Primary production and nutrients in a tropical macrotidal estuary, Darwin Harbour, Australia

Burford, Michele A.; Alongi, Daniel M.; McKinnon, A. David; Trott, Lindsay

doi:10.1016/j.ecss.2008.04.018

Cited by 79 publications

(67 citation statements)

References 27 publications

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“…This contrasts with some large temperate systems where diffuse sources typically make up a larger proportion of the loads (e.g. Boynton et al 1995;Nixon et al 1995) but is similar to other temperate (Engqvist 1996;Mackas and Harrison 1997), subtropical (Eyre and France 1997), and tropical (Burford et al 2008) coastal systems. Differences in the importance of ocean exchange to the N and P budgets is most likely due to the morphology of the coastal system with the ratio of catchment area: water volume an important driver of the relative importance of ocean input.…”

Section: Budget Comparisonsmentioning

confidence: 82%

Denitrification, N-fixation and nitrogen and phosphorus fluxes in different benthic habitats and their contribution to the nitrogen and phosphorus budgets of a shallow oligotrophic sub-tropical coastal system (southern Moreton Bay, Australia)

et al. 2010

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Denitrification, N-fixation, and dissolved inorganic and organic fluxes of nitrogen (N) and phosphorus (P) were measured in each of the major benthic habitat types of a shallow oligotrophic subtropical coastal system, and N and P budgets were constructed to quantify the importance of each habitat to N and P cycling in the whole ecosystem. The productivity/respiration (p/r) ratio (trophic status) of the habitats was an important control on the rates, direction (uptake, efflux) and composition (dissolved inorganic N (DIN), dissolved organic N (DON), N 2 ) of N fluxes across the sediment-water interface, with an efflux below p/r = 1.5 and an uptake above p/ r = 1.5. The Zostera Seagrass Community was the most important habitat for N loss via net N 2 effluxes (denitrification; 48%). Denitrification rates in seagrass were higher than those previously measured in temperate regions, most likely due to greater availability of NH 4? for coupled nitrification-denitrification. Yabby Shoals (sub-tidal shoals inhabited by burrowing shrimp, Trypaea australiensis) accounted for the second largest loss of N via denitrification, the largest recycling of DIN and dissolved inorganic P (DIP; statistically significant only during the dark in summer) across the sediment-water interface and the second largest uptake of DON (statistically significant only in summer). This study highlighted that shallow subtropical coastal systems have a complex mosaic of benthic habitats and that some less 'iconic' habitats (i.e. non-seagrass) also make an important functional contribution that controls the flow of N and P through the whole ecosystem.

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Section: Budget Comparisonsmentioning

confidence: 82%

Denitrification, N-fixation and nitrogen and phosphorus fluxes in different benthic habitats and their contribution to the nitrogen and phosphorus budgets of a shallow oligotrophic sub-tropical coastal system (southern Moreton Bay, Australia)

et al. 2010

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“…Impacts on water quality in Darwin Harbour as a result of seasonal and point source nutrient inputs have been reported previously (e.g. McKinnon et al 2006;Burford et al 2008) and fish kills have occurred in tidal creeks receiving sewage effluent. There is potential for more severe impacts on water quality and overall ecological health in the future due to increasing population and land development.…”

Section: Introductionmentioning

confidence: 88%

“…The majority of nutrients that enter the harbour are imported from the ocean and are typically in the particulate or organic form (Burford et al 2008). Nutrients also enter the harbour from the surrounding catchment and include both diffuse sources, such as urban and rural runoff, and point sources such as treated sewage effluent which is discharged into both the main body of the harbour and several tidal creeks on the fringes.…”

Section: Study Areamentioning

confidence: 99%

Effect of nutrient loading on biogeochemical processes in tropical tidal creeks

et al. 2011

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The effect of increased nutrient loads on biogeochemical processes in macrotidal, mangrovelined creeks was studied in tropical Darwin Harbour, Australia. This study uses an integrative approach involving multiple benthic and pelagic processes as measures of ecosystem function, and provides a comparison of these processes in three tidal creeks receiving different loads of treated sewage effluent. There were significant differences in process rates between Buffalo Creek (BC) (hypereutrophic), which receives the largest sewage loads; Myrmidon Creek (MC) (oligotrophic-mesotrophic) which receives smaller sewage inputs; and Reference Creek (RC) (oligotrophic) which is comparatively pristine.Benthic nutrient fluxes and denitrification were more than an order of magnitude higher and lower, respectively, in BC and denitrification efficiency (DE) was \10%. Pelagic primary production rates were also much higher in BC but respiration exceeded primary production resulting in severe drawdown of O 2 concentrations at night. Hypoxic conditions released oxide-bound phosphorus and inhibited coupled nitrification-denitrification, enhancing benthic nitrogen and phosphorus fluxes, leading to a build-up of excess nutrients in the water column. Poor water quality in BC was exacerbated by limited tidal flushing imposed by a narrow meandering channel and sandbar across the mouth. In contrast to BC, the effect of the sewage load in MC was confined to the water column, and the impact was temporary and highly localized. This is attributed to the effective flushing of the sewage plume with each tidal cycle. Denitrification rates in MC and RC were high (up to 6.83 mmol N m -2 day -1 ) and DE was approximately 90%. This study has identified denitrification, benthic nutrient fluxes and pelagic primary production as the biogeochemical processes most affected by nutrient loading in these tidal creek systems. Physical process play a key role and the combined influence of nutrient loading and poor tidal flushing can have serious consequences for ecosystem functioning.

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“…Darwin Harbour, Australia: Burford et al 2008;Hinchinbrook Channel, Australia: Alongi et al 1998;Sawi Bay, Thailand: Alongi et al 2000) mangrove production in southern Moreton Bay was the largest source of primary production. But annual estimates of gross primary production, respiration and net ecosystem metabolism were much lower than in the tropical systems, even with similar percentage coverage of mangroves (Table 5), probably reflecting the reduced sub-tropical growing climate.…”

Section: Whole System Budget Comparisonsmentioning

confidence: 97%

Metabolism of different benthic habitats and their contribution to the carbon budget of a shallow oligotrophic sub-tropical coastal system (southern Moreton Bay, Australia)

et al. 2010

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The major benthic habitats in a shallow oligotrophic sub-tropical coastal system were mapped, benthic productivity and respiration were measured seasonally (summer, winter) in each open water habitat, and an annual carbon budget was constructed using measured, modelled and literature fluxes to estimate the functional importance of each major benthic habitat to the whole ecosystem. Stable Zostera Seagrass Communities covered 16% of the open water system but made little contribution to whole system metabolism. In contrast, ephemeral Halophila Seagrass Communities covered only 8% of the open water system but contributed 46% of the net productivity (p). The less 'iconic' Inter-and Sub-tidal Pimpama Shoals also only had a small areal extent (10%) but accounted for 50% of the net benthic production. Similarly, Yabby Shoals only covered 27% of the open water system but accounted for 89% of the net respiration (r). Budget estimates suggest that lateral import of organic matter, most likely tidally transported phytoplankton trapped in seagrass beds, across the Broadwater boundaries was required to balance the carbon budget if any reasonable estimate of burial was invoked. However, budget errors make it difficult to distinguish this import from zero. This study demonstrated that shallow subtropical coastal systems have a complex mosaic of benthic habitats, and that some of the less 'iconic' habitats (i.e. non-seagrass, non-mangrove) also make an important functional contribution that controls the flow of energy and nutrients through the whole ecosystem and determines the net ecosystem metabolism and possible exchanges with adjacent systems.

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Primary production and nutrients in a tropical macrotidal estuary, Darwin Harbour, Australia

Cited by 79 publications

References 27 publications

Denitrification, N-fixation and nitrogen and phosphorus fluxes in different benthic habitats and their contribution to the nitrogen and phosphorus budgets of a shallow oligotrophic sub-tropical coastal system (southern Moreton Bay, Australia)

Denitrification, N-fixation and nitrogen and phosphorus fluxes in different benthic habitats and their contribution to the nitrogen and phosphorus budgets of a shallow oligotrophic sub-tropical coastal system (southern Moreton Bay, Australia)

Effect of nutrient loading on biogeochemical processes in tropical tidal creeks

Metabolism of different benthic habitats and their contribution to the carbon budget of a shallow oligotrophic sub-tropical coastal system (southern Moreton Bay, Australia)

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