A comparison of purification efficiencies of various constructed ecosystems (aquatic,semi-aquatic and terrestrial) receiving urban wastewaters

Tests were carried out under controlled conditions in the Experimental Plant of Viville (Arlon, Belgium) to enhance the purification of urban wastewater by natural means. The results demonstrate the need to structure treatment systems in a series of different artificial ecosystems (or a Hierarchical Mosaic of Artificial Ecosystems — MHEA in French). The first two levels we used were made up of an unplanted aquatic ecosystem (stabilization pond) followed by a semi-aquatic ecosystem planted withTypha latifolia L. in which the water flows over the substrate. At a flow rate of 4 m²/PE (1 PE=150 1/day of typical urban wastewaters in Belgian rural zones), this first stage substantially reduces suspended solids (SS), COD and BOD₅, a significant amount of tot-N and tot-P, and reduces pathogens by 100-fold. Further, the system is easy to manage (sludge is eliminated in the first stage and biomass is collected in the second stage) and the treatment system does not clog up.Nevertheless, real and sustainable environmental protection demands even higher performance rates, and these first two stages, both in terms of design and dimension, can only be considered as a satisfactory part of a MHEA system. Artificial aquatic, semi-aquatic, and terrestrial ecosystems were systematically compared at the third and fourth stage of the system to increase the overall removal efficiency.The most complete and efficient system in our tests (i.e., the one that provides the most successful primary (SS), secondary (COD and BOD₅) and tertiary (N and P) treatment and the best pathogens removal rates) was made up of 3 sequential series of ecosystems: an aquatic ecosystem whose flow went into a plantedTypha latifolia system (surface water flow), that flowed into a terrestrial ecosystem planted withAlnus glutinosa (L.) Gaertn (vertical subsurface water flow). A total surface area (stages 1–4) of 8 m²/PE ensured a high performance level whose outflow conformed to the strictest European norms.     

Seasonality of mycorrhizae in coastal sand dunes of Baja California

 Populations of arbuscular mycorrhizal fungi were estimated from spores associated with seven plant species in coastal dunes at El Socorro, near Ensenada, Baja California, during six months in 1992. The seasonal patterns of percent root colonization were also described in the same species during the wet season (January–March) and the dry season (April–July). Comparisons were made between the pioneer species (Abronia maritima) in the mobile dunes and six species (Abronia umbellata, Atriplex julacea, Camissonia californica, Haplopappus venetus, Helianthus niveus and Lotus spp.) in the fixed dunes. Mycorrhizal colonization in Abronia maritima was slight (<1%) and we observed few spores (<1/g soil). All of the species in the fixed dune formed mycorrhizae with up to 80% colonization in early summer, and no more than 4 spores/g soil by late summer. The highest percentages of total colonization and abundance of spores did not coincide temporally for any of the seven species, but the percentages were higher in summer than in spring. Arbuscules were more abundant when the soil was moist, and vesicles more abundant when it was dry. Accepted: 16 August 1995     

Oxygen depletion and carbon dioxide and methane production in waters of the Pantanal wetland of Brazil

This study examines dissolved O₂, CO₂ and CH₄ in waters of the Pantanal, a vast savanna floodplain in Brazil. Measurements are presented for 540 samples from throughout the region, ranging from areas of sheet flooding to sluggish marsh streams to the major rivers of the region. Dissolved O₂ is often strongly depleted, particularly in waters filled with emergent vascular plants, which are the most extensive aquatic environment of the region. Median O₂ concentrations were 35 M for vegetated waters, 116 M for the Paraguay River, 95 M for tributary rivers, and 165 M for open lakes (atmospheric equilibrium, 230–290 M). Airwater diffusive fluxes were calculated from dissolved gas concentrations for representative vegetated floodplain waters, based on data collected over the course of an annual cycle. These fluxes reveal about twice as much CO₂ evasion as can be accounted for by invasion of O₂ (overall means in nmol cm^-2 s^-1: O₂ 0.18, CO₂ 0.34, and CH₄ 0.017). Methanogenesis is estimated to account for ca. 20% of the total heterotrophic metabolism in the water column and sediments, with the remainder likely due mostly to aerobic respiration. Anaerobic respiration is limited by the low concentrations of alternate electron acceptors. We hypothesize that O₂ transported through the stems of emergent plants is consumed in aerobic respiration by plant tissues or microorganisms, producing CO₂ that preferentially dissolves into the water, and thus explaining most of the excess CO₂ evasion. This hypothesis is supported by measurements of gases in submersed stems of emergent plants.     

有机物料对黄河三角洲滨海盐土的根际效应：Ⅱ.盐分效应

采用根际袋法研究腐熟有机物料对滨海盐土水稻淹水层及土壤的盐分和植株元素吸收的影响．结果表明,在不排水条件下,施用有机物料使淹水层盐分上升,土壤盐分也高于对照,但其根际富集程度降低;植株Ｋ吸收增强,Ｎａ则明显下降,Ｃａ、Ｍｇ含量略增,但变化没有１价元素明显．     

Using 18O/16O data to examine the mixing of water masses in floodplain wetlands

Oxygen isotopic data were used to assess how far waters from the Savannah River, a major river in the Southeastern United States, backed up and inundated the wetlands along a small Coastal Plain tributary during a flood. This approach worked because the water of this tributary, Unper Three Runs, had an oxygen isotopic composition (¹⁸O = –4.9 ) distinct from Savannah River water (¹⁸O = –3.2 ).Two sample surveys were taken from the mouth of Upper Three Runs to 2 km upstream. Waters were isotopically uniform along the length of the sample transect when both river and tributary water levels were below bankfull. Visual estimates of turbidity taken when both the river and tributary overflowed their channels and inundated adjacent wetlands indicated that Savannah River water extended about 300 meters up the tributary channel. In contrast, the isotopic data indicated that a mixing zone of river and tributary waters extended about 1100 meters upstream. Although this mixing zone was documented only in the channel of Upper Three Runs, it probably extended into adjacent parts of the riparian wetland, potentially affecting ecological processes due to the differing water quality. This study was conducted in a single river-tributary system and the approach is probably applicable in other large rivers.Corresponding Editor: R. SharitzTo Whom Correspondence should be sent     

Assessing the impact of water management options upon vegetation development in drained lake side wetlands

Lake-side wetlands and their original vegetation have become rare in The Netherlands. The few remaining lake-side wetlands (also called: boezemlands) are mostly managed as nature reserves. Much attention is given to the preservation and restoration of species-rich meadows (Calthion palustris). In lake-side wetlands, both desiccation and acidification endanger the characteristic environmental conditions of these plant communities.The aim of this study was to develop guidelines for water management in different types of boezemlands. Three sites, representing different hydrological conditions, were selected. The steady-state groundwater model FLOWNET was used to describe water movement. The results of vegetation surveys were used to produce response curves for important species, giving correlations between their presence and environmental conditions (groundwater levels, soil pH).     

The use of diatoms in monitoring the development of created wetlands at a sandmining site in Western Australia

Former sand-mining pits at Capel, 200 km south of Perth in Western Australia, have been rehabilitated into artificial wetlands since 1975–1979. A chain of fresh water lakes was created as a potential waterbird refuge and an area for passive recreation. Initially, the lakes had low pH, high ammonium, iron and manganese levels and low phosphorus concentration. The lakes were characterised by low diversity of diatoms dominated by acidophilous species. Following an increase in pH in the effluent water discharged into the lake from the mining process plant and landscaping of the lakes since 1988, the diversity of diatoms gradually increased. The system is now dominated by periphytic diatom communities, preferring high conductivity. There has been a marked transition in the diatom community from acidophilous to alkaliphilous species. Planktonic diatom blooms replaced dinoflagellate blooms. Concomitantly, there has been a dramatic increase in the diversity of invertebrates and waterbirds in these lakes. The value of diatoms in assessing the progressive development of created wetlands as self-sustaining ecosystems at sand mines in Australia is discussed.     

13C natural abundance variations in carbonates and organic carbon from boreal forest wetlands

¹³C natural abundance variations were measured in peat soil and vegetation from two contrasting boreal forest wetlands: an upland watershed basin and a permanently saturated lowland mire. Evidence of methane oxidation was shown in the permanently saturated wetland with δ¹³C values as low as -97 ‰ in carbonate minerals found in floating peat mats. It is postulated that¹³C depleted CH₄ is oxidized in the mat and reacts with calcium ions to form calcite (identified through x-ray diffraction). Methane flux measurements during the summer of 1992 showed much lower fluxes in areas with floating peat mats relative to open water. Secondary carbonates in the basin peat have isotope compositions close to the δ¹³C values of the peat organic carbon (-25 ‰), indicating their origin from fermentation and possibly from sulfate-reduction. In the upland basin peat deposits, the δ¹³C_PDB values of organic C were constant with depth, while the permanently saturated mire had localities of¹³C enrichment in deeper layers of the peat. The¹³C enrichment may reflect areas of intense CH₄ production in which¹³C enriched residual substrate is left behind during the production of highly¹³C depleted CH₄.     

A waterfowl seed-dispersal network from the Neotropical region is nested and modular

Seed dispersal by vertebrates is fundamental for the persistence of plant species, forming networks of interactions that are often nested and modular. Networks involving angiosperms and frugivorous birds are relatively well-studied in the Neotropical region, but there are no previous studies of networks involving waterbirds. Here, we describe the structure of a Neotropical waterfowl seed-dispersal network and identify the species that have an important role for the network structure. We used information on 40 plant taxa found in fecal samples of five common waterfowl species to calculate the nestedness (NODF), weighted nestedness (WNODF), modularity, and weighted modularity of the network. We found that the network was nested, with yellow-billed teal showing the highest contribution both to nestedness and weighted nestedness. Twenty-four plant species contributed positively to weighted nestedness, with Salzmann's mille graines presenting the highest influence both to nestedness and weighted nestedness. The network was modular, but the weighted modularity was not significant. These results need to be considered with caution due to incomplete interaction sampling for two species. Ringed teal, Brazilian teal, and yellow-billed teal were considered hub modular species. Among plants, beak sedges and water snowflake were considered modular hub species, while Salzmann's mille graines and spikerush were network connectors. The structure of this Neotropical waterbird seed-dispersal network differed from the only previous waterfowl network study, from Europe, which found similar level of nestedness but no significant modularity. We include several possible explanations for this discrepancy and identified priorities for future research into waterbird–plant interaction networks. Abstract in Portuguese is available with online material.     

Phenotypic trait differences between Iris pseudacorus in native and introduced ranges support greater capacity of invasive populations to withstand sea level rise

Aim

Tidal wetlands are greatly impacted by climate change, and by the invasion of alien plant species that are being exposed to salinity changes and longer inundation periods resulting from sea level rise. To explore the capacity for the invasion of Iris pseudacorus to persist with sea level rise, we initiated an intercontinental study along estuarine gradients in the invaded North American range and the native European range.

Location

San Francisco Bay-Delta Estuary; California, USA and Guadalquivir River Estuary; Andalusia, Spain.

Methods

We compared 15 morphological, biochemical, and reproductive plant traits within populations in both ranges to determine if specific functional traits can predict invasion success and if environmental factors explain observed phenotypic differences.

Results

Alien I. pseudacorus plants in the introduced range had more robust growth than plants in the native range. The vigour of the alien plants was reflected by expression of higher leaf water content, fewer senescent leaves per leaf fan, and more carbohydrate storage reserves in rhizomes than plants in the native range. Moreover, alien plants tended to show higher specific leaf area and seed production than native plants. I. pseudacorus plants in the introduced range were less affected by increasing salinity and were exposed to deeper inundation water along the estuarine gradient than those in the native range.

Main Conclusions

Functional trait differences suggest mature populations of I. pseudacorus in the introduced range have greater adapted capacity to adjust to environmental stresses induced by rising sea level than those in the native range. Knowledge of these trait responses can be applied to improve risk assessments in invaded estuaries and to achieve climate-adapted conservation goals for conservation of the species in its native range.