Search

The Amazon River has the largest discharge of all rivers on Earth, and its complex plume system fuels a wide array of biogeochemical processes, across a large area of the western tropical North Atlantic. The plume thus stimulates microbial processes affecting carbon sequestration and nutrient cycles at a global scale. Chromosomal gene expression patterns of the 2.0 to 156 mu m size-fraction eukaryotic microbial community were investigated in the Amazon River Plume, generating a robust dataset (more than 100 million mRNA sequences) that depicts the metabolic capabilities and interactions among the eukaryotic microbes. Combining classical oceanographic field measurements with metatranscriptomics yielded characterization of the hydrographic conditions simultaneous with a quantification of transcriptional activity and identity of the community. We highlight the patterns of eukaryotic gene expression for 31 biogeochemically significant gene targets hypothesized to be valuable within forecasting models. An advantage to this targeted approach is that the database of reference sequences used to identify the target genes was selectively constructed and highly curated optimizing taxonomic coverage, throughput, and the accuracy of annotations. A coastal diatom bloom highly expressed nitrate transporters and carbonic anhydrase presumably to support high growth rates and enhance uptake of low levels of dissolved nitrate and CO2. Diatom-diazotroph association (DDA: diatoms with nitrogen fixing symbionts) blooms were common when surface salinity was mesohaline and dissolved nitrate concentrations were below detection, and hence did not show evidence of nitrate utilization, suggesting they relied on ammonium transporters to aquire recently fixed nitrogen. These DDA blooms in the outer plume had rapid turnover of the photosystem D1 protein presumably caused by photodegradation under increased light penetration in clearer waters, and increased expression of silicon transporters as si

Attempts to estimate primary and new production with ADEOS (Advanced Earth Observing Satellite)/OCTS (Ocean Color and Temperature Scanner) data were discussed. Primary production off Sanriku was estimated by OCTS data during the ADEOS/OCTS field campaign. Time series of sinking flux of particle was also measured and compared with the time series of OCTS images during the field campaign. Sea surface nitrate of the North Pacific was estimated by OCTS data and new production during the spring bloom was estimated. Those attempts of ADEOS/OCTS data indicate that the data is useful to estimate primary and new production and significant for the study of carbon and material cycles in the ocean., ADEOS(地球観測プラットフォーム技術衛星)/OCTS(海色海温走査放射計)データを用いて海洋基礎生産と新生産を推定した。三陸沖の基礎生産はADEOS/OCTSの運用期間中にOCTSデータを用いて推定した。時系列沈降粒子フラックスも測定し、同期間中のOCTS時系列画像と比較した。北太平洋の海面硝酸塩をOCTSデータで推定し、春ブルーム期間における新生産を推定した。ADEOS/OCTSデータの解析から、これらのデータは基礎生産と新生産の推定、および海洋における炭素および物質循環の研究に有意義であることが示された。

Our long-term goal is to understand the role of the two most abundant nanoparticles in the sea, viruses and polymer aggregates and their impact on the inherent ocean optical properties of seawater., code 1 only. The original document contains color images.

Our long-term goal is to understand the role of the two most abundant nanoparticles in the sea, viruses and polymer aggregates and their impact on the inherent ocean optical properties of seawater. There are two objectives to this work that deal with the role of nanoparticles and ocean optics: (1) To determine the importance of viruses (and other biological processes) in the formation of chromophoric dissolved organic matter (CDOM) in the ocean through lysis of host cells, and (2) To quantify the importance of aggregate formation to seawater optical properties., code 1 only

Our long-term goal is to understand the role of the two most abundant nanoparticles in the sea, viruses and polymer aggregates and their impact on the inherent ocean optical properties of seawater. This work is important to our understanding of the impact of viral infection on the optical properties of seawater and its suspended microbial communities. In particular, it is critical to know the magnitude of changes in inherent optical properties, the rates of change and host specificity. Our field and laboratory dilution experiments have provided this. Along with changing the size spectrum of the particulate matter, viruses essentially convert Case I waters (where the optical properties can be easily indexed to chlorophyll a) to Case II-like waters (where the optics are dominated by dissolved organic matter, not chlorophyll a). Results of this work have provided important understanding of the time scales of optical changes for the numerically-abundant nano- and picoplankton following infection. The discovery of the virus phi 43 demonstrates that viral infection rates of eukaryotic hosts are even faster than we originally postulated. Our longterm goals are to better understand time-space optical variability associated with viruses, which ultimately provides improved observational capabilities, ocean color algorithms, and predictive-multidisciplinary models. This work also is important for understanding the optical properties associated with polymer-gel formation. Polymer gels begin as nanometer-sized colloids of dissolved organic matter (DOM) that aggregate, producing micron-sized colloids. Polymer gels and viruses represent two of the most abundant particles in the sea; thus, our results have far-reaching implications for ocean optical properties, for both molecular and particle scattering.

Our long-term goal is to understand the role of the two most abundant nanoparticles in the sea, viruses and polymer aggregates, in controlling the inherent ocean optical properties of seawater. There are two objectives to this work that deal with the role of nanoparticles and ocean optics: 1. To determine the importance of viruses (and other biological processes) in the formation of chromophoric dissolved organic matter (CDOM) in the ocean (including the time scales of infection/lysis and CDOM release) 2. To quantify the importance of aggregate formation to seawater optical properties as well as the potential for non-biogenic calcification associated with aggregate formation, Prepared in collaboration with the Dept. of Microbiology, College of Osteopathic Medicine, University of New England, Biddeford, ME. The original document contains color images.