Hello,

This is Dan writing about Wednesday, November 19, 2003

The day started out with a dive expedition to a new site near Cape Evans. This site was the location of an iceberg scour several years ago, and there is a large track across the bottom where all the animals and algae were removed by the grinding of the ice. By now a few smaller animals have re-colonized this region, and the only clear delineation of the area is caused by its lack of coralline algae covering the boulders. Coralline algal crusts are the thin layers of calcified algal tissue that are found throughout the world, covering hard substrates in shades of pink, purple and red. These algae can tolerate extremely low light levels and are relatively slow growing, hence their absence from the ice scour area.

Large pycnogonid sea-spider, a relative of terrestrial spiders, on a coralline algae-encrusted rock at Cape Evans.

In the afternoon Jennifer and I went diving at a site not far from the sewer outfall in McMurdo to retrieve the time lapse camera which had been on the bottom filming (or so we thought) for the previous 24 hours. This deployment was a test run of a new camera system that was designed and constructed by Bill Watson, an engineer at Moss Landing Marine Labs who specializes in underwater instrumentation, with help from electronics wizard James Novak. The system consists of an off-the-shelf digital camera and strobes that are powered from the surface by large 12 volt batteries and 150 feet of cable. Because the water we are working in is 28° F (-2° C) batteries contained within the camera and strobes would die within a number of hours. We would ideally like to take pictures over periods of several days, and this necessitates having a power supply at the surface. The camera is kept dry in a hand built PVC and plexiglass housing which has a dome port for the lens and contains a voltage regulator to adjust for the power loss through 150’ of ice cold cable, and an intervalometer – a remote control device that triggers the camera to fire at regular intervals. The system works wonderfully, and it takes spectacular pictures,

Image taken with the new time lapse camera system.

but is sufficiently complex that operators with less than passable intelligence may find it difficult to push a series of buttons in the proper sequence to ensure that it is actually taking pictures in an automated fashion and not just sitting on the bottom like an expensive anchor. A valuable learning experience was had, one that will ensure the proper sequence of button pushing in the future. The purpose of this time lapse photography is to study the activities of the slow moving scavengers which inhabit the soft bottoms in the McMurdo region. Urchins, sea-stars and nemertean worms move slowly enough that divers have a hard time quantifying their rates of movement and feeding.
Something unquestionably yummy must lie at the bottom of this feeding-aggregation pile of nemertean worms (Parborlasia corrugata) and sea-stars.

These time-lapse sequences will allow us to determine the amounts of time that they spend in various activities, and also the intensity of feeding that occurs on different sediments (e.g., organic enriched, bacterial-mat covered, natural, etc.)