Reflectance in the Red and Near Infra-Red Ranges of the Spectrum as Tool for Remote Chlorophyll Estimation in Inland Waters: Lake Kinneret Case Study

Signature analysis of reflectance spectra was used for the selection of the most suitable spectral bands for remote sensing of chlorophyll in inland waters. The parameters of the reflectance peak near 700 nm were employed for construction of algorithms for chlorophyll determination. The best model, validated by independent data sets, enabled estimation of chlorophyll concentration with an error \u3c 0.6 mg/m3 for period of low Chl concentration and \u3c 6.5 mg/m3 for period of the phytoplankton bloom. For the purpose of chlorophyll mapping in Lake Kinneret, the use of three relatively narrow spectral bands was sufficient. Radiometric data were also used to simulate radiances in the channels of TM Landsat and to find algorithm for chlorophyll assessment. The ratio (TM2-TM3)/TMl was used to retrieve chlorophyll in the range 3-10 mg/m3 with an error of \u3c 1 mg.m-3; the ratio TM4/TM3 was used to map chlorophyll in the range 10-200 mg/m3 with 10 gradations

NIR-red reflectance-based algorithms for chlorophyll-a estimation in mesotrophic inland and coastal waters: Lake Kinneret case study

A variety of models have been developed for estimating chlorophyll-a (Chl-a) concentration in turbid and productive waters. All are based on optical information in a few spectral bands in the red and near-infra-red regions of the electromagnetic spectrum. The wavelength locations in the models used were meticulously tuned to provide the highest sensitivity to the presence of Chl-a and minimal sensitivity to other constituents in water. But the caveat in these models is the need for recurrent parameterization and calibration due to changes in the biophysical characteristics of water based on the location and/or time of the year. In this study we tested the performance of NIR-red models in estimating Chl-a concentrations in an environment with a range of Chl-a concentrations that is typical for coastal and mesotrophic inland waters. The models with the same spectral bands as MERIS, calibrated for small lakes in the Midwest U.S., were used to estimate Chla concentration in the subtropical Lake Kinneret (Israel), where Chl-a concentrations ranged from 4 to 21 mgm-3 during four field campaigns. A two-band model without reparameterization was able to estimate Chl-a concentration with a root mean square error less than 1.5 mgm-3. Our work thus indicates the potential of the model to be reliably applied without further need of parameterization and calibration based on geographical and/or seasonal regimes

Molecular mechanisms of cell death: recommendations of the Nomenclature Committee on Cell Death 2018.

Over the past decade, the Nomenclature Committee on Cell Death (NCCD) has formulated guidelines for the definition and interpretation of cell death from morphological, biochemical, and functional perspectives. Since the field continues to expand and novel mechanisms that orchestrate multiple cell death pathways are unveiled, we propose an updated classification of cell death subroutines focusing on mechanistic and essential (as opposed to correlative and dispensable) aspects of the process. As we provide molecularly oriented definitions of terms including intrinsic apoptosis, extrinsic apoptosis, mitochondrial permeability transition (MPT)-driven necrosis, necroptosis, ferroptosis, pyroptosis, parthanatos, entotic cell death, NETotic cell death, lysosome-dependent cell death, autophagy-dependent cell death, immunogenic cell death, cellular senescence, and mitotic catastrophe, we discuss the utility of neologisms that refer to highly specialized instances of these processes. The mission of the NCCD is to provide a widely accepted nomenclature on cell death in support of the continued development of the field

Reflectance in the Red and Near Infra-Red Ranges of the Spectrum as Tool for Remote Chlorophyll Estimation in Inland Waters: Lake Kinneret Case Study

Signature analysis of reflectance spectra was used for the selection of the most suitable spectral bands for remote sensing of chlorophyll in inland waters. The parameters of the reflectance peak near 700 nm were employed for construction of algorithms for chlorophyll determination. The best model, validated by independent data sets, enabled estimation of chlorophyll concentration with an error \u3c 0.6 mg/m3 for period of low Chl concentration and \u3c 6.5 mg/m3 for period of the phytoplankton bloom. For the purpose of chlorophyll mapping in Lake Kinneret, the use of three relatively narrow spectral bands was sufficient. Radiometric data were also used to simulate radiances in the channels of TM Landsat and to find algorithm for chlorophyll assessment. The ratio (TM2-TM3)/TMl was used to retrieve chlorophyll in the range 3-10 mg/m3 with an error of \u3c 1 mg.m-3; the ratio TM4/TM3 was used to map chlorophyll in the range 10-200 mg/m3 with 10 gradations

Remote sensing of chlorophyll in Lake Kinneret using highspectral- resolution radiometer and Landsat TM: spectral features of reflectance and algorithm development

High-resolution reflectance spectra in the range of 400-850 nm were obtained from Lake Kinneret during a period when dense populations of the dinoflagellate Peridinium gatunense dominated the phytoplankton. Chlorophyll (ChI) concentrations ranged from 5.1 to 185 mg m-3 and from 2.4 to 187.5 mg m-3 in the samples of two independent experiments. The most prominent features of the reflectance spectra were: (i) a wide minimum from 400 to 500 nm; (ii) a maximum at 550-570 nm, which did not surpass 3% in samples with high ChI concentration (\u3e20 mg m-3), indicating a strong absorption by pigments in the green range of the spectrum; (iii) a minimum at 676 nm; this was ~ 1 % and was almost insensitive to variation in ChI concentration \u3e10 mg m-3; (iv) a maximum reflectance showed near 700 nm; its magnitude and position were highly dependent on chlorophyll concentration. Highspectral- resolution data were used as a guideline for selection of the most suitable spectral bands for chlorophyll remote sensing. Models were devised, based on the calculation of the integrated area above the baseline from 670 to 850 nm and the reflectance maximal height within this range. Some algorithms already used in previous studies were tested and showed a plausible degree of accuracy when applied to the current data base. However, novel models devised in this study improved substantially the accuracy of ChI estimation by remotely sensed data, by reducing the estimation error from \u3e11 to 6.5 mg m-3. Those models were validated by an independent data set where ChI concentration ranged over two orders of magnitude. The use of three relatively narrow spectral bands was sufficient for ChI mapping in Lake Kinneret. Therefore, a relatively simple sensor, measuring only a few bands will be employed in future applications for ChI monitoring in inland waters. Radiometric data were also used to simulate radiances in the channels of TM Landsat and to find the algorithm for ChI assessment. The ratio of channel 4 to channel 3 was used and enabled ChI estimation with an error of \u3c15 mg\u3em-3. This algorithm was employed to map ChI in the entire area of Lake Kinneret with 10 gradations

Occurrence of high concentrations of a unique degradation product of chlorophyll-a in particles residing below the thermocline throughout a period of oxygen depletion in Lake Kinneret

An unrecognized chlorophyllous pigment, designated Pheob4, was the most abundant degradation product of chlorophyll-a (Chla) in the hypolimimnion, benthic boundary layer and sedimenting particles in Lake Kinneret in June-July 1997, when a prolonged period of residual oxygen concentration was found below the thermocline. The highest concentration of Pheob4 was found in the benthic boundary layer, where it reached as high concentration as 2 μg l-1. In sediment traps positioned below the thermocline Pheob4 constituted from about 5 to 20% of the Chl-a concentration and in bottom sediments from 5 to 185%. Pheob4 was not detected in epilimnetic water samples, but was found in sediment traps located within the oxygenated water column, within the range of surface wave action. Comparison of regular traps, with traps poisoned by formaldehyde indicates that the importance of Pheob4- containing particles in the sedimentation flux is relatively low, and that the bulk of Pheob4 found in the bottom sediment is apparently a result of Chl-a transformation in situ by biological activity. The timing and location of Pheob4 appearance coincided with the lake compartments where denitrification apparently took place. This suggests that Pheob4 may be used as a target pigment to trace organic matter processing under transient conditions in the water column and on the bottom sediments. Pheob4 was tentatively identified as 132, 172 cyclophaeophorbide-a enol. But, since the identification was done on a different system than the one used for the analysis of most of the samples, further investigation is required to verify that finding

Absorption spectroscopy of colored dissolved organic carbon in Georgia (USA) rivers: the impact of molecular size distribution

Dissolved organic carbon (DOC) was collected in six rivers that transect the coastal plain of Georgia in July 1999 and February 2000. DOC concentrations ranged from 4.9 to 40.7 g m-3 and from 7.1 to 40.5 g m-3, respectively. The absorption coefficient at 440 nm was highly correlated with DOC concentration, suggesting that the optical parameter may be utilized for rapid estimation of DOC in these waters. The isolated DOC was separated into fractions of operationally defined molecular size, using an ultrafiltration technique that yielded three fractions: <10 ("small"), 10-50 ("medium") and >50 ("large") kilodalton. The smallest fraction was the most abundant (>50%) in 4 rivers in July and in all rivers in February, and considerably more abundant than in previous years. The wavelength-dependent absorption of the total DOC and its fractions showed approximately uniform shape of a curve declining exponentially with the increase of wavelength. The average slope of logarithmically transformed curves was 0.0151 and 0.0159 nm-1, for the material collected in July and February, respectively and showed a dependence on DOC molecular size. In unfractionated DOC samples, the mass-specific light absorption determined at 440 nm was on average 0.33 m2 g-1 in July, and 0.26 m2 g-1 in February. The mass-specific absorption coefficient in all fractions ranged between 0.085 and 1.347 m2 g-1 in July and between 0.085 and 1.877 m2 g-1 in February, and was positively correlated with the molecular size of the measured samples. The results of the reported study clearly suggest that the specific absorption coefficient of the yellow substance is an outcome of the relative contribution of its different size fractions