October 20th

Dan Malone

The day started off with an early morning roundup of people and gear for another dive out at Cinder Cones. This dive site has been used by people doing research on the seafloor animals of McMurdo Sound for around 25 years. Because of this there are a number of relict experimental setups still lying on the bottom. One of our tasks today was to take video and still photographs of a series of settling plates which were set out by Dr. Paul Dayton in the early 70’s. These settling plates are pieces of PVC sheet which were attached to rods stuck into the bottom, and they are used to learn about the order in which new animal species recruit to bare substrate in a particular location. Since we know their dates of inception, they can also tell us how fast these animals grow and how long-lived they are. In the video clip below taken of one of these plates you can see bright pink colonies of the soft coral Alcyonium as well as several sponges etc. The laser marks you see in the image come from a set of lasers attached to the video camera. Two of the laser beams are parallel and spaced 15 cm apart, and are used as a scale bar to measure the size of objects in the image. A third laser is adjusted so its beam intersects one of the other beams at a distance of 1 meter from the camera lens. This laser is used to find a standard shooting distance when we are taking video transects, and it can also be used to tell us how far away an object is.

Click here for a 4.3 mb quicktime movie

While Jim and I were taking photographs and video we were pleasantly surprised by a visit from a curious young Weddell Seal. This seal was taking the time to swim around to each of the divers in the water (another dive party came out to use our hole at the same time) and seemed to be trying to puzzle out just what we were doing with our bright lights and flashes and sediment cores. The video below shows a brief segment of my personal seal encounter.

Click here for a 2.5 mb quicktime movie

In the afternoon we had another pleasant diversion in the form of a guided tour of the new sewage treatment plant for McMurdo Station. In a way the building of this new plant is a major reason for why we are here. The fact that raw sewage is no longer being pumped into the Sound provided the opportunity for a unique large scale experiment to study how marine community recovery will occur in an extremely cold, low productivity environment. No one knows if it will take years or decades for the species abundances in the areas polluted by the outfall to once again resemble those in pristine areas. Our tour guide Lane who operates the plant gave us a description of the treatment process including maceration, aerobic digestion, settling, the pressing of solids into “cakes” which are shipped back to the US, and ultimately the ultraviolet treatment of the clear effluent before it is released into the sound.