Denitrification in intertidal sediments of a tropical estuary subject to increasing development pressures

Abstract Darwin Harbour is a working port and the most populated city in Northern Territory of Australia. This macrotidal estuary located wet–dry tropics Australia notwithstanding mounting development pressures region, largely unmodified. The prevailing oligotrophic condition estuarine waters suggest that biogeochemical cycling sediments remain active, buffering influence anthropogenic inputs. We tested hypothesis nutrient hotspots exist depositional low-velocity zones, with gradient high to low nitrogen processing from upper outer reaches estuary. A number factors were examined for their on effectiveness denitrification these putative key process driving removal, particular emphasis carbon-loading extremes tidal creeks, spatial gradients along seasonality. There significant differences rates between hypereutrophic/eutrophic creeks receive largest proportion treated sewage loads region mesotrophic/oligotrophic comparatively undisturbed. Net benthic fluxes dinitrogen efflux more than an order magnitude higher lower, respectively, degraded (hypereutrophic/eutrophic) creek systems where efficiency (DE%) was < 40%. Denitrification (Dinitrogen efflux) (mesotrophic/oligotrophic) broader sites (~ 8 mmol N m −2 day −1 ) remained > 65%, particularly during wet season. On whole-of-estuary basis, conjunction mechanisms such as burial could feasibly make substantial impact, abating Although considerable variability encountered, across seasons, elevated zones not convincing. More influential are potential ‘reactors’ but capacity can be by overloading nutrients.