Unicellular Cyanobacteria Are Important Components of Phytoplankton Communities in Australia’s Northern Oceanic Ecoregions

Abstract

The tropical marine environments of northern Australia encompasses a diverse range of geomorphological and oceanographic conditions and high levels of productivity and nitrogen fixation. However, efforts to characterize phytoplankton assemblages in these waters have been restricted to studies using microscopic and pigment analyses, leading to the current consensus that this region is dominated by large diatoms, dinoflagellates, and the marine cyanobacterium Trichodesmium. During an oceanographic transect from the Arafura Sea through the Torres Strait to the Coral Sea, we characterized prokaryotic and eukaryotic phytoplankton communities in surface waters using a combination of flow cytometry and Illumina based 16S and 18S ribosomal RNA amplicon sequencing. Similar to observations in other marine regions around Australian, phytoplankton assemblages throughout this entire region were rich in unicellular picocyanobacterial primary producers while picoeukaryotic phytoplankton formed a consistent, though smaller proportion of the photosynthetic biomass. Major taxonomic groups displayed distinct biogeographic patterns linked to oceanographic and nutrient conditions. Unicellular picocyanobacteria dominated in both flow cytometric abundance and carbon biomass, with members of the Synechococcus genus dominating in the shallower Arafura Sea and Torres Strait where chlorophyll a was relatively higher (averaging 0.4 ± 0.2 mg m-3), and Prochlorococcus dominating in the oligotrophic Coral Sea where chlorophyll a averaged 0.13 ± 0.07 mg m-3. Consistent with previous microscopic and pigment-based observations, we found from sequence analysis that a variety of diatoms (Bacillariophyceae) exhibited high relative abundance in the Arafura Sea and Torres Strait, while dinoflagellates (Dinophyceae) and prymnesiophytes (Prymnesiophyceae) were more abundant in the Coral Sea. Ordination analysis identified temperature, nutrient concentrations and water depth as key drivers of the region’s assemblage composition. This is the first molecular and flow cytometric survey of the abundance and diversity of both prokaryotic and picoeukaryotic phytoplankton in this region, and points to the need to include the picocyanobacterial populations as an essential oceanic variable for sustained monitoring in order to better understand the health of these important coastal waters as global oceans change.

Diatom Biogeography, Temporal Dynamics, and Links to Bacterioplankton across Seven Oceanographic Time-Series Sites Spanning the Australian Continent

“…In each of these examples, the bacterial partner is a member of the Bacteroidetes phylum, which is widely distributed in the marine environment and can degrade complex polysaccharides, which represent a significant component of organic matter released by diatom. Their ability to degrade complex organic matter molecules and the fact that these correlations have repeatedly been observed in several time-series further suggest that those specific taxa may have evolve to specialise and thrive in a diatom-dominated bloom event environment [58,60,61]. Other important correlations identified within our dataset involved the siderophore-producing bacteria Idiomarina sp.…”

An Insight Into Detection Pathways/Biosensors of Highly Infectious Coronaviruses

“…In this way, pyro-phosphate or fluorescence can be monitored to tackle the shortcoming of the endpoint detection [ 23 ]. Pei Huang et al [ 25 ] developed a nucleic acid visualization method by combining the RT-LAMP technique with the vertical flow visualization strip (RT-LAMP-VF) technique to diagnose MERS-CoV (Fig. 4 ).…”

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“…Cyanobacteria are an ancient group of autotrophic bacteria living both in freshwater and marine environments and constituting an important component of the primary producers [1,2]. Mass populations of toxic cyanobacteria represent a global phenomenon, and the recent recognition that incidences of blooms may increase significantly under climate change serves to reinforce further the seriousness of the potential risks to human health [3].…”

“…This study represents the first attempt focusing on culture-independent studies of cyanobacteria from Danube Delta shallow lakes. Therefore, we aimed to: (1) find the best methods for extraction of high-quality DNA using different preservation protocols and several commercial kits, and the lab-made potassium ethyl xanthogenate extraction buffer (XS buffer) and (2) to optimize a PCR protocol for 16S ribosomal RNA gene amplification.…”

“…Electrophoresis gel (2 % agarose, 1× TBE buffer, dyed with pegGREEN directly in the gel, ran at 120V for 50') performed with MangoTaq and 20 µL PCR product (expected amplicon size was 782 bp corresponding to the 16sRNA region specific for cyanobacteria) and using the optimized PCR protocol with BSA (Figure7c). Random eDNA from lakes sampled in autumn(1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11) and positive control DNA of M. aeruginosa PCC 7806 were used for tests. PCR product was amplified in all the samples, with the mention that in 11 a very thin band was noted meaningless DNA; also unspecific bands are present.…”