A comparison of nutrient uptake efficiency and growth rate between different macrophyte growth forms

Area of Science:

• Ecology
• Aquatic Botany
• Biogeochemistry

Background:

• Aquatic macrophytes are vital for stream ecosystem functioning, particularly nutrient retention.
• Understanding nutrient uptake kinetics of different macrophyte growth forms is crucial for stream management.

Purpose of the Study:

• To quantify and compare nutrient (nitrogen and phosphorus) uptake kinetics in submerged and amphibious macrophyte growth forms.
• To investigate the relationship between relative growth rate and nutrient uptake parameters.
• To assess seasonal variations in nutrient uptake kinetics.

Main Methods:

• Microcosm experiment comparing 19 freshwater macrophyte species (12 submerged, 7 amphibious).
• Measurement of inorganic nitrogen (NH4-N, NO3-N) and phosphorus (PO4-P) uptake kinetic parameters (Vmax, Cmin).
• Seasonal monitoring of nutrient uptake kinetics in a subset of species.

Main Results:

• Submerged plants exhibited higher ammonium (NH4-N) uptake, while amphibious plants showed higher nitrate (NO3-N) uptake.
• Phosphorus (PO4-P) uptake kinetics did not differ significantly between growth forms.
• Significant seasonal variations in Vmax were observed, with highest uptake rates in summer for both growth forms.

Conclusions:

• Nutrient uptake kinetics vary between submerged and amphibious macrophytes and across seasons.
• Increased functional diversity of macrophytes enhances annual nutrient uptake in streams.
• Stream restoration should promote habitats for both submerged and amphibious species to maximize nutrient retention.