Sargassum Influence on Coastal Bioaerosol Microbiota

NOHHYEON KWAK, Shahar Tsameret, Mahdis Sobhanian, Brittany Mc Intyre, Helena Solo-Gabriele, Jiayu Li, University of Miami

     Abstract Number: 226
     Working Group: Bioaerosols

Abstract
The brown algae of the genus, Sargassum, float in the open ocean, forming large free-floating mats. Since 2011, unprecedented blooms of pelagic Sargassum have created severe socioeconomic and ecological problems, leading to significant tourism losses (estimated at $2.7 billion in Florida in 2018) and potential public health threats. Notably, decaying Sargassum can harbor pathogenic bacteria like Vibrio and Pseudomonas; these microbes, along with largely unknown associated microbial communities, can be released into the air within bioaerosols during decomposition. Characterizing the composition of these bioaerosols is crucial for assessing pathogenic disease transmission risks. In this work, we used molecular-based analysis for bacterial sequencing to identify microbes included in bioaerosols and other environment samples.

We collected samples representing four types of environmental samples – seawater, beach sand, air (bioaerosols), and Sargassum from a coastal area. Bioaerosols were collected using a swirling aerosol collector (Biosampler®, SKC Inc.). Microbial community structure and diversity across these sample types were compared using 16S rRNA gene amplicon sequencing, complemented by qPCR to assess bacterial load.

Quantitative PCR (qPCR) analysis indicated that microbial loads (based on 16S rRNA gene copy numbers) were substantially lower in bioaerosol samples compared to the other environmental matrices. In contrast, Sargassum biomass harbored the highest microbial load per unit mass, followed by sand and then seawater samples. However, bioaerosol samples exhibited the highest Operational Taxonomic Units (OTUs) richness (6,415 unique OTUs), with 3.2% of these OTUs also detected in the Sargassum samples. High microbial variation was observed across sample types, with 18,200 OTUs, yet only 17 OTUs were universally shared among air, sand, seawater, and Sargassum.

For general microbes, the majority of microbes identified in bioaerosols originate from the marine environment (OM60(NOR5)clade, Marinomonas, and Alteromonas), with additional contributions from sand sources (Nocardioides and Lysobacter). These findings suggest that the rich microbial diversity in bioaerosols is shaped by multiple environmental origins.

Potential pathogenic microbes such as Vibrio and Pseudomonas were detected in bioaerosol samples. Vibrio exhibited high relative abundance in Sargassum, suggesting a possible transmission pathway from Sargassum to the atmosphere. In contrast, Pseudomonas showed higher relative abundance in beach sand, indicating that wind-driven sand erosion may contribute to its presence in bioaerosols.