Phytoplankton Ecology

Light pollution, which illuminates the night sky, promotes the growth of cyanobacteria (often called blue-green algae) and stimulates metabolic processes in lakes. This is shown by a recent study by the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB) in the largest field experiment to date on the effect of light pollution on lakes. The results have been published in the scientific journal Water Research.

Researchers from the Global Lake Ecosystem Observatory Network have now reviewed the factors that cause algal blooms to subside, the challenges in combating them, and how to deal with current and ongoing effects of climate change.

Oxygen is essential for most aquatic organisms. Chemical and biological processes, such as the ability to self-purify, are also dependent on oxygen. However, environmental changes and rising water temperatures are altering the oxygen content of lakes, ponds and pools. Oxygen concentrations in the deep layers of lakes are decreasing worldwide. In addition, oxygen depletion can lead to an increased release of greenhouse gases. IGB researchers are investigating the extent and consequences of this. In the process, they are also questioning some theories about the laws of lake ecology.

Microplastics are found in lakes and reservoirs around the world. Pollution reaches even the most secluded places where human influence is minimal. Moreover, concentrations of microplastics in freshwaters are sometimes higher than in subtropical gyres, the marine areas where large amounts of waste accumulate. These are the findings of an international study of 38 lakes and reservoirs led by the University of Milan-Bicocca in Italy, with the participation of IGB, and published in the journal Nature.

Mass developments of cyanobacteria, so-called blue-green algae blooms, repeatedly threaten the quality of water bodies and drinking water resources worldwide. Cyanobacteria are considered to be heat-loving, and massive algal blooms are reported mainly in summer, when monitoring is particularly close. Now, an international research network involving IGB has shown that cyanobacterial blooms can also occur at colder temperatures - even under ice. If the algal blooms go unnoticed, there are risks to drinking water production.

With the help of two mobile phone apps, Igor Ogashawara and Lena Mellin want to assess the water quality of lakes considering their water colour. In an interview, they explain how these apps work and why remote sensing is so useful for their research.