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>Seas: < 3-4 feet
>Winds 25 knots
>Temp -1 C ; w/ wind chill –20 C
>Location: Latitude 63 degrees 15.83’ S; Longitude 60 degrees 44.03 W

Three views of Admiralty Bay, long harbor halfway along the south side of King George Island
Click on each image for larger view.

6 December 2004

Hello all. As pleasant as the temperature was yesterday (1.5° C), today has simply been cold. Outside at present the temperature is –18.1° C (w/ wind chill), the wind is blowing at 30 knots, and it is lightly snowing. Ah, what a wonderful day to be at sea and working on the deck.

Today has been an interesting exploration of the interaction of physical oceanography and biology. The Bransfield Strait is dominated by two hydrographic features: a northern warmer flow that is an offshoot of the Antarctic Circumpolar Current and a southern colder flow that comes out of the Weddell Sea. The maximum difference is approximately 4° C, a rather wide range in these waters. There is an apparent difference in the abundance of invertebrate larval forms between these two flows. The northern (warmer) flow has a relative abundance of larvae of sea stars (asteroid echinoderms) and ribbon worms (heteronemertean nemerteans). The colder southern side of the Bransfield Strait, in contrast, contains relatively few larvae. I am told that much of the Weddell Sea is covered with ice and, as a consequence of lower light penetration, there is less photosynthetic activity in these waters (less food for filter feeding adults and planktotrophic (feeding) larvae). We’ll need to complete a few more transects across the Strait in order to more clearly evaluate this hypothesis.

Our main activity was to process a rather large and diverse sample of the fauna from the seafloor. It required ca. 8 hours to sort, photograph, and preserve these specimens. This trawl contained an unusually high number of comatulid crinoids (feather stars). These echinoderms are considered by most to be basal to this clade. You may recall that they possess open ambulacra, are suspension feeders, attach to hard surface by cirri, and both the mouth and the anus open on the aboral surface. They are truly remarkable animals and I wish you all had an opportunity to see them alive….. perhaps we could arrange a field trip?

Another unusual find was an apparent symbiosis between a snail and a sea anemone. In several trawls we have noticed that one particular snail always has a sea anemone (a relative of corals) covering its shell. Although nobody in our group knows these species, it does seem reasonable to hypothesize that these two have entered into a mutualistic symbiosis [a state of coexistence where both members benefit from the interaction]. The anemone would be provided with a home (a hard surface to attach) and the snail may experience lower predation pressure owing to the presence of the stinging tentacles of the anemone. This would be an interesting system to study.

I know finals will begin soon — I wish you all well.

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