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Marine Ecology Progress Series

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MEPS 478:57-70 (2013)  -  DOI:

Denitrification, anammox and nitrate reduction in sediments of the southern Great Barrier Reef lagoon

Dirk V. Erler*,1, Lindsay A. Trott2, Daniel M. Alongi2, Bradley D. Eyre1

1Centre for Coastal Biogeochemistry, School of Environmental Science and Management, Southern Cross University, Lismore NSW 2480, Australia.
2Australian Institute of Marine Science, PMB 3, Townsville MC QLD 4810, Australia

ABSTRACT: 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.

KEY WORDS: Great Barrier Reef · Anammox · Dissimilatory/assimilatory nitrate reduction to ammonia · Denitrification

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Cite this article as: Erler DV, Trott LA, Alongi DM, Eyre BD (2013) Denitrification, anammox and nitrate reduction in sediments of the southern Great Barrier Reef lagoon. Mar Ecol Prog Ser 478:57-70.

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