Mudflat Surface Research Articles

Sources of suspended sediments in salt marsh creeks: Field measurements in China and the Netherlands

Marsh creeks are perceived as important conduits for transporting water and sediment between mudflats and marshes. In order to advance the understanding of the transport mechanisms in creeks, the source and ultimate sink of sediment which moves between mudflats and marshes through creek channels need further investigation. Therefore, two field campaigns were conducted in two intertidal systems with varying sediment availability. The water depth, flow velocity, suspended sediment concentration, and bed level change were measured simultaneously in a marsh creek and on the adjacent mudflat in Chongming Island (China) and in Paulina Saltmarsh (the Netherlands). Paulina Saltmarsh is much smaller, more frequently flooded, and has lower sediment concentration than Chongming. These contrasting conditions allow for a comparison of transport mechanisms and functioning of the creek. Both systems first show that the high suspended sediment concentration (SSC) measured in marsh creeks is mainly the consequence of sediment advection rather than local erosion. In addition, erosion in marsh creeks is usually limited during ebb tides, reducing the export of sediment through these creeks. However, differences have been observed between two systems. The measured SSC was highly asymmetric between flood and ebb tides in Chongming. Large peaks in SSC during the flood period can be observed for most tidal cycles. The marsh creeks in Chongming therefore function as conduits for sediment import. Additionally, there are distinct overbank and underbank tides in Chongming. Sediment was trapped and retained in creeks during underbank tides, which can then be eroded and transported to the marsh during subsequent overbank tides. We also observed that mudflats in Chongming quickly recovered after erosion. These mechanisms have not been observed in Paulina Saltmarsh, where net sediment export via the marsh creek was observed due to a lack of abundant sediment in suspension during flood tides. Furthermore, the remaining bed surface of mudflats after an erosion event was stronger than before, limiting further erosion in Paulina Saltmarsh. These findings from the two systems indicate that the role of creeks in sediment import/export depends on the availability of sediment from mudflats, shedding light on nourishment strategies for salt marshes.

Views from 'crabworld': the spatial distribution of light in a tropical mudflat.

Natural scene analysis has been extensively used to understand how the invariant structure of the visual environment may have shaped biological image processing strategies. This paper deals with four crucial, but hitherto largely neglected aspects of natural scenes: (1) the viewpoint of specific animals; (2) the fact that image statistics are not independent of the position within the visual field; (3) the influence of the direction of illumination on luminance, spectral and polarization contrast in a scene; and (4) the biologically relevant information content of natural scenes. To address these issues, I recorded the spatial distribution of light in a tropical mudflat with a spectrographic imager equipped with a polarizing filter in an attempt to describe quantitatively the visual environment of fiddler crabs. The environment viewed by the crabs has a distinct structure. Depending on the position of the sun, the luminance, the spectral composition, and the polarization characteristics of horizontal light distribution are not uniform. This is true for both skylight and for reflections from the mudflat surface. The high-contrast feature of the line of horizon dominates the vertical distribution of light and is a discontinuity in terms of luminance, spectral distribution and of image statistics. On a clear day, skylight intensity increases towards the horizon due to multiple scattering, and its spectral composition increasingly resembles that of sunlight. Sky-substratum contrast is highest at short wavelengths. I discuss the consequences of this extreme example of the topography of vision for extracting biologically relevant information from natural scenes.

The effect of a gait and balance training program on an unstable mudflats surface in older adults: A randomized controlled pilot study.

Balance training on an unstable support surface has been known to improve postural control. The aim of this study was to investigate the effect of a gait and balance training program on an unstable mudflats surface in older adults. A total of 28 older people were assigned to participate in a gait and balance training program on an unstable mudflats surface (experimental group) or on firm ground (control group). All participants received the training program for 55 minutes per session, 2 sessions per day for 5 days. The primary outcomes were the Berg Balance Scale (BBS) and single-leg stance (SLS) test. Secondary outcomes were Timed Up and Go (TUG), 10-meter walk test (10MWT), Modified Falls Efficacy Scale (MFES), Motricity Index (MI) of the lower extremities, and medical research council (MRC) scale of lower extremities. SLS with eyes open and the MRC of the left and right ankles showed a large effect size whereas the MI of the left and right lower extremities and MRC of the left and right knees showed a medium effect size in the experimental group. Intergroup differences in changes from baseline to after the exercise program included a large effect size of the SLS with eye open and MI of the right lower extremity and a medium effect size of the MI of the left lower extremity and MRC of the right ankle and left hip. Muscle strength and balance of older people could be improved with gait and balance training on an unstable mudflat surface.

Mudflat surface sediment type mapping by remote sensing considering the effect of the chlorophyll-a content

Mudflats are critical interfaces between the marine and terrestrial environment of muddy coasts. Mapping mudflat surface sediment types and analyzing their dynamic changes are helpful to understand the variations of sedimentary environments and their responses to tidal current movements. To obtain the surface sediment types of the mudflats, this study first took the chlorophyll-a content as an environmental variable and combined it with satellite spectral reflectance data processed by fractional-order derivative (FOD) to establish a machine learning model for retrieving sediment component content (SCC) of the sand, silt, and clay. Then, the three SCCs were linear equilibrium corrected and inputted into Folk's ternary classification model, and the spatial distribution map of the sediment types was accurately obtained. The results showed that the use of the FODs for satellite image enhancement could provide richer spectral information and improve the accuracy of the chlorophyll-a content and SCCs inversed by the grid search-support vector machine (GS-SVM) model. When compared to direct spectral modeling, considering the effect of the chlorophyll-a content as the key input factor, the coefficients of determination (R2) for the sand, silt, and clay contents inversion were increased by 15.1, 9.2, and 38.2%, and the root mean square error (RMSE) were reduced by 9.7, 5.5, and 2.5%, respectively. Surface sediment type maps obtained from the three SCCs showed that the main sediments in the mudflats on the central coast of Jiangsu Province, China were silty sand and sandy silt. Between 2019 and 2021, the sediment types in 84.46% of the total area were unchanged. For the changing area, the sediment transitioned toward finer-grained types near the seawall of the coastal region. Whereas in the offshore area, especially along the edge of the huge tidal channels, the sediments tended to be coarser because of strong hydrodynamic screening. The findings will be helpful for improving the ability of mudflat sedimentation environmental monitoring and spatial resource management via remote sensing.

Long chain fatty acids analysis of intertidal biofilm by direct injection liquid chromatography time of flight mass spectrometry

The critical importance of mono- and polyunsaturated fatty acids (FAs) in a variety of biological functions, including animal nutrition and as an environmental stress monitor, is well recognized. However, while methods exist for monitoring of fatty acids, few are specific either to the profile of a microphytobenthos matrix or practical in application to multiple, diverse intertidal biofilm sample sets. In the current study, a sensitive liquid chromatography (LC) quadrupole time of flight mass spectrometry (QTOF) method was developed for the quantitative analysis of 31 FAs specific to intertidal biofilm, a thin mucilaginous layer of microalgae, bacteria, and other organisms on the surface of coastal mudflats, which provide a rich source of FAs for migratory birds. Preliminary screening of diverse biofilm samples collected from shorebird feeding grounds highlighted eight saturated (SFA), seven monounsaturated (MUFA), and sixteen polyunsaturated FAs (PUFA) that were selected for analysis. Improved method detection limits in the range 0.3–2.6 ngmL−1 were achieved, excepting for stearic acid at 10.6 ngmL−1. These excellent results were obtained without use of complex sample extraction and clean-up procedures undertaken by other published methods. An alkaline matrix of dilute aqueous ammonium hydroxide with methanol was shown to be selective for extraction and stability of the more hydrophilic fatty acid components. The direct injection method showed excellent precision and accuracy both during validation and application to hundreds of real-world intertidal biofilm samples from the Fraser River estuary (British Columbia, Canada) and other areas of the region frequented by shoreline birds.

A Machine-Learning Approach to Intertidal Mudflat Mapping Combining Multispectral Reflectance and Geomorphology from UAV-Based Monitoring

Remote sensing is a relevant method to map inaccessible areas, such as intertidal mudflats. However, image classification is challenging due to spectral similarity between microphytobenthos and oyster reefs. Because these elements are strongly related to local geomorphic features, including biogenic structures, a new mapping method has been developed to overcome the current obstacles. This method is based on unmanned aerial vehicles (UAV), RGB, and multispectral (four bands: green, red, red-edge, and near-infrared) surveys that combine high spatial resolution (e.g., 5 cm pixel), geomorphic mapping, and machine learning random forest (RF) classification. A mudflat on the Atlantic coast of France (Marennes-Oléron bay) was surveyed based on this method and by using the structure from motion (SfM) photogrammetric approach to produce orthophotographs and digital surface models (DSM). Eight classes of mudflat surface based on indexes, such as NDVI and spectral bands normalised to NIR, were identified either on the whole image (i.e., standard RF classification) or after segmentation into five geomorphic units mapped from DSM (i.e., geomorphic-based RF classification). The classification accuracy was higher with the geomorphic-based RF classification (93.12%) than with the standard RF classification (73.45%), showing the added value of combining topographic and radiometric data to map soft-bottom intertidal areas and the user-friendly potential of this method in applications to other ecosystems, such as wetlands or peatlands.

Occurrence and size distribution of microplastics in mudflat sediments of the Cowichan-Koksilah Estuary, Canada: A baseline for plastic particles contamination in an anthropogenic-influenced estuary

Documenting the prevalence of microplastics in marine-coastal ecosystems serves as a first step towards understanding their impacts and risks presented to higher trophic levels. Estuaries exist at the interface between freshwater and marine systems, and provide habitats for a diverse suite of species, including shellfish, fish, and birds. We provide baseline values for estuarine mudflats using sediment samples collected at Cowichan-Koksilah Estuary in British Columbia, Canada, a biologically-rich estuary. The estuary also contains a marine shipping terminal, forestry log sort area, and input of contaminants from nearby residential and agricultural areas. Microplastics, both fragments and fibers, occurred in 93% (13/14) of sediment samples. A mean of 6.8 microfibers/kg dw (range: 0–12 microfibers/kg dw) and 7.9 microfragments/kg (range: 0–19 fragments/kg dw) occurred in individual samples, and counts of fibers and fragments were strongly correlated (r = 0.78, p = 0.008, n = 14). The abundance of microplastics tended to be higher on the north side of the estuary that receives greater inputs from upland sources relative to the south side. Size distributions of microplastic fragments and fibers were similar to sediment grain size distribution with size categories 0.063 to 0.25 mm and 0.25 to 0.6 mm being the most common for plastics and sediment, indicating the occurrence of microplastics likely followed existing depositional processes within the estuary. Microplastics in sediments were composed of a variety of polymers, including high density polyethylene (HDPE), Nylon 6/6 (polyhexamethylene adipamide), and polyethylene terephthalate-PETE (poly(1,4-cyclohexylene dimethylene terephthalate)). This study indicates that microplastics occur throughout most of the Cowichan-Koksilah Estuary, and future studies should focus on the exposure risk and potential for bioaccumulation for wildlife species that feed on the surface of intertidal mudflats.

Burrow residence of males and females of the mudskipper Periophthalmus modestus during reproduction

Pre-spawning reproductive behavior on the mudflat surface was reported previously for the mudskipper, Periophthalmus modestus , but it remains unknown how a pair spawns and fertilizes eggs within the spawning chamber of a burrow. In this study, we recorded reproductive behaviors from burrow entry of a pair to the departure of a female. In those cases, where spawning was suspected from a drastic reduction in the distension of the female’s belly (N = 4), the female remained inside a burrow for 240-350 min without coming out onto the mudflat surface. In contrast, the male often but irregularly emerged from the burrow. In one case, a second male entered a burrow 169 min after the burrow entry of a female, resulting in her desertion from the burrow without spawning. During burrow cohabitation of the pair, burrow openings were often clogged by mud from inside. After the female left the burrow, the male remained inside the burrow for variable periods. Then, the male guarded the burrow for about one week. Upon termination of the burrow guarding, the male began excavating a new burrow near the previous one or repaired the burrow that he had guarded. A hypothesized scenario is proposed for the reproduction of this species for further investigation.

Mapping the Intertidal Microphytobenthos Gross Primary Production, Part II: Merging Remote Sensing and Physical-Biological Coupled Modeling

Microphytobenthos (MPB) at the sediment surface of intertidal mudflats are known to show a high spatial and temporal variability in response to the biotic and abiotic conditions prevailing at the mud surface. It makes long-term and large-scale monitoring of MPB Gross Primary Production (GPP) difficult to set up. In this study, we developed the first 3D physical-biological coupled model (MARS-3D) that explicitly simulates GPP of intertidal MPB at the mudflat scale, and we compared the outputs with in situ and space remote sensing MPB GPP data. We discuss the sources of discrepancies between the modeling and the remote sensing approach in the light of future developments to be done. For instance, the remote sensing algorithm provides a very synoptic view of the mudflat GPP. It is well-suited to achieve diagnostic estimates of MPB GPP at the synoptic spatial and temporal scale. By contrast, the MARS-3D model provides a more dynamic representation of the MPB activity and prognostic estimates of MPB GPP over the mudflat. It is very relevant to resolve the seasonal and inter-annual dynamics of MPB. Getting comparable GPP estimates derived from the remote sensing algorithm and 3D physical-biological coupled model will further require a better convergence in terms of equations structure, biological constants parameterization, and source data used (i.e., vegetation index vs. chlorophyll a). Setting a common parameterization in both the numerical model and remote sensing algorithm might be challenging in a perspective of mapping MPB PP over large mudflats from a synoptic to inter-annual time scale, but it could open the door to a new way of quantifying MPB GPP over large intertidal mudflats.

Interactive effects of shell hash and predator exclusion on 0-year class recruits of two infaunal intertidal bivalve species in Maine, USA

Biotic and abiotic factors affecting survival and growth of recently settled infaunal bivalves not only determine the strength of 0-year class populations, but the structure and function of benthic soft-bottom communities. At mudflats across north-central Casco Bay, a 517 km2 embayment in the western Gulf of Maine, USA, intertidal sediments are generally acidic (pore water pH range = 7.09–7.85), which can negatively affect settlement and subsequent recruitment success of infaunal bivalves due directly or indirectly to shell dissolution. In addition, predation on bivalves by invasive green crabs, Carcinus maenas, and native consumers is intense in this region. Two commercially important infaunal bivalve species occupy these sediments (softshell clams, Mya arenaria; hard clams, Mercenaria mercenaria). Fisheries managers, legislators, and others have suggested that adding crushed shells of M. arenaria to the surface of mudflats can ameliorate negative effects of acidic sediment pore water through chemical buffering. We investigated the interactive effects of modifying surface sediments using crushed and weathered shells of Mya and predator exclusion on abundance and size of 0-year class individuals of these two bivalve species in large-scale plots (9.3 m2) and small-scale experimental units (EU; 182.4 cm2). Field experiments were conducted over three years (170–204 days yr−1; each initiated prior to spawning and continuing well after settlement had ceased). Shell hash in large-scale plots (mean particle size = 19.3 mm) varied across three levels (0, 0.63, and 1.27 kg m−2), and between 0 and 1.27 kg m−2 in EU where shell size varied from 1.9–19.3 mm. Small-scale experiments also used granite chips that, like crushed shells, increased habitat heterogeneity but did not buffer sediments. Density and size of both bivalve species at the end of most field trials were significantly greater in predator-exclusion treatments vs. controls independent of shell treatment. In all trials, neither Mya nor Mercenaria responded positively to the presence of shell additions. Fisheries managers should focus attention on mitigating effects due to predators instead of spreading shell hash to buffer intertidal sediments.

Morphology of the feeding apparatus in the herbivorous mudskipper, Boleophthalmus pectinirostris (Linnaeus, 1758)

Gaining the ability to feed in terrestrial environment allows fish to exploit novel food resources. However, the difference in physical characteristics between air and water, i.e., much lower density and viscosity of the former, would dictate a change in feeding mechanisms: suction feeding, the dominant feeding mode of aquatic vertebrates, hardly works in the air. There are some extant amphibious fishes that feed on land. However, most published studies have dealt with the feeding mechanisms of carnivorous amphibious fishes that prey on relatively large food items, and little is known about herbivorous fishes grazing on land. In this study, we investigated the morphology of the feeding apparatus of Boleophthalmus pectinirostris, a herbivorous mudskipper, to understand how feeding apparatus is modified for grazing on land. Dentition, and the skeletal and muscular systems of the branchial basket were examined through macroscopic and microscopic dissection, scanning electron microscopy, and micro-computed topography scanning. The results show that the feeding apparatus of the fish has been modified presumably to transport diatom cells from the mudflat surface to the digestive tract with minimum admixture of mud particles. The modifications include horizontal orientation of the lower jaw teeth, horizontally aligned, high-density gill rakers on the third (only on the posterior raw) and fourth (both rows) gill arches, large pharyngeal plates bearing numerous fine teeth, and the musculoskeletal system of the branchial basket.

Effect of Mudflat Trampling on Activity of Intertidal Crabs

Many people visit intertidal mudflats to collect bait and seafood, or for eco-tourism and recreation, and as a consequence trample on the mudflats frequently. Trampling would not be life threatening to most animals in the intertidal flats as they have evolved hiding behavior to escape predation. However, what is the effect of trampling on the behavior of intertidal animals? In this study, the effect of mudflat trampling on the activity of crabs (e.g. fiddler crabs, sentinel crabs) living on the mudflat was explored. The number of crabs active on the mudflat surface in experimental plots (1.5 × 1.5 m2) before and after (10 min. and 30 min.) trampling of three different intensities (Heavy trampling = 60 steps; Moderate trampling = 20 steps; and No trampling) was compared in two different mudflat systems. After trampling, the number of crabs active on the surface decreased and was significantly lower than that of control plots. The more intensively trampled the mudflat was, the fewer crabs were active on the mudflat surface. Surprisingly, the number of active crabs did not recover even 30 min. after trampling. The results clearly support the hypothesis that trampling can severely interfere with the behavior of crabs living on intertidal mudflats.

Hydraulic and Sediment Dynamics at times of Very Shallow Water on Intertidal Mudflats: The Contribution of Waves

ABSTRACT Zhang Q.; Gong Z.; Zhang C.K.; Zhou Z., and Townend I., 2016. Hydraulic and sediment dynamics at times of very shallow water on intertidal mudflats: the contribution of waves. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 507–511. Coconut Creek (Florida), ISSN 0749-0208. Intertidal mudflats are often characterized by a special “very shallow water” environment, with a water depth in the order of 10 cm. High-resolution data including water depth, wave parameters, velocity profiles (within 3–6 cm above the mudflat surface with a vertical resolution as fine as 1 mm), stratified suspended sediment concentration (SSC) and bed deformation over the intertidal mudflat during August 8–10, 2013 were measured using a self-designed measuring system. High-resolution stratified velocities near the bottom under different tide and wave conditions were c...

Velocity and sediment surge: What do we see at times of very shallow water on intertidal mudflats?

A self-designed “bottom boundary layer hydrodynamic and suspended sediment concentration (SSC) measuring system” was built to observe the hydrodynamic and the SSC processes over the intertidal mudflats at the middle part of the Jiangsu coast during August 8–10, 2013. Velocity profiles within 10cm of the mudflat surface were obtained with a vertical resolution as fine as 1mm. An ADCP was used to extend the profile over the full water depth with a resolution of 10cm and the vertical SSC profile was measured at intervals using Optical Backscatter Sensors (OBS). At the same time, water levels and wave conditions were measured with a Tide and Wave Recorder. Measured data suggested that the vertical structure of velocity profiles within 10cm above the bed maintains a logarithmic distribution during the whole tidal cycle except the slack-water periods. Shallow flows during both the early-flood period and the later-ebb period are characterized by a relatively large vertical velocity gradient and a “surge” feature. We conclude that the very shallow water stages are transient and may not contribute much to the whole water and sediment transport, while they can play a significant role in the formation and evolution of micro-topographies on tidal flats.

Target Detection Is Enhanced by Polarization Vision in a Fiddler Crab

We are constantly surprised by the ability of relatively simple animals to perform precise visually guided movements within complex visual scenes, often using eyes with limited resolution. Exceptional examples include the capture of airborne prey by dragonflies, the learning flights of bees and wasps, and the tracking of conspecifics by crabs on intertidal mudflats. Most studies have focused on how animals do this using sensitivity to intensity or color. However, it is increasingly evident that a third ability, polarization vision, may contribute to such tasks. In many insects, polarization-sensitive photoreceptors are confined within an area of the eye known as the dorsal rim, which detects the polarized sky pattern specifically for navigation. However, some animals, including fiddler crabs, are sensitive to the polarization of light across the majority of their image-forming eyes, potentially allowing them to use polarization information to increase perceived contrast for general visual tasks. Investigations into the use of polarization image-parsing by animals have largely been confined to laboratory settings under artificial lighting. This approach can occasionally mislead if the lighting conditions are different from natural. This study presents the first behavioral evidence from the natural context for a function of polarization image parsing. Using experimental manipulations in wild populations of the fiddler crab Uca stenodactylus, we provide evidence that these animals use their polarization vision to enhance contrast in their visual environment, thereby increasing their ability to detect and respond to objects on the mudflat surface.

River flow control on intertidal mudflat sedimentation in the mouth of a macrotidal estuary

The objective of this study is to analyze the impact of hydrological variability influenced by climatic phenomena upon the sedimentary exchange between the turbidity maximum (TM) and a river mouth intertidal mudflat. This study, carried out over a period of 10years (1997–2006) in the Seine Estuary (France), is specifically focused on two extreme periods: a wet one from 2001 to 2002 and a drier one from 2005 to 2006. This study is based on an original approach combining data gathered via low-altitude remote sensing with altimeter readings and ground-level measurements.During this 10year period, we observed a link between climate change and the sedimentary processes on the mudflat surface. The modifications of sedimentary processes are mainly connected to the multiannual variability of hydrological flow rates that control the positioning of the turbidity maximum, the source of the sedimentary material deposited in this intertidal zone. The TM at the mouth of the Seine estuary is well developed; its maximum mass is estimated to be between 300,000tons and 500,000tons (Avoine et al., 1981) with maximum concentrations in the surface waters ranging from 1 to 2g∙l−1 (Le Hir et al., 2001). Most of the fine particles stored within the TM have been found to originate from within the catchment area (Dupont et al., 1994). In the Seine estuary, the dynamics of the estuarine TM, in response to hydrodynamic forcings, have been previously described (Avoine et al., 1981) and modeled (e.g. Brenon and Le Hir, 1999; Le Hir et al., 2001). The TM is upstream of the northern mudflat when the river flow is low (<450m∙s−1) and nearby the study area when the river flow is higher. Thus during wet periods, the sedimentation rates increase by +17cm∙y−1, while during the drier one (when the turbidity maximum is located upstream of the estuary) we observed an erosion rate of 7.6cm∙y−1. Sedimentation events in the mudflat resulting from spring tides are less frequent during dry periods, and they deposit a smaller quantity of sediment (−23% of total deposition mass per event). Because of the lower flow rates coupled with the impacts of local development, the flood tides have become dominant. This contributes to the addition of sandy or silty sediments on the mudflat, of which the slope has increased 450% over 8years caused by erosion.

Roles of air stored in burrows of the mudskipper Boleophthalmus pectinirostris for adult respiration and embryonic development

Air was stored in 90% of Boleophthalmus pectinirostris burrows in summer breeding months when fish were active on the mudflat surface during low tide but only in 50% of burrows in overwintering months when the fish confined themselves to burrows. The volume of gas recovered from the burrows ranged from 30 to > 400 ml. The partial pressure of oxygen (PO₂) of the gas varied from 5 to 20 kPa and was inversely related to the partial pressure of carbon dioxide (PCO₂) in all but the wintering periods. Sampling in July demonstrated that gas was stored in both male and female burrows with no difference in volume, PO₂ or PCO₂ between them. Adult fish were able to survive total submersion in hypoxic (PO₂ = 1.96 kPa) water for 8 h, but no embryos survived to hatch in the hypoxic aquatic environment. Thus, the deposited air appears to be a crucial source of oxygen for the embryos developing in the egg chamber of the burrow, but may play only a subsidiary role for adult respiration during presumed high-tide confinement.

盐城淤泥质潮滩湿地潮沟发育及其对米草扩张的影响

Wetland ecosystems are landscapes of the highest biodiversity in nature and one of the most important environmental resources for human welfares. Their important ecosystem functions sometimes are regarded as "the earth' s filtration system". Yancheng coastal wetland now remains a typical mudflat by frequent tidal reaction. A more complex, changing creek system is formed by the mudflat development with a process of tidal movement. The creek system as a typical geomorphologic factor has formed at mudflat and become a pivotal pathway to continuously exchange matter,energy and information within and outside of the system. It is also important for distribution of the tidal water and sediment supply. And creek system development has a direct impact on the wetland ecologically environmental change and spatial distribution of vegetation. Therefore it has become an important indicator for the evolution of the mudflat. Spartina is a salt,flooded tolerant and perennial plant growing in a vast intertidal zone. It is growing at low tide with well-developed root system,and it could strongly intercept sediment. Accompanied with the formation of Spartina,hydrodynamic force and sediment transport conditions change in its mudflat surface, caused by changes of tidal flat sedimentary characteristics and topography,thereby affecting the development of trenches. And Spartina tidal trenches are specially established. Yancheng coastal wetland was chosen as the study area. Based on the remote sensing images of 1996—2012,using GIS techniques and field survey,we extract tidal creek system in this study. And a 16-year trend was analyzed on the mutual relations of Spartina expansion and tidal creek system development between 1996 and 2012 of Yancheng coastal wetland. Research results show that: Under the control of the tidal and terrain,no large-scale distribution of trenches present in this study area. The size of the trenches gradually increased from north to south. Their elevation is 0—1. 8m. Distinct morphology exists in salt marsh and bare mudflat. Trenches covered by Spartina indicate a unique feature,which present narrow and deep; Trenches are very dense with covering of 1539m / km2; They reach up to 4—5 grades; And lateral movement is less than longitudinal. The trenches are wide and deep,the main trenches are generally about 17m and branches between 3— 9m. The trenches are becoming deep at low grade; both sides of the edges of the trenches often development in asymmetry coastal embankment with ranging different height. The edges of the salt marsh have developed scarps and gullies with stretches throughout the Spartina zone. Inside the salt marsh,tidal creek development leads to Spartina inland expansion, expansion of the width and amplitude largely depends on the density and size of the tidal creek areas; Outside of the salt marsh,creeks activity in bare tidal will slow down with the reduction of the rate of expansion of Spartina. The wetlands microrelief variation has been further understand with this study. The baseline information greatly supports the Yancheng coastal wetlands and management,and benefits regional social and economic development in an effective manner.

Mangrove ecofarming in Guangxi Province China: an innovative approach to sustainable mangrove use

Following 7 years of field trials conducted in the mangrove areas of Guangxi Province, China, between 2007 and 2012, a mariculture system has been developed that greatly enhances natural productivity. This system is based on the installation of underground tubes and has resulted in annual mean production values of between 27 000, and 45 000 US$ per hectare11Currency exchange rate: 1 USD = 6.35 China Yuan. per annum without requiring cutting or conversion of mangrove vegetation. This article provides details of the system, its construction, operation, economics and production.Consisting of a network of underground tubes, erect pipes and management chambers, this system is based on enhancing the spatial heterogeneity of the benthic environment by burying plastic pipes in the mangrove soils, thus providing refuges for economically important fish with minimal disturbance to the mangrove root system. Landward shrimp ponds can be used as reservoirs to oxygenate the water in the system during low tide. Molluscs are raised on mudflat surfaces within the habitat. The ecofarming site is accessed by boardwalks that also facilitate ecotourism and public education. This ecofarming system is environmentally friendly because no enclosures are constructed and there is no industrial feed input. The bulk of the system is buried within the mangrove soils consequently it is resistant to storm and tidal surges, is easy to control and has low management cost, whilst the products are of high quality and have high recapture rates. To date, ten indigenous species have been tested, and five of them have been successfully raised and harvested. The underground tube ecofarming system is unique and not derived from any similar system currently in operation elsewhere in mangrove ecosystems.22An application for a Chinese patent on the system was granted in September 2012.

Comparative Feeding on Chlorophyll-Rich Versus Remaining Organic Matter in Bivalve Shellfish

Filter feeding was compared in the blue mussel Mytilus edulis, Mediterranean mussel Mytilus galloprovincialis, Pacific oyster Crassostrea gigas, Chinese pleated oyster Crassostrea plicatula, Chinese scallop Chlamys farreri,Manila clam Tapes phillipinarum, razor clam Sinonvacula constricta, and blood cockle Tegillarca granosa over 95 dietary conditions across nine locations in Europe and China. Conditions included natural seawater enhanced, on occasion, with variable additions of microalgal monoculture and/or natural silt collected from the surface of nearby mudflats, thereby ensuring that diets ranged from oligotrophic to hypereutrophic (>325 µg chlorophyll a/L) and highly turbid (>1,250 mg total particulate matter/L). Building on past insights into differential particle processing, we resolved the availability, filtration, and ingestion of organic matter rich in chlorophyll a, and which matter is known to be ingested selectively, from all remaining organics, such as detritus, bacteria, protozoans, and/or colloids. The forms of fitted relations that best described feeding responses were different for chlorophyll-rich versus remaining organics, that difference being consistent in all eight bivalve species, including when measured in the same species across different locations. Throughout, positive linear relations between net ingestion of chlorophyll-rich organic matter and the availability of that chlorophyll-rich organic matter indicated that each species ingested constant proportions of the organics associated with chlorophyll a, with no limitation evident to such ingestion over our experimental range. Alternatively, ingestion of the remaining organics by each species increased as saturating functions of the availability of those remaining organics alone. Differences were evident between species both in the proportions of available chlorophyll-rich organic matter that were ingested and in saturated ingestion rates for the remaining organics. Comparison of those differences suggests an evolutionary trade-off among species between their relative abilities to process chlorophyll-rich versus remaining organics. Differences also suggest congeneric adaptation to natural habitat, impressing a need for careful appraisal of each and every bivalve species. Significant costs of particle sorting, digestion, and absorption, evidenced as metabolically derived material egested and assayed within feces, were greatest in species with higher saturated capacities for the ingestion of remaining organics. Last, we describe how, compared with predictions based on chlorophyll a or total particulate organic matter alone, our approach resolving coincident differential availabilities and processing of chlorophyll-rich versus remaining organic matter has improved the accuracy of growth simulations when applying single calibrations of the generic shellfish model ShellSIM across coastal habitats that contrast in seston composition.