Investigation of calcareous beach sands in the Akumal and Tulum areas for use in constructed wetlands,Eastern Yucatan Peninsula

Constructed wetlands can be a low-cost, ecologically based technology to locally treat domestic wastewater prior to discharge. Wetland systems implemented in the resort village of Akumal in the state of Quintana Roo, in the Yucatan Peninsula of Mexico have been considered moderately successful over approximately 10 years of operation. Yet the wide-scale implementation of constructed wetlands has not occurred in the region nor throughout Mexico due largely to the cost of the crushed aggregate used in these systems. Variation in the geotechnical and mineralogical properties of 29 samples of local calcareous beach sands collected from the tourist areas of Akumal and Tulum in the Yucatan, Mexico were analyzed and compared to those of crushed aggregate currently used in constructed wetland systems in Akumal. Powder X-ray diffraction on beach sand samples from Akumal and Tulum indicates that the proportion of aragonite varies from 24 to 84%, calcite varies from 7 to 38% and Mg-calcite varied from 8 to 57% compared to crushed aggregate which consists of 0–25% aragonite and 75–100% calcite. Compared to crushed aggregate beach sands are unimodal and have better uniformity coefficients, making them a better geotechnical choice than crushed sands with respect to these properties. Grain-size of the beach sands is much smaller compared to that of the crushed aggregate currently used in the constructed wetland systems in Akumal which should enhance the efficiency of the filtration of organic matter and bacteria. The average hydraulic conductivity measurements of 0.010 and 0.016 cm/s for beach sands from Akumal and Tulum, respectively are comparable or less than the average of 0.016 cm/s for crushed aggregate currently used in engineered wetland systems. Yet a combination of high bulk porosity, intragranular pores, and the presence of Mg-calcite observed in beach sands may likely result in higher dissolution rates versus the crushed aggregate. Preliminary assessment suggests that the use of local sand may be a technical, economic, and perceptual enhancement to the systems. Still a careful and thorough analysis of the potential environmental and aesthetic impacts of mining beach sands is necessary.     

Geoheritage values of consanguineous wetland suites on the Swan Coastal Plain,Western Australia

A wide range of wetland types occur on the Swan Coastal Plain of Western Australia. They vary from basins, and flats, to slopes and channels, and vary in size, shape, water characteristics, sediment types, stratigraphy, vegetation, origin, and maintenance processes. The wetlands range from large linear lakes to small round or irregular seasonally damp wetland basins to seasonally flooded flats, to seasonally flooded or permanently flowing channels. Salinity ranges from fresh to saline to hyposaline; and recharge mechanisms from perching of surface-water to wetting and inundation by groundwater, as determined by regional features such as geology, geomorphology, soils, climate and hydrology, and local physical/chemical processes. The Swan Coastal Plain presents a bewildering array, diversity, and complexity of wetlands, but patterns and ordering can be recognised if the wetlands are aggregated into natural groups. The wetlands, in fact, have been aggregated into natural groupings termed ‘consanguineous suites’, resulting in some 30 different formally named wetland suites related to geomorphic setting varying, for instance, from interdune depressions on a beach-ridge plain (the Becher Suite), to karst-formed linear lakes in limestone-ridge country (the Yanchep Suite), to irregular to round, semi-interconnected basins on a quartz sand subdued dune system (the Jandakot Suite), to linear and round basins formed along the hydrological contact between limestone and quartz sand (the Bibra Suite), among others. The variety of wetland types on the Swan Coastal Plain represents geodiversity that needs to be addressed in geoheritage assessments of the State of Western Australia. Further, as repositories of Holocene to Pleistocene sedimentary sequences, the wetlands present significant reservoirs of information on wetland history, climate changes, and hydrochemical history, and are templates on wetland maintenance and functioning, diagnostic for their geologic/geomorphic setting useful for management of wetlands in Western Australia, nationally, and globally. From a global perspective, the diversity and array of consanguineous suites of the Swan Coastal Plain is unique. An understated aspect of the approach in identifying consanguineous suites of wetlands of the Swan Coastal Plain is that in their geological, geomorphological, and hydrological/hydrochemical setting they provide profound insights into gradual and uninterrupted wetland development, sedimentary filling and ecological functioning because, for a given east–west transect, they are located in the same climate setting but in different geologic/geomorphic and hydrochemical settings. They appear to be unrepresented globally, and therefore, in terms of geoheritage, are internationally significant.     

Groundwater-wetland ecosystem interaction in the semiarid glaciated plains of North America

The prairie wetlands of northern USA and Canada exist in numerous topographical depressions within the glaciated landscape. The wetlands are disconnected from each other most of the time with respect to surface-water drainage. The wetland water balance is controlled by snowmelt runoff and snowdrift from the surrounding uplands, precipitation, evapotranspiration, groundwater exchange, and occasional “fill-spill” connections to other wetlands. Salinity of water and the seasonal variability of water level in these wetlands have a strong influence on the ecosystem. Clay-rich glacial tills, covering much of the region, have very low (0.001–0.01 m/yr) hydraulic conductivity, except for the top several meters where the factures and macropores increase conductivity up to 1,000 m/yr. Transpiration in the wetland margin induces infiltration and lateral flow of shallow groundwater from wetland ponds through the high-conductivity zone, which strongly affects the water balance of wetlands. In contrast, groundwater flow in the deeper low-conductivity till has minor effects on water balance, but has a strong influence on salinity because the flow direction determines if the salts accumulate in wetlands (upward flow) or are leached out (downward flow) under wetlands. Understanding of the roles of shallow and deep groundwater systems will improve the hydrological conceptual framework for the management of wetland ecosystems.     

Effects of plants development and pollutant loading on performance of vertical subsurface flow constructed wetlands

The influent concentration has a great effect on nutrients removal efficiency in vertical subsurface flow constructed wetland systems, but treatment performance response to different C: N: P ratios in the influent are unclear at present. At the first growing seasons, the effects of the plants present or not, season, the different C: N: P ratio in influent condition and their interaction on treatment performances were studied in the planted or the unplanted wetlands in greenhouse condition. Each set of units was operated at hydraulic loading rates of 40 L/d. Low, medium and high-strength (100, 200, 400 mg/L of chemical oxygen demand or 20, 40, 80 mg/L total nitrogen) synthetic sewage were applied as influent. According to the first growing season results, the average removal efficiencies for the unplanted and the planted wetlands were as follows: chemical oxygen demand (44–58 % and 55–61 % respectively), total nitrogen (26–49% and 31–54 %) and total phosphorus (36–64 % and 70–83 %). The both wetlands system was operated as an efficient treatment system of highest average removal rates of both chemical oxygen demand and total phosphorus when medium-strength synthetic sewage were applied. When high strength synthetic sewage was applied, the planted wetlands usually had a higher nutrients removal rates than the unplanted over the study period. The plants grew well under any high loading treatment over the study period. Anyhow, it also proved that the wetland systems have a good capacity to treat different strength wastewater in greenhouse condition.     

黄淮海湿地系统分类体系构建

黄淮海平原是3条大河在时空演化过程中形成的,其内形成了复杂多样的湿地系统和类型.由于受强烈的人类活动影响,湿地系统演变的自然规律特性逐渐消失,明显受到人为调控下的水文情势制约,并在空间分布上也是持续萎缩,湿地系统的整体性联系被明显打破,景观破碎化、退化严重.构建一个符合现存湿地情形、宜于湿地管理的分类体系,对于保护和管理好湿地,发挥其功能具有重要意义.在湿地系统分类中,就人工湿地的划分,突出了其服务功能性质,有利于人工湿地的归类管理.     

The Deposition and Chronology of Cenote T’isil: A Multiproxy Study of Human/Environment Interaction in the Northern Maya Lowlands of Southeast Mexico

Cenotes (natural wells or sinkholes) comprise the most common landscape features in the northern Maya Lowlands of the Yucatán Peninsula, México. Detailed study of dated soil‐sedimentary sequences, recovered from a cenote at the archaeological site T’isil and nearby wetlands, allows a partial reconstruction of environmental variability at the site for the last 2000 years. Biogenic calcite sedimentation and Calcisol development occur during three intervals of increased inundation in cenote and wetland environments, ca. A.D. 300, A.D. 1000, and A.D. 1300. Periods of increased inundation in the cenote and wetlands correlate with wetter climatic intervals, and periods of Maya occupation at sites in the Yalahau region. Evidence for Maya modification of the cenote environment may relate to regional wetland agricultural practices.     

Potency of constructed wetlands for deportation of pathogens index from rural,urban and industrial wastewater

Pathogen removal is essential for wastewater treatment and its potential reuse in agriculture. Three field-scale wastewater treatment systems consisting of free surface flow were operated around 1.5 years receiving water from urban domestic, rural domestic and industrial sources. The study was conducted to evaluate seasonal performance of constructed wetland systems in removing Escherichia coli, Enterococci and total coliforms under continuous hydraulic flow. Results displayed that all three wetlands gain recognition in removing pathogen load with high removal efficacy till water reaches output ports. Removal efficiencies were even higher, 66–93, 78–92 and 80–94% for E. coli, Enterococci and total coliforms, respectively, within constructed wetlands. Remarkably at shorter temporal scales in CW-A, greater homogeneity of pathogen concentrations was assessed at wetland outlet sites. In outlet ports, results displayed a highly effective removal of E. coli concentration 80–90% (June 2015), 86–92% (October 2015) and 79–92% (February 2016), Enterococci 80–94% (June 2015), 83–94% (October 2015) and 80–94% (February 2016) and total coliforms 85–93% (June 2015), 87–95% (October 2015) and 88–96% (February 2016). Positive correlation was observed between bacterial indicators (E. coli–Enterococci, r = 0.038; p < 0.01 and E. coli–total coliforms, r = 0.142; p < 0.01). Removal of bacterial indicators in constructed wetland was also displayed by PCA in which three-component analysis of variance was 98.39% and showed a clear decrease in measured parameter gradients toward samples from outlet ports. Constructed wetlands provide cost-effective treatment systems for reducing the pathogen load in wastewater in variable agro-climatic conditions and thus improve water quality.     

Relating groundwater to seasonal wetlands in southeastern Wisconsin, USA

Historically, drier types of wetlands have been difficult to characterize and are not well researched. Nonetheless, they are considered to reflect the precipitation history with little, if any, regard for possible relation to groundwater. Two seasonal coastal wetland types (wet prairie, sedge meadow) were investigated during three growing seasons at three sites in the Lake Michigan Basin, Wisconsin, USA. The six seasonal wetlands were characterized using standard soil and vegetation techniques and groundwater measurements from the shallow and deep systems. They all met wetland hydrology criteria (e.g., water within 30 cm of land surface for 5% of the growing season) during the early portion of the growing season despite the lack of appreciable regional groundwater discharge into the wetland root zones. Although root-zone duration analyses did not fit a lognormal distribution previously noted in groundwater-dominated wetlands, they were able to discriminate between the plant communities and showed that wet prairie communities had shorter durations of continuous soil saturation than sedge meadow communities. These results demonstrate that the relative rates of groundwater outflows can be important for wetland hydrology and resulting wetland type. Thus, regional stresses to the shallow groundwater system such as pumping or low Great Lake levels can be expected to affect even drier wetland types.     

Mapping wetland cover in the greater Himalayan region: a hybrid method combining multispectral and ecological characteristics

In the greater Himalayan region, wetland ecosystems such as lakes, marshes, and peat lands play an important role in regulating the flow of major rivers. These ecosystems are often overlooked and not well represented on land-use planning and conservation maps. Wetland complexes are partly ephemeral and difficult to map accurately either with digital image processing or visual interpretation. This study developed a hybrid method of extracting spatial patterns of wetland areas which combines month-on-month multispectral classifications of Moderate Resolution Imaging Spectroradiometer data with a sample wetland extraction method based on knowledge of the spectral characteristics of satellite data and wetland ecological systems. The results were compared with the best available sources for lakes and wetlands on global and national scales. It was demonstrated that the method could extract wetlands automatically to a reasonable degree of accuracy and, therefore, reduce the need for extensive ground knowledge. The model was transferred by adjusting parameters through application of high-resolution satellite data (Landsat) in some sub-basin areas. These findings are cognizant with field interviews conducted by wetland experts. The hybrid method and high-altitude wetlands maps will provide decision makers with valuable information about wetland distribution and change in response to global warming and human activities.     

A comparison of ecosystem dynamics in freshwater wetlands

The effects of system closure on the dynamics of productivity and nutrient cycling are examined in four wetlands that differ in plant growth form and magnitudes and sources of water input and nutrient loading. Dynamics in relatively closed ombrotrophicCarex marsh andTaxodium swamp systems from Okefenokee Swamp are compared to those in open, rheotrophic riparian systems. The riparian systems examined includeZizaniopsis marshes along the tidal freshwater portion of the Altamaha River in Georgia and a matureTaxodium-Nyssa swamp along the Cache River in Illinois. Water budgets in the ombrotrophic systems are dominated by precipitation inputs while in the riparian wetlands they are dominated by overbank flooding. Nutrient loading to the open and closed systems differs by only two orders of magnitude, the former depending on atmospheric inputs and the latter depending on tidal and riverine inputs. Comparisons of nutrient import, export, and retention indicate that greater than 90% of inorganic nutrients are retained in the closed systems while less than 5% are retained in the open systems. Nutrient budgets for wetland vegetation, including aboveground uptake, root uptake, leaching, death, and translocation, are constructed. Strong differences in nutrient conservation within plant communities are found between marsh and forested closed systems and between open and closed systems as a whole. There is the indication that nutrients turn over more rapidly and nutrient cycles are less retentive and conservative as systems become more open and nutrient inputs increase. Nutrients turn over more rapidly in marshes with nonwoody vegetation than in swamp forests. This phenomena is partially attributable to the growth form of the vegetation as trees store vast amounts of high Canutrient ratio biomass in boles. Substituting space for time and marsh and swamp wetlands for young and mature ecosystems enables patterns of productivity and nutrient cycling for these wetlands to be compared with Odum’s (1969) predictions of ecosystem development. Patterns of ecosystem development in wetlands agree with those predicted for terrestrial systems in general, but there are many areas of contradiction. The degree of system closure appears to be a major factor controlling nutrient retention and cycling in wetland ecosystems. System closure is also likely to be important in determining the response of wetland systems to global increases in CO₂ levels.     

Soil Organic Carbon Storage Changes in Coastal Wetlands of the Liaohe Delta,China, Based on Landscape Patterns

Growing wetland loss along a coastal area in China was examined through shoreline recession and land use changes. Carbon storage or sequestration in coastal wetland soils was based on vertical marsh accretion and aerial change data. Marshes sequester significant amounts of carbon through vertical accretion; however, large amounts of carbon previously sequestered in the soil profile are lost through rapid land use changes and shoreline recessions. The Liaohe Delta (LHD) was divided into nine landscape types based on Landsat TM digital images from 1991 to 2011. The distributed areas and transfer matrices of each landscape type were calculated. Combined with the organic carbon content and bulk density of 202 soil surface samples from field investigations in 2012, the soil organic carbon pools and stocks were estimated. Results showed that the soil organic carbon pools varied from 0.58 to 9.75 kg m^?2, and organic carbon storage in the upper 20 cm of soil was 1935.92 × 10⁴ and 1863.87 × 10⁴ t in 1991 and 2011, respectively. We attributed these large losses of carbon to rapid land use changes. The construction of levees along the shoreline has triggered large instantaneous losses of previously sequestered carbon through the destruction of 278.06 km² of tidal flats. Our results reveal that the LHD wetlands might not serve as a desired sink of carbon if maladministration practices are applied. These results can provide scientific guidance for decision makers in determining an effective way to maintain the soil carbon pool in the wetlands of the LHD.     

Simulation of the hydrogeologic effects of oil-shale mining on the neighbouring wetland water balance: case study in north-eastern Estonia

The water balance of wetlands plays an integral role in their function. Developments adjacent to wetlands can affect their water balance through impacts on groundwater flow and increased discharge in the area, and they can cause lowering of the wetland water table. A 430 km² area was selected for groundwater modelling to asses the effect of underground mining on the water balance of wetlands in north-eastern Estonia. A nature conservation area (encompassing Selisoo bog) is within 3 km of an underground oil-shale mine. Two future mining scenarios with different areal extents of mining were modeled and compared to the present situation. Results show that the vertical hydraulic conductivity of the subsurface is of critical importance to potential wetland dewatering as a result of mining. Significant impact on the Selisoo bog water balance will be caused by the approaching mine but there will be only minor additional impacts from mining directly below the bog. The major impact will arise before that stage, when the underground mine extension reaches the border of the nature conservation area; since the restriction of activities in this area relates to the ground surface, the conservation area’s border is not sufficiently protective in relation to underground development.     

Assessment of wetland fragmentation in the Tarim River basin, western China

The wetlands in the middle and lower reaches of the Tarim River are a rich area of biodiversity and natural resources in the inland arid region of China. However, this wetland area has decreased in size during the past several decades. Water quality and biodiversity has declined due to expanded agricultural activities since 1960s. Using remote sensing (RS), geographic information system (GIS) and global positioning system (GPS) techniques, we investigated the dynamics, spatial patterns and fragmentation of the wetlands in the middle and lower reaches of the Tarim River from 1980 to 2000. We found that the total area of the wetlands was reduced by 45.8% and the density of the patches increased four times from 1980 to 1990. From 1990 to 2000, though the total area of the wetlands slightly increased the number of the patches increased three times and the density of the patches doubled. Based on the analyses of transition matrixes, diversity and fragmentation indexes, and spatial distribution alternation of the wetlands, we found the landscape diversity and fragmentation indices increased while wetland dominance index decreased dramatically. Among the wetland types, the areas of the river-channel, reservoir and pond wetlands increased while the areas of the lake and marsh wetlands decreased continuously.     

三种人工湿地脱氮除磷效果比较研究

对沸石潜流湿地、砾石潜流湿地和自由表面流人工湿地脱氮除磷性能进行了中试对比试验研究,结果表明在相同进水水质和水力停留时间为1 d的运行条件下,沸石潜流湿地脱氮效果最佳,总氮去除率接近60%;砾石潜流湿地除磷效果最佳,总磷去除率可达70%;自由表面流人工湿地脱氮除磷效果介于沸石和砾石潜流湿地之间.探讨了三种人工湿地脱氮除磷机理方面的差别,并对其进行了经济性、运行方式等方面的比较.     

Common reed grass,<Emphasis Type="Italic">Phragmites australis</Emphasis>, expansion into constructed wetlands: Are we mortgaging our wetland future?

The use of constructed wetlands to replace natural wetlands has become a widespread management tool. Because of the inherent disturbed nature of these sites, constructed wetlands are susceptible to colonization by undesirable plant species. Vegetated communities in 15 constructed wetland sites ranging in age from 1 to 12 yr and in size from 0.4 to 5.3 ha were surveyed using differential global positioning system (GPS) technology in 1994. These sites were re-surveyed in 2000. Colonization of the sites byPhragmites australis expanded from 73% of the sites in 1994 to 80% of the sites in 2000. The total area colonized byP. australis within the sites increased from 3.47 to 4.96 ha. In some sites, the area ofP. australis decreased, which appears to be correlated with an increase in scrub-shrub vegetation (0.986, p=0.014). Similar to results from the previous study, sites that are surrounded by subtidal perimeter ditches have significantly lessP. australis than those sites without perimeter ditches (p=0.019).P. australis expansion rates within the sites varied from 0.1 to 5.6 yr^?1. Colonization of constructed wetland sites byP. australis should be a continued concern of resource managers. Activities such as planting scrub-shrub species on the upland-wetland berm and construction of subtidal perimeter ditches should be considered as methods to reduce the probability of invasion.     

A field study (Massachusetts, USA) of the factors controlling the depth of groundwater flow systems in crystalline fractured-rock terrain

Groundwater movement and availability in crystalline and metamorphosed rocks is dominated by the secondary porosity generated through fracturing. The distributions of fractures and fracture zones determine permeable pathways and the productivity of these rocks. Controls on how these distributions vary with depth in the shallow subsurface (<300 m) and their resulting influence on groundwater flow is not well understood. The results of a subsurface study in the Nashoba and Avalon terranes of eastern Massachusetts (USA), which is a region experiencing expanded use of the fractured bedrock as a potable-supply aquifer, are presented. The study logged the distribution of fractures in 17 boreholes, identified flowing fractures, and hydraulically characterized the rock mass intersecting the boreholes. Of all fractures encountered, 2.5% are hydraulically active. Boreholes show decreasing fracture frequency up to 300 m depth, with hydraulically active fractures showing a similar trend; this restricts topographically driven flow. Borehole temperature profiles corroborate this, with minimal hydrologically altered flow observed in the profiles below 100 m. Results from this study suggest that active flow systems in these geologic settings are shallow and that fracture permeability outside of the influence of large-scale structures will follow a decreasing trend with depth.     

基于GSFLOW的镜湖湿地地表水与地下水耦合数值模拟

湿地地表径流包括明渠流和片流等多种形式,且存在海绵状土壤层,其地表水-地下水耦合模拟困难。针对湿地片流和海绵层模拟不准确的问题,以绍兴镜湖国家城市湿地公园为研究对象,考虑湿地多年植物生长沉积形成的独特海绵层,基于GSFLOW模型构建湿地地表水与地下水耦合数值模型,通过二维扩散方程模拟湿地片流、一维圣维南方程模拟湿地明渠流,使用竖管法测量湿地海绵层渗透系数,利用模拟区水文站的监测数据率定模型参数并对模拟结果进行验证,应用校正后模型模拟湿地地表水与地下水的水量交互过程,并对研究区进行水均衡分析。研究结果表明:考虑湿地海绵层的湿地地表水与地下水耦合模型能较为真实地反映湿地水文特性,湿地以地表水补给地下水为主,补给量随降雨量变化。研究建立的湿地地表水与地下水耦合模型合理可靠,对湿地水文分析有良好的应用价值。     

三江平原湿地消长与区域气候变化关系研究

以遥感手段为主,提取近20年来多个时期三江平原湿地变化动态数据。将湿地动态数据与历年气象数据相对变化比较处理后,再作灰色关联分析,可以发现它们之间的相互关系。研究表明三江平原湿地面积减小迅速,三江平原区域气候环境变化剧烈,超过全球气候变化速度。通过灰色关联分析可以发现,湿地在维持区域"冷湿"效应中作用突出,三江平原湿地的变化与气温变化成负相关,与降水、湿度变化成正相关。湿地消长与气候要素中的降水因子的相关关系最大,与日照因子相关关系较低,与降雪因子几乎无关。     

Shallow subsurface diagenesis of Pleistocene periplatform ooze: northern Bahamas

Previous studies on early submarine diagenesis of periplatform carbonates have implied that these originally polymineralic (aragonite, magnesian calcite, calcite) sediments are susceptible to early diagenesis only in current-swept open seaways or where surficially exposed by erosion on the seafloor. It has also been proposed that while in the shallow subsurface, periplatform oozes retain their original mineralogy for at least 200,000–400,000 yr and remain unlithified for tens of millions of years. Evidence is reported here for extensive calcitization and selective lithification of periplatform oozes of late Pleistocene age in two piston cores collected from water depths of ～ 1,000 m north of Little Bahama Bank. It is shown that shallow (<30 m) subsurface diagenesis can significantly alter the original mineralogy of periplatform oozes to predominantly calcite in less than 440,000 yr, and that cementation by calcite can produce chalk-ooze sequences within the same time-frame. Periplatform oozes that originally contain a high percentage of bank-derived magnesian calcite appear to have a higher diagenetic potential than those originally low in magnesian calcite. Shallow subsurface calcitization and fithification greatly reduce the diagenetic potential of periplatform carbonates, and chalk-ooze sequences apparently can persist for tens of millions of years and to burial depths of at least 300 m. Shallow subsurface diagenesis, at water depths > 1,000 m, proceeds via dissolution of magnesian calcite and aragonite and reprecipitation of calcite as allochem fillings, exterior overgrowths and cement. It is speculated that density-driven ‘Kohout convection‘, where seawaters under-saturated with respect to magnesian calcite and aragonite and saturated/supersaturated with respect to calcite flow through the margins of carbonate platforms, is the primary driving mechanism for shallow subsurface diagenesis. Removal of Mg during early stages of deep seafloor and shallow subsurface diagenesis should increase the Mg content of interstitial waters which is likely to increase the ‘dolomitizing potential’ of Kohout convection fluid flow.     

A Landscape-Scale Assessment of Above- and Belowground Primary Production in Coastal Wetlands: Implications for Climate Change-Induced Community Shifts

Above- and belowground production in coastal wetlands are important contributors to carbon accumulation and ecosystem sustainability. As sea level rises, we can expect shifts to more salt-tolerant communities, which may alter these ecosystem functions and services. Although the direct influence of salinity on species-level primary production has been documented, we lack an understanding of the landscape-level response of coastal wetlands to increasing salinity. What are the indirect effects of sea-level rise, i.e., how does primary production vary across a landscape gradient of increasing salinity that incorporates changes in wetland type? This is the first study to measure both above- and belowground production in four wetland types that span an entire coastal gradient from fresh to saline wetlands. We hypothesized that increasing salinity would limit rates of primary production, and saline marshes would have lower rates of above- and belowground production than fresher marshes. However, along the Northern Gulf of Mexico Coast in Louisiana, USA, we found that aboveground production was highest in brackish marshes, compared with fresh, intermediate, and saline marshes, and belowground production was similar among all wetland types along the salinity gradient. Multiple regression analysis indicated that salinity was the only significant predictor of production, and its influence was dependent upon wetland type. We concluded that (1) salinity had a negative effect on production within wetland type, and this relationship was strongest in the fresh marsh (0–2 PSU) and (2) along the overall landscape gradient, production was maintained by mechanisms at the scale of wetland type, which were likely related to plant energetics. Regardless of wetland type, we found that belowground production was significantly greater than aboveground production. Additionally, inter-annual variation, associated with severe drought conditions, was observed exclusively for belowground production, which may be a more sensitive indicator of ecosystem health than aboveground production.