Monitoring bacterial composition and assemblage in the Gulf of Corcovado, southern Chile: Bacteria associated with harmful algae

So Fujiyoshi; Kyoko Yarimizu; Gonzalo Fuenzalida; Marco Campos; Joaquin-Ignacio Rilling; Jacquelinne J Acuña; Pedro Calabrano Miranda; Emma-Karin Cascales; Ishara Perera; Oscar Espinoza-González; Leonardo Guzmán; Milko A Jorquera; Fumito Maruyama

doi:10.1016/j.crmicr.2023.100194

Monitoring bacterial composition and assemblage in the Gulf of Corcovado, southern Chile: Bacteria associated with harmful algae

Curr Res Microb Sci. 2023 May 27:4:100194. doi: 10.1016/j.crmicr.2023.100194. eCollection 2023.

Affiliations

¹ Microbial Genomics and Ecology, The IDEC Institute, Hiroshima University, 1-3-2 Kagamiyama, Higashi-Hiroshima City, Hiroshima 739-8511, Japan.
² Centro de Estudios de Algas Nocivas (CREAN), Instituto de Fomento Pesquero (IFOP), Padre Harter 574, Puerto Montt 5480000, Chile.
³ Departamento de Ciencias Básicas, Facultad de Ciencias, Universidad Santo Tomás, Buena Vecindad #91, Puerto Montt, Chile.
⁴ Laboratorio de Ecología Microbiana Aplicada (EMAlab), Departamento de Ciencias Quimicas y Recursos Naturales, Universidad de La Frontera, Ave. Francisco Salazar 01145, Temuco 4811230, Chile.

Abstract

Harmful Algal Blooms (HABs) have caused damage to the marine environment in Isla San Pedro in the Gulf of Corcovado, Chile. While rising water temperature and artificial eutrophication are the most discussed topics as a cause, marine bacteria is a recent attractive parameter as an algal bloom driver. This study monitored algal and bacterial compositions in the water of Isla San Pedro for one year using microscopy and 16S rRNA metabarcoding analysis, along with physicochemical parameters. The collected data were analyzed with various statistical tools to understand how the particle-associated bacteria (PA) and the free-living (FL) bacteria were possibly involved in algal blooms. Both FL and PA fractions maintained a stable bacterial composition: the FL fraction was dominated by Proteobacteria (α-Proteobacteria and γ-Proteobacteria), and Cyanobacteria dominated the PA fraction. The two fractions contained equivalent bacterial taxonomic richness (c.a. 8,000 Operational Taxonomic Units) and shared more than 50% of OTU; however, roughly 20% was exclusive to each fraction. The four most abundant algal genera in the Isla San Pedro water were Thalassiosira, Skeletonema, Chaetoceros, and Pseudo-nitzchia. Statistical analysis identified that the bacterial species Polycyclovorans algicola was correlated with Pseudo-nitzschia spp., and our monitoring data recorded a sudden increase of particle-associated Polycyclovorans algicola shortly after the increase of Pseudo-nitzschia, suggesting that P. algicola may have regression effect on Pseudo-nitzschia spp. The study also investigated the physicochemical parameter effect on algal-bacterial interactions. Oxygen concentration and chlorophyll-a showed a strong correlation with both FL and PA bacteria despite their assemblage differences, suggesting that the two groups had different mechanisms for interacting with algal species.

Keywords: Bacteria-algae-physicochemical interaction; Free-living and particle-associated bacteria; Harmful algal bloom; Network analysis.