Macrophyte coverage drives microbial community structure and interactions in a shallow sub-tropical lake

Area of Science:

• Ecology
• Aquatic Botany
• Microbial Ecology

Background:

• Shallow lakes rely on macrophytes for trophic regulation and habitat creation.
• Invasive submersed macrophytes, such as hydrilla, dominate many Florida lakes and require intensive management.
• Macrophyte presence significantly influences water chemistry and microbial community structure.

Purpose of the Study:

• To investigate the effects of herbicidal and mechanical control treatments on invasive hydrilla in a large Florida lake.
• To assess the subsequent impacts on water chemistry and microbial communities (bacteria and protists).
• To understand the ecological consequences of managing invasive aquatic plants.

Main Methods:

• Large-scale (40 ha) herbicidal and mechanical control treatments were applied to Lake Tohopekaliga.
• Macrophyte coverage, water chemistry (chlorophyll a, turbidity), and microbial community diversity were monitored.
• Changes in bacterial and protist communities were analyzed in relation to macrophyte decline.

Main Results:

• Treatments significantly reduced macrophyte coverage, leading to increased chlorophyll a and turbidity.
• A decrease in macrophyte coverage resulted in lower microbial community diversity.
• An increase in cyanobacteria relative abundance was observed with declining macrophyte coverage.

Conclusions:

• Macrophyte control impacts lake water chemistry and microbial ecology, with both positive and negative consequences.
• While initial plant reduction occurred, coverage increased over time, indicating treatment limitations.
• The rise in cyanobacteria suggests a risk of harmful algal blooms following sustained macrophyte decline.