Latitude: -53 10.2 Longitude -70 54.39 (Punta Arenas, Chile)
We are starting our final preparations before heading south… and we are ready to head south. After a few more days in port, we will begin our 4-5 day crossing of the Drake Passage, one of the most notoriously rough areas in the world’s oceans. We are ready to begin science!
Although there are four different National Science Foundation-funded projects on this expedition, they all have a common thread of exploring and discovering biodiversity on the Antarctic continental shelf, the sea floor region that extends from a continent to the steep slope that descends into the deep sea. The shelf of Antarctica is a bit different that in other regions of the world for a number of reasons. In most areas, the continental shelf is about 200m deep. However, in Antarctica, because of the weight of the ice pushing the continent down, shelf regions more typically about 400m deep. Also, because of the high latitude, the Southern Ocean region around Antarctica is bathed in nearly 24-hour light in summer and plunged into near 24-hour darkness in the winter. This light regime has a pronounced impact on the organisms. The well-lit summer months feed the region with energy for photosynthesis which is absent in the winter months. Thus, organisms in the region have evolved to handle this boom-bust energy cycle. At the end of the summer, much of the phytoplankton (small photosynthetic organisms in the water column) die and sink to the bottom, along with carcasses of zooplankton (small animals in the water column). This provides an incredible input of food to the organisms living on the sea floor, which can literally turn greenish from the input of phytoplankton – now called phytodetritus.
In addition to depth and energy dynamics, the Antarctic shelf is different because of the constant presence of icebergs which, because of their size and weight, can extend to the sea floor and become “grounded.” Grounding and movement of icebergs is a perpetual source of disturbance for the communities surrounding the Antarctic. This constant disturbance has likely contributed to diversity and resilience of Antarctic organisms. However, the rate and magnitude of such disturbances are changing due to human-mediated climate change. With more icebergs calving off of glaciers, the benthos (the habitat on the sea floor) will possibly experience an elevated frequency of disturbance.
What does this have to do with studying Antarctic biodiversity? Well, parts of the Western Antarctic are among the fastest warming regions on the planet. That not only means more disturbance, but organisms are shifting their biogeographic ranges because of changing water temperature. Importantly, because rates of climate change are greater in the Antarctic, organisms there can serve as a proxy for what to expect in other regions. However, in order to understand how organisms are responding, we first have to know who lives in these regions and their preferred habitat.
At this point, I would remind the reader that although we think of the Antarctic as a singular place, the content covers 14 million square kilometers, a region bigger than Europe, Australia, or the contiguous United States. So of course, there are different coasts, different environments supporting different communities of organisms that are uniquely adapted to their own particular environment. Given the remote nature of the Antarctic, we still only have a poor understanding of its diversity. That is what we are here study.
Dr. Ken Halanych