Quantifying photosynthetic rates of microphytobenthos using the triple isotope composition of dissolved oxygen

Abstract

Author Posting. © Association for the Sciences of Limnology and Oceanography, 2013. This article is posted here by permission of Association for the Sciences of Limnology and Oceanography for personal use, not for redistribution. The definitive version was published in Limnology and Oceanography: Methods 11 (2013): 360-373, doi:10.4319/lom.2013.11.360.Microphytobenthos are important mediators of nutrient and carbon fluxes in coastal environments. However, quantifying production rates by microphytobenthos is difficult, and existing methods necessitate perhaps erroneous assumptions that dark respiration equals light respiration. Here we present a new method for quantifying photosynthetic rates of microphytobenthos, i.e., gross primary production, by using the triple isotope composition of dissolved oxygen in benthic flux chambers. Because the triple oxygen isotope signature is sensitive to photosynthesis, but not to respiration, this method allows quantification of gross photosynthetic oxygen fluxes by microphytobenthos without assumptions about respiration. We present results from field experiments in Waquoit Bay, Massachusetts, that illustrate the method.We gratefully acknowledge funding for this work by the Coastal Ocean Institute of Woods Hole Oceanographic Institution and the National Science Foundation (OCE-82964400). EH was supported by a National Defense Science and Engineering Graduate Fellowship award