Turbid Water Bodies Research Articles

Study of entropy generation in transient hydromagnetic flow of couple stress fluid due to heat and mass transfer from a radiative vertical cylinder

Radiative–convective flow studies find wide range of applications in furnace design, solar fans, photochemical reactors, turbid water bodies, etc. The present article focusses on unsteady radiative–convective hydromagnetic couple stress fluid (CSF) flow from a vertical cylinder using the thermodynamic concept. The obtained governing equations of the present model are resolved by a well-organised numerical scheme. The unsteady nature of friction, entropy, coefficients of heat and mass transfer (HMT) along with the time-independent state pattern of flow-field profiles, are shown graphically for distinct values of governing radiation parameter, magnetic parameter, concentration parameter, and constant parameter to display important aspects of the solution. To analyse the HMT process in a 2D domain, Bejans flow visualisation is considered along with isotherms, streamlines, and isoconcentration lines. The Bejans HMT flow visualisation shows that the heat and mass function contours are denser in the foremost verge of the hot surface of the cylinder compared to other contours. The result indicates that the entropy generation (EG) parameter increases with decreasing values of radiation and magnetic parameters. Also, the entropy parameter increases for increasing values of concentration parameter or constant parameter.

Challenges for assessing vertebrate diversity in turbid Saharan water-bodies using environmental DNA.

The Sahara desert is the largest warm desert in the world and a poorly explored area. Small water-bodies occur across the desert and are crucial habitats for vertebrate biodiversity. Environmental DNA (eDNA) is a powerful tool for species detection and is being increasingly used to conduct biodiversity assessments. However, there are a number of difficulties with sampling eDNA from such turbid water-bodies and it is often not feasible to rely on electrical tools in remote desert environments. We trialled a manually powered filtering method in Mauritania, using pre-filtration to circumvent problems posed by turbid water in remote arid areas. From nine vertebrate species expected in the water-bodies, four were detected visually, two via metabarcoding, and one via both methods. Difficulties filtering turbid water led to severe constraints, limiting the sampling protocol to only one sampling point per study site, which alone may largely explain why many of the expected vertebrate species were not detected. The amplification of human DNA using general vertebrate primers is also likely to have contributed to the low number of taxa identified. Here we highlight a number of challenges that need to be overcome to successfully conduct metabarcoding eDNA studies for vertebrates in desert environments in Africa.

Zooplankton assemblage in four temperate shallow waterbodies in association with habitat heterogeneity and alternative states

We assessed the zooplankton assemblages in four temperate shallow waterbodies differing in macrophyte coverage and alternative states: transparent vs. turbid. The main objectives of this study were: (i) to determine the horizontal assemblage of zooplankton in structurally different habitats; (ii) to examine the role of fish, macroinvertebrates and environmental conditions in the observed zooplankton assemblage patterns; and (iii) to evaluate the zooplankton-macroinvertebrate-fish food web interactions in pelagial and littoral zone in transparent vs. turbid lakes. Abiotic factors and food resources, as well as zooplankton assemblage did not show significant difference along the gradient of habitat complexity, but exhibited pronounced variability among these waterbodies. Selected lakes contained nutrient levels that can undergo or were shifted into turbid state. Two waterbodies showed hysteresis: at similar nutrient conditions one remained transparent with macrophytes, while other shifted in its turbid state with increased phytoplankton biomass, and reduced population of planktonic crustaceans. Rotifers contributed mainly to the metazooplankton diversity and abundance. The results suggested that total phosphorous and phytoplankton were the main drivers in turbid waterbodies, and biotic interactions governed structuring of zooplankton assemblage in transparent waterbodies. Habitats of submerged and floating-leaved macrophytes do not appear to a secure refuge for zooplankton against predation. On the other hand, sediment in the vegetated and non-vegetated littoral zone functioned as an effective shelter. According to our results, zooplankton underwent strong predation pressure by macroinvertebrates and small-sized fish in the littoral and by larger-sized fish in pelagial, with alteration related to ecosystem peculiarities. Based on an applied ecological network model, zooplankters were equally vulnerable to predation in both the pelagial and littoral zones, and these biotic interactions were main factors for zooplankton homogenous horizontal distribution. These results suggest that zooplankton organisms play important role in the matter cycling and resilience of the food webs to environmental alterations.

Studying of Physico-chemical and Biological characters of Qarun Lake, El-Fayoum – Egypt

LakeQarun is an inland lake occupies the lowest part of El- Fayoum depression. Thesampling program during the studied period was carried out on monthly basisfrom May 2015 and continued till April 2016 (12 successive months).Physico-chemical analysis of Qarun Lake revealed that pH values recorded wereon the alkaline side, values of Secchi disc indicated that the water of thelake concerned as a turbid water bodies. The alkalinity in Qarun Lake ischaracterized by increasing of bicarbonate values as compared with carbonateone. Nutrients analysis indicated increasing of ammonium, nitrate, nitrite,phosphate, silicate in the water of the lake especially in front of the drains.On the other hand a total of 89 species of phytoplankton belonging to sixclasses were recorded in the lake. The recorded classes were Bacillariophyceae,Cyanophyceae, Chlorophyceae, Euglenophyceae, Dinophyceae and Cryptophyceae,.TheBacillariophyceae were most diverse with 39 species, then Cyanophyceae with 18species, Chlorophyceae and Euglenophyceae with 10 species for both, Dinophyceaewith 9 species and Cryptophyceae with 3 species. Our study concluded that theincreased nutrient level in the lake by time show an exacerbated problem ofeutrophication which lead to economic effect on fish production

Multi-Algorithm Indices and Look-Up Table for Chlorophyll-a Retrieval in Highly Turbid Water Bodies Using Multispectral Data

Many approaches have been proposed for monitoring the eutrophication of Case 2 waters using remote sensing data. Semi-analytical algorithms and spectrum matching are two major approaches for chlorophyll-a (Chla) retrieval. Semi-analytical algorithms provide indices correlated with phytoplankton characteristics, (e.g., maximum and minimum absorption peaks). Algorithms’ indices are correlated with measured Chla through the regression process. The main drawback of the semi-analytical algorithms is that the derived relation is location and data limited. Spectrum matching and the look-up table approach rely on matching the measured reflectance with a large library of simulated references corresponding to wide ranges of water properties. The spectral matching approach taking hyperspectral measured reflectance as an input, leading to difficulties in incorporating data from multispectral satellites. Consequently, multi-algorithm indices and the look-up table (MAIN-LUT) technique is proposed to combine the merits of semi-analytical algorithms and look-up table, which can be applied to multispectral data. Eight combinations of four algorithms (i.e., 2-band, 3-band, maximum chlorophyll index, and normalized difference chlorophyll index) are investigated for the MAIN-LUT technique. In situ measurements and Medium Resolution Imaging Spectrometer (MERIS) sensor data are used to validate MAIN-LUT. In general, the MAIN-LUT provide a comparable retrieval accuracy with locally tuned algorithms. The most accurate of the locally tuned algorithms varied among datasets, revealing the limitation of these algorithms to be applied universally. In contrast, the MAIN-LUT provided relatively high retrieval accuracy for Tokyo Bay (R2 = 0.692, root mean square error (RMSE) = 21.4 mg m−3), Lake Kasumigaura (R2 = 0.866, RMSE = 11.3 mg m−3), and MERIS data over Lake Kasumigaura (R2 = 0.57, RMSE = 36.5 mg m−3). The simulated reflectance library of MAIN-LUT was generated based on inherent optical properties of Tokyo Bay; however, the MAIN-LUT also provided high retrieval accuracy for Lake Kasumigaura. MAIN-LUT could capture the spatial and temporal distribution of Chla concentration for Lake Kasumigaura.

Assessment of depth and turbidity with airborne Lidar bathymetry and multiband satellite imagery in shallow water bodies of the Alaskan North Slope

Airborne Lidar bathymetry (ALB) is an effective and a rapidly advancing technology for mapping and characterizing shallow coastal water zones as well as inland fresh-water basins such as rivers and lakes. The ability of light beams to detect and traverse shallow water columns has provided valuable information about unmapped and often poorly understood coastal and inland water bodies of the world.Estimating ALB survey results at varying water clarity and depth conditions is essential for realizing project expectations and preparing budgets accordingly. In remote locations of the world where in situ water clarity measurements are not feasible or possible, using multiband satellite imagery can be an effective tool for estimating and addressing such considerations.For this purpose, we studied and classified reflected electromagnetic energy from selected water bodies acquired by RapidEye sensor and then correlated findings with ALB survey results. This study was focused not on accurately measuring depth from optical bathymetry but rather on using multiband satellite imagery to quickly predict ALB survey results and identify potentially turbid water bodies with limited depth penetration. For this study, we constructed an in-house algorithm to confirm ALB survey findings using bathymetric waveform information.The study findings are expected to contribute to the ongoing understanding of forecasting ALB survey expectations in unknown and varying water conditions, especially in remote and inaccessible parts of the world.

Stage Monitoring in Turbid Reservoirs with an Inclined Terrestrial Near-Infrared Lidar

To monitor the stage in turbid reservoirs with a sloping bank, it has been proposed to install a near-infrared Lidar on the bank and to orient it so that it points at the water surface with a large incidence angle (between ≈ 30° and 70°). The technique assumes that the Lidar can detect suspended particles that are slightly below the water surface. Some laboratory results and the first long-term assessment (>2 years) of the technique are presented. It found that: (1) although the test Lidar provides erratic distance data, they can be easily filtered according to the intensity of the received signal; (2) the Lidar provides reliable data only when the water is very turbid (Secchi depth smaller than ≈ 1.0 m); and (3) the reliable data can be used to estimate daily stage values (after a simple field calibration) with an uncertainty better than ±0.08 m (p = 0.95). Although the present form of the technique is not very accurate, it uses an inexpensive instrument (≈1500 USD) which can be easily installed in a safe place (such as is the roof of a building). It is argued that the technique could be also used to monitor the stage and the sub-surface velocity in others turbid water bodies, such as some coastal areas (a recent field of application) and flooding rivers.

An integrated model coupling open-channel flow, turbidity current and flow exchanges between main river and tributaries in Xiaolangdi Reservoir, China

The ever growing importance of sustainable management of reservoir sedimentation has promoted the development and applications of turbidity current models. However, there are few effective and practical models in literature for turbidity currents in a reservoir where the impounded area involves both the main river and its many tributaries. An integrated numerical model coupling open-channel flow, turbidity current and flow exchanges between main river and tributaries is proposed, which can simulate the complex flow and sediment transport in a reservoir where these three physical processes coexist. The model consists of two sets of governing equations for the open-channel flow and turbidity current, which are based on the modified St. Venant equations by taking into account the effect of lateral flow exchanges. These two sets of equations are solved in the finite volume method framework and the solutions are executed in an alternating calculation mode. Different methods are respectively proposed to calculate the discharge of flow exchange caused by free surface gradient and turbidity current intrusion. For the surface-gradient driven flow exchange, a storage cell method, which re-defines the relationship between water level and representative cross-sectional area, is used to update the water level at confluence. For the turbidity current intrusion, a discharge formula is proposed based on the analysis of the energy and momentum transformation in the intruding turbid water body. This formula differs from previous ones in that the effect of tributary bed slope is considered. Two events of water-sediment regulation conducted in the Xiaolangdi Reservoir in 2004 and 2006 were simulated to test the ability of this model. The predicted reservoir drawdown process, the turbidity current evolution and the sediment venting efficiency were in close agreement with the measurements. The necessity to couple the flow exchanges was demonstrated by comparing the performance of the proposed model with different intrusion discharge formulas and the common one-dimensional model neglecting the main river and tributary interaction.

Assessment of a simple hydroacoustic system for the mapping of macrophytes in extremely shallow and turbid lagoon

In this study, we focused on relatively inexpensive and commonly used fishermen class sonar in order to test its ability to detect stands of charophytes and other groups of submerged angiosperms in the shallow and turbid waters of the Curonian Lagoon. Based on the length of macrophytes, height thresholds (20 and 30cm) were established in order to distinguish charophytes from submerged angiosperms in obtained echograms. The echograms were visually analysed by two experts. We successfully discriminated 3 echofeatures (bare bottom, stands of charophytes and submerged angiosperms), whereas angiosperms from different morphology groups could not be distinguished. Below 1m depth, the stands of charophytes and submerged angiosperms were clearly distinguished, thus their maximum colonization depth could be delineated. The accuracy of the discrimination could be reduced by free-drifting mats of filamentous algae, resulting in the overestimation of charophytes. Our approach can be useful for the mapping of monospecific stands of submerged vegetation and could be an important additional tool for macrophyte monitoring and water quality assessment in shallow and turbid waterbodies.

Semi-analytical prediction of Secchi depth using remote-sensing reflectance for lakes with a wide range of turbidity

It is crucial to monitor light environments in large lakes using satellite remote-sensing data. Many studies have proposed prediction schemes of transparency information, but most of them were site-specific. Here, we applied semi-analytical retrieval procedures of inherent optical properties from in situ-measured remote-sensing reflectance and then predicted the Secchi depth (SD) using contrast transmittance theory. Two types of water regions (clear or turbid waterbodies) were first classified based on spectral characteristics, and a selection from two retrieval procedures for clear and turbid water bodies was made. The relationship between the SD and the sum of attenuation coefficients (beam and diffuse attenuation coefficients), which arises in contrast transmittance theory, was determined by analyzing the data from the previous research. The predicted SD values were compared with the observed values in 10 Japanese lakes with a wide variety of turbidity (SD 0.4–17 m). Fairly good agreement between the predicted and observed SD values was obtained, indicating the usefulness of this prediction scheme. We then made an accuracy comparison with the results obtained by previous studies, and we discuss the coefficients and the discrepancies between the measured and predicted SD values in addition to the future directions of this approach.

Influence of Particle Composition on Remote Sensing Reflectance and MERIS Maximum Chlorophyll Index Algorithm: Examples From Taihu Lake and Chaohu Lake

Using data collected from two eutrophic lakes located in eastern China (Taihu Lake, 2330 km2 and Chaohu Lake, 760 km2), the influence of variable particle composition on remote sensing reflectance (Rrs, in sr-1) properties and on the Medium Resolution Imaging Spectrometer (MERIS) maximum chlorophyll index (MCI) algorithm for estimating near-surface chlorophyll-a concentrations (Chla, in $\mu\text{g}\cdot\text{L}^{-1} $ ) is demonstrated. Although separated by a distance of only ∼200 km, the two lakes showed dramatic differences in particle composition, with Taihu Lake dominated by inorganic particles and Chaohu Lake dominated by organic particles. Such differences led to variable Rrs spectral slopes in the red and near-IR bands and perturbations to the MCI algorithm. A modified MCI algorithm (MCIT) was then developed to reduce the impact of turbidity caused by inorganic particles. Root-mean-square errors in Chla retrievals decreased from 129.5% to 43.5% when using this new approach compared with the MCI algorithm in Taihu Lake for Chla ranging between ∼5 and 100 $\mu\text{g}\cdot\text{L}^{-1} $ . Application of this approach to other turbid water bodies, on the other hand, requires validation and possibly further tuning.

Long-term remote monitoring of total suspended matter concentration in Lake Taihu using 250 m MODIS-Aqua data

We have developed and validated a robust empirical model for estimating the concentrations of total suspended matter (TSM) in Lake Taihu (China), a large turbid inland water body. This model was generated using Moderate Resolution Imaging Spectroradiometer (MODIS-Aqua) medium-resolution (250m) data gathered from 2003 to 2013 and in situ data collected from a number of cruise surveys. A strong significant correlate relationship between the in situ TSM data and the atmospherically corrected MODIS-Aqua remote sensing reflectance at the 645nm band (Rrs(645)) was found (R2=0.70, p<0.001, n=150). From these data, a local TSM model was developed for Lake Taihu. Long-term TSM distribution maps retrieved from the MODIS-Aqua data demonstrated marked temporal and spatial variations. Temporally, significant lower TSM was found in summer and autumn than in winter and spring (p<0.005, t-test). The significant seasonal variability could be attributed to sediment resuspension due to changes in the wind speed between different seasons. Lake Taihu also experiences large inter-annual variations that are primarily caused by changes in wind force over the region. In particular, the TSM in Lake Taihu from 2006 to 2008 was relatively lower than in other years, which could be explained by the lower mean wind speed during these years compared to the other years. Spatially, the TSM in the Open area, especially in the southern part of this region, was consistently higher than in other sub-regions of Lake Taihu. The coverage of submerged aquatic vegetation (SAV) generally characterized East Lake Taihu as a region with a relatively lower TSM. Lake topographic conditions, SAV, and runoff discharge jointly contributed to the spatial variations in TSM.

New strategy to improve estimation of diffuse attenuation coefficient for highly turbid inland waters

The diffuse attenuation coefficient, Kd(λ), is an important water optical property. Detection of Kd(λ) by means of remote sensing can provide significant assistance in understanding water environment conditions and many biogeochemical processes. Even when existing algorithms exhibit good performance in clear open ocean and turbid coastal waters, accurate quantification of highly turbid inland water bodies can still be a challenge due to their bio-optical complexity. In this study, we examined the performance of two typical pre-existing Kd(490) models in inland water bodies from Lake Taihu, Lake Chaohu, and the Three Gorges Reservoir in China. On the basis of water optical classification, new Kd(490) models were developed for these waters by means of the support vector machine approach. The obtained results showed that the two pre-existing Kd(490) models presented relatively large errors by comparison with the new models, with mean absolute percentage error (MAPE) values above ~30%. More importantly, among the new models, type-specific models generally outperformed the aggregated model. For water classified as Type 1 + Type 2, the type-specific model produced validation errors with MAPE = 16.8% and RMSE = 0.98 m−1. For water classified as Type 3, the MAPE and RMSE of the type-specific model were found to be 18.8% and 1.85 m−1, respectively. The findings in this study demonstrate that water classification (prior to algorithm development) is needed for the development of excellent Kd(490) retrieval algorithms, and the type-specific models thus developed are an important supplement to existing Kd(490) retrieval models for highly turbid inland waters.

Spectral Geometric Triangle Properties of Chlorophyll-A Inversion in Taihu Lake Based on TM Data

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.

Environmental factors determining invasibility of urban waters for exotic macroinvertebrates

AbstractAim Urbanization usually leads to biotic homogenization with a decrease in native species and increase in exotic species. We investigated whether local environmental factors in urban water bodies, such as water quality, habitat structure and biotic interactions, influenced the invasion of these systems by exotic macroinvertebrate species.Location Urban surface water systems in lowlands of the Rhine‐Meuse delta.Methods Presence and abundance of native and exotic macroinvertebrate species were compared between different urban water types and related to environmental variables with multivariate analysis and spearman’s correlations. Moreover, co‐existence of related native and exotic species was studied.Results In total nine exotic species were found in the following taxa: Tricladida (1), Crustacea (5), Bivalvia (1) and Gastropoda (2). Taxonomically related native and exotic crustacean species did not seem to be influenced by competition in nutrient‐rich urban waters; most species showed high abundances. Nevertheless, two exotic crustacean species were much more abundant in waters where other crustacean species were absent, possibly filling empty niches. Native species richness and abundance was positively related to environmental heterogeneity in the form of submerged vegetation. The occurrence and abundance of most exotic species were positively related to several eutrophication indicators, such as nitrate, sludge layer and lemnid vegetation.Main conclusions Exotic species in urban waters were mostly detritivorous or omnivorous and therefore dependent on leaf breakdown. In nutrient‐rich water systems, where food availability was high, exotic crustacean species co‐existed with native crustacean species, while in nutrient‐poor, richly vegetated systems, native Asellidae dominated exotic Asellidae. In the turbid water bodies with very little vegetation, native species richness was low and two exotic crustacean species were relatively abundant in these water systems. Invasibility of urban water systems could be reduced by stimulating the development of submerged and nymphaeid vegetation and decreasing nutrient levels.

水气界面参数和二向性影响因素交互作用研究

水气界面参数和二向性影响因素交互作用研究

Improvements in mapping water bodies using ASTER data

Coalbed Natural Gas extraction usually results in the production of excess, or product, water, necessitating a strategy for disposal and minimizing landscape and habitat impacts. In the Powder River Basin in Wyoming, product water is either discharged into ephemeral streams or retention/detention ponds. Monitoring these water bodies is important for environmental, habitat, and human health perspectives. This study assessed the benefits of using higher spatial resolution ASTER image, in contrast to more commonly used moderate-resolution Landsat imagery, for detecting smaller water bodies in the Powder River Basin. ASTER and Landsat Thematic Mapper (TM) images were acquired concomitantly and classified following similar methods to identify water bodies for three color classes and a range of sizes. Results showed that the ASTER image had significantly higher accuracies for detecting clear and green colored water bodies, but did not demonstrate significant improvement for detecting turbid water bodies. ASTER also showed significant improvements in detecting small-scale water bodies. However this improved performance was somewhat offset due to the misclassification of other landscape elements as water in the ASTER image. Overall when compared to Landsat TM image, ASTER image more accurately detected more water bodies, especially those with a relatively small surface area, with the two images producing similar results at large scales. The application of ASTER is therefore appropriate for monitoring and evaluation of water bodies in the Powder River Basin and elsewhere.

Interactions between a cyanobacterial bloom (Microcystis) and the submerged aquatic plant Ceratophyllum oryzetorum Kom.

In aquatic ecosystems, macrophytes and phytoplankton are main primary producers, in which macrophyte plays an important role in maintaining clear water state, while phytoplankton often dominates in turbid waterbodies. In the present study, the growth and photosynthetic activity of the submerged aquatic plant Ceratophyllum oryzetorum Kom. in different cell densities of cyanobacterial bloom are studied. The results show that the plant length and fresh mass of C. oryzetorum are promoted by low cyanobacterial cell densities. Medium and high cyanobacterial cell densities, on the contrary, act as inhibitory. Furthermore, the photosynthetic activity of C. oryzetorum is strongly inhibited by high cyanobacterial cell densities. To a certain extent, the growth of cyanobacteria is inhibited by C. oryzetorum, but no significant effect is found in this study.

Inversion of total suspended matter concentration in turbid water based on the characteristic of chlorophyll fluorescence peak

The optical property of inland water is very complex, and inversion of water components concentration of inland water body is hotspot and difficulty problem in water quality remote sensing. The remote sensing reflectance and water qualities of 67 stations were acquired in the Lake Taihu in October, 2004. Basing on the characteristic spectral analysis, it was obvious that the water body spectral character in Lake Taihu in autumn was dominated by the total suspended matter (TSM). The properties of the chlorophyll fluorescence peak mainly reflect the variation of the concentration of TSM. Hereby, we established the relation between the properties of the chlorophyll fluorescence peak and the concentration of TSM based on in-situ remote sensing reflectance with 1nm bandwith and water quality measurements. There were good response relationships between them. Making a concrete analysis ofthe correlation relationship between the absolute height of fluoresce peak, the height above the reference baseline, the normalized height referred to the maximum reflectance about 560nm in green band and 810nm in infrared band, the integral area (including the total integral area, the integral area between the spectral curve and the reference baseline, the integral area below the reference baseline and the wavelength axis) and the concentration of TSM. Their correlation coefficients were 0.8822, 0.7483, 0.8901, 0.8547, 0.8927, 0.8877 and 0.8632 respectively, and the average relative error were 27.25%, 41.03%, 27.11%, 25.75%, 24.91%, 25.47% and 27.54% respectively. The inversion accuracy of the total integral area method is obvious better than the reference baseline height method. No outstanding correlation relationship between chlorophyll concentration and fluorescence peak position were found based on reflectance spectra. The results show that chlorophyll fluorescence properties are effective in detecting TSM concentration in turbid inland water body, which provide a new optional sensitive band to retrieval TSM concentration in complex waters.

Turbidity mitigates lead toxicity to cladocerans (Cladocera)

To test the hypothesis that sediment would have a synergistic effect on the toxicity of lead to cladocerans, we performed life table demography experiments with two pelagic (Diaphanosoma birgei and Moina micrura) and one littoral (Alona rectangula) cladoceran species. Life table demography experiments were conducted at three levels of turbidity (0, 17 and 170 NTU) and six concentrations of lead (as PbCl2) from 0 to 0.71 mg l(-1). Median lethal concentrations (LC50) forA. rectangula, D. birgei and M. micrura were 7.06 +/- 0.39, 3.16 +/- 0.25 and 3.24 +/- 0.69 mg l(-1) of Pb. Life table study showed that in general, the presence of sediments in test jars allowed an overall increase of 20-75% in both survivorship and reproduction of the cladoceran species exposed to different concentrations of Pb. At 0.04 mg l(-1) of Pb, the population growth rates were 0.127 forA. rectangula, 0.037 for D. birgei and 0.471 d(-1) for M. micrura in the absence of sediments but were elevated in their presence (0.309, 0.141 and 0.722 d(-1), respectively). The data have been discussed in relation to their importance in shallow, turbid Mexican waterbodies.