Abstract
MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 199:69-81 (2000) - doi:10.3354/meps199069 Effects of ultraviolet B radiation on simultaneous carbon and nitrogen transport rates by estuarine phytoplankton during a week-long mesocosm study Laure Mousseau1,*, Michel Gosselin1, Maurice Levasseur2, Serge Demers1, Juliette Fauchot1, Suzanne Roy1, Piedad Zulema Villegas1, Behzad Mostajir1 1Institut des sciences de la mer de Rimouski (ISMER), Université du Québec à Rimouski, 310 allée des Ursulines, Rimouski, Québec G5L 3A1, Canada 2Institut Maurice-Lamontagne, Ministère des Pêches et des Océans, CP 1000, Mont-Joli, Québec G5L 3Z4, Canada *Present address: Observatoire Océanologique, BP 28, 06230 Villefranche-sur-Mer, France. E-mail: mousseau@obs-vlfr.fr ABSTRACT: The effect of UV B radiation on photosynthesis and nitrogen uptake by an estuarine phytoplankton community was investigated during a week long experiment, conducted in 8 mesocosms under varying conditions of UV-B radiation: reduced UV-B, natural radiation, and 2 levels of enhanced UV-B. Twice a day, dissolved inorganic carbon (13C) and total dissolved nitrogen (15N) transport rates were estimated simultaneously from in situ incubations. Irrespective of the treatment, phytoplankton biomass (chlorophyll a) and primary production increased over the first 3 d. Subsequently, nitrate and silicate depletion resulted in a decrease in algal biomass and productivity. Enhanced UV-B radiation was deleterious to chlorophyll a specific transport rates of C and N when compared to reduced and natural UV B. The C:N transport ratios, as well as the POC:PON ratios, were generally not affected by enhanced or reduced UV-B. In the enhanced UV-B treatments, carbon transport rates were often significantly higher in the afternoon than in the morning, suggesting that phytoplankton exposed to UV B developed photoprotective mechanisms against UV radiation on a daily basis. A shift in the algal community assemblage from diatoms (>10 µm) to small flagellates (5-10 µm) was observed during the study. Small flagellates were less sensitive to the UV B treatments than diatoms, whose abundance decreased under reduced and enhanced UV B. Results from this study suggest that UV B exposure on a daily basis could change the chlorophyll a specific transport rates of C and N and alter the structure of the phytoplankton community. KEY WORDS: Mesocosms · Nitrogen transport · Photoinhibition · Photosynthesis · Phytoplankton · St. Lawrence Estuary · UV B radiation Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 199. Publication date: June 26, 2000 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 2000 Inter-Research.
Highlights
The recent decline of the stratospheric ozone concentrations has resulted in a major increase in ultraviolet-B radiation (UV-B:280-320 nm) reaching the Earth's surface (Kerr & McElroy 1993),causing concern about the influence of UV-B radiation on living organisms
For total nitrogen transport rates, negative percent changes were observed from the beginning to the end of the experiment in the HUV-B treatment while the values remained negative after Day 3 A.M. in the LW-B treatment (Fig. ?c,d)
UV-B radiation reaching the Earth's surface is considered a natural stress for aquatic organisms (Behrenfeld et al 1994).This study provides the first results of the effects of UV-B radiation on the simultaneous transport rates of dissolved inorganic carbon and total dissolved nitrogen (i.e.nitrate + ammonium + urea) by phytoplankton estimated with stable isotopes (13Cand 15N).This study represents the first such attempt on natural phytoplankton communities, as opposed to those conducted with laboratory cultures under totally artificial illumination conditions
Summary
The recent decline of the stratospheric ozone concentrations has resulted in a major increase in ultraviolet-B radiation (UV-B:280-320 nm) reaching the Earth's surface (Kerr & McElroy 1993),causing concern about the influence of UV-B radiation on living organisms. The irnpact of such changes in ambient solar radiation on plank-. Several studies have shown that ozone depletion was occurring in temperate and arctic latitudes, leading to a corresponding increase in UV-B radiation (Kerr & McE1roy 1993,Fioletov & Evans 1997,Fioletov et al 1997,Rex et al 1997,Tarasick & Fioletov 1997). It has already been shown that UV radiation can reduce phytoplankton growth (Jokiel & York 1984)and photosynthesis (Smith et al 1992, Goes et al 1996, Helbling et al 1996b, Furgal & Smith 1997), change photosynthate allocation (Dohler 1989,Furgal et al 1998,Smith et al 1998), alter nitrogen metabolism (Dohler 1985, 1992, 1997, Behrenfeld et al 1995, Dohler & Buchmann 1995, Goes et al 1995, Dohler & Hagmeier 1997, Fauchot et al 2000), modify biochemical composition (Dohler & Biermann 1994, Goes et al 1994), and alter phytoplankton community structure (Jokiel & York 1984, Dohler & Biermann 1987, Helbling et al 1996a,Santas et al 1998)
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