海南岛红树林湿地的水鸟多样性

从2015年10月至2016年6月,调查了海南岛17个沿海红树林湿地春、夏、秋、冬四季的湿地鸟类。共记录水鸟74种,隶属5目12科,其中,翘鼻麻鸭（Tadorna tadorna）为海南鸟类分布新记录种。位于海南省儋州市白马井镇洋浦湾的新英作为黑脸琵鹭（Platalea minor）新的越冬点被发现。全岛水鸟数量较多的地点在万宁小海、海口东寨港和乐东莺歌海,种类较多的地点在东寨港、东方四更和莺歌海。Jaccard指数分析表明,栖息地具有相似适合度的地方,水鸟种类相似性更高,人工湿地之间的水鸟相似性高,人工湿地与天然湿地之间的水鸟相似性低。海南岛沿海红树林湿地的鸟类种类和数量随季节变化,秋、冬季种类多、数量丰富,春、夏季的种类和数量均较少。鸻鹬类在春、冬季种类和数量占比均为最大,秋、夏季数量最多的为鹭类。Shannon-Wiener指数、Pielou均匀度指数分析得出东寨港的多样性指数最高,东寨港和莺歌海的均匀度指数表现较高。研究表明,海南岛的沿海红树林湿地是很多水鸟的重要栖息地,保护红树林是保护湿地水鸟多样性的关键。     

Fine scale waterbody data improve prediction of waterbird occurrence despite coarse species data

While modelling habitat suitability and species distribution, ecologists must deal with issues related to the spatial resolution of species occurrence and environmental data. Indeed, given that the spatial resolution of species and environmental datasets range from centimeters to hundreds of kilometers, it underlines the importance of choosing the optimal combination of resolutions to achieve the highest possible modelling prediction accuracy. We evaluated how the spatial resolution of land cover/waterbody datasets (meters to 1 km) affect waterbird habitat suitability models based on atlas data (grid cell of 12 × 11 km). We hypothesized that the area, perimeter and number of waterbodies computed from high resolution datasets would explain distributions of waterbirds better because coarse resolution datasets omit small waterbodies affecting species occurrence. Specifically, we investigated which spatial resolution of waterbodies better explain the distribution of seven waterbirds nesting on ponds/lakes with areas ranging from 0.1 ha to hundreds of hectares. Our results show that the area and perimeter of waterbodies derived from high resolution datasets (raster data with 30 m resolution, vector data corresponding with map scale 1:10 000) explain the distribution of the waterbirds better than those calculated using less accurate datasets despite the coarse grain of the species data. Taking into account the spatial extent (global vs regional) of the datasets, we found the Global Inland Waterbody Dataset to be the most suitable for modelling distribution of waterbirds. In general, we recommend using land cover data of a resolution sufficient to capture the smallest patches of the habitat suitable for a given species’ presence for both fine and coarse grain habitat suitability and distribution modelling.     

The limits of phosphorus removal in wetlands

The phosphorus concentrations exported from wetlands are explored via data and a first order model. The graph of outlet concentration versus areal phosphorus loading is used to display these data and the model. For a given wetland, data and models show that P concentrations show an S curve response to increasing P loadings. The lower plateau is the background concentration and the upper plateau is the inlet concentration. The position of the ascending limb between the two plateaus is positioned differently for different wetlands. Phosphorus (P) removal in wetlands is often typified by a stable decreasing gradient of P concentrations from inlet to outlet, and an accompanying stable decreasing gradient in P assimilation. Limits to removal are inherent in the physical, chemical and biological processes. A lower outlet concentration limit exists because of the P cycle in the un-impacted wetland. The loading at which the outlet concentration departs from background, the lower knee in the loading curve, varies from wetland to wetland. An upper outlet concentration limit is imposed by the source concentration for extremely high inflows. The first order mass balance equation interpolates between these limits. The model gives further insights about performance within an overall envelope. The water carrying capacity of the wetland precludes flows in excess of the hydraulic conveyance capacity, thus limiting the possible P loadings to the system. Conversely, extremely low hydraulic loadings cause the wetland to be dominated by atmospheric additions and losses. The central tendency of inter-system data in the North American Database is shown to be inadequate to draw generalized conclusions about ecosystem processes in an individual wetland. The proposed one gram rule of Richardson, et al. (1997) is shown to be an over-simplification.     

Growth and nutrient dynamics of soft-stem bulrush in constructed wetlands treating nutrient-rich wastewaters

The growth characteristics and nutritional status ofSchoenoplectus tabernaemontani (C.C. Gmelin)Palla (soft-stem bulrush or lake clubrush) wereinvestigated during the second and third growthseasons in four equivalent subsurface-flow, gravel-bedconstructed treatment wetlands. Each wetland wassupplied with a different hydraulic loading rate ofagricultural wastewater, covering the range commonlyapplied to such systems. Harvest and demographictechniques were combined to determine seasonalpatterns and gradients of growth and nutrientallocation, and net annual primary productivity(NAPP). Marked seasonal patterns of early springemergence, summer growth and autumn senescence wereobserved, with little over-wintering of liveabove-ground biomass. Starch, the dominant long-termstorage substance, comprised 20% of rhizome dryweight (DW) in autumn. Mobilization during springreduced concentrations by around half, with a trend ofincreasing depletion in the higher loaded wetlands.NAPP, including above-ground mortality, during thesecond growth season ranged between 2.5 and 3.5 kg DWm^-2, with 10-23% allocated to below-groundgrowth. Mean above-ground live and dead biomass rangedbetween 1.75 and 2.65 kg DW m^-2 by mid-summer,with below to above-ground biomass ratios similar inall wetlands at between 0.6 and 0.7. Rhizomes, whichcomprised around 80% of the below-ground biomass,were generally restricted to the upper 10 cm of thesubstratum and over half the root biomass alsooccurred in this zone, with very few roots penetratingbelow 30 cm depth. High culm concentrations of N,P, Mg and Zn in spring declined markedly over thegrowth season, while S and Ca showed generalincreases, and K, Fe and Cu remained relativelystable. Gradients of decreasing tissue concentrationof most macronutrients were noted with increasingdistance from wastewater inflows. Plant accumulationof N rose by 20-35 g m^-2 and P by 4-9 g m^-2with seasonal re-growth of above-ground shoots. Netplant N and P uptake rates rose to maximum values of0.3 g N m^-2 d^-1 and 0.1 g P m^-2d^-1 in early summer, declining markedly duringlate summer and autumn. Mass balance assessments of Nand P accumulation in plants at near maximum seasonalbiomass, after three growth seasons, showed that only6 to 11% of the N removal and 6 to 13% of the Premoval recorded from wastewaters applied to thewetlands could be ascribed to plant uptake andaccumulation.     

Filling of a wetland (Seine estuary,France): natural eutrophication or anthropogenic process? A sedimentological and geochemical study of wetland organic sediments

Hydrobiologia - For over a century the Seine estuary has been highly affected by human activities, resulting in a reduction of the surface of wetland habitat. Several ponds of the Vernier Marsh,...     

Evaluation of biotracers to monitor effluent retention time in constructed wetlands

AIMS: With concern surrounding the environmental impact of chemical tracers on the aquatic environment, this paper presents the initial evaluation of biotracers used to determine the effluent retention time, an important performance indicator, in a Free Water Surface Constructed Wetland. METHODS AND RESULTS: Production of the biotracers, coliphage MS2, and the bacteriophage of Enterobacter cloacae and antibiotic resistant endospores of Bacillus globigii is described in detail. Their subsequent use in three separate tracer experiments - January, March and June (2000) - revealed the variability of retention time with respect to effluent flow. The biotracer MS2 showed the constructed wetland had a retention time of 8-9 h at a mean discharge of 0.9 l s-1, increasing to 10-12 h at a mean discharge 0.3 l s-1. A similar retention of 9-10 h at a mean discharge of 0.3 l s-1 was calculated for the Ent. cloacae phage. In contrast, use of endospores revealed considerably longer retention times at these mean discharge rates; 12-24 h and 36-48 h, respectively. CONCLUSION: Biotracers could provide a useful and environmentally friendly technique to monitor effluent retention in constructed wetlands. At this stage the phage tracers appear particularly promising due to ease of isolation and recovery. SIGNIFICANCE AND IMPACT OF THE STUDY: Initial results are encouraging and have highlighted the potential of biotracers as alternatives to chemical tracers, even in microbially-rich waters.     

The effects of population size limitation on fecundity in mosaic populations of the clonal macrophyte Scirpus maritimus (Cyperaceae)

The clonal macrophyte Scirpus maritimus (Cyperaceae) propagates locally by rhizomes and reproduces sexually by achenes. The purpose of this paper was to examine whether in size-limited habitats in patchy and discrete marshes in two Mediterranean wetlands in southern France natural populations may suffer from a reduced maternal fecundity due to a deficit in outcross pollen. We first verified that S. maritimus suffers from a reduced fecundity when self-pollinated. At a site in the Camargue, mean fecundity (mean number of achenes per centimetre of spikelet) measured in 1995 and 1996 in seven and nine populations, respectively (surface area from 50 to 4500 m) increased significantly with population surface area in 1995 but not in 1996. In the second wetland at Roquehaute, which is composed of small ponds, fecundity was very low in all 12 local populations studied in 1996 (1.1 achenes per spikelet, SD = 1.2) and was not correlated with the population surface area (from 10 to 400 m). We performed a pollen supplementation experiment in five local populations at Roquehaute to determine whether this low fecundity may be due to a pollen limitation. A significant increase in fecundity after among-pond pollinations compared to within-pond pollinations indicated that local populations suffer from a deficit in outcross pollen, since each pond appears to contain one or a few number of clones (or incompatibility types). In S. maritimus, clonal spread may have a cost in terms of reduced fecundity in small habitats because each habitat is colonized by very few clones.     

Lakes Hula and Agmon: destruction and creation of wetland ecosystems in northern Israel

A portion of the former Lake Hula wetland (northern Israel) was re-flooded in spring 1994 and the physical, chemical and biological developments within the resulting new lake and wetland complex (Agmon) was followed closely by a multi-disciplinary scientific team. The first three years of study relating to Lake Agmon are reported in this issue of Wetlands Ecology & Management. We provide in this paper a general background on the Lake Hula Draining Project in the 1950s and the recent re-flooding and creation of the Agmon wetland.     

Hysteresis in the temperature response of carbon dioxide and methane production in peat soils

The ability to predict the effects of climate change on trace gas fluxes requires a knowledge of microbial temperature responses. However, the response of a microbial community to temperature in a given substrate may be complicated by its thermal history. To examine the effect of sequentially changing temperature on methane and carbon dioxide production in different peat types, we incubated anaerobic peat samples from 3 types of northern peatlands, a bog, a sedge fen and a cedar swamp, in both rising and falling temperature regimes. Graphic and statistical comparisons of the different temperature regimes suggest hysteresis in microbial response to temperature, although the absolute rates at any given temperature often did not differ. Where regressions for temperature response (Arrhenius plots) were significant, they generally differed between temperature regimes. The greatest differences among treatments occurred during the first half of the 40-d incubation. Increases in carbon dioxide production were similar across all peat types, but methanogenesis varied widely: methane production was uniformly low in the bog peat but increased sharply with temperature in the other two peat types. The complicating effect of history or chronology on substrate responses to environmental stimuli may restrain our ability to model the responses of complex systems to changing conditions.