Effects Of Cyanobacterial Blooms Research Articles

Role of Hydrology in Cyanobacterial Blooms in the Floodplain Lakes

River floodplains are sites of extremely high environmental and ecological value due to high biodiversity. Floodplain lakes (FPLs) are essential parts of complex floodplain ecosystems’ biological and hydro-chemical processes. Clear seasonal cycles, determined by the regime of the parent river and closely linked to climatic conditions, are observed in these lakes. Both the quantity and the quality of water are determined by the functional phases of a floodplain lake; limnophase, when the lake is isolated from the river, and potamophase (inundation), when the floodplain lake is overflowed by the river waters. These phases highly modify lake bathymetry, water balance, chemistry, and biology. Human pressure, mostly dam construction and land use changes, alter the frequency, duration, and intensity of natural cycles of inundation. The majority of large rivers in the Northern Hemisphere have been impacted by human activity. Floodplain lakes are also affected by continuous climate change, due to the alterations of the hydrological regimes. Cyanobacterial blooms in floodplain lakes are often characterized by high qualitative and quantitative annual and long-term variability. The main forces driving cyanobacterial blooms can be found in the flooding dynamics and intensity influencing hydraulic residence time and the concentration of biogenic compounds in lake water. Cyanotoxin production and seasonal dynamics in floodplain lakes have been rarely studied, particularly in connection with the hydrological regime. Moreover, the effects of cyanobacterial blooms and their toxicity to organisms inhabiting floodplain lakes, connected rivers, and floodplains are poorly understood. Therefore, knowledge of the processes controlling floodplain lakes’ ecological conditions is crucial to implementing water management and restoration practices, protecting those fragile and precious ecosystems from degradation and possible extension.

Cyanobacterial Blooms Increase Functional Diversity of Metazooplankton in a Shallow Eutrophic Lake

Harmful cyanobacterial blooms disrupt aquatic ecosystem processes and biological functions. However, studies focusing on the effect of cyanobacterial blooms on the functional diversity of consumers are still insufficient. To examine the interactions of cyanobacterial blooms and the diversity and composition of metazooplankton, we investigated the variation in metazooplankton and their driven variables during the cyanobacterial bloom and non-bloom periods in 2020 and 2021 in Lake Xingkai. We found that cyanobacterial blooms reduced the metazooplankton species diversity but increased their biomass, functional dispersion, and functional evenness. Generalized additive mixed model results revealed that cyanobacteria showed different effects on metazooplankton biodiversity and functional diversity during the bloom and non-bloom periods. Variance partitioning analysis indicated that cyanobacteria, physicochemical variables, and temporal variation explained 15.93% of the variation in metazooplankton during the bloom period and 20.27% during the non-bloom periods. Notably, cyanobacteria during the bloom period explained more variations in metazooplankton composition than those during the non-bloom period. Our results suggest that cyanobacterial blooms significantly impact the functional diversity and community composition of metazooplankton. Physicochemical and spatiotemporal factors may mask the effects of cyanobacteria on metazooplankton. Our findings may improve the understanding of the dynamics and responses of metazooplankton communities to environmental changes and cyanobacterial blooms disturbances and enhance our ability to assess the effectiveness of aquatic ecosystem restoration and eutrophication management.

Pilot-scale study on the effects of cyanobacterial blooms on Vallisneria natans and biofilms at different phosphorus concentrations

Cyanobacterial blooms cause potential risk to submerged macrophytes and biofilms in eutrophic environments. This pilot-scale study investigated the growth, oxidative responses, and detoxification activity of aquatic plants in response to cyanobacterial blooms under different phosphorus concentrations. Variations of extracellular polymeric substances (EPSs) and microbial community composition were also assessed. Results showed that the biomass of Vallisneria natans increased with exposure to cyanobacterial blooms at higher phosphorous concentrations (P > 0.2 mg L−1). The amount of microcystin compounds (MC-LR) released into the water and the accumulation of MC-LR into both plant tissue and biofilms changed according to the phosphorus concentration. Furthermore, a certain degree of oxidative stress was induced in the plants, as evidenced by increased activity of superoxide dismutase, catalase, and peroxidase, as well as increased malondialdehyde concentrations; significant differences were also seen in acid phosphatase and glutathione S-transferase activities, as well as in glutathione concentrations. Together, these responses indicate potential mechanisms of MC-LR detoxification. Broader α-D-glucopyranose polysaccharides (PS) increased with increasing phosphorous and aggregated into clusters in biofilm EPS in response to the cyanobacterial blooms. In addition, alterations were seen in the abundance and structure of the microbial communities present in exposed biofilms. These results demonstrate that cyanobacterial blooms under different concentrations of phosphorus can induce differential responses, which can have a significant impact on aquatic ecosystems.

The effect of cyanobacterial blooms on bio- and functional diversity of zooplankton communities

Global biodiversity decline is believed to be caused by high anthropopressure. Particularly vulnerable habitats are freshwater ecosystems, which are hotspots of biodiversity. The threat to these ecosystems are cyanobacterial blooms, which tend to proliferate in the face of climate changes. Cyanobacteria development and dominance affect the whole food web, especially the zooplankton community. We used three classical biodiversity indexes (species richness, Simpson’s Diversity Index and Shannon Diversity Index) and three functional diversity indexes (functional richness, functional evenness and functional divergence) to study the impact of cyanobacterial bloom on the zooplankton community. The study was conducted in water bodies with a different period of bloom duration (short-lasting blooms vs. long-lasting blooms) in order to determine the impact of the proliferated blooms on the aquatic ecosystems. Use of functional diversity indexes allowed for identifying changes that can be overlooked by classical biodiversity indexes. We conclude that cyanobacterial bloom involves modifications of functional trait space of studied communities and, in consequence, functioning of aquatic ecosystems.

Factors related to water quality and thresholds for microcystin concentrations in subtropical Brazilian reservoirs

ABSTRACTStudies of the environmental factors that lead to cyanotoxic blooms in tropical/subtropical reservoirs are limited. While technological advances for water treatment and remediation techniques can mitigate the effects of cyanobacterial blooms, the identification of initial drivers and tipping points for minimizing cyanotoxin concentrations could be more cost effective. We studied factors related to microcystin (MC) concentrations and estimated thresholds to limit MC using a water quality dataset from 6 subtropical Brazilian reservoirs. Reservoirs varied by water chemistry and toxin concentrations (MC yearly means <0.1–17 µg/L). Phytoplankton community composition in most reservoirs was dominated by cyanobacteria, and both nitrogen-fixing and non-fixing genera were common. We found positive correlations (p < 0.05, Spearman’s rank) between MC and nutrients (ρ = 0.48–0.74) and chlorophyll a (Chl-a, ρ = 0.65) and a negative correlation between MC and total nitrogen/total phosphorus (TN/TP, ρ = −0.49). While no association between MC and water temperature was observed, MC normalized to Chl-a values were positively related to higher temperatures and lower wind velocities, indicating warmer and more stable waters had a higher probability of toxic blooms. We found thresholds for MC ≥0.1 and ≥1 µg/L related to cyanobacterial cell counts of 20 060–136 165 cells/mL, respectively, and for turbidity (5–12 NTU) and TP (0.016–0.028 mg/L), respectively. We considered these MC concentrations (0.1 and 1 µg/L) to account for different levels of toxin production. The thresholds were different from those published for temperate ecosystems but not consistently lower or higher. TN/TP molar ratios favored toxin concentration when ≤121, suggesting that less phosphorus in relation to nitrogen is necessary to allow MC production in subtropical freshwaters. High phosphorus concentrations can increase concentration of cyanotoxins in subtropical reservoirs, and our data confirm that global warming could exacerbate problems associated with toxic algal blooms.

The effects of cyanobacterial blooms on MODIS-L2 data products in the southern Caspian Sea

The effects of cyanobacterial blooms on MODIS-L2 data products in the southern Caspian Sea

The effects of cyanobacterial blooms on the immune system of Elliptio complanata in urban and agricultural areas in the Yamaska River watershed

The cumulative effects of cyanobacterial blooms at sites impacted by urban or agricultural activity, could be detrimental to local freshwater mussels. The purpose of this study was to examine and compare the resulting toxicity using an upstream–downstream approach at four sites in the Yamaska River. Mussels were caged and placed at a site where cyanobacterial blooms were present, a site that receives municipal effluent from a small city of 75,000 inhabitants, and a site that drains a large agricultural area—plus a reference site in Lake Saint-Pierre (Quebec, Canada) for four months spanning the summer and fall (June to October). Effects on immunocompetence were monitored by testing for hemocyte counts, viability, phagocytosis, production of nitric oxide (NO), lysozyme (LY), reactive oxygen species (ROS), thiol contents, and inflammation induced by cyclooxygenase (COX) activity and glutathione S-transferase (GST) activity. Cyanobacterial blooms occurred at the target site only, reaching levels of 2.1 million cyanobacteria/L and 3 g/L of microcystin-LR in surface waters. Although most of the immune parameters were affected at the urban, agricultural and cyanobacteria sites, ROS and LY were the most responsive to cyanobacterial bloom, with a significantly greater response than the agriculture, urban and reference sites. The results also suggest that the effects of cyanobacterial blooms are spatially localized; they are not found at the downstream urban and agriculture sites in the Yamaska River.

Effects of Lyngbya majuscula blooms on the seagrass Halodule wrightii and resident invertebrates

Cyanobacterial blooms have been increasing worldwide due to increased nutrients associated with urban, industrial, and agricultural development. Blooms that occur in the Indian River Lagoon (IRL), Florida may be increased by nutrient-laden runoff from storm water and non-point sewage pollution due to alterations to the watershed. In the IRL, during the summer of 2006, extensive blooms of the marine cyanobacterium, Lyngbya majuscula, were observed forming mats throughout beds of the seagrass Halodule wrightii in Fort Pierce, Florida. The effects of cyanobacterial blooms were compared to artificial shading of H. wrightii to assess the shading potential of L. majuscula. The combined effects of L. majuscula removal and artificial shading showed increases in the below ground biomass of H. wrightii. However, leaf length increased in the presence of L. majuscula. In response to artificial shading, H. wrightii decreased in density, but showed similar leaf elongation. A common bivalve in our study area, Macoma constricta, increased in density when L. majuscula was removed. Therefore, when L. majuscula blooms occur, light limitation is one of the mechanisms altering H. wrightii density and leaf lengths in the IRL. Loss of H. wrightii biomass due to shading from cyanobacterial mats may further damage the diversity and habitat value of the IRL.

Temperature and nutrients are significant drivers of seasonal shift in phytoplankton community from a drinking water reservoir, subtropical China

Reservoirs are an important source of water supply in many densely populated areas in southeast China. Phytoplankton plays an important role in maintaining the structure and function of these reservoir ecosystems. Understanding of seasonal succession in phytoplankton communities and its driving factors is essential for effective water quality management in drinking-water reservoirs. In this study, water samples were collected monthly at the surface layers of riverine, transitional, and lacustrine zones from May 2010 to April 2011 in Tingxi Reservoir, southeast China. The phytoplankton showed distinct seasonal shifts in community structure at both taxonomic and functional levels. Cyanophyta was the dominant group in summer, especially species of Raphidiopsis in May and Aphanizomenon in June, and cyanobacterial dominance was promoted by both warmer conditions and excessive nutrients loading. Cyanophyta was gradually replaced by Cryptophyta (e.g., Chroomonas caudata) in abundance and by Bacillariophyta (Fragilaria sp. or Synedra sp. and Melosira sp.) in biomass with decreasing temperature. It appeared that seasonal shifts in phytoplankton composition were closely related to climate, nutrient status, and hydrology in this reservoir. Our partial RDA results clearly showed that water temperature and nutrients (TN and TP) were the most critical factors driving phytoplankton community shift in the abundance and biomass data, respectively. Further, with the global warming, cyanobacterial blooms may increase in distribution, duration, and intensity. In our study, the abundance and biomass of cyanobacteria had significant and positive correlations with temperature and phosphorus. Therefore, a stricter limit on nutrient input should be a priority in watershed management to protect drinking water from the effects of cyanobacterial blooms, especially in high-temperature period.

123. Effects of Cyanobacterial Bloom on Fish: Proteomics and Histological Investigation on the Medaka Oryzias Latipes

123. Effects of Cyanobacterial Bloom on Fish: Proteomics and Histological Investigation on the Medaka Oryzias Latipes

Long-term (1956–1999) dynamics of phosphorus in a shallow, subtropical Chinese lake with the possible effects of cyanobacterial blooms

This paper describes the long-term dynamics of phosphorus concentrations in both the lake water and the sediment in a subtropical Chinese lake, Lake Donghu. The total phosphorus (TP) concentration in the lake water experienced an upward trend from the 1950s, and peaked in 1983/1984, but declined obviously afterwards. From the 1950s to the1990s, TP content in the upper 10 cm sediment of the lake increased steadily from 0.307 to 1.68 mg P g DW −1 at Station I and from 0.151 to 0.89 mg P g DW −1 at Station II, respectively. The TP increase in the lake water before mid-1980s was mainly attributed to the massive input of sewage P. The outbreak of cyanobacterial blooms coincided with the peaks of TP and Orthophosphate (PO 4-P) in the water in mid-1980s, and the maximum TP of the water reached as high as 1.349 mg/l at Station I and 0.757 mg/l at Station II (in 1984), respectively. The declines of TP and PO 4-P in the water after mid-1980s was coincident with the disappearance of cyanobacterial bloom.