An Inherent Optical Properties Data Processing System for Achieving Consistent Ocean Color Products From Different Ocean Color Satellites

We used field measurements and multimission satellite data to evaluate how well an inherent optical properties (IOPs) data processing system performed at correcting the residual error of the atmospheric correction in satellite remote sensing reflectance (R-rs) and how well the system simultaneously minimized intermission biases between different remote sensing systems. We developed the IOPs data processing system as a semianalytical algorithm called IDAS. Our results show that IDAS generates accurate and consistent IOPs products from two ocean color missions: Sea-viewing Wide Field-of-View Sensor (SeaWiFS) and Moderate Resolution Imaging Spectroradiometer Aqua (MODISA). Specifically, with "high-quality" SeaWiFS and MODISA R-rs data, IDAS provided temporally consistent IOPs products for the oligotrophic open ocean resulting in an annual mean intermission difference of less than 3%, which is significantly lower than what a quasi-analytical algorithm (QAA) provided. We used IDAS to generate a long time series of b(b)(555) from the Northwest Atlantic Subtropical Gyre using SeaWiFS (1998 to 2002) and MODISA (2003 to 2017) images. Our results show that the IDAS-derived annual b(b)(555) decreased monotonically by 2.81% per decade from 1998 to 2017. Comparing the IDAS-generated annual trend for b(b)(555) to the same data processed with the QAA algorithm, we found that the QAA results differed because of impacts of the residual errors of the atmospheric correction and intermission biases. The differences in the annual trends existed despite the same temporal changing patterns of in situ particulate organic carbon existing in the Sargasso Sea and in the satellite chlorophyll-a concentration in the Northwest Atlantic Subtropical Gyre

A simple method for estimating macroalgae area under clouds on MODIS imagery

The presence of clouds interferes with optical remote sensing monitoring of macroalgae blooms. To solve this problem, we propose a simple method for estimating macroalgae area under clouds (Area_cloud_GT) on MODIS imagery using the principle behind the lowpass filter. The method is based on a rectangle with clouds and eight identical adjacent rectangles surrounding it that contain macroalgae. The cloud rectangle is a central ‘pixel’ (Cloud) and the eight adjacent rectangles are ‘pixels’ GT1–GT8. The core operation is to calculate the central ‘pixel’ value, i.e., the macroalgae coverage rate in the Cloud rectangle. The macroalgae area detected by semi-simultaneous fine resolution images in the same region was taken as the ‘real’ value. A comparison of the estimation results and the ‘real’ value shown that the mean relative difference between them (MRD) was 30.09% when the time interval of the images within 10 minutes. When the time interval was over 3 hours, the MRD was more than 60%. The MRD increased significantly with increasing time interval because of the constant movement of the macroalgae and the limitations of the remote sensing image. The results indicate that this simple method is effective to a certain extent. These results can provide a reference for the quantitative analysis of green tide

CDOM absorption properties of natural water bodies along extreme environmental gradients

We present absorption properties of colored dissolved organic matter (CDOM) sampled in six different water bodies along extreme altitudinal, latitudinal, and trophic state gradients. Three sites are in Norway: the mesotrophic Lysefjord (LF), Samnangerfjord (SF), and Røst Coastal Water (RCW); two sites are in China: the oligotrophic Lake Namtso (LN) and the eutrophic Bohai Sea (BS); and one site is in Uganda: the eutrophic Lake Victoria (LV). The site locations ranged from equatorial to subarctic regions, and they included water types from oligotrophic to eutrophic and altitudes from 0 m to 4700 m. The mean CDOM absorption coefficients at 440 nm [ a CDOM (440) aCDOM(440) ] and 320 nm [ a CDOM (320) aCDOM(320) ] varied in the ranges 0.063–0.35 m −1 −1 and 0.34–2.28 m −1 −1 , respectively, with highest values in LV, Uganda and the lowest in the high-altitude LN, Tibet. The mean spectral slopes S 280−500 S280−500 and S 350−500 S350−500 were found to vary in the ranges of 0.017–0.032 nm −1 −1 and 0.013–0.015 nm −1 −1 , respectively. The highest mean value for S 280−500 S280−500 as well as the lowest mean value for S 350−500 S350−500 were found in LN. Scatter plots of S 280−500 S280−500 versus a CDOM (440) aCDOM(440) and a CDOM (320) aCDOM(320) values ranges revealed a close connection between RCW, LF, and SF on one side, and BS and LV on the other side. CDOM seems to originate from terrestrial sources in LF, SF, BS, and LV, while RCW is characterized by autochthonous-oceanic CDOM, and LN by autochthonous CDOM. Photobleaching of CDOM is prominent in LN, demonstrated by absorption towards lower wavelengths in the UV spectrum. We conclude that high altitudes, implying high levels of UV radiation and oligotrophic water conditions are most important for making a significant change in CDOM absorption properties.publishedVersio

The influence of summer hypoxia on sedimentary phosphorus biogeochemistry in a coastal scallop farming area, North Yellow Sea

In situ field investigations coupled with laboratory incubations were employed to explore the surface sedimentary phosphorus (P) cycle in a mariculture area adjacent to the Yangma Island suffering from summer hypoxia in the North Yellow Sea. Five forms of P were fractionated, namely exchangeable P (Ex-P), iron-bound P (Fe-P), authigenic apatite (Ca-P), detrital P (De-P) and organic P (OP). Total P (TP) varied from 13.42 to 23.88 mu mol g(-1) with the main form of inorganic P (IP). The benthic phosphate (DIP) fluxes were calculated based on incubation experiments. The results show that the sediment was an important source of P in summer with similar to 39% of the bioavailable P (Bio-P) recycled back into the water column. However, the sediment acted a sink of P in autumn. The benthic DIP fluxes were mainly controlled by the remobilizing of Fe-P, Ex-P and OP under contrasting redox conditions. In August (hypoxia season), similar to 0.92 mu mol g(-1) of Fe-P and similar to 0.52 mu mol g(-1) of OP could be transformed to DIP and released into water, while similar to 0.36 mu mol g(-1) of DIP was adsorbed to clay minerals. In November (non-hypoxia season), however, similar to 0.54 mu mol g(-1) of OP was converted into DIP, while similar to 0.55 mu mol g(-1) and similar to 0.28 mu mol g(-1) of DIP was adsorbed to clay minerals and bind to iron oxides. Furthermore, scallop farming activities also affected the P mobilization through biological deposition and reduced hydrodynamic conditions. The burial fluxes of P varied from 11.67 to 20.78 mu mol cm(-2) yr(-1) and its burial efficiency was 84.7-100%, which was consistent with that in most of the marginal seas worldwide. This study reveals that hypoxia and scallop farming activities can significantly promote sedimentary P mobility, thereby causing high benthic DIP flux in coastal waters. (C) 2020 Elsevier B.V. All rights reserved

Geochemistry of organic carbon in surface sediments of a summer hypoxic region in the coastal waters of northern Shandong Peninsula

The geochemistry of sedimentary organic matter (SOM) in coastal areas is complex due to its multiple sources and intricate hydrological features. In this study, the biogenic element concentrations and stable carbon (delta C-13) and nitrogen (delta N-15) isotopic compositions in the coastal surface sediments of northern Shandong Peninsula, along with some parameters related to water quality, were analyzed to investigate the temporal-spatial variations in SOM and the processes that control its distribution. The results revealed that marine autogenous organic matter is a major contributor to SOM, accounting for 75.4 +/- 3.3%, 60.8 +/- 6.6% and 67.4 +/- 10.3% in August and November 2015 and March 2016, respectively. In summer, TOC and TN concentrations were significantly higher than those in autumn and spring. The relatively high abundances of SOM were found in the offshore areas in summer and spring, which was contrary to those in autumn. Riverine discharge, nutrients, primary productivity and dissolved oxygen (DO) dynamics could all influence the composition and contents of SOM in different seasons. In summer, high primary productivity and hypoxia condition led to high SOM values. In comparison, SOM contents were relatively low due to sufficient DO in bottom water in autumn and spring. Dissolved nutrients in seawater could affect the accumulation of autogenous organic matter by impacting upon primary production. In summer, nitrate in surface water had the most obvious effects on autogenous organic carbon (AOC) and may be the principal factor of limiting the growth of phytoplankton. In autumn, nitrate as well as dissolved silicate had more effects on AOC storage. However, phosphate had the most obvious influence on AOC storage in spring

Remote sensing image classification method based on evidence theory and decision tree

Remote sensing image classification is an important and complex problem. Conventional remote sensing image classification methods are mostly based on Bayesian subjective probability theory, but there are many defects for its uncertainty. This paper firstly introduces evidence theory and decision tree method. Then it emphatically introduces the function of support degree that evidence theory is used on pattern recognition. Combining the D-S evidence theory with the decision tree algorithm, a D-S evidence theory decision tree method is proposed, where the support degree function is the tie. The method is used to classify the classes, such as water, urban land and green land with the exclusive spectral feature parameters as input values, and produce three classification images of support degree. Then proper threshold value is chosen and according image is handled with the method of binarization. Then overlay handling is done with these images according to the type of classifications, finally the initial result is obtained. Then further accuracy assessment will be done. If initial classification accuracy is unfit for the requirement, reclassification for images with support degree of less than threshold is conducted until final classification meets the accuracy requirements. Compared to Bayesian classification, main advantages of this method are that it can perform reclassification and reach a very high accuracy. This method is finally used to classify the land use of Yantai Economic and Technological Development Zone to four classes such as urban land, green land and water, and effectively support the classification. © 2010 Copyright SPIE - The International Society for Optical Engineering

Nutrient and chlorophyll a anomaly in red-tide periods of 2003-2008 in Sishili Bay, China

Sishili Bay is the most important aquiculture and tourism area for the city of Yantai, China; however, red tides occurred frequently and have caused huge economic losses in this bay in recent years. To gain a better understanding of the local ecological environments in the bay, we conducted this research between 2003 and 2008 to analyze variations in nutrients and chlorophyll (chl-a) during high frequency red tide period (May to September). The results show that the chl-a concentration increased from 2.70 in 2003 to 7.26 mg/m(3) in 2008, while the concentration of total inorganic nitrogen (TIN) and silicate (SiO(3)-Si) increased lineally from 5.18 and 1.45 mu mol/L in 2003 to 18.57 and 9.52 mu mol/L in 2008, respectively, and the annual phosphate (PO(4)-P) varied between 0.15 and 0.46 mu mol/L. Special attention was given to a red tide in August 2007 occurred when water temperature was high and nutrient concentrations increased sharply because of a heavy rainfall. Overall, the results show the P limitation in Sishili Bay, and reveal that red tides were caused by eutrophication from terrestrial inputs and local warm weather, particularly during rainy periods. Therefore, to control red tide, greater efforts should be made to reduce sewage discharges into Sishili Bay, particularly during rainfall seasons.Sishili Bay is the most important aquiculture and tourism area for the city of Yantai, China; however, red tides occurred frequently and have caused huge economic losses in this bay in recent years. To gain a better understanding of the local ecological environments in the bay, we conducted this research between 2003 and 2008 to analyze variations in nutrients and chlorophyll (chl-a) during high frequency red tide period (May to September). The results show that the chl-a concentration increased from 2.70 in 2003 to 7.26 mg/m(3) in 2008, while the concentration of total inorganic nitrogen (TIN) and silicate (SiO3-Si) increased lineally from 5.18 and 1.45 mu mol/L in 2003 to 18.57 and 9.52 mu mol/L in 2008, respectively, and the annual phosphate (PO4-P) varied between 0.15 and 0.46 mu mol/L. Special attention was given to a red tide in August 2007 occurred when water temperature was high and nutrient concentrations increased sharply because of a heavy rainfall. Overall, the results show the P limitation in Sishili Bay, and reveal that red tides were caused by eutrophication from terrestrial inputs and local warm weather, particularly during rainy periods. Therefore, to control red tide, greater efforts should be made to reduce sewage discharges into Sishili Bay, particularly during rainfall seasons

A review of environment problems in the coastal sea of South China

The coastal sea of South China provided an important habitat for protection and propagation of marine organisms. Rapid economic development and human activities, such as wastewater discharge, reclamation, overfishing and aquaculture in the South China Sea had already resulted in environmental degradation, and thus caused sharp contradictions between exploitation and protection of the coastal sea of South China. In this present article, the main environment problems and degradation trends were reviewed based on literatures and other sources of information, which mainly referenced nutrient pollution, persistent organic pollution and metal pollution, decrease of biodiversity, reduction of marine habitat and frequent natural and ecological disasters. The current efforts in China on protecting the environment in the coastal sea of South China were discussed, which included improving legislation by formulating a series of laws and regulations at national or local level, setting up natural reserves, and supporting research projects. There were many challenges regarding policy, management and science research to protect and sustain the coastal sea of South China, such as imperfect legal and administrative systems, lack of public participation, poor financial support and lack of monitoring and evaluation. Finally, some recommendations were put forward for the sake of the sustainable use of the environment in the coastal sea of South China, including reinforcing the planning of marine resource exploitation and use through integrated coastal zone management, strengthening the marine environment and protection awareness of the public, and scientifically establishing the fishery spawning spots and aquatic reserves.The coastal sea of South China provided an important habitat for protection and propagation of marine organisms. Rapid economic development and human activities, such as wastewater discharge, reclamation, overfishing and aquaculture in the South China Sea had already resulted in environmental degradation, and thus caused sharp contradictions between exploitation and protection of the coastal sea of South China. In this present article, the main environment problems and degradation trends were reviewed based on literatures and other sources of information, which mainly referenced nutrient pollution, persistent organic pollution and metal pollution, decrease of biodiversity, reduction of marine habitat and frequent natural and ecological disasters. The current efforts in China on protecting the environment in the coastal sea of South China were discussed, which included improving legislation by formulating a series of laws and regulations at national or local level, setting up natural reserves, and supporting research projects. There were many challenges regarding policy, management and science research to protect and sustain the coastal sea of South China, such as imperfect legal and administrative systems, lack of public participation, poor financial support and lack of monitoring and evaluation. Finally, some recommendations were put forward for the sake of the sustainable use of the environment in the coastal sea of South China, including reinforcing the planning of marine resource exploitation and use through integrated coastal zone management, strengthening the marine environment and protection awareness of the public, and scientifically establishing the fishery spawning spots and aquatic reserves