Photosynthetic characteristics of marine Synechococcus spp. with special reference to light environments near the bottom of the euphotic zone of the open ocean

1994 ◽  
Vol 118 (2) ◽  
pp. 215-221 ◽  
Author(s):  
T. Ikeya ◽  
K. Ohki ◽  
M. Takahashi ◽  
Y. Fujita
Keyword(s):  
Special Reference ◽  
Euphotic Zone ◽  
Open Ocean ◽  
Photosynthetic Characteristics

scholarly journals Modeling submerged biofouled microplastics and their vertical trajectories

2021 ◽  
Author(s):  
Reint Fischer ◽  
Delphine Lobelle ◽  
Merel Kooi ◽  
Albert Koelmans ◽  
Victor Onink ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Mixed Layer ◽  
Mixed Layer Depth ◽  
Euphotic Zone ◽  
Equatorial Pacific ◽  
Open Ocean ◽  
Subtropical Gyre ◽  
Layer Depth ◽  
High Biological Activity ◽  
Near Surface

Abstract. The fate of (micro)plastic particles in the open ocean is controlled by physical and biological processes. Here, we model the effects of biofouling on the subsurface vertical distribution of spherical, virtual plastic particles with radii of 0.01–1 mm. For the physics, four vertical velocity terms are included: advection, wind-driven mixing, tidally induced mixing, and the sinking velocity of the biofouled particle. For the biology, we simulate the attachment, growth and loss of algae on particles. We track 10,000 particles for one year in three different regions with distinct biological and physical properties: the low productivity region of the North Pacific Subtropical Gyre, the high productivity region of the Equatorial Pacific and the high mixing region of the Southern Ocean. The growth of biofilm mass in the euphotic zone and loss of mass below the euphotic zone result in the oscillatory behaviour of particles, where the larger (0.1–1.0 mm) particles have much shorter average oscillation lengths (< 10 days; 90th percentile) than the smaller (0.01–0.1 mm) particles (up to 130 days; 90th percentile). A subsurface maximum concentration occurs just below the mixed layer depth (around 30 m) in the Equatorial Pacific, which is most pronounced for larger particles (0.1–1.0 mm). This occurs since particles become neutrally buoyant when the processes affecting the settling velocity of the particle and the motion of the ocean are in equilibrium. Seasonal effects in the subtropical gyre result in particles sinking below the mixed layer depth only during spring blooms, but otherwise remaining within the mixed layer. The strong winds and deepest average mixed layer depth in the Southern Ocean (400 m) result in the deepest redistribution of particles (> 5000 m). Our results show that the vertical movement of particles is mainly affected by physical (wind-induced mixing) processes within the mixed layer and biological (biofilm) dynamics below the mixed layer. Furthermore, positively buoyant particles with radii of 0.01–1.0 mm can sink far below the euphotic zone and mixed layer in regions with high near-surface mixing or high biological activity. This work can easily be coupled to other models to simulate open-ocean biofouling dynamics, in order to reach a better understanding of where ocean (micro)plastic ends up.

scholarly journals Insights into global diatom distribution and diversity in the world’s ocean

2016 ◽  
Vol 113 (11) ◽  
pp. E1516-E1525 ◽  
Author(s):  
Shruti Malviya ◽  
Eleonora Scalco ◽  
Stéphane Audic ◽  
Flora Vincent ◽  
Alaguraj Veluchamy ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Drake Passage ◽  
Euphotic Zone ◽  
Sampling Procedure ◽  
Open Ocean ◽  
Global Ocean ◽  
Planktonic Diatoms ◽  
Operational Taxonomic Units ◽  
Wide Range ◽  
Indian And Atlantic Oceans

Diatoms (Bacillariophyta) constitute one of the most diverse and ecologically important groups of phytoplankton. They are considered to be particularly important in nutrient-rich coastal ecosystems and at high latitudes, but considerably less so in the oligotrophic open ocean. The Tara Oceans circumnavigation collected samples from a wide range of oceanic regions using a standardized sampling procedure. Here, a total of ∼12 million diatom V9-18S ribosomal DNA (rDNA) ribotypes, derived from 293 size-fractionated plankton communities collected at 46 sampling sites across the global ocean euphotic zone, have been analyzed to explore diatom global diversity and community composition. We provide a new estimate of diversity of marine planktonic diatoms at 4,748 operational taxonomic units (OTUs). Based on the total assigned ribotypes, Chaetoceros was the most abundant and diverse genus, followed by Fragilariopsis, Thalassiosira, and Corethron. We found only a few cosmopolitan ribotypes displaying an even distribution across stations and high abundance, many of which could not be assigned with confidence to any known genus. Three distinct communities from South Pacific, Mediterranean, and Southern Ocean waters were identified that share a substantial percentage of ribotypes within them. Sudden drops in diversity were observed at Cape Agulhas, which separates the Indian and Atlantic Oceans, and across the Drake Passage between the Atlantic and Southern Oceans, indicating the importance of these ocean circulation choke points in constraining diatom distribution and diversity. We also observed high diatom diversity in the open ocean, suggesting that diatoms may be more relevant in these oceanic systems than generally considered.

scholarly journals Genetic Diversity and Cooccurrence Patterns of Marine Cyanopodoviruses and Picocyanobacteria

2018 ◽  
Vol 84 (16) ◽  
Author(s):  
Yingting Sun ◽  
Si Zhang ◽  
Lijuan Long ◽  
Junde Dong ◽  
Feng Chen ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Coastal Area ◽  
Time Course ◽  
Equatorial Indian Ocean ◽  
Euphotic Zone ◽  
Open Ocean ◽  
Host Community ◽  
23S Rrna ◽  
Content Type ◽  
Sanya Bay

ABSTRACTPicocyanobacteriaProchlorococcusandSynechococcusare abundant in the global oceans and subject to active viral infection. In this study, the genetic diversity of picocyanobacteria and the genetic diversity of cyanopodoviruses were synchronously investigated along water columns in the equatorial Indian Ocean and over a seasonal time course in the coastal Sanya Bay, South China Sea. Using the 16S-23S rRNA internal transcribed spacer (ITS)-based clone library and quantitative PCR (qPCR) analyses, the picocyanobacterial community composition and abundance were determined. Sanya Bay was dominated by clade IISynechococcusduring all the seasons, and a typical population shift from high-light-adaptedProchlorococcusto low-light-adaptedProchlorococcuswas found along the vertical profiles. Strikingly, the DNA polymerase gene sequences of cyanopodoviruses revealed a much greater genetic diversity than we expected. Nearly one-third of the phylogenetic groups were newly described here. No apparent seasonal pattern was observed for the Sanya Bay picocyanobacterial or cyanopodoviral communities. Different dominant cyanopodovirus lineages were identified for the coastal area, upper euphotic zone, and middle-to-lower euphotic zone of the open ocean. Diversity indices of both picocyanobacteria and cyanopodoviruses were highest in the middle euphotic zone and both were lower in the upper euphotic zone, reflecting a host-virus interaction. Cyanopodoviral communities differed significantly between the upper euphotic zone and the middle-to-lower euphotic zone, showing a vertical pattern similar to that of picocyanobacteria. However, in the surface waters of the open ocean, cyanopodoviruses exhibited no apparent biogeographic pattern, differing from picocyanobacteria. This study demonstrates correlated distribution patterns of picocyanobacteria and cyanopodoviruses, as well as the complex biogeography of cyanopodoviruses.IMPORTANCEPicocyanobacteria are highly diverse and abundant in the ocean and display remarkable global biogeography and a vertical distribution pattern. However, how the diversity and distribution of picocyanobacteria affect those of the viruses that infect them remains largely unknown. Here we synchronously analyzed the community structures of cyanopodoviruses and picocyanobacteria at spatial and temporal scales. Both spatial and temporal variations of cyanopodoviral communities can be linked to those of picocyanobacteria. The coastal area, upper euphotic zone, and middle-to-lower euphotic zone of the open ocean have distinct cyanopodoviral communities, showing horizontal and vertical variation patterns closely related to those of picocyanobacteria. These findings emphasize the driving force of host community in shaping the biogeographic structure of viruses. Our work provides important information for future assessments of the ecological roles of viruses and hosts for each other.

scholarly journals A Study of the Distributions of Two Endangered Sea Skaters Halobates matsumurai Esaki and Asclepios shiranui (Esaki) (Hemiptera: Gerridae: Halobatinae) with Special Reference to Their Strategies to Cope with Tidal Currents

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Terumi Ikawa ◽  
Yuichi Nozoe ◽  
Natsuko Yamashita ◽  
Namiko Nishimura ◽  
Satoshi Ohnoki ◽  
...  
Keyword(s):  
Special Reference ◽  
Intertidal Zone ◽  
Tidal Currents ◽  
Open Ocean ◽  
Survival Strategies ◽  
Close Relative ◽  
Coastal Species ◽  
Coastal Sea ◽  
Oceanic Species

There exist surprisingly few marine insects, most of which are confined to the intertidal zone. Halobates is the only genus to have some oceanic species along with some coastal species. Among the coastal sea skaters, that is, genus Halobates and its close relative, genus Asclepios, there are variations in their affinity for the shore. We have studied the distributions of two endangered Japanese sea skaters, Halobates matsumurai and Asclepios shiranui in Kujukushima, where they cooccur in coves. To compare their survival strategies at sea, we especially noted differences in their distributions along the shore during high and low tides. The results show that A. shiranui tended to remain along the shore during low tide. This species appeared to cling to the shore against the ebb current and to stay in the protected coves. By contrast, H. matsumurai tended to leave the shore during low tide. Notably, some adults were found skating outside the coves. The strategy of H. matsumurai appeared to be leaving with the ebb current even beyond the coves, thereby using more resources and enlarging its habitat. Some such coastal Halobates might have acquired the ability to live on the open ocean clearly independent of the shoreline.

scholarly journals Lateral advection supports nitrogen export in the oligotrophic open-ocean Gulf of Mexico

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Thomas B. Kelly ◽  
Angela N. Knapp ◽  
Michael R. Landry ◽  
Karen E. Selph ◽  
Taylor A. Shropshire ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Surface Waters ◽  
Organic Nitrogen ◽  
Regional Scale ◽  
Euphotic Zone ◽  
Open Ocean ◽  
Biogeochemical Model ◽  
Nitrogen Export ◽  
Field Campaigns ◽  
Lateral Advection

AbstractIn contrast to its productive coastal margins, the open-ocean Gulf of Mexico (GoM) is notable for highly stratified surface waters with extremely low nutrient and chlorophyll concentrations. Field campaigns in 2017 and 2018 identified low rates of turbulent mixing, which combined with oligotrophic nutrient conditions, give very low estimates for diffusive flux of nitrate into the euphotic zone (< 1 µmol N m−2 d−1). Estimates of local N2-fixation are similarly low. In comparison, measured export rates of sinking particulate organic nitrogen (PON) from the euphotic zone are 2 – 3 orders of magnitude higher (i.e. 462 – 1144 µmol N m−2 d−1). We reconcile these disparate findings with regional scale dynamics inferred independently from remote-sensing products and a regional biogeochemical model and find that laterally-sourced organic matter is sufficient to support >90% of open-ocean nitrogen export in the GoM. Results show that lateral transport needs to be closely considered in studies of biogeochemical balances, particularly for basins enclosed by productive coasts.

scholarly journals An Open Ocean Trial of Controlled Upwelling Using Wave Pump Technology

2010 ◽  
Vol 27 (2) ◽  
pp. 385-396 ◽  
Author(s):  
Angelicque White ◽  
Karin Björkman ◽  
Eric Grabowski ◽  
Ricardo Letelier ◽  
Steve Poulos ◽  
...  
Keyword(s):  
Deep Water ◽  
Cold Water ◽  
Phytoplankton Bloom ◽  
Vertical Motion ◽  
Euphotic Zone ◽  
Open Ocean ◽  
Molar Ratio ◽  
Upward Movement ◽  
Surface Ocean ◽  
Total Input

Abstract In 1976, John D. Isaacs proposed to use wave energy to invert the density structure of the ocean and pump deep, nutrient-rich water into the sunlit surface layers. The basic principle is simple: a length of tubing attached to a surface buoy at the top, and a one-way valve at the bottom can be extended below the euphotic zone to act as a conduit for deep water. The vertical motion of the ocean forces the attached valve to open on the downslope of a wave and close on the upslope, thus generating upward movement of deep water to the surface ocean. Although Isaacs’s wave-powered pump has taken many forms, from energy production to aquaculture to the more recent suggestion that artificial upwelling could be used to stimulate primary productivity and carbon sequestration, the simple engineering concept remains the same. In June 2008, the authors tested a commercially available wave pump (Atmocean) north of Oahu, Hawaii, to assess the logistics of at-sea deployment and the durability of the equipment under open ocean conditions. This test was done as part of an experiment designed to evaluate a recently published hypothesis that upwelling of water containing excess phosphate (P) relative to nitrogen (N) compared to the canonical “Redfield” molar ratio of 16N:1P would generate a two-phased phytoplankton bloom. The end result of this field experiment was rapid delivery (&lt;2 h for a 300-m transit) of deep water to the surface ocean followed by catastrophic failure of pump materials under the dynamic stresses of the oceanic environment. Wave-driven upwelling of cold water was documented for a period of ∼17 h, with a volumetric upwelling rate of ∼45 m3 h−1 and an estimated total input of 765 m3 of nutrient-enriched deep water. The authors discuss the deployment of a 300-m wave pump, the strategy to sample a biogeochemical response, the engineering challenges faced, and the implications of these results for future experiments aimed at stimulating the growth of phytoplankton.

scholarly journals Lateral Advection Supports Nitrogen Export in the Oligotrophic Open-Ocean Gulf of Mexico

2020 ◽  
Author(s):  
Thomas Kelly ◽  
Angela Knapp ◽  
Michael Landry ◽  
Karen Selph ◽  
Taylor Shropshire ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Surface Waters ◽  
Organic Nitrogen ◽  
Regional Scale ◽  
Euphotic Zone ◽  
Open Ocean ◽  
Biogeochemical Model ◽  
Nitrogen Export ◽  
Field Campaigns ◽  
Lateral Advection

Abstract In contrast to its productive coastal margins, the open-ocean Gulf of Mexico (GoM) is notable for highly stratified surface waters with extremely low nutrient and chlorophyll concentrations. Field campaigns in 2017 and 2018 indicate low rates of turbulent mixing, which combined with oligotrophic nutrient conditions, give very low estimates of diffusive flux of nitrate into the euphotic zone (< 1 µmol N m-2 d-1). Estimates of local N2-fixation are similarly low. In comparison, measured export rates of sinking particulate organic nitrogen (PON) from the euphotic zone are 2-3 orders of magnitude higher (i.e. 462 – 1144 µmol N m-2 d-1). We reconcile these disparate findings with regional scale dynamics inferred independently from remote-sensing products and a regional biogeochemical model and find that laterally-sourced organic matter is sufficient to support >90% of open-ocean nitrogen export in the GoM. Results show that lateral transport needs to be closely considered in studies of biogeochemical balances, particularly for basins enclosed by productive coasts.

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