Pollution Affecting Cyanobacteria in Aquatic Habitats

Aquatic ecosystems comprise the largest portion (~72%) of the biosphere and play a crucial role in stabilizing the global climate as well as providing a large array of services for a fast-growing human population. Nowadays, there is a growing amount of data that prove that many anthropogenic pollutants from agricultural, urban and industrial wastes are dumped in the aquatic ecosystems and accumulate in many environments, including the habitats of marine and freshwater cyanobacteria. Cyanobacteria, as a natural part of phytoplankton assemblages, are known for their role as dominant primary producers and base of aquatic food webs. These microorganisms are continuously exposed to various concentrations of the pollutants that are present in their habitats and affect cyanobacterial communities at different levels such as abundance, growth strategies, succession patterns and dominance. Even if no direct changes in cyanobacterial communities are visible, the pollutants may accumulate in cyanobacteria and be passed onto higher trophic levels in a cascading manner, resulting in biomagnifications of certain pollutants. The most common pollutants in aquatic ecosystems are heavy metals, herbicides, pesticides, nutrients, pharmaceuticals, polycyclic aromatic hydrocarbons and microplastics. It is important to determine their concentrations in cyanobacterial cells and in their environment to know the possibility of contaminants that might be transferred to higher trophic levels. However, some strains of cyanobacteria are capable of metabolizing these pollutants that makes them less toxic or sometimes they even remove pollutants from the environment. This chapter highlights the toxic effects of different types of pollution (both point sources and non-point sources) on cyanobacterial communities in aquatic habitats. The anthropocentric concept of “pollution” and the links between pollution, eutrophication and harmful algal blooms (HABs) are also analyzed. An understanding of the synergistic interactions between these aspects and climate change effects will be useful to devise suitable remediation strategies for future use.