Phytoplankton Pigment Concentrations Research Articles

Drought can cause phytoplankton growth intensification in Barra Bonita reservoir

In this research, we investigated the possible consequences of the 2012–2014 drought in Southeastern Brazil on growing phytoplankton in a eutrophic reservoir. Weather has direct influence to phytoplankton communities and, consequently, underwater light climate which drives important processes in aquatic systems. Absorption coefficient of phytoplankton pigment (aφ) and chlorophyll-a (Chl-a) concentration were determined in laboratory in order to analyze the interference of phytoplankton biomass over light. In addition, a historical monthly rainfall series in the reservoir was analyzed. Results showed clearly the strong drought effect over the monthly useful volume and flow rate. Both of them play important roles to water column mixing and retention time which increase the nutrients availability in the system and phytoplankton biomass. Chl-a concentration and aphy values were extremely high [maximum Chl-a of 797.8 mg m−3 and aφ(440) of almost 6 m−1 in October]. So, more attention should be paid to water quality in long episodes of drought as occurred from 2012 to 2014.

Effects of intensive mariculture on the sediment environment as revealed by phytoplankton pigments in a semi-enclosed bay, South China Sea

Phytoplankton pigment concentrations in the surface sediments of a fish and oyster farm in Dapeng Cove, South China Sea, were measured monthly to investigate the effects of mariculture on the environment from December 2011 to December 2012. The highest contents of the identified phytopigments, sulphides and total organic carbon in the surface sediments were all found at the fish farm, followed by the oyster farm; the lowest contents were detected at the control site. Fucoxanthin in the surface sediments was the most abundant carotenoid and was significantly correlated with chlorophyll a (Chl a; r = 0.922, P < 0.01). This finding suggested that the deposited diatoms could be the main source of the Chl a concentration. Besides a differential sedimentation of phytoplankton (i.e. higher downflux at fish and oyster site than that at control site), we assume that the extent of pigment diminution from the fish site to control site was also controlled by the chemical conditions of the surface sediments. The fish farm provided the most optimum preservation conditions for the phytopigments and was a good sink for phytodetritus among the three sites because of its anoxic and reductive characteristics. Phytoplankton pigments could be useful biomarkers to evaluate the influence of mariculture on sediment environment.

Halocarbon emissions and sources in the equatorial Atlantic Cold Tongue

Abstract. Halocarbons from oceanic sources contribute to halogens in the troposphere, and can be transported into the stratosphere where they take part in ozone depletion. This paper presents distribution and sources in the equatorial Atlantic from June and July 2011 of the four compounds bromoform (CHBr3), dibromomethane (CH2Br2), methyl iodide (CH3I) and diiodomethane (CH2I2). Enhanced biological production during the Atlantic Cold Tongue (ACT) season, indicated by phytoplankton pigment concentrations, led to elevated concentrations of CHBr3 of up to 44.7 and up to 9.2 pmol L−1 for CH2Br2 in surface water, which is comparable to other tropical upwelling systems. While both compounds correlated very well with each other in the surface water, CH2Br2 was often more elevated in greater depth than CHBr3, which showed maxima in the vicinity of the deep chlorophyll maximum. The deeper maximum of CH2Br2 indicates an additional source in comparison to CHBr3 or a slower degradation of CH2Br2. Concentrations of CH3I of up to 12.8 pmol L−1 in the surface water were measured. In contrary to expectations of a predominantly photochemical source in the tropical ocean, its distribution was mostly in agreement with biological parameters, indicating a biological source. CH2I2 was very low in the near surface water with maximum concentrations of only 3.7 pmol L−1. CH2I2 showed distinct maxima in deeper waters similar to CH2Br2. For the first time, diapycnal fluxes of the four halocarbons from the upper thermocline into and out of the mixed layer were determined. These fluxes were low in comparison to the halocarbon sea-to-air fluxes. This indicates that despite the observed maximum concentrations at depth, production in the surface mixed layer is the main oceanic source for all four compounds and one of the main driving factors of their emissions into the atmosphere in the ACT-region. The calculated production rates of the compounds in the mixed layer are 34 ± 65 pmol m−3 h−1 for CHBr3, 10 ± 12 pmol m−3 h−1 for CH2Br2, 21 ± 24 pmol m−3 h−1 for CH3I and 384 ± 318 pmol m−3 h−1 for CH2I2 determined from 13 depth profiles.

Reconstruction of hyperspectral reflectance for optically complex turbid inland lakes: test of a new scheme and implications for inversion algorithms.

A new scheme has been proposed by Lee et al. (2014) to reconstruct hyperspectral (400 - 700 nm, 5 nm resolution) remote sensing reflectance (Rrs(λ), sr-1) of representative global waters using measurements at 15 spectral bands. This study tested its applicability to optically complex turbid inland waters in China, where Rrs(λ) are typically much higher than those used in Lee et al. (2014). Strong interdependence of Rrs(λ) between neighboring bands (≤ 10 nm interval) was confirmed, with Pearson correlation coefficient (PCC) mostly above 0.98. The scheme of Lee et al. (2014) for Rrs(λ) re-construction with its original global parameterization worked well with this data set, while new parameterization showed improvement in reducing uncertainties in the reconstructed Rrs(λ). Mean absolute error (MAERrs(λi)) in the reconstructed Rrs(λ) was mostly < 0.0002 sr-1 between 400 and 700nm, and mean relative error (MRERrs(λi)) was < 1% when the comparison was made between reconstructed and measured Rrs(λ) spectra. When Rrs(λ) at the MODIS bands were used to reconstruct the hyperspectral Rrs(λ), MAERrs(λi) was < 0.001 sr-1 and MRERrs(λi) was < 3%. When Rrs(λ) at the MERIS bands were used, MAERrs(λi) in the reconstructed hyperspectral Rrs(λ) was < 0.0004 sr-1 and MRERrs(λi) was < 1%. These results have significant implications for inversion algorithms to retrieve concentrations of phytoplankton pigments (e.g., chlorophyll-a or Chla, and phycocyanin or PC) and total suspended materials (TSM) as well as absorption coefficient of colored dissolved organic matter (CDOM), as some of the algorithms were developed from in situ Rrs(λ) data using spectral bands that may not exist on satellite sensors.

Using empirical orthogonal functions derived from remote-sensing reflectance for the prediction of phytoplankton pigment concentrations

Abstract. The composition and abundance of algal pigments provide information on phytoplankton community characteristics such as photoacclimation, overall biomass and taxonomic composition. In particular, pigments play a major role in photoprotection and in the light-driven part of photosynthesis. Most phytoplankton pigments can be measured by high-performance liquid chromatography (HPLC) techniques applied to filtered water samples. This method, as well as other laboratory analyses, is time consuming and therefore limits the number of samples that can be processed in a given time. In order to receive information on phytoplankton pigment composition with a higher temporal and spatial resolution, we have developed a method to assess pigment concentrations from continuous optical measurements. The method applies an empirical orthogonal function (EOF) analysis to remote-sensing reflectance data derived from ship-based hyperspectral underwater radiometry and from multispectral satellite data (using the Medium Resolution Imaging Spectrometer – MERIS – Polymer product developed by Steinmetz et al., 2011) measured in the Atlantic Ocean. Subsequently we developed multiple linear regression models with measured (collocated) pigment concentrations as the response variable and EOF loadings as predictor variables. The model results show that surface concentrations of a suite of pigments and pigment groups can be well predicted from the ship-based reflectance measurements, even when only a multispectral resolution is chosen (i.e., eight bands, similar to those used by MERIS). Based on the MERIS reflectance data, concentrations of total and monovinyl chlorophyll a and the groups of photoprotective and photosynthetic carotenoids can be predicted with high quality. As a demonstration of the utility of the approach, the fitted model based on satellite reflectance data as input was applied to 1 month of MERIS Polymer data to predict the concentration of those pigment groups for the whole eastern tropical Atlantic area. Bootstrapping explorations of cross-validation error indicate that the method can produce reliable predictions with relatively small data sets (e.g., &lt; 50 collocated values of reflectance and pigment concentration). The method allows for the derivation of time series from continuous reflectance data of various pigment groups at various regions, which can be used to study variability and change of phytoplankton composition and photophysiology.

행암만 해양환경요인과 플랑크톤 군집구조의 변동

We analyzed with HPLC (High Performance Liquid Chromatography) analysis photosynthetic pigments and environmental factors, microscopic observations of the phytoplankton and zooplankton in the seawater every month from February 2009 to November 2010 in Haengam Bay. The level of dissolved inorganic nutrients was the highest between July and September, when freshwater influx was at its peak, whereas chlorophyll a levels were the highest in April and August. Also, phytoplankton pigment concentration increased when dissolved inorganic nutrients are carried into nearshore waters by rainfall runoff. Based on identification of phytoplankton and photosynthetic pigments results, diatoms were mainly dominant while dinoflagellate populations increased at July and August 2009, May 2010. The zooplankton communities are dominated in terms of Noctiluca scintillans. The contribution of Noctiluca scintillans in 2010 accounts for approximately 77.3% of the total zooplankton. Distribution patterns over time of zooplankton in the seasonal distribution of phytoplankton showed a different pattern.

Bio-Optical Characteristics of the Northern Gulf of California during June 2008

Bio-optical variables in the Northern Gulf of California were analyzed using in situ and satellite data obtained during a cruise in June 2008. The study area was divided into three bio-optical regions: Upper Gulf (UG), Northern Gulf (NG), and Great Isles (GI). Each region was characterized according to phytoplankton pigment concentration, phytoplankton and nonpigmented material spectral absorption coefficients, and spectral reflectance. Observed patterns were an indication of the shift in bio-optical conditions from north to south going from turbid and eutrophic waters to mesotrophic ones. Although there was a good agreement between satellite and in situ Chla (RMSE ±33%), an overestimation of in situ Chla was observed. This was partly explained by the presence of nonalgal particles, as well as the influence of desert and continental aerosols, which is generally overcorrected in the standard processing. The UG and NG could be considered as Case 2 waters, but they did exhibit different bio-optical characteristics. This implies that both biological and optical properties should be invoked to better understand water reflectance variability in the study region and its implications for the remote sensing of Chla and biogeochemical processes.

Evaluation of cyanobacteria cell count detection derived from MERIS imagery across the eastern USA

Inland waters across the United States (US) are at potential risk for increased outbreaks of toxic cyanobacteria blooms events resulting from elevated water temperatures and extreme hydrologic events attributable to climate change and increased nutrient loadings associated with intensive agricultural practices. Current monitoring efforts are limited in scope due to resource limitations, analytical complexity, and data integration efforts. The goals of this study were to validate an algorithm for satellite imagery that could potentially be used to monitor surface cyanobacteria events in near real-time to provide a compressive monitoring capability for freshwater lakes (>100ha). The algorithm incorporated narrow spectral bands specific to the European Space Agency's (ESA's) MEdium Resolution Imaging Spectrometer (MERIS) instrument that were optimally oriented at phytoplankton pigment absorption features including phycocyanin at 620nm. A validation of derived cyanobacteria cell counts was performed using available in situ data assembled from existing monitoring programs across eight states in the eastern US over a 39-month period (2009–2012). Results indicated that MERIS provided robust estimates for low (10,000–109,000 cells/mL) and very high (>1,000,000 cells/mL) cell enumeration ranges (approximately 90% and 83%, respectively). However, the results for two intermediate ranges (110,000–299,000 and 300,000–1,000,000 cells/mL) were substandard, at approximately 28% and 40%, respectively. The confusion associated with intermediate cyanobacteria cell count ranges was largely attributed to the lack of available taxonomic data and distinction of natural counting units for the in situ measurements that would have facilitated conversions between cell counts and cell volumes. The results of this study document the potential for using MERIS-derived cyanobacteria cell count estimates to monitor freshwater lakes (>100ha) across the eastern US.

Estimation of Marine Primary Productivity From Satellite-Derived Phytoplankton Absorption Data

The global ocean net primary production (NPP) was estimated from satellite-derived information using a phytoplankton pigment absorption ( <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">${a}_{{\bf ph}}$</tex> </formula> )-based model. Satellite-derived spectral-averaged <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">${a}_{{\bf ph}}$</tex> </formula> was used as the key predictor of phytoplankton photosynthetic efficiency in the model. The <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">${a}_{{\bf ph}}$</tex> </formula> -based model yields an annual integrated NPP of approximately <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$\bf 55~\hbox{Pg C year}^{-1}$</tex> </formula> for the global oceans over the period 2003–2010. The accuracy of the model was validated by comparing it with in situ NPP at three sites, and the logarithmic root-mean-square error of the model was approximately 0.18. The model performance was also compared with two existing NPP models (chlorophyll-based model and carbon-based model) in terms of spatial distribution, seasonal cycles, and accuracy. The comparison results indicated that the <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">${a}_{{\bf ph}}$</tex> </formula> -based model has improved accuracy in describing NPP variation for monthly timescales compared with the other two models. We were surprised to find that the spatial distribution of global ocean NPP provided by the <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">${a}_{{\bf ph}}$</tex> </formula> -based model is more similar to the carbon-based model than the chlorophyll-based model. Although many additional studies need to be conducted, the performance of the <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">${a}_{{\bf ph}}$</tex> </formula> -based model in this work may encourage us to estimate ocean NPP from satellite-derived phytoplankton pigment absorption.

Photoprotective acclimation of micro- and nano-size phytoplankton assemblages in the Indian sector of the Southern Ocean

Phytoplankton in the mixed layer is exposed to increasing levels of light when transported to the surface layer of the ocean. The photoprotective response of natural assemblages of phytoplankton can differ among community structures. We investigated photoprotective acclimation and xanthophyll cycle pigments in size-fractionated natural phytoplankton assemblages during the austral summer in the Indian sector of the Southern Ocean. We estimated concentrations of phytoplankton pigments in the micro-size fractions (>20 μm) and nano-size fractions (2–20 μm) by subtracting concentrations in the 67 %) and in deck incubation bottles under variable light conditions (>75 % of the temporal variation) for the micro-size fractions suggest a higher potential for photoprotective acclimation than for the nano-size fractions. Decreases in DT/(DD + DT) with increases in the optical depth of the mixed layer (ζMLD) suggest that larger variations in light availability in the mixed layer might predict lower values of DT/(DD + DT) at the surface, regardless of cell size.

Evaluating the importance of phytoplankton community structure to the optical properties of the Santa Barbara Channel, California

Observations from the Santa Barbara Channel, California, were used to evaluate relationships among optical properties and phytoplankton community structure. Phytoplankton community structure was determined by statistically analyzing 10 diagnostic phytoplankton pigment concentrations using empirical orthogonal function (EOF) analysis. The first four EOF modes explained 82% of phytoplankton community structure variability and were interpreted as a mixed community mode composed mostly of nanoplankton, a mode dominated by microplankton (diatoms and dinoflagellates), a mode describing alternating diatom and dinoflagellate dominance, and a mode reflecting picoplankton presence. Variations in colored dissolved organic matter (CDOM) and phytoplankton absorption spectra were related to changes of the mixed microplankton modal amplitudes. Characteristics of the CDOM spectrum were further dependent on whether diatoms or dinoflagellates were dominant. The particle backscattering coefficient was significantly correlated with EOF modes describing the mixed microplankton and the picoplankton communities. The influence of phytoplankton community structure was also seen in the performance of standard ocean color algorithms using the in situ data set. The present results demonstrate that many optical characteristics vary significantly with changes in phytoplankton community structure and suggest that improvements in remote‐sensing algorithms will require model coefficients to vary accordingly. Further, changes in phytoplankton community composition affect both dissolved and particle absorption and scattering properties, not simply the phytoplankton‐specific properties, creating challenges for the development of algorithms aimed at assessing phytoplankton community structure from satellite observations.

Coefficients of summer spectral absorption of particulate matter in Xin'anjiang Reservoir (Lake Qiandao)

通过对2013年夏季新安江水库(千岛湖)53个站点悬浮颗粒物的吸收光谱进行研究,系统分析了总颗粒物吸收系数a_p(λ)、非藻类颗粒物吸收系数a_d(λ)和浮游藻类光谱吸收系数a_ph(λ)的变化规律以及影响因素.结果表明:总颗粒物吸收除西北河流区上游段外,其他各站点均呈现出明显的浮游藻类吸收特性,反映新安江水库总颗粒物中浮游藻类贡献较高.全库a_p(440)在0.068~0.629m^-1之间变化,西北河流区总颗粒物吸收系数显著大于其他水域,而湖泊区与西南河流区则显著小于其他水域.非藻类颗粒物吸收光谱随着波长增加大致呈现出指数函数衰减的规律,其光谱斜率S_d均值为8.52±1.62μm^-1,存在显著的空间差异,但整体偏低,与新安江水库无机颗粒物含量低有关.a_d(440)与浮游藻类色素浓度存在显著的线性相关,表明夏季新安江水库非藻类颗粒物可能主要来源于浮游藻类降解.浮游藻类的光谱吸收在440和675nm附近有明显的吸收峰.a_ph(440)和a_ph(675)存在显著的空间差异,其与浮游藻类色素浓度存在极显著的正线性关系,而与总悬浮颗粒物浓度相关性较弱.;The spectral absorption coefficients of total particles a_p(λ), nonalgal particles a_d(λ) and phytoplankton a_ph(λ) in Xin'anjiang Reservoir(Lake Qiandao) were studied based on the data of 53 sampling sites in the summer of 2013. The results showed that the absorption spectra of total particles were similar to those of phytoplankton except the data at sites 9 and 10. It indicated that phytoplankton made larger contribution to the total particles. The values of the total particulate matter at 440nm a_p(440) ranged between 0.068 and 0.629 m^-1 in the water body. Moreover, the values of a_p(λ) in the northwestern area were significantly larger than those in other areas, while the values of a_p(λ) in the lake district and the southwestern riverine areas were the smallest. Absorption coefficients of nonalgal particles decreased exponentially from the short to the long wavelength. There were marked spatial variations of the exponential spectral slope coefficients of nonalgal particles S_d with the average value of 8.52±1.62μ m^-1. However, the values of S_d in Xin'anjiang Reservoir were generally low due to the low values of the inorganic suspended solids. Significant positive relationships were found between a_d(440) and phytoplankton pigment concentrations, suggesting that the degradation of phytoplankton was an important source of the nonalgal particles in summer. There were distinctive absorption peaks at the wavelength of 440 and 675nm in the absorption spectra of phytoplankton. In addition, there were significant spatial variations of the phytoplankton absorption coefficients at 440nm (a_ph(440)) and 675nm (a_ph(675)). Significant positive linear relationships were found between a_ph(440), a_ph(675) and phytoplankton pigment concentration, respectively, while weak relationships were showed between a_ph(440), a_ph(675) and the total suspended solids, respectively.

Bio-Optical Inversion in Highly Turbid and Cyanobacteria-Dominated Waters

Phytoplankton pigment absorption data from algal-bloom-dominated waters are highly desirable to better understand the primary productivity and carbon uptake by algal biomass in a regional scale. However, retrieving phytoplankton pigment absorption coefficients, in turbid and hypereutrophic waters, from above-surface remote sensing reflectance (Rrs) is often challenging because of the optical complexity of the water body. In this paper, a quasi-analytical algorithm has been parameterized using in situ data to retrieve inherent optical properties from Rrs(λ) in highly turbid productive aquaculture ponds, where the phytoplankton absorption coefficient (3.44-37.67 m-1 ) contributes 54 % of the total absorption at 443 nm (4.99-47.21 m-1). The model was validated using an independent data set by comparing the model-derived optical parameters with in situ measured values. The absolute percentage error (assuming no error in the in situ measurements) of the estimated total absorption coefficient at( λ) varied from 15.22 % to 24.13 % within 413-665 nm, and the overall average error was 19.87 %. Maximum and minimum errors occurred at 443 and 665 nm, respectively. Similarly, the percentage error for the phytoplankton absorption coefficient aφ(λ) varied from 15.9 % to 41.27 % within the 413-665-nm range, and the average error was 27.24 %. The spectral shape of modeled aφ(λ) matched very well (R2 = 0.97) with the measured aφ(λ). A supplementary method was also developed to retrieve first-order estimates of colored detrital matter absorption coefficients aCDM( λ) from subsurface remote sensing reflectance rrs( λ) using an empirical approach. Results reveal that the retrieval accuracy of aφ(λ) improved after incorporating the first-order estimates of aCDM(λ) in the algorithm.

Differential response of planktonic primary, bacterial, and dimethylsulfide production rates to static vs. dynamic light exposure in upper mixed-layer summer sea waters

Abstract. Microbial plankton experience short-term fluctuations in total solar irradiance and in its spectral composition as they are vertically moved by turbulence in the oceanic upper mixed layer (UML). The fact that the light exposure is not static but dynamic may have important consequences for biogeochemical processes and ocean–atmosphere fluxes. However, most biogeochemical processes other than primary production, like bacterial production or dimethylsulfide (DMS) production, are seldom measured in sunlight and even less often in dynamic light fields. We conducted four experiments in oligotrophic summer stratified Mediterranean waters, where a sample from the UML was incubated in ultraviolet (UV)-transparent bottles at three fixed depths within the UML and on a vertically moving basket across the same depth range. We assessed the response of the phyto- and bacterioplankton community with physiological indicators based on flow cytometry singe-cell measurements, fast repetition rate fluorometry (FRRf), phytoplankton pigment concentrations and particulate light absorption. Dynamic light exposure caused a subtle disruption of the photoinhibition and photoacclimation processes associated with ultraviolet radiation (UVR), which slightly alleviated bacterial photoinhibition but did not favor primary production. Gross DMS production (GPDMS) decreased sharply with depth in parallel to shortwave UVR, and displayed a dose-dependent response that mixing did not significantly disrupt. To our knowledge, we provide the first measurements of GPDMS under in situ UV-inclusive optical conditions.

Quantifying cyanobacterial phycocyanin concentration in turbid productive waters: A quasi-analytical approach

In this research, we present a novel technique to monitor cyanobacterial bloom using remote sensing measurements. We have used a multi-band quasi analytical algorithm that determines phytoplankton absorption coefficients, aϕ(λ), from above surface remote sensing reflectance, Rrs(λ). In situ data including remote sensing reflectance, phytoplankton pigment concentration, and absorption coefficients of optically active constituents in the water were collected from highly turbid and productive aquaculture ponds. These shallow (<1.5m) ponds in northwestern Mississippi, USA, were used for channel catfish Ictalurus punctatus aquaculture and had high nitrogen and phosphorus loading rates from manufactured feeds added to ponds to promote rapid fish growth. These practices resulted in high phytoplankton biomass (chlorophyll-a concentrations=59.4–1376.6mgm−3) with communities dominated by filamentous, gas-vacuolate cyanobacteria. A novel technique was developed to further decompose the aϕ to obtain phycocyanin absorption coefficient, aPC, at 620nm, a primary peak of phycocyanin absorption spectrum. Validation of the model produced mean and median absolute relative errors of 36.2% and 22.0%. Overall, the model performance was higher in the higher range of PC concentration (>150μgl−1). Results demonstrate that the new approach will be suitable for quantifying phycocyanin concentration in cyanobacteria dominated turbid productive waters.

Absorption characteristics of particulates and the CDOM in autumn in Guanting Reservoir

利用2012年9月5日在官厅水库采集的水体吸收系数数据,对总悬浮颗粒物、浮游植物色素颗粒物、非色素颗粒物和有色可溶性有机物的吸收特性进行研究.结果表明:秋季官厅水库的颗粒物吸收以浮游植物色素吸收为主,总颗粒物吸收光谱与浮游藻类吸收光谱相似;非色素颗粒物和有色可溶性有机物的吸收系数随波长的增大接近指数规律衰减;a_d(440)、a_d(675)与C_Chl.a呈显著相关,表明官厅水库秋季的非色素颗粒物主要来源于浮游藻类降解产物,陆源性输入较少;a ph(440)、a ph(675)与C_Chl.a存在显著线性关系,但其比吸收系数较为恒定,与C_Chl.a基本无关;不同采样点的不同组分吸收系数对总吸收系数的贡献不同,大致有4种表现类型.在富营养程度较高的妫库区,浮游植物色素是水体光谱吸收的主导因子;在富营养程度较低的中库区,颗粒物与有色可溶性有机物共同主导水体光谱吸收.;Field work was carried out in Guanting Reservoir on September 5,2012 to study the absorption characteristics of total particulates,phytoplankton pigment,tripton and chromophoric dissolved organic matter (CDOM).The results show that: (1) In autumn,phytoplankton pigment absorption plays a major role in total particulates absorption,thus the absorption of total particulates has the similar characteristics as that of phytoplankton pigment.(2) The absorption coefficients of CDOM and tripton decreased exponentially with wavelength increasing.The slope coefficient of tripton absorption spectral Sd is much smaller than that of other eutrophic waters (eg.Lake Taihu,Lake Dianchi,Lake Chaohu).The slope coefficient of CDOM absorption spectral S_g is similar to Lake Taihu and Lake Chaohu.(3) Significant linear relationship was found between a_ph (440),a_ph (676) and C_Chl.a , but the specific absorption of phytoplankton (a_ph^*) at 440 nm and 675 nm keeps a stable level and has no obvious relationship with C_Chl.a.(4) Significant linear relationship was also found between a_d (440),a_d (676) and C_Chl.a ,which indicates tripton in autumn Guanting Reservoir mainly comes from the degra_dation of phytoplankton.(5) Absorption coefficients of different components from different sites of Guanting Reservoir show four different types of contributions to the total absorption coefficients.In more eutrophic area (Gui Area),phytoplankton dominates water's light absorption,while in less eutrophic area (Zhong Area),particles and CDOM play the same important roles in light absorption.

Remote sensing of picophytoplankton distribution in the northern South China Sea

By using a global data set (NOMAD), improved algorithms were developed for deducing from ocean color remote sensing data the concentrations of phytoplankton pigments, total chlorophyll a (TChl_a), zeaxanthin (Zea) and fucoxanthin (Fuco), and the associated primary phytoplankton groups, namely, Prochlorococcus, Synechococcus, haptophytes and diatoms, in the oceans. A modified classification for the waters of the world's ocean based on the dominant phytoplankton group was then devised. By using a local data set from the northern South China Sea (NSCS), algorithms were also developed for assessing the cell abundances of picophytoplankton, Prochlorococcus, Synechococcus and pico-eukaryotes, in this region. These algorithms were then applied to the remotely sensed data from the MODerate-resolution Imaging Spectrometer at Aqua sensor (MODIS-Aqua) to study the abundances and the distributional patterns of picophytoplankton in the entire NSCS. The results agreed well with field observations, which were available only from selected locations in the study area. On a basin scale, the results were consistent with expected variations in phytoplankton pigments, phytoplankton community composition, and picophytoplankton biomass, in response to the major known environmental phenomena in the NSCS, such as the progressive increase in biological productivity towards the coast, the runoff from the Pearl River, higher biological productivity in the wintertime, upwelling around the Taiwan Bank, winter upwelling northwest of the Luzon Island, and the transformation and dissipation of internal waves off the Dongsha Atoll. This work represents the first effort in estimating the cell abundances of the principal picophytoplankton groups in the oceans from space. The general application of this approach to the global ocean needs to be further validated and calibrated with a more extensive data base from field observations in other parts of the oceans.

Validation of MERIS Case-2 Water Products in Lake Taihu, China

Three artificial neural network (ANN) processors available as plug-in modules for the Basic ERS & ENVISAT (A)ATSR and MERIS Toolbox (BEAM) were validated in Lake Taihu, China. Mean deviations of reflectance derived from Lakes\\Boreal and Lakes\\Eutrophic were 10-90%, while reflectance from the FUB-WeW processor showed larger errors. All processors showed underestimates of chlorophyll a (Chl-a), total suspended matter (TSM), and phytoplankton pigment absorption, while particulate scattering values were severely overestimated. None of the readily available MERIS processors is currently able to separate atmospheric and water-leaving radiance over Lake Taihu, while the retrieval of phytoplankton biomass through ANN processors shows promise.

Dissolved zinc in the subarctic North Pacific and Bering Sea: Its distribution, speciation, and importance to primary producers

The eastern subarctic North Pacific, an area of high nutrients and low chlorophyll, has been studied with respect to the potential for iron to control primary production. The geochemistry of zinc, a critical micronutrient for diatoms, is less well characterized. Total zinc concentrations and zinc speciation were measured in near‐surface waters on transects across the subarctic North Pacific and across the Bering Sea. Total dissolved zinc concentrations in the near‐surface ranged from 0.10 nmol L−1 to 1.15 nmol L−1 with lowest concentrations in the eastern portions of both the North Pacific and Bering Sea. Dissolved zinc speciation was dominated by complexation to strong organic ligands whose concentration ranged from 1.1 to 3.6 nmol L−1 with conditional stability constants (K′ZnL/Zn′) ranging from 109.3 to 1011.0. The importance of zinc to primary producers was evaluated by comparison to phytoplankton pigment concentrations and by performing a shipboard incubation. Zinc concentrations were positively correlated with two pigments that are characteristic of diatoms. At one station in the North Pacific, the addition of 0.75 nmol L−1 zinc resulted in a doubling of chlorophyll after 4 days.

The proportions and variations of the light absorption coefficients of major ocean color components in the East China Sea

The East China Sea (ECS), one of the largest continental seas, has dynamic hydrology and complex optical characteristics that make ocean color remote-sensing retrieval difficult. The distributions and proportions of the light absorption coefficients of major ocean color components based on two large-scale investigations in the ECS are presented, showing these features in typical summer and winter seasons. The absorption coefficient aCDOM, aNAP and aphy of colored dissolved organic matter, non-algal particle, and pigment of phytoplankton show a decreasing trend from the coast to the outer shelf. According to the aCDOM distribution at 440 nm, the Changjiang River plume shows an abnormal southeastward transport. An extremely high aNAP value patch at 440 nm is present in the middle coast. The chlorophyll-a-specific phytoplankton pigment absorption (aphy*) is much higher in winter than in summer, which may cause serious underestimated results when applying the averaged aphy* into remote-sensing algorithms for chlorophyll concentration retrieval. The importance of phytoplankton size was evident in outer shelf waters. The absorption of aCDOM(440) is a dominant component accounting for over half of the total seawater absorption in summer. The aNAP(440) accounts for 64% of the absorption of the ECS coastal area in winter.