IPY 194-COMBINED EFFECTS OF ULTRAVIOLET RADIATION AND CLIMATE CHANGE ON THE BIOLOGICAL PUMP: A TEMPORAL AND LATITUDINAL STUDY (BIOP)

PROYECTO ARGENTINO

Research on ultraviolet B radiation (UVB, 380-320 nm) and climate change are
two main subjects of interest in the international scientific community. Both
factors can act synergistically on ocean plankton communities modifying their
contribution to the dynamics of carbon fluxes between surface waters and the
deep ocean. It is assumed that physical processes control the fluxes of CO2
between the atmosphere and the ocean. However, part of this incorporation is
fixed by phytoplankton photosynthesis within the water column. It should be
noted that most of the estimations of biological carbon sequestration are based
on phytoplankton photosynthesis and chlorophyll a, and a great uncertainty
remains regarding both the magnitude and the contribution of autotrophic and
heterotrophic respiration of the plankton community to carbon dynamics.

Consequently, for a comprehensive understanding of the role of biology on
carbon fluxes to the deep sea (the “biological pump”), it is necessary to
account for the metabolic balance of the whole plankton community, i.e. the
balance between autotrophic production and autotrophic plus heterotrophic
respiration. Experimental results with mesocosms show that exposure of the
plankton community to enhanced UVB changes the community structure from large
cells supporting large grazers to a community dominated by small cells based on
dissolved organic carbon cycling (i.e. microbial food webs). The main
consequence of this is that most of the organic carbon is recycled at the
plankton community level, with low downward fluxes of particles (i.e., low
efficiency of the biological pump), contrasting with the more productive,
diatom-based herbivorous food webs. We expect different biological communities
to respond differently to the scenarios presented above as ecological
adaptations and genetic composition influence the degree of response to the
changing physical and chemical environment. The intensity and extent of these
modifications and their consequences within the frame of global warming remains
unknown.

This project will be developed onboard the ship SEDNA, which will navigate from
Canada to Antarctica within the frame of the “Mission Antarctique” project
(already presented as a project to the Canadian IPY secretariat and with own
financial support approved). This mission represents a unique opportunity to
test a series of scientific hypotheses derived from the above points because
present-day biological processes along a latitudinal gradient mimic temporal
changes that happen or are expected to occur due to climate change. Moreover,
the results of this project will be of valuable help to do a cross-ecosystem
intercomparison (temperate – tropical - polar).

First, we will take advantage of the trip from Canada to Antarctica to study
the different communities and their relationships with water column
characteristics (i.e. physical structure and dynamics, chemical composition and
bio-optics), within a latitudinal-biogeographical perspective. The structure
and composition of plankton communities, as well as the dynamics of carbon
transfers within the water column (photosyntesis, respiration, grazing, carbon
export and allocation within the different components of the community) will be
studied in detail. We plan to deploy, whenever possible, sediment traps to
measure the vertical transport of particles. UV radiation will be measured on
board and correlated to stratospheric ozone and clouds. We will characterize
also the optical properties in the water column (UV and visible) and in the
planktonic communities to relate light distribution and utilization to carbon
dynamics and trophic structure. These studies will be extended to remote
sensing of potential UVB effects. Determination of photosynthetic pigments,
particle absorption and quantum yield of photosynthesis will be determined
along the transect. On the other hand, the overwintering of the ship will allow
us to understand the above points on a yearly basis. Research onboard SEDNA
during 2005/06 will represent a pre-IPY (International Polar Year) project, and
is expected to be continued during the IPY in 2007 in collaboration with new
added partners (see below). Researchers from Argentina, Canada and USA will
participate in this pre-IPY phase, including several students who will work on
the ship and on land-based stations.

Serge Demers - Institut des Sciences de la Mer de Rimouski (Quebec)
�milien Pelletier - Institut des Sciences de la Mer de Rimouski (Quebec)
Jean Lemire - Glacialis Productions (Quebec)
Eddy Carmack - Institut of Ocean Science – Victoria (BC), Canada
Maria Vernet - Scripps Institution of Oceanography, USA
Irene Schloss - Instituto Ant�rtico Argentino & CONICET, Argentina

FIELD ACTIVITY DETAILS

Geographical location(s) for the proposed field activities: During the
spring-summer 2005-2006 a ship survey will be done in the area of the Antarctic
Peninsula, after an inter-hemispheric transect from Canada to Antarctica. This
phase will be continued by another one during the winter 2006 in the vicinity
of a coastal station, tentatively Jubany Station (Argentina).

Antarctic: September - October 2005: Transect onboard SEDNA from North America
to the Southern Ocean; November 2005 -– January 2006: Subantarctic islands
(Malvinas, Georgias, Cabo de Hornos, Diego Ramirez, Elephant Island);
January -– April 2006: Navigation around the Eastern and Western Antarctic
Peninsula; May –- October 2006: Overwintering of the ship SEDNA in the Western
Antarctic Peninsula (place to be confirmed); November -– December 2006: trip
back to Canada.

The ship SEDNA will provide the necessary facilities for the development of the
scientific activities, as well as connection with schools and public media in
real time. Proposed ice-breaker candidate with helicopter facilities: Almirante
Irizar (Armada Argentina). The icebreaker will provide losistic support for
cargo and personnel transport, and eventually for sediment trap recovery and
instrumental deployment at sea.(2)SEDNA will overwinter close to a coastal
station. A proposed candidate is Jubany station (Argentina). The station would
provide security and logistic support, as well as support from the
meteorological observatory.