Is a Central Sediment Sample Sufficient? Exploring Spatial and Temporal Microbial Diversity in a Small Lake
Barbara Weisbrod1, Susanna A Wood2, Konstanze Steiner2
1Human and Environmental Toxicology, Department of Biology, University of Konstanz, Universitätsstrasse 10, 78457 Konstanz, Germany.
Toxins
|September 12, 2020
Summary
Paleolimnology reveals Lake Rotorua
Area of Science:
- Environmental Science
- Microbiology
- Geology
Background:
- Paleolimnological studies analyze lake sediment cores for long-term ecological changes, including harmful cyanobacterial blooms.
- Limited data exists on small-scale microbial community variability in lake sediments, challenging the representativeness of single-core studies.
Purpose of the Study:
- To investigate the spatial variability of microbial communities in Lake Rotorua's surface sediments.
- To assess the presence of toxin-producing *Microcystis* and associated genes in lake sediments.
- To understand the historical occurrence of cyanobacterial blooms in relation to sediment layers and geological events.
Main Methods:
- Collected surface sediments (top 0.5 cm) from 12 sites and two sediment cores from Lake Rotorua.
- Utilized 16S rRNA metabarcoding to analyze bacterial communities and specific genes (*Microcystis* 16S rRNA, *mcyE*) for toxin-producing cyanobacteria.
- Quantified microcystins (MCs) and dated sediments using radionuclide measurements (210Pb, 137Cs).
Main Results:
- Bacterial communities in surface sediments showed significant spatial variation, yet most sequences were shared across sites.
- No *Microcystis* specific 16S rRNA, *mcyE* gene, or microcystins were detected in surface sediments.
- These cyanobacteria and toxins were found deeper in sediment cores, dating back to the 1950s, with disturbed sediment profiles due to earthquakes.
Conclusions:
- A single sediment core can effectively represent the dominant microbial communities in a lake.
- Toxin-producing *Microcystis* blooms are a recent phenomenon in Lake Rotorua, likely influenced by recent geological events.
- The absence of *Microcystis* in surface sediments may be linked to the Kaikoura earthquake prior to sampling.
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