Author: Riley  Hale,  Graduate Research Assistant (University of Wisconsin-Madison)

Designation: 

Description:
Cyanobacteria, commonly known as “blue-green algae,” are a phylum of bacteria that produce toxic or otherwise bioactive peptides that can affect the brain, liver, and skin of humans and animals. Rapid growth of Cyanobacteria in water bodies—known as “blooms”—affect the health and recreation of many nutrient-rich lakes, including Lake Mendota (Madison, WI). However, little is known about the ecological reason for cyanotoxin production, and the definition of a bloom remains vague. Water quality managers and health officials often struggle to predict the behavior of toxic blooms because of their spatial and temporal variability. Samples were taken at a single point over six years as part of a long-term microbial observatory time series and from 20 points across Lake Mendota on a single day characterized by visible cyanobacterial growth. These samples were analyzed for toxin concentration using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) and for cyanobacterial community composition using 16S rRNA gene amplicon sequencing. We also collected continuous cross-lake environmental measurements using a sonde connected to the Fast Limnological Austomated Measurement (FLAMe) platform. We found that the concentration and compositional makeup of toxins remained relatively homogeneous throughout each year and spatially across the lake. However, this homogeneity is not evident in cyanobacterial community composition analysis, which reveals both cyanobacterial community dynamics within and across years and spatial differences between the whole-lake system dominated by Cyanobacteria taxa and the inlet of the Yahara River into the lake dominated by Chloroplasts (eukaryotic algae). This suggests that Lake Mendota is a distinct homogeneous toxic summer lake system that favors Cyanobacteria and cyanotoxin production. By studying the spatiotemporal distribution of Cyanobacteria and cyanotoxins, we found that the cyanobacterial community is spatially and temporally heterogeneous, whereas cyanotoxins are spatially and temporally homogeneous. This provides valuable information regarding the characterization of freshwater toxic cyanobacterial blooms which can be used by water quality managers to assess the toxicity of freshwater lakes.

Category: Scientific Program Abstract > Special Sessions > SS24 Aquatic microbial structure and function across spatiotemporal scales