Variability Of Chlorophyll Research Articles

Effects of Calcium Chloride Treatment on the Photosynthetic Capacity and Intensity of Banana Fruit during Ripening

The general objective of this work was to highlight the physiological phenomenon of photosynthesis that underlies ripening in banana fruits and to follow its bioindicators evolution. To achieve this goal, pigment content, protein content and the amount of oxygen released were determined at different stages of ripening of bananas fruits. The determination of pigment content was carried out by spectrophotometric assay after extraction in pure acetone. Protein content was determined using a known albumin concentration calibration curve. Moreover, photosynthetic intensity was evaluated by measuring the oxygen released by the banana peels by means of an oximeter. Results showed that there was a gradual decrease in pigment levels, while at the same time there were increases in carotenoid and protein levels. Photosynthetic intensity and capacity also decreased significantly. The treatment of bananas with calcium chloride helped to slow the fall of photosynthetic activity. Also, calcium chloride treatment induced a reduction of the decrease in chlorophyll content, photosynthetic intensity and increase in proteins content. Positive correlations were found between photosynthetic intensity and levels of chlorophyll a and total chlorophylls. The intensity of photosynthesis was negatively correlated with carotenoid and protein levels. The change in photosynthetic intensity during ripening was proportional to the variation in chlorophyll a and total chlorophylls content, but inversely proportional to variations in total carotenoids and proteins contents.

A comparison of chlorophyll a values obtained from an autonomous underwater vehicle to satellite-based measures for Lake Michigan

Accurate methods to track changes in lake productivity through time and space are critical to fisheries management. Chlorophyll a is the most widely studied proxy for ecosystem primary production and has been the topic of many studies. The main sources of chlorophyll a measurements are ship-based measures or multi-spectral satellite data. Autonomous underwater vehicles can survey large spatial extents approaching the scale of satellite data, but with the accuracy of ship-based water sampling methods. We use several statistical measures to compare measures of chlorophyll a collected in Lake Michigan with spatiotemporally matched satellite-derived measures of chlorophyll a from the MODIS Aqua multi-spectral sensor using NASA's OC3 and the Great Lakes Fit algorithms. Our findings show a near one to one relationship between AUV data and both satellite-derived data sets when the AUV data are coarsened to the resolution of the satellite data. A comparison of satellite-based chlorophyll a to AUV-derived chlorophyll summarized in discrete water depth bins suggested that, based on decreasing coefficients of determination, satellite estimates of chlorophyll accounted for the most variability in chlorophyll a concentrations in the upper 10 m of the water column, even though satellite sensors may detect past this depth.

Environment and anthropogenic activities influence cetacean habitat use in southeastern Brazil

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 616:197-210 (2019) - DOI: https://doi.org/10.3354/meps12937 Environment and anthropogenic activities influence cetacean habitat use in southeastern Brazil Rodrigo H. Tardin1,2,3,*, Yongwan Chun4, Clinton N. Jenkins5, Israel S. Maciel2, Sheila M. Simão2, Maria Alice S. Alves3 1Graduate Program in Ecology and Evolution, Department of Ecology, Universidade do Estado do Rio de Janeiro, Rio de Janeiro 20550-013, Brazil 2Laboratory of Cetacean Bioacoustics and Ecology, Department of Environmental Studies, Universidade Federal Rural do Rio de Janeiro, Rio de Janeiro 23897-000, Brazil 3Department of Ecology, Universidade do Estado do Rio de Janeiro, Rio de Janeiro 20550-013, Brazil 4School of Economic, Political and Policy Sciences, The University of Texas at Dallas, Richardson, TX 75080, USA 5IPÊ - Instituto de Pesquisas Ecológicas, Nazaré Paulista, São Paulo 12.960-000, Brazil *Corresponding author: rhtardin@gmail.com ABSTRACT: Investigating the influence of coastal development on marine environments is a priority to maintain healthy seas. Cetaceans are top predators, keystone and umbrella species and thus are good candidate models to evaluate the extent of anthropogenic impacts on coastal habitats. We employed a generalized linear model with spatial eigenvector mapping (SEV-GLM) to understand the influence of environmental and anthropogenic activities on migrant (humpback whale Megaptera novaeangliae) and non-migrant (Bryde’s whale Balaenoptera brydei and common bottlenose dolphin Tursiops truncatus) cetacean habitat use off Cabo Frio, Rio de Janeiro, Brazil. We hypothesized that both environmental and anthropogenic activities influence their habitat use. Data were collected during 118 boat trips between December 2010 and June 2014. The best SEV-GLM predicted humpback whales would increase linearly with distance to coast, with minimum sea surface temperature (SST) around 19.4-19.8°C and maximum SST around 25.5-26°C, with low variations in chlorophyll a (chl a) concentrations. The model also predicted that humpback whales would occur up to 10 km from diving areas, increasing linearly with distance to fishing grounds. The best non-migrant cetacean SEV-GLM predicted that they would occur more frequently around depths from 30-60 m, increasing with low SST and high chl a concentration. For the anthropogenic component, the model predicted that non-migrant cetaceans would occur up to 10 km from fishing grounds. Our study modeled the influence of anthropogenic activities on cetaceans, and indicates specific priority areas for cetacean conservation, contributing at a local and national scale. KEY WORDS: Species distribution modeling · Balaenopteridae · Delphinidae · Spatial eigenvectors · Modeling · Spatial prioritization · Upwelling Full text in pdf format Supplementary material PreviousNextCite this article as: Tardin RH, Chun Y, Jenkins CN, Maciel IS, Simão SM, Alves MAS (2019) Environment and anthropogenic activities influence cetacean habitat use in southeastern Brazil. Mar Ecol Prog Ser 616:197-210. https://doi.org/10.3354/meps12937 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 616. Online publication date: May 09, 2019 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2019 Inter-Research.

Spatial Variation in Water Column Structure, Nutrients, Chlorophyll and Zooplankton in an Estuarine Transect of Southampton Water

Estuary systems are complicated and closely related to humans. The understanding of estuary systems is important to scientific study and human develop. An investigation was conducted on 3rd November 2009 by RV Callista along the Itchen estuary of Southampton Water with the aim of determining spatial variability in physical water column structure, nutrients, chlorophyll and zooplankton of Southampton Water, and recognizing the links between them. The salinity and temperature values are relatively lower at surface upper estuary than that of deep lower estuary. Water stratification is observed around upper and mid estuary. The nutrient Si exhibits conservative behaviour with a linear relationship with salinity gradient, while P shows non-linear with salinity, which may indicate an addition bahaviour. Chlorophyll distributes high concentration at surface upper estuary and relatively uniform and low concentration at downriver area which is mainly due to light and nutrients factors. Water turbidity affects chlorophyll distribution by reducing light availability in the water column, while chlorophyll can in turn influence water turbidity. The abundance dominant species of the estuary are Copepoda and Appendicularia. The mid estuary has the highest zooplankton abundance, while the lower estuary has the most zooplankton groups. Zooplankton distribution is relative to food distribution, temperature, light and salinity profiles.

Effect of Under-Ice Light Intensity and Convective Mixing on Chlorophyll a Distribution in a Small Mesotrophic Lake

Data of long-term measurements of under-ice solar radiation, water temperature, and chlorophyll a are analyzed in four phytoplankton groups (green, diatoms, blue-green, and cryptophyte algae) in a small mesotrophic Vendyurskoe Lake (Karelia) in the period of spring under-ice convection. It is shown that, after thawing away of snow cover from lake surface, under-ice illumination increases, water temperature rises, the depth of convectively mixed layer (CML) increases, and microalga photosynthesis intensifies. In the daytime, chlorophyll a extremums appear in the CML, and, unlike the homogeneous characteristics (water electric conductivity, mineralization, etc.), the cells of different phytoplankton species can be used as tracers in studying convective mixing. A prognostic equation is obtained, reflecting an inverse dependence of the coefficients of variation of chlorophyll a concentration in CML on solar radiation fluxes, penetrating under ice bottom surface. A direct relationship was shown to exist between the increase in chlorophyll concentration in CML and its thickness.

A Random Forest Machine Learning Approach for the Retrieval of Leaf Chlorophyll Content in Wheat

Developing rapid and non-destructive methods for chlorophyll estimation over large spatial areas is a topic of much interest, as it would provide an indirect measure of plant photosynthetic response, be useful in monitoring soil nitrogen content, and offer the capacity to assess vegetation structural and functional dynamics. Traditional methods of direct tissue analysis or the use of handheld meters, are not able to capture chlorophyll variability at anything beyond point scales, so are not particularly useful for informing decisions on plant health and status at the field scale. Examining the spectral response of plants via remote sensing has shown much promise as a means to capture variations in vegetation properties, while offering a non-destructive and scalable approach to monitoring. However, determining the optimum combination of spectra or spectral indices to inform plant response remains an active area of investigation. Here, we explore the use of a machine learning approach to enhance the estimation of leaf chlorophyll (Chlt), defined as the sum of chlorophyll a and b, from spectral reflectance data. Using an ASD FieldSpec 4 Hi-Res spectroradiometer, 2700 individual leaf hyperspectral reflectance measurements were acquired from wheat plants grown across a gradient of soil salinity and nutrient levels in a greenhouse experiment. The extractable Chlt was determined from laboratory analysis of 270 collocated samples, each composed of three leaf discs. A random forest regression algorithm was trained against these data, with input predictors based upon (1) reflectance values from 2102 bands across the 400–2500 nm spectral range; and (2) 45 established vegetation indices. As a benchmark, a standard univariate regression analysis was performed to model the relationship between measured Chlt and the selected vegetation indices. Results show that the root mean square error (RMSE) was significantly reduced when using the machine learning approach compared to standard linear regression. When exploiting the entire spectral range of individual bands as input variables, the random forest estimated Chlt with an RMSE of 5.49 µg·cm−2 and an R2 of 0.89. Model accuracy was improved when using vegetation indices as input variables, producing an RMSE ranging from 3.62 to 3.91 µg·cm−2, depending on the particular combination of indices selected. In further analysis, input predictors were ranked according to their importance level, and a step-wise reduction in the number of input features (from 45 down to 7) was performed. Implementing this resulted in no significant effect on the RMSE, and showed that much the same prediction accuracy could be obtained by a smaller subset of indices. Importantly, the random forest regression approach identified many important variables that were not good predictors according to their linear regression statistics. Overall, the research illustrates the promise in using established vegetation indices as input variables in a machine learning approach for the enhanced estimation of Chlt from hyperspectral data.

Hydrodynamic Modeling Coupled with Long-term Field Data Provide Evidence for Suppression of Phytoplankton by Invasive Clams and Freshwater Exports in the San Francisco Estuary

The San Francisco Estuary (California, USA) had abundant pelagic fish in the late 1960s, but has few pelagic fish today. A primary cause for this decline in fish is thought to be a trophic cascade, triggered by declining phytoplankton. Here, we describe the changes in pelagic community structure of the San Francisco Estuary. Then, we examine whether changes in hydrodynamics due to freshwater exports, which increased exponentially beginning in 1967, in addition to the 1986 invasion by the clam Potamocorbula amurensis, explain the phytoplankton loss. Hydrodynamic variables were reconstructed back to 1956 using statistical models fit to, and cross-validated against, output from a hydrodynamic model. Then, we regressed mean summer/fall chlorophyll a—the season with the largest phytoplankton decline—against the reconstructed hydrodynamic variables and the presence/absence of P. amurensis for 1969–2014. The regression model, which explained 78% of the interannual variation in chlorophyll a, was then used to quantify the influence of P. amurensis and exports on chlorophyll a. Based on monitoring data, chlorophyll a declined 22-fold from 1969–2014, zooplankton declined 32-fold from 1972–2014, and pelagic fish declined 92-fold from 1968–2014. Averaged over 1990–2014, the chlorophyll a model ascribed an 88% decline in chlorophyll a to P. amurensis, a 74% decline to exports (at minimum), and a 97% decline to the combined influence of P. amurensis and exports (at minimum). Thus, the decline in pelagic productivity in the San Francisco Estuary has occurred largely due to the combined impacts of the P. amurensis invasion and increased freshwater exports.

Investigation of physiological changes in the affected Quercus brantii stand by oak charcoal disease

The purpose of this work was to monitor the effects of the environmental factors include temperature, precipitation and sun radiation on some physiological aspects of Q. brantii trees in the forest stand involved with the oak charcoal disease during a growing season. We designed a systematic random sampling and all trees were examined for disease status. Our result showed that 70.96% of the trees with different intensities are affected by the charcoal disease. Accordingly, values of predawn leaf water potential (PWP), midday leaf water potential (MWP) and chlorophyll variables showed significant difference in classes of oak charcoal disease. Linear regression analysis showed that the values of PWP, MWP and chlorophyll are changing at the high temperature. Mean of canker length are 20.5 cm and 51.7 cm in class 2 and 3 respectively and there is a great relation between PWP value and canker length (r<sup>2</sup> = 0.914). Canker length also has a linear relation with MWP values (r<sup>2</sup> = 0.627). Drought stress affected the physiological functions of oak trees and considerably reduced their defense potential against pathogen agents.

Tracking of NiFe2O4 nanoparticles in barley (Hordeum vulgare L.) and their impact on plant growth, biomass, pigmentation, catalase activity, and mineral uptake

Intense use of nanoparticles (NPs) in many areas has led to the release of these molecules into the environment. Plants, as sessile organisms, have contact with those particles through soil and air. However, limited information is available about their impacts and fate on plants. Therefore, this study investigates the effect of magnetic nickel ferrite (NiFe2O4) NPs, on the growth, nutrient uptake, and magnetic behavior of a crop species, barley (Hordeum vulgare L.). For this purpose, barley seedlings were grown for three weeks in hydroponic solution supplemented with (125, 250, 500, and 1000 mg/L) NiFe2O4 NPs. Results showed that synthesized NiFe2O4 NPs, sized in 12.5 ± 0.5 nm, were up-taken by the plant roots and led to an increase in nickel and iron contents of leaves, which were ˜8 and ˜5.5 times higher than that of control, respectively. In addition to that, calcium, magnesium, potassium, sodium and manganese content of the leaf were increased by the NPs treatment. Vibrating sample magnetometer (VSM) analysis showed that the magnetic signals obtained from roots and leaves were increased in proportion to the concentration of NPs, which strongly suggests the translocation of NiFe2O4 NPs. Moreover, the inclusion led to significant increase in physiological parameters, such as chlorophyll variations (˜50%), carotenoids (˜51%), and soluble protein (˜35%) (p < 0.05). However, plant biomass and growth indicators did not change up to 500 mg/L level. Higher dose treatment (1000 mg/L) significantly reduced the plant growth (˜37%; p < 0.05). Catalase activity was suppressed in leaves (p < 0.005) and induced (p < 0.01) in the root tissue. Overall, the current study showed that NiFe2O4 NPs (12.5 ± 0.5 nm in size) are up-taken by roots and translocated to the leaves without phytotoxic effect. Moreover, it enhanced the mineral uptake of some elements. These findings are suggesting the safe-use of magnetic NiFe2O4 NPs in nano-agricultural applications, i.e. nanoparticle delivery, nanoparticle-mediated plant transformation.

Medicanes Triggering Chlorophyll Increase

Studies have shown that hurricanes and typhoons, apart from being extreme weather phenomena, cause increases in marine chlorophyll-a concentrations and even phytoplankton blooms. Medicanes are the tropical-like Mediterranean cyclones that induce hazardous weather conditions as well. In this study, a couple of medicanes, over the central and eastern parts of the Sea, are examined for the first time in respect to their possible influence on chlorophyll concentrations. The affected area was delineated with the use of numerical model data, while the sea surface temperature and chlorophyll variations were assessed based on satellite-derived data. The results showed that medicanes trigger surface chlorophyll increases; after the cyclones’ passage, the concentrations were higher compared both with those before and with the climatological monthly values over a large part of the affected area. The mechanisms proposed to explain hurricanes’ favorable influence on chlorophyll concentration seem to be valid for medicanes as well. Area averaged chlorophyll concentrations presented analogous increases to the ones reported for hurricanes, though on a smaller scale. Despite the much lower intensity of medicanes compared with hurricanes, the observed increase in surface chlorophyll after their passage points to their favorable influence.

Mapping leaf chlorophyll content from Sentinel-2 and RapidEye data in spruce stands using the invertible forest reflectance model

Leaf chlorophyll plays an essential role in controlling photosynthesis, physiological activities and forest health. In this study, the performance of Sentinel-2 and RapidEye satellite data and the Invertible Forest Reflectance Model (INFORM) radiative transfer model (RTM) for retrieving and mapping of leaf chlorophyll content in the Norway spruce (Picea abies) stands of a temperate forest was evaluated. Biochemical properties of leaf samples as well as stand structural characteristics were collected in two subsequent field campaigns during July 2015 and 2016 in the Bavarian Forest National Park (BFNP), Germany, parallel with the timing of the RapidEye and Sentinel-2 images. Leaf chlorophyll was measured both destructively and nondestructively using wet chemical spectrophotometry analysis and a hand-held chlorophyll content meter. The INFORM was utilised in the forward mode to generate two lookup tables (LUTs) in the spectral band settings of RapidEye and Sentinel-2 data using information obtained from the field campaigns. Before generating the LUTs, the sensitivity of the model input parameters to the spectral data from RapidEye and Sentinel-2 were examined. The canopy reflectance of the studied plots were obtained from the satellite images and used as input for the inversion of LUTs. The coefficient of determination (R2), root mean square errors (RMSE), and the normalised root mean square errors (NRMSE), between the retrieved and measured leaf chlorophyll, were then used to examine the attained results from RapidEye and Sentinel-2 data, respectively. The use of multiple solutions and spectral subsets for the inversion process were further investigated to enhance the retrieval accuracy of foliar chlorophyll. The result of the sensitivity analysis demonstrated that the simulated canopy reflectance of Sentinel-2 is sensitive to the alternation of all INFORM input parameters, while the simulated canopy reflectance from RapidEye did not show sensitivity to leaf water content variations. In general, there was agreement between the simulated and measured reflectance spectra from RapidEye and Sentinel-2, particularly in the visible and red-edge regions. However, examining the average absolute error from the simulated and measured reflectance revealed a large discrepancy in spectral bands around the near-infrared shoulder. The relationship between retrieved and measured leaf chlorophyll content from the Sentinel-2 data had a higher coefficient of determination with a higher NRMSE (NRMSE = 0.36 μg/cm2, R2 = 0.45) compared to those obtained using the RapidEye data (NRMSE = 0.31 μg/cm2 and R2 = 0.39). Using the mean of the ten best solutions (retrieved chlorophyll) the retrieval error for both Sentinel-2 and RapidEye data decreased (NRMSE = 0.34, NRMSE = 0.26, respectively), as compared to only selecting the single best solution. When the Sentinel-2 red edge bands were used as the spectral subset, the retrieval error of leaf chlorophyll decreased indicating the importance of red edge, as well as properly located spectral bands, for leaf chlorophyll estimation. The chlorophyll maps produced by the inversion of the two LUTs effectively represented the variation of foliar chlorophyll in BFNP and confirmed our earlier findings on the observed stress pattern caused by insect infestation. Our findings emphasise the importance of multispectral satellites which benefits from red edge spectral bands such as Sentinel-2 as well as RapidEye for regional mapping of vegetation foliar properties, particularly, chlorophyll using RTMs such as INFORM.

Biogeophysical feedback of phytoplankton on Arctic climate. Part II: Arctic warming amplified by interactive chlorophyll under greenhouse warming

It has been shown that the interaction between marine phytoplankton and climate systems may intensify Arctic warming in the future via shortwave heating associated with increased spring chlorophyll bloom. However, the changes of chlorophyll variability and its impact on the Arctic future climate are uncomprehended. Lim et al. (Clim Dyn. https://doi.org/10.1007/s00382-018-4450-6 , 2018a) (Part I) suggested that two nonlinear rectifications of chlorophyll variability play cooling role in present-day climate. In this study, we suggest that the decreased interannual chlorophyll variability may amplify Arctic surface warming (+ 10% in both regions) and sea ice melting (− 13% and − 10%) in Kara-Barents Seas and East Siberian-Chukchi Seas in boreal winter, respectively. Projections of earth system models show a future decrease in chlorophyll both mean concentration and interannual variability via sea ice melting and intensified surface-water stratification in summer. We found that suggested two nonlinear processes in Part I will be reduced by about 31% and 20% in the future, respectively, because the sea ice and chlorophyll variabilities, which control the amplitudes of nonlinear rectifications, are projected to decrease in the future climate. The Arctic warming is consequently enhanced by the weakening of the cooling effects of the nonlinear rectifications. Thus, this additional biological warming will contribute to future Arctic warming. This study suggests that effects of the mean chlorophyll and its variability should be considered to the sensitivity of Arctic warming via biogeophysical feedback processes in future projections using earth system models.

Spatial variations in Chlorophyll a, C, N, and P in a Louisiana estuary from 1994 to 2016

Intense sampling of an estuary can reveal relative spatial changes that are significant irrespective of whether or not the estuary is eutrophic, micro- or meso-tidal, disturbed, or restored. This ‘waterscape’ perspective is analogous to a landscape perspective. We collected monthly water samples in the Barataria Basin watershed from 1994 to 2016 at 37 stations along a 129 km transect from 1 km offshore to a freshwater stream. The average Chlorophyll a (Chl) concentration from 267 trips was supported from both nitrogen-fixing cyanobacteria in a freshwater lake and partially from nutrients in seaward sources. Estuarine salinity was correlated with the discharge of the nearby Mississippi River. The main form of N was as organic nitrogen, not inorganic forms that recycle quickly, making changes in inorganic nitrogen concentration an unreliable indicator of net denitrification or uptake. The total nitrogen (TN) and total phosphorus (TP) concentrations declined with dilution towards the coast, but not because of denitrification. The phytoplankton standing biomass reflected the TN:TP ratio in the water column and there was a significant rise in the variability of Chl concentration at 2–6 psu, which was otherwise unremarkably constant. These waterscape patterns and cautionary interpretations may be common to other estuaries.

Spatial and temporal variation in chlorophyll a concentration in the Eastern China Seas based on a locally modified satellite dataset

Satellite chlorophyll a (Chl) is an essential parameter for large-scale studies on changes in the marine ecosystem and biogeochemistry. However, in the eastern China seas (ECSs), the coexistence and interaction of turbid and clear water pose challenges to the application of standard satellite Chl products to studies on phytoplankton dynamics. Based on the empirical modification of the OC-CCI (Ocean Colour Climate Change Initiative) standard products, we herein provide a locally modified chlorophyll a (LMC) dataset and compare the large-scale Chl distributions with satellite and in-situ Chl datasets. Compared with standard Chl, LMC has a higher correlation with in-situ data (R2 = 0.58) and lower Bias (0.08) and is more consistent with the ship-measured Chl distributions. Using the LMC dataset, we analyzed the climatological Chl distributions in the ECSs and classified the Chl annual cycles into four types. Our results suggest that high Chl patterns not only rely on nutrient supply, but also relate to light conditions controlled by vertical mixing and suspended matter. The different Chl annual cycles are mainly caused by differences in the duration and range of nutrients and light limitation, and thus their distributions tend to vary with water depth. We believe that this work presents a more accurate dataset in the ECSs and can improve the understanding of local biogeochemical cycles.

Study of the seasonality and hydrology as drivers of phytoplankton abundance and composition in a shallow estuary, Weeks Bay, Alabama (USA)

Small, shallow estuaries can be highly vulnerable to land use changes, eutrophication and habitat loss but are understudied with respect to their larger counterparts. Where they are monitored, the descriptors of their environmental status are typically chlorophyll a as a proxy for phytoplankton abundance and nutrient concentration as a presumed driver of the phytoplankton community. We present data from a shallow estuary, Weeks Bay, Alabama (USA), that demonstrates that chlorophyll a and nutrient concentrations are inadequate descriptors of ecological state. Weeks Bay had relatively high nutrient concentrations (86–169µM total nitrogen and 1.0–5.2µM total phosphorus) and highly variable chlorophyll a concentrations (2.2–160.5μgL-1). The variability in chlorophyll a was most highly correlated with nutrient levels and river discharge. There was no relationship between chlorophyll a and community composition. Two of three maxima in chlorophyll a (&gt; 100 μgL-1) were caused by non-toxic chlorophytes and diatoms; the third was dominated by potentially toxic raphidophyte Heterosigma akashiwo. The phytoplankton were diverse even at the class level and community composition varied on both annual and inter-annual scales. The best overall descriptor of phytoplankton composition was the annual cycle in temperature, but inter-annual variability was correlated with hydrology. In the winter, dominance by dinoflagellates, including several taxa that form harmful algal blooms, was correlated with low river discharge, low turbidity and high zooplankton numbers, while dominance by diatoms was correlated with high and variable river discharge and high turbidity. In the summer, dominance by cryptophytes versus diatoms was consistent with changes in groundwater discharge. The dominance of harmful algal bloom taxa vs non-toxic ones could not be inferred from chlorophyll a and/or nutrient concentrations.

Physiological and biochemical response of cowpea (Vigna unguiculata L.) landraces of Kashmir valley under water stress

The present study is based on the hypothesis that natural variation for physiological and biochemical parameters can be effectively harnessed to improve water stress resilience. Under irrigated conditions, CTD decreased progressively. However, under drought stress, it decreased sharply. Under drought relative water content (RWC) had a mean value of 65.49% with the highest and lowest value recorded for C25 and C32. The largest and smallest reduction in RWC under drought was recorded in case of C32 and C9. There was wide variation in chlorophyll a and b content. The highest and lowest values for chlorophyll stability index (CSI) were recorded for C13 and C29 respectively. The DAB assay clearly differentiated the lines on the basis of darker staining of leaves. The lines showing greater per cent reductions in yield parameters such as C1, C2, C3, C7, C12, C14, C22 and C29 showed greater staining in leaves in DAB assay.

Assessment of environmental impacts of LID technologies on vegetation

LID facilities do not consider environmental factors, and due to inappropriate vegetation planting causing degradation in efficiency due to plant damage and difficulty in maintenance. Therefore, in this study, assessment of impact environmental factor by seasonal variation of chlorophyll and growth of vegetation planted in LID technologies and change of pollutant reduction were conducted. In the case of B-SJ and B-RI, growth rate decreased after summer (August), and B-MG showed steady growth until autumn (September). Chlorophyll was found to increase during spring season while it decreased during autumn season. The chlorophyll concentration was found to affect the plant growth pattern. TN reduction efficiency was highest with greater than 80% efficiency in summer, and it was analyzed that plants were identified as the main factor affecting the seasonal reduction efficiency of TN. Also, temperature and relative humidity were analyzed to affect plant growth, activity and pollutant removal efficiency. Plant type and growth pattern are considered as factors to be considered in selection of appropriate plant types in LID technologies.

Seasonal variation in chlorophyll a fluorescence of Butea monosperma

ABSTRACT This study was conducted to observe the seasonal variation trend in leaf chlorophyll a fluorescence of Butea monosperma tree belonging to Fabaceae family. Chlorophyll fluorescence parameters taken for the present study were NPQ = (FM/FM −1) (non-photochemical quenching of chlorophyll fluorescence), Fv/Fm = Fm–Fo/Fm (maximum photochemical quantum yield of photosystem II) and qL = qp.F0ʹ/F’ (coefficient of photochemical fluorescence quenching). Chlorophyll a fluorescence of Butea monosperma was measured with the help of JUNIOR‐PAM, Chlorophyll Fluorometer, Heinz Walz GmbH, Germany in December (winter), May (summer) and August (rainy) seasons and also on day 1, day 10 and day 20 of December, May and August. The measurement revealed that the above three fluorescence parameters showed a seasonal variation trend, wherein NPQ and qL followed a similar variation trend while Fv/Fm showed a different trend. NPQ and qL values were maximum in the summer season followed by winter and rainy seasons, while Fv/Fm value was maximum in the rainy season followed by winter and summer seasons. The variations in chlorophyll a fluorescence in different seasons are due to different environmental conditions causing a different degree of stress to Butea monosperma plant in different seasons.

Spatial–temporal distribution and limiting factor variation of algal growth: three-dimensional simulation to enhance drinking water reservoir management

Although algal growth in drinking water reservoirs has attracted worldwide attention, its spatial–temporal distribution and limiting factor variation are still not well described. In this study, three-dimensional environmental fluid dynamic code of Miyun reservoir had been established and numerical simulation was conducted to reveal the detailed temporal–spatial variation and interrelationship of temperature, total nitrogen, total phosphorous, chlorophyll a at specific time points and locations in a drinking water reservoir in China. The limiting effect of light, temperature, nitrogen and phosphorus on algae growth was also quantified throughout the year. The results suggested that thermal stratification and internal sources of nutrients played an important role in the algal bloom development; the surface layer of shallow regions was identified as the originating algal habitat. The dominant controlling factors for algal growth varied throughout the year. Temperature was the main limiting factor before May 4 and after November 25, while total phosphorous became the dominant limiting factor from May 4 to November 25. Variation of chlorophyll a and phosphorous concentration was closely related during the phosphorous limiting period. This study suggests that comprehensive measures, including external nutrient reduction, internal nutrient reduction and mixing condition improvement, should be implemented to reduce algal bloom events.

How can a rare protected plant cope with the metal and metalloid soil pollution resulting from past industrial activities? Phytometabolites, antioxidant activities and root symbiosis involved in the metal tolerance of Astragalus tragacantha

Astragalus tragacantha is a protected plant species in France that grows even in the trace metal and metalloid (TMM) polluted soils of the Calanques National Park (PNCal). Soils are mainly contaminated by lead, copper, zinc and arsenic. An ex situ experiment was conducted, firstly to determine the molecular responses and root traits involved in the TMM tolerance of this plant species by growing individuals in a soil from the surroundings of one of the brownfields of the PNCal, known as l’Escalette, where this plant species grows spontaneously. Secondly, in order to determine the plasticity of these responses, seeds were collected from three different populations, at l’Escalette (polluted site), one from the Frioul archipelago (non-polluted, insular site) and one from La Seyne (non-polluted, littoral site). The results of this study confirmed the capacity of A. tragacantha to germinate and grow in TMM contaminated soils. Only moderate significant variations in chlorophyll and flavonol indices, proline content and antioxidant activities were detected between polluted and control soil conditions for all populations. The main driver for A. tragacantha TMM tolerance seemed to be its ability to be associated with root symbionts i.e. arbuscular mycorrhizal fungi and dark septate endophytes, corresponding to a nutrient-uptake strategy trait. This work provides support for the challenge of A. tragacantha conservation along the littoral of the PNCal, because increasing the number of A. tragacantha individuals would both increase vegetation cover of the polluted soils to reduce the pollution transfer and reinforce the populations of this species.