Catchment land use predicts benthic vegetation in small estuaries

Area of Science:

• Estuarine ecology
• Environmental science
• Coastal management

Background:

• Estuaries are increasingly eutrophic due to anthropogenic catchment activities.
• Nutrient loads are commonly used to assess eutrophication risk but are costly and time-intensive to collect.
• Alternative, cost-effective predictors are needed for estuary management.

Purpose of the Study:

• To identify reliable predictors of estuarine vegetation composition, specifically macroalgae dominance.
• To assess the relationship between catchment land use and estuarine ecological state.
• To establish thresholds for land use changes impacting estuaries.

Main Methods:

• Compared four potential predictors: percent fertilized catchment land, dissolved inorganic nitrogen loads, catchment-to-estuary area ratio, and flushing time.
• Analyzed data from 14 estuaries in south-eastern Australia.
• Determined the proportion of macroalgae to total vegetation in each estuary.

Main Results:

• The percent of fertilized land within a catchment was the strongest predictor of macroalgae proportion.
• A significant transition to macroalgae dominance occurred when fertilized land exceeded 24% of the catchment.
• Catchment land use emerged as a key driver of estuarine vegetation dynamics.

Conclusions:

• Estuarine sensitivity to catchment land use is high, particularly concerning agricultural fertilization.
• The percentage of fertilized land in a catchment serves as a practical and effective indicator for eutrophication risk.
• Management strategies should focus on limiting agricultural intensification in estuarine catchments to prevent ecological shifts.