Harmful Cyanobacterial Blooms: Causes, Consequences, and Controls

Abstract

Cyanobacteria are the Earth's oldest oxygenic photoautotrophs and have had major impacts on shaping its biosphere. Their long evolutionary history (≈ 3.5 by) has enabled them to adapt to geochemical and climatic changes, and more recently anthropogenic modifications of aquatic environments, including nutrient over-enrichment (eutrophication), water diversions, withdrawals, and salinization. Many cyanobacterial genera exhibit optimal growth rates and bloom potentials at relatively high water temperatures; hence global warming plays a key role in their expansion and persistence. Bloom-forming cyanobacterial taxa can be harmful from environmental, organismal, and human health perspectives by outcompeting beneficial phytoplankton, depleting oxygen upon bloom senescence, and producing a variety of toxic secondary metabolites (e.g., cyanotoxins). How environmental factors impact cyanotoxin production is the subject of ongoing research, but nutrient (N, P and trace metals) supply rates, light, temperature, oxidative stressors, interactions with other biota (bacteria, viruses and animal grazers), and most likely, the combined effects of these factors are all involved. Accordingly, strategies aimed at controlling and mitigating harmful blooms have focused on manipulating these dynamic factors. The applicability and feasibility of various controls and management approaches is discussed for natural waters and drinking water supplies. Strategies based on physical, chemical, and biological manipulations of specific factors show promise; however, a key underlying approach that should be considered in almost all instances is nutrient (both N and P) input reductions; which have been shown to effectively reduce cyanobacterial biomass, and therefore limit health risks and frequencies of hypoxic events.

Mathematical modeling of Microcystis aeruginosa growth and [D-Leu1] microcystin-LR production in culture media at different temperatures

“…As the global climate changes, the occurrence and intensity of toxic cyanobacterial blooms are expected to increase (Paerl and Huisman, 2009;Michalak et al, 2013 Paerl andOtten, 2013). Direct effects, such as rising temperatures, and indirect effects, such as intensified stratification, favor cyanobacterial blooms.…”

The relationships of meteorological factors and nutrient levels with phytoplankton biomass in a shallow eutrophic lake dominated by cyanobacteria, Lake Dianchi from 1991 to 2013

“…The occurrence and expansion of cyanobacterial blooms in aquatic ecosystems cause serious environmental problems worldwide (Paerl and Otten 2013;Sukenik et al 2015). The dynamics of cyanobacterial blooms involve the combined effects of physical (e.g., light, temperature, turbulence and mixing, and water residence time), chemical (e.g., nutrients, dissolved carbon, and salinity), and biological (e.g., grazing, microbial interactions, and allelopathy) factors and are also affected by the cyanobacterium itself (Dokulil and Teubner 2000;Heisler et al 2008;O'Neil et al 2012;Paerl and Otten 2013).…”

“…The dynamics of cyanobacterial blooms involve the combined effects of physical (e.g., light, temperature, turbulence and mixing, and water residence time), chemical (e.g., nutrients, dissolved carbon, and salinity), and biological (e.g., grazing, microbial interactions, and allelopathy) factors and are also affected by the cyanobacterium itself (Dokulil and Teubner 2000;Heisler et al 2008;O'Neil et al 2012;Paerl and Otten 2013). Nutrients (particularly nitrogen and phosphorus) play vital roles in bloom formation (Håkanson et al 2007;Heisler et al 2008;Paerl et al 2014), and meteorological factors, climate change (Hu et al 2009;Paerl and Huisman 2008;Verspagen et al 2014;Zhang et al 2012), and their indirect effects (Callieri et al 2014;Paerl and Huisman 2009;Posch et al 2012) have also been identified as contributors to the expansion of cyanobacterial blooms.…”

Cyanobacterial blooms in freshwaters bodies in a semiarid region, northeastern Brazil: A review

“…The occurrence of cyanoHABs is usually associated with an interaction of various factors, such as eutrophication, low turbulence, and high temperatures (Dokulil and Teubner, 2000;BittencourtOliveira et al, 2014;Soares et al, 2013;Paerl and Otten, 2013). These factors enable the dominance of colonial and filamentous species that can cause numerous negative effects on domestic, industrial, and recreational uses, especially in lakes and reservoirs (Dokulil and Teubner, 2000).…”

“…Anthropic interferences through the input of nutrients in aquatic environments (in addition to climatic changes) can increase cyanobacterial harmful algal blooms (cyanoHABs) (Paerl and Huisman, 2009;Paerl and Otten, 2013;Paerl et al, 2016). The conditions that cause these blooms have become increasingly more frequent in inland waters worldwide, especially during dry seasons (Carmichael and Boyer, 2016).…”