sample included was of a mussel shell which was coated by the orange stuff and also had many of the cumaceans on it. The orange stuff in this sample had a number of projections that made it appear as if towers were growing out of it. At the time, I hypothesized that this could be a more adult version of what we had seen in the previous collections, or perhaps Loosanoff’s Haliclona. However, the latter was rejected because the northern end of its range is south of Cape Cod. Based on further reading and class discussion, I now believe that they may be the fouling organism known as the orange sheath tunicate.

Finally, we spent quite a lot of time attempting to identify the things we generalized as cumaceans. We had a difficult time identifying them more specifically than that because they are very small and move a lot, making them difficult to observe closely. Although we saw a number of morphotypes in all of our collections, there was one in particular that we saw only in the sunny location. This one looked less like the others in that its body did not swell as much; rather, it looked much like a stick with legs. When we spread out all of its appendages, it also looked like kokopelli . I now hypothesize that this was a skeleton shrimp (Caprella) and that the others that we initially observed were cumaceans, though I do not know what species.

Final tally of observed species (all identifications are tentative)
Sea lettuce
Blue mussels (young and grown)
Frilled anemone
Possible starfish?
Orange sheath tunicates
Many cumaceans
Skeleton shrimp