Turbid Water Environment Research Articles

Solitary corals of the Campanian Hajajah Limestone Member, Aruma Formation, Central Saudi Arabia

Fourteen species of the solitary corals belonging to eight genera and six families were identified and illustrated from the Campanian – Maastrichtian Aruma Formation, northeast of Riyadh, Saudi Arabia. Cunnolites (Plesiocunnolites) riyadhensis, Actinoseris riyadhensis and Asteroseris arabica are believed to be new. Genus Cunnolites dominates the identified fauna with six species namely Cunnolites (C.) reussi, C. (P.) orbignyi, C. (P.) longifossata, C. (P.) scutellum, C. (C.) profundus and C. (P.) riyadhensis (n. sp.). The other species belong to Aulosmilia cuneiformis, Rennensismilia inflexa, Rennensismilia sp., Acrosmilia conica, Actinoseris riyadhensis (n. sp.), Asteroseris arabica (n. sp.), Montlivaltia sp. and Conicosmilotrochus sp. The solitary corals have various growthforms from cupolate to flabellate, trochoid, ceratoid, cylindrical and patellate. The studied taxa inhabit soft substrate in turbid water environment with low rate of sedimentation. Borings and scars are rare, encrustations occur on the lower surfaces of some specimens. Partial mortality, overgrowths, disorientation or any records of life impedences due to sedimentation and unstable substrate were not observed in the studied specimens. Pedestals and columnar growths are also absent. Bioerosion is observed in some specimens in the form of pittings produced by predators.

Retrieving Total Suspended Matter in Tropical Reservoirs Within a Cascade System With Widely Differing Optical Properties

Total suspended matter (TSM) is an important indicator of water quality and has an adverse effect on light propagation in the water affecting the primary production. Moderate resolution imaging spectroradiometer (MODIS) data have been widely used to develop numerous semiempirical models all over the world. In this paper, many of these models perform satisfactorily either in a single water body or in many similar turbid water environments, however, their performance drops when data from oligo-to-eutrophic environments are used to monitor all reservoirs simultaneously. Most of them tend to overestimate TSM at low concentration. Two separate model calibrations were used to monitor the spatio-temporal variability of TSM in two oligo-to-eutrophic reservoirs, Nova Avanhandava (Nav) and Barra Bonita (BB), situated in the cascade system of Sao Paulo State, Brazil. The exponential model using MODIS band 1 yielded the best accuracy for BB (RMSE = 3.66 mg/L) and MODIS band 1 based linear model showed the best performance for Nav (RMSE = 0.37 mg/L). The distribution of TSM in Nav showed comparatively low and homogenous concentrations for the entire reservoir but the magnitude doubled for a period between May and October. The same seasonal variability occurred in BB showing increased TSM trend in October compared to May, but the spatial variability was not homogeneous because of the runoff from Piracicaba River, which is the main contributor of TSM. Rainfall associated runoff and land use and land cover were the principal factors for TSM variability.

Platy corals from the Middle Triassic of Upper Silesia, Poland: Implications for photosymbiosis in the first scleractinians

Coral patch reefs from Middle Triassic (upper Pelsonian–lower Illyrian) strata in the Upper Silesia region of southern Poland (Germanic domain of the Peri-Tethys) are rare examples of the first scleractinian buildups. The shallowing-upward succession in the Tarnów Opolski quarry records a transition from sponge to coral patch reefs interbedded with bioclastic limestones. Coral pillarstones built by thin, branching Volzeia szulci are succeeded by platy Pamiroseris silesiaca constructing two platestone layers, each up to 50cm thick. Serial sections through platestones revealed flat to undulose growth form of P. silesiaca. The maximum observable dimension of the coral plates is 24cm wide (typically up to 12cm), while thickness of most plates is 1–1.5cm. Coral plates are interlayered with crinoidal wacke- to packstone and microbialites, which are locally important component of the platestone. Platy corals grew in a shallow, turbid-water environment with changing, but dominantly moderate hydrodynamics. Net sedimentation was low, as indicated by the epibionts encrusted to the undersides of the coral plates, and locally common microbial fabrics. Growth-interruptions of P. silesiaca record events of storm-induced sediment input and resuspension of carbonate mud. Based on the euphotic floor model, the flattened morphology of P. silesiaca is interpreted as an optimal growth form in a turbid, low-light environment. Platy scleractinian assemblages from Silesia are the oldest occurrences of this ecological coral group (mostly representing deeper, mesophotic habitats) and support the hypothesis that some of the earliest scleractinians had photosymbionts like modern zooxanthellae.

Simulation of the fate of faecal bacteria in estuarine and coastal waters based on a fractionated sediment transport model

A two-dimensional depth-integrated numerical model is refined in this paper to simulate the hydrodynamics, graded sediment transport process and the fate of faecal bacteria in estuarine and coastal waters. The sediment mixture is divided into several fractions according to the grain size. A bed evolution model is adopted to simulate the processes of the bed elevation change and sediment grain size sorting. The faecal bacteria transport equation includes enhanced source and sink terms to represent bacterial kinetic transformation and disappearance or reappearance due to sediment deposition or re-suspension. A novel partition ratio and dynamic decay rates of faecal bacteria are adopted in the numerical model. The model has been applied to the turbid water environment in the Bristol Channel and Severn estuary, UK. The predictions by the present model are compared with field data and those by non-fractionated model.

Atmospheric correction of hyperspectral airborne GCAS measurements over the Louisiana Shelf using a cloud shadow approach

ABSTRACTAs an image-driven method to correct for atmospheric effects, the cloud shadow (CS) approach does not require accurate radiometric calibration of the sensor, making it feasible to process remotely sensed data when radiometric calibration may contain non-negligible uncertainties. Using measurements from the Geostationary Coastal and Air Pollution Events Airborne Simulator and from the Moderate Resolution Imaging Spectroradiometer over the Louisiana Shelf, we evaluate the CS approach to airplane measurements in turbid-water environments. The original CS approach somehow produced remote-sensing reflectance (Rrs, sr−1) with an abnormal spectral shape, likely a result of the assumption of identical path radiance for the pair of pixels in and out of the shadow, which is not exactly valid for measurements made from a low-altitude airplane. To overcome this limitation, an empirical scheme using an effective wavelength-dependent radiance reflectance for the cloud (γ, sr−1) was developed and reasonable GCAS Rrs retrievals are then generated, which were further validated against in situ Rrs. Issues and challenges in applying CS to measurements of low-altitude airplanes are discussed.

Water Environment Remote Sensing Atmospheric Correction of Geostationary Ocean Color Imager Data over Turbid Coastal Waters in the Bohai Sea Using Artificial Neural Networks

The Geostationary Ocean Color Imager (GOCI) can produce good ocean colour products in the open sea. However, an atmospheric correction problem continues to occur for turbid coastal water environment monitoring. In this communication, a regional atmospheric correction method based on an artificial neural network (ANN) model has been proposed. The ANN model was built according to differences in the spatial and radiometric characteristics between the Medium Resolution Imaging Spectrometer (MERIS) and GOCI, with 3000 pixels of the top-of-atmosphere (TOA) reflectance of seven GOCI images from 2011 to 2012 above turbid water used as the inputs and coinciding validated remote-sensing reflectance (Rrs) of MERIS 1 used as the outputs. Subsequently, the water-leaving reflectance of GOCI in turbid coastal water areas of the Bohai Sea was derived. Compared with the products produced by the standard GOCI Data Processing System (GDPS Version 1.3), the Rrs retrieved according to the proposed method showed a significant improvement in spatial pattern. Although the ANN model displayed a degree of difficulty in representing high water-leaving reflectance values, a comparison with three in situ measurements collected on 11 November 2011 in the study area showed encouraging results. The results suggest that the ANN method can be used for atmospheric correction process in turbid waters without requiring numerous in situ measurements.

Impulse response modeling for general underwater wireless optical MIMO links

In underwater wireless optical communications (UWOC), channel modeling plays a key role in investigating the propagation properties of light beams through UWOC links as well as evaluating overall system performance. We consider UWOC multiple-input and multiple-output (MIMO) systems with multiple light sources and detectors, and focus on the impulse response that is capable of characterizing the temporal behavior of UWOC links. We propose a weighted Gamma function polynomial (WGFP) to model the impulse response of general UWOC MIMO links with arbitrary numbers of light sources and detectors. Numerical results of Monte Carlo simulations have validated the proposed WGFP model in a turbid water environment.

General Stochastic Channel Model and Performance Evaluation for Underwater Wireless Optical Links

In underwater wireless optical communications (UWOC), absorption and scattering characterize the link properties since photons may suffer these two processes with energy loss and direction change, respectively, when interacting with water molecules or suspended particles. In this work, we consider the effects of absorption and scattering on the probability distribution, i.e., normalized intensity distribution, of photons in space and time domains. Our prior work proposed a stochastic channel model to represent the spatial–temporal probability distribution of propagated photons only for nonscattering and single scattering components of UWOC links. However, multiple scattering will dominate the scattering behavior of the underwater environment with long communication distance and/or more turbid water type. In this work, we take into account all three types of components including nonscattering, single and multiple scattering, and present a more general stochastic channel model which fits well with Monte Carlo simulations in turbid water environment such as coastal and harbor water. Based on the proposed channel model, we also evaluate the performance of path loss, scattering richness, and attenuation of UWOC links. Numerical results suggest that multiple scattering can compensate the path loss overestimated by traditional approaches. Furthermore, scattering richness and attenuation tend to increase but have opposite effects to raise and reduce the received probabilities of higher order scattered photons, respectively, as link range increases.

Hybrid technique for enhanced optical ranging in turbid water environments

A hybrid approach is described that enhances the performance of an underwater optical ranging system. This approach uses high-frequency modulation and a spatial delay line filter to suppress unwanted backscatter. A dual frequency approach is also implemented to reduce the effects of forward scatter and remove the ambiguity associated with using the phase of the single, high-frequency modulation envelope to measure range. Controlled laboratory experiments were conducted to evaluate the effectiveness of the hybrid technique to reject multiple scattered light and improve range precision. The experimental results were compared with data generated from a theoretical model developed to predict the performance of the technique as a function of system and environmental variables. Model and experimental results are shown that reveal the ability of the approach to provide accurate ranging to an underwater object in a variety of water environments. Model predictions also indicate that advancements in transmitter and receiver technology will extend the range and improve the accuracy of the technique beyond what has been achieved thus far.

Extended-Range Undersea Laser Imaging: Current Research Status and a Glimpse at Future Technologies

AbstractRecent advancements in obtaining visibility of undersea objects at extended ranges in coastal and oceanic waters are reviewed for the years 2009 to present. The paper focuses on the latest techniques that are utilized to reduce the undesirable effects of scattering, mainly due to suspended particulate within the imaging volume, leading to the loss of contrast and blurring characteristic of undersea optical images produced over long ranges. Several recent sets of experimental results obtained using both benchtop laboratory development systems as well as field-deployable prototypes of new system concepts are presented, with observed performance attributes being discussed. Simulation studies that make use of accurate radiative transfer physical models to enable design and operation of new system concepts within a turbid water environment are also presented. Finally, this paper includes a description and results from an extended-range laser system that has reached a level of packaging and automation necessary to be available as a commercial product.

MICROTAPHOFACIES ANALYSIS OF LOWER OLIGOCENE TURBID-WATER CORAL ASSEMBLAGES

The presence, distribution, and preservation of coral-rich facies in the lower Oligocene Gornji Grad Beds of Slovenia are analyzed using a microtaphofacies approach. This method allows taphonomic signatures to be recognized in thin section along with the presence of coral specimens and growth forms within and between stratigraphic logs. Coral-dominated limestones within the Gornji Grad Beds are represented by rudstones in a packstone-wackestone matrix. The conditions are generally reconstructed as turbid water due to the prevalence of muddy carbonate matrix, which also leads to excellently preserved morphological features in thin section. These beds represent a reference area for the study of Paleogene corals, especially during the Oligocene, a key phase of reef development during the Cenozoic. This study also contributes to the characterization of fossil reefs in turbid-water environments. The evaluated coral fauna is dominated by delicate-branching Stylophora and Acropora, although thickly branching (Actinacis, Goniopora), phaceloid (Caulastrea), and massive forms (Alveopora, Astreopora, Antiguastrea) also occur. Assessed taphonomic signatures include fragmentation, abrasion, bioerosion, and encrustation. Three types of bioerosion traces are distinguished (Entobia, Gastrochoenolites, Trypanites). Encrustation incl udes both thin crusts and complex multi-taxon sequences dominated by coralline algae. Five microtaphofacies are distinguished based on variation of taphonomic signatures, taxonomic composition, and growth forms. Differences in microtaphofacies are interpreted with respect to turbidity, sediment accumulation, and water turbulence; both parautochthonous and allochthonous deposits are reconstructed. A depositional model based on the distribution of microtaphofacies in the studied sections shows a succession of coral communities with different colonization strategies reflecting generally high stress levels.

Impact of stress and disturbance factors on the phytoplankton communities in Northeastern Brazil reservoir

The ecology of phytoplankton reservoir communities plays a pivotal role in their management and in the development of inland fisheries in the water scarce semi-arid regions of Rio Grande do Norte State, Brazil. The hydrological conditions characterizing these reservoirs include infrequent rainfall and high evaporative loses. The phytoplankton assemblages in tropical climate are structured primarily on dry and wet cycles, not the annual temperature and light regime. The purpose of the current study was to investigate the ecological aspects of phytoplankton communities from three reservoirs during the period of July 2003–June 2004, which include atypical summer rainfall and reservoir overflow. The environmental data broadly divided into two categories, stress factors and disturbance factors. The stress factors deals with the impact of high particulate organic matter and low dissolved oxygen concentrations and disturbance factors, linked to water level fluctuation through flushing and reservoir drawdown, and these events are associated with the phytoplankton assemblages. Results indicated that the three distinct hydroperiods determined the structure of phytoplankton and chlorophyll levels and limited the presence and relative abundance of cyanobacterial species. Phytoplankton succession accompanied changes in clear and turbid water phase represented by the alternate dominance between diatoms and chlorophytes. Inundation and complete filling of reservoir stimulated “s” and “r” strategists species (<20 um) of unicellular and some colonial members of chlorophytes and cryptomonads in highly turbid water environment, and “c” strategist species in rest of the wet period following disturbance gradients. Statistical analysis elicited a significant relationship between particulate organic matter and relative abundance of smaller chlorophytes, which was deemed as stress factor. The flushing and reservoir drawdown indicate disturbance gradient and as a consequence high diversity. Furthermore, a substantial reduction in chlorophyll levels was registered in turbid water phase is related to the reduction of light penetration and re-suspension of sediments. Considering these results, it can be suggested that the well-managed reservoir drawdown can possibly maintain an environment free of eutrophication and cyanobacterial dominance.

Modelling enteric bacteria level in coastal and estuarine waters

Details are given in this paper of the development of a numerical model for describing the bacterial transport processes in estuarine and coastal waters. The transport of enteric bacteria is influenced by many physical, chemical and biological factors, including both the suspended and bed sediments. In recent years, an increasing number of studies have shown that generally the sediments contain much higher bacterial population levels than previously assumed. The aim of this study has been to develop a numerical modelling tool for predicting the sediment-linked bacterial concentration levels in coastal and estuarine waters. This paper outlines the theoretical background of an enteric bacterial water quality numerical model. A conceptual model has been established for representing the transport of bacteria due to sediment movement, including deposition and suspension. Details are given of the solute and mass transport equations used to simulate the flow and transport of suspended sediments and enteric bacterial indicators. The enteric bacteria transport equation includes enhanced source and sink terms to represent bacterial kinetic transformation and disappearance or reappearance due to sediment deposition or resuspension. The model has been applied to the turbid water environment in the Bristol Channel and Severn estuary, UK, with initial results from the modelling study being presented.

Preference polymorphism for coloration but no speciation in a population of Lake Victoria cichlids

Female mating preference based on male nuptial coloration has been suggested to be an important source of diversifying selection in the radiation of Lake Victoria cichlid fish. Initial variation in female preference is a prerequisite for diversifying selection; however, it is rarely studied in natural populations. In clear water areas of Lake Victoria, the sibling species Pundamilia pundamilia with blue males and Pundamilia nyererei with red males coexist, intermediate phenotypes are rare, and most females have species-assortative mating preferences. Here, we study a population of Pundamilia that inhabits turbid water where male coloration is variable from reddish to blue with most males intermediate. We investigated male phenotype distribution and female mating preferences. Male phenotype was unimodally distributed with a mode on intermediate color in 1 year and more blue-shifted in 2 other years. In mate choice experiments with females of the turbid water population and males from a clearer water population, we found females with a significant and consistent preference for P. pundamilia (blue) males, females with such preferences for P. nyererei (red) males, and many females without a preference. Hence, female mating preferences in this population could cause disruptive selection on male coloration that is probably constrained by the low signal transduction of the turbid water environment. We suggest that if environmental signal transduction was improved and the preference/color polymorphism was stabilized by negative frequency-dependent selection, divergent sexual selection might separate the 2 morphs into reproductively isolated species resembling the clear water species P. pundamilia and P. nyererei.

Adaptations in the structure and innervation of follicle‐sinus complexes to an aquatic environment as seen in the Florida manatee (Trichechus manatus latirostris)

Florida manatees are large-bodied aquatic herbivores that use large tactile vibrissae for several purposes. Facial vibrissae are used to forage in a turbid water environment, and the largest perioral vibrissae can also grasp and manipulate objects. Other vibrissae distributed over the entire postfacial body appear to function as a lateral line system. All manatee vibrissae emanate from densely innervated follicle-sinus complexes (FSCs) like those in other mammals, although proportionately larger commensurate with the caliber of the vibrissae. As revealed by immunofluorescence, all manatee FSCs have many types of C, Adelta and Abeta innervation including Merkel, club, and longitudinal lanceolate endings at the level of the ring sinus, but they lack other types such as reticular and spiny endings at the level of the cavernous sinus. As in non-whisking terrestrial species, the inner conical bodies of facial FSCs are well innervated but lack Abeta-fiber terminals. Importantly, manatee FSCs have two unique types of Abeta-fiber endings. First, all of the FSCs have exceptionally large-caliber axons that branch to terminate as novel, gigantic spindle-like endings located at the upper ring sinus. Second, facial FSCs have smaller caliber Abeta fibers that terminate in the trabeculae of the cavernous sinus as an ending that resembles a Golgi tendon organ. In addition, the largest perioral vibrissae, which are used for grasping, have exceptionally well-developed medullary cores that have a structure and dense small-fiber innervation resembling that of tooth pulp. Other features of the epidermis and upper dermis structure and innervation differ from that seen in terrestrial mammals.

The relationship between autotrophic picoplankton (APP) - the smallest autotrophic component of food web and the trophic status and the depth of lakes

The occurrence and dynamics of autotrophic picoplankton (APP) in relation to the trophic status of a lake is discussed basing on results from 9 lakes situated in northeastern Poland and southern Finland. The lakes varied in the concentration of basic nutrients, chlorophyll a, phytoplankton biomass, pH depth and the composition of APP.A positive relationship between the productivity of the lakes and the APP biomass was confirmed. Shallow lakes were characterised by a significantly higher abundance and biomass of APP than deeper lakes, regardless of their trophic status. The abundance of APP as well as its contribution to the total phytoplankton biomass in the studied shallow lakes was also higher, than it could be expected from the level of basic nutrients in those lakes.Results imply that, when compared to deep lakes of a comparable trophic level, shallow and occasionally turbid water environment may create favourable conditions for APP, enabling it to occur in high numbers and thus influence the carbon cycling causing an increase of the carbon flow through the microbial food webs.