Changes Of Hydrological Environment And Their Influences On Coastal Wetlands InThe Southern Laizhou Bay, China

The structure and function of the coastal wetland ecosystem in the southern Laizhou Bay have been changed greatly and influenced by regional hydrological changes. The coastal wetlands have degraded significantly during the latest 30 years due to successive drought, decreasing of runoff, pollution, underground saline water intrusion, and aggravating marine disasters such as storm tides and sea level rising. Most archaic lakes have vanished, while artificial wetlands have been extending since natural coastal wetlands replaced by salt areas and ponds of shrimps and crabs. The pollution of sediments in inter-tidal wetlands and the pollution of water quality in sub-tidal wetlands are getting worse and therefore “red tides” happen more often than before. The biodiversity in the study area has been decreased. Further studies are still needed to protect the degraded coastal wetlands in the area.     

Wetland loss under the impact of agricultural development in the Sanjiang Plain, NE China

Wetland loss has been the major environmental problem in Sanjiang Plain, NE China in recent years because of the dramatic agricultural development. We determined the spatial associations of the wetland loss rates in an 11,000-km² study area for two intervals of period 1 (1975–1989) and period 2 (1989–2004) spanning 30 years by using geographic information systems. The landscape of this area was simple with five categories, composed of ten types, and including three natural wetland types—open water, marsh, and wet meadow. Extensive agriculture was the principal cultivation form in terms of large size farm units in the area. Agriculture has become the principal land use category replacing natural wetlands over the 30-year period. It has changed the whole landscape of the region and the landscape pattern, causing wetland loss and fragmentation. The wetland loss rate of the area was very different between the two intervals, while wetland loss was not uniform throughout the region and was influenced by the landscape characteristics, such as topography, geomorphology, and the location of the wetlands in the watershed. Despite the remarkable land use changes, the wetlands distribution in the landscapes was similar compared to their original pattern. These results indicated that agricultural development affected the areas more than the distribution pattern of the wetlands in this region.     

Assessing the zooplankton community and environmental factors in a Mediterranean wetland

Mediterranean wetlands represent unique repositories of biodiversity, but these ecosystems are increasingly threatened by human-induced habitat loss. Seventy percent of Greek wetlands (ponds, mires, marshes, etc.) have been lost in the past 80 years due to human intervention. In Greece habitat types of mires, listed in Directive 92/43/EEC, have been recorded in a few locations, one of the most important is Kalodiki wetland. Eutrophication key elements were determined at four sampling stations throughout 1 year in order to monitor the trophic conditions. Moreover, the zooplankton community was described as biological element relevant in the assessment of the ecological status of Kalodiki wetland. Kalodiki wetland exhibits nutrient concentrations corresponding to eutrophic conditions while according to chlorophyll-a values it is classified between mesotrophic and eutrophic status depending mostly on the sampling period. As concerning zooplankton community, it appears poor in species and dominated by small-sized organisms, which is generally typical of eutrophic, disturbed systems. Differences among zooplankton assemblages over seasons as well as among sampling sites highlight the role of both abiotic and biotic factors.     

Mapping and quantifying habitat fragmentation in small coastal areas: a case study of three protected wetlands in Apulia (Italy)

In the Mediterranean Region, habitat loss and fragmentation severely affect coastal wetlands, due to the rapid expansion of anthropogenic activities that has occurred in the last decades. Landscape metrics are commonly used to define landscape patterns and to evaluate fragmentation processes. This investigation focuses on the performance of a set of landscape pattern indices within landscapes characterized by coastal environments and extent below 1,000 ha. The aim is to assess the degree of habitat fragmentation for the monitoring of protected areas and to learn whether values of landscape metrics can characterize fine-resolution landscape patterns. The study areas are three coastal wetlands belonging to the Natura 2000 network and sited on the Adriatic side of Apulia (Southern Italy). The Habitat Maps were derived from the Vegetation Maps generated integrating phytosociological relevés and Earth Observation data. In the three sites, a total of 16 habitat types were detected. A selected set of landscape metrics was applied in order to investigate their performance in assessing fragmentation and spatial patterns of habitats. The final results showed that the most significant landscape patterns are related to highly specialized habitat types closely linked to coastal environments. In interpreting the landscape patterns of these highly specialized habitats, some specific ecological factors were taken into account. The shape indices were the most useful in assessing the degree of fragmentation of habitat types that usually have elongated morphology along the shoreline or the coastal lagoons. In all the cases, to be meaningful, data obtained from the application of the selected indices were jointly assessed, especially at the class level.     

Characterizing wetland change at landscape scale in Jiangsu Province, China

Human activities produced great impacts on wetlands worldwide. Taking Jiangsu Province, China, as a representative wetland region subject to extensive human activities, the aim of this study is to understand the conversion trajectory and spatial differentiation in wetland change from a multi-scale perspective. Based on multi-temporal Landsat images, it was found that the natural wetlands decreased by 11.2% from 1990 to 2006 in Jiangsu Province. Transition matrices showed that the conversion of natural wetlands to human-made wetlands (mostly aquaculture ponds) was the major form of natural wetland reduction, accounting for over 60% of the reduction. Percentage reduction and area reduc tion of natural wetlands were respectively quantified within different wetland cover zones using a moving window analysis. Average percentage reduction showed a decreasing tendency with increasing wetland cover. The high-cover and mid-cover zone presented the largest area reduction at the scales of 1-2 km and 4-8 km, respectively. Local hotspots of natural wetland reduction were mapped using the equal-interval and quantile classification schemes. The hotspots were mostly concentrated in the Lixiahe marshes and the coastal wetland areas. For the area reduction hotspots, the quantile classification presented larger area and more patches than the equal-interval classification; while an opposite result was shown for the percentage reduction hotspots. With respect to the discontinuous distribution of the natural wetlands, area reduction could be more appropriate to represent reduction hotspots than percentage reduction in the study area. These findings could have useful implications to wetland conservation.     

Using two classification schemes to develop vegetation indices of biological integrity for wetlands in West Virginia, USA

Bioassessment methods for wetlands, and other bodies of water, have been developed worldwide to measure and quantify changes in “biological integrity.” These assessments are based on a classification system, meant to ensure appropriate comparisons between wetland types. Using a local site-specific disturbance gradient, we built vegetation indices of biological integrity (Veg-IBIs) based on two commonly used wetland classification systems in the USA: One based on vegetative structure and the other based on a wetland’s position in a landscape and sources of water. The resulting class-specific Veg-IBIs were comprised of 1–5 metrics that varied in their sensitivity to the disturbance gradient (R ²?=?0.14???0.65). Moreover, the sensitivity to the disturbance gradient increased as metrics from each of the two classification schemes were combined (added). Using this information to monitor natural and created wetlands will help natural resource managers track changes in biological integrity of wetlands in response to anthropogenic disturbance and allows the use of vegetative communities to set ecological performance standards for mitigation banks.     

Ecosystem evaluation (1989–2012) of Ramsar wetland Deepor Beel using satellite-derived indices

The unprecedented urban growth especially in developing countries has laid immense pressure on wetlands, finally threatening their existence altogether. A long-term monitoring of wetland ecosystems is the basis of planning conservation measures for a sustainable development. Deepor Beel, a Ramsar wetland and major storm water basin of the River Brahmaputra in the northeastern region of India, needs particular attention due to its constant degradation over the past decades. A rule-based classification algorithm was developed using Landsat (2011)-derived indices, namely Normalised Difference Water Index (NDWI), Modified Normalised Difference Water Index (MNDWI), Normalised Difference Pond Index (NDPI), Normalised Difference Vegetation Index (NDVI) and field data as ancillary information. Field data, ALOS AVNIR and Google Earth images were used for accuracy assessment. A fuzzy accuracy assessment of the classified data sets showed an overall accuracy of 82 % for MAX criteria and 90 % for RIGHT criteria. The rules were used to classify major wetland cover types during low water season (January) in 1989, 2001 and 2012. The statistical analysis of the classified wetland showed heavy manifestation in aquatic vegetation and other features indicating severe eutrophication over the past 23 years. This degradation was closely related to major contributing anthropogenic factors, such as a railway line construction, growing croplands, waste disposal and illegal human settlements in the wetland catchment. In addition, the landscape development index (LDI) indicated a rapid increase in the impact of the surrounding land use on the wetland from 1989 to 2012. The techniques and results from this study may prove useful for top-down landscape analyses of this and other freshwater wetlands.     

Levels of polycyclic aromatic hydrocarbons and dibenzothiophenes in wetland sediments and aquatic insects in the oil sands area of Northeastern Alberta, Canada

An immense volume of tailings and tailings water is accumulating in tailings ponds located on mine leases in the oil sands area of Alberta, Canada. Oil sands mining companies have proposed to use tailings- and tailings water-amended lakes and wetlands as part of their mine remediation plans. Polycyclic aromatic hydrocarbons (PAHs) are substances of concern in oil sands tailings and tailings water. In this study, we determined concentrations of PAHs in sediments, insect larvae and adult insects collected in or adjacent to three groups of wetlands: experimental wetlands to which tailings or tailings water had been purposely added, oil sands wetlands that were located on the mine leases but which had not been experimentally manipulated and reference wetlands located near the mine leases. Alkylated PAHs dominated the PAH profile in all types of samples in the three categories of wetlands. Median and maximum PAH concentrations, especially alkylated PAH concentrations, tended to be higher in sediments and insect larvae in experimental wetlands than in the other types of wetlands. Such was not the case for adult insects, which contained higher than expected levels of PAHs in the three types of ponds. Overlap in PAH concentrations in larvae among pond types suggests that any increase in PAH levels resulting from the addition of tailings and tailings water to wetlands would be modest. Biota-sediment accumulation factors were higher for alkylated PAHs than for their parent counterparts and were lower in experimental wetlands than in oil sands and reference wetlands. Research is needed to examine factors that affect the bioavailability of PAHs in oil sands tailings- or tailings water-amended wetlands.     

Application of a three-tier framework to assess ecological condition of Gulf of Mexico coastal wetlands

A multi-level coastal wetland assessment strategy was applied to wetlands in the northern Gulf of Mexico (GOM) to evaluate the feasibility of this approach for a broad national scale wetland condition assessment (US Environmental Protection Agency’s National Wetlands Condition Assessment). Landscape-scale assessment indicators (tier 1) were developed and applied at the sub-watershed (12-digit hydrologic unit code (HUC)) level within the GOM coastal wetland sample frame with scores calculated using land-use maps and geographic information system. Rapid assessment protocols (tier 2), using a combination of data analysis and field work, evaluated metrics associated with landscape context, hydrology, physical structure, and biological structure. Intensive site monitoring (tier 3) included measures of soil chemistry and composition, water column and pore-water chemistry, and dominant macrophyte community composition and tissue chemistry. Relationships within and among assessment levels were evaluated using multivariate analyses with few significant correlations found. More detailed measures of hydrology, soils, and macrophyte species composition from sites across a known condition gradient, in conjunction with validation of standardized rapid assessment method, may be necessary to fully characterize coastal wetlands across the region.     

An integrated approach to assess broad-scale condition of coastal wetlands—the Gulf of Mexico Coastal Wetlands pilot survey

The Environmental Protection Agency (EPA) and U.S. Geological Survey (USGS) initiated a two-year regional pilot survey in 2007 to develop, test, and validate tools and approaches to assess the condition of northern Gulf of Mexico (GOM) coastal wetlands. Sampling sites were selected from estuarine and palustrine wetland areas with herbaceous, forested, and shrub/scrub habitats delineated by the US Fish and Wildlife Service National Wetlands Inventory Status and Trends (NWI S&T) program and contained within northern GOM coastal watersheds. A multi-level, stepwise, iterative survey approach is being applied to multiple wetland classes at 100 probabilistically-selected coastal wetlands sites. Tier 1 provides information at the landscape scale about habitat inventory, land use, and environmental stressors associated with the watershed in which each wetland site is located. Tier 2, a rapid assessment conducted through a combination of office and field work, is based on best professional judgment and on-site evidence. Tier 3, an intensive site assessment, involves on-site collection of vegetation, water, and sediment samples to establish an integrated understanding of current wetland condition and validate methods and findings from Tiers 1 and 2. The results from this survey, along with other similar regional pilots from the Mid-Atlantic, West Coast, and Great Lakes Regions will contribute to a design and implementation approach for the National Wetlands Condition Assessment to be conducted by EPA’s Office of Water in 2011.     

Development and validation of a macroinvertebrate index of biotic integrity (IBI) for assessing urban impacts to Northern California freshwater wetlands

Despite California policies requiring assessment of ambient wetland condition and compensatory wetland mitigations, no intensive monitoring tools have been developed to evaluate freshwater wetlands within the state. Therefore, we developed standardized, wadeable field methods to sample macroinvertebrate communities and evaluated 40 wetlands across Northern California to develop a macroinvertebrate index of biotic integrity (IBI). A priori reference sites were selected with minimal urban impacts, representing a best-attainable condition. We screened 56 macroinvertebrate metrics for inclusion in the IBI based on responsiveness to percent urbanization. Eight final metrics were selected for inclusion in the IBI: percent three dominant taxa; scraper richness; percent Ephemeroptera, Odonata, and Trichoptera (EOT); EOT richness; percent Tanypodinae/Chironomidae; Oligochaeta richness; percent Coleoptera; and predator richness. The IBI (potential range 0–100) demonstrated significant discriminatory power between the reference (mean = 69) and impacted wetlands (mean = 28). It also declined with increasing percent urbanization (R ² = 0.53, p < 0.005) among wetlands in an independent validation dataset (n = 14). The IBI was robust in showing no significant bias with environmental gradients. This IBI is a functional tool to determine the ecological condition at urban (stormwater and flood control ponds), as well as rural freshwater wetlands (stockponds, seasonal wetlands, and natural ponds). Biological differences between perennial and non-perennial wetlands suggest that developing separate indicators for these wetland types may improve applicability, although the existing data set was not sufficient for exploring this option.     

Using dual classifications in the development of avian wetland indices of biological integrity for wetlands in West Virginia, USA

Considerable resources are being used to develop and implement bioassessment methods for wetlands to ensure that “biological integrity” is maintained under the United States Clean Water Act. Previous research has demonstrated that avian composition is susceptible to human impairments at multiple spatial scales. Using a site-specific disturbance gradient, we built avian wetland indices of biological integrity (AW-IBI) specific to two wetland classification schemes, one based on vegetative structure and the other based on the wetland’s position in the landscape and sources of water. The resulting class-specific AW-IBI was comprised of one to four metrics that varied in their sensitivity to the disturbance gradient. Some of these metrics were specific to only one of the classification schemes, whereas others could discriminate varying levels of disturbance regardless of classification scheme. Overall, all of the derived biological indices specific to the vegetative structure-based classes of wetlands had a significant relation with the disturbance gradient; however, the biological index derived for floodplain wetlands exhibited a more consistent response to a local disturbance gradient. We suspect that the consistency of this response is due to the inherent nature of the connectivity of available habitat in floodplain wetlands.     

An Analytical Solution to Model Aquaculture Wetlands Subject to Intermittent Loading and Variable Initial Concentrations

Constructed wetlands are increasingly being used to treat intermittent releases of wastewaters from aquaculture ponds. Most constructed wetland design protocols are based on steady-state releases and as such are incapable of characterizing transient pollutant distribution arising from intermittent releases. Given the seasonal nature of aquaculture operations, the constructed wetland has to be developed using water from other nearby sources (termed as fill water in this study). In some instances, the pollutant concentrations in the fill water are noted to be greater than that measured in the aquaculture ponds. Also, the pollutants in the wetland may exhibit spatial variability due to geochemical interactions with wetland soils. These effects cannot be captured with existing steady-state design schemes. A mathematical model based on the tanks-in-series conceptualization is developed to overcome the aforementioned limitations. An analytical solution for multiple intermittent releases and spatially varying initial concentrations is obtained using Laplace transform and superposition techniques. The utility of the developed model is illustrated using an example based after a constructed wetland at the Loma Alta Shrimp Aquaculture Facility (LASAF) in South Texas. The developed model captures the extremely nonlinear relationship between the maximum discharge concentration and the hydraulic residence time. For the conditions assumed in this study, the extent of mixing is not of major concern when the spacing between the loadings is greater than 0.75 times the hydraulic residence time (HRT). Model results also suggest that the wetland should be oriented in a manner such that the internal geochemical production of the pollutant, if any, is near the inlet.     

2016—2018年北京城市湿地遥感监测分析

为全面了解北京城市湿地的现状及近年来的动态变化情况，利用高分辨率卫星遥感数据，综合运用GIS技术与景观生态学方法，定量分析了北京市6环内的湿地空间格局。结果表明，北京6环内城市湿地以河流湿地和湖库湿地为主；2016—2018年间湿地面积有所下降，2年间减少了126.58 hm²，主要转化为草地，少量转化为建设用地和林地；由于城市外围的开发建设强度较大，5-6环湿地被侵占面积相对较大，而4环内湿地面积的波动较小；2016—2018年，北京城市湿地的斑块密度增加，平均斑块面积有所减小，表明湿地斑块随时间变化呈破碎化的趋势，且从城市中心向城市边缘，湿地斑块的破碎化程度增强。     

The areal extent of brown shrimp habitat suitability in Mobile Bay, Alabama, USA: targeting vegetated habitat restoration

The availability of wetlands and shallow water habitats significantly influences Gulf of Mexico (GOM) penaeid shrimp fishery productivity. However, the GOM region has the highest rate of wetland loss in the USA. Protection and management of these vital GOM habitats are critical to sustainable shrimp fisheries. Brown shrimp (Farfantepenaeus aztecus) are a major component of GOM fisheries. We present an approach for estimating the areal extent of suitable habitat for post-larval and juvenile brown shrimp in Mobile Bay, Alabama, using an existing habitat suitability index model for the northern GOM calculated from probabilistic survey of water quality and sediment data, land cover data, and submerged aquatic vegetation coverages. This estuarine scale approach is intended to support targeted protection and restoration of these habitats. These analyses indicate that approximately 60% of the area of Mobile Bay is categorized as suitable to near optimal for post-larval and juvenile shrimp and 38% of the area is marginally to minimally suitable. We identify potential units within Mobile Bay for targeted restoration to improve habitat suitability.     

Characteristics of nutrients in natural wetland in winter: a case study

The transformation, composition, and distribution characteristics of nutrients in natural wetlands are significantly affected by human activities, such as large-scale water conservancy projects and agricultural activities. It is necessary to reveal the composing and distribution characteristics of nutrients for elucidating its complex removal and retention mechanisms in natural wetlands. In this study, the composition and the spatial distribution characteristics of nitrogen in a natural wetland in central China were illustrated and analyzed. The self-organizing map (SOM) model was used in this study to assess the water quality dataset of the wetland. The relationships between nitrogen and other water quality parameters were revealed by the visualization function of the SOM model with the pre-processed data; the modeling result was in agreement with the linear correlation analysis. The results indicated that the SOM model was suitable for the assessment of field-scale date of natural wetlands, and finally a potential approach for predicting the nutrients concentrations in natural wetlands was also found.     

Land cover changes on the coastal zone of Candarli Bay, Turkey using remotely sensed data

Land cover of the Earth is changing dramatically because of human activities. Information about changes is useful for management of natural resources. Rapid land cover changes have taken place in many coastal areas of Turkey over the last two decades due to urbanization and land degradation. In this paper, land cover change dynamics were investigated by the combined use of satellite remote sensing and geographical information systems. The main objective of the study was to determine land-cover transition rates among land cover types in coastal areas of Turkey. A time series of Landsat TM and ASTER images were used to gather land cover change data of the coastal line of Candarli Bay, Izmir, Turkey. The images were classified using supervised classification and a post-classification comparison approach was used in change detection. The results show significant increase in urban areas but decrease in semi natural and agricultural areas.     

Driving Forces for the Marsh Wetland Degradation in the Honghe National Nature Reserve in Sanjiang Plain, Northeast China

In the study, we analyze and assess quantitatively the spatial pattern of vegetation and its ecological degradation information in the Honghe National Nature Reserve (HNNR), a Ramsar-designated site in Northeast China. Statistics from historical survey data are used to measure the degradation of marshes over time and changes in the hydrological regime. Long-term statistical data are also employed to analyze both natural and human impacts on these changes. Both the wetland degradation model and its mechanisms are discussed in this paper. The research finds that the loss of water and other types of degradation in the vegetation habitat caused by the rapid deterioration of the hydrological regime has threatened the status of HNNR as a “storage area of natural genes.” Scientifically constructed strategies are urgently required to ensure sustainable economic benefits that do not adversely affect this nature reserve.     

Contamination assessment of arsenic and heavy metals in a typical abandoned estuary wetland—a case study of the Yellow River Delta Natural Reserve

Coastal and estuarine areas are often polluted by heavy metals that result from industrial production and agricultural activities. In this study, we investigated the concentration trait and vertical pattern of trace elements, such as As, Cd, Ni, Zn, Pb, Cu, and Cr, and the relationship between those trace elements and the soil properties in coastal wetlands using 28 profiles that were surveyed across the Diaokouhe Nature Reserve (DKHNR). The goal of this study is to investigate profile distribution characteristics of heavy metals in different wetland types and their variations with the soil depth to assess heavy metal pollution using pollution indices and to identify the pollution sources using multivariate analysis and sediment quality guidelines. Principal component analysis, cluster analysis, and pollution level indices were applied to evaluate the contamination conditions due to wetland degradation. The findings indicated that the concentration of trace elements decreased with the soil depth, while Cd increases with soil depth. The As concentrations in reed swamps and Suaeda heteroptera surface layers were slightly higher than those in other land use types. All six heavy metals, i.e., Ni, Cu, As, Zn, Cr, and Pb, were strongly associated with PC1 (positive loading) and could reflect the contribution of natural geological sources of metals into the coastal sediments. PC2 is highly associated with Cd and could represent anthropogenic sources of metal pollution. Most of the heavy metals exhibited significant positive correlations with total concentrations; however, no significant correlations were observed between them and the soil salt and soil organic carbon. Soil organic carbon exhibited a positive linear relationship with Cu, Pb, and Zn in the first soil layer (0–20 cm); As, Cr, Cu, Ni, Pb, and Zn in the second layer (20–40 cm); and As, Cr, Cu, Ni, Pb, and Zn in the third layer (40–60 cm). Soil organic carbon exhibited only a negative correlation with Cd (P?I _geo values), which averaged less than 0 in the three soil layers, this finding indicates that the soils have remained unpolluted by these heavy metals. The mean concentrations of these trace elements were lower than Class I criteria. The degradation wetland restoration suggestions have also been provided in such a way as to restore the reserved flow path of the Yellow River. The results that are associated with trace element contamination would be helpful in providing scientific directions to restore wetlands across the world.     

Monitoring water quality of Coimbatore wetlands, Tamil Nadu, India

Signs of wetland-water quality degradation have been apparent for decades, especially in those wetlands situated in the vicinity of cities and human habitations. Investigation on four urban wetlands of Coimbatore have been undertaken to assess the water quality with reference to pollution from various sources. The pH and total dissolved solids (TDS) values of the lakes were found to be different from those reported almost a decade back. The concentrations of phosphate and sulphate were much lower than the earlier reported values. The present scenario states that though the biochemical oxygen demand and chemical oxygen demand values were lower for the Ukkadam wetland, the values for Perur wetland have shown a gradual increase. Alkalinity and chloride concentrations were thrice higher than the previous findings. Electrical conductivity and TDS ranged from 303.67 to 4,456.7 μS/cm and from 169 to 2,079.3 mg/l, respectively, and were positively correlated with chloride and sulphate (P?< 0.05). These changes are a reflection of the environmental changes happening in the cityscape of the Coimbatore, a fast-growing city in south India.