Review Lecture - Picoplankton

1986 ◽  
Vol 228 (1250) ◽  
pp. 1-30 ◽  
Keyword(s):  
Natural Waters ◽  
Heterotrophic Bacteria ◽  
Marine Ecosystem ◽  
Radiant Energy ◽  
Euphotic Zone ◽  
Nutrient Status ◽  
Maximum Growth ◽  
Accessory Pigment ◽  
High Concentrations ◽  
Dynamic Population

Picoplankton consists of those organisms found in the open waters of seas and lakes which are capable of passing through a filter with 2 μm pores but not through one with 0.2 μm pores. Cells in this size range are well adapted to planktonic life in that they sink extremely slowly and are more efficient than larger forms in taking up nutrients and absorbing radiant energy. Picophytoplankton includes coccoid cyanobacteria and a variety of eukaryotic algal forms. Strains studied in the laboratory have all been found to show maximum growth at relatively low irradiances, the eukaryotic forms being more efficient than the cyanobacteria in utilizing the blue light which predominates at the bottom of the photic zone in clear oceanic waters. Oceanic strains of coccoid cyanobacteria, however, are characterized by high concentrations of phycoerythrin, which appears to function as a nitrogenous reserve as well as an accessory pigment in photosynthesis. The seasonal and spatial distribution of picophytoplankton seems explicable in terms of these physiological characteristics. Numbers of coccoid cyanobacteria have shown a striking correlation with temperature in a number of different situations. Heterotrophic bacteria are also included in the picoplankton, and a review of the information concerning them suggests that they form a highly dynamic population subsisting on dissolved organic matter liberated by living phytoplankton and zooplankton and by decomposition of dead matter. The productivity of this population in the euphotic zone approaches that of the phytoplankton. Both the picophytoplankton and the bacterioplankton are preyed on by phagotrophic flagellates. Both bacteria and flagellates are active in regeneration of mineral nutrients. Regardless of the salinity, temperature or nutrient status of the water, the numbers of heterotrophic bacteria, picophytoplankton and flagellates tend to be around 10 6 , 10 4 and 10 3 organisms per millilitre respectively. It is suggested that these populations form a basic, self-sustaining and self-regulating community in all natural waters. From present information, it seems that little of the energy which passes through this community finds its way into the larger planktonic organisms, but the role of picoplankton in recycling nutrient elements is of great importance in the marine ecosystem.

scholarly journals Large subglacial source of mercury from the southwestern margin of the Greenland Ice Sheet

2021 ◽  
Author(s):  
Jon R. Hawkings ◽  
Benjamin S. Linhoff ◽  
Jemma L. Wadham ◽  
Marek Stibal ◽  
Carl H. Lamborg ◽  
...  
Keyword(s):  
Natural Waters ◽  
Inorganic Mercury ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Annual Runoff ◽  
Arctic Ecosystems ◽  
High Mercury ◽  
Southwestern Margin ◽  
High Concentrations ◽  
Dissolved Mercury

AbstractThe Greenland Ice Sheet is currently not accounted for in Arctic mercury budgets, despite large and increasing annual runoff to the ocean and the socio-economic concerns of high mercury levels in Arctic organisms. Here we present concentrations of mercury in meltwaters from three glacial catchments on the southwestern margin of the Greenland Ice Sheet and evaluate the export of mercury to downstream fjords based on samples collected during summer ablation seasons. We show that concentrations of dissolved mercury are among the highest recorded in natural waters and mercury yields from these glacial catchments (521–3,300 mmol km−2 year−1) are two orders of magnitude higher than from Arctic rivers (4–20 mmol km−2 year−1). Fluxes of dissolved mercury from the southwestern region of Greenland are estimated to be globally significant (15.4–212 kmol year−1), accounting for about 10% of the estimated global riverine flux, and include export of bioaccumulating methylmercury (0.31–1.97 kmol year−1). High dissolved mercury concentrations (~20 pM inorganic mercury and ~2 pM methylmercury) were found to persist across salinity gradients of fjords. Mean particulate mercury concentrations were among the highest recorded in the literature (~51,000 pM), and dissolved mercury concentrations in runoff exceed reported surface snow and ice values. These results suggest a geological source of mercury at the ice sheet bed. The high concentrations of mercury and its large export to the downstream fjords have important implications for Arctic ecosystems, highlighting an urgent need to better understand mercury dynamics in ice sheet runoff under global warming.

scholarly journals Diversity of Arctic pelagic <i>Bacteria</i> with an emphasis on photoheterotrophs: a review

2014 ◽  
Vol 11 (12) ◽  
pp. 3309-3322 ◽  
Author(s):  
D. Boeuf ◽  
F. Humily ◽  
C. Jeanthon
Keyword(s):  
Arctic Ocean ◽  
Heterotrophic Bacteria ◽  
Euphotic Zone ◽  
The Arctic ◽  
Major Influence ◽  
Distinctive Features ◽  
Ice Melt ◽  
Energy Needs ◽  
Continental Shelves ◽  
The Arctic Ocean

Abstract. The Arctic Ocean is a unique marine environment with respect to seasonality of light, temperature, perennial ice cover, and strong stratification. Other important distinctive features are the influence of extensive continental shelves and its interactions with Atlantic and Pacific water masses and freshwater from sea ice melt and rivers. These characteristics have major influence on the biological and biogeochemical processes occurring in this complex natural system. Heterotrophic bacteria are crucial components of marine food webs and have key roles in controlling carbon fluxes in the oceans. Although it was previously thought that these organisms relied on the organic carbon in seawater for all of their energy needs, several recent discoveries now suggest that pelagic bacteria can depart from a strictly heterotrophic lifestyle by obtaining energy through unconventional mechanisms that are linked to the penetration of sunlight into surface waters. These photoheterotrophic mechanisms may play a significant role in the energy budget in the euphotic zone of marine environments. Modifications of light and carbon availability triggered by climate change may favor the photoheterotrophic lifestyle. Here we review advances in our knowledge of the diversity of marine photoheterotrophic bacteria and discuss their significance in the Arctic Ocean gained in the framework of the Malina cruise.

scholarly journals Simulating the Impact of the Internal Structure of Phytoplankton on the Bulk Particulate Backscattering Ratio using a Two-Layered Spherical Geometry for Cells

2018 ◽  
Author(s):  
Lucile Duforêt-Gaurier ◽  
David Dessailly ◽  
William Moutier ◽  
Hubert Loisel
Keyword(s):  
Coastal Waters ◽  
Natural Waters ◽  
Heterotrophic Bacteria ◽  
Relative Concentration ◽  
Spherical Geometry ◽  
The Third ◽  
Study Case ◽  
Coated Spheres ◽  
The Impact ◽  
Phytoplankton Cells

The bulk backscattering ratio ($\tilde{b_{bp}}$) is commonly used as a descriptor of the bulk real refractive index of the particulate assemblage in natural waters. Based on numerical simulations, we analyze the impact of heterogeneity of phytoplankton cells on $\tilde{b_{bp}}$. $\tilde{b_{bp}}$ is modeled considering viruses, heterotrophic bacteria, phytoplankton, detritus, and minerals. Three study cases are defined according to the relative abundance of these different components. Two study cases represent typical situations in open ocean, outside (No-B/No-M) and inside bloom (B/No-M). The third study case is typical of coastal waters with the presence of minerals. Phytoplankton cells are modeled by a two-layered spherical geometry representing a chloroplast surrounding the cytoplasm. The $\tilde{b_{bp}}$ values are higher when heterogeneity is considered because the contribution of coated spheres to backscattering is higher than homogeneous spheres. The impact of heterogeneity is however strongly conditioned by the hyperbolic slope $\xi$ of the particle size distribution. Even if the relative concentration of phytoplankton is small (&lt;1%), $\tilde{b_{bp}}$ increases by about 60% (for $\xi=4.3$ and for the No-B/No-M water body), when the heterogeneity is taken into account, in comparison with a particulate population only composed by homogeneous spheres. As expected, heterogeneity has a much smaller impact (about 5$\%$ for $\xi=4.3$) on $\tilde{b_{bp}}$ when minerals are added.

scholarly journals Dissolved iron (II) in the Baltic Sea surface water and implications for cyanobacterial bloom development

2009 ◽  
Vol 6 (2) ◽  
pp. 3803-3850 ◽  
Author(s):  
E. Breitbarth ◽  
J. Gelting ◽  
J. Walve ◽  
L. J. Hoffmann ◽  
D. R. Turner ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Surface Waters ◽  
Cyanobacterial Bloom ◽  
Euphotic Zone ◽  
Strong Wind ◽  
Ferrous Ions ◽  
The Baltic Sea ◽  
High Concentrations ◽  
Wind Events ◽  
The Baltic

Abstract. Iron chemistry measurements were conducted during summer 2007 at two distinct locations in the Baltic Sea (Gotland Deep and Landsort Deep) to evaluate the role of iron for cyanobacterial bloom development in these estuarine waters. Depth profiles of Fe(II) were measured by chemiluminescent flow injection analysis (CL-FIA) and reveal several origins of Fe(II) to the water column. Photoreduction of Fe(III)-complexes and deposition by rain are main sources of Fe(II) (up to 0.9 nmol L−1) in light penetrated surface waters. Indication for organic Fe(II) complexation resulting in prolonged residence times in oxygenated water was observed. Surface dwelling heterocystous cyanobacteria where mainly responsible for Fe(II) consumption in comparison to other phytoplankton. The significant Fe(II) concentrations in surface waters apparently play a major role in cyanobacterial bloom development in the Baltic Sea and are a major contributor to the Fe requirements of diazotrophs. Second, Fe(II) concentrations up to 1.44 nmol L−1 were observed at water depths below the euphotic zone, but above the oxic anoxic interface. Finally, all Fe(III) is reduced to Fe(II) in anoxic deep water. However, only a fraction thereof is present as ferrous ions (up to 28 nmol L−1) and was detected by the CL-FIA method applied. Despite their high concentrations, it is unlikely that ferrous ions originating from sub-oxic waters could be a temporary source of bioavailable iron to the euphotic zone since mixed layer depths after strong wind events are not deep enough in summer time.

scholarly journals Influence of the temperature factor on regeneration features of Silene Jailensis N.I. Rubtzov and Crepis Purpurea (Willd.) M. Bieb. and the content of phenolic substances in vitro

2020 ◽  
pp. 87-96
Author(s):  
I. V. Mitrofanova ◽  
N. N. Ivanova ◽  
A. E. Paliy ◽  
I. N. Paliy ◽  
O. V. Mitrofanova
Keyword(s):  
Phenolic Compounds ◽  
Biochemical Study ◽  
Adventitious Shoots ◽  
Maximum Growth ◽  
Rare Plant ◽  
Temperature Influence ◽  
Phenolic Substances ◽  
Morphogenetic Potential ◽  
High Concentrations

The results of temperature influence on the regeneration of microshoots and the level of phenolic compounds in microshoots of two rare plant species under in vitro conditions are presented. It is shown that the maximum growth of the main and the formation of adventitious shoots, leaves occurred at a temperature of 21- 23°C. Reconnaissance experiments on the biochemical study of organs and tissues of the studied species were conducted. It was found that the leaves contain high concentrations of phenolic substances and are characterized by a wide variety of components. It is shown that as the temperature increased, the content of the sum of phenolic substances increased, which negatively affected the morphogenetic potential of the studied species.

scholarly journals Quorum Sensing Regulates the Hydrolytic Enzyme Production and Community Composition of Heterotrophic Bacteria in Coastal Waters

2021 ◽  
Vol 12 ◽  
Author(s):  
Marion Urvoy ◽  
Raphaël Lami ◽  
Catherine Dreanno ◽  
Daniel Delmas ◽  
Stéphane L’Helguen ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Community Composition ◽  
Coastal Waters ◽  
Bacterial Communities ◽  
Heterotrophic Bacteria ◽  
Bacterial Community Composition ◽  
Marine Ecosystem ◽  
Hydrolytic Enzyme ◽  
Enzymatic Activities ◽  
Hydrolytic Activities

Heterotrophic microbial communities play a central role in biogeochemical cycles in the ocean by degrading organic matter through the synthesis of extracellular hydrolytic enzymes. Their hydrolysis rates result from the community’s genomic potential and the differential expression of this genomic potential. Cell-cell communication pathways such as quorum sensing (QS) could impact both aspects and, consequently, structure marine ecosystem functioning. However, the role of QS communications in complex natural assemblages remains largely unknown. In this study, we investigated whether N-acylhomoserine lactones (AHLs), a type of QS signal, could regulate both hydrolytic activities and the bacterial community composition (BCC) of marine planktonic assemblages. To this extent, we carried out two microcosm experiments, adding five different AHLs to bacterial communities sampled in coastal waters (during early and peak bloom) and monitoring their impact on enzymatic activities and diversity over 48 h. Several specific enzymatic activities were impacted during both experiments, as early as 6 h after the AHL amendments. The BCC was also significantly impacted by the treatments after 48 h, and correlated with the expression of the hydrolytic activities, suggesting that changes in hydrolytic intensities may drive changes in BCC. Overall, our results suggest that QS communication could participate in structuring both the function and diversity of marine bacterial communities.

Quantum yield of the marine benthic microflora of near-shore coastal Penang, Malaysia

2005 ◽  
Vol 56 (7) ◽  
pp. 1047 ◽  
Author(s):  
A. McMinn ◽  
S. Sellah ◽  
W. A. Wan Ab. Llah ◽  
M. Mohammad ◽  
F. Md. Sidik Merican ◽  
...  
Keyword(s):  
Primary Production ◽  
Suspended Solids ◽  
Euphotic Zone ◽  
Water Clarity ◽  
Quantum Yields ◽  
Chl A ◽  
Near Shore ◽  
High Concentrations ◽  
A Minor ◽  
Reduced Water

Benthic microalgal communities often contribute more than 30% of the primary production of shallow coastal and estuarine areas. At Muka Head Penang (Pulau Pinang) and the Songsong Islands (Pulau Songsong), Kedah, Malaysia, high concentrations of suspended solids and phytoplankton biomass (10.6 mg Chl a m−3) has reduced water clarity such that the euphotic zone of these areas is less than 2 m and 3 m deep respectively. The benthic microalgal communities, which were composed of the diatom genera Cocconeis, Fragilaria, Paralia and Pleurosigma, had a low biomass, had low maximum quantum yields (0.325 ± 0.129), were poorly adapted to their light environment and were constantly light limited. These characteristics suggest that the benthic microalgal communities were likely to have made only a minor contribution to the total primary production of the area.

scholarly journals Measurements of nitrite production in and around the primary nitrite maximum in the central California Current

2013 ◽  
Vol 10 (11) ◽  
pp. 7395-7410 ◽  
Author(s):  
A. E. Santoro ◽  
C. M. Sakamoto ◽  
J. M. Smith ◽  
J. N. Plant ◽  
A. L. Gehman ◽  
...  
Keyword(s):  
Ammonia Oxidation ◽  
Heterotrophic Bacteria ◽  
California Current ◽  
Euphotic Zone ◽  
Ammonia Oxidizing Bacteria ◽  
Central California ◽  
Oxidation Rates ◽  
Ammonia Oxidizing Archaea ◽  
Nitrite Production ◽  
Nh3 Oxidation

Abstract. Nitrite (NO2−) is a substrate for both oxidative and reductive microbial metabolism. NO2− accumulates at the base of the euphotic zone in oxygenated, stratified open-ocean water columns, forming a feature known as the primary nitrite maximum (PNM). Potential pathways of NO2− production include the oxidation of ammonia (NH3) by ammonia-oxidizing bacteria and archaea as well as assimilatory nitrate (NO3−) reduction by phytoplankton and heterotrophic bacteria. Measurements of NH3 oxidation and NO3− reduction to NO2− were conducted at two stations in the central California Current in the eastern North Pacific to determine the relative contributions of these processes to NO2− production in the PNM. Sensitive (< 10 nmol L−1), precise measurements of [NH4+] and [NO2−] indicated a persistent NH4+ maximum overlying the PNM at every station, with concentrations as high as 1.5 μmol L−1. Within and just below the PNM, NH3 oxidation was the dominant NO2− producing process, with rates of NH3 oxidation to NO2− of up to 31 nmol L−1 d−1, coinciding with high abundances of ammonia-oxidizing archaea. Though little NO2− production from NO3− was detected, potentially nitrate-reducing phytoplankton (photosynthetic picoeukaryotes, Synechococcus, and Prochlorococcus) were present at the depth of the PNM. Rates of NO2− production from NO3− were highest within the upper mixed layer (4.6 nmol L−1 d−1) but were either below detection limits or 10 times lower than NH3 oxidation rates around the PNM. One-dimensional modeling of water column NO2− production agreed with production determined from 15N bottle incubations within the PNM, but a modeled net biological sink for NO2− just below the PNM was not captured in the incubations. Residence time estimates of NO2− within the PNM ranged from 18 to 470 days at the mesotrophic station and was 40 days at the oligotrophic station. Our results suggest the PNM is a dynamic, rather than relict, feature with a source term dominated by ammonia oxidation.

Anaerobic Treatment of Industrial Wastewater Containing Organic Solvents

1994 ◽  
Vol 29 (9) ◽  
pp. 321-329 ◽  
Author(s):  
Evangelos Terzis
Keyword(s):  
Anaerobic Digestion ◽  
Organic Solvents ◽  
Industrial Effluent ◽  
Maximum Growth ◽  
Anaerobic Treatment ◽  
Maximum Growth Rate ◽  
Bacterial Cells ◽  
Precise Control ◽  
Water Charges ◽  
High Concentrations

Industrial water usage results in large volumes of liquid wastes rich in organic pollutants. Waste waters from certain industrial chemical operations (e.g. organic synthesis, perfume industry) will sometimes contain organic solvents at relatively high concentrations. The presence of organic solvents is undesirable in the sewerage system and so must be removed from the industrial effluent. Anaerobic treatment of many of these organic solvents is possible, in which the organic material is converted ~90% to volatile substances -carbon dioxide and methane gas- and ~10% to new bacterial cells (solids). Industry will be using less water in the future. Increased water charges will lead to more precise control and integrated processes will reduce wastage. The smaller volumes of more concentrated waste will be ideal for anaerobic digestion. In order to evaluate the optimum conditions for the anaerobic digestion of propan-2-ol (iso-propanol) the kinetic parameters of the Monod rate model, namely, maximum growth rate (µm), yield (Y), half velocity constant (Ks) and endogenous decay coefficient (Kd), were determined at the temperature range 25°-40°C, inclusively. The regulatory role of molecular hydrogen was investigated and discussed, and also its possible use as a monitor feature in the anaerobic digestion.

The limits of sodium/calcium interactions in plant growth

2000 ◽  
Vol 27 (7) ◽  
pp. 709 ◽  
Author(s):  
Robert J. Reid ◽  
F. Andrew Smith
Keyword(s):  
High Salinity ◽  
Foliar Application ◽  
Maximum Growth ◽  
Growth Responses ◽  
Wheat Seedlings ◽  
Low Salinity ◽  
High Concentrations ◽  
Main Component ◽  
Dependent Processes ◽  
Root Plasma Membrane

The amelioration of Na toxicity by supplementation of Ca in the growth medium was investigated in wheat with the aims of (1) identifying the Ca-dependent processes that determine the growth responses and (2) defining the limits to Ca effects on these processes. Growth of wheat seedlings was strongly inhibited by 150 mM NaCl but improved as the Ca concentration in the nutrient medium was increased up to 2.34 mM. Further increasing Ca to 10 mM did not increase growth, nor did foliar application of Ca. Even at high concentrations of Ca, the maximum growth was only approximately 50% of the growth at low salinity. We conclude that the main component of improved growth caused by Ca was via its apoplastic effects on the transport of Na and K across the root plasma membrane, rather than by increasing root or shoot Ca concentrations. There was no evidence that high salinity inhibited Ca uptake to the shoot. The limits to improvement of growth by Ca appear to relate to the fact that, although Ca is able to ameliorate the toxicity caused by high intracellular Na, it is not able to overcome the osmotic deficits associated with high salinity.

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