Adenosine triphosphate (ATP) is the primary energy storage molecule in metabolic pathways. It is common in marine studies to use particulate ATP (PATP) concentrations as representative of microbial biomass. However, there is growing evidence from culture studies, models, and transcriptional data that PATP concentration varies across microbes and conditions, thus compromising interpretations in environmental settings. Importantly, there is a lack of open ocean studies assessing variations in PATP concentrations and thus a deficiency of information on the key biogeochemical drivers for variability in microbial PATP independent of biomass. In sampling the U.S. GO-SHIP P06E zonal transect (32.5°S) across the eastern South Pacific, from the subtropical gyre to the upwelling waters off Chile, we conducted the first comprehensive transect survey quantifying PATP. PATP concentrations increased toward the upwelling region of the transect, but varied vertically when normalized against three measures of biomass: particulate phosphorus, microbial abundance, and microbial biovolume. Generally, greater biomass-normalized PATP concentrations were observed below the deep chlorophyll maximum. Subdividing the P06E transect into four biogeochemical regimes highlighted distinct metabolic strategies used by microbes. Between these regimes, we found PATP concentrations were representative of biomass in upper surface waters. However, below the deep chlorophyll maximum we observed higher biomass normalized PATP concentrations that we hypothesize were due to less availability of energy sources in those subeuphotic zone waters and abundances of chemoautotrophs in the microbial community. This finding suggests that stored energy was more important for these deeper microbes.

Harmful algal blooms (HABs) can generate toxins that can be aerosolized and negatively impact human health through inhalation. HABs are often found in waterways near residences, therefore, aerosolized HAB toxins can potentially affect both indoor and outdoor air quality. Given that HABs are predicted to increase worldwide, effective mitigation strategies are needed to prevent the inhalation of aerosolized HAB toxins. In this work, we characterized both the particle filtration efficiency using particle sizing instruments as well as the mass concentration of different congeners of aerosolized microcystin (MC) toxins that penetrate through commercially available face masks and air conditioner (AC) filters. Particles were generated from cultures of the toxinproducing cyanobacteria Microcystis aeruginosa. Hydrophobic congeners of microcystin including MC-LF and MC-LW were enriched in aerosols compared to water, with MC-LR being the most abundant, which has implications for the toxicity of inhalable particles generated from HAB-contaminated waters. Particle transmission efficiencies and toxin filtration efficiencies scaled with the manufacturer-provided filter performance ratings. Up to 80% of small, microcystin-containing aerosols were transmitted through AC filters with low filter performance ratings. In contrast, both face masks as well as AC filters with high filter performance ratings

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We optimized a high throughput method to quantify turnover rates of adenosine triphosphate (ATP), adenosine diphosphate (ADP), and adenosine monophosphate (AMP) in marine microbes from simultaneous measures of the respective stocks and phosphorylation rates. We combined a microbial adenylate extraction method using boiling 20 mM Tris buffer with purification and analysis by high pressure liquid chromatography optimized to quantify these intracellular adenylate concentrations in marine microbes. Additionally, we incorporated radiolabeled phosphate (32Pi) incubations to quantify phosphorus (P) uptake rates and the phosphorylation rates for these adenylate compounds in microbial cells. With this method, we can directly assess the variations in microbial growth rates, metabolic turnover rates, energy charge, and adenylate storage. We applied and validated this method application with environmental samples from Biscayne Bay, Florida, and quantified adenylate turnover times of 12, 15, and 73 min, for ATP, ADP, and AMP, respectively. Future incorporation of this method into experiments and geographic surveys across marine environments will allow for direct assessments of changes in microbial metabolic activity in relation to other ecological variables.