Temporal and vertical variability of bacterioplankton composition in Chipana bay (21º20’S) in a coastal upwelling system of northern Chile: A fluorescence in situ hybridization approach

Cristy Medina-Armijo,Rubén Moraga-Mamani,Edgardo Santander-Pulgar

doi:10.22370/rbmo.2020.55.1.2375

Cristy Medina-Armijo, Rubén Moraga-Mamani + Show 1 more

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https://doi.org/10.22370/rbmo.2020.55.1.2375

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Abstract

The bacterioplankton in the upwelling systems associated with oceanographic condition of the oxygen minimum zone (OMZ) of the Eastern tropical South Pacific was studied through visualization and enumeration with fluorescent in situ hybridization (FISH). Six different taxonomic groups were studied (Alpha, Beta, Gamma-proteobacteria, Cytophaga-flavobacterium and the domains Archaea and Bacteria). The analysis showed a greater predominance of the Bacteria domain (20 to 68% of hybridized cells) over Archaea (2 to 18% of hybridized cells). The specific groups showed that Cytophaga-flavobacterium, Alpha-proteobacteria and Gamma-proteobacteria are more abundant in the surface layer. Gamma-proteobacteria is also most abundant in the deep oxycline and, Beta-proteobacteria is the group with the lowest registered abundances. Changes in the vertical distribution of the bacterial community in the water column between OMZ and on oxycline were observed through NMDS. This change is a product of a shift in the abundances of the specific groups Cytophaga-flavobacterium and Gamma-proteobacteria in the surface layers, due to low concentration of chlorophyll-a caused by periods of relaxation in the upwelling.

Highlights

The Eastern South Pacific (ESP) is one of the most productive regions of the world’s ocean (Wyrtki 1966, Ryther 1969, Cushing 1990)
The wind persistently showed positive values, resulting in an upwelling index (UI) that revealed the prevalence of conditions that favor the occurrence of coastal upwelling during both, warm and cold events
The visualization and enumeration of bacterial communities found in this study resemble those routinely found in a variety of pelagic marine environments using fluorescent in situ hybridization (FISH) methods

Summary

Introduction

The Eastern South Pacific (ESP) is one of the most productive regions of the world’s ocean (Wyrtki 1966, Ryther 1969, Cushing 1990) This oceanic region belongs to the Humboldt Current Systems (HCS), which is characterized by events of coastal upwelling, driving nutrient-rich water into the surface layer of the ocean. Due to a low ventilation and high primary production, the water column is characterized by a permanent oxygen minimum zone (OMZ), which is located between 100-500 m depth (Herrera & Escribano 2006, Palma et al 2006) This OMZ is a permanent feature, forming ecosystems with unique characteristics where chemical and redox gradients are intense, inducing vertical division and greater bacterial richness (Stevens & Ulloa 2008). Bacterioplankton is a major component of the biomass in oceanic oligotrophic systems (Azam et al 1983, Cho & Azam 1988, Amann et al 1990, 1991; Amann 1995, Binder et al 1996, Carlson et al 1996), and the role of these organisms in biogeochemical cycling of carbon, nitrogen, and sulfur is critical for the function of the ocean’s ecosystem (Cole et al 1988, Ducklow & Carlson 1992)

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