Natural Beds Research Articles

Impact of bed surface arrangement on bedload rate: comparisons between loose, armored and water-worked beds

Existing formulas for predicting bedload rate may be not adapted for mountain rivers with poorly sorted sediments, partly because they were often established using laboratory data with conditions far from those found in such rivers. Natural bed arrangement is particularly difficult to reproduce in flumes, although recent studies highlighted its importance on bedload dynamics. This study aims to quantify bed arrangement impact on bedload rate using original laboratory tests and to improve existing bedload formulas. Three types of bed composed with the same material but having different bed arrangements were studied: loose beds were installed manually in the flume and the others, packed and water-worked beds, were created using water power. Packed beds were assimilated to flat beds composed of a static armor layer whereas water-worked beds exhibited stronger bed organization, including large-scale bed forms. Laser-scanner surveys were used to characterize differences in bed morphology. Similar unsteady hydraulic conditions were applied over these beds. Results showed that bedload dynamics varies significantly depending on the initial arrangement. Compared to loose bed, bedload was enhanced over water-worked bed and reduced over packed bed. Bed surface indicators are thus important parameters to take into account when predicting gravel transport.

Oyster culture on the Amazon mangrove coast: asymmetries and advances in an emerging sector

AbstractOyster culture activity along the eastern Amazon mangrove coast in Pará state, Brazil, was evaluated using socio‐economic data to support its management and future development. Between 2013 and 2014, surveys were carried out in the region's seven oyster culture associations through interviews with the president of each association as well as with 56 members (72% of the total). Further data up to 2016 were obtained from annual reports of the Serviço Brasileiro de Apoio às Micro e Pequenas Empresas in Pará and the Instituto Brasileiro de Geografia e Estatística. Two associations stand out from the rest due to their larger on‐growing areas and total production in 2013. However, smaller associations are more efficient with higher production per unit area. Currently, oyster culture in Pará provides an alternative source of income for 80 families, where total production has increased from 8.25 tons in 2013 to 41.8 tons in 2016. Although associations have grown in number since 2006, along with increased capacity and production due to government assistance, in comparison with other regions of Brazil, they need to be better organized internally, including regular monitoring of growth, production and environmental variables, development of depuration facilities and improved distribution and presentation of products. Diversification of seed supply among different locations is desirable. There should also be less dependence on public funding and more partnerships with private enterprise, as well as active coparticipation in the development of legislation and public policies regulating both oyster culture and protection of natural oyster beds.

Pathogenicity and antibiotic susceptibility of two bacterial pathogens associated with the clam Tapes decussatus in some Egyptian fisheries

Bivalve aquaculture is generally influenced by bacterial pathogens that cause high mortality-related losses in hatcheries. Six bacterial phenotypes had been previously isolated as the most predominant microorganisms in carpet shell clam ( Tapes decussates ) samples collected from natural beds in representative Egyptian clam fisheries. The main aims of this study were to investigate the nature of the pathogenic strains that significantly affect clam survival and test their susceptibility to commercially available antibiotics. Based on their 16S rRNA sequences and some biochemical features, two potent clam pathogens were emerged; one of which is gram-positive and the other is gram-negative. The former isolate was identified as Micrococcus luteus and the latter as Vibrio alginolyticus . Experimental challenges with the two bacterial pathogens introduced at different initial cell concentrations (2.5 X 10 4 - 7.5 X 10 4 cfu ml -1 ) showed markedly diverse clam mortality results. However, the pathogenic interaction of M. luteus with clam survival was generally higher than that of V. alginolyticus . When introduced at a relatively low initial cell density, the infectious records of V. alginolyticus were significantly increased suggesting that the expression of its key virulence factors is mainly triggered as a response to host contact. Antibiotic susceptibility tests suggested chloramphenicol and tetracycline as markedly effective agents that can be used to control the spread of these two bacterial pathogens in aquaculture applications.

The Impact of Qanat In Physical Form Case Study: Mohammadiyeh Village, Nain, Iran

Cities and settlements in the Iranian Plateau are developed in deep relationship with and dependence on water sources and systems governing them. A clear manifestation of this all-inclusive link between the settlement and the water production and distribution system can be found in Mohammadiyeh, in central Iranian deserts. The system that was developed based on groundwater recovery and its transportation by Qanat still remains today with little change. There are multiple aspects to this system with respect to the community and the life of inhabitants. This water system has remained for centuries and is systematically developed. Considering that the water network of Mohammadiyeh Qanat is one of the few surviving samples in Iran, and due to climate change and the rising water crisis in this dry area of Iranian plateau, and with attention to the historic and influential role of water networks in formation of settlements, the historical study of the water networks in the Iranian Plateau areas gives a significant document for recognizing of various aspects and capacities between the settlement and Qanat. The purpose of this research is analyzing of Qanat role and its effects on the components of the physical structure of Mohammadiyeh fabric and also the study of Qanat’s effects on the structural differences of water access elements in comparison with public and private buildings. For this purpose, descriptive-analytic research method has been used and the data has collected through library studies, field studies and oral interviews. The findings of the research indicate that the Qanat effects on physical structure of Mohammadiyeh city in some components such as finding and choosing the establishment place (in relation to topography and the natural bed), the totality of the fabric (organic and full compressed), the formation of the communication arteries and the network of passages (adherence of transit network from the Qanat route and the gradual organic pattern of the fabric) and the organization of public spaces and residential units.

Stabilizing Effects of Bacterial Biofilms: EPS Penetration and Redistribution of Bed Stability Down the Sediment Profile

AbstractBiofilms, consisting of microorganisms and their secreted extracellular polymeric substances (EPSs), serve as “ecosystem engineers” stabilizing sedimentary environments. Natural sediment bed provides an excellent substratum for biofilm growth. The porous structure and rich nutrients allow the EPS matrix to spread deeper into the bed. A series of laboratory‐controlled experiments were conducted to investigate sediment colonization of Bacillus subtilis and the penetration of EPS into the sediment bed with incubation time. In addition to EPS accumulation on the bed surface, EPS also penetrated downward. However, EPS distribution developed strong vertical heterogeneity with a much higher content in the surface layer than in the bottom layer. Scanning electron microscope images of vertical layers also displayed different micromorphological properties of sediment‐EPS matrix. In addition, colloidal and bound EPSs exhibited distinctive distribution patterns. After the full incubation, the biosedimentary beds were eroded to test the variation of bed stability induced by biological effects. This research provides an important reference for the prediction of sediment transport and hence deepens the understanding of the biologically mediated sediment system and broadens the scope of the burgeoning research field of “biomorphodynamics.”

First characterization report of natural pearl of Pinctada fucata from Gulf of Mannar

The present study is aimed to characterize the natural pearl of Pinctada fucata from Gulf of Mannar by Scanning Electron Microscope (SEM) and Energy Dispersive Studies (EDS). Pearl oysters (P. fucata) from Kayalpattinam, Gulf of Mannar, were landed as a by-catch in the bottom set gill net at a depth of 4m and collected for tissue culture studies. During mantle tissue dissection, a good lustrous, round pearl of 1.5mm size was found in the mantle fold of pearl oyster P. fucata. This evidenced the existence of natural pearl oyster beds and natural pearls in this region. It was analyzed by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) to find out the composition of nacre. Parallel orientation of crystals to form the lamellar formation of nacre is clearly visible in SEM. Pseudo-hexagonal aragonite crystals arranged in a uniform layer and joined together to form a lamella with inter-lamellar matrix. Two forms of calcium (CaO and CaCO3) obtained in EDS analysis. Calcium content in the natural pearl is 66.05% which is clearly reveals the aragonite form. Niobium (Nb) was attained at 6% in natural pearl which is the first report in its kind and it may also play a role in the formation of lustrous layer. There are so many characterization reports available about mother of pearl in shell of different species, but this is the first report of natural pearl from P. fucata.

An integrated method for rapid estimation of the valley incision by debris flows

Valley incision by debris flow is an important process in creating and maintaining the topography of a valley, in addition to explaining the significant growth of the magnitudes of debris flow hazards. In this paper, we introduce a semi-empirical method to quantitatively estimate the valley incision process by debris flows over complex bed surface. We first reproduce natural bed surface across the valley by a polyline, and use a hydrograph of discharge versus time to represent the temporal variation of debris flow process. The presented method subsequently predicts the debris flow behavior over an irregular bed surface. A dynamic erosion law considers the solved debris flow behavior and estimates an instantaneous erosion rate. Finally, the accumulative incision depth of bed sediment is calculated, reshaping the initial bed surface across the valley. The presented method is simple and therefore notably beneficial for practical work. The performance of the proposed method has been tested using two case study applications. Results demonstrate that the presented method estimates comparable incision depth as revealed in the in-situ survey and the numerical simulation.

Suspended culture of Chondracanthus chamissoi (Rhodophyta: Gigartinales) in Caleta Hornos (northern Chile) via vegetative propagation with secondary attachment discs

Vegetative propagation of Chondracanthus chamissoi by means of secondary attachment discs (SAD) has been an effective strategy for maintaining the species biomass in natural beds. Suspended culture was used in the present study. Biomass, epiphytes, length of new thalli, and number of secondary attachment discs of C. chamissoi were measured during different seasons as well as different depths (2, 4, and 6 m), and cultivation times (1, 2, 3, and 4 months). The greatest accumulation of biomass, biofouling, and SAD formation occurred during spring cultivation, while maximum lengths were observed in winter. Maximum values of each variable were observed at 2 m depth in most cases.

Determination of Salmonella spp., E. coli VTEC, Vibrio spp., and Norovirus GI-GII in Bivalve Molluscs Collected from Growing Natural Beds in Sardinia (Italy).

The aim of the present study was to evaluate the presence of Salmonella spp., verotoxigenic E. coli (VTEC), Vibrio spp., and Norovirus GI-GII in bivalve molluscs, cockles, and European grooved carpet shells (Cerastoderma spp. and Ruditapes decussatus) collected from a class B growing natural bed in Sardinia (Italy). All of the samples were analysed for Salmonella spp. detection according to European Commission Regulation (EC) 2285/2015. Detection and enumeration of Vibrio spp. were performed according to previously published methods. Presumptive identification of Vibrio spp. isolates was performed by means of conventional biochemical tests. E. coli VTEC was isolated following a direct multiplex polymerase chain reaction (PCR) screening test. Norovirus GI and GII were determined by reverse transcriptase-polymerase chain reaction (RT-PCR). No Salmonella spp. were detected. The prevalence of Vibrio spp. was 90%, and the average contamination levels were 3.19 ± 1.07 and 2.84 ± 0.31 Log10 cfu/g in cockles and European grooved carpet shells, respectively. The prevalence of E. coli VTEC was 6.6%. All of the isolates showed a complete pathogenicity profile. The presence of Norovirus was highlighted in 25% of European grooved carpet shells samples. Results showed the typical microbiological profile of bivalve molluscs collected from backwaters and confirmed the capability of shellfish to accumulate E. coli VTEC, pathogenic vibrios, and Norovirus. The presence of such pathogens in shellfish is of major concern for the safety of consumers.

Sustainable harvesting of wild seaweed resources

Macroalgae have played an important role in coastal communities for centuries. In the past, they have been harvested and gathered from shorelines around the world for traditional uses such as food, animal feed and a crude fertilizer (marine manure). Today, seaweeds are used in a multitude of applications with expanding global industries based on hydrocolloids, cosmetics and food supplements, and also as a potential biofuel source. However, of the approximately 10 000 algal species reported to exist, only a small number are commercially utilized. While representing only a small fraction of total global seaweed production, harvesting and gathering ‘wild’ seaweeds has had, and continues to have, an integral role in many coastal societies, often being intrinsically linked to the cultural identity of those coastal communities. Today, 32 countries actively harvest seaweeds from wild stocks, with over 800 000 t harvested annually from natural beds. It is vitally important that seaweeds are utilized sustainably and that natural resources are effectively managed by coastal communities with vested interests around the world. As the popularity of seaweeds increases and the use of less traditional species with novel applications comes to the fore, it is critically important to make certain that the sustainability of the resource is ensured given the increased pressures of harvesting. Issues exist regarding ownership of the resource and its over-exploitation, and the implementation of environmentally damaging harvesting techniques must be avoided. Resource scientists, managers, conservationists, governments, and other stakeholders need to be proactive in the sustainable management of these vulnerable, yet valuable, resources.

Seaweed production: overview of the global state of exploitation, farming and emerging research activity

ABSTRACTThe use of seaweeds has a long history, as does the cultivation of a select and relatively small group of species. This review presents several aspects of seaweed production, such as an update on the volumes of seaweeds produced globally by both extraction from natural beds and cultivation. We discuss uses, production trends and economic analysis. We also focus on what is viewed as the huge potential for growing industrial-scale volumes of seaweeds to provide sufficient, sustainable biomass to be processed into a multitude of products to benefit humankind. The biorefinery approach is proposed as a sustainable strategy to achieve this goal. There are many different technologies available to produce seaweed, but optimization and more efficient developments are still required. We conclude that there are some fundamental and very significant hurdles yet to overcome in order to achieve the potential contributions that seaweed cultivation may provide the world. There are critical aspects, such as improving the value of seaweed biomass, along with a proper consideration of the ecosystem services that seaweed farming can provide, e.g. a reduction in coastal nutrient loads. Additional considerations are environmental risks associated with climate change, pathogens, epibionts and grazers, as well as the preservation of the genetic diversity of cultivated seaweeds. Importantly, we provide an outline for future needs in the anticipation that phycologists around the world will rise to the challenge, such that the potential to be derived from seaweed biomass becomes a reality.

Community Structure and Distribution of Natural Seaweed Beds on the Eastern Coast of Korea

Community Structure and Distribution of Natural Seaweed Beds on the Eastern Coast of Korea

Increased Walleye Egg‐to‐Larvae Survival following Spawning Habitat Enhancement in a Tributary of Eastern Lake Ontario

AbstractTo mitigate the effects of sedimentation from surrounding land use, a Newbury weir was installed in Kent's Creek (a tributary of eastern Lake Ontario) by the U.S. Fish and Wildlife Service Partners for Fish and Wildlife Program to enhance spawning habitat for Walleye Sander vitreus. By adding angular crushed limestone, the Newbury weir was designed as an engineered spawning riffle that creates a scouring effect to maintain clean spawning substrate for Walleyes. To evaluate the success of the Newbury weir, we compared rates of egg deposition, egg viability, and larval out‐migration between the created spawning riffle and a natural spawning bed for two seasons subsequent to its construction. Spawning Walleyes were found to immediately spawn on the created riffle following construction and demonstrated similar patterns of egg deposition and larval out‐migration at both sites each year. When data were pooled between years, significantly higher densities of out‐migrating larvae were observed at the Newbury weir despite the finding that significantly more eggs were spawned at the natural site. Considering that egg viability was similar between sites, we deduce that the created riffle had a higher egg‐to‐larvae survival rate. Our results suggest that the Newbury weir successfully created functional spawning habitat promoting out‐migrating larval Walleyes. We anticipate that the created riffle will maintain valuable spawning substrate for Walleyes, but sediments deposited from upstream eroding banks and agricultural land use practices could affect its long‐term viability. We recommend that future spawning habitat enhancement projects adopt similar approaches within appropriate fluvial geomorphic settings and additionally consider watershed‐scale improvements to enhance Walleye spawning tributaries.Received March 17, 2017; accepted May 26, 2017 Published online August 9, 2017

Organic molecule fluorescence as an experimental test-bed for quantum jumps in thermodynamics

We demonstrate with an experiment how molecules are a natural test bed for probing fundamental quantum thermodynamics. Single-molecule spectroscopy has undergone transformative change in the past decade with the advent of techniques permitting individual molecules to be distinguished and probed. We demonstrate that the quantum Jarzynski equality for heat is satisfied in this set-up by considering the time-resolved emission spectrum of organic molecules as arising from quantum jumps between states. This relates the heat dissipated into the environment to the free energy difference between the initial and final state. We demonstrate also how utilizing the quantum Jarzynski equality allows for the detection of energy shifts within a molecule, beyond the relative shift.

Behavioral self-organization underlies the resilience of a coastal ecosystem

Self-organized spatial patterns occur in many terrestrial, aquatic, and marine ecosystems. Theoretical models and observational studies suggest self-organization, the formation of patterns due to ecological interactions, is critical for enhanced ecosystem resilience. However, experimental tests of this cross-ecosystem theory are lacking. In this study, we experimentally test the hypothesis that self-organized pattern formation improves the persistence of mussel beds (Mytilus edulis) on intertidal flats. In natural beds, mussels generate self-organized patterns at two different spatial scales: regularly spaced clusters of mussels at centimeter scale driven by behavioral aggregation and large-scale, regularly spaced bands at meter scale driven by ecological feedback mechanisms. To test for the relative importance of these two spatial scales of self-organization on mussel bed persistence, we conducted field manipulations in which we factorially constructed small-scale and/or large-scale patterns. Our results revealed that both forms of self-organization enhanced the persistence of the constructed mussel beds in comparison to nonorganized beds. Small-scale, behaviorally driven cluster patterns were found to be crucial for persistence, and thus resistance to wave disturbance, whereas large-scale, self-organized patterns facilitated reformation of small-scale patterns if mussels were dislodged. This study provides experimental evidence that self-organization can be paramount to enhancing ecosystem persistence. We conclude that ecosystems with self-organized spatial patterns are likely to benefit greatly from conservation and restoration actions that use the emergent effects of self-organization to increase ecosystem resistance to disturbance.

Exploring the decline of oyster beds in Atlantic Canada shorelines: potential effects of crab predation on American oysters (Crassostrea virginica)

Atlantic Canada’s American oyster (Crassostrea virginica) beds, while economically and ecologically important, have been in decline over the past few decades. Predation by crabs, in particular by the European green crab (Carcinus maenas), has been proposed as one of the potential causes of such decline. Hence, this study examined oyster mortality levels in multiple beds across Prince Edward Island (PEI) and then experimentally assessed the contribution of green crab predation to oyster mortality. Results from surveys conducted in 10 estuaries across PEI in 2014 indicate that the probability of mortality for small oysters was significantly higher when green crabs were present then in areas without green crabs. This probability of mortality was significantly less when there was the presence of alternative prey like natural mussel beds (Mytilus edulis). The odds of oyster mortality were also higher when beds had rock crabs (Cancer irroratus) compared to beds with no rock crabs. Given the potential importance of green crab predation, its influence was assessed in 2015 using two field experiments with tethered oysters. Our results indicate that odds of small oyster mortality occurring were much higher in green crab inclusion cages than in the open environment and the exclusion cages. These results reaffirm that oysters up to ~40 mm SL are vulnerable to predation, and at least some of the mortality affecting these oysters can be causally attributed to green crab predation. Green crab predation rates upon small oysters are relevant given the economic benefits and ecosystem services provided by these bivalves. They highlight the need for the industry to consider mitigation measures and potentially adapt their oyster growing strategies.

A Numerical Study of Non-hydrostatic Shallow Flows in Open Channels

Abstract The flow field of many practical open channel flow problems, e.g. flow over natural bed forms or hydraulic structures, is characterised by curved streamlines that result in a non-hydrostatic pressure distribution. The essential vertical details of such a flow field need to be accounted for, so as to be able to treat the complex transition between hydrostatic and non-hydrostatic flow regimes. Apparently, the shallow-water equations, which assume a mild longitudinal slope and negligible vertical acceleration, are inappropriate to analyse these types of problems. Besides, most of the current Boussinesq-type models do not consider the effects of turbulence. A novel approach, stemming from the vertical integration of the Reynolds-averaged Navier-Stokes equations, is applied herein to develop a non-hydrostatic model which includes terms accounting for the effective stresses arising from the turbulent characteristics of the flow. The feasibility of the proposed model is examined by simulating flow situations that involve non-hydrostatic pressure and/or nonuniform velocity distributions. The computational results for free-surface and bed pressure profiles exhibit good correlations with experimental data, demonstrating that the present model is capable of simulating the salient features of free-surface flows over sharply-curved overflow structures and rigid-bed dunes.

AVALIAÇÃO DA CAPACIDADE DE SUPORTE DOS BANCOS NATURAIS DE SEMENTES DO MEXILHÃO Perna perna, EM JURUJUBA, NITERÓI - RIO DE JANEIRO

Esse estudo analisou a capacidade de suporte dos bancos naturais utilizados pelos mitilicultores de Jurujuba, município de Niterói, em consonância com a Instrução Normativa n° 105, de 20 jul. de 2006 do IBAMA, que estabelece, entre outras instruções, a retirada de somente 50% do total de sementes dos costões. Para isso, foi calculado a área total dos costões e o peso médio de sementes em 1m². O resultado indica 1.148.560 Kg como o peso total de sementes nos bancos naturais da região. Entretanto, os mitilicultores podem utilizar no máximo 50% desse total, ficando a disposição deles 574.280 Kg de sementes. Calculou-se o total de 20.853 cordas existentes nos Long lines de Jurujuba. Sabendo-se que na criação comercial são colocadas, aproximadamente, 3 Kg sementes para cada corda de 1,5m, um total de 60.949,56 Kg de sementes seria necessário para semear todas as cordas existentes. Porém, ressalta-se a importância de novos estudos, uma vez que este tema ainda não foi avaliado de forma exaustiva, pois existem muitas variáveis envolvidas na avaliação da capacidade de suporte de uma mitilicultura.

New Insights into Pathogenic Vibrios Affecting Bivalves in Hatcheries: Present and Future Prospects.

Hatcheries constitute nowadays the only viable solution to support the husbandry of bivalve molluscs due to the depletion and/or overexploitation of their natural beds. Hatchery activities include the broodstock conditioning and spawning, rearing larvae and spat, and the production of microalgae to feed all stages of the production cycle. However, outbreaks of disease continue to be the main bottleneck for successful larval and spat production, most of them caused by different representatives of the genus Vibrio. Therefore, attention must be paid on preventive and management measures that allow the control of such undesirable bacterial populations. The present review provides an updated picture of the recently characterized Vibrio species associated with disease of bivalve molluscs during early stages of development, including the controversial taxonomic affiliation of some of them and relevant advances in the knowledge of their virulence determinants. The problematic use of antibiotics, as well as its eco-friendly alternatives are also critically discussed.

Flow through a very porous obstacle in a shallow channel.

A theoretical model, informed by numerical simulations based on the shallow water equations, is developed to predict the flow passing through and around a uniform porous obstacle in a shallow channel, where background friction is important. This problem is relevant to a number of practical situations, including flow through aquatic vegetation, the performance of arrays of turbines in tidal channels and hydrodynamic forces on offshore structures. To demonstrate this relevance, the theoretical model is used to (i) reinterpret core flow velocities in existing laboratory-based data for an array of emergent cylinders in shallow water emulating aquatic vegetation and (ii) reassess the optimum arrangement of tidal turbines to generate power in a tidal channel. Comparison with laboratory-based data indicates a maximum obstacle resistance (or minimum porosity) for which the present theoretical model is valid. When the obstacle resistance is above this threshold the shallow water equations do not provide an adequate representation of the flow, and the theoretical model over-predicts the core flow passing through the obstacle. The second application of the model confirms that natural bed resistance increases the power extraction potential for a partial tidal fence in a shallow channel and alters the optimum arrangement of turbines within the fence.