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Importance of habitat diversity in benthic metabolism changes over land-use gradients: evidence from three sub-tropical estuaries

Jian-Jhih Chen*, Naomi S. Wells, Dirk V. Erler, Bradley D. Eyre

*Corresponding author:

ABSTRACT: Seasonal rates of benthic gross primary production (GPP), net primary production (NPP) and respiration (R) were measured, and whole-system carbon budgets were constructed, in three sub-tropical estuaries with different catchment land-use intensities, to better understand how land-use change influences benthic metabolism. The annual benthic net ecosystem metabolism indicates that systems become more heterotrophic with increasing land-use intensity. This was due to a combination of an increase in the area of the un-vegetated habitats, and the un-vegetated habitats becoming more heterotrophic, with increasing land-use intensity. Whole-system net ecosystem metabolism is closely linked to the benthic net ecosystem metabolism, highlighting the important control of benthic metabolism on whole-system metabolism in shallow coastal systems. Carbon mass balances show whole-system net metabolism also shifted from net autotrophic to net heterotrophic, with a concomitant switch from CO2 uptake to emission, with increasing land-use intensity. Our findings demonstrate that land-use changes shift whole-estuary metabolism by altering both habitat distribution and within-habitat metabolism rates.