Nitrogen availability facilitates phosphorus acquisition by bloom-forming cyanobacteria.

Area of Science:

• Environmental Science
• Limnology
• Microbiology

Background:

• Cyanobacterial blooms pose a significant threat to freshwater ecosystems.
• Understanding the physiological triggers of these blooms is key for prediction and management.
• Cyanobacteria growth is typically limited by nitrogen (N) or phosphorus (P) availability.

Purpose of the Study:

• To investigate how nitrogen (N) availability affects the phosphate (P) uptake affinity and activity in N-deficient, bloom-forming cyanobacteria.
• To determine the physiological response of cyanobacteria to episodic nutrient inputs.

Main Methods:

• Lake samples dominated by filamentous cyanobacteria were used.
• Samples were pre-incubated with and without nitrate addition.
• Phosphate uptake kinetics, including affinity and activity, were measured using [32P] phosphate pulses and analyzed with a flow-force model.

Main Results:

• Nitrate pre-incubation for 24 hours significantly increased cyanobacterial phosphate uptake affinity (to nanomolar [Pe]A levels) and activity (25-fold).
• This enhanced phosphate uptake was directly linked to cyanobacterial growth.
• The findings demonstrate that alleviating nitrogen deficiency activates phosphate uptake systems in non-N2-fixing cyanobacteria.

Conclusions:

• Nitrogen inputs stimulate phosphate uptake systems in cyanobacteria, promoting growth and bloom formation.
• Reducing dissolved inorganic nitrogen levels in lakes is essential to decrease cyanobacterial phosphate uptake capabilities.
• This highlights the importance of managing nitrogen pollution for controlling harmful cyanobacterial blooms.