Bacterial communities in acidic and circumneutral streams.

Area of Science:

• Environmental microbiology
• Aquatic ecology
• Acidification effects

Background:

• Stream acidification poses a threat to aquatic ecosystems.
• Understanding microbial community responses is crucial for assessing ecosystem health.
• Epilithic bacteria on rock surfaces are a key component of stream communities.

Purpose of the Study:

• To investigate the relationship between pH and bacterial abundance and activity in streams.
• To determine which bacterial communities are most affected by acidification.
• To assess the impact of low pH on microbial biomass and production.

Main Methods:

• Quantified microbial biomass using Adenosine Triphosphate (ATP) levels.
• Measured bacterial production via tritiated thymidine incorporation into DNA.
• Analyzed bacterioplankton concentrations and their association with seston.
• Examined bacterial numbers and production in sediments in relation to organic content.

Main Results:

• Epilithic bacterial biomass and production were significantly correlated with pH, decreasing at lower pH levels.
• Bacterioplankton concentrations were not correlated with pH but with seston concentrations.
• Sediment bacteria abundance and production correlated with organic content, not overlying water pH.
• Epilithic communities showed the most significant negative impact from acidification.

Conclusions:

• Acidification primarily affects the epilithic bacterial community due to direct exposure in unbuffered environments.
• Bacterioplankton and sediment bacteria are less sensitive to pH changes compared to epilithic bacteria.
• The study highlights the vulnerability of rock-surface microbial communities to environmental stressors like acidification.