Predicting Cyanobacteria dominance in lakes

Suspended algae, or phytoplankton, are the prime source of organic matter supporting food webs in freshwater ecosystems. Phytoplankton productivity is reli-ant 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, deoxy-genation 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 (N 2), 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 N 2-and non-N 2-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 hy-drologic, 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.

Scientific reports, 2017

We investigated possibility of predicting whether blooms, if they occur, would be formed of microcystin-producing cyanobacteria. DGGE analysis of 16S-ITS and mcyA genes revealed that only Planktothrix and Microcystis possessed mcy-genes and Planktothrix was the main microcystin producer. qPCR analysis revealed that the proportion of cells with mcy-genes in Planktothrix populations was almost 100%. Microcystin concentration correlated with the number of potentially toxic and total Planktothrix cells and the proportion of Planktothrix within all cyanobacteria, but not with the proportion of cells with mcy-genes in total Planktothrix. The share of Microcystis cells with mcy-genes was low and variable in time. Neither the number of mcy-possessing cells, nor the proportion of these cells in total Microcystis, correlated with the concentration of microcystins. This suggests that it is possible to predict whether the bloom in the Masurian Lakes will be toxic based on Planktothrix occurrenc...

Journal of Plankton Research, 2009

2015

Bloom-forming cyanobacteria are harmful to both environment and public health because of the release of water soluble toxins. This report provides a broad overview of cyanobacteria and cyanotoxins and the current state of knowledge about the bloom control management. Cyanobacteria blooms usually flourish in warm, lentic, and eutrophic waters. Several environmental factors such as temperature, nutrients, light intensity, and turbulence can affect cyanobacterial growth and the formation of bloom. Cyanobacteria can synthesize multiple types of toxins, which cause human and animal toxications worldwide. Cyanobacterial blooms also cause detrimental effects on aquatic ecosystems, and the taste and odor problems in drinking water supplies. Due to the adverse effects, treatments that are used for removing both cyanobacterial cells and aqueous cyanotoxins should be carried out once cyanobacterial blooms occur in freshwaters. Strategies based on physical, chemical, and biological methods are carried out to remove the cyanobacteria and cyanotoxins. All of these strategies have both advantages and disadvantages: some physical treatment methods can remove cyanotoxins within the intact molecules, but the cost is usually high and further processing is needed; some chemical methods are cheap and can degrade the cyanotoxins, however, the toxicological characterization of the chemical and the by-products needs to be investigated; some biological treatments are more environmentally friendly, but the long reaction time and some other external factors also pose some problems that affect the efficiency of the treatments. The paper concludes that the key to success is to find a reasonable balance between those advantages and disadvantages, and the specific conditions of each unique aquatic ecosystem should be taken into consideration. As well, some suggestions are also proposed for the further development of more robust monitoring and management strategies.

FEMS Microbiology Ecology, 2014

Nutrients have the capacity to change cyanobacterial toxin loads via growth-related toxin production, or shifts in the dominance of toxic and non-toxic strains. This study examined the effect of nitrogen (N) and phosphorus on cell division and strain-related changes in production of the toxins, cylindrospermopsins (CYNs) by the cyanobacterium, Cylindrospermopsis raciborskii. Two short-term experiments were conducted with mixed phytoplankton populations dominated by C. raciborskii in a subtropical reservoir where treatments had nitrate (NO3), urea (U) and inorganic phosphorus (P) added alone or in combination. Cell division rates of C. raciborskii were only statistically higher than the control on day 5 when U and P were co-supplied. In contrast, cell quotas of CYNs (Q CYNS ) increased significantly in treatments where P was supplied, irrespective of whether N was supplied, and this increase was not necessarily related to cell division rates. Increased Q CYNS did correlate with an increase in the proportion of the cyrA toxin gene to 16S genes in the C. raciborskiidominated cyanobacterial population. Therefore changes in strain dominance is the most likely factor driving differences in toxin production between treatments. Our study has demonstrated differential effects of nutrients on cell division and strain dominance reflecting a C. raciborskii

Canadian Journal of Fisheries and Aquatic Sciences, 2016

Algal bloom reports are on the rise across Canada. While eutrophication is the main driver, other stressors of aquatic ecosystems, specifically climate change and food web alterations from the spread of invasive species and overfishing, are compounding factors acting in concert or independently. Current models can predict the average algal and cyanobacterial biomass concentrations across temperate lakes as a function of nutrients, but models to specifically predict harmful algal composition and toxicity are lacking. At the within-lake scale, where management occurs, strong year to year variations in cyanobacterial blooms remain challenging to explain, let alone predict. The most common cyanotoxins, the hepatotoxic microcystins, are chemically diverse with some variants more toxic than others and with greater propensity for persistence and bioaccumulation. These differences have been largely overlooked, as current guidelines have been based on microcystin-LR, considered the most common variant. Microcystin-LA is also encountered in Canadian waters and appears to exhibit greater persistence and bioaccumulation. With cyanobacterial blooms most likely to increase across the country, including the north, guidelines and policies for cyanotoxins in drinking and recreational waters as well as fish will need to be developed for the protection of ecosystem and human health. Ultimately, control of eutrophication is the most important option for managing toxic cyanobacterial blooms; nitrogen and phosphorus need to be considered as environmental contaminants, as both play a role in controlling the dominance of toxigenic cyanobacteria. Résumé : Les signalements de fleurs d'eau sont en hausse au Canada. Si l'eutrophisation en est la principale cause, d'autres facteurs de stress pour les écosystèmes aquatiques, plus précisément les changements climatiques et les modifications des réseaux trophiques découlant de la propagation d'espèces envahissantes et de la surpêche, agissent de concert avec cette dernière ou de manière indépendante. Les modèles actuels peuvent prédire les concentrations moyennes de biomasse d'algues et de cyanobactéries dans les lacs tempérés en fonction des nutriments, mais des modèles permettant de prédire la composition et la toxicité des algues nuisibles en particulier manquent toujours. À l'échelle d'un lac faisant l'objet d'une gestion, il est difficile d'expliquer et encore plus difficile de prédire les fortes variations interannuelles des proliférations de cyanobactéries observées. Les cyanotoxines les plus répandues, les microcystines hépatotoxiques, sont variées sur le plan chimique, certaines variantes étant plus toxiques que d'autres et plus susceptibles de persister et de se bioaccumuler. Ces différences ont été largement négligées, les directives actuelles étant basées sur la microcystine-LR, considérée comme la variante la plus répandue. La microcystine-LA est également présente dans les eaux canadiennes et semble caractérisée par une persistance et une bioaccumulation plus grandes. Comme les proliférations de cyanobactéries iront probablement en augmentant à la grandeur du pays, notamment dans le nord, des directives et politiques concernant les cyanotoxines dans l'eau potable et les plans d'eau destinés aux loisirs, ainsi que chez les poissons, devront être élaborées pour protéger la santé des écosystèmes et des humains. Au final, le contrôle de l'eutrophisation est l'option la plus importante pour gérer des proliférations de cyanobactéries toxiques; l'azote et le phosphore doivent être vus comme des contaminants du milieu puisqu'ils jouent tous deux un rôle dans la modulation de la prédominance des différentes cyanobactéries toxigènes. [Traduit par la Rédaction]

Limnology [Working Title]

This chapter will present an overview of cyanobacterial harmful algal blooms (cyano-HABs) and biotic and abiotic factors, as well as various aspects associated with these worldwide ecological bursts. The exact causes of the cyanoHABs are still not well defined, but eutrophication and climate change (temperature increase, light intensity variation, etc.) are the two assumed main factors that may promote the proliferation and expansion of cyanobacterial blooms. However, these premises need to be profoundly investigated as the optimal combination of all factors such as increased nutrient loading, physiological characteristics of cyanobacterial species, and climate effects which could lead to the blooming pattern will require robust modeling approaches to predict the phenomena. Negative issues associated with cyanoHABs are diverse including the toxic products (cyanotoxins) released by certain taxa which can damage the health of humans and animal habitats around the related watershed as well as generate a huge water quality problem for aquatic industries.

Delta (California)

Harmful cyanobacteria and their toxins are growing contaminants of concern. Noxious toxins produced by HC, collectively referred as cyanotoxins, reduce the water quality and may impact the supply of clean water for drinking as well as the water quality which directly impacts the livelihood of other species including several endangered species. USEPA recently (May 29, 2008) made the decision to add microcystin toxins as an additional cause of impairment for the Klamath River, CA. However, harmful cyanobacteria are some of the less studied causes of impairment in California water bodies and their distribution, abundance and dynamics, as well as the conditions promoting their proliferation and toxin production are not well characterized.

PLoS ONE, 2012

The importance of nitrogen (N) versus phosphorus (P) in explaining total cyanobacterial biovolume, the biovolume of specific cyanobacterial taxa, and the incidence of cyanotoxins was determined for 102 north German lakes, using methods to separate the effects of joint variation in N and P concentration from those of differential variation in N versus P. While the positive relationship between total cyanobacteria biovolume and P concentration disappeared at high P concentrations, cyanobacteria biovolume increased continually with N concentration, indicating potential N limitation in highly P enriched lakes. The biovolumes of all cyanobacterial taxa were higher in lakes with above average joint NP concentrations, although the relative biovolumes of some Nostocales were higher in less enriched lakes. Taxa were found to have diverse responses to differential N versus P concentration, and the differences between taxa were not consistent with the hypothesis that potentially N 2 -fixing Nostocales taxa would be favoured in low N relative to P conditions. In particular Aphanizomenon gracile and the subtropical invasive species Cylindrospermopsis raciborskii often reached their highest biovolumes in lakes with high nitrogen relative to phosphorus concentration. Concentrations of all cyanotoxin groups increased with increasing TP and TN, congruent with the biovolumes of their likely producers. Microcystin concentration was strongly correlated with the biovolume of Planktothrix agardhii but concentrations of anatoxin, cylindrospermopsin and paralytic shellfish poison were not strongly related to any individual taxa. Cyanobacteria should not be treated as a single group when considering the potential effects of changes in nutrient loading on phytoplankton community structure and neither should the N 2 -fixing Nostocales. This is of particular importance when considering the occurrence of cyanotoxins, as the two most abundant potentially toxin producing Nostocales in our study were found in lakes with high N relative to P enrichment. Citation: Dolman AM, Rü cker J, Pick FR, Fastner J, Rohrlack T, et al. (2012) Cyanobacteria and Cyanotoxins: The Influence of Nitrogen versus Phosphorus. PLoS ONE 7(6): e38757.

Aquatic Ecology, 2016

This is the Editorial to a Special Issue entitled ''Cyanobacterial blooms. Ecology, prevention, mitigation and control''. The Special Issue is a product of a European COST Action, CYANOCOST. In this Special Issue, contributions describe methods currently available for the management of cyanobacterial blooms, a key issue threatening the ecological functioning of lakes and the ecosystem services they provide. Contributions start with a section on the prevention of blooms, through Keywords Algal blooms Á Climate change Á Cyanobacteria Á Eutrophication Á HABS Á Lake management Cyanobacterial blooms are the most conspicuous sign of eutrophication of freshwater ecosystems.