Harmful Freshwater Algal Blooms, With an Emphasis on Cyanobacteria

By Hans W. Paerl, R. S. Fulton, Pia H. Moisander, J. Dyble. TheScientificWorldJournal, 2001

1,048 citations recorded by the source corpus.

Suspended algae, or phytoplankton, are the prime source of organic matter supporting food webs in freshwater ecosystems. Phytoplankton productivity is reliant on adequate nutrient supplies; however, increasing rates of nutrient supply, much of it manmade, fuels accelerating primary production or eutrophication. An obvious and problematic symptom of eutrophication is rapid growth and accumulations of phytoplankton, leading to discoloration of affected waters. These events are termed blooms. Blooms are a prime agent of water quality deterioration, including foul odors and tastes, deoxygenation of bottom waters (hypoxia and anoxia), toxicity, fish kills, and food web alterations. Toxins produced by blooms can adversely affect animal (including human) health in waters used for recreational and drinking purposes. Numerous freshwater genera within the diverse phyla comprising the phytoplankton are capable of forming blooms; however, the blue-green algae (or cyanobacteria) are the most notorious bloom formers. This is especially true for harmful toxic, surface-dwelling, scum-forming genera (e.g., Anabaena, Aphanizomenon, Nodularia, Microcystis) and some subsurface bloom-formers (Cylindrospermopsis, Oscillatoria) that are adept at exploiting nutrient-enriched conditions. They thrive in highly productive waters by being able to rapidly migrate between radiance-rich surface waters and nutrient-rich bottom waters. Furthermore, many harmful species are tolerant of extreme environmental conditions, including very high light levels, high temperatures, various degrees of desiccation, and periodic nutrient deprivation. Some of the most noxious cyanobacterial bloom genera (e.g., Anabaena, Aphanizomenon, Cylindrospermopsis, Nodularia) are capable of fixing atmospheric nitrogen (N2), enabling them to periodically dominate under nitrogen-limited conditions. Cyanobacteria produce a range of organic compounds, including those that are toxic to higher-ranked consumers, from zooplankton to further up the food chain. Both N2- and non-N2-fixing genera participate in mutualistic and symbiotic associations with microorganisms, higher plants, and animals. These associations appear to be of great benefit to their survival and periodic dominance. In this review, we address the ecological impacts and environmental controls of harmful blooms, with an emphasis on the ecology, physiology, and management of cyanobacterial bloom taxa. Combinations of physical, chemical, and biotic features of natural waters function in a synergistic fashion to determine the sensitivity of water bodies. In waters susceptible to blooms, human activities in water- and airsheds have been linked to the extent and magnitudes of blooms. Control and management of cyanobacterial and other phytoplankton blooms invariably includes nutrient input constraints, most often focused on nitrogen (N) and/or phosphorus (P). The types and amount of nutrient input constraints depend on hydrologic, climatic, geographic, and geologic factors, which interact with anthropogenic and natural nutrient input regimes. While single nutrient input constraints may be effective in some water bodies, dual N and P input reductions are usually required for effective long-term control and management of harmful blooms. In some systems where hydrologic manipulations (i.e., plentiful water supplies) are possible, reducing the water residence time by enhanced flushing and artificial mixing (in conjunction with nutrient input constraints) can be particularly effective alternatives. Implications of various management strategies, based on combined ecophysiological and environmental considerations, are discussed.

Subfields: Biomaterials, Environmental Chemistry, Oceanography

View Paper: https://www.semanticscholar.org/paper/9798732004cfaab19e4e1bc664f0d352b5ec55b6

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Citations in the corpus

The effects of temperature and nutrients on the growth and dynamics of toxic and non-toxic strains of Microcystis during cyanobacteria blooms (2009, background): “Frequently, cyanobacteria dominate phytoplankton assemblages in temperate freshwater environments during the warmest periods of the year, particularly in eutrophic systems (Paerl, 1988; Paerl et al., 2001; Paerl and Huisman, 2008; Paul, 2008).”
Harmful Cyanobacterial Blooms: Causes, Consequences, and Controls (2013, background): “There is broad agreement that nutrient over-enrichment of freshwater and marine ecosystems from anthropogenic sources (urban, agricultural, and industrial) has promoted CyanoHAB expansion and persistence [59, 97, 105, 106].”
Deciphering the effects of nitrogen, phosphorus, and temperature on cyanobacterial bloom intensification, diversity, and toxicity in western Lake Erie (2019, background): “2012) and can result in ecosystem disruption (Chorus and Bartram 1999; Paerl et al. 2001).”
Nutrient enrichment and selective predation by zooplankton promote Microcystis (Cyanobacteria) bloom formation (2010, background): “The formation of cyanobacterial blooms is dependent on the complex interactions of several key factors (Paerl, 1988; Oliver and Ganf, 2000; Paerl et al., 2001).”
Effects of rising CO₂ on the harmful cyanobacterium Microcystis (2016, background): “Other factors, like phosphate, iron, temperature, salinity and grazing zooplankton, also Chapter 9 influence the dominance of different cyanobacterial species (Paerl et al. , 2001; Huisman et al. , 2005; Paerl and Huisman, 2009).”
Effects of nitrogenous compounds and phosphorus on the growth of toxic and non-toxic strains of Microcystis during cyanobacterial blooms (2010, background): “Eutrophication is considered a primary cause of many HABs (Paerl 1997, Anderson et al. 2008, Heisler et al. 2008), particularly within freshwater ecosystems (Paerl 1988, 2008, Paerl et al. 2001).”
Sustainability and cyanobacteria (blue-green algae): facts and challenges (2011, background): “The ecological and physiological significance of cyanotoxin production is not yet clear (Paerl et al. 2001).”
The influence of environmental conditions on the seasonal variation of Microcystis cell density and microcystins concentration in San Francisco Estuary (2008, background): “Although there are many management strategies for control of Microcystis and its toxins (Pearl et al., 2001), regulation of streamflow may be the most important for SFE.”
In situ studies on the bioaccumulation of microcystins in the phytoplanktivorous silver carp (Hypophthalmichthys molitrix) stocked in Lake Taihu with dense toxic Microcystis blooms (2006, background): “The occurrence of toxic cyanobacterial blooms in eutrophic fresh and brackish waters has been a worldwide problem (Paerl et al., 2001).”