Data Descriptor: Systematic, continental scale temporal monitoring of marine pelagic microbiota by the Australian Marine Microbial Biodiversity Initiative

© 2018 Author(s). Sustained observations of microbial dynamics are rare, especially in southern hemisphere waters. The Australian Marine Microbial Biodiversity Initiative (AMMBI) provides methodologically standardized, continental scale, temporal phylogenetic amplicon sequencing data describing Bacteria, Archaea and microbial Eukarya assemblages. Sequence data is linked to extensive physical, biological and chemical oceanographic contextual information. Samples are collected monthly to seasonally from multiple depths at seven sites: Darwin Harbour (Northern Territory), Yongala (Queensland), North Stradbroke Island (Queensland), Port Hacking (New South Wales), Maria Island (Tasmania), Kangaroo Island (South Australia), Rottnest Island (Western Australia). These sites span ~30° of latitude and ~38° longitude, range from tropical to cold temperate zones, and are influenced by both local and globally significant oceanographic and climatic features. All sequence datasets are provided in both raw and processed fashion. Currently 952 samples are publically available for bacteria and archaea which include 88,951,761 bacterial (72,435 unique) and 70,463,079 archaeal (24,205 unique) 16 S rRNA v1-3 gene sequences, and 388 samples are available for eukaryotes which include 39,801,050 (78,463 unique) 18 S rRNA v4 gene sequences

Spatial and temporal variability of aerobic anoxygenic photoheterotrophic bacteria along the east coast of Australia

© 2016 Society for Applied Microbiology and John Wiley & Sons Ltd Aerobic Anoxygenic Phototrophic Bacteria (AAnPB) are ecologically important microorganisms, widespread in oceanic photic zones. However, the key environmental drivers underpinning AAnPB abundance and diversity are still largely undefined. The temporal patterns in AAnPB dynamics at three oceanographic reference stations spanning at approximately 15° latitude along the Australian east coast were examined. AAnPB abundance was highly variable, with pufM gene copies ranging from 1.1 × 102 to 1.4 × 105 ml−1 and positively correlated with day length and solar radiation. pufM gene Miseq sequencing revealed that the majority of sequences were closely related to those obtained previously, suggesting that key AAnPB groups are widely distributed across similar environments globally. Temperature was a major structuring factor for AAnPB assemblages across large spatial scales, correlating positively with richness and Gammaproteobacteria (phylogroup K) abundance but negatively with Roseobacter-clade (phylogroup E) abundance, with temperatures between 16°C and 18°C identified as a potential transition zone between these groups. Network analysis revealed that discrete AAnPB populations exploit specific niches defined by varying temperature, light and nutrient conditions in the Tasman Sea system, with evidence for both niche sharing and partitioning amongst closely related operational taxonomic units

High levels of heterogeneity in diazotroph diversity and activity within a putative hotspot for marine nitrogen fixation

Australia’s tropical waters represent predicted ‘hotspots’ for nitrogen (N2) fixation based on empirical and modelled data. However, the identity, activity and ecology of diazotrophs within this region are virtually unknown. By coupling DNA and cDNA sequencing of nitrogenase genes (nifH) with size-fractionated N2 fixation rate measurements, we elucidated diazotroph dynamics across the shelf region of the Arafura and Timor Seas (ATS) and oceanic Coral Sea during Austral spring and winter. During spring, Trichodesmium dominated ATS assemblages, comprising 60% of nifH DNA sequences, while Candidatus Atelocyanobacterium thalassa (UCYN-A) comprised 42% in the Coral Sea. In contrast, during winter the relative abundance of heterotrophic unicellular diazotrophs (δ-proteobacteria and γ-24774A11) increased in both regions, concomitant with a marked decline in UCYN-A sequences, whereby this clade effectively disappeared in the Coral Sea. Conservative estimates of N2 fixation rates ranged from <1 to 91 nmol l−1 day−1, and size fractionation indicated that unicellular organisms dominated N2 fixation during both spring and winter, but average unicellular rates were up to 10-fold higher in winter than in spring. Relative abundances of UCYN-A1 and γ-24774A11 nifH transcripts negatively correlated to silicate and phosphate, suggesting an affinity for oligotrophy. Our results indicate that Australia’s tropical waters are indeed hotspots for N2 fixation and that regional physicochemical characteristics drive differential contributions of cyanobacterial and heterotrophic phylotypes to N2 fixation

Long-term seasonal and interannual variability of marine aerobic anoxygenic photoheterotrophic bacteria

We studied the long-term temporal dynamics of the aerobic anoxygenic phototrophic (AAP) bacteria, a relevant functional group in the coastal marine microbial food web, using high-throughput sequencing of the pufM gene coupled with multivariate, time series and co-occurrence analyses at the Blanes Bay Microbial Observatory (NW Mediterranean). Additionally, using metagenomics, we tested whether the used primers captured accurately the seasonality of the most relevant AAP groups. Phylogroup K (Gammaproteobacteria) was the greatest contributor to community structure over all seasons, with phylogroups E and G (Alphaproteobacteria) being prevalent in spring. Diversity indices showed a clear seasonal trend, with maximum values in winter, which was inverse to that of AAP abundance. Multivariate analyses revealed sample clustering by season, with a relevant proportion of the variance explained by day length, temperature, salinity, phototrophic nanoflagellate abundance, chlorophyll a, and silicate concentration. Time series analysis showed robust rhythmic patterns of co-occurrence, but distinct seasonal behaviors within the same phylogroup, and even within different amplicon sequence variants (ASVs) conforming the same operational taxonomic unit (OTU). Altogether, our results picture the AAP assemblage as highly seasonal and recurrent but containing ecotypes showing distinctive temporal niche partitioning, rather than being a cohesive functional group