Understanding sediment nutrient cycling in a hypersaline coastal lagoon using hydrogel-based passive sampling...

Area of Science:

• Environmental Science
• Aquatic Ecology
• Geochemistry

Background:

• The Coorong, South Australia, is a vital hypersaline lagoon facing environmental pressures.
• Limited knowledge exists on nutrient cycling and organic matter fate within this system.
• Understanding these processes is critical for effective ecosystem management.

Purpose of the Study:

• To investigate nutrient dynamics and sediment redox conditions in the Coorong.
• To assess the influence of environmental factors like salinity, macrophytes, and microphytobenthos on nutrient cycling.
• To provide insights for improving the Coorong's ecosystem health.

Main Methods:

• Applied diffusive equilibrium in thin films (DET) and diffusive gradient in thin films (DGT) techniques.
• Measured dissolved nutrients (ammonium, phosphate), ferrous iron, and sulfide in sediment porewaters.
• Examined concentration profiles under light and dark conditions across a salinity gradient.

Main Results:

• Deep South Lagoon sediments showed high ammonium, phosphate, and sulfide, indicating anoxic conditions.
• Shallow sediments exhibited variable nutrient concentrations influenced by Ruppia and microphytobenthos.
• Ruppia-colonized sites had significantly lower porewater ammonium, suggesting a mitigating effect.

Conclusions:

• Aquatic macrophyte presence, particularly Ruppia, can reduce nutrient accumulation in Coorong sediments.
• Enhancing macrophyte and macroinvertebrate biomass may improve sediment quality and nutrient cycling.
• Findings offer crucial data for managing the Coorong's ecological health.