Comparison of the Seasonal Variations of Synechococcus Assemblage Structures in Estuarine Waters and Coastal Waters of Hong Kong

Abstract

bSeasonal variation in the phylogenetic composition of Synechococcus assemblages in estuarine and coastal waters of Hong Kong was examined through pyrosequencing of the rpoC1 gene. Sixteen samples were collected in 2009 from two stations representing estuarine and ocean-influenced coastal waters, respectively. Synechococcus abundance in coastal waters gradually increased from 3.6 ؋ 10 3 cells ml ؊1 in March, reaching a peak value of 5.7 ؋ 10 5 cells ml ؊1 in July, and then gradually decreased to 9.3 ؋ 10 3 cells ml ؊1 in December. The changes in Synechococcus abundance in estuarine waters followed a pattern similar to that in coastal waters, whereas its composition shifted from being dominated by phycoerythrin-rich (PE-type) strains in winter to phycocyanin-only (PC-type) strains in summer owing to the increase in freshwater discharge from the Pearl River and higher water temperature. The high abundance of PC-type Synechococcus was composed of subcluster 5.2 marine Synechococcus, freshwater Synechococcus (F-PC), and Cyanobium. The Synechococcus assemblage in the coastal waters, on the other hand, was dominated by marine PE-type Synechococcus, with subcluster 5.1 clades II and VI as the major lineages from April to September, when the summer monsoon prevailed. Besides these two clades, clade III cooccurred with clade V at relatively high abundance in summer. During winter, the Synechococcus assemblage compositions at the two sites were similar and were dominated by subcluster 5.1 clades II and IX and an undescribed clade (represented by Synechococcus sp. strain miyav). Clade IX Synechococcus was a relatively ubiquitous PE-type Synechococcus found at both sites, and our study demonstrates that some strains of the clade have the ability to deal with large variation of salinity in subtropical estuarine environments. Our study suggests that changes in seawater temperature and salinity caused by the seasonal variation of monsoonal forcing are two major determinants of the community composition and abundance of Synechococcus assemblages in Hong Kong waters. Members of the Synechococcus group of widely distributed and abundant picocyanobacteria are important primary producers in the surface waters of global oceans (1). Strains of Synechococcus are both phenotypically and phylogenetically diverse and dynamic (2, 3). Based on gene markers, like the 16S rRNA gene, marine Synechococcus strains form a well-defined clade termed cluster 5 (4, 5), which is divided into 3 subclusters: 5.1, 5.2, and 5.3. Of these, subcluster 5.1 is the most abundant and diverse subcluster in marine environments and is further divided into at least 9 clades (6). The high genetic diversity of Synechococcus is reflected in the ecogeographic and temporal distribution of different ecotypes. Subcluster 5.1 clade I mainly dominates in temperate mesotrophic ocean waters, while clade II is mainly present in offshore, continental shelf, and oligotrophic warm waters (4, 7). Subcluster 5.2 Synechococcus strains are phycocyanin-enriched (PC-type) euryhaline s...

Phylogeography and pigment type diversity of Synechococcus cyanobacteria in surface waters of the northwestern pacific ocean

“…). These taxa were previously found to be abundant in the Hong Kong estuarine waters (Xia et al ., ), suggesting that they have a high nutrient requirement and are possibly halotolerant, as it is the case for S5.2 (Chen et al ., ; Dufresne et al ., ).…”

“…Amplification of the rpoC1 gene sequences was performed as previously described (Mühling et al ., ). The first round of PCR used the primer rpoC1 ‐N5 and the C‐terminal primer rpoC1 ‐C, and the PCR products were used as templates for a second round of PCR with primer rpoC1 −39F (5′‐adaptor A + barcode + GGNATNGTNTGYGAGCGYTG) and rpoC1 −462R (5′‐adaptor B + CGYAGRCFCTTGRTCAGCTT (Mühling et al ., ; Xia et al ., ). PCR products were gel‐purified using the Qiaquick gel purification kit, as described by the manufacturer (Qiagen, Germany).…”

“…The phylotype of each reference sequence is listed in Supporting Information Table S4. Since the similarity of sequences within each lineage ranged from 90% to 100% (Supporting Information Table S5), sequences displaying less than 90% identical to the reference sequences were assigned as unclassified (Xia et al ., ). The relative abundance of each lineage was calculated and used to generate a heatmap using HemI (Deng et al ., ), then square root transformed in order to perform average linkage clustering using Pearson correlation matrices.…”

Dynamics of Bacterial Community Diversity and Structure in the Terminal Reservoir of the South-To-North Water Diversion Project in China

“…Some researchers have reported that the abundance and biomass of Synechococcus sp. showed strong seasonal relationships with temperature [28], and this genera provided important sources of organic carbon and nutrients for the summer food web [29]. This is a health concern in some cases, as Synechococcus blooms can produce harmful toxins [30][31][32].…”

Seasonality of Coliform Bacteria Detection Rates in New Jersey Domestic Wells

“…Seasonal differences in surface water and stormwater coliform concentrations have been observed by many investigators (e.g., Hunter and McDonald ; Hathaway et al ; Duris et al ; Meals et al ). Such seasonality is undoubtedly a universal pattern for mesophilic organisms in all waterbodies in temperate climates (Giovannoni and Vergin ; Ran et al ; Xia et al ).…”