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

Abstract

ABSTRACT. 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.Key words: Arctic, CDOM, DNA, global change, ozone depletion, phytoplankton, Siberia, transparency, ultraviolet radiation RÉSUMÉ. 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 pondération photobiologique pour les écosystèmes des hautes latitudes comme l'océan Arctique. À cette fin, nous avons calculé les valeurs pour un paramètre de débit de dose UV qui ait une action biologique («transparence pondérée» ou T*) fondée sur des mesures sous l'eau du rayonnement UV dans des lacs et cours d'eau de hautes latitudes qui se déversent dans l'océan Arctique; sur des mesures du rayonnement UV incident à Barrow, en Ala...

Contribution of absorption and scattering to the attenuation of UV and photosynthetically available radiation in Lake Biwa

“…There are many indications that climate change-related modifications of CDOM input to aquatic ecosystems are likely to affect biological UV exposure in the underwater environment to a greater extent than ozone depletion (Gibson et al 2000;Pienitz and Vincent 2000). Our results suggest that modifications of particle input may also significantly affect UV exposure.…”

Potential for Mercury Reduction by Microbes in the High Arctic

“…Photochemical rates of reduction and oxidation were based on previously published data for temperate coastal marine systems and ranged from 0.1 h Ϫ1 to 1.4 h Ϫ1 for photooxidation (33,34,63) and from 0.4 h Ϫ1 to 1.58 h Ϫ1 for photoreduction (1,63). UV energy attenuation was calculated using an empirical model based on dissolved organic carbon concentrations used for Arctic ocean waters (25). Dissolved organic carbon concentrations for Arctic water ranged from 43 to 225 mol liter Ϫ1 , as observed for the central Arctic Ocean (10).…”

Marine CDOM accumulation during a coastal Arctic mesocosm experiment: No response to elevated pCO2 levels

“…The Arctic Ocean receives substantial riverine input of terrestrial organic matter including CDOM [e.g., Dittmar and Kattner, 2003;Stedmon et al, 2011]. The presence of CDOM profoundly affects the physics, biogeochemistry, and biology in the upper layer of the Arctic Ocean through radiative heating [Pegau, 2002;Granskog et al, 2007;Hill, 2008], availability of photosynthetically active radiation (PAR) for photosynthesis [Granskog et al, 2007], photoprotection of marine organisms from harmful UV light [Gibson et al, 2000], and photochemical transformation of organic matter [Osburn et al, 2009]. Practically, due to its effect on remotely sensed ocean color, CDOM must be properly taken into consideration when primary productivity is assessed in the Arctic Ocean [Matsuoka et al, 2007;Popova et al, 2012;Bélanger et al, 2013].…”