Beyond Microcystins: A New Look at Cyanotoxins in Lake Erie
Cyanobacterial harmful algal blooms (cyanoHABs) in Lake Erie’s western basin have long been associated with microcystins, a well-known group of liver toxins. However, new research shows that these blooms are far more chemically diverse than previously thought. A seven-year study using advanced chemical and genetic tools reveals that cyanobacteria produce a succession of different chemical signatures related to toxins throughout the bloom season, each with distinct environmental triggers and potential health impacts.
More Than Just Microcystins
For years, scientists and water managers have focused on microcystins when evaluating the risks of cyanobacterial harmful algal blooms (cyanoHABs). However, new analytical tools that reveal both the chemistry and genetics of these blooms are expanding our understanding. Using cutting-edge methods, researchers from U.S. Geological Survey (USGS), National Oceanic and Atmospheric Administration (NOAA), and University of Michigan Cooperative Institute for Great Lakes Research and Geomicrobiology Lab, discovered that Lake Erie’s algal blooms produce a wide variety of cyanopeptides toxins, not just microcystins. Among them are lesser-known compounds like anabaenopeptins, aeruginosins, and aerucyclamides. These toxins are not as well understood, but they may still pose significant risks to ecosystems and human health.
This finding challenges the assumption that a decline in microcystins signals a reduction in bloom toxicity. In reality, the bloom may be transitioning to produce different cyanotoxins—ones that are not routinely monitored and for which no regulatory guidelines currently exist.
Cyanopeptides
Cyanopeptides are natural chemicals made by certain types of algae called cyanobacteria— the same organisms that cause harmful algal blooms. People often hear about microcystins, which are one well‑known toxin, but cyanobacteria produce many other small, biologically active molecules. These are collectively called cyanopeptides. Some of them may be harmful, some may have no known effects, and many are still being discovered. What makes them important is that they can appear in the water during algal blooms, sometimes at the same time as better‑known toxins. Because they can vary throughout the bloom season, they may influence the overall health risks of a bloom
Three Toxin Phases, One Bloom
To understand how cyanopeptides changes over time, researchers analyzed data from 2016 to 2022 using metagenomics (to study microbial DNA), and metabolomics (to measure chemical compounds). They tracked shifts in cyanobacterial species, toxin-producing genes (known as biosynthetic gene clusters, or BGCs), and the actual toxins present.
Microcystis tends to dominate early in the bloom season when water is warmer, and nitrogen levels are high. Later in the season, as temperatures drop, Dolichospermum becomes more prevalent. In this shift cyanopeptides also shift in distinct phases:
Phase 1: Microcystins – well-known liver toxin in mammals, other potential effects are less understood.
Phase 2: Anabaenopeptins and aeruginosins – protease inhibitors that may affect aquatic ecosystems and human health.
Phase 3: Aerucyclamides - compounds known to be toxic to a U.S. based freshwater crustacean (Thamnocephalus platyurus) known as the Beavertail Fairy Shrimp, a filter feeder that is responsible for improving water quality. Potential human toxicity is largely unknown.
These cyanopeptides phases were linked to changes in environmental conditions and biological interactions. For example, later phases coincided with more microbially processed organic nitrogen and fewer detectable grazers (organisms that feed on cyanobacteria), based on environmental DNA (eDNA) analysis.
The study highlights that cyanobacterial blooms involve a complex succession of cyanopeptides types, not just microcystins, and that these patterns are influenced by both bottom-up factors (like nutrients and temperature) and top-down pressures (like grazing).
Rethinking Cyanotoxin Risk
This discovery changes the way we think about cyanotoxin risk. If we only test microcystins, we might miss other cyanopeptides that are present,and potentially dangerous. This broader understanding could improve monitoring and management of freshwater blooms. The study shows that:
- Cyanopeptides can still be present even when microcystins are not.
- Current monitoring programs may underestimate risk by focusing on a single toxin class.
- New exposure thresholds are needed for other cyanotoxins like anabaenopeptins and aerucyclamides, which currently lack regulatory guidelines.
A Call for Broader Monitoring
The findings highlight the importance of non-targeted chemical analysis and genomic tools in environmental monitoring. These methods allow scientists to detect a wider range of toxins, even those for which no commercial test kits exist.
By combining LC/HRMS with biosynthetic gene cluster analysis, researchers can not only detect toxins but also begin to understand the environmental conditions that trigger their production. This opens the door to early warning systems and better prevention strategies.
This study has been supported by the U.S. Geological Survey Ecosystems Mission Area, through the Environmental Health Program (Contaminant Biology and Toxic Substances Hydrology); U.S. Environmental Protection Agency Great Lakes Restoration Initiative; National Institute of Environmental Health Sciences; National Science Foundation, and the NOAA ‘Omics Program.
Cyanobacterial harmful algal blooms (cyanoHABs) in Lake Erie’s western basin have long been associated with microcystins, a well-known group of liver toxins. However, new research shows that these blooms are far more chemically diverse than previously thought. A seven-year study using advanced chemical and genetic tools reveals that cyanobacteria produce a succession of different chemical signatures related to toxins throughout the bloom season, each with distinct environmental triggers and potential health impacts.
More Than Just Microcystins
For years, scientists and water managers have focused on microcystins when evaluating the risks of cyanobacterial harmful algal blooms (cyanoHABs). However, new analytical tools that reveal both the chemistry and genetics of these blooms are expanding our understanding. Using cutting-edge methods, researchers from U.S. Geological Survey (USGS), National Oceanic and Atmospheric Administration (NOAA), and University of Michigan Cooperative Institute for Great Lakes Research and Geomicrobiology Lab, discovered that Lake Erie’s algal blooms produce a wide variety of cyanopeptides toxins, not just microcystins. Among them are lesser-known compounds like anabaenopeptins, aeruginosins, and aerucyclamides. These toxins are not as well understood, but they may still pose significant risks to ecosystems and human health.
This finding challenges the assumption that a decline in microcystins signals a reduction in bloom toxicity. In reality, the bloom may be transitioning to produce different cyanotoxins—ones that are not routinely monitored and for which no regulatory guidelines currently exist.
Cyanopeptides
Cyanopeptides are natural chemicals made by certain types of algae called cyanobacteria— the same organisms that cause harmful algal blooms. People often hear about microcystins, which are one well‑known toxin, but cyanobacteria produce many other small, biologically active molecules. These are collectively called cyanopeptides. Some of them may be harmful, some may have no known effects, and many are still being discovered. What makes them important is that they can appear in the water during algal blooms, sometimes at the same time as better‑known toxins. Because they can vary throughout the bloom season, they may influence the overall health risks of a bloom
Three Toxin Phases, One Bloom
To understand how cyanopeptides changes over time, researchers analyzed data from 2016 to 2022 using metagenomics (to study microbial DNA), and metabolomics (to measure chemical compounds). They tracked shifts in cyanobacterial species, toxin-producing genes (known as biosynthetic gene clusters, or BGCs), and the actual toxins present.
Microcystis tends to dominate early in the bloom season when water is warmer, and nitrogen levels are high. Later in the season, as temperatures drop, Dolichospermum becomes more prevalent. In this shift cyanopeptides also shift in distinct phases:
Phase 1: Microcystins – well-known liver toxin in mammals, other potential effects are less understood.
Phase 2: Anabaenopeptins and aeruginosins – protease inhibitors that may affect aquatic ecosystems and human health.
Phase 3: Aerucyclamides - compounds known to be toxic to a U.S. based freshwater crustacean (Thamnocephalus platyurus) known as the Beavertail Fairy Shrimp, a filter feeder that is responsible for improving water quality. Potential human toxicity is largely unknown.
These cyanopeptides phases were linked to changes in environmental conditions and biological interactions. For example, later phases coincided with more microbially processed organic nitrogen and fewer detectable grazers (organisms that feed on cyanobacteria), based on environmental DNA (eDNA) analysis.
The study highlights that cyanobacterial blooms involve a complex succession of cyanopeptides types, not just microcystins, and that these patterns are influenced by both bottom-up factors (like nutrients and temperature) and top-down pressures (like grazing).
Rethinking Cyanotoxin Risk
This discovery changes the way we think about cyanotoxin risk. If we only test microcystins, we might miss other cyanopeptides that are present,and potentially dangerous. This broader understanding could improve monitoring and management of freshwater blooms. The study shows that:
- Cyanopeptides can still be present even when microcystins are not.
- Current monitoring programs may underestimate risk by focusing on a single toxin class.
- New exposure thresholds are needed for other cyanotoxins like anabaenopeptins and aerucyclamides, which currently lack regulatory guidelines.
A Call for Broader Monitoring
The findings highlight the importance of non-targeted chemical analysis and genomic tools in environmental monitoring. These methods allow scientists to detect a wider range of toxins, even those for which no commercial test kits exist.
By combining LC/HRMS with biosynthetic gene cluster analysis, researchers can not only detect toxins but also begin to understand the environmental conditions that trigger their production. This opens the door to early warning systems and better prevention strategies.
This study has been supported by the U.S. Geological Survey Ecosystems Mission Area, through the Environmental Health Program (Contaminant Biology and Toxic Substances Hydrology); U.S. Environmental Protection Agency Great Lakes Restoration Initiative; National Institute of Environmental Health Sciences; National Science Foundation, and the NOAA ‘Omics Program.