Presence Of Suspended Sediment Research Articles

Contribution of high turbidity to tidal dynamics in a curved channel in Zhoushan Islands, China

The curved tidal channel, Luotou Deep-water Navigational Channel, is the main channel of the Ningbo Zhoushan Port, which is ranked first in the world. Tidal dynamics in the channel are spatially and temporally asymmetric. In this study, the three-dimensional tidal dynamics in the channel were analyzed using field data and simulated using FVCOM. The results show that the tides in the channel flood/ebb along the northern/southern bank near the bottom/surface layer and these asymmetries are due to the imbalanced Coriolis force, centrifugal force, sea-level gradient, and density gradient. Residual current velocity peaks (0.7 m/s) in the middle of the channel as the same distribution as sediment flux. There are two high turbidity zones (>4 kg/m3) which are northern at flood than at an ebb in the channel. The drag reduction effect of fluid mud enhances the lateral circulation, which is strong near the Chuanshan Peninsula and frictional dissipation plays an important role in it. The presence of suspended sediment changes the contribution of acceleration terms through impacting density and bottom friction, and the centrifugal force term has the largest increases. This study provides the foundation for the morphology evolution and harbor management of macro-tidal turbid coastal zones. Highlights A baroclinic model was built to study the tidal dynamics in macro-tidal turbid Zhoushan Islands. Asymmetric tides and lateral circulation occur in the Luotou Deep-water Navigational Channel (DNC). Mechanism of lateral circulation depends on tidal phases and locations in the DNC. Sediment impacts water density and drag coefficient, and then changes currents and sediment fluxes in the DNC.

Uncovering Plastic Litter Spectral Signatures: A Comparative Study of Hyperspectral Band Selection Algorithms

This article provides insights into the optical signatures of plastic litter based on a published laboratory-scale reflectance data set (350–2500 nm) of dry and wet plastic debris under clear and turbid waters using different band selection techniques, including sparse variable selection, density peak clustering, and hierarchical clustering. The variable selection method identifies important wavelengths by minimizing a reconstruction error metric, while clustering approaches rely on the strengths of the correlation and local density of the spectra. Analyses of the data reveal three distinct absorption lines at 560, 740, and 980 nm that produce relatively broad reflectance peaks in the measured spectra of wet plastics around 475–490, 635–650, 810–815, and 1070 nm. The results of band selection consistently identify three important regions across 450–470, 650–690, and 1050–1100 nm that are close to the reflectance peaks of the mean of wet plastic spectra over clear and turbid waters. However, as the number of isolated important wavelengths increases, the results of the methodologies diverge. Density peak clustering identifies additional wavelengths in the short-wave infrared (SWIR) region of 1170–1180 nm) as a result of a high local density of the reflectance points. In contrast, hierarchical clustering isolates more wavelengths in the visible range of 365–400 nm due to weak correlations of nearby wavelengths. The results of the clustering methods are not consistent with the visual inspection of the signatures as peaks and valleys in the spectra, which are effectively captured by the variable selection method. It is also found that the presence of suspended sediments can (i) shift the important wavelength towards higher values in the visible part of the spectrum by less than 50 nm, (ii) attenuate the magnitude of wet plastic reflectance by up to 80% across the entire spectrum, and (iii) manifest a similar spectral signature with plastic litter from 1070 to 1100 nm.

Rechargeable stormwater biofilters: In situ regeneration of PFAS removal capacity by using a cationic polymer, polydiallyldimethylammonium chloride

Conventional stormwater biofilter media such as sand and compost have limited capacity to remove PFAS due to the exhaustion of attachment sites with pollutants and other stormwater constituents. Replacing exhausted filter media is expensive whereas in situ regeneration of their adsorption capacity can be cost-effective. This study demonstrates that in situ application of cationic polymers such as polydiallyldimethylammonium chloride (PDADMAC), a drinking water coagulant, could regenerate the filter media capacity to remove anionic PFAS. The benefit of PDADMAC increased with a decrease in PFAS carbon chain length: the removal of PFBA increased by 9.9 ± 1.8 times while the removal of PFOA only increased by 0.3 ± 0.03 times. The result indicates the application of the cationic polymer can help remove short-chain PFAS, the ones that are most difficult to remove by typical organic amendments such as activated carbon and biochar. Despite being used as coagulants, the addition of PDADMAC did not negatively affect the clogging rate of the biofilters in the presence of suspended sediments. Surprisingly, biofilters exposed to PDADMAC required 35.3% more suspended sediments than the biofilters without PDADMAC to reduce the hydraulic conductivity below half of the initial value. PDADMAC application reduced the release of colloids from the biofilter media during intermittent flow, thereby decreasing the potential of the colloid-facilitated release of adsorbed PFAS. The adsorbed PDADMAC in the biofilter was not degraded, indicating that applied PDADMAC could last long and continue to remove PFAS in the biofilter. Thus, in situ application of cationic polymers can help regenerate the PFAS removal capacity of conventional biofilters.

Bioavailability of citalopram to Daphnia magna in the presence of suspended sediments with various properties

The influence of suspended sediment (SPS) properties on the biological effects of antidepressant citalopram (CIT) was investigated in our study. For CIT exposure alone, the feeding behavior, energy available, glutathione-S-transferase (GST) activity of D. magna were vitally induced at 10 μg/L. In the presence of SPS, significant dose-dependent reduction in the ingestion and filtration rates were observed with the increase of SPS concentration, while SPS organic content (foc) of 1% exhibited the most serious aggravation. The protein was the main contributor to detoxification and cellular protection under the stress of CIT and SPS. Obvious disturbance effects on the malonaldehyde content, catalase and GST activities were observed for SPS of 0.1 g/L, 60–90 μm and foc of 2%. Overall, the important role of SPS properties on the biological effects of CIT should be taken into consideration for the accurate risk assessment of pollutants.

Influence of suspended sediment on the bioavailability of benzophenone-3: Focus on accumulation and multi-biological effects in Daphnia magna

The UV-filter benzophenone-3 (BP3) tends to associate with suspended sediment (SPS) due to hydrophobicity, which could alter its toxicological effects on non-target aquatic organisms. In this study, the freshwater cladoceran Daphnia magna (D. magna) was selected as a model organism to investigate the impacts of the source and composition of SPS on the accumulation and multiple toxicological effects (from the molecular level to individual level) of BP3. Among the three components of SPS, amorphous organic carbon (AOC) and minerals promoted the body burden of BP3, while black carbon (BC) inhibited the bioaccumulation. The inhibition effects of BP3 on swimming and feeding behaviors of D. magna were also enhanced due to the presence of AOC and BC. Compared with BP3 exposure alone, higher oxidative stress and neurotoxicity were observed in the presence of SPS containing AOC, BC and minerals, corresponding to that superoxide dismutase, catalase and glutathione-S-transferase activities were further induced, and acetylcholinesterase activity was inhibited. Furthermore, BP3 induced mRNA expression levels of the endocrine system (ecdysone receptor, cytochrome P450 CYP314) and metabolic system (toxicant nuclear receptor HR96, P-glycoprotein), and the presence of SPS containing AOC, BC and minerals exhibited an enhanced effect. Combined with all endpoints, evident relationship was observed between the bioaccumulation level and the response of individual behavior and molecular biomarkers. The results demonstrated that the effects of SPS compositions on bioaccumulation and toxicological effects of organic UV-filters should be considered in aquatic environments.

Feral horses (

Feral horses preferentially utilise aquatic landscape elements. Damage to stream banks by feral horses potentially degrades water quality and affects aquatic ecosystems. Despite the global predominance of horse activity in or near water, there is poor understanding of in-stream impacts. Motion-sensing cameras were used near subalpine streams to quantify frequency and behaviour of horses interacting with streams. Deployed turbidity loggers were used to indicate the presence of suspended sediment from interactions and to assess long-term (3 year) seasonal suspended sediment regime at sites with very small and large amounts of horse activity. In summer, 99.9% of large grazer interactions with streams were horses and we estimate 130 horse interactions per kilometre of stream per day, resulting in stream turbidity increases up to 100 NTU. Long-term turbidity at sites with greater riparian damage from horses was significantly greater than at control sites. Turbidity in horse-affected streams peaked at 50 times the national turbidity guideline and, in summer, averaged eight times the guideline. Suspended sediment leads to a high risk of loss of aquatic diversity and impairment of ecosystem function. Linear relationships between turbidity and riparian damage suggest that any level of horse presence affects subalpine waterways.

Suspended sediment exacerbates perfluorooctane sulfonate mediated toxicity through reactive oxygen species generation in freshwater clam Corbicula fluminea

Perfluorooctane sulfonate (PFOS) potentially adsorbs on the surface of suspended sediment (SPS), which can develop a toxic “pool” bioavailable to benthic organisms. In this study, the freshwater clam Corbicula fluminea was employed as a zoobenthos model to study the effects of SPS (collected from the Yellow River) on the bioaccumulation and toxicity (from the molecular level to cellular and physiological levels) caused by PFOS exposure. Besides, the enhanced integrated biomarker response (EIBR) system was applied as an index to evaluate the in-depth toxic effects of PFOS and SPS single and co-exposure at various treatment levels. Our results demonstrated that PFOS-SPS co-exposure (at sub-lethal doses of PFOS) significantly increased the bioaccumulation of PFOS, and induced the elevated levels of reactive oxygen species (ROS), the significantly increased activities of superoxide dismutase (SOD) and catalase (CAT) enzymes, the significantly increased content of malondialdehyde (MDA), and the significantly upregulated expression levels of sod, selenium-dependent glutathione peroxidase (se-gpx), heat shock protein 22 (hsp22), heat shock protein 40 (hsp40) and cytochrome P450 30 (cyp30) genes. Further, the co-exposure induced the significantly higher histopathological alterations in the gonads and digestive glands, and even elevated the inhibition of siphoning behavior in clams. In addition, the EIBR index also revealed the highest values for PFOS and SPS co-exposure, compared to the individual SPS or PFOS exposure. The results indicated that at high levels of PFOS exposure (especially at 1000 μg/L), the presence of SPS might increase the generation of ROS by influencing the bioaccumulation of PFOS, which enhanced the toxicity of PFOS to C. fluminea. These results potentially provide basic information for the comprehensive evaluation of the toxic effects of PFOS on benthos in a multi-sediment river ecosystem.

Movement of the Suspended Flow in the Open Irrigation Channels

Abstract The article deals with the issues of turbulent movement of a suspended flow in open channels. Differential equations of a suspended flow were used with considering the interaction of the fluid and solid particles. The solution of equations for steady flow was obtained by a numerical method. Field data measured in irrigation channels in Tashkent and Parkent were used to estimate the velocity distribution over the depth of the stream. Developed method for calculating the formation of velocity field in statically and dynamically stable channels considered the turbulent characteristics and the presence of suspended sediments in the stream. The possibilities of practical application of the above-mentioned differential equations to the solution of the problem of a suspended solids flow's forming a velocity field were discussed. The developed analytical formulas make it possible to determine the value of flow parameters. The result is a new generalization of the mathematical model of the velocity field formation regularity at different flow saturations with a suspension. On its basis, the method is developed for calculating the parameters of the weighing process and transport of suspended particles in open channels.

Influence of suspended sediment characteristics on the bioaccumulation and biological effects of citalopram in Daphnia magna

The influence of suspended sediment (SPS) characteristics on the bioavailability of the antidepressant citalopram (CIT) was investigated in the cladoceran Daphnia magna. The bioaccumulation, swimming behaviours, psychological indices, and oxidative stress were examined. The CIT bioaccumulation were altered in the presence of SPS, such that the body burden of CIT decreased as the concentration of SPS increased and as the organic carbon content of SPS (foc) increased; moreover, the body burden of CIT increased as SPS particle size increased. All the biomarker activities of D. magna were markedly induced at a CIT exposure concentration of 10 μg/L. However, the biological effects of CIT did not depend on the body burden of CIT as SPS concentration increased, while the swimming activities and oxidative stress were significantly enhanced by SPS concentration at 1 g/L. The influences of SPS particle size and foc on the activities of swimming and physiological indicators were mainly associated with the CIT bioaccumulation, while foc in SPS was more substantial than particle size. In addition, the antioxidant activities decreased as foc increased and were significantly strengthened at particle sizes of 30–60 μm. The impacts of different SPS characteristics on the adsorption and desorption capacity of CIT and the ingestion habits of D. magna were the main reasons for the variations in CIT body burden and biological effects. According to the results obtained in this study, the SPS characteristics should be considered in the risk assessment of contaminants in natural aquatic environments.

Optical Detection of Diatom Bloom in the Coastal Waters of Bay of Bengal Using Oceansat-2 OCM

Phytoplankton blooms are the indicators of marine ecosystem health status and their monitoring is a key component in the effective management of coastal and oceanic resources. It remained as a challenge in the coastal waters due to the presence of suspended sediments and dissolved organic matter which interferes with the phytoplankton signal. Several methods and techniques were developed to detect, map and monitor the phytoplankton blooms in the coastal waters using in situ and satellite data. To address this issue ISRO took an initiative to monitor and identify the phytoplankton blooms in the North Indian Ocean to be specific in the coastal waters. As part of this program, the blooms are monitored using Oceansat-2 Ocean Colour Monitor (OCM-2) data all along the East coast of India. This paper presents a case study in the bloom dominated coastal waters along Off Godavari delta covering Kakinada and Yanam in the East coast of India. In-situ measurements collected onboard during a bloom event are optical parameters like Remote Sensing reflectance, Rrs(λ), Water leaving radiance Lw(λ) from the Hyperpro-II under water radiometer, absorption due to phytoplankton, aph(λ), from the spectrophotometer, biological parameters of phytoplankton cell counts and HPLC pigments. From the in situ biological measurements, it is confirmed that the bloom was dominated by with diatom species of Skeletonema costatum with a high concentration of Fucoxanthin as the biomarker for diatoms from the HPLC pigment analysis. Based on these results obtained, optical detection of the bloom species using spectral discrimination of Rrs for different cell enumerations was considered and further spectral derivative analysis (first to fifth order) has been carried out to identify the peaks to detect the bloom forming species. The criteria considered as the minima in the second order derivative (dλ2Rrs) for identifying the peak to discriminate the spectra of the bloom forming species. From the analysis, a unique peak at 483 nm which is identified in particular to S. costatum species in the coastal waters which are identified from the chlorophyll product derived from OCM-2. From the results observed, it can ensure that diatom blooms can be detected from OCM-2 using 490 nm spectral band.

A three-phase flow simulation of local scour caused by a submerged wall jet with a water-air interface

Interactions between fluid and hydraulic structures and the resulting bed scouring are complex phenomena that involve three phases: water, air and sediment. This study presents a new rheology-based three-phase flow model that can (i) track the water-air interface in the presence of suspended sediment and (ii) predict the local scour caused by submerged wall jet. A modified volume-of-fluid (VOF) method was used to track the water-air interface, and a modified k-ϵ turbulence model was employed to capture important features of the turbulent flow, including turbulence modulation due to fluid-sediment interaction. The three-phase model was first used to study the sediment transport in open-channel flows in order to evaluate the performance of two models for particle response time, and then employed to simulate the scouring process downstream a submerged wall jet issued from a sluice gate. The simulated bed profiles showed good agreement with the measured. It was demonstrated that the three-phase model could capture important dynamic features such as sediment avalanche.

Biological effects of citalopram in a suspended sediment-water system on Daphnia magna.

Suspended sediment (SPS) plays an important role in the aquatic ecosystems. Selective serotonin uptake inhibitors (SSRIs) are commonly used antidepressants and are frequently detected in aquatic environments. However, the biological effects of SSRIs in the presence of SPS are not well understood. To fill this gap, an SPS-water system was constructed to investigate the effects of citalopram (CIT) on Daphnia magna in the presence of SPS with different concentrations (0.1, 0.5, 1gl-1) and organic carbon contents (0.5, 1, 1.5, 2%). A dialysis bag was applied in the exposure system to control the same dissolved concentration of CIT and prevent SPS from entering into the bag. The dissolved CIT concentration obviously decreased in the SPS-water system during the exposure period. The presence of SPS significantly increased the immobilization of D. magna, and the immobilization rates were positively correlated with the SPS concentration and negatively correlated with the organic carbon content in SPS. For a single exposure, CIT significantly increased superoxide dismutase (SOD) activity and inhibited acetylcholinesterase (AChE) activity in D. magna, while SPS itself did not change the SOD and AChE activities. In the SPS-water system, SOD activity was significantly suppressed, indicating that the SPS-CIT combination could result in oxidative damage. However, SPS did not enhance the neurotoxicity of D. magna that was induced by CIT. These results suggest that SPS exerts a vital role on the biological effects of CIT and the contaminants sorbed on SPS should be taken into consideration.

Fine sediment as environmental stressor affecting freshwater mussel behavior and ecosystem services

Fine sediment pollution is considered a major stressor for aquatic ecosystems and their biodiversity. In particular, fine sediments have been suggested to play a crucial role in the declines of freshwater mussels which are considered keystone fauna of streams and rivers. Whereas the effects of deposited fine sediments on recruitment failure are well known, effects of suspended fine sediments on adult mussel behavior are less studied. Therefore the aim of this study was to investigate the effects of fine sediment exposure on freshwater mussel behavior and on mussel-dependent ecosystem services. Unio pictorum mussels were used to test three behavioral endpoints: Hall activity, transition frequency and relative water clearance rate. Mussels were exposed to fine sediments of different particle size classes (<45μm, 45–63μm, 63–125μm) and different concentration (0–10gL−1) of the smallest particle size class. Hall sensor technology and turbidity measurements were used to detect mussel behavior in presence of suspended sediments. Results revealed that mussels improve clearance of suspended particles out of the water column by 35%, independent of particle size class and concentration. Transition frequency was determined an unsuitable behavioral endpoint for non-soluble substances. Contrary to previous studies, we could demonstrate that fine sediments do not interfere with filtration by mussels and that mussels have a great influence on water purification, providing a valuable ecosystem service.

Off-shelf fluxes across the southern Adriatic margin: Factors controlling dense-water-driven transport phenomena

The northern Adriatic Sea is a basin where dense shelf waters form during winters if the following favorable conditions are attained: high salinities, mainly related to low river water discharge (Po river in primis) during fall season, and strong heat fluxes induced by cold and dry Bora wind events blowing from north-east. Extremely favorable conditions to Northern Adriatic Dense Waters (NAdDW) formation characterized winter 2012 when, following several months of low Po river runoff, a strong event of Cold Air Outbreak (CAO) occurred from the end of January until mid-February. Consequently, the mean temperature of northern Adriatic waters dropped to about 6°C and exceptional densities (potential density anomaly locally exceeding 30.0kgm−3) were reached.The production and spreading mechanisms of dense water in the Adriatic Sea have been modeled by means of the COAWST (Coupled-Ocean–Atmosphere-Wave-Sediment-Transport) modeling system. The model builds upon a high-resolution (1km spaced horizontal grid), fully 3-D primitive equations hydrodynamic model coupled with a phase-averaged wave model and sediment routines, and is driven by simulated atmospheric forcings.The dataset used to assess model outputs relies on the measurements acquired during the dedicated field campaigns “Operation Dense Water”, a set of two rapid response cruises carried out in southern Adriatic during winter 2012, and by five mooring arrays deployed in the Southern Adriatic Margin (SAM) that allowed the continuous acquisition of temperature, salinity, currents and suspended matter samples.Results from the integrated data-model approach suggest that the NAdDW propagates along the shelf to the southern basin following both a shallower vein and a deeper stream, with a process characterized by a strong variability (mean value of 0.31Sv with peaks rapidly growing in the first weeks after the CAO up to 2.19Sv). Additionally, COAWST capability to couple different numerical models allowed to disentangle the relative importance of aspects on dense water generation, mixing and spreading, demonstrating how coupled runs can lead to volumes up to 50% larger with respect to uncoupled simulations. Additional light is shed on the transport pathways off the shelf and on possible sediment transport phenomena in the area, in this benefiting from an unprecedented spatial resolution and a new bathymetry reflecting very high resolution data acquired via multi-beam techniques. Although dense water propagation appears as a relatively large-scale process involving the whole western side of the SAM, topographic local discontinuities and seabed slopes appear crucial in triggering descent and governing flow patterns. The presence of suspended sediment along the water column, despite not significantly influencing the overall fluxes across sections, is responsible of pulling part of the veins towards deeper zones.

The Between-Population Genetic Architecture of Growth, Maturation, and Plasticity in Atlantic Salmon

The between-population genetic architecture for growth and maturation has not been examined in detail for many animal species despite its central importance in understanding hybrid fitness. We studied the genetic architecture of population divergence in: (i) maturation probabilities at the same age; (ii) size at age and growth, while accounting for maturity status and sex; and (iii) growth plasticity in response to environmental factors, using divergent wild and domesticated Atlantic salmon (Salmo salar). Our work examined two populations and their multigenerational hybrids in a common experimental arrangement in which salinity and quantity of suspended sediments were manipulated to mimic naturally occurring environmental variation. Average specific growth rates across environments differed among crosses, maturity groups, and cross-by-maturity groups, but a growth-rate reduction in the presence of suspended sediments was equal for all groups. Our results revealed both additive and nonadditive outbreeding effects for size at age and for growth rates that differed with life stage, as well as the presence of different sex- and size-specific maturation probabilities between populations. The major implication of our work is that estimates of the genetic architecture of growth and maturation can be biased if one does not simultaneously account for temporal changes in growth and for different maturation probabilities between populations. Namely, these correlated traits interact differently within each population and between sexes and among generations, due to nonadditive effects and a level of independence in the genetic control for traits. Our results emphasize the challenges to investigating and predicting phenotypic changes resulting from between-population outbreeding.

Enhancement of toxic effects of phenanthrene to Daphnia magna due to the presence of suspended sediment

In the present work, the influences of suspended sediment (SPS) on the toxic effects of phenanthrene (PHE), one kind of polycyclic aromatic hydrocarbons, to Daphnia magna was studied using a dialysis bag simulation system, which equalized the freely dissolved concentration of PHE between outside the dialysis bag in the presence of SPS and inside the dialysis bag in the absence of SPS. The immobilization and total superoxide dismutase (T-SOD) activity of Daphnia magna caused by PHE (0–0.8mgL−1) were investigated under the influence of different SPS concentrations (0, 1, 3, 5gL−1) during a 96h-exposure. The results showed that, compared to the absence of SPS, the presence of SPS (1–5gL−1) increased the immobilization of Daphnia magna by 1.6–2.7 times when the freely dissolved concentration of PHE was identical in both systems. The inhibition of T-SOD activity of Daphnia magna by PHE was significantly greater in the presence of SPS than in the absence of SPS (p<0.01). This infers that the PHE sorbed on SPS might be bioavailable and enhanced the toxic effect of PHE to Daphnia magna. The bioavailable fraction of PHE sorbed on SPS ranged from 10.1% to 22.7%, and the contribution of PHE sorbed on SPS to the immobilization caused by total PHE in the exposure system increased with SPS concentration, with the contribution ratio increasing from 36.7% to 57.7% when SPS concentration increased from 1 to 5gL−1. This study suggests that only considering the concentrations of hydrophobic organic compounds in the water phase may underestimate their toxicity; and the hydrophobic organic compounds sorbed on SPS should not be ignored in assessment of water quality and the establishment of water quality standard in the future.

Is the von Kármán constant affected by sediment suspension?

Is the von Kármán constant affected by sediment suspension? The presence of suspended sediment in channels and fluvial streams has been known for decades to affect turbulence transfer mechanism in sediment‐laden flows, and, therefore, the transport and fate of sediments that determine the bathymetry of natural water courses. This study explores the density stratification effects on the turbulent velocity profile and its impact on the transport of sediment. There is as yet no consensus in the scientific community on the effect of sediment suspension on the von Kármán parameter,κ. Two different theories based on the empirical log‐wake velocity profile are currently under debate: One supports a universal value ofκ = 0.41 and a strength of the wake, Π, that is affected by suspended sediment. The other suggests that both κ and Π could vary with suspended sediment. These different theories result in a conceptual problem regarding the effect of suspended sediment on κ, which has divided the research area. In this study, a new mixing length theory is proposed to describe theoretically the turbulent velocity profile. The analytical approach provides added insight defining κas a turbulent parameter which varies with the distance to the bed in sediment‐laden flows. The theory is compared with previous experimental data and simulations using ak‐εturbulence closure to the Reynolds averaged Navier Stokes equations model. The mixing length model indicates that the two contradictory theories incorporate the stratified flow effect into a different component of the log‐wake law. The results of this work show that the log‐wake fit with a reducedκ is the physically coherent approximation.

Effects of suspended sediments on reproductive responses of Paracalanus sp. (Copepoda: Calanoida) in the laboratory

The ingestion rate, egg production, egg-hatching success and survival rate of adult female copepods, Paracalanus sp., in relation to a suspended sediment concentration gradient (control: 0 mg L, low: 10 mg L, middle: 30 mg L and high: 100 mg L) were examined in the laboratory under two concentrations (1 10 and 1 10 cells mL) of the dinoflagellate Prorocentrum minimum to understand the impacts of turbidity on the reproductive responses. Ingestion rates under both phytoplankton concentrations were significantly lower at high level of suspended sediments than at the control level. The egg production rate at the low phytoplankton concentration also decreased with increasing suspended sediment concentration, but there was no effect of suspended sediment on egg production at the high phytoplankton concentration. Egg-hatching success was relatively high at .90%; thus, there was no deleterious effect of suspended sediments on egg viability. The survival rate of adult females decreased with time in all treatments, indicating no negative effects of suspended sediments on the mortality of female copepods. These results suggest that higher concentrations of suspended sediments might have negative effects on copepod recruitment in the field. Feeding efficiency on phytoplankton decreased in the presence of suspended sediments, thus potentially decreasing the copepod egg production rate. However, the negative effects may be lessened if the copepod ingests more food in terms of both quality and quantity in favorable food environments.

Submerged hydraulic jump with sediment-laden flow

In this experimental study, the effect of suspended sediment concentration on the characteristics of a submerged hydraulic jump in a rectangular channel has been investigated, based on the sediment concentrations of 0.43%-16.15% and jet Froude numbers were in the range of 1.9-5. Two grain sizes, 0.15 and 0.03 mm (ρs=2.65 g/cm3) have been used in the experiments. Characteristics of the submerged hydraulic jump including the submergence depth at the gate, length of submerged hydraulic jump, energy dissipation, velocity, and concentration distribution have been studied in both smooth and rough beds. Results showed that the submergence depth at the gate and the energy dissipation were constant regardless of sediment concentration. However, in the presence of suspended sediment, the length of the submerged hydraulic jump is smaller than that of clear water flow. It was also found that suspended sediment increase flow resistance, as a result of decreased in the maximum flow velocity.

A new bio-optical algorithm for the remote sensing of algal blooms in complex ocean waters

[1] A new bio-optical algorithm has been developed to provide accurate assessments of chlorophyll a (Chl a) concentration for detection and mapping of algal blooms from satellite data in optically complex waters, where the presence of suspended sediments and dissolved substances can interfere with phytoplankton signal and thus confound conventional band ratio algorithms. A global data set of concurrent measurements of pigment concentration and radiometric reflectance was compiled and used to develop this algorithm that uses the normalized water-leaving radiance ratios along with an algal bloom index (ABI) between three visible bands to determine Chl a concentrations. The algorithm is derived using Sea-viewing Wide Field-of-view Sensor bands, and it is subsequently tuned to be applicable to Moderate Resolution Imaging Spectroradiometer (MODIS)/Aqua data. When compared with large in situ data sets and satellite matchups in a variety of coastal and ocean waters the present algorithm makes good retrievals of the Chl a concentration and shows statistically significant improvement over current global algorithms (e.g., OC3 and OC4v4). An examination of the performance of these algorithms on several MODIS/Aqua images in complex waters of the Arabian Sea and west Florida shelf shows that the new algorithm provides a better means for detecting and differentiating algal blooms from other turbid features, whereas the OC3 algorithm has significant errors although yielding relatively consistent results in clear waters. These findings imply that, provided that an accurate atmospheric correction scheme is available to deal with complex waters, the current MODIS/Aqua, MERIS and OCM data could be extensively used for quantitative and operational monitoring of algal blooms in various regional and global waters.