10.6084/m9.figshare.12032598.v1 John M. Quinn John M. Quinn J. Christopher Rutherford J. Christopher Rutherford Sherry J. Schiff Sherry J. Schiff Nutrient attenuation in a shallow, gravel-bed river. I. <i>In-situ</i> chamber experiments Taylor & Francis Group 2020 Nutrients nitrogen phosphorus periphyton attenuation photosynthesis 2020-03-25 21:58:23 Journal contribution https://tandf.figshare.com/articles/journal_contribution/Nutrient_attenuation_in_a_shallow_gravel-bed_river_I_i_In-situ_i_chamber_experiments/12032598 <p>Dissolved nutrient uptake and metabolism by periphyton in a central North Island gravel-bed river were investigated using recirculating <i>in-situ</i> chambers. Dissolved inorganic nitrogen (DIN) uptake was correlated with photosynthesis and chlorophyll but N uptake and carbon fixation were partly de-coupled indicating storage. Dissolved reactive phosphorus (DRP) uptake was only weakly correlated with photosynthesis. Diatoms and green algae relied on DRP in the water, but Cyanobacteria met part of their P needs from storage. Dissolved organic nutrients were excreted in both light and dark incubations, with approximately 50% of DIN uptake during photosynthesis excreted as DON. To simulate diurnal variations in nutrients, oxygen and pH existing computer models need to de-couple photosynthesis from nutrient uptake, allow for variable stoichiometry and better quantify recycling of organic nutrients.</p>