Activity Abundance and Diversity of Nitrifying A

Authors: J Michael Beman

Publish Date: 2013/10/01

Volume: 37, Issue: 6, Pages: 1343-1352

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Abstract

Fixed nitrogen N removal from estuaries via coupled nitrification–denitrification plays a significant role in the global N cycle and the biogeochemistry of individual estuaries Much of our understanding of these processes is drawn from temperate estuaries yet tropical and subtropical estuaries may respond differently to N inputs I tested the hypothesis that nitrification is limited within subtropical estuaries by comparing nitrification and denitrification potentials and the abundance of archaeal ammonia monooxygenase amoA and bacterial nitrite reductase nirS genes across five sites in Bahía del Tóbari Mexico Sampling was conducted when agricultural runoff supplied substantial quantities of N ca 20–80 μM ammonium yet nitrification was detected at a single site Denitrification was measured at four sites and three displayed nitrate uptake rather than net nitrification—indicating a N sink within these sediments Bacterial nirS genes uniformly outnumbered archaeal amoA genes 3 to 49fold and were more abundant in the northern part of the estuary Patterns of community similarity among different sites were also different for nirS and archaeal amoA similarities between sites based on nirS were often greater than for amoA and sites were more rarely statistically different from each other While amoA abundance was inversely related to temperature neither amoA nor nirS was correlated with nitrification or denitrification potentials My results are broadly consistent with known and proposed patterns of nitrification and denitrification in subtropical estuarine sediments including the idea that nitrification is limited within subtropical estuarine sedimentsWe thank C Francis for comments on an earlier version of this manuscript C Francis and P Matson for use of their laboratories S Alford for assistance with QPCR analyses P Jewett for performing nutrient analyses and assisting the nitrification and denitrification potential measurements E CruzColin and J DelgadoContreras for assistance with fieldwork and sampling M NieblasLopez and the pescadores of Bahía del Tóbari for boat access and G Asner and D Lobell for providing ALI imagery This work was supported by the US National Science Foundation Graduate Research Fellowship Program the US National Science Foundation Office of International Science and Engineering Americas Program Grant OISE0438396 the US National Science Foundation Chemical Oceanography Program OCE1034943 and the David and Lucile Packard Foundation to P Matson and collaborators

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