Aerosolized Cyanobacterial Harmful Algal Bloom Toxins: Microcystin Congeners Quantified in the Atmosphere

Life Course Exposure to Cyanobacteria and Amyotrophic Lateral Sclerosis Survival

Cyanobacterial harmful algal blooms (cyanoHABs) occur worldwide and can cause ingestion and inhalation exposure to microcystin and other potent toxins. This study develops life course exposure measures for cyanobacteria for application in population studies and then associates these measures with the survival of individuals with amyotrophic lateral sclerosis (ALS). The exposure measures utilize an individual's residence history, date of disease onset, and satellite data from the Cyanobacteria Assessment Network. Residence duration for selected exposure windows referenced to disease onset date was used to weight cyanobacteria concentrations in water bodies within 0.25 to 10 km of each residence. Different concentration metrics, buffer sizes, and exposure windows were evaluated. The 2.5 and 5 km buffers best balanced the likelihood and plausibility of exposure while still resolving exposure contrasts. Over their lifetime, most study participants lived within 5 km of cyanobacteria blooms, and the exposure was associated with up to 0.89 years shorter survival, with significant interactions for individuals reporting swimming, fishing, and private wells. Our findings suggest a new and modifiable risk factor for ALS survival, and a need to confirm exposures and epidemiological findings. These cyanoHAB exposure estimates can facilitate population studies that can discover new relationships with neurodegenerative and other diseases.

CyanoHABs and CAPs: assessing community-based monitoring of PM2.5 with regional sources of pollution in rural, northeastern North Carolina

Underserved rural communities in northeastern North Carolina (NC), surrounding the Albemarle Sound, have faced degraded environmental quality from various sources of air and water pollution. However, access to local air quality data is regionally scarce due to a lack of state-run monitoring stations, which has motivated local community science efforts. In January 2022, we co-developed a community-led study to investigate the relationship between fine particulate matter (PM2.5) and sources of regional air pollution, with a specific focus on previously identified emissions from cyanobacterial harmful algal blooms (CyanoHABs). Using low-cost PurpleAir air quality sensors to quantify PM2.5 mass, satellite-derived indicators of CyanoHABs, and other publicly available atmospheric and meteorological data, we assessed environmental drivers of PM2.5 mass in the airshed of the Albemarle Sound estuary during 2022-2023. We found that bias-corrected PurpleAir PM2.5 mass concentrations aligned with composite data from the three nearest federal reference equivalent measurements within 1 μg m-3 on average, and that the temporal variation in PM2.5 was most closely associated with changes in criteria air pollutants. Ultimately, satellite-based indicators of CyanoHABs (Microcystis spp. equivalent cell counts and bloom spatial extent) were not strongly associated with ambient/episodic increases in PurpleAir PM2.5 mass during our study period. For the first time, we provide local PM2.5 measurements to rural communities in northeastern NC with an assessment of environmental drivers of PM2.5 pollution events. Additional compositional analyses of PM2.5 are warranted to further inform respiratory risk assessments for this region of NC. Despite the lack of correlation between CyanoHABs and PM2.5 observed, this work serves to inform future studies that seek to employ widely available and low-cost approaches to monitor both CyanoHAB aerosol emissions and general air quality in rural coastal regions at high spatial and temporal resolutions.

Bioaerosol Characterization with Vibrational Spectroscopy: Overcoming Fluorescence with Photothermal Infrared (PTIR) Spectroscopy

Aerosols containing biological material (i.e., bioaerosols) impact public health by transporting toxins, allergens, and diseases and impact the climate by nucleating ice crystals and cloud droplets. Single particle characterization of primary biological aerosol particles (PBAPs) is essential, as individual particle physicochemical properties determine their impacts. Vibrational spectroscopies, such as infrared (IR) or Raman spectroscopy, provide detailed information about the biological components within atmospheric aerosols but these techniques have traditionally been limited due to the diffraction limit of IR radiation (particles >10 μm) and fluorescence of bioaerosol components overwhelming the Raman signal. Herein, we use photothermal infrared spectroscopy (PTIR) to overcome these limitations and characterize individual PBAPs down to 0.18 μm. Both optical-PTIR (O-PTIR) and atomic force microscopy-PTIR (AFM-PTIR) were used to characterize bioaerosol particles generated from a cyanobacterial harmful algal bloom (cHAB) dominated by Planktothrix agardhii. PTIR spectra contained modes consistent with traditional Fourier transform infrared (FTIR) spectra for biological species, including amide I (1630-1700 cm-1) and amide II (1530-1560 cm-1). The fractions of particles containing biological materials were greater in supermicron particles (1.8-3.2 μm) than in submicron particles (0.18-0.32 and 0.56-1.0 μm) for aerosolized cHAB water. These results demonstrate the potential of both O-PTIR and AFM-PTIR for studying a range of bioaerosols with vibrational spectroscopy.

Fate of a toxic Microcystis aeruginosa bloom introduced into a subtropical estuary from a flow-managed canal and management implications

The Caloosahatchee Estuary in southwest Florida, USA, is regularly subject to the introduction of toxic Microcystis aeruginosa blooms, often originating from the eutrophic Lake Okeechobee via the C-43 Canal. The focus of this study was to determine the responses of one of these introduced blooms to progressively elevated salinity levels as the bloom water mass moved through the estuary. In the upper estuary, salinities were freshwater, and surface blooms of large colonies of M. aeruginosa were observed, along with peak microcystin toxin concentrations up to 107 μg L-1, all in the particulate fraction. In the mid-estuary, salinity levels increased to 2-6, and surface blooms were again observed, with peak microcystin concentrations up to 259 μg L-1, however, significant levels of extracellular toxin were also observed (i.e., 17.8 μg L-1), suggesting a level of osmotic stress on M. aeruginosa. In the lower estuary, salinities ranged from 6 to 25 and very few viable M. aeruginosa colonies were observed, but significant levels of extracellular microcystin (i.e., 0.5 μg L-1) were present throughout the water column. It is noteworthy that average total microcystin concentrations in the water column (i.e., particulate + extracellular) remained constant throughout the movement of the bloom water mass during its transit through the estuary, revealing the negligible rate of microcystin degradation during the ten-day transit. The results also provide insights into the changes in the distribution of particulate and extracellular microcystin along the salinity gradient, which has implications for management of risks for ecosystem and human health, and how these risks may be affected by management of releases from three water control structures in the C-43 Canal. Discharge rates from the water control structures play major roles in the rate of movement of blooms through the C-43 Canal-Caloosahatchee Estuary ecosystem. The potential implications of discharge regulation for the management of M. aeruginosa in the ecosystem are discussed from the perspectives of blooms of allochthonous and autochthonous origin.

Effectiveness of ozone nanobubble treatments on high biomass cyanobacterial blooms: A mesocosm experiment and field trial

Cyanobacterial harmful algae blooms (cyanoHABs) are a global threat to water resources, and lake managers need effective strategies to suppress or control them. Algaecides may have negative environmental impacts, and their use is becoming restricted. Nanobubble ozone technology (NBOT) is an emerging water treatment option with potentially fewer negative impacts. We assessed the effectiveness of NBOT in treating Planktothrix cyanoHAB from Grand Lake St Marys (GLSM, Ohio USA) in a mesocosm (2,000L) experiment and two 4-week trials in a GLSM embayment (Sunset Beach, SBE; ∼4.7∗107 L). In mesocosms, the medium (1.21 ± 0.08 ozone to dissolved organic carbon ratio, O3:DOC) and high (2.04 ± 0.07 O3:DOC) doses decreased both chlorophyll a (chl-a) and phycocyanin by 98-99% and microcystins by 62% and 92%, respectively. The low dose (0.68 ± 0.05 O3:DOC) decreased chl-a and phycocyanin by over 70%. No effect was observed for chl-a nor microcystins in both oxygen-only nanobubble mesocosm treatments and the SBE NBOT trial. The average O3:DOC at SBE was less than the low NBOT mesocosm experiment dose, and the percentage of water treated was lower. DOC chemistry, as indicated by SUVA254, was more oxidized at the NBOT outlet than the inlet in the SBE trial, suggesting interaction with ozone. However, no differences were observed 3m from the outlet, indicating minimal treatment reach. The mesocosm experiment highlighted NBOT's ability to control cyanoHABs, but the limited effectiveness of NBOT at SBE was likely due to high cyanobacteria biomass and DOC at the onset of treatment, low O3:DOC, and low percentage of lake water instantaneously treated.

Comparative toxic effect of tire wear particle-derived compounds 6PPD and 6PPD-quinone to Chlorella vulgaris

N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), a widely used antioxidant in rubber products, and its corresponding ozone photolysis product N-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine-quinone (6PPD-Q), have raised public concerns due to their environmental toxicity. However, there is an existing knowledge gap on the toxicity of 6PPD and 6PPD-Q to aquatic plants. A model aquatic plant, Chlorella vulgaris (C. vulgaris), was subjected to 6PPD and 6PPD-Q at concentrations of 50, 100, 200, and 400 μg/L to investigate their effects on plant growth, photosynthetic, antioxidant system, and metabolic behavior. The results showed that 6PPD-Q enhanced the photosynthetic efficiency of C. vulgaris, promoting growth of C. vulgaris at low concentrations (50, 100, and 200 μg/L) while inhibiting growth at high concentration (400 μg/L). 6PPD-Q induced more oxidative stress than 6PPD, disrupting cell permeability and mitochondrial membrane potential stability. C. vulgaris responded to contaminant-induced oxidative stress by altering antioxidant enzyme activities and active substance levels. Metabolomics further identified fatty acids as the most significantly altered metabolites following exposure to both contaminants. In conclusion, this study compares the toxicity of 6PPD and 6PPD-Q to C. vulgaris, with 6PPD-Q demonstrating higher toxicity. This study provides valuable insight into the risk assessment of tire wear particles (TWPs) derived chemicals in aquatic habitats and plants.

Aerosolized algal bloom toxins are not inert

Harmful algal blooms (HABs) are projected to become increasingly prevalent, extending over longer periods and wider geographic regions due to the warming surface ocean water and other environmental factors, including but not limited to nutrient concentrations and runoff for marine and freshwater environments. Incidents of respiratory distress linked to the inhalation of marine aerosols containing HAB toxins have been documented, though the risk is typically associated with the original toxins. However, aerosolized toxins in micrometer and submicrometer particles are vulnerable to atmospheric processing. This processing can potentially degrade HAB toxins and produce byproducts with varying potencies compared to the parent toxins. The inhalation of aerosolized HAB toxins, especially in conjunction with co-morbid factors such as exposure to air pollutants from increased commercial activities in ports, may represent a significant exposure pathway for a considerable portion of the global population. Understanding the chemistry behind the transformation of these toxins can enhance public protection by improving the existing HAB alert systems.