Effects of harmful algal blooms and associated water-quality on endangered Lost River and shortnose suckers

Target Fishing Reveals a Novel Mechanism of N-Acylamino Saccharin Derivatives Targeting Glyceraldehyde-3-Phosphate Dehydrogenase toward Cyanobacterial Blooms Control

Based on current challenges of poor targeting and limited choices in chemical control methods of cyanobacterial blooms (CBs), identifying new targets is an urgent and formidable task in the quest for target-based algaecides. This study discovered N-acylamino saccharin derivatives exhibiting potent algicidal activity. Thus, using N-acylamino saccharin as the probes, glyceraldehyde-3-phosphate dehydrogenase from cyanobacterial (CyGAPDH) was identified as a new target of algaecides through the activity-based protein profiling (ABPP) strategy for the first time. Building upon the structure of Probe2, a series of derivatives were designed and synthesized, with compound b6 demonstrating the most potent inhibitory activity against CyGAPDH and Synechocystis sp. PCC6803 (IC50 = 1.67 μM and EC50 = 1.15 μM). Furthermore, the potential covalent binding model of b6 to the cysteine residue C154 was explored through covalent possibility prediction, LC-MS experiments, substrate competitive inhibition experiments, and molecular docking. Especially, the results revealed C154 as a crucial covalent binding site, with residues T184 and R11 forming robust hydrophobic interactions and H181 establishing significant hydrogen-bonding interactions with b6, highlighting their potential as essential pharmacophores. In summary, this study not only identifies a novel target of algaecides for the control of CB but also lays the solid foundation for the development of targeted covalent algaecides.

Oxidation effects on Microcystis aeruginosa inactivation through various reactive oxygen species: Degradation efficiency, mechanisms, and physiological properties

The study investigated the inactivation of Microcystis aeruginosa using a combined approach involving thermally activated peroxyacetic acid (Heat/PAA) and thermally activated persulfate (Heat/PDS). The Heat/PDS algal inactivation process conforms to first-order reaction kinetics. Both hydroxyl radical (•OH) and sulfate radical (SO4-•) significantly impact the disruption of cell integrity, with SO4-• assuming a predominant role. PAA appears to activate organic radicals (RO•), hydroxyl (•OH), and a minimal amount of singlet oxygen (1O2). A thorough analysis underscores persulfate's superior ability to disrupt algal cell membranes. Additionally, SO4-• can convert small-molecule proteins into aromatic hydrocarbons, accelerating cell lysis. PAA can accelerate cell death by diffusing into the cell membrane and triggering advanced oxidative reactions within the cell. This study validates the effectiveness of the thermally activated persulfate process and the thermally activated peroxyacetic acid as strategies for algae inactivation.

Relation between the relative abundance and collapse of Aphanizomenon flos-aquae and microbial antagonism in Upper Klamath Lake, Oregon

Aphanizomenon flos-aquae (AFA) is the dominant filamentous cyanobacterium that develops into blooms in Upper Klamath Lake, Oregon, each year. During AFA bloom and collapse, ecosystem conditions for endangered Lost River and shortnose suckers deteriorate, thus motivating the need to identify processes that limit AFA abundance and decline. Here, we investigate the relations between AFA and other members of the microbial community (photosynthetic and nonphotosynthetic bacteria and archaea), how those relations impact abundance and collapse of AFA, and the types of microbial conditions that suppress AFA. We found significant spatial variation in AFA relative abundance during the 2016 bloom period using 16S rRNA sequencing. The Pelican Marina site had the lowest AFA relative abundance, and this was coincident with increased relative abundance of Candidatus Sericytochromatia, Flavobacterium, and Rheinheimera, some of which are known AFA antagonists. The AFA collapse coincided with phosphorus limitation relative to nitrogen and the increased relative abundance of Cyanobium and Candidatus Sericytochromatia, which outcompete AFA when dissolved inorganic nitrogen is available. The data collected in this study indicate the importance of dissolved inorganic nitrogen combined with microbial community structure in suppressing AFA abundance.

Hydraulic retention time governed the micro/nanostructures of titanium-incorporated diatoms and their photocatalytic activity

Titanium-incorporated diatoms are promising biomaterials to photodegrade micropollutants such as pharmaceuticals and personal care products (PPCPs). Hydraulic retention time (HRT) is a key parameter for diatom cultivation and the incorporation of titanium into diatom frustules. This study assessed how HRT governs the micro/nanostructures, titania (TiO2) content and distribution, and the photocatalytic activity of titanium-incorporated diatom frustules. We cultivated a diatom strain Stephanodiscus hantzschii using a feed solution containing titanium(IV) in membrane bioreactors (MBRs) at a solids retention time (SRT) of 10 d and staged HRTs from 24 to 12 and to 6 h. The decrease in HRT reduced the porosity of diatom frustules but increased their silicon and titania contents. When the HRT decreased from 24 to 12 and to 6 h, the specific surface areas of the diatom decreased from 37.65 ± 3.19 to 31.53 ± 3.71 and to 18.43 ± 2.69 m2·g-1 frustules, while the titanium (Ti) contents increased from 53 ± 14 to 71 ± 9 and to 85 ± 13 mg Ti·g-1 frustules. The increase in the influent flow rates of the MBRs with decreasing HRTs likely enhanced nutrient diffusion inside the diatom valve pores, facilitating the uptake and incorporation of silicon and titanium. The titanium-incorporated frustules were effective in removing two representative PPCPs, bisphenol A (BPA) and N,N-diethyl-meta-toluamide (DEET), from water. As photocatalytic activity depends on the amount of titanium, decreasing the HRT substantially increased the photocatalytic activity of the titanium-incorporated frustules. In batch tests under ultraviolet light, frustules from the diatom cultivated at HRTs of 24, 12, and 6 h had the pseudo-first-order removal (mainly through photodegradation) rate constants of BPA of 0.376, 0.456, and 0.683 h-1, respectively. Under the same experimental condition, the pseudo-first-order removal rate constants of DEET by the frustules cultivated at HRTs of 24, 12, and 6 h increased from 0.270 to 0.330 and to 0.480 h-1.

Prevention and control of algae residue deposition in long-distance water conveyance project

With the increase of operation cycle in long-distance water conveyance project, the problem of silt or algae residue deposition in river channels is becoming more and more prominent, especially in the vicinity of some uncommonly used bifurcation and outflow gates along the water conveyance project. When the deposition reaches certain thickness, it will not only affect the water quality of local water bodies, but also seriously affect the normal operation of these bifurcation and outflow gates. In order to alleviate this problem, the prevention and control of algae residue deposition in long-distance water conveyance project is mainly explored from two perspectives: (1) the scouring effect on the bottom of the side channel is compared by studying different diversion ratios of the side channel; (2) The arc guide wing wall is built near the junction of the main channel and side channel. The simulation is conducted at 6 different included angles including -10°, -5°, 0°, 5°, 10° and 15°, and for non-guide wing wall. The incoming flow is simulated at 280 m3/s of general flow and 320 m3/s of design flow. A total of 14 groups of experiments are carried out for numerical simulation. It can be concluded that, when the incoming flow is held constant, a higher diversion ratio results in a more effective scouring of the bottom sediment in the side channel; when the included angles of the guide wing wall are -10°, -5°, 0° and 5°, it has a significant effect on the prevention and control of algae deposition near the junction; when the included angles of the guide wing wall are 10° and 15°, it cannot play a role in prevention and control and also hinders the normal operation of the river channel.

Revealing the environmental hazard posed by biodegradable microplastics in aquatic ecosystems: An investigation of polylactic acid's effects on Microcystis aeruginosa

The influence of petroleum-based microplastics (MPs) on phytoplankton has been extensively studied, while research on the impact of biodegradable MPs, derived from alternative plastics to contest the environmental crisis, remains limited. This study performed a 63 days co-incubation experiment to assess the effect of polylactic acid MPs (PLA-MPs) on the growth, physiology, and carbon utilization of M. aeruginosa and the change in PLA-MPs surface properties. The results showed that despite PLA-MPs induced oxidative stress and caused membrane damage in M. aeruginosa, the presence of PLA-MPs (10, 50, and 200 mg/L) triggered significant increases (p < 0.05) in the density of M. aeruginosa after 63 days. Specifically, the algal densities upon 50 and 200 mg/L PLA-MPs exposure were increased by 20.91% and 36.31% relative to the control, respectively. Meanhwhile, the reduced C/O ratio on PLA-MPs surface and change in PLA-MPs morphological characterization, which is responsible for substantially increase in the aquatic dissolved inorganic carbon concentration during the co-incubation, implying the degradation of PLA-MPs; thus, provided sufficient carbon resources that M. aeruginosa could assimilate. This was in line with the declined intracellular carbonic anhydrase content in M. aeruginosa. This study is the first attempt to uncover the interaction between PLA-MPs and M. aeruginosa, and the finding that their interaction promotes the degrading of PLA-MPs meanwhile favoring M. aeruginosa growth will help elucidate the potential risk of biodegradable MPs in aquatic environment.

Geographic Variability, Seasonality, and Increase in ASPCA Animal Poison Control Center Harmful Blue-Green Algae Calls-United States and Canada, 2010-2022

Harmful cyanobacteria (blue-green algae) exposures can cause illness or death in humans and animals. We characterized American Society for the Prevention of Cruelty to Animals (ASPCA) Animal Poison Control Center (APCC) harmful blue-green algae (HBGA) call data, compared it to a measure of harmful algal bloom public awareness, and considered its suitability as a public health information source. ASPCA APCC dog and cat "HBGA exposure" calls made 1 January 2010-31 December 2022 were included. We calculated annual HBGA call percentages and described calls (species, month, origin, exposure route). We characterized public awareness by quantifying Nexis Uni® (LexisNexis Academic; New York, NY, USA)-indexed news publications (2010-2022) pertaining to "harmful algal bloom(s)". Call percentage increased annually, from 0.005% (2010) to 0.070% (2022). Of 999 HBGA calls, 99.4% (n = 993) were dog exposures. Over 65% (n = 655) of calls were made July-September, largely from the New England (n = 154 (15.4%)) and Pacific (n = 129 (12.9.%)) geographic divisions. Oral and dermal exposures predominated (n = 956 (95.7%)). Harmful algal bloom news publications increased overall, peaking in 2019 (n = 1834). Higher call volumes in summer and in the New England and Pacific geographic divisions drove HBGA call increases; public awareness might have contributed. Dogs and humans have similar exposure routes. ASPCA APCC HBGA call data could serve as a public health information source.

Metabolites dynamics exacerbated by external nutrients inputs into a Ceratium hirundinella-dominated bloom in the Pengxi River, Three Gorges Reservoir, China

Secondary metabolites (toxins) production during harmful algal blooms (HABs) further increases the public health risks associated with water quality deterioration from anthropogenic eutrophication. In the present study, the dynamic pattern in the production of metabolites under different nutrient conditions in Ceratium-dominated spring HABs was investigated in Pengxi River, China. Results revealed five (5) important toxins all attributable to the Dinophyceae including azaspiracid 2&4, okadaic acid, tetrodotoxin, brevetoxin, and saxitoxin, each exhibiting certain levels of specificity to the ecosystem enrichments. In effect, while the production of azaspiracid 2 and okadaic acid was N-driven, azaspiracid 4 and tetrodotoxin were enhanced by Ca enrichment. The ambient HABs community structure shows absolute ecosystem dominance by a dinoflagellate, Ceratium hirundinella with relative abundance ((RA = 78.81%, p ˂ 0.05). However, P enrichment triggered a slight shift (p ≥ 0.05) in the HABs species structure within the cyanobacteria strictly represented by Chroococcus minor (RA = 26.60%) and Dolichospermum circinalis (RA = 23.91%) initiating possible emergency dominance. The effect of nutrient addition on biomass production as chlorophyll-a (Chl-a) confirmed a P-limited ecosystem juxtaposed by a secondary limitation by Ca. The significant stimulation on biomass as Chl-a from day 3 through day 4 by N and the multiple enrichments designated as NPFeCa was attributed to luxury consumption rather than limitation following N repletion thus delaying biomass accumulation. The study, therefore, offers useful insights into the dynamic pattern of toxins during spring HABs while it also provides comprehensive knowledge of the HABs impact predictions in the TGR.

Comparison of peracetic acid and sodium hypochlorite enhanced Fe(Ⅱ) coagulation on algae-laden water treatment

In this study, Fe(Ⅱ)/peracetic acid (PAA) and Fe(Ⅱ)/sodium hypochlorite (NaClO) systems were applied as the combined preoxidation and coagulation process to enhance algae removal. A high removal rate of algae and turbidity could be achieved, with most algal cells keeping intact when adding reasonable concentrations of PAA and NaClO to enhance Fe(Ⅱ) coagulation. The variations of chlorophyll a, malondialdehyde, and intracellular reactive oxygen species suggested that moderate oxidation with only destroying surface-adsorbed organic matter rather than cell integrity was realized. The generated organic radicals, Fe(Ⅳ), and hydroxy radical played the major roles in the Fe(Ⅱ)/PAA system for the moderate oxidation of algal cells, but direct oxidation by NaClO rather than producing reactive species in the Fe(Ⅱ)/NaClO process contributed to the preoxidation. Concurrently, the in-situ formed Fe(Ⅲ) greatly promoted the agglomerating and settling of algae. The analysis of cell integrity, biochemical compositions, and fluorescence excitation-emission matrices spectra demonstrated that excess NaClO but not PAA would seriously damage the algal cells. This might be because that NaClO would directly oxidize the cell wall/membrane, while PAA mainly permeates into the cell to inactivate algae. These results suggest that Fe(Ⅱ)/PAA is an efficient strategy for algae-laden water treatment without serious algae lysis.

Anthropogenic impact on long-term riverine CODMn, BOD, and nutrient flux variation in the Pearl River Delta

In the Pearl River Delta (PRD), population growth and economic development have steadily increased the anthropogenic nutrient discharge into coastal waters. In this study, we employed the observed concentration and model reproduced runoff to quantify the interannual variation and the long-term (1985-2021) trends in riverine chemical oxygen demand (COD_Mn), biochemical oxygen demand (BOD), and nutrient fluxes. The annual COD_Mn and BOD fluxes increased slightly between 1999 and 2021. In comparison, the mean annual dissolved inorganic nitrogen (DIN) fluxes of the four eastern outlets increased significantly from 2.05 × 10⁵ t/a in 1985-1995 to 3.11 × 10⁵ t/a in 1999-2011 and then to 3.91 × 10⁵ t/a in 2014-2021. The outlets with the largest contributions to the COD_Mn, BOD, and DIN fluxes were Humen and Modaomen, which are both located near large cities. By calculating the COD_Mn fluxes upstream of the PRD, we found that the COD_Mn fluxes from downstream in the PRD increased faster than the fluxes from upstream. It follows that the increase in COD_Mn at outlets was mostly driven by the contributions of downstream major cities. In addition, the proportion of ammonia nitrogen flux in the DIN flux decreased from over 50 % to under 10 % at most outlets. This indicates that the toxicity of DIN fluxes has been mitigated. The DIN fluxes also showed a positive correlation with surface chlorophyll a and a negative correlation with bottom dissolved oxygen outside the Pearl River Estuary (PRE). This implies that the changes in phytoplankton growth and oxygen levels outside the PRE are closely linked to the variation in river-delivered nutrients, and the increasing riverine nutrient input may result in the expansion of intensified low-oxygen conditions outside the PRE.

Deactivation of cyanobacteria blooms and simultaneous recovery phosphorus through electrolysis method

A novel method for remediating eutrophic lakes through electrolysis was made possible by one titanium (Ti) mesh, which serves as a cathode and two anodes of Ti mesh coated with ruthenium (IV) oxide and iridium (IV) oxide (RuO₂-IrO₂/Ti). Once the three-electrode components RuO₂-IrO₂/Ti and Ti are stabilized, they can carry out electrolytic reaction to control cyanobacteria blooms and assist with the remediation of eutrophic water. The order of influence on the theoretical energy consumption involved in removing algae is as follows: The electrode spacing was more effective than electrode voltage, which proved more effective than electrolysis time through the orthogonal test method. Thus, an electrode spacing of 60 mm, an electrode voltage of 30 V, and an electrolysis time of 12 h are the optimal electrolysis methods used to remove cyanobacterial blooms. The strong acidic environment produced by the anode increased the concentration of hydroxyl radical (•OH) and other strong oxidizing substances, which were the main roles that made cyanobacteria bloom inactivation. The electrolysis reaction was conducive to the transformation of organophosphorus in cyanobacterial blooms to dissolved inorganic phosphorus (DIP) in water. Some DIP was most deposited on the cathode after electro-depositing enhanced the removal of P in water with the 12-h prolonged electrolysis time. Meanwhile, it was beneficial to reduce the total nitrogen (TN) and ammonia nitrogen (NH₃-N) in the water. Thus, electrolysis proved to be an effective way to the inactivation of cyanobacteria blooms and simultaneously recover P as the concentration became higher.

Threats, challenges and sustainable conservation strategies for freshwater biodiversity

Increasing human population, deforestation and man-made climate change are likely to exacerbate the negative effects on freshwater ecosystems and species endangerment. Consequently, the biodiversity of freshwater continues to dwindle at an alarming rate. However, this particular topic lacks sufficient attention from conservation ecologists and policymakers, resulting in a dearth of data and comprehensive reviews on freshwater biodiversity, specifically. Despite the widespread awareness of risks to freshwater biodiversity, organized action to reverse this decline has been lacking. This study reviews prospective conservation and management strategies for freshwater biodiversity and their associated challenges, identifying current key threats to freshwater biodiversity. Engineered nanomaterials pose a significant threat to aquatic species, and will make controlling health risks to freshwater biodiversity increasingly challenging in the future. When fish are exposed to nanoparticles, the surface area of their respiratory and ion transport systems can decline to 60% of their total surface area, posing serious health risks. Also, about 50% of freshwater fish species are threatened by climate change, globally. Freshwater biodiversity that is heavily reliant on calcium perishes when the calcium content of their environments degrades, posing another severe threat to world biodiversity. To improve biodiversity, variables such as species diversity, population and water quality, and habitat are essential components that must be monitored continuously. Existing research on freshwater biota and ecosystems is still lacking. Therefore, data collection and the establishment of specialized policies for the conservation of freshwater biodiversity should be prioritized.

Human induced fish declines in North America, how do agricultural pesticides compare to other drivers?

Numerous anthropogenic factors, historical and contemporary, have contributed to declines in the abundance and diversity of freshwater fishes in North America. When Europeans first set foot on this continent some five hundred years ago, the environment was ineradicably changed. Settlers brought with them diseases, animals, and plants via the Columbian Exchange, from the old world to the new, facilitating a process of biological globalization. Invasive species were thus introduced into the Americas, displacing native inhabitants. Timber was felled for ship building and provisioning for agriculture, resulting in a mass land conversion for the purposes of crop cultivation. As European colonization expanded, landscapes were further modified to mitigate against floods and droughts via the building of dams and levees. Resources have been exploited, and native populations have been overfished to the point of collapse. The resultant population explosion has also resulted in wide-spread pollution of aquatic resources, particularly following the industrial and agricultural revolutions. Collectively, these activities have influenced the climate and the climate, in turn, has exacerbated the effects of these activities. Thus, the anthropogenic fingerprints are undeniable, but relatively speaking, which of these transformative factors has contributed most significantly to the decline of freshwater fishes in North America? This manuscript attempts to address this question by comparing and contrasting the preeminent drivers contributing to freshwater fish declines in this region in order to provide context and perspective. Ultimately, an evaluation of the available data makes clear that habitat loss, obstruction of streams and rivers, invasive species, overexploitation, and eutrophication are the most important drivers contributing to freshwater fish declines in North America. However, pesticides remain a dominant causal narrative in the popular media, despite technological advancements in pesticide development and regulation. Transitioning from organochlorines to organophosphates/carbamates, to pyrethroids and ultimately to the neonicotinoids, toxicity and bioaccumulation potential of pesticides have all steadily decreased over time. Concomitantly, regulatory frameworks designed to assess corresponding pesticide risks in Canada and the USA have become increasingly more stringent and intensive. Yet, comparatively, habitat loss continues unabated as agricultural land is ceded to the frontier of urban development, globalized commerce continues to introduce invasive species into North America, permanent barriers in the form of dams and levees remain intact, fish are still being extracted from native habitats (commercially and otherwise), and the climate continues to change. How then should we make sense of all these contributing factors? Here, we attempt to address this issue.

Does the Kis-Balaton Water Protection System (KBWPS) Effectively Safeguard Lake Balaton from Toxic Cyanobacterial Blooms?

Lake Balaton is the largest shallow lake in Central Europe. Its water quality is affected by its biggest inflow, the Zala River. During late 20th century, a wetland area named the Kis-Balaton Water Protection System (KBWPS) was constructed in the hopes that it would act as a filter zone and thus ameliorate the water quality of Lake Balaton. The aim of the present study was to test whether the KBWPS effectively safeguards Lake Balaton against toxic cyanobacterial blooms. During April, May, July and September 2018, severe cyanobacterial blooming was observed in the KBWPS with numbers reaching up to 13 million cells/mL at the peak of the bloom (July 2018). MC- and STX-coding genes were detected in the cyanobacterial biomass. Five out of nine tested microcystin congeners were detected at the peak of the bloom with the concentrations of MC-LR reaching 1.29 µg/L; however, accumulation of MCs was not detected in fish tissues. Histopathological analyses displayed severe hepatopancreas, kidney and gill alterations in fish obtained throughout the investigated period. In Lake Balaton, on the other hand, cyanobacterial numbers were much lower; more than 400-fold fewer cells/mL were detected during June 2018 and cyanotoxins were not detected in the water. Hepatic, kidney and gill tissue displayed few alterations and resembled the structure of control fish. We can conclude that the KBWPS acts as a significant buffering zone, thus protecting the water quality of Lake Balaton. However, as MC- and STX-coding genes in the cyanobacterial biomass were detected at both sites, regular monitoring of this valuable ecosystem for the presence of cyanobacteria and cyanotoxins is of paramount importance.