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3 pages, 151 KiB

Open AccessEditorial

Harmful Blooms of Cyanobacteria: Adding Complexity to a Well-Studied Topic

by Maria Moustaka-Gouni and Ulrich Sommer

Water 2021, 13(19), 2645; https://doi.org/10.3390/w13192645 - 26 Sep 2021

Viewed by 1486

Abstract

Cyanobacteria are the oldest phylogenetic group of organisms performing “plant type” (O₂-producing) photosynthesis [...] Full article

(This article belongs to the Special Issue Effects of Harmful Cyanobacteria on Ecosystem Functioning, Food Webs, and Water Quality)

Research

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20 pages, 4199 KiB

Open AccessArticle

Interannual and Spatial Variability of Cyanotoxins in the Prespa Lake Area, Greece

by Valentini Maliaka, Miquel Lürling, Christian Fritz, Yvon J.M. Verstijnen, Elisabeth J. Faassen, Frank van Oosterhout and Alfons J.P. Smolders

Water 2021, 13(3), 357; https://doi.org/10.3390/w13030357 - 30 Jan 2021

Cited by 8 | Viewed by 3187

Abstract

The Prespa Lakes area in Greece—comprised partly of lake Great and lake Lesser Prespa and the Vromolimni pond—has a global importance for biodiversity. Although the waters show regular cyanobacteria blooms, assessments of water quality threats are limited. Samples collected in 2012 revealed scattered [...] Read more.

The Prespa Lakes area in Greece—comprised partly of lake Great and lake Lesser Prespa and the Vromolimni pond—has a global importance for biodiversity. Although the waters show regular cyanobacteria blooms, assessments of water quality threats are limited. Samples collected in 2012 revealed scattered and low microcystin (MC) concentrations in Great Prespa (<0.2 μg MC L⁻¹) whereas considerable spatial heterogeneity in both total chlorophyll (2.4–93 µg L⁻¹) and MC concentrations (0.04–52.4 µg MC L⁻¹) was detected in Lesser Prespa. In 2013, there was far less spatial variability of MC concentrations in Lesser Prespa (0.4–1.53 µg L⁻¹), however in 2014, increased concentrations were detected near the lakeshore (25–861 µg MC L⁻¹). In Vromolimni pond the MC concentrations were on average 26.6 (±6.4) µg MC L⁻¹ in 2012, 2.1 (±0.3) µg MC L⁻¹ in 2013 and 12.7 (±12.5) µg MC L⁻¹ in 2014. In 2013, no anatoxins, saxitoxins, nor cylindrospermopsins were detected in Lesser Prespa and Vromolimni waters. Tissue samples from carps, an otter and Dalmatian Pelicans contained 0.4–1.9 µg MC g⁻¹ dry weight. These results indicate that cyanotoxins could be a threat to the ecosystem functions of particularly Lesser Prespa and Vromolimni. Full article

(This article belongs to the Special Issue Effects of Harmful Cyanobacteria on Ecosystem Functioning, Food Webs, and Water Quality)

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20 pages, 1909 KiB

Open AccessArticle

Uptake and Effects of Cylindrospermopsin: Biochemical, Physiological and Biometric Responses in The Submerged Macrophyte Egeria densa Planch

by Nelida Cecilia Flores-Rojas and Maranda Esterhuizen

Water 2020, 12(11), 2997; https://doi.org/10.3390/w12112997 - 26 Oct 2020

Cited by 5 | Viewed by 1804

Abstract

Cylindrospermopsin (CYN) is being detected in surface waters more commonly and frequently worldwide. This stable, extracellular cyanotoxin causes protein synthesis inhibition, thus posing a risk to aquatic biota, including macrophytes, which serve as primary producers. Nevertheless, data regarding the effects caused by environmental [...] Read more.

Cylindrospermopsin (CYN) is being detected in surface waters more commonly and frequently worldwide. This stable, extracellular cyanotoxin causes protein synthesis inhibition, thus posing a risk to aquatic biota, including macrophytes, which serve as primary producers. Nevertheless, data regarding the effects caused by environmental concentrations of CYN is still limited. In the presented study, the uptake of CYN at environmental concentrations by the submerged macrophyte Egeria densa was investigated. Bioaccumulation, changes in the plant biomass, as well as shoot-length were assessed as responses. Variations in the cellular H₂O₂ levels, antioxidative enzyme activities, as well as concentrations and ratios of the photosynthetic pigments were also measured. E. densa removed 54% of CYN within 24 h and up to 68% after 336 h; however, CYN was not bioaccumulated. The antioxidative enzyme system was activated by CYN exposure. Pigment concentrations decreased with exposure but normalized after 168 h. The chlorophyll a to b ratio increased but normalized quickly thereafter. Carotenoids and the ratio of carotenoids to total chlorophylls increased after 96 h suggesting participation in the antioxidative system. Growth stimulation was observed. The ability to remove CYN and resistance to CYN toxicity within 14 days proved E. densa as suitable for phytoremediation; nonetheless, prolonged exposure (32 days) resulted in adverse effects related to CYN uptake, which needs to be studied further. Full article

(This article belongs to the Special Issue Effects of Harmful Cyanobacteria on Ecosystem Functioning, Food Webs, and Water Quality)

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24 pages, 4843 KiB

Open AccessArticle

Urea Inputs Drive Picoplankton Blooms in Sarasota Bay, Florida, U.S.A.

by James E. Ivey, Jennifer L. Wolny, Cynthia A. Heil, Susan M. Murasko, Julie A. Brame and Ashley A. Parks

Water 2020, 12(10), 2755; https://doi.org/10.3390/w12102755 - 3 Oct 2020

Cited by 11 | Viewed by 3792

Abstract

Recent increases in global urea usage, including its incorporation in slow-release fertilizers commonly used in lawn care in Florida, have the potential to alter the form and amount of nitrogen inputs to coastal waters. This shift may, in turn, impact phytoplankton community diversity [...] Read more.

Recent increases in global urea usage, including its incorporation in slow-release fertilizers commonly used in lawn care in Florida, have the potential to alter the form and amount of nitrogen inputs to coastal waters. This shift may, in turn, impact phytoplankton community diversity and nutrient cycling processes. An autonomous water quality monitoring and sampling platform containing meteorological and water quality instrumentation, including urea and phycocyanin sensors, was deployed between June and November of 2009 in Sarasota Bay, Florida. This shallow, lagoonal bay is characterized by extensive and growing urban and suburban development and limited tidal exchange and freshwater inputs. During the monitoring period, three high-biomass (up to 40 µg chlorophyll-a·L⁻¹) phytoplankton blooms dominated by picocyanobacteria or picoeukaryotes were observed. Each bloom was preceded by elevated (up to 20 μM) urea concentrations. The geolocation of these three parameters suggests that “finger canals” lining the shore of Sarasota Bay were the source of urea pulses and there is a direct link between localized urea inputs and downstream picoplankton blooms. Furthermore, high frequency sampling is required to detect the response of plankton communities to pulsed events. Full article

(This article belongs to the Special Issue Effects of Harmful Cyanobacteria on Ecosystem Functioning, Food Webs, and Water Quality)

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19 pages, 1962 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Exploring How Cyanobacterial Traits Affect Nutrient Loading Thresholds in Shallow Lakes: A Modelling Approach

by Manqi Chang, Sven Teurlincx, Jan H. Janse, Hans W. Paerl, Wolf M. Mooij and Annette B. G. Janssen

Water 2020, 12(9), 2467; https://doi.org/10.3390/w12092467 - 2 Sep 2020

Cited by 12 | Viewed by 4078

Abstract

Globally, many shallow lakes have shifted from a clear macrophyte-dominated state to a turbid phytoplankton-dominated state due to eutrophication. Such shifts are often accompanied by toxic cyanobacterial blooms, with specialized traits including buoyancy regulation and nitrogen fixation. Previous work has focused on how [...] Read more.

Globally, many shallow lakes have shifted from a clear macrophyte-dominated state to a turbid phytoplankton-dominated state due to eutrophication. Such shifts are often accompanied by toxic cyanobacterial blooms, with specialized traits including buoyancy regulation and nitrogen fixation. Previous work has focused on how these traits contribute to cyanobacterial competitiveness. Yet, little is known on how these traits affect the value of nutrient loading thresholds of shallow lakes. These thresholds are defined as the nutrient loading at which lakes shift water quality state. Here, we used a modelling approach to estimate the effects of traits on nutrient loading thresholds. We incorporated cyanobacterial traits in the process-based ecosystem model PCLake+, known for its ability to determine nutrient loading thresholds. Four scenarios were simulated, including cyanobacteria without traits, with buoyancy regulation, with nitrogen fixation, and with both traits. Nutrient loading thresholds were obtained under N-limited, P-limited, and colimited conditions. Results show that cyanobacterial traits can impede lake restoration actions aimed at removing cyanobacterial blooms via nutrient loading reduction. However, these traits hardly affect the nutrient loading thresholds for clear lakes experiencing eutrophication. Our results provide references for nutrient loading thresholds and draw attention to cyanobacterial traits during the remediation of eutrophic water bodies. Full article

(This article belongs to the Special Issue Effects of Harmful Cyanobacteria on Ecosystem Functioning, Food Webs, and Water Quality)

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17 pages, 4145 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Interannual and Seasonal Shift between Microcystis and Dolichospermum: A 7-Year Investigation in Lake Chaohu, China

by Min Zhang, Zhen Yang, Yang Yu and Xiaoli Shi

Water 2020, 12(7), 1978; https://doi.org/10.3390/w12071978 - 13 Jul 2020

Cited by 23 | Viewed by 2628

Abstract

The shifts among bloom-forming cyanobacteria have attracted increasing attention due to the reductions in nitrogen and phosphorus during the eutrophication mitigation process. However, knowledge is limited regarding the pattern and drivers of the shifts among these cyanobacterial genera. In this study, we performed [...] Read more.

The shifts among bloom-forming cyanobacteria have attracted increasing attention due to the reductions in nitrogen and phosphorus during the eutrophication mitigation process. However, knowledge is limited regarding the pattern and drivers of the shifts among these cyanobacterial genera. In this study, we performed a 7-year long, monthly investigation in Lake Chaohu, to analyze the interannual and seasonal shifts between Microcystis and Dolichospermum. Our results showed that Microcystis was the dominant cyanobacterium in the western lake region in summer, whereas Dolichospermum was dominant in the other regions and seasons. The Microcystis biomass and ratio were driven primarily by total phosphorus and temperature. The sensitivity of Dolichospermum to nutrients and temperature was relatively weak compared to that of Microcystis. The shifts between Microcystis and Dolichospermum might be led by Microcystis. If the temperature and phosphorus level were relatively high, then Microcystis grew rapidly, and competitively excluded Dolichospermum. If the nutrient level, especially the phosphorus level, was low, then the exclusive power of Microcystis was weak, and Dolichospermum maintained its dominance, even in summer. The key temperature (~17 °C) determined the dominance of the two cyanobacteria. Microcystis never dominated, while Dolichospermum was always dominant below the key temperature. Microcystis and Dolichospermum had different means of responding to the interaction of temperature, nitrogen and phosphorus. The Dolichospermum biomass was sensitive to the variation in nitrogen level, and the sensitivity depended on temperature. While the Microcystis biomass was sensitive to the variation in phosphorus level, and the sensitivity depended on temperature and total nitrogen. The different ways might contribute to the succession of the two cyanobacteria. Our findings will be helpful for improving the understanding of the shift process between Microcystis and Dolichospermum. Full article

(This article belongs to the Special Issue Effects of Harmful Cyanobacteria on Ecosystem Functioning, Food Webs, and Water Quality)

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Review

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41 pages, 1516 KiB

Open AccessEditor’s ChoiceReview

Cyanobacteria and Cyanotoxins in a Changing Environment: Concepts, Controversies, Challenges

by Ingrid Chorus, Jutta Fastner and Martin Welker

Water 2021, 13(18), 2463; https://doi.org/10.3390/w13182463 - 7 Sep 2021

Cited by 58 | Viewed by 6793

Abstract

Concern is widely being published that the occurrence of toxic cyanobacteria is increasing in consequence of climate change and eutrophication, substantially threatening human health. Here, we review evidence and pertinent publications to explore in which types of waterbodies climate change is likely to [...] Read more.

Concern is widely being published that the occurrence of toxic cyanobacteria is increasing in consequence of climate change and eutrophication, substantially threatening human health. Here, we review evidence and pertinent publications to explore in which types of waterbodies climate change is likely to exacerbate cyanobacterial blooms; whether controlling blooms and toxin concentrations requires a balanced approach of reducing not only the concentrations of phosphorus (P) but also those of nitrogen (N); how trophic and climatic changes affect health risks caused by toxic cyanobacteria. We propose the following for further discussion: (i) Climate change is likely to promote blooms in some waterbodies—not in those with low concentrations of P or N stringently limiting biomass, and more so in shallow than in stratified waterbodies. Particularly in the latter, it can work both ways—rendering conditions for cyanobacterial proliferation more favourable or less favourable. (ii) While N emissions to the environment need to be reduced for a number of reasons, controlling blooms can definitely be successful by reducing only P, provided concentrations of P can be brought down to levels sufficiently low to stringently limit biomass. Not the N:P ratio, but the absolute concentration of the limiting nutrient determines the maximum possible biomass of phytoplankton and thus of cyanobacteria. The absolute concentrations of N or P show which of the two nutrients is currently limiting biomass. N can be the nutrient of choice to reduce if achieving sufficiently low concentrations has chances of success. (iii) Where trophic and climate change cause longer, stronger and more frequent blooms, they increase risks of exposure, and health risks depend on the amount by which concentrations exceed those of current WHO cyanotoxin guideline values for the respective exposure situation. Where trophic change reduces phytoplankton biomass in the epilimnion, thus increasing transparency, cyanobacterial species composition may shift to those that reside on benthic surfaces or in the metalimnion, changing risks of exposure. We conclude that studying how environmental changes affect the genotype composition of cyanobacterial populations is a relatively new and exciting research field, holding promises for understanding the biological function of the wide range of metabolites found in cyanobacteria, of which only a small fraction is toxic to humans. Overall, management needs case-by-case assessments focusing on the impacts of environmental change on the respective waterbody, rather than generalisations. Full article

(This article belongs to the Special Issue Effects of Harmful Cyanobacteria on Ecosystem Functioning, Food Webs, and Water Quality)

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19 pages, 1570 KiB

Open AccessReview

Effects of Harmful Blooms of Large-Sized and Colonial Cyanobacteria on Aquatic Food Webs

by Maria Moustaka-Gouni and Ulrich Sommer

Water 2020, 12(6), 1587; https://doi.org/10.3390/w12061587 - 3 Jun 2020

Cited by 40 | Viewed by 5070

Abstract

Cyanobacterial blooms are the most important and best studied type of harmful algal blooms in fresh waters and brackish coastal seas. We here review how and to which extent they resist grazing by zooplankton, how zooplankton responds to cyanobacterial blooms and how these [...] Read more.

Cyanobacterial blooms are the most important and best studied type of harmful algal blooms in fresh waters and brackish coastal seas. We here review how and to which extent they resist grazing by zooplankton, how zooplankton responds to cyanobacterial blooms and how these effects are further transmitted to fish. Size, toxicity and poor nutritional value are widespread mechanisms of grazing defense by cyanobacteria. In some cases, defenses are inducible, in some they are obligate. However, to some extent zooplankton overcome grazing resistance, partly after evolutionary adaptation. Cyanotoxins are also harmful to fish and may cause fish kills. However, some fish species feed on Cyanobacteria, are able to reduce their abundance, and grow on a cyanobacterial diet. While reduced edibility for crustacean zooplankton tends to elongate the food chain from primary producers to fish, direct feeding by fish tends to shorten it. The few available comparative studies relating fish yield to nutrients or phytoplankton provide no indication that cyanobacteria should reduce the ratio fish production: primary production. Full article

(This article belongs to the Special Issue Effects of Harmful Cyanobacteria on Ecosystem Functioning, Food Webs, and Water Quality)

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