Cyanobacteria, also known as blue-green algae, are diverse photosynthetic bacteria that play a crucial role in Earth’s ecosystems. These photosynthetic bacteria are pivotal in our environment, contributing to oxygen production and soil enrichment. However, in specific conditions, cyanobacteria growth can result in harmful algae blooms (HABs) that disrupt aquatic life and pose health risks to humans. This blog explores the significance of cyanobacteria, their vertical migration patterns, and how modeling tools can help manage and mitigate their impact.
Cyanobacteria are found in various habitats, from freshwater lakes to marine environments and terrestrial ecosystems. Through photosynthesis, they harness sunlight and carbon dioxide to produce organic matter, significantly boosting atmospheric oxygen levels. These remarkable microorganisms also fix atmospheric nitrogen, enhancing soil fertility and supporting other organisms’ growth.
Certain cyanobacteria species exhibit vertical migration in water columns, with Microcystis aeruginosa, Oscillatoria agardhii, and Anabaena flos-aqua examples. Vertical migration allows the bacteria to access light-rich surface layers for photosynthesis and nutrient-rich lower layers for sustenance.
However, under specific circumstances, cyanobacteria lose this vertical stability, leading to the formation of HABs. These blooms diminish sunlight penetration, deplete oxygen levels, and harm aquatic life. Moreover, some cyanobacteria produce toxic cyanotoxins that can contaminate water supplies, posing health risks like liver damage, skin irritation, and neurological effects.
Software tools have been developed to simulate the vertical migration of algae and help researchers and environmentalists manage and mitigate cyanobacteria-related issues. An example of such a tool is EFDC+ Explorer (EEMS), which offers four ways to specify the settling velocity of cyanobacteria and any other algal species for vertical migration modeling:
A simple test model was set up to demonstrate the cyanobacteria vertical migration option in EEMS. The model consists of a single cell horizontally and 20 layers vertically. The results demonstrate the tool’s ability to accurately depict the cyanobacteria vertical migration due to changes in light levels. A vertical slice, or 2DV animation in Figure 2 below, clearly shows the vertical movement of a colony of cyanobacteria using the “Dynamic Velocity” option.
Figure 2. Animation showing the vertical movement of a colony of cyanobacteria
To better see the impact of various option, the animation in Figure 3, below shows the results of the test model’s simulation of cyanobacteria vertical migration using the four available options available in EEMS. It can be seen that the results are similar between the “Daily Cycle Velocity” and “Daily Cycle Velocity with Depth-varying Light Effects” options since they use very similar equations. In contrast, the results from the “Dynamic Velocity” and “Constant Velocity” methods notably differ.
Figure 3. Animation showing a comparison of vertical movement using different options
If you want to know more about the software tools described here, you can read more on the EEMS website. If you want to learn more about matters discussed in this blog, contact the DSI team today.
