3 Sep 2025

Acute Toxicity of Carbon Nanotubes, Carbon Nanodots, and Cell-Penetrating Peptides to Freshwater Cyanobacteria

Abstract: Synthetic non-metallic nanoparticles have been explored to treat harmful algal blooms, but their strain-specific algicidal activities have been rarely investigated. Three batches of CNDs were prepared in-house using glucose or chloroform and methanol as the substrate and one batch of single-walled CNTs. The axenic laboratory culture of each cyanobacterial strain was exposed to an NMNP at two dosage levels for 48 h, followed by measurement of five endpoints. The endpoints were optical density at 680 nm for chlorophyll-a estimation, OD at 750 nm for cell density, instantaneous pigment fluorescence emission after being excited with 450 nm blue light for chlorophyll-a or 620 nm red light for phycocyanin, and quantum yield for photosynthesis efficiency of photosystem II. The results indicate the acute toxicity was strain-, NMNP type-, dosage-, and endpoint-dependent. The two benthic strains were more resistant to NMNP treatment. SWCNTs and fraction A14 of CND-G were more toxic than CND-G and CND-C/M. The CPP was the least toxic. The high dose generally caused more severe impairment. OD750 and OD680 were more sensitive and QY was the least sensitive. The strain dependence of toxicity suggested the potential application of these NMNPs as a target-specific tool for mitigating harmful cyanobacterial blooms.

7 Aug 2024

A Broadscale Assessment of Sentinel-2 Imagery and the Google Earth Engine for the Nationwide Mapping of Chlorophyll a

Abstract: Harmful algal blooms degrade water quality and can adversely impact human and wildlife health. Monitoring these at scale is difficult due to the lack of coincident data. Additionally, traditional field collection methods are labor- and cost-prohibitive, resulting in disparate data collection in capable of capturing the physical and biological variations within waterbodies or regions. This research attempts to alleviate this by leveraging large, public, water quality databases and open-access Google Earth Engine-derived Sentinel-2 imagery to evaluate the practical usability of four common chlorophyll a algorithms as a proxy for detecting and mapping algal blooms nationwide. Chlorophyll a data were aggregated from spatially diverse sites across the continental US between 2019 and 2022. The 2BDA and the NDCI algorithms were the most viable for broadscale mapping of chlorophyll a, which performed moderately well, encompassing highly diverse spatial, temporal, and physical conditions. The most compatible field data acquisition method was the chlorophyll a, water, trichromatic method, uncorrected. Resulting data indicate the feasibility of utilizing band ratio algorithms for broadscale detection and mapping of chlorophyll a as a proxy for HABs, which is valuable when coincident data are unavailable or limited.