Fuchsman, CA and Devol, AH and Chase, Z and Reimers, CE and Hales, B, Benthic fluxes on the Oregon shelf, Estuarine, Coastal and Shelf Science, 163, (Part B) pp. 156-166. ISSN 0272-7714 (2015) [Refereed Article]
Benthic chamber incubations were performed in the mid-shelf region on the Oregon shelf in June and August 2009 to measure fluxes of oxygen, nutrients, and iron and their effect on water column chemistry. Chamber oxygen and nitrate fluxes were into the sediments while silicate, iron and ammonium fluxes were out of the sediments. Benthic fluxes were similar between the two months, except that dissolved iron fluxes were higher at some sites in August. Bottom waters were consistently hypoxic (43ľ64áμM O2) and had ammonium concentrations from 0 to 2.6áμM in the mid-shelf region. Given measured ammonium fluxes (0.2ľ1.4ámmolám−2ád−1), we used a simple stoichiometric model for a 10ám bottom boundary layer to calculate that benthic fluxes only contributed ∼16ľ41% of the bottom water ammonia. Benthic oxygen fluxes (−4.3 toá−12.5ámmoláO2ám−2ád−1) were responsible for ∼38ľ51% of oxygen drawdown in the benthic boundary layer. In both cases, the remainder may be attributed to water column respiration. Benthic iron and nitrate fluxes have opposite effects on productivity. Iron fluxes (0ľ71áμmolám−2ád−1, average: 5áμmolám−2ád−1) increased bottom water concentrations while nitrate was lost (−1.2 toá−2.9ámmolám−2ád−13NO−) due to denitrification. By supplying iron and consuming nitrogen, benthic diagenetic processes reinforce an iron-replete, nitrate-limited coastal ecosystem.