Cyanobacterial harmful algal blooms (cHABs) are becoming more widespread due to climate change, affecting freshwater bodies worldwide. These blooms produce toxins like microcystins (MCs) and nodularins (NODs), which pose serious health risks to humans and animals. Additionally, these cyanobacteria blooms can also pose a threat to the ecosystem in which it is located. While cyanobacteria are an important part of the aquatic food web as it is able to fix nitrogen from the atmosphere and make it usable for the aquatic ecosystem, an excess amount can cause it to become a toxic bloom. This excessive amount of algae can low to no oxygen in the water as well as acidification. 

Microcystin-LR fix

Microcystin-LR Structure

Microcystins and Nodularins are a diverse group of cyclic heptapeptides produced by cyanobacteria in slow-moving bodies of water like lakes and ponds. Both Microsytins and Nodularins have similar chemical properties and thus are generally studied together. The two toxins are also able to inhibit protein phosphatase 1 and 2A. Microcystin-Leucine-Arginine (MC-LR) is the most toxic variant of this family and a known inhibitor of multiple human protein phosphatases. Exposure has been implicated in liver, reproductive, immune, and developmental toxicity as well as in increasing one’s risk of various forms of cancer. This may be in part due to the fact that recent findings indicate MC-LR causes apoptosis, altered functions of immune cells, and ultimately decreased cell viability. Since MC-LR is one of the most common and potent forms of toxic cyanobacterial toxins, it is regulated by the World Health Organization (WHO) for safe drinking and recreational water standards.

These toxins are often found in lakes and reservoirs, such as Lake Erie and Lake Taihu, and are increasing in frequency and severity due to warmer water temperatures and nutrient pollution. The World Health Organization (WHO) has set guidelines for MC levels in drinking water, but more research is needed to fully understand the impact of these toxins, especially NODs, on human health. 

Algae bloom in Lake Erie

Toxic algae bloom in Lake Erie

Cyanobacteria relates to the AP Biology topics cells and the chemistry of water. Cyanobacteria is an example of a prokaryotic cell that is known to have existed since the earliest form of life. Additionally, since cyanobacteria is able to float on the surface of water it allows them to easily perform photosynthesis. While prokaryotic cells do not have any membrane bound organelles such as chloroplasts, cyanobacteria is able to perform photosynthesis nonetheless. Their ability to perform photosynthesis stems from the photosynthetic pigments such as chlorophyll. Overall, I believe now more than ever we must spend more time and effort on understanding these cyanobacteria before it is too late. Global warming coupled with the increasing presence of cHABs makes understanding their health risks even more crucial. Efforts to mitigate their spread and better assess the impact of combined pollutants are essential to protect public health and our ecosystems. I was surprised to learn about these common dangerous toxins, so have you ever considered how different local bodies of water may contain these toxins before?