Cyanobacterial bloom intensities determine planktonic eukaryote community structure and stability

Area of Science:

• Freshwater ecology
• Limnology
• Eukaryotic microbial ecology

Background:

• Cyanobacterial blooms are common in global lakes and reservoirs, with variable intensity impacting freshwater ecosystems.
• The influence of cyanobacterial blooms on planktonic eukaryotic communities and their ecological functions remains poorly understood.
• Planktonic eukaryotes are crucial for freshwater ecosystem structure and function.

Purpose of the Study:

• To investigate the effects of varying cyanobacterial bloom intensities on eukaryotic plankton community dynamics in Hongze Lake.
• To understand how spatial heterogeneity of cyanobacterial blooms influences planktonic eukaryotes.
• To reveal the impact of bloom levels on eukaryotic plankton diversity, richness, evenness, and community composition.

Main Methods:

• Studied eukaryotic plankton communities across a gradient of cyanobacterial bloom levels in Hongze Lake.
• Analyzed changes in diversity, richness, and evenness of eukaryotic plankton.
• Assessed shifts in the relative abundance of major eukaryotic groups (Metazoa, Ochrophyta, Chloroplastida, Cryptomonadales, Ciliophora).
• Evaluated the stability of planktonic eukaryotic food webs using linkage density.

Main Results:

• Low cyanobacterial bloom levels did not affect eukaryotic plankton diversity, richness, or evenness.
• High cyanobacterial bloom levels significantly decreased eukaryotic plankton diversity, richness, and evenness.
• Low bloom levels led to a decline in Metazoa and an increase in eukaryotic phytoplankton and Ciliophora.
• High bloom levels showed opposite community composition changes compared to low bloom levels.
• Planktonic eukaryotic network stability (linkage density) was lower under high bloom conditions.

Conclusions:

• Cyanobacterial blooms at high intensity have a significant negative impact on microeukaryote communities in freshwater ecosystems.
• Maintaining low levels of cyanobacterial blooms is crucial to preserve the diversity and stability of planktonic eukaryotic communities.
• Findings highlight the importance of bloom management strategies to mitigate adverse effects on lake ecosystems.