Journals 2008/2009

Roy Arezzo
New York Harbor School, Brooklyn, New York

"Impact of Climate Change on Antarctic Shelf Ecosystems" FOODBANCS2 Project, Antarctic Peninsula RVIB NATHANIEL B. PALMER July 7 - August 7, 2008

Journal Index: July 10 - 11 - 12 - 13 - 14 - 15 - 16 - 17        18 - 19 - 20 - 21 - 22 - 23 - 24 - 25        26 - 27 - 28 - 29 - 30 - 31 August 1 - 2 - 3 - 4 - 5

August 5, 2008
Project Summary

After the last of the scientists left town, I stuck around Punta Arenas to finish up some work and travel around southern Chile. I met with a friend from New York Harbor School and we traveled to Port Natales for an epic six-day backpacking trek through Torres Del Paine to get a taste of Patagonia. We covered over 88 kilometers through snow, ice, and rocky terrain and were rewarded with incredible images and memories. Our excursion also served as a great opportunity to discuss the FOODBANCS work, fresh from Antarctica, with someone from home in preparation for sharing my experiences with my students.

The Antarctic Peninsula is a region of majestic beauty. Sea ice is a marvel to witness and important to the polar ecosystems. Unfortunately, it is this sea ice that is diminishing as warming at our poles increases. When I returned to the States I found some alarming articles on climate change and Associated Press reports of about sea ice reductions in the Arctic Sea waiting for me at home (http://news.yahoo.com/s/ap/20080827/ap_on_sc/sci_arctic_ice).

The results of the FOODBANCS projects along the Antarctic Peninsula will serve as important baseline data in bentho-pelagic coupling to compliment long-term pelagic and euphotic zone research conducted as part of the Antarctic Program (Palmer Station LTER and GLOBEC Programs). Having had time to reflect and read papers that I probably should have digested before the project, I realized there are a few unanswered questions that warrant more explanation in my journals.

What is a "Food Bank"?
This is an important question absent from my writings and something the reader (if anyone is still reading), should be asking. A food bank refers to the build up of nutrient rich sediment on the seafloor. The top five centimeters of sediment we sampled tends to have the freshest carbon (or "food") materials and the deeper layers have older, less nutritious materials. The sources of these materials vary in their origin - some derived from current driven sediment transport and sea-ice melt. Some organic goodies come from the short summer bloom when there is an increase of sinking phytoplankton of the euphotic zone. Once on the seafloor, these materials cycle very slowly due to the deep-water temperatures that remains cold throughout the year. The deep-sea organisms that interact with nutrients do however allow for continued cycling in a myriad of ways, contributing to the upward movement of nutrients for communities above, helping to support a wealth of life. The food webs of Antarctica are far more complex than originally thought possible.

How does the benthos serve as a lens to study climate change?
Through FOODBANCS research, it appears that the Antarctic shelf seafloor is more "stable" than originally believed; filtering out seasonal "noise" as compared to pelagic cycles. Due to the build up of a nutritious food bank layer on the seafloor, the benthic community responds less to seasonal fluctuations, serving as a "low pass filter" and making it possible to monitor long term changes in Antarctic production cycles. FOODBANCS1 data from1999 to 2001 demonstrated that food for the benthos fluctuated more from year to year than it did between seasons at Station B. Much of the annual differences were due to shorter sea ice durations, attributed to warming trends.

What will we learn from FOODBANDS2?
In February '09, FOODBANCS will be back out at the Western Antarctic Peninsula for the last of thrre cruises to collect data in the austral summer along the latitudinal transect. Analysis of the structure, reproductive condition and feeding rates of the seafloor biota will be compared and contrasted with the biogeochemistry of the water column and sediments. Using special dating techniques, the origin of seafloor organic materials will be determined.

Thorium-234 is a naturally occurring radioisotope that is regularly created from the radioactive decay uranium salts in seawater. Thorium-234 can serve as an indictor of the "freshness" of organic material. When thorium-234 is formed, it readily bonds to available organic particles passing through the water column. Thorium-234 has a short 24-day half life, meaning that any bottom sediments containing extra thorium-234 atoms absorbed in the water column have been recently added to the sediment food bank. Carbon-14 data will tell us the origin of older materials. Data from sediment traps, water samples, seafloor sediments at various depths, and sediment from the tissue/guts of deposit feeders will be analyzed to give a fuller picture of community nutrient cycling. This information will be correlated with biodiversity and biomass data from microbes to megafauna to provide us with a complete picture of seasonal and annual fluctuations in carbon and nitrogen cycling, the key ingredients of life, along a latitudinal sea-ice gradient.

Although I am sad to see my summer come to an end, I look forward to remaining connected to the FOODBANCS project as the story unfolds and new information becomes available. I once again would like to express my gratitude for this opportunity and wonderful experience to The ARMADA Project, the National Science Foundation, Craig Smith, David DeMaster, and all the scientists and crew of the NATHANIEL B. PALMER, University of Hawaii, North Carolina State University, and University of San Paulo, Brazil.

Important final award to Dr. Craig Smith given out at the end of the cruise

Missing the ice already