『Abstract
　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 sub-tropical 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), N2) 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 N2 effluxes (denitrification; 48％). Denitrification rates in seagrass were higher than those previously measured in temperate regions, most likely due to greater availability of NH4⁺ 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.

Keywords: Benthic microalgae (BMA); Budgets; Denitrification; Dissolved organic nitrogen (DON); Habitats; Mangroves; Seagrass』

Introduction
Study area
Methods
　Water quality
　Biogeochemical process measurements
　N and P exchange between mangroves and open water
　Statistical analysis
　Nitrogen (N) and phosphorus (P) budgets
　　Spatial and temporal boundaries, units of mass, significant figures and errors
　　Diffuse, lateral catchment and atmospheric loads
　　Denitrification, N-fixation and net N2 loss
　　Nutrient burial, mangrove exchange, fisheries harvest and Broadwater exchange
　　Standing stocks and recycling
Results
　Water quality
　Sediment nitrogen (N) and phosphorus (P)
　Benthic nitrogen fluxes
　Dinitrogen gas (N2) fluxes and N-fixation
　Benthic phosphorus fluxes
　System wide annual estimates of benthic nitrogen and phosphorus fluxes
　Nitrogen and phosphorus budgets for the study area
Discussion
　Influence of benthic trophic status on nitrogen and phosphorus cycling
　Seagrass habitats
　Non-seagrass benthic habitats
　Budget uncertainty and balance
　Budget comparisons
Further work
Acknowledgements
References