Dynamics and Distribution of Marine Synechococcus Abundance and Genotypes during Seasonal Hypoxia in a Coastal Marine Ranch

Abstract

Marine Synechococcus are an ecologically important picocyanobacterial group widely distributed in various oceanic environments. Little is known about the dynamics and distribution of Synechococcus abundance and genotypes during seasonal hypoxia in coastal zones. In this study, an investigation was conducted in a coastal marine ranch along two transects in Muping, Yantai, where hypoxic events (defined here as the dissolved oxygen concentration <3 mg L−1) occurred in the summer of 2015. The hypoxia occurred in the bottom waters from late July and persisted until late August. It was confined at nearshore stations of the two transects, one running across a coastal ranch and the other one outside. During this survey, cell abundance of Synechococcus was determined with flow cytometry, showing great variations ranging from 1 × 104 to 3.0 × 105 cells mL−1, and a bloom of Synechococcus occurred when stratification disappeared and hypoxia faded out outside the ranch. Regression analysis indicated that dissolved oxygen, pH, and inorganic nutrients were the most important abiotic factors in explaining the variation in Synechococcus cell abundance. Diverse genotypes (mostly belonged to the sub-clusters 5.1 and 5.2) were detected using clone library sequencing and terminal restriction fragment length polymorphism analysis of the 16S–23S rRNA internal transcribed spacer region. The richness of genotypes was significantly related to salinity, temperature, silicate, and pH, but not dissolved oxygen. Two environmental factors, temperature and salinity, collectively explained 17% of the variation in Synechococcus genotype assemblage. With the changes in population composition in diverse genotypes, the Synechococcus assemblages survived in the coastal hypoxia event and thrived when hypoxia faded out.

The “Dark Side” of Picocyanobacteria: Life as We Do Not Know It (Yet)

“…Different molecular techniques with increasing descriptive power and reliability are now in common use in field studies. For example: clone library sequencing (e.g., [ 108 ]), terminal restriction fragment length polymorphism analysis of the 16S–23S rRNA internal transcribed spacer region (e.g., [ 109 ]), specific gene markers analysis by qPCR ( rpoC1 , petB , cpcBA, cpeBA ecc.) (e.g., [ 27 , 110 , 111 , 112 ]), as well as metagenomic (recruitment) analysis [ 22 , 23 , 25 , 28 ].…”

Spatio-Temporal Variation of Synechococcus Assemblages at DNA and cDNA Levels in the Tropical Estuarine and Coastal Waters

“…Synechococcus cell abundance ranged from 10 3 to 10 4 cells/ml at the coastal stations ( Figure 2A ). It is lower than those in temperate or subtropic coastal waters, such as Bohai coastal marine ranch ( Li et al, 2021 ), Hong Kong coastal waters ( Liu et al, 2014 ), coastal western subtropical Pacific ( Tsai et al, 2006 ), and Southern California coast ( Nagarkar et al, 2021 ). However, it is consistent with those in other tropical coastal waters, such as the equatorial eastern Indian Ocean ( Wei et al, 2019 ) and coastal waters of the Philippines (Southeast China Sea) ( Agawin et al, 2003 ).…”

“…Marine Synechococcus exhibits high genetic diversity ( Farrant et al, 2016 ; Xia et al, 2019 ). Gene markers, such as the 16S rRNA gene ( Mackey et al, 2017 ), the 16S–23S internally transcribed spacer (ITS) ( Li et al, 2021 ; Nagarkar et al, 2021 ), the RNA polymerase gene ( rpo C1) ( Kent et al, 2019 ; Wang et al, 2021a ), the nitrate reductase gene ( nar B) ( Robidart et al, 2012 ), the cytochrome b 6 gene ( pet B) ( Mazard et al, 2012 ), and the ribulose–1,5–bisphosphate carboxylase oxygenase gene ( rbc L) ( Paerl et al, 2012 ), have been commonly applied to study the genetic diversity of Synechococcus . Among these gene markers, ITS is the locus with the most sequences available for primer design ( Ahlgren and Rocap, 2012 ).…”

Response of a Coastal Microbial Community to Olivine Addition in the Muping Marine Ranch, Yantai

“…The natural seawater used in this experiment was from the Muping Marine Ranch, Yantai, China ( Figure 1 ), where the maximum depth is ∼22 m, with an averaged tidal current rate of ∼0.5 m s –1 ( Lu et al, 2015 ; Li et al, 2021 ). In this ranch, the abundance and diversity of the bacterial community have been altered greatly by anthropogenic activities and aquaculture ( Li et al, 2021 ).…”

“…The natural seawater used in this experiment was from the Muping Marine Ranch, Yantai, China ( Figure 1 ), where the maximum depth is ∼22 m, with an averaged tidal current rate of ∼0.5 m s –1 ( Lu et al, 2015 ; Li et al, 2021 ). In this ranch, the abundance and diversity of the bacterial community have been altered greatly by anthropogenic activities and aquaculture ( Li et al, 2021 ). Before the experiment, the seawater was collected in the morning (8:00 to 10:00 a.m.) of August 10, 2019 from the surface (∼1-m depth) and bottom layers (∼1 m above the seabed) of the ranch with a Niskin bottle (Sea–Bird).…”