D.S. Venables, E.R. Ashu-Ayem, U. Nitschke, C. Monahan, J. Chen, S.B. Darby, P.D. Smith, C.D. O’Dowd, and D.B. Stengel

European Geosciences Union Annual Assembly

Release of I2 by Laminaria digitata in chamber experiments

Vienna

Poster Presentation

2012

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Current emission rates of I2 from tidally-exposed macroalgae are poorly constrained and reported emission rates vary by three orders of magnitude. Here we quantify I2 emissions from 25 Laminaria digitata (Phaeophyceae) samples investigated in a simulation chamber using a broadband cavity-enhanced absorption spectrometer. The chamber design allowed for gradual extraction of the seawater during experiments to simulate tidal emersion. Samples were exposed to air with or without ozone and to varying irradiances. Molecular iodine emission occurred in four distinct stages: moderate emissions from partially submerged samples (stage one), followed by a strong release by fully emerged samples (stage two) and slowing or stopping of I2 release (stage three). In some samples, later pulses of I2 were evident (stage four). Emission rates ranged from 7 to 616 pmol min-1 gFW-1 (FW: fresh weight) in ozone-free air, with a median value of 55 pmol min-1 gFW-1 for 20 samples. Our relatively large dataset provides strong evidence that I2 emission rates between alga are highly variable, an observation that explains the wide range of previously reported emission rates.

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