scholarly journals ANN-BP model for Chl-a concentration estimation with in-situ collected hyperspectral refelctance in Lake Chagan, Jilin Province

2007 ◽  
Vol 19 (3) ◽  
pp. 275-282 ◽  
Author(s):  
SONG Kaishan ◽  
◽  
ZHANG Bai ◽  
WANG Zongming ◽  
DUAN Hongtao ◽  
...  
Keyword(s):  
Jilin Province ◽  
Chl A ◽  
Concentration Estimation ◽  
Lake Chagan ◽  
Bp Model

scholarly journals Temporal Variation of Chlorophyll-a Concentrations in Highly Dynamic Waters from Unattended Sensors and Remote Sensing Observations

Sensors ◽  
2018 ◽  
Vol 18 (8) ◽  
pp. 2699 ◽  
Author(s):  
Jian Li ◽  
Liqiao Tian ◽  
Qingjun Song ◽  
Zhaohua Sun ◽  
Hongjing Yu ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Water Quality ◽  
Chlorophyll Fluorescence ◽  
Chlorophyll A ◽  
Temporal Variations ◽  
Lake Area ◽  
Short Term ◽  
Chl A ◽  
Spatio Temporal

Monitoring of water quality changes in highly dynamic inland lakes is frequently impeded by insufficient spatial and temporal coverage, for both field surveys and remote sensing methods. To track short-term variations of chlorophyll fluorescence and chlorophyll-a concentrations in Poyang Lake, the largest freshwater lake in China, high-frequency, in-situ, measurements were collected from two fixed stations. The K-mean clustering method was also applied to identify clusters with similar spatio-temporal variations, using remote sensing Chl-a data products from the MERIS satellite, taken from 2003 to 2012. Four lake area classes were obtained with distinct spatio-temporal patterns, two of which were selected for in situ measurement. Distinct daily periodic variations were observed, with peaks at approximately 3:00 PM and troughs at night or early morning. Short-term variations of chlorophyll fluorescence and Chl-a levels were revealed, with a maximum intra-diurnal ratio of 5.1 and inter-diurnal ratio of 7.4, respectively. Using geostatistical analysis, the temporal range of chlorophyll fluorescence and corresponding Chl-a variations was determined to be 9.6 h, which indicates that there is a temporal discrepancy between Chl-a variations and the sampling frequency of current satellite missions. An analysis of the optimal sampling strategies demonstrated that the influence of the sampling time on the mean Chl-a concentrations observed was higher than 25%, and the uncertainty of any single Terra/MODIS or Aqua/MODIS observation was approximately 15%. Therefore, sampling twice a day is essential to resolve Chl-a variations with a bias level of 10% or less. The results highlight short-term variations of critical water quality parameters in freshwater, and they help identify specific design requirements for geostationary earth observation missions, so that they can better address the challenges of monitoring complex coastal and inland environments around the world.

Iron plays a role in nitrate drawdown by phytoplankton in Lake Erie surface waters as observed in lake-wide assessments

2012 ◽  
Vol 69 (2) ◽  
pp. 369-381 ◽  
Author(s):  
Sonya M. Havens ◽  
Christel S. Hassler ◽  
Rebecca L. North ◽  
Stephanie J. Guildford ◽  
Greg Silsbe ◽  
...  
Keyword(s):  
Surface Waters ◽  
Thermal Stratification ◽  
Lake Erie ◽  
Phytoplankton Community ◽  
Sampling Depth ◽  
Phytoplankton Pigment ◽  
Chl A ◽  
Dissolved Iron ◽  
Continuous Surface

Phytoplankton interactions with iron (Fe) were examined in surface waters of Lake Erie during summer thermal stratification. Lake-wide sampling in June and September 2005 was conducted using a continuous surface water sampler (1 m sampling depth) and in July at 18 hydrographic stations (5 m sampling depth). In situ measurements of photosynthetic efficiency (maximum quantum yield of photosystem II) and phytoplankton community composition were measured using fast repetition rate fluorometry and a phytoplankton pigment-specific fluorometer, respectively, during June and September. High ratios (73%–85%) of intracellular Fe to particulate Fe coincident with increases in chlorophyll a (Chl a) concentrations in the western and central basins in June and July imply that the majority of Fe in these regions was associated with intracellular pools. Correlations between intracellular Fe and Chl a were frequently observed when Heterokontophyta and Pyrrophyta dominated the phytoplankton community. Assimilation of Fe by the phytoplankton strongly influenced its partitioning between the dissolved and particulate phase. Dissolved iron (<0.45 µm) concentrations were proportional to Chl a concentrations and both dissolved iron and Chl a were inversely proportional to nitrate concentrations in July and September, suggesting that dissolved iron influenced both nitrate drawdown and Chl a concentrations in Lake Erie surface waters in summer.

scholarly journals Trichome abundance, chlorophyll content and the spectral coefficient for light absorption of Trichodesmium slicks observed in the Southwestern Atlantic

2020 ◽  
Vol 42 (2) ◽  
pp. 135-139
Author(s):  
Amália Maria Sacilotto Detoni ◽  
Aurea Maria Ciotti
Keyword(s):  
Natural Waters ◽  
Degradation Products ◽  
Spectral Feature ◽  
Quantitative Information ◽  
Southwestern Atlantic ◽  
Austral Spring ◽  
Chl A ◽  
Ocean Colour Remote Sensing ◽  
Break Region

Abstract Dense slicks of Trichodesmium were found in the shelf-break region in the Southwestern Atlantic during austral spring and autumn. A total of 14 slicks were sampled, and the absorption coefficients of phytoplankton (aph(λ)) indicated clear spectral features of phycobilin pigments. Although these samples showed low-degradation products and detrital importance, the chemotaxonomy, shape, and magnitude of aph(λ) indicated the importance of co-occurring species in the slicks. In addition to the difficulties of enumerating trichomes in situ, co-occurring species affect the expected chlorophyll-a (Chl-a) to trichome ratio, further complicating the detection of Trichodesmium by ocean colour remote sensing. Our results showed that trichome density could be predicted similarly by Chl-a and by aph(621), especially for trichome densities above 8000 trichomes L−1. The phycocyanin spectral feature is a potential source of quantitative information for the detection of Trichodesmium, but noninvasive techniques for quantifying the abundance of Trichodesmium in natural waters are necessary.

scholarly journals Improved MODIS-Aqua Chlorophyll-a Retrievals in the Turbid Semi-Enclosed Ariake Bay, Japan

2018 ◽  
Vol 10 (9) ◽  
pp. 1335 ◽  
Author(s):  
Meng Meng Yang ◽  
Joji Ishizaka ◽  
Joaquim I. Goes ◽  
Helga do R. Gomes ◽  
Elígio de Raús Maúre ◽  
...  
Keyword(s):  
Chlorophyll A ◽  
Red Tide ◽  
Atmospheric Correction ◽  
Ariake Bay ◽  
Band Ratio ◽  
Simple Method ◽  
Chl A ◽  
Switching Algorithm ◽  
Economic Significance

The accurate retrieval of chlorophyll-a concentration (Chl-a) from ocean color satellite data is extremely challenging in turbid, optically complex coastal waters. Ariake Bay in Japan is a turbid semi-enclosed bay of great socio-economic significance, but it suffers from serious water quality problems, particularly due to red tide events. Chl-a derived from the MODerate resolution Imaging Spectroradiometer (MODIS) sensor on satellite Aqua in Ariake Bay was investigated, and it was determined that the causes of the errors were from inaccurate atmospheric correction and inappropriate in-water algorithms. To improve the accuracy of MODIS remote sensing reflectance (Rrs) in the blue and green bands, a simple method was adopted using in situ Rrs data. This method assumes that the error in MODIS Rrs(547) is small, and MODIS Rrs(412) can be estimated from MODIS Rrs(547) using a linear relation between in situ Rrs(412) and Rrs(547). We also showed that the standard MODIS Chl-a algorithm, OC3M, underestimated Chl-a, which was mostly due to water column turbidity. A new empirical switching algorithm was generated based on the relationship between in situ Chl-a and the blue-to-green band ratio, max(Rrs(443), Rrs(448)/Rrs(547), which was the same as the OC3M algorithm. The criterion of Rrs(667) of 0.005 sr−1 was used to evaluate the extent of turbidity for the switching algorithm. The results showed that the switching algorithm performed better than OC3M, and the root mean square error (RMSE) of estimated Chl-a decreased from 0.414 to 0.326. The RMSE for MODIS Chl-a using the recalculated Rrs and the switching algorithm was 0.287, which was a significant improvement from the RMSE of 0.610, which was obtained using standard MODIS Chl-a. Finally, the accuracy of our method was tested with an independent dataset collected by the local Fisheries Research Institute, and the results revealed that the switching algorithm with the recalculated Rrs reduced the RMSE of MODIS Chl-a from 0.412 of the standard to 0.335.

Protein Synthesis by Lake Plankton Measured Using in situ Carbon Dioxide and Sulfate Assimilation

1987 ◽  
Vol 44 (12) ◽  
pp. 2102-2117 ◽  
Author(s):  
Russell L. Cuhel ◽  
David R. S. Lean
Keyword(s):  
Carbon Dioxide ◽  
Protein Synthesis ◽  
Carbon Fixation ◽  
Total Carbon ◽  
Light Limitation ◽  
Sulfate Assimilation ◽  
Sulfate Uptake ◽  
Chl A ◽  
Total Sulfate

Sequential 4- to 6-h in situ measurements of carbon dioxide and sulfate uptake showed midday deepening of the depth of Pmax and photoinhibition of upper water column samples. Analysis of subcellular fractions accentuated total uptake measurements, with net protein synthesis providing a direct measure of growth. The percentage of carbon assimilated into protein was smallest at the depth of maximum photosynthesis and increased with light limitation. Summed incubations agreed well with all-day deployments for total carbon fixation and protein synthesis. Assimilation numbers were consistently low (<2.5 g C∙g Chl a−1∙h-1 with integrated (0–20 m) areal production of 616–1467 mg C∙m−2 and 7.5–32.4 mg S∙m−2 during the light day. Nonreductive sulfate assimilation (predominantly ester-SO4−) accounted for up to 40% of the total sulfate uptake when diatoms predominated. Protein synthesis measured with 35S (200–1000 mg protein∙m−2 during the light day) increased 57–89% overnight. Hourly rates were similar during light and scotophase incubations. Night metabolism substantially altered the biochemical composition (e.g. protein, lipid, and carbohydrate) of the plankton with respect to newly incorporated carbon. Combined plant-specific H14CO3− and general microbial 3SSO42− techniques suggested algal dominance in the mixed layer.

scholarly journals Phytoplankton Biomass and the Hydrodynamic Regime in NEOM, Red Sea

2021 ◽  
Vol 13 (11) ◽  
pp. 2082
Author(s):  
Nikolaos Papagiannopoulos ◽  
Dionysios Raitsos ◽  
Georgios Krokos ◽  
John Gittings ◽  
Robert Brewin ◽  
...  
Keyword(s):  
Red Sea ◽  
Late Summer ◽  
Marine Conservation ◽  
Conservation Strategy ◽  
Late Winter ◽  
Northwestern Part ◽  
Local Circulation ◽  
Chl A ◽  
Under Construction

NEOM (short for Neo-Mustaqbal) is a $500 billion coastal city megaproject, currently under construction in the northwestern part of the Red Sea, off the coast of Tabuk province in Saudi Arabia, and its success will rely on the preservation of biodiverse marine ecosystems. Monitoring the variability of ecological indicators, such as phytoplankton, in relation to regional environmental conditions, is the foundation for such a goal. We provide a detailed description of the phytoplankton seasonal cycle of surface waters surrounding NEOM using satellite-derived chlorophyll-a (Chl-a) observations, based on a regionally-tuned product of the European Space Agency’s Ocean Colour Climate Change Initiative, at 1 km resolution, from 1997 to 2018. The analysis is also supported with in situ cruise datasets and outputs of a state-of-the-art high-resolution hydrodynamic model. The open waters of NEOM follow the oligotrophic character of the Northern Red Sea (NRS), with a peak during late winter and a minimum during late summer. Coral reef-bound regions, such as Sindala and Sharma, are characterised by higher Chl-a concentrations that peak during late summer. Most of the open waters around NEOM are influenced by the general cyclonic circulation of the NRS and local circulation features, while shallow reef-bound regions are more isolated. Our analysis provides the first description of the phytoplankton seasonality and the oceanographic conditions in NEOM, which may support the development of a regional marine conservation strategy.

SentiLake - Sentinel-2 satellite data-based service for monitoring of Latvian lakes

2020 ◽  
Author(s):  
Dainis Jakovels ◽  
Agris Brauns ◽  
Jevgenijs Filipovs ◽  
Tuuli Soomets
Keyword(s):  
Water Quality ◽  
Satellite Data ◽  
Ecological Status ◽  
Quality Parameters ◽  
Water Bodies ◽  
Water Quality Parameters ◽  
Chl A ◽  
Regular Monitoring ◽  
Sentinel 2

&lt;p&gt;Lakes and water reservoirs are important ecosystems providing such services as drinking water, recreation, support for biodiversity as well as regulation of carbon cycling and climate. There are about 117 million lakes worldwide and a high need for regular monitoring of their water quality. European Union Water Framework Directive (WFD) stipulates that member states shall establish a programme for monitoring the ecological status of all water bodies larger than 50 ha, in order to ensure future quality and quantity of inland waters. But only a fraction of lakes is included in in-situ monitoring networks due to limited resources. In Latvia, there are 2256 lakes larger than 1 ha covering 1.5% of Latvian territory, and approximately 300 lakes are larger than 50 ha, but only 180 are included in Inland water monitoring program, in addition, most of them are monitored once in three to six years. Besides, local municipalities are responsible for the management of lakes, and they are also interested in the assessment of ecological status and regular monitoring of these valuable assets.&amp;#160;&lt;/p&gt;&lt;p&gt;Satellite data is a feasible way to monitor lakes over a large region with reasonable frequency and support the WFD status assessment process. There are several satellite-based sensors (eg. MERIS, MODIS, OLCI) available specially designed for monitoring of water quality parameters, however, they are limited only to use for large water bodies due to a coarse spatial resolution (250...1000 m/pix). Sentinel-2 MSI is a space-borne instrument providing 10...20 m/pix multispectral data on a regular basis (every 5 days at the equator and 2..3 days in Latvia), thus making it attractive for monitoring of inland water bodies, especially the small ones (&lt;1 km&lt;sup&gt;2&lt;/sup&gt;).&amp;#160;&lt;/p&gt;&lt;p&gt;Development of Sentinel-2 satellite data-based service (SentiLake) for monitoring of Latvian lakes is being implemented within the ESA PECS for Latvia program. The pilot territory covers two regions in Latvia and includes more than 100 lakes larger than 50 ha. Automated workflow for selecting and processing of available Sentinel-2 data scenes for extracting of water quality parameters (chlorophyll-a and TSM concentrations) for each target water body has been developed. Latvia is a northern country with a frequently cloudy sky, therefore, optical remote sensing is challenging in or region. However, our results show that 1...4 low cloud cover Sentinel-2 data acquisitions per month could be expected due to high revisit frequency of Sentinel-2 satellites. Combination of C2X and C2RCC processors was chosen for the assessment of chl-a concentration showing the satisfactory performance - R&lt;sup&gt;2&lt;/sup&gt; = 0,82 and RMSE = 21,2 &amp;#181;g/l. Chl-a assessment result is further converted and presented as a lake quality class. It is expected that SentiLake will provide supplementary data to limited in situ data for filling gaps and retrospective studies, as well as a visual tool for communication with the target audience.&lt;/p&gt;

scholarly journals Bromocarbons in the tropical coastal and open ocean atmosphere during the 2009 Prime Expedition Scientific Cruise (PESC-09)

2014 ◽  
Vol 14 (15) ◽  
pp. 8137-8148 ◽  
Author(s):  
M. S. Mohd Nadzir ◽  
S. M. Phang ◽  
M. R. Abas ◽  
N. Abdul Rahman ◽  
A. Abu Samah ◽  
...  
Keyword(s):  
Chlorophyll A ◽  
Statistical Tests ◽  
Open Ocean ◽  
Common Source ◽  
Sampling Point ◽  
Coastal Regions ◽  
Chl A ◽  
June July ◽  
Strait Of Malacca

Abstract. Atmospheric concentrations of very short-lived species (VSLS) bromocarbons, including CHBr3, CH2Br2, CHCl2Br, CHClBr2, and CH2BrCl, were measured in the Strait of Malacca and the South China and Sulu–Sulawesi seas during a two-month research cruise in June–July 2009. The highest bromocarbon concentrations were found in the Strait of Malacca, with smaller enhancements in coastal regions of northern Borneo. CHBr3 was the most abundant bromocarbon, ranging from 5.2 pmol mol−1 in the Strait of Malacca to 0.94 pmol mol−1 over the open ocean. Other bromocarbons showed lower concentrations, in the range of 0.8–1.3 pmol mol−1 for CH2Br2, 0.1–0.5 pmol mol−1 for CHCl2Br, and 0.1–0.4 pmol mol−1 for CHClBr2. There was no significant correlation between bromocarbons and in situ chlorophyll a, but positive correlations with both MODIS and SeaWiFS satellite chlorophyll a. Together, the short-lived bromocarbons contribute an average of 8.9 pmol mol−1 (range 5.2–21.4 pmol mol−1) to tropospheric bromine loading, which is similar to that found in previous studies from global sampling networks (Montzka et al., 2011). Statistical tests showed strong Spearman correlations between brominated compounds, suggesting a common source. Log–log plots of CHBr3/CH2Br2 versus CHBr2Cl/CH2Br2 show that both chemical reactions and dilution into the background atmosphere contribute to the composition of these halocarbons at each sampling point. We have used the correlation to make a crude estimate of the regional emissions of CHBr3 and to derive a value of 32 Gg yr−1 for the Southeast (SE) Asian region (10° N–20° S, 90–150° E). Finally, we note that satellite-derived chlorophyll a (chl a) products do not always agree well with in situ measurements, particularly in coastal regions of high turbidity, meaning that satellite chl a may not always be a good proxy for marine productivity.

scholarly journals Development of a three-dimensional growth prediction model for the Japanese scallop in Funka Bay, Japan, using OGCM and MODIS

2015 ◽  
Vol 72 (9) ◽  
pp. 2684-2699 ◽  
Author(s):  
Yang Liu ◽  
Sei-Ichi Saitoh ◽  
Yu Ihara ◽  
Satoshi Nakada ◽  
Makoto Kanamori ◽  
...  
Keyword(s):  
Prediction Model ◽  
Three Dimensional ◽  
Temperature Data ◽  
Japanese Scallop ◽  
Growth Prediction ◽  
Chl A ◽  
Funka Bay ◽  
Dimensional Growth ◽  
In Situ Observations

Abstract The Japanese scallop (Patinopecten (Mizuhopecten) yessoensis) is an important commercial species in Funka Bay, Japan, where it is farmed using the hanging culture method. Our study was based on 6 years (from 2006 to 2011) of monthly in situ observations of scallop growth at Yakumo station. To produce a basic spatial distribution dataset, we developed an interpolation solution for the shortage of Chl-a concentration data available from the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite. Additionally, we integrated four-dimensional variational (4D-VAR) assimilation water temperature data from ocean general circulation models (OGCMs), with four vertical levels (6, 10, 14, and 18 m) from the sea surface. Statistical models, including generalized additive models (GAMs) and generalized linear models, were applied to in situ observation data, satellite data, and 4D-VAR data to identify the influence of environment factors (interpolated Chl-a, temperature, and depth) on the growth of scallops, and to develop a three-dimensional growth prediction model for the Japanese scallops in Funka Bay. We considered three methods to simulate the growth process of scallops (accumulation, summation, and product), and used them to select the most suitable model. All the interpolated Chl-a concentrations and 4D-VAR temperature data were verified by shipboard data. The results revealed that GAM, using an accumulation method that was based on a combination of integrated temperature, integrated log Chl-a, depth, and number of days, was best able to predict the vertical and spatial growth of the Japanese scallop. The predictions were verified by in situ observations from different depths (R2 = 0.83–0.94). From the distribution of three-dimensional predicted scallop growth maps at each depth, it was suggested that the growth of the Japanese scallop was most favourable at 6 m and least favourable at 18 m, although variations occurred in each aquaculture region in different years. These variations were probably due to the ocean environment and climate variation.

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