Pollutants In Wetlands Research Articles

Demonstration Project of Wetlands Restoration and Pollution Control - A Case Study in Xiangtan Manganese Mine, China

Demonstration project attempted to restore the terrestrial habitats around wetlands and reduce the manganese (Mn) pollution of wetlands. Project had tested five kinds of trees for phytoremediation in terrestrial habitats, and designed Ecological interception system (EIS) to control the Mn pollution to wetlands. EIS was composed of the surface runoff collection system (SRCS) and the Treatment system (TS). SRCS composed of cobblestones, high-capacity adsorbent fillers, sands and plants. TS composed of three subsurface wetland units processing modules. The results show that: (1)New soil and base fertilizer applied in the plant pits can effectively improve plants survival rate; (2)Koelreuteria paniculata, Elaeocarpus sylvestris and Paulownia can be used for phytoremediation in terrestrial habitats; (3)Canna warszewiczii, Boehmeria, Thalia dealbata and other nine kinds plants in the EIS can absorb the Mn element effectively; (4)EIS can purify the water effectively. The complex project was based on the biological principles, ecological principles and biochemical effects which provides a reasonable ecological engineering model suitable for the restoration of polluted wetlands.

Development of a time-stepping sediment budget model for assessing land use impacts in large river basins

The use of river basin modelling to guide mitigation of non-point source pollution of wetlands, estuaries and coastal waters has become widespread. To assess and simulate the impacts of alternate land use or climate scenarios on river washload requires modelling techniques that represent sediment sources and transport at the time scales of system response. Building on the mean-annual SedNet model, we propose a new D-SedNet model which constructs daily budgets of fine sediment sources, transport and deposition for each link in a river network. Erosion rates (hillslope, gully and streambank erosion) and fine sediment sinks (floodplains and reservoirs) are disaggregated from mean annual rates based on daily rainfall and runoff. The model is evaluated in the Burdekin basin in tropical Australia, where policy targets have been set for reducing sediment and nutrient loads to the Great Barrier Reef (GBR) lagoon from grazing and cropping land. D-SedNet predicted annual loads with similar performance to that of a sediment rating curve calibrated to monitored suspended sediment concentrations. Relative to a 22-year reference load time series at the basin outlet derived from a dynamic general additive model based on monitoring data, D-SedNet had a median absolute error of 68% compared with 112% for the rating curve. RMS error was slightly higher for D-SedNet than for the rating curve due to large relative errors on small loads in several drought years. This accuracy is similar to existing agricultural system models used in arable or humid environments. Predicted river loads were sensitive to ground vegetation cover. We conclude that the river network sediment budget model provides some capacity for predicting load time-series independent of monitoring data in ungauged basins, and for evaluating the impact of land management on river sediment load time-series, which is challenging across large regions in data-poor environments.

Influence of low levels of water salinity on toxicity of nitrite to anuran larvae

Reactive nitrogen compounds such as nitrite (NO2-) are highly toxic to aquatic animals and are partly responsible for the global decline of amphibians. On some fish and Caudata amphibian species low levels of sodium chloride significantly reduce the toxicity of nitrite. However, the nitrite–salinity interaction has not been properly studied in anuran amphibians. To verify if chloride (Cl−) attenuates NO2- toxicity, eggs and larvae of three anuran species were subjected to a series of NO2- solutions combined with three salt concentrations (0, 0.4 and 2 or 0, 0.052 and 0.2gL−1NaCl). One of the species tested originated from two different populations inhabiting highly contrasted nutrient richness environments: lowland Doñana Natural Park and Sierra de Gredos Mountain. In general, the presence of Cl− increased survival and growth of lowland Pelophylax perezi and activity of mountain P. perezi larvae exposed to NO2-, thus attenuating the toxicity of NO2- to developing amphibians. Mountain amphibian populations appeared to be much more sensitive to the concentrations of NO2- and Cl− used in this experiment than coastal conspecifics, suggesting possible adaptation of populations to local conditions. Nitrogen pollution in coastal wetlands poses a serious threat to aquatic organisms, causing direct toxicity or indirect effects via ecosystem eutrophication. The presence of low to medium levels of salinity that would be common in coastal wetlands may attenuate the direct effects of increasing concentrations of nitrogenous compounds in water bodies. Furthermore, treating cultures of endangered anurans with small amounts of NaCl may provide an additional protective measure.

Geographical Multianalysis and Function Division of Wetland

Wetlands are considered as one of the most productive ecosystems on earth, and more vulnerable and sensitive compared to other ecosystems. With the development of the society, wetlands are suffering serious degradation and loss due to intense anthropogenic disturbance, such as wetland pollution, land use, etc. As one of the effective management measurements, regionalization of wetland function is helpful to have resources in a sustainable development pattern. This paper takes Widgeon Lake, in Beijing, as study region, combining with multi-source remote sensing data, wetland investigation, and the field and meteorological observation data, to analyzes natural features of wetland surrounding, rare feature of wetland type, rare feature of wetland species and the impact of human activities on the wetland. On the other hand, the species and species distribution, soil type and soil moisture, vegetation type and vegetation growing feature, soil erosion and land cover are analyzed, in order to implement regionalization of wetland. Consequently, based on the principles of landscape ecology and wetland science, the function division is conducted, and the leading function area is determined based on GIS technique and overlay analyses, correlation analyses, and leading index methods. As to the management district, according to the hydrological situation and the DEM, the supplement region and protection region are marked out firstly. Then the center, buffer and experiment regions are ascertained in the protection region. As to the leading function area, the protection region is divided into bird protection, vegetation protection, water environment, material supplement, recreation and service regions.

Wetland Degradation and Ecological Restoration

Wetlands are among the most important ecosystems on earth and functioned as the “kidneys” of the earth, which play an important role in maintaining ecological service functions. However, with the rapid growth in human populations, wetlands worldwide are suffering from serious degradation or loss as affected by wetland pollution, wetland reclamation, civilization and land use changes, and so forth. Wetland degradation has potential influences on human health, biodiversity, regional climate, and regional ecological security. Therefore, it is an urgent task to recover these degraded wetlands. In recent years, wetland protection, restoration, and its reasonable exploitation have been paid much more attention to by most governments and researchers. Moreover, wetland restoration has become the frontier fields of wetlands science, which has been listed as one of important themes in these recent international wetlands and ecological conferences. Understanding wetland degradation processes can contribute to better effective wetland restoration. Therefore, we organized this special issue on “wetland degradation and ecological restoration.” The objective of this special issue is to emphasize the effects of human activities on wetland ecosystems, the relationships between soil, water, and plant in wetlands, and wetland restoration issues and applications.

Urban lakes in a developing nation: Drivers, states and impacts of water quality and quantity in Dhaka, Bangladesh

AbstractThis study examined pollution and shrinkage of urban lakes in the rapidly urbanizing city of Dhaka, Bangladesh. A mixed‐method approach was employed, nested within the European Environmental Agency Drivers, Pressure, States, Impacts, Responses Framework and Environmental Systems Analysis tools (as stakeholder and functions analysis methodologies). A variety of stakeholders and policymakers were first interviewed, being asked to participate in an exercise identifying their perceptions of the greatest challenges facing urban lakes in Dhaka. The current quantity and quality of lakes in Dhaka was subsequently assessed through a combination of field work, government reports and satellite imagery analysis. The results indicated that past management strategies have failed to prevent the infill and pollution of lakes and wetlands. Many key indicators of poor water quality have exhibited sharp increases over the past decade. Urban encroachment into lakes has been curtailed in only four of Dhaka’s 14 districts, with ten districts losing water land cover over the past 66 years. Policymaker and stakeholder opinions on the drivers of lake pollution were highly variable in this study, creating additional roadblocks in implementing and enforcing effective management strategies. It is concluded that the regulatory policies must be implemented to prevent furthermore environmental degradation, while also observing that such policies will be very difficult to enforce under current conditions.

Arsenic and heavy metal pollution in wetland soils from tidal freshwater and salt marshes before and after the flow-sediment regulation regime in the Yellow River Delta, China

Summary Soil samples were collected in tidal freshwater and salt marshes in the Yellow River Delta (YRD), northern China, before and after the flow-sediment regulation. Total concentrations of arsenic (As), cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn) were determined using inductively coupled plasma atomic absorption spectrometry to investigate the characteristics of heavy metal pollution in tidal wetlands before and after the regulation regime. The results demonstrated that marsh soils in both marshes had higher silt and total P contents, higher bulk density and lower sand contents after the flow-sediment regulation; moreover, soil salinity was significantly decreased in the tidal salt marsh. As and Cd concentrations were significantly higher in both marsh soils after the regulation than before, and there were no significant differences in the concentrations of Cu, Pb and Zn measured before and after the regulation. No significant differences in heavy metal concentrations were observed between freshwater and salt marsh soils, either before or after the regulation. Before the regulation regime, soil organic matter, pH and sulfer (S) were the main factors influencing heavy metal distribution in tidal freshwater marshes, whereas for tidal salt marshes, the main factors are soil salinity and moisture, pH and S. However, bulk density and total P became the main influencing factors after the regulation. The sediment quality guidelines and geoaccumulation indices showed moderately or strongly polluted levels of As and Cd and unpolluted or moderately polluted levels of Cu, Pb and Zn; As and Cd pollution became more serious after the regulation. Factor analysis indicated thatthese heavy metals including As were closely correlated and orginated from common pollution sources before the flow-sediment regulation; however, the sources of As and Cd separated from the sources of Cu, Pb and Zn after the regulation regime, implying that the flow-sediment regulation regime contributed to As and Cd accumulation in the YRD.

Evolution of tidal flats in China and ecological exploitation of tidal flat resources

Tidal flats play a tremendous role for solving the problem of land use because of the crisis of population increments. Many coastal countries have carried out reclamation projects near seas in various degrees for a long time. China currently has about 2.13 million hm2 of tidal flats that are mainly scattered in the delta plains and coastal regions near medium- to large-sized rivers. The tidal flats in China are reserves featuring dynamic growth and a capacity for continuous expansion; the tidal flat area undergoes an annual increase of over 20,000 hm2. In recent years, countries around the world have paid much attention to the marine ecological environment and have taken measures to restrict the scale and range of sea reclamation. Although widespread reclamation of tidal flats in China has taken place, such activities have also brought some negative effect: (1) water overdraft, seawater intrusion, (2) tidal gates and channel silting, (3) environment pollution, unbalanced ecosystem, and (4) loss of wetlands and threats to the survival of species. This paper examines the mechanisms associated with tidal flat dynamic growth, and points out that artificial siltation can greatly increase the growth speed of tidal flats, and the actual measured annual siltation thickness may reach 0.5–2.7 m. At present, this paper proposes a theory relating to the ecological exploitation of this ecosystem as follows: (1) the principle of adjustment to local conditions; (2) the principle of three-dimensional distribution; (3) the principle of ecological balance; (4) the principle of green and environmental protection. In practical terms, this dynamic growth may play a significant role in mitigating conflicts relating to land use demands in coastal areas.

The Nile monitor ( Varanus niloticus; Squamata: Varanidae) as a sentinel species for lead and cadmium contamination in sub-Saharan wetlands

Wetland pollution is a matter of concern in sub-Saharan Africa. Though regularly exploited, the Nile monitor ( Varanus niloticus), a large amphibious lizard, is not threatened. This work aims at assessing the value of this varanid as a sentinel species in surveys of environmental contamination by metals. Lead and cadmium quantifications were performed by graphite furnace-atomic absorption spectrophotometry in bone, intestine, kidney, liver and muscle in 71 monitors from three unevenly polluted sites in Mali and Niger, plus a reference site. The effects of sex, size and fat reserves as well as factors related to the sampling strategy (tissue sampled, sampling site) were studied with a mixed linear model. Metal contamination is moderate at the four sites but clear differences nevertheless occur. Lead levels are generally maximal in bone, with a gender-independent median value 320 ng.g −1. Median cadmium concentrations never exceed 70.2 ng.g −1 in females (kidney) and 57.5 ng.g −1 in males (intestine). Such levels should have no detrimental effects on the monitors. Lead and cadmium levels in muscles are generally below 200 and 20 ng.g −1, respectively, and should provoke no health hazard to occasional consumers of monitor meat. Metal organotropisms are consistent with those observed in other studies about Squamates: for lead: bone > [kidney, intestine, liver] > muscle in males and [bone, kidney] > [intestine, liver] > muscle in females; for cadmium: [liver, intestine, kidney] > [bone, muscle] for both genders. Females are more contaminated, especially in their kidneys. In this tissue, median values in ng.g −1 are 129.7 and 344.0 for lead and 43.0 and 70.2 for cadmium, for males and females, respectively. Nile monitors can reveal subtle differences in local pollution by metals; moreover, the spatial resolution of the pollution indication that they give seems to be very sharp. The practical relevance of this new tool is thus validated.

Degradation of diesel-originated pollutants in wetlands by Scirpus triqueter and microorganisms

The wetland ecological environment near Huangpu-Yangtze River Estuary (HYRE) is deteriorating more and more seriously due to oil spills. In this paper, the simulation experiment of degradation was conducted to restore the diesel pollution in soils where the decontaminating potential of indigenous hydrocarbon-degrading microorganisms (HDMs) was evaluated with pot experiments and the co-activation between HDMs and native plant, Scirpus triqueter L.(STL), was investigated. The experimental results indicated that HDMs isolated from HYRE wetland had a degradation effect on diesel pollutants. Within 60 days, the removal ratio of diesel compared with initial amount could be up to 57.27±8.18% in the HDMs inoculated soils at different concentrations of diesel. It was also found that the growth of Scirpus triqueter could enhance the degradation and remediation of diesel pollutants by increasing the populations of microorganisms. A community of STL and HDMs showed a remarkable capability of degrading hydrocarbon components in diesels. Under the combined effects of HDMs and STL (STL-Ms), the removal ratio of diesel pollutants could reach 67.42±8.92%. For example, at 15,000 mg kg −1 diesel concentration the removal ratios in the HDMs and STL-Ms soils were 67.41% and 72.62%, respectively. Moreover, the saturated hydrocarbons were more readily degraded than the aromatic hydrocarbons in treated soils showing a good degradation effect on the range of C 16–C 24 n-alkanes, especially C 19. Positive correlations between microbial populations and diesel removal ratios were observed during the experiment. Microbial populations were found significantly higher in the HDMs soils and rhizosphere soils than in the control ones. The results confirmed that the HDMs and plant improved the biodegradation ability for diesel pollutants and they could be reasonably matched to cure and restore the ecological environment of oil-contaminated wetlands.

Mobilisation of AS and trace metals in saline, acidic Sopolic Technosols: the role of the rhizosphere and flooding conditions

The aim of this work was to study the risk of As and metal pollution in saline wetlands affected by slightly acidic mine wastes, in the presence or absence of a plant rhizosphere, under different flooding regimes. Some guidelines for management will be proposed in order to minimise the risk of metal leaching in metal-polluted salt marshes. A microcosm experiment was conducted to assess the influence of two flooding regimes (continuous or alternating) and the presence of rhizosphere (Sarcocornia fruticosa and Phragmites australis) on the mobilisation of As, Cd, Mn, Pb, Zn and Fe in a slightly acidic, saline Spolic Technosol (pH ≈ 6.5; total concentrations: 551 mg kg−1 As, 5,640 mg kg−1 Pb, 5,299 mg kg−1 Zn). Metal and As pore water concentrations decreased with flooding time (e.g. from approximately 1,700 μg L−1 Cd, 190 mg L−1 Zn and 230 mg L−1 Mn to <400 μg L−1 Cd, <35 mg L−1 Zn, and 50 mg L−1 Mn). A sequential extraction showed that Fe and As were associated mainly with the silicate fraction of the soil, but most of the Mn, Cd, Pb and Zn belonged to the reactive fraction. The rhizosphere of Sarcocornia induced a lower pH, which facilitated higher concentrations of soluble Fe. However, in pots without plants and pots with Phragmites, the combination of Eh and pH led to conditions for formation of siderite, and hence the concentrations of soluble Fe were lower. The concentrations of Mn, Cd, Pb and Zn were lower in vegetated pots, probably due to precipitation of metal carbonates favoured by gas exchange in the rhizosphere. The rhizosphere modified soil conditions during the period of flooding and this affected the dynamics of metals. The high levels of soluble metals pose a risk for leaching, transfer to the food web and toxicity for living organisms. In order to reduce the risks, we propose the water saturation of the soil and the establishments of a plant cover.

Larval escape behavior in anuran amphibians as a wetland rapid pollution biomarker

Biomarkers represent a promising tool as “early-indicators” of potential pollutant impacts, providing the link between individuals’ responses and higher hierarchical levels, such as populations and communities. In this study we use alteration of escape behavior, caused by exposure to typical agrochemicals, as a biomarker of wetland pollution. Tadpoles from three different Iberian anuran species were exposed to sublethal concentrations of copper sulfate and ammonium nitrate for 96 h. Different behavioral indicators were then monitored: number of stimuli to provoke a displacement, distance moved, and nature of escape movement. All species showed similar behavioral alterations. The endpoints of all the three behavioral indices showed deficits leading to a reduction in the capacity and efficiency of escape. The recovery when larvae were moved to clean water was surprisingly fast. After 96 h in recovery, almost all larvae showed normal escape behavior. This indicates that this larval behavioral biomarker can be used as a warning tool in wetland biomonitoring programs in a continuous runoff or spill pollution context.

Quantitative analyses of ammonia-oxidizing Archaea and bacteria in the sediments of four nitrogen-rich wetlands in China

With the rapid development of ammonia-synthesizing industry, the ammonia-nitrogen pollution in wetlands acting as the sink of point and diffuse pollution has been increased dramatically. Most of ammonia-nitrogen is oxidized at least once by ammonia-oxidizing prokaryotes to complete the nitrogen cycle. Current research findings have expanded the known ammonia-oxidizing prokaryotes from the domain Bacteria to Archaea. However, in the complex wetlands environment, it remains unclear whether ammonia oxidation is exclusively or predominantly linked to Archaea or Bacteria as implied by specific high abundance. In this research, the abundance and composition of Archaea and Bacteria in sediments of four kinds of wetlands with different nitrogen concentration were investigated by using quantitative real-time polymerase chain reaction, cloning, and sequencing approaches based on amoA genes. The results indicated that AOA distributed widely in wetland sediments, and the phylogenetic tree revealed that archaeal amoA functional gene sequences from wetlands sediments cluster as two major evolutionary branches: soil/sediment and sediment/water. The bacteria functionally dominated microbial ammonia oxidation in different wetlands sediments on the basis of molecule analysis, potential nitrification rate, and soil chemistry. Moreover, the factors influencing AOA and AOB abundances with environmental indicator were also analyzed, and the results addressed the copy numbers of archaeal and bacterial amoA functional gene having the higher correlation with pH and ammonia concentration. The pH had relatively great negative impact on the abundance of AOA and AOB, while ammonia concentration showed positive impact on AOB abundance only. These findings could be fundamental to improve understanding of the importance of AOB and AOA in nitrogen and other nutrients cycle in wetland ecosystems.

Chemical, biological and physiological indicators of metal pollution in wetlands

Chemical, biological and physiological responses in terrestrial and aquatic plants may be used as biomarkers to monitor contamination in ecosystems. Some plant parameters such as chlorophyll content, photosynthesis, transpiration, metal uptake and metabolism may be used to determine the level of toxic stress in plants. Similarly, the concentrations of metals in soil may be used to establish the levels of pollution. In this review, we present challenge to researchers involved in environmental assessment to use these simple techniques as a basis for establishing guidelines on environmental pollution.

Soil and Water Quality: Integral Components of Watershed Management

Management of agricultural, forested, range, wetland, and urban land plays an integral part in influencing soil and water quality within a watershed. Non-point-source pollution of blue waters, streams, rivers, groundwater, lakes, wetlands, and estuaries is now linked to the management practices used in these ecosystems. In this article, we present a brief overview of the role of soil and water quality in sustainable management of watersheds. Sustainable watershed management will require integration of information from diverse domains (e.g., physical, biogeochemical, economic, social, cultural, and demographic) at multiple spatial and temporal scales, and development of predictive tools across environmental, hydrologic, economic, and social gradients. Soils in the watershed play a unique role in regulating air and water quality, plant productivity, carbon sequestration, production and consumption of greenhouse gases, and climate. Management strategies used to reduce pollutant loads from watersheds should seek to improve soil quality as a first step to improve water quality. Changes in practices by the user are needed to implement new solutions to improve quantity and quality of water resources. Current educational programs in India and other developing countries are not adequate for watershed technology transfer to the user. Linkage between research and outreach must be improved for effective implementation of watershed management practices. Watershed-management plans should be viewed as the starting point, but not the end of management cycle, thus following the concept of adaptive management. Science and policy must function together for watershed management to be successful.

Relative effects of local and landscape factors on wetland algal biomass over a salinity gradient

Wetlands in south-eastern Australia and other arid regions of the world are experiencing increases in salinity due to dryland salinization and climate change. We investigated changes in wetland ecological function, measured as phytoplankton and benthic algal Chl a, over a large salinity gradient (0.047–226 mS cm−1) and in relation to several local water chemistry variables that may be important predictors of algal biomass. We investigated the relative importance of landscape variables that may affect input pollution and hydrology of wetlands at four spatial scales (100, 500, 1,000 and 5000 m). We explored the strength and form of the relationships between algal biomass and local and landscape predictors with emphasis on the effects of local and landscape salinity. We found local variables were more important than landscape variables in influencing algal biomass. We also found salinity of wetlands was not a good predictor of phytoplankton biomass but it did predict benthic algal biomass.

Influence of water quality change in Fu River on Wetland Baiyangdian

Fu River is the only river that has perennial flow into Wetland Baiyangdian and is mainly composed of living sewage and industrial wastewater from Baoding city. Pollutant concentrations were monitored at three sections in the upstream, midstream, and downstream of Fu River and water quality in Wetland Baiyangdian was monitored at seven monitoring sites from 2001 to 2005. Results show that pollutant concentrations in Fu River and pollution load entering Wetland Baiyangdian generally increased during 2001–2005. On average, the concentrations of CODMn and BOD5 increased by 46.5% and 50% from 2001 to 2005 in Fu River and CODMn increased by 17% in Wetland Baiyangdian. The total amount of CODMn and BOD5 entering Wetland Baiyangdian increased from 1630 and 997 t/a to 2243 and 1583 t/a from 2001 to 2005, respectively. Total amount of water within the wetland and non-point source pollution input from surrounding areas also influenced the water quality in the wetland.

Current status of Peruvian Terns Sternula lorata in Perú: threats, conservation and research priorities

SummaryPeruvian Terns Sternula lorata breed in the sand desert plains of the coast of Perú and northern Chile. Because of their long-term population decline, Peruvian Tern is categorized as ‘Endangered’ on the IUCN Red List. The observations that formed the basis for that decision were made in the 1970s and 1990s. In this study, we compile information on distribution, numbers, habitat use and threats of Peruvian Terns that has become available between 2003 and 2008 from 14 localities on the Peruvian coast. Peruvian Tern sites are located between the mangroves of San Pedro de Vice in the north (5o31’S) and the wetlands of Ite in the south (17o56’S). From the 14 locations, five are reported for first time: Virrilá, Eten, Huanchaco, isla Mazorca and Ite. There were only four active breeding sites: Pacasmayo, Paraíso, Pampa Lechuzas and Tres Hermanas-Yanyarina; however, some localities were visited outside the breeding season and should be surveyed between October and February to search for nests. The presence of 283 individuals was confirmed at the 14 sites in an area of approximately 1,388 ha (which represents only 0.35% of the total suitable area for nesting along the Peruvian coast). Thus, the number of Peruvian Terns in Perú should increase with systematic surveys. Here for the first time we report the importance of wetlands for the Peruvian Terns (43% of the sightings occurred in this habitat). Wetlands can offer optimal conditions for feeding, but the cost of using them is becoming higher with a sharp increase of human expansion into coastal areas and urban development around wetlands. We identified the following threats affecting Peruvian Terns on their feeding and breeding grounds: 1) recreational activities; 2) off-road driving by fishermen and tourists; 3) wetland pollution and water use for irrigation; 4) conversion of desert plains to agricultural land; 5) management of wetland water levels; 6) presence of feral cats and dogs, and 7) oil exploration on the desert plains. These adverse factors can be eradicated by the protection of tern sites and public awareness and education. Conservation actions, monitoring and research priorities are suggested.

Effects of oil on internal gas transport, radial oxygen loss, gas films and bud growth in Phragmites australis.

Oil pollution of wetlands is a world-wide problem but, to date, research has concentrated on its influences on salt marsh rather than freshwater plant communities. The effects of water-borne light oils (liquid paraffin and diesel) were investigated on the fresh/brackish wetland species Phragmites australis in terms of routes of oil infiltration, internal gas transport, radial O(2) loss (ROL), underwater gas films and bud growth. Pressure flow resistances of pith cavities of nodes and aerenchyma of leaf sheaths, with or without previous exposure to oil, were recorded from flow rates under applied pressure. Convective flows were measured from living excised culms with oiled and non-oiled nodes and leaf sheaths. The effect of oil around culm basal nodes on ROL from rhizome and root apices was measured polarographically. Surface gas films on submerged shoots with and without oil treatment were recorded photographically. Growth and emergence of buds through water with and without an oil film were measured. Internodes are virtually impermeable, but nodes of senesced and living culms are permeable to oils which can block pith cavity diaphragms, preventing flows at applied pressures of 1 kPa, natural convective transport to the rhizome, and greatly decreasing ROL to phyllospheres and rhizospheres. Oil infiltrating or covering living leaf sheaths prevents humidity-induced convection. Oil displaces surface gas films from laminae and leaf sheaths. Buds emerge only a few centimetres through oil and die. Oil infiltrates the gas space system via nodal and leaf sheath stomata, reducing O(2) diffusion and convective flows into the rhizome system and decreasing oxygenation of phyllospheres and rhizospheres; underwater gas exchange via gas films will be impeded. Plants can be weakened by oil-induced failure of emerging buds. Plants will be most at risk during the growing season.

The importance of unmanaged coastal wetlands to waterbirds at coastal Ghana

AbstractGhana's 550 km coastline has about 100 wetlands out of which five large ones are managed as Ramsar sites, the rest being unmanaged. Recent pollution and misuse of unmanaged wetlands have necessitated a study into their roles in the support of waterbirds. Waterbird survey on four wetlands between September 2005 and April 2006 revealed that 51 waterbird species make use of the managed compared to 44 in the unmanaged wetlands. Average numbers of waterbirds were higher on the managed wetlands (10,510 ± 4862) than on the unmanaged wetlands (1348 ± 602) (P &lt; 0.05) but mean population density of waterbirds (n/ha) was the same for both the managed (1860 ± 310) and unmanaged (1400 ± 220) (P &gt; 0.05) wetlands. The population densities of waterbirds belonging to guilds 1, 5 and 7 were significantly higher on the managed wetlands (P &lt; 0.05). In contrast, guilds 2 and 4 have significantly higher population densities on the unmanaged wetlands while the population density of guild 3 was the same (P &gt; 0.05). There was an indication that during mid and late periods of the nonbreeding season, the unmanaged wetlands altogether may support a larger number of waterbirds belonging to guilds 2, 3 and 4 than the five managed wetlands.