Resultados preliminares de la expedición de invierno del Sedna IV en el oeste de la Península Antartica: efectos de la radiación ultravioleta B sobre el Bacterioplancton, Picoplancton y Nanoplancton marinos

DEMERS, S.; MOREAU, S.; MERCIER, B.; LEMARCHAND, K.; LÓPEZ, D.; ROY, S.; SCHLOSS, I. Y FERREYRA, G. A.

Buenos Aires

Simposio; VI° Simposio Argentino y III° Latinoamericano sobre Investigaciones Antárticas; 2007

This research was developed in the frame of the international collaboration existing between Argentina (IAA) and Canada (ISMER), and was jointly funded by agencies from both countries. The Sedna IV mission represented the first phase of a project entitled: “Combined effects of Ultraviolet B Radiation, increased CO2 and Climate Warming on the Biological Pump: A temporal and latitudinal study”, which will last 4 years. Other three missions are planned to be deployed in both polar regions to achieve the goals of the project (Pto. Deseado cruise in December 2007, Antarctica; mesocosms experiments in Esperanza Station in January 2008, Antarctica and in Whapmagoostui-Kuujjuarapik Research Station, Arctic in July 2008). In 2006 the Sedna IV vessel overwintered (between March and November) in the vicinity of the Argentinean "Melchior" station. This allowed a detailed study of the effects of ultraviolet B radiation (UVBR, 280-315 nm) on the lower levels of the plankton food web before and during the ozone hole period. UVBR has been long recognized as highly harmful for aquatic organisms, particularly for those exposed at low depths in the water column. A significant portion of the Western Antarctic Peninsula in general, and the study area in particular, were characterized by relatively high air temperatures and low ice cover during winter and spring 2006. As a result, the water column presented some degree of stratification even during the colder months, which allowed plankton biomass accumulation in shallow waters (between ~10 – 50 m). Furthermore, the stronger ozone hole ever described took place during the spring 2006. During such period, UVBR reached depths > 20 m, thus potentially affecting the plankton community due to the fact that high residence time of cells in shallow waters increased their exposure to these radiations. Preliminary results from microscopy and flow cytometry analyses suggest the presence of modifications in the size structure of the plankton communities (phyto and bacterioplankton). Picoplankton dominated the community during winter, whereas nanoplankton was the most important size fraction during spring. In contrast,Combined effects of Ultraviolet B Radiation, increased CO2 and Climate Warming on the Biological Pump: A temporal and latitudinal study”, which will last 4 years. Other three missions are planned to be deployed in both polar regions to achieve the goals of the project (Pto. Deseado cruise in December 2007, Antarctica; mesocosms experiments in Esperanza Station in January 2008, Antarctica and in Whapmagoostui-Kuujjuarapik Research Station, Arctic in July 2008). In 2006 the Sedna IV vessel overwintered (between March and November) in the vicinity of the Argentinean "Melchior" station. This allowed a detailed study of the effects of ultraviolet B radiation (UVBR, 280-315 nm) on the lower levels of the plankton food web before and during the ozone hole period. UVBR has been long recognized as highly harmful for aquatic organisms, particularly for those exposed at low depths in the water column. A significant portion of the Western Antarctic Peninsula in general, and the study area in particular, were characterized by relatively high air temperatures and low ice cover during winter and spring 2006. As a result, the water column presented some degree of stratification even during the colder months, which allowed plankton biomass accumulation in shallow waters (between ~10 – 50 m). Furthermore, the stronger ozone hole ever described took place during the spring 2006. During such period, UVBR reached depths > 20 m, thus potentially affecting the plankton community due to the fact that high residence time of cells in shallow waters increased their exposure to these radiations. Preliminary results from microscopy and flow cytometry analyses suggest the presence of modifications in the size structure of the plankton communities (phyto and bacterioplankton). Picoplankton dominated the community during winter, whereas nanoplankton was the most important size fraction during spring. In contrast,”, which will last 4 years. Other three missions are planned to be deployed in both polar regions to achieve the goals of the project (Pto. Deseado cruise in December 2007, Antarctica; mesocosms experiments in Esperanza Station in January 2008, Antarctica and in Whapmagoostui-Kuujjuarapik Research Station, Arctic in July 2008). In 2006 the Sedna IV vessel overwintered (between March and November) in the vicinity of the Argentinean "Melchior" station. This allowed a detailed study of the effects of ultraviolet B radiation (UVBR, 280-315 nm) on the lower levels of the plankton food web before and during the ozone hole period. UVBR has been long recognized as highly harmful for aquatic organisms, particularly for those exposed at low depths in the water column. A significant portion of the Western Antarctic Peninsula in general, and the study area in particular, were characterized by relatively high air temperatures and low ice cover during winter and spring 2006. As a result, the water column presented some degree of stratification even during the colder months, which allowed plankton biomass accumulation in shallow waters (between ~10 – 50 m). Furthermore, the stronger ozone hole ever described took place during the spring 2006. During such period, UVBR reached depths > 20 m, thus potentially affecting the plankton community due to the fact that high residence time of cells in shallow waters increased their exposure to these radiations. Preliminary results from microscopy and flow cytometry analyses suggest the presence of modifications in the size structure of the plankton communities (phyto and bacterioplankton). Picoplankton dominated the community during winter, whereas nanoplankton was the most important size fraction during spring. In contrast, VI SIMPOSIO ARGENTINO Y III LATINOAMERICANO SOBRE INVESTIGACIONES ANTÁRTICAS - VI ARGENTINE AND III LATIN-AMERICAN SYMPOSIUM ON ANTARCTIC RESEARCH Dirección Nacional del Antártico / Instituto Antártico Argentino - 10 al 14 de Septiembre de 2007 - 10th to 14th September, 2007th to 14th September, 2007 bacterioplankton showed a more homogeneous distribution during the whole study. Since this work is still underway, these observations are not conclusive. More information from pigment analysis, photochemistry, C and N isotopes, and molecular analyses are presently being processed by the other components of the project, which will help to interpret the above results. The combination of high air temperature, low ice cover and a strong ozone hole allowed, by the first time, the study of the combined effects of these variables on the plankton communities of Antarctica. Previous studies suggested that increased UVBR during the Austral spring should not have significant impacts on planktonic organisms, since at that time ice is still at its maximum extent. However, our results suggest that the combination of global warming, and hence early ice retreat, could enhance the negative effects of UVBR on the marine biota more than thought. Such effects could propagate toward higher levels in the Antarctic food web and affect its dynamics, as well as carbon export.