Inorganic nutrients, bacteria, and the microbial loop

Area of Science:

• Marine microbial ecology
• Ocean biogeochemistry
• Aquatic microbiology

Background:

• Traditionally, planktonic bacteria were viewed primarily as remineralizers of nutrients in aquatic ecosystems.
• Recent findings indicate that bacteria can actively acquire dissolved inorganic nutrients, altering this paradigm.
• This bacterial nutrient uptake influences competition dynamics between bacteria and phytoplankton.

Purpose of the Study:

• To re-evaluate the role of planktonic bacteria in nutrient cycling within marine communities.
• To understand the implications of bacterial nutrient acquisition on microbial loop functioning.
• To explore the conditions and locations where bacterial nutrient uptake is significant.

Main Methods:

• Analysis of nutrient uptake rates in natural planktonic bacterial assemblages.
• Investigating the competition for dissolved inorganic nitrogen and phosphorus between bacteria and phytoplankton.
• Assessing the role of bacterivorous protozoa in nutrient remineralization.

Main Results:

• Planktonic bacteria acquire a substantial portion of their nitrogen and phosphorus from dissolved inorganic pools.
• Bacterial nutrient uptake positions bacteria as competitors with phytoplankton for growth-limiting nutrients.
• Bacterivorous protozoa emerge as key players in remineralizing these nutrients within the microbial loop.

Conclusions:

• The traditional view of bacteria solely as nutrient remineralizers is challenged by their active nutrient uptake.
• Bacterial competition for inorganic nutrients with phytoplankton is a significant ecological interaction.
• Understanding bacterial nutrient utilization is crucial for accurate modeling of marine biogeochemical cycles.