Control of Biological Exposure to UV Radiation in the Arctic Ocean: Comparison of the Roles of Ozone and Riverine Dissolved Organic Matter

• Published in: Arctic 2000-12, Vol.53 (4), p.372-382
• Main Authors: Gibson, John A. E., Vincent, Warwick F., Nieke, Barbara, Pienitz, Reinhard
• Format: Article
• Language: English
• Subjects: Arctic Ocean; Bacteria; Biological effects; Climate; Deoxyribonucleic acid; Dissolved organic matter; DNA; Fresh water; Latitude; Marine ecosystems; Oceans; Ozone; Ozone depletion; Ozone layer depletion; Photochemicals; Photosynthesis; Phytoplankton; Polar environments; Radiation damage; Radiation dosage; Sea water; Seas; Ultraviolet radiation; Water column; Wavelengths
• ISSN: 0004-0843; 1923-1245
• DOI: 10.14430/arctic868

Reports of severe stratospheric ozone depletion over the Arctic have heightened concern about the potential impact of rising ultraviolet-B (UV-B) radiation on north polar aquatic ecosystems. Our optical measurements and modelling results indicate that the ozone-related UV-B influence on food web processes in the Arctic Ocean is likely to be small relative to the effects caused by variation in the concentrations of natural UV-absorbing compounds, known as chromophoric dissolved organic matter (CDOM), that enter the Arctic basin via its large river inflows. The aim of our present study was to develop and apply a simple bio-optical index that takes into account the combined effects of attenuation by atmospheric ozone and water column CDOM, and photobiological weighting for high-latitude environments such as the Arctic Ocean. To this end, we computed values for a biologically effective UV dose rate parameter ("weighted transparency" or T*) based on underwater UV measurements in highlatitude lakes and rivers that discharge into the Arctic Ocean; measured incident UV radiation at Barrow, Alaska; and published biological weighting curves for UV-induced DNA damage and UV photoinhibition of photosynthesis. The results underscore how strongly the Arctic Ocean is influenced by riverine inputs: shifts in CDOM loading (e. g., through climate change, land-use practices, or changes in ocean circulation) can cause variations in biological UV exposure of much greater magnitude than ozonerelated effects. /// Des rapports concernant un appauvrissement sérieux de l'ozone stratosphérique au-dessus de l'Arctique ont accru les préoccupations au sujet de l'impact potentiel d'un plus fort rayonnement ultraviolet-B (UV-B) sur les écosystèmes aquatiques du pôle Nord. Nos mesures optiques et nos résultats de modélisation indiquent que l'influence de l'UV-B relié à la couche d'ozone sur les processus du réseau trophique dans l'océan Arctique est probablement faible en comparaison avec les effets dus à la variation dans les concentrations des composés absorbants naturels de l'UV, connus sous le nom de matière organique dissoute chromophore, qui entrent dans le bassin Arctique par le biais de l'eau amenée par les cours d'eau majeurs. Le but de la présente étude était de développer et d'appliquer un index bio-optique simple qui tient compte des effets combinés de l'atténuation due à l'ozone atmosphérique et à la matière organique dissoute chromophore dans la colonne d'eau, et de la pondé