scholarly journals From the shape of the vertical profile of in vivo fluorescence to Chlorophyll-<i>a</i> concentration

2011 ◽  
Vol 8 (8) ◽  
pp. 2391-2406 ◽  
Author(s):  
A. Mignot ◽  
H. Claustre ◽  
F. D'Ortenzio ◽  
X. Xing ◽  
A. Poteau ◽  
...  
Keyword(s):  
Mixed Layer ◽  
Mixed Layer Depth ◽  
Homogeneous Layer ◽  
Fluorescence Signal ◽  
Vertical Profiles ◽  
Shape Parameters ◽  
Chl A ◽  
In Vivo Fluorescence ◽  
Chl A Fluorescence

Abstract. In vivo fluorescence of Chlorophyll-a (Chl-a) is a potentially useful property to study the vertical distribution of phytoplankton biomass. However the technique is presently not fully exploited as it should be, essentially because of the difficulties in converting the fluorescence signal into an accurate Chl-a concentration. These difficulties arise noticeably from natural variations in the Chl-a fluorescence relationship, which is under the control of community composition as well as of their nutrient and light status. As a consequence, although vertical profiles of fluorescence are likely the most recorded biological property in the open ocean, the corresponding large databases are underexploited. Here with the aim to convert a fluorescence profile into a Chl-a concentration profile, we test the hypothesis that the Chl-a concentration can be gathered from the sole knowledge of the shape of the fluorescence profile. We analyze a large dataset from 18 oceanographic cruises conducted in case-1 waters from the highly stratified hyperoligotrophic waters (surface Chl-a = 0.02 mg m−3) of the South Pacific Gyre to the eutrophic waters of the Benguela upwelling (surface Chl-a = 32 mg m−3) and including the very deep mixed waters in the North Atlantic (Mixed Layer Depth = 690 m). This dataset encompasses more than 700 vertical profiles of Chl-a fluorescence as well as accurate estimations of Chl-a by High Performance Liquid Chromatography (HPLC). Two typical fluorescence profiles are identified, the uniform profile, characterized by a homogeneous layer roughly corresponding to the mixed layer, and the non-uniform profile, characterized by the presence of a Deep Chlorophyll Maximum. Using appropriate mathematical parameterizations, a fluorescence profile is subsequently represented by 3 or 5 shape parameters for uniform or non-uniform profiles, respectively. For both situations, an empirical model is developed to predict the "true" Chl-a concentration from these shape parameters. This model is then used to calibrate a fluorescence profile in Chl-a units. The validation of the approach provides satisfactory results with a median absolute percent deviation of 33 % when comparing the HPLC Chl-a profiles to the Chl-a-calibrated fluorescence. The proposed approach thus opens the possibility to produce Chl-a climatologies from uncalibrated fluorescence profile databases that have been acquired in the past and to which numerous new profiles will be added, thanks to the recent availability of autonomous platforms (profiling floats, gliders and animals) instrumented with miniature fluorometers.

scholarly journals From the shape of the vertical profile of in vivo fluorescence to Chlorophyll-<i>a</i> concentration

2011 ◽  
Vol 8 (2) ◽  
pp. 3697-3737 ◽  
Author(s):  
A. Mignot ◽  
H. Claustre ◽  
F. D'Ortenzio ◽  
X. Xing ◽  
A. Poteau ◽  
...  
Keyword(s):  
Mixed Layer ◽  
Mixed Layer Depth ◽  
Homogeneous Layer ◽  
Fluorescence Signal ◽  
Vertical Profiles ◽  
Shape Parameters ◽  
Chl A ◽  
In Vivo Fluorescence ◽  
Chl A Fluorescence

Abstract. In vivo fluorescence of Chlorophyll-a (Chl-a) is a potentially useful property to study the vertical distribution of phytoplankton biomass. However the technique is presently not fully exploited as it should be, essentially because of the difficulties in converting the fluorescence signal into an accurate Chl-a concentration. These difficulties arise noticeably from natural variations in the Chl-a fluorescence relationship, which is under the control of community composition as well as of their nutrient and light status. As a consequence although vertical profiles of fluorescence are likely the most recorded biological property in the open ocean, the corresponding large databases are underexploited. Here with the aim to convert a fluorescence profile into a Chl-a concentration profile, we test the hypothesis that the Chl-a concentration can be gathered from the sole knowledge of the shape of the fluorescence profile. We analyze a large dataset from 18 oceanographic cruises conducted in case-1 waters from the highly stratified hyperoligotrophic waters (surface Chl-a = 0.02 mg m−3) of the South Pacific Gyre to the eutrophic waters of the Benguela upwelling (surface Chl-a = 32 mg m−3) and including the very deep mixed waters in the North Atlantic (Mixed Layer Depth = 690 m). This dataset encompasses more than 700 vertical profiles of Chl-a fluorescence as well as accurate estimations of Chl-a by High Performance Liquid Chromatography (HPLC). Two typical fluorescence profiles are identified, the uniform profile, characterized by a homogeneous layer roughly corresponding to the mixed layer, and the non-uniform profile, characterized by the presence of a Deep Chlorophyll Maximum. Using appropriate mathematical parameterizations, a fluorescence profile is subsequently represented by 3 or 5 shape parameters for uniform or non-uniform profiles, respectively. For both situations, an empirical model is developed to predict the "true" Chl-a concentration from these shape parameters. This model is then used to calibrate a fluorescence profile in Chl-a units. The validation of the approach provides satisfactory results with a median absolute percent deviation of 33% when comparing the HPLC Chl-a profiles to the Chl-a-calibrated fluorescence. The proposed approach thus opens the possibility to produce Chl-a climatologies from uncalibrated fluorescence profile databases that have been acquired in the past and to which numerous new profiles will be added, thanks to the recent availability of autonomous platforms (profiling floats, gliders and animals) instrumented with miniature fluorometers.

The Deep Chlorophyll Maximum: Comparing Vertical Profiles of Chlorophyll a

1982 ◽  
Vol 39 (5) ◽  
pp. 791-803 ◽  
Author(s):  
John J. Cullen
Keyword(s):  
Chlorophyll A ◽  
Phytoplankton Biomass ◽  
Physiological Adaptation ◽  
Organic Carbon Content ◽  
Deep Chlorophyll Maximum ◽  
Vertical Profiles ◽  
In Vivo Fluorescence ◽  
Chlorophyll Maximum ◽  
Vertical Distributions

The relationship between chlorophyll a and phytoplankton biomass (organic carbon content) is highly variable as is the yield of in vivo fluorescence per unit chlorophyll. Thus, vertical profiles of chlorophyll or in vivo fluorescence must be interpreted with caution if their ecological significance is to be established. Although the variability of carbon-to-chlorophyll ratios and fluorescence yield is large, much of it can be anticipated, corrected for, and usefully interpreted. Vertical profiles from different regions of the sea are presented; each has a deep chlorophyll maximum, but the probable mechanisms of their formation and maintenance differ widely. Most vertical distributions of chlorophyll can be explained by the interaction between hydrography and growth, behavior, or physiological adaptation of phytoplankton with no special consideration of grazing by herbivores, even though vertical distributions of epizooplankton are not uniform. The interaction between vertical profiles of zooplankton and chlorophyll will be better understood when the relationships between chlorophyll and phytoplankton biomass in those profiles is determined.Key words: chlorophyll a, fluorescence, phytoplankton, vertical structure

scholarly journals Global distribution and variability of subsurface chlorophyll a concentration

2021 ◽  
Author(s):  
Sayaka Yasunaka ◽  
Tsuneo Ono ◽  
Kosei Sasaoka ◽  
Kanako Sato
Keyword(s):  
Chlorophyll A ◽  
Mixed Layer ◽  
Net Primary Production ◽  
Thermal Structure ◽  
Mixed Layer Depth ◽  
Subsurface Layer ◽  
Spatiotemporal Variability ◽  
Shortwave Radiation ◽  
Concentration Data ◽  
Chl A

Abstract. Chlorophyll a (Chl-a) often retains its maximum concentration not at the surface but in the subsurface layer. The depth of the Chl-a maximum primarily depends on the balance between light penetration from the surface and nutrient supply from the deep ocean. However, a global map of subsurface Chl-a concentrations based on observations has not been presented yet. In this study, we integrate Chl-a concentration data not only from recent biogeochemical floats but also from historical ship-based and other observations, and present global maps of subsurface Chl-a concentration with related variables. The subsurface Chl-a maximum deeper than the mixed layer depth was stably observed in the subtropics and tropics (30° S to 30° N), only in summer in midlatitudes (30–40° N/S), and rarely at 45–60° S of the Southern Ocean and in the northern North Atlantic (north of 45° N). The depths of the subsurface Chl-a maxima are deeper than those of the euphotic layer in the subtropics and shallower in the tropics and midlatitudes. In the subtropics, seasonal oxygen increases below the mixed layer implied substantial biological new production, which corresponds to 10 % of the net primary production there. During El Niño, the subsurface Chl-a concentration in the equatorial Pacific is higher in the middle to the east and lower in the west than that during La Niña, which is opposite that on the surface. The spatiotemporal variability of the Chl-a concentration described here would be suggestive results not only for the biogeochemical cycle in the ocean but also for the thermal structure and the dynamics of the ocean via the absorption of shortwave radiation.

scholarly journals MMP-14-targeted Nanoprobe for in vivo Fluorescence Imaging of Rupture-prone Carotid Plaques

2021 ◽  
Author(s):  
Mengtao Han ◽  
Kaining Liu ◽  
Hongqiu Xiao ◽  
Tao Sun ◽  
Fei Wang ◽  
...  
Keyword(s):  
Fluorescence Imaging ◽  
Fluorescence Signal ◽  
Plaque Progression ◽  
Carotid Plaques ◽  
In Vivo Fluorescence ◽  
Cell Tissue ◽  
A Cell ◽  
In Vivo Fluorescence Imaging ◽  
Membrane Anchoring

Abstract Background: The identification of rupture-prone carotid plaques for preventing stroke remains a clinical challenge. Macrophage matrix metalloproteinase (MMP)-14, which contributes to plaque progression and destabilisation, could be a promising biomarker for plaque imaging. This study aimed to design and synthesise an MMP-14-targeted nanoprobe to noninvasively visualise the behaviour of M1 macrophages in atherosclerotic plaques.Methods: A fluorescence molecular imaging probe ([email protected]) was constructed by covalently attaching the fluorescent dye cyanine (Cy) 5.5, an MMP-14 substrate, and polyethylene glycol (PEG) 5000-wrapped gold nanoparticles (AuNPs), and then administered via tail vein injection to carotid atherosclerosis models for in vivo fluorescence imaging. Additionally, carotid tissues and cultured macrophages were analysed for nanoprobe binding, and MMP-14 and inflammation-related marker expression was evaluated by polymerase chain reaction, western blotting, and immunohistochemistry.Results: MMP-14 expression significantly increased with plaque progression, along with the upregulation of MMP-2 and inflammatory M1 markers, CD68 and F4/80, and significant downregulation of the M2 marker CD206. All of cell, tissue and in vivo fluorescence imaging exhibited a favourable targeting efficacy of [email protected] for MMP-14.Conclusions: MMP-14, a cell membrane-anchoring enzyme, can serve as a biomarker of vulnerable plaques, and MMP-14 substrate-based [email protected], with an intense fluorescence signal after activation and good biocompatibility, can be applied to screen for and monitor plaque progression in vivo.

scholarly journals Delineation of marine ecosystem zones in the northern Arabian Sea during winter

2018 ◽  
Vol 15 (5) ◽  
pp. 1395-1414 ◽  
Author(s):  
Saleem Shalin ◽  
Annette Samuelsen ◽  
Anton Korosov ◽  
Nandini Menon ◽  
Björn C. Backeberg ◽  
...  
Keyword(s):  
Mixed Layer ◽  
Temporal Variability ◽  
Arabian Sea ◽  
Mixed Layer Depth ◽  
Marine Ecosystem ◽  
Chlorophyll Concentration ◽  
Spatial And Temporal Variability ◽  
Chl A ◽  
Northern Arabian Sea ◽  
Cross Correlation Analysis

Abstract. The spatial and temporal variability of marine autotrophic abundance, expressed as chlorophyll concentration, is monitored from space and used to delineate the surface signature of marine ecosystem zones with distinct optical characteristics. An objective zoning method is presented and applied to satellite-derived Chlorophyll a (Chl a) data from the northern Arabian Sea (50–75∘ E and 15–30∘ N) during the winter months (November–March). Principal component analysis (PCA) and cluster analysis (CA) were used to statistically delineate the Chl a into zones with similar surface distribution patterns and temporal variability. The PCA identifies principal components of variability and the CA splits these into zones based on similar characteristics. Based on the temporal variability of the Chl a pattern within the study area, the statistical clustering revealed six distinct ecological zones. The obtained zones are related to the Longhurst provinces to evaluate how these compared to established ecological provinces. The Chl a variability within each zone was then compared with the variability of oceanic and atmospheric properties viz. mixed-layer depth (MLD), wind speed, sea-surface temperature (SST), photosynthetically active radiation (PAR), nitrate and dust optical thickness (DOT) as an indication of atmospheric input of iron to the ocean. The analysis showed that in all zones, peak values of Chl a coincided with low SST and deep MLD. The rate of decrease in SST and the deepening of MLD are observed to trigger the algae bloom events in the first four zones. Lagged cross-correlation analysis shows that peak Chl a follows peak MLD and SST minima. The MLD time lag is shorter than the SST lag by 8 days, indicating that the cool surface conditions might have enhanced mixing, leading to increased primary production in the study area. An analysis of monthly climatological nitrate values showed increased concentrations associated with the deepening of the mixed layer. The input of iron seems to be important in both the open-ocean and coastal areas of the northern and north-western parts of the northern Arabian Sea, where the seasonal variability of the Chl a pattern closely follows the variability of iron deposition.

Frost Resistance of Wheat and CHL a in vivo Fluorescence Induction Kinetics

1990 ◽  
pp. 3441-3444
Author(s):  
Shiqing Lin ◽  
Dianan Yang ◽  
Jide Zhang ◽  
Tongzhu Li ◽  
Tang Chongqing ◽  
...  
Keyword(s):  
Frost Resistance ◽  
Fluorescence Induction ◽  
Chl A ◽  
In Vivo Fluorescence ◽  
Induction Kinetics ◽  
Fluorescence Induction Kinetics

scholarly journals Characteristics of Mixed Layer Depth and Its Effect on Concentration of Chlorophyll-a (Karakteristik Mixed Layer Depth dan Pengaruhnya Terhadap Konsentrasi Klorofil-a)

2015 ◽  
Vol 19 (4) ◽  
pp. 219 ◽  
Author(s):  
Novita Ayu Ryandhini ◽  
Muhammad Zainuri ◽  
Anastasia Rita Tisiana D. K.
Keyword(s):  
Chlorophyll A ◽  
Mixed Layer ◽  
Mixed Layer Depth ◽  
Vertical Movement ◽  
Water Masses ◽  
Homogeneous Layer ◽  
Indonesian Throughflow ◽  
Layer Depth ◽  
Current Activity ◽  
Chlorophyll A Content

Perairan Selat Badung memiliki karakteristik yang sebagian besar dipengaruhi oleh aktivitas Arus Lintas Indonesia (ARLINDO). Pencampuran massa air akibat pergerakan massa air vertikal menjadikan kondisi lapisan yang homogen, dimana nilai suhu, salinitas dan densitas berada pada nilai yang hampir sama di lapisan tertentu akan membentuk Mixed Layer Depth (MLD). Penelitian dilakukan untuk mengetahui karakteristik MLD dan pengaruhnya terhadap konsentrasi klorofil-a di Perairan Selat Badung, Bali. Metode pengukuran klorofil-a menggunakan spektrofotometri. Hasil penelitian menunjukkan bahwa suhu dan salinitas sebagai parameter MLD, membentuk lapisan yang homogen pada kedalaman yang bervariasi. Sebaran kandungan klorofil-a pada kedalaman MLD 12-23 m, menunjukkan nilai klorofil-a yang cenderung lebih tinggi pada permukaan perairan dibandingkan di perairan yang lebih dalam. Pada MLD kedalaman 12-60 m, menunjukkan bahwa kecenderungan kandungan klorofil-a lebih tinggi pada lapisan di kedalaman tersebut. Namun pada beberapa stasiun menunjukkan bahwa meskipun terdapat lapisan homogen yang cukup dalam, kandungan klorofil-a lebih tinggi di lapisan permukaan dibandingkan pada perairan yang lebih dalam. Kata Kunci: mixed layer depth, klorofil-a, perairan selat Badung Badung Strait characteristics is largely influenced by the ARLINDO (Indonesian Throughflow) current activity. The mixing of water masses due to the vertical movement of water masses, homogenized some range of layer (Mixed Layer Depth), whereas the value of temperature, salinity and density were about on the same range. The study was conducted to determine the characteristics of MLD and its influence on the concentration of chlorophyll-a of Badung Strait, Bali. Chlorophyll-a content was measured by using spectrophotometry method. The results showed that temperature and salinity as the MLD parameters, formed homogeneous layer (MLD) at varying depths. Distribution of MLD at depth of 12-23 m, indicating that chlorophyll-a consentration tends to be higher on the surface than at depth. In conditions at depth of 12-60 m, showed that chlorophyll-a higher on the depth, where a lot of MLD formed on the layer. However, in some stations showed that although there were quite a lot of homogeneous layer, chlorophyll-a consentration was higher on the surface than in the depth. Keywords: Mixed Layer Depth, Chlorophyll-a, Badung Strait

scholarly journals Autonomous profiling float observations of the high biomass plume downstream of the Kerguelen plateau in the Southern Ocean

2014 ◽  
Vol 11 (12) ◽  
pp. 17413-17462 ◽  
Author(s):  
M. Grenier ◽  
A. Della Penna ◽  
T. W. Trull
Keyword(s):  
Southern Ocean ◽  
Water Column ◽  
Mixed Layer ◽  
Dissolved Inorganic Carbon ◽  
Mixed Layer Depth ◽  
Light Limitation ◽  
Clear Correlation ◽  
Kerguelen Plateau ◽  
Layer Depth ◽  
Chl A

Abstract. Natural iron fertilisation from Southern Ocean islands results in high primary production and phytoplankton biomass accumulations readily visible in satellite ocean colour observations. These images reveal great spatial complexity with highly varying concentrations of chlorophyll, presumably reflecting both variations in iron supply and conditions favouring phytoplankton accumulation. To examine the second aspect, in particular the influences of variations in temperature and stratification, we deployed four autonomous profiling floats in the Antarctic Circumpolar Current near the Kerguelen plateau in the Indian sector of the Southern Ocean. Each "bio-profiler" measured more than 250 profiles of temperature (T), salinity (S), dissolved oxygen, chlorophyll fluorescence (Chl a), and particle backscatter in the top 300 m of the water column, sampling up to 5 profiles per day along meandering trajectories extending up to 1000 km. Comparison of surface Chl a estimates (top 50 m depth; analogous to values from satellite images) with total water column inventories revealed largely linear relationships, suggesting that dilution of chlorophyll by mixed layer depth variations plays only a minor role in the spatial distributions observed by satellite, and correspondingly that these images provide credible information on total and not just surface biomass accumulations. Regions of very high Chl a accumulation (1.5–10 μg L-1) were associated predominantly with a narrow T–S class of surface waters, which appears to derive from the northern Kerguelen plateau. In contrast, waters with only moderate Chl a enrichments (0.5–1.5 μg L-1) displayed no clear correlation with water properties, including no dependence on mixed layer depth, suggesting a diversity of sources of iron and/or its efficient dispersion across filaments of the plume. The lack of dependence on mixed layer depth also indicates a limited influence on production by light limitation. One float became trapped in a cyclonic eddy, allowing temporal evaluation of the water column in early autumn. During this period, decreasing surface Chl a inventories corresponded with decreases in oxygen inventories on sub-mixed layer density surfaces, consistent with significant export of organic matter and its respiration and storage as dissolved inorganic carbon in the ocean interior. These results are encouraging for the expanded use of autonomous observing platforms to study biogeochemical, carbon cycle, and ecological problems, although the complex blend of Lagrangian and Eulerian sampling achieved by the floats suggests that arrays rather than single floats will often be required.

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