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Search Results: 1 - 10 of 51739 matches for " Chlorophyll-A "
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Mapping Potential Fishing Grounds in Lake Malawi Using AVHRR and MODIS Satellite Imagery  [PDF]
Geoffrey Chavula, Harlod Sungani, Kenneth Gondwe
International Journal of Geosciences (IJG) , 2012, DOI: 10.4236/ijg.2012.33065
Abstract: This paper discusses a procedure that was developed to delineate potential fishing grounds in Lake Malawi using data on chlorophyll-a concentration derived from Moderate-resolution Imaging Spectroradiometer (MODIS/AQUA) in combination with lake surface temperature (LST) data obtained from Advanced Very High Resolution Radiometer (AVHRR) and MODIS/Terra satellite sensors. The paper draws from findings of studies [1,2] on development of algorithms for estimating chlorophyll-a and lake surface temperature in Lake Malawi from satellite imagery, respectively. To estimate chlorophyll concentration (a proxy for phytoplankton) in Lake Malawi using data from MODIS satellite imagery, in situ measurements of chlorophyll concentration were conducted at three selected sampling stations over the southeastern arm of Lake Malawi concurrent with satellite image acquisitions. These were regressed on chlorophyll-a concentration values obtained from Ocean Color (MODIS/AQUA) Data using SeaWIFS Data Analysis System (SeaDAS) software. From this, an equation for estimating chlorophyll-a concentration in Lake Malawi from MODIS satellite imagery was developed and used for mapping the spatial distribution of chlorophyll-a concentration in the lake. Since Lake Malawi is an oligotrophic lake, with an average value of chlorophyll concentration of 1 μg/L, areas in the lake with relatively high chlorophyll-a concentration were identified as potential locations for the development of the fishery industry. Estimation of lake surface temperature using satellite imagery involved two main activities. Firstly, in situ measurements of lake surface temperature were conducted at the three selected sampling stations over Lake Malawi concurrent with satellite image acquisitions. The second activity involved downloading and processing AVHRR and MODIS/Terra satellite imagery. AVHRR data covered the period September 1997 to February 1998 whereas MODIS/Terra data covered the period May to November, 2006. Both MODIS Land Surface Temperature (MOD11A1) and Ocean Color Sea Surface Temperature (SST) were downloaded from EOS Gateway website and processed into lake surface temperature. Two glass thermometers were used to measure temperature directly from the lake surface at a depth of 0 - 7.0 cm (i.e., skin temperature) and the average of the two readings was recorded as the lake surface temperature at a particular sampling station. Observed temperatures were regressed on remotely sensed data. ER Mapper was employed in drawing maps showing the distribution of lake surface temperature using
An Innovative and High-Speed Technology for Seawater Monitoring of Asinara Gulf (Sardinia-Italy)  [PDF]
Maria Sighicelli, Ileana Iocola, Daniele Pittalis, Antonella Luglié, Bachisio Mario Padedda, Silvia Pulina, Massimo Iannetta, Ivano Menicucci, Luca Fiorani, Antonio Palucci
Open Journal of Marine Science (OJMS) , 2014, DOI: 10.4236/ojms.2014.41005
Abstract:

Laser induced fluorescence technique for sea water monitoring allows no-time consuming, non-invasive and non-destructive controls. In this study, the performance of the new shipboard laser spectrofluorometric CAS-PER (Compact and Advanced Laser SpectrometerENEA Patent) for monitoring phytoplankton community composition was examined. The prototype CASPER is based on double laser excitation of water samples in the UV (266 nm) and visible (405 nm) spectral region and a double water filtration in order to detect both quantitative data, such as chromophoric dissolved organic matter (CDOM), proteins-like components (tyrosine, tryptophan), algal pigments (chlorophylls a and b, phycoerythrin, phycocyanin, different pigments of the carotenoid groups) and qualitative data on the presence of hydrocarbons and oil pollutants. Sea water samples from different depths have been collected and analyzed from August 2010 through November 2011 in the Gulf of Asinara (N-W Sardinia). Several sampling stations were selected as sites with different degree of pollution. The accuracy and the reliability of data obtained by CASPER have been evaluated comparing the results with other standard measurements such as: Chlorophyll a (Chl a) data obtained by spectrophotometric method and total phytoplankton abundance in terms of density and class composition. Spectral deconvolution technique was developed and integrated with CASPER system to assess and characterize a marker pigments and organic compounds in situ and in vivo. Field studies confirmed CASPER system capability to effectively discriminate characteristic spectra of fluorescent water constituents, contributing to decrease the time-consuming manual analysis of the water samples in

Chlorophyll-a Estimation in Tachibana Bay by Data Fusion of GOCI and MODIS Using Linear Combination Index Algorithm  [PDF]
Yuji Sakuno, Keita Makio, Kazuhiko Koike, Maung-Saw-Htoo-Thaw  , Shigeru Kitahara
Advances in Remote Sensing (ARS) , 2013, DOI: 10.4236/ars.2013.24032
Abstract:

This study discusses the fusion of chlorophyll-a (Chl.a) estimates around Tachibana Bay (Nagasaki Prefecture, Japan) obtained from MODIS and GOCI satellite data. First, the equation of GOCI LCI was theoretically calculated on the basis of the linear combination index (LCI) method proposed by Frouin et al. (2006). Next, assuming a linear relationship between them, the MODIS LCI and GOCI LCI methods were compared by using the Rayleigh reflectance product dataset of GOCI and MODIS, collected on July 8, July 25, and July 31, 2012. The results were found to be correlated significantly. GOCI Chl.a estimates of the finally proposed method favorably agreed with the in-situ Chl.a data in Tachibana Bay.

Island Activities Detected by VIIRS and Validation with AIS  [PDF]
Ichio Asanuma, Daisuke Hasegawa, Takashi Yamaguchi, Jong Geol Park, Kenneth James Mackin
Advances in Remote Sensing (ARS) , 2018, DOI: 10.4236/ars.2018.73012
Abstract: A possibility to monitor the reclamation activities by remote sensing was discussed. The lights observed in the night time by Day Night Band (DNB) of Visible Infrared Imaging Radiometer Suite (VIIRS), ocean color observed in the day time by visible bands of VIIRS were the tools to monitor the surface activities, and the Automated Information System (AIS) was used to verify the types and number of vessels associated with the reclamation activities. The lights as the radiance from the surface were monitored by the object based analysis, where the object was defined as a radius of 5 km from the center of the Mischief Reef in the South China Sea (SCS). The time history of surface lights exhibited the increase of the radiance from January to May 2015 and the radiance was kept in the certain level to December 2016 with some variations. The ocean color, chlorophyll-a concentration as a proxy of sediments, showed an increase from February to June 2015 and returned to a low concentration in August 2015. According to the historical data of AIS, the number of dredgers has increased from February to August 2015 and the maximum number of dredgers was recorded in June 2015. The timing of increase of lights from surface, increase of chlorophyll-a concentration, and increase of number of vessels are consistent.
Modeling chlorophyll-a and dissolved oxygen concentration in tropical floodplain lakes (Paraná River , Brazil)
Rocha, RRA.;Thomaz, SM.;Carvalho, P.;Gomes, LC.;
Brazilian Journal of Biology , 2009, DOI: 10.1590/S1519-69842009000300005
Abstract: the need for prediction is widely recognized in limnology. in this study, data from 25 lakes of the upper paraná river floodplain were used to build models to predict chlorophyll-a and dissolved oxygen concentrations. akaike's information criterion (aic) was used as a criterion for model selection. models were validated with independent data obtained in the same lakes in 2001. predictor variables that significantly explained chlorophyll-a concentration were ph, electrical conductivity, total seston (positive correlation) and nitrate (negative correlation). this model explained 52% of chlorophyll variability. variables that significantly explained dissolved oxygen concentration were ph, lake area and nitrate (all positive correlations); water temperature and electrical conductivity were negatively correlated with oxygen. this model explained 54% of oxygen variability. validation with independent data showed that both models had the potential to predict algal biomass and dissolved oxygen concentration in these lakes. these findings suggest that multiple regression models are valuable and practical tools for understanding the dynamics of ecosystems and that predictive limnology may still be considered a powerful approach in aquatic ecology.
Spatio-Temporal Variations of Microphytobenthos in the Botafogo and Siri estuaries (norteast - Brazil)
Murolo, Priscila Porchat de Assis;Carvalho, Paulo Vladmir Vandenberg da Costa;Carvalho, Monica Lucia Botter;Souza-Santos, Lilia Pereira de;Santos, Paulo Jorge Parreira dos;
Brazilian Journal of Oceanography , 2006, DOI: 10.1590/S1679-87592006000100002
Abstract: spatio-temporal variations of microphytobenthic biomass were investigated in the botafogo and siri estuaries, pernambuco - brazil. samples were taken during low water (bi-monthly) from february to december, 2003. three sampling stations were located in each estuary, in both midlittoral and sublittoral areas. clear spatial and temporal variations were found for both chlorophyll-a and phaeopigment concentrations. in botafogo, chlorophyll-a had 34% of total variation explained by mra from nitrogen and phosphorus concentrations, while only 16% of total variation was thus explained from nitrogen concentration in the siri estuary. phaeopigments had 39% of total variation explained by mra from nitrogen concentration and salinity in the botafogo estuary and 58% of total variation was similarly explained from nitrogen concentration in the siri estuary. nitrogen was discriminated by the b coefficients as the most important factor in the explanation of the microphytobenthic pigments variations in the botafogo estuary. the data of this study emphasize the role of nutrients and suggest that both estuaries show evidence of eutrophication.
Using rem ote sensed data and G IS technique to estimate surface chlorophyll-a of Chaohu Lake
Cheng Chengqi,Yin Chengqing
环境科学学报(英文版) , 1992,
Abstract: The thematic mapper(TM)images from Landsat-V satellite are characterized by a short acquired period(16 days per cycle),and high spatial and spectral resolution.It is cheap and convenient to establish a dynamic monitoring system for water quality in large lakes by combining TM image data and measured data with a chemical method.In this paper the TM image digitized and GIS technology have been used to acquire digital remote sensing data.At the time the TM image were taken,samples ofchlorophyll-afrom the surface water of Chaohu Lake were colleeted and analyzed.Comparing the TM image digitized data with the measured ehlorophyll-a data,the relationships have been found and quantitative models have been established.Applying the model as supported by a GIS,the map ofchlorophyll-a distribution in the surface of Chaohu Lake has been produced.The average concentration of surface chlorophyll-a of Chaohu Lake is calculated.
The Identification of Fishing Ground Area with MODIS Satellite Image (Case Study: South Coast of West Java)
Dudung Muhally Hakim,Ketut Wikantika,Nengah Widiadnyana,Asmi M. Napitu
ITB Journal of Engineering Science , 2006,
Abstract: According to UNCLOS, Indonesian marine territorial covers an area equal to around 2.8 million square kilometers inner archipelagic seas. Though the Indonesian water region is very wide, the resource within it is not yet been exploited optimally. Indonesia still has problems that have to be copped with, including identification of marine fishing ground areas. This report proposes a technology to make the fish-catching be more efficient and effective with the help of MODIS satellite image in term of Surface Temperature and chlorophyll-a computation. Data conversion from digital number to Water Brightness Temperature are performed. The determination of potential fishing ground area were conducted based on temperature and chlorophyll-a parameters which serve as an indicator of upwelling and observations were carried out on parameters which show this phenomenon. Based on the result, during May 2004 the upwelling process were not happened yet, and it seems to occur in June 2004. It showes by the decreasing of water temperature in South Coast of West Java particularly between the border of West Java and Central of Java. This phenomenon acts as an indicator for the raising of primer productivity and will takes about one month after upwelling to the bloom of phytoplankton.
Spectral Geometric Triangle Properties of Chlorophyll-A Inversion in Taihu Lake Based on TM Data  [PDF]
Jun Chen, Zhenhe Wen, Zhengqing Xiao
Journal of Water Resource and Protection (JWARP) , 2011, DOI: 10.4236/jwarp.2011.31008
Abstract: The main objective of this study was to develop and validate the applicability of the Area Chlorophyll-a Concentration Retrieved Model (ACCRM), Height Chlorophyll-a Concentration Retrieved Model (HCCRM), Angle Chlorophyll-a Concentration Retrieved Model (AgCCRM), and Ratio Model of TM2/TM3 (RM) in estimating the chlorophyll-a concentration in Case II water bodies, such as Taihu Lake in Jiangsu Province, China. Water samples were collected from 23 stations on the 27th and 28th of October, 2003. The four empirical models were calibrated against the calibration dataset (samples from 19 stations) and validated using the validation dataset (samples from 4 stations). The regression analysis showed higher correlation coefficients for the ACCRM and the HCCRM than for the AgCCRM and the Ratio Model; and the HCCRM was slightly superior to the ACCRM. The performance of the ACCRM and the HCCRM was validated, and the ACCRM underestimated concentration values more than the HCCRM. The distribution of chlorophyll-a concentrations in Taihu Lake on October 27, 2003 was estimated based on the Landsat/TM data using the ACCRM and the HCCRM. Both models indicated higher chlorophyll-a concentrations in the east, north and center of the lake, but lower concentrations in the south. The accuracy of results obtained from the HCCRM and the ACCRM were also supported by the validation dataset. The study revealed that the HCCRM and the ACCRM had the best potential for accurately assessing the chlorophyll-a concentration in the highly turbid water bodies.
Support Vector Regression Model of Chlorophyll-a during Spring Algal Bloom in Xiangxi Bay of Three Gorges Reservoir, China  [PDF]
Hua-Jun Luo, De-Fu Liu, Ying-Ping Huang
Journal of Environmental Protection (JEP) , 2012, DOI: 10.4236/jep.2012.35052
Abstract: To study the relationship between chlorophyll-a and environmental variables during spring algal bloom in Xiangxi Bay of Three Gorges Reservoir, the support vector regression (SVR) model was established. In surveys, 11 stations have been investigated and 264 samples were collected weekly from March 4 to May 13 in 2007 and February 16 to May 10 in 2008. The parameters in SVR model were optimized by leave one out cross validation. The squared correlation coefficient R2 and the cross validated squared correlation coefficient Q2 of the optimal SVR model are 0.8202 and 0.7301, respectively. Compared with stepwise multiple linear regression and back propagation artificial neural network models using external validation, the SVR model has been shown to perform well for regression with the predictive squared correlation coefficient R2pred value of 0.7842 for the test set.
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