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| We expect that the community near the outfall will begin to recover and become more like the community in surrounding uncontaminated areas as soon as sewage treatment starts. Today, the species that are found near the outfall are colonists, weedy species that are very good at growing in open spaces where they are disturbed often. In uncontaminated areas, climax species dominate; these are species that take a long time to grow and need a stable place to do so. We will observe the communities both near the outfall and far away, tracking changes in species over time. | 
These seastars and nemertean worms are examples of colonist species. |
This sponge is one of climax species found near McMurdo Station |
We think that the community will go through succession – from colonist species through climax species – though it may take decades for complete recovery. In temperate areas like Monterey Bay, communities show significant recovery within years. Many biological processes are slow in the Antarctic, including reproduction and growth, so we expect that it will take much longer for this polar community to recover completely. |
| There are two kinds of disturbance at the sewage outfall, one from the large amount of organic enrichment that provides a huge and unexpected food resource, and one from burial under the large amount of material released. In the past, we have always assumed that the community near the outfall is a result of organic enrichment, but we will test whether burial has an additional effect. | 
This hydroid is one species that may be highly sensitive to burial or to sediment suspended in the water |
A Weddell seal relaxes in one of our dive holes |
There are small natural deposits of organic material in the Antarctic, where seals and other large marine mammals defecate. These patches are quickly scavenged by seastars. We will contrast how these patches are utilized with how the large deposit from the sewage outfall is utilized. It appears that instead of seastars, microbes are doing most of the scavenging at the outfall. |
Hard substrates in near-shore Antarctic environments are dominated by sponges. These organisms can cover over half of the available space and grow to sizes of up to 2 meters tall and 1 meter wide. Studies on the growth and survival of these sponges have been conducted since the 1960’s and suggest that some of the largest species grow very slowly – almost imperceptibly - and are therefore probably extremely long-lived. On the other hand, some species which are at times very rare are capable of reproducing and growing rapidly and dominating the available space. During our field research we will have the opportunity to revisit study sites where data on abundance and the size of individual sponges has been recorded since 1967. This will allow us to add to a 35 year long record and generate insights into the population cycles and longevity of species in this unique community. Additional questions we will be pursuing include the following: If as previous studies suggest space is not limiting for settlement of new sponges, why are fast growing sponges in the genus Mycale often seen overgrowing other sponges? Are they using other sponges as settlement sites/ substrate? More importantly, are they able to escape from predation by the sponge-eating sea-stars Perknaster and Acodontaster by settling on or near chemically defended sponge species that these predators avoid?
In many of the coastal oceans around the world the water column is productive throughout the year with variations with season but food is always present. The Antarctic, especially at McMurdo Station, has a very short time period every year where food is abundant in the water column. This is in the spring when the ice breaks up and lets light get to the depths. The rest of the year the water column is devoid of food in the larger size classes. Instead the water column harbors bacterioplankton and ciliates . These animals are between 0.2 and 2 and 2 to 10 microns (*10-6 meters) in size, respectively. The animals that feed either have the option of waiting for the seasonal abundant food and starving for 10 months of the year or feeding on this "fine" fraction of the seston. This is really only key for suspension feeding animals, of which the Antarctic ecosystem is full from sponges to anemones to tunicates (aka sea squirts.) So the question is are the animals capable of feeding on the bacteria size particles that are ubiquitous throughout the year.
| Since the outfall at McMurdo sound spits out bacteria that came from humans it will have the isotopic signature of humans rather than that of the surrounding ecosystem. The particulate matter drops out of the water column near the outfall and the bacteria then spread downstream. The animals that eat this bacteria then retain the isotopic signature of what they are eating, in this case human waste along with the natural bacterioplankton. By taking the tissue from these suspension feeders and measuring their isotopic composition (Carbon and Nitrogen) one can tell if they were in fact consuming bacteria sized parcticles. Isotopes are measured with a Mass Spectrometer back in the lab. | 
The sewage outfall at McMurdo Sound. |
The infaunal (animals that live in sediment) community in the Antarctic has been hypothesized to "save" food in the sediment by mixing food below the surface when it is available. They then eat it throughout the year. Year after year sponges have been laying down spicules, small glass or calcium carbonate toothpick-like structures, and these form layers and possible inhibit this burying of food. Two treatments, one with fake spicules and one without these spicules are going to be put out in the environment for one year. At the end of the year one can see whether the spicules caused different communities to form or not.
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Here is a previous experiment similar what is planned. Photo Courtesy of Norbert Wu, www.norbertwu.com |
This project is based on the observation that scientists fishing for the emerald rockcod, Trematomus bernachii, through holes in the ice appear to fish out areas after a short period of time. It appears as if the fishermen catch all of the fish in a given area, and they are unable to catch any more in that area for a period of time , which indicates that it takes time for fish to recolonize the areas and that these fish do not move around much (they have small activity spaces or home ranges). This project has two parts, a removal portion and a site fidelity portion. The goal of the removal part of the project is to assess how the populations of T. bernachii within the study sites react to artificially lowered densities, which would mimic the impact of fishing. After tagging and determining a baseline density of fish within the study sites, we will then be able to remove a certain proportion of the fish and survey the sites to see how long it takes for the densities to reach pre-removal levels (how long it takes for fish to recolonize the sites). Tagging the fish serves the dual purpose of allowing us to see if the fish that we are counting are the same fish, and to see both the number fish that are moving back into the study sites and when they arrive.
The site fidelity part of the project is designed to see how much or little a fish
moves around its environment and how these movements might change according to the density of the fish. To do this you tag some fish with tags that allow you to
recognize individual fish (i.e. you use color coded tags). We will then lay a grid on the bottom around the study area, which will give us a frame of reference. Then we
will survey the site and observe the movements of the fish. By analyzing this data we will be able to see the general activity space or home range of the individual fish
and how their movements change when the fish are at different densities.
Picture courtesy of Dr.
John MacDonald
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