Denitrification, anammox and nitrate reduction in the sediments of the Southern Great Barrier Reef Lagoon
Erler, DV, Trott, LA, Alongi, DM & Eyre, BD 2013, 'Denitrification, anammox and nitrate reduction in sediments of the southern Great Barrier Reef lagoon', Marine Ecology Progress Series, vol. 478, pp. 57-70.
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We provide the first reported estimates of anammox activity in tropical continental shelf sediments (southern section of the Great Barrier Reef lagoon; GBRL). The measured contribution of anammox to total N2 production was up to 70% but restricted to only 1 of the 4 (2 inshore and 2 offshore) sites assayed. Sediment characteristics (contents of total organic carbon [TOC] and manganese [Mn], C:N ratio) at this site appeared to favour anammox activity and the estimated maximum rate was 4.9 µmol m-2 h-1. Anammox bacteria may be a significant contributor to N2 production along the coastal zone of the GBRL. The availability of labile (low C:N) TOC seemed to drive denitrification to completion in the offshore sediments. However, rates of NO3- reduction to NH4+ at the offshore sites were comparable to or higher than denitrification rates. It was unclear whether dissimilatory or assimilatory processes were responsible for the observed reduction of NO3- to NH4+ at the offshore sites. At the 2 inshore sites, NO3- reduction to NH4+ was a larger sink for NO3- than denitrification. Anammox does exist in the tropical continental shelf sediments of the GBRL and should be studied further to determine its role in larger scale N cycling. The roles of assimilatory and dissimilatory nitrate reduction to ammonium also need to be assessed within the GBRL.