Mercury bioaccumulation and trophic transfer in sympatric snapper species from the Gulf of Mexico.

Consumption of marine fish is a major route of toxic methyl mercury (MeHg) exposure to ocean apex predators and human populations. Here we explore the influence of trophic structure on total mercury (Hg) accumulation in red snapper (RS, Lutjanus campechanus) and gray snapper (GS, Lutjanus griseus) from the coastal Louisiana region of the Gulf of Mexico, west of the Mississippi River. The objectives of this investigation were to: (1) determine the effectiveness of the use of offshore recreational fishing charter boats and marinas as sources of fish samples and (2) compare species differences in Hg bioaccumulation, trophic position, and carbon sources. Our data show that length-normalized Hg concentrations (> or = 97% as MeHg in tissue of both species) were 230% greater in GS in comparison to RS collected from the same general area. Stable C and N isotope signatures (delta15N and delta13C) indicate that GS occupy a slightly higher trophic position (approximately 30% of one trophic position higher) on the Gulf food web in comparison to RS and that GS appear to incorporate higher trophic positioned prey, continually and at smaller sizes. Mercury was strongly correlated with combined delta15N and delta13C in pooled species data, arguing that most of the substantial difference in Hg bioaccumulation between RS and GS can be explained by modest differences in their trophic position and, to a lesser degree, carbon sources, which had low variation and high overlap among species. These observations demonstrate that even minor to moderate differences in trophic position and food habits in sympatric species can create relatively large differences in bioaccumulation regimes and underscores the importance of quantitative characterization of trophic structure in marine MeHg bioaccumulation studies.     

Managing Watershed Externalities in India: Theory and Practice

Watershed development is the focus of poverty alleviation programs in rural India. Watershed projects aim to solve problems of externalities, but they also create their own externalities, which cause uneven distribution of costs and benefits that undermine project objectives and harm the poor. Numerous approaches exist to internalize externalities, including awareness creation, moral suasion, investment subsidies, regulatory limits and fines, indirect benefits, mergers, and recent innovations like payment for environmental services and cap and trade. These can be judged on several criteria; the best approach would solve the problem cost effectively and help or at least not hurt poor people. Watershed projects in India were examined to identify the approaches taken to internalize watershed externalities. Investment subsidies and indirect employment benefits are the least effective approaches theoretically, but they are the most commonly applied, most likely because they are easy to administer and bring popular short term gains. Some theoretically favorable approaches that have been used elsewhere, such as payment for environmental services, may not work as well in India due to high transaction costs. However, one key innovation that easily could be applied in India is to make investment subsidies contingent on performance. Legal support and property rights reform would be needed for other favorable approaches.     

A Multilevel Modeling Approach to Assessing Regional and Local Landscape Features for Lake Classification and Assessment of Fish Growth Rates

The ecoregion and watershed frameworks are landscape-based classifications that have been used to group waterbodies with respect to measures of community structure; however, they have yet to be evaluated for grouping lakes for demographic characteristics of fish populations. We used a multilevel modeling approach to determine if variability in mean fish length at age could be partitioned by ecoregions and watersheds. For the ecoregions analysis, we then examined if within-ecoregion variability could be explained by local water quality and lake morphometry characteristics. We used data from agency surveys conducted during 1974-1984 for age 2 and 3 fish of seven common warm and coolwater fish species. Variance in mean length at age between ecoregions for all species was not significant, and between-watershed variance estimates were only significant in 3 out of 14 analyses; however, the total amount of variation between watersheds was very small (ranging from 1.8% to 3.7% of the total variance), indicating that ecoregions and watersheds were ineffective in partitioning variability in mean length at age. Within ecoregions, water quality and lake morphometric characteristics accounted for 2%-23% of the variation in mean length at age. Measures of lake productivity were the most common significant covariates, with mean length at age increasing with increasing lake productivity. Much of the variability in mean length at age was not accounted for, suggesting that other local factors such as biotic interactions, fish density, and exploitation are important. The results indicate that the development of an effective regional framework for managing inland lakes will require a substantial effort to understand sources of demographic variability and that managers should not rely solely on ecoregions or watersheds for grouping lakes with similar growth rates.     

Fully automated FISH examination of amniotic fluid cells

Objective Fluorescence in situ hybridization (FISH) analysis has become a valuable adjunct in cytogenetics, providing a rapid screen for common chromosome abnormalities that is particularly helpful in prenatal diagnosis. FISH analysis using standard microscopy is expensive and labor intensive, requiring both a high skill level and subjective signal interpretation. A reliable fully automated system for FISH analysis could improve laboratory efficiency and potentially reduce errors and costs. Methods The efficacy of an automated system was compared to standard manual FISH analysis. Two sets of slides were generated from each of 152 amniotic fluid samples. Following hybridization with a standard panel of five chromosome FISH probes, one set of slides was evaluated using manual microscopy. The other set was evaluated using an automated microscopy system. Results A diagnostic outcome was obtained for all 152 samples using manual microscopy and for 146 of 152 (96%) samples using automated microscopy. Three cases of aneuploidy were detected. For those samples for which a diagnostic outcome was determined by both manual and automated microscopy, 100% concordance was observed. All FISH analysis results were confirmed by karyotype. Conclusion These data suggest that an automated microscopy system is capable of providing accurate and rapid enumeration of FISH signals in amniocytes. Copyright © 2007 John Wiley & Sons, Ltd.     

Drought-induced sulphate release from a wetland in south-central Ontario

Increased sulphate (SO₄) export from wetlands following summer droughts in central Ontario, Canada has been associated with the delayed chemical recovery of downstream surface waters following decreased sulphur (S) emissions. Prolonged summer droughts result in a decrease or cessation of stream flow, declines in wetland water table level and oxidation of reduced S compounds to SO₄, which is subsequently flushed into drainage streams when stream flow resumes. Sulphate input-output budget calculations (1983–1995 and 1999–2001) at a conifer Sphagnum swamp in the Plastic Lake catchment, indicate that SO₄ is retained in most years but is exported on a net basis following particularly severe summer droughts that result in the cessation of stream flow for more than 54 days (95% CI: 41–72 days). Hindcast calculations using long-term (1916–2000) stream discharge records from a nearby station indicate that while droughts occurred frequently in south-central Ontario over the past 85 years, sufficiently dry conditions to cause net SO₄ export occurred in only18 of the past 85 years, and indicate a cumulative positive SO₄ balance for the swamp (i.e. net SO₄ retention). Furthermore, the S pool at the Plastic Lake swamp has been estimated to be ∼1500 kg S/ha in the upper 40 cm peat layer, which is large compared to the amount of net SO₄ export that occurs even in years with particularly dry summers (e.g. −43 kg S/ha in 1987/88). Together, these data suggest that the wetland S pool at Plastic Lake has not been depleted by previous droughts and will continue to sustain episodic drought-related SO₄ export for the foreseeable future.     

Locally-calibrated light transmission visualization methods to quantify nonaqueous phase liquid mass in porous media

Five locally-calibrated light transmission visualization (LTV) methods were tested to quantify nonaqueous phase liquid (NAPL) mass and mass reduction in porous media. Tetrachloroethylene (PCE) was released into a two-dimensional laboratory flow chamber packed with water-saturated sand which was then flushed with a surfactant solution (2% Tween 80) until all of the PCE had been dissolved. In all the LTV methods employed here, the water phase was dyed, rather than the more common approach of dyeing the NAPL phase, such that the light adsorption characteristics of NAPL did not change as dissolution progressed. Also, none of the methods used here required the use of external calibration chambers. The five visualization approaches evaluated included three methods developed from previously published models, a binary method, and a novel multiple wavelength method that has the advantage of not requiring any assumptions about the intra-pore interface structure between the various phases (sand/water/NAPL). The new multiple wavelength method is also expected to be applicable to any translucent porous media containing two immiscible fluids (e.g., water-air, water-NAPL). Results from the sand-water-PCE system evaluated here showed that the model that assumes wetting media of uniform pore size (Model C of Niemet and Selker, 2001) and the multiple wavelength model with no interface structure assumptions were able to accurately quantify PCE mass reduction during surfactant flushing. The average mass recoveries from these two imaging methods were greater than 95% for domain-average NAPL saturations of approximately 2.6x10(-2), and were approximately 90% during seven cycles of surfactant flushing that sequentially reduced the average NAPL saturation to 7.5x10(-4).     

Ammonia assessment from agriculture: U.S. status and needs

Recent studies suggest that human activities accelerate the production of reactive nitrogen on a global scale. Increased nitrogen emissions may lead to environmental impacts including photochemical air pollution, reduced visibility, changes in biodiversity, and stratospheric ozone depletion. In the last 50 yr, emissions of ammonia (NH3), which is the most abundant form of reduced reactive nitrogen in the atmosphere, have significantly increased as a result of intensive agricultural management and greater livestock production in many developed countries. These agricultural production practices are increasingly subject to governmental regulations intended to protect air resources. It is therefore important that an accurate and robust agricultural emission factors database exist to provide valid scientific support of these regulations. This paper highlights some of the recent work that was presented at the 2006 Workshop on Agricultural Air Quality in Washington, D.C. regarding NH3 emissions estimates and emission factors from agricultural sources in the U.S. and Europe. In addition, several best management practices are explored as the scientific community attempts to maximize the beneficial use of reactive nitrogen while simultaneously minimizing negative environmental impacts.     

Release of nitrogen and trace metal species from field stacked biosolids

Concerns over elevated nitrate (NO3-) levels found in groundwater near former biosolid stockpiling locations resulted in the Maine Department of Environmental Protection (MDEP) imposing stricter regulations governing the stockpiling of biosolids in October 2002. The goals of this study were to measure the amount and speciation of nitrogen (N) and trace metals leaving stockpiled biosolids and travelling through the soil column. The biosolids were placed on plastic-lined cells to collect all leachate. Ammonium (NH4+), ranging from 2000 to 4900 mg L(-1), was the dominant N species (90% of total N) in the leachate from the Class B lime-stabilized biosolids in the lined cell experiment. Nitrate (NO3-) and nitrite (NO2-) concentrations were negligible, remaining below 0.25 and 0.1 mg L(-1), respectively. Dissolved organic carbon (DOC) concentrations as high as 8900 mg L(-1) and chemical oxygen demand (COD) as high as 37 000 mg L(-1) were measured in the leachate leaving the lined cell. Fifteen zero-tension pan lysimeters (ZTP-lysimeter) were installed in a 90 m2 plot at depth intervals of 30, 60, and 100 cm. Leachate passing through the soil column underlying the biosolids stockpile was collected in the ZTP-lysimeters. The average ZTP-lysimeter NH4+ concentrations ranged from 1400 mg L(-1) at 60 cm depth to 145 mg L(-1) at 90 cm depth. The average ZTP-lysimeter DOC concentrations ranged from 2000 mg L(-1) at 60 cm to 525 mg L(-1) at 90 cm. Trace metal determinations of the leachate collected from the lined cell and ZTP-lysimeters showed arsenic loading rates exceeded the state limits of 0.5 kg ha(-1) year(-1) by an order of magnitude. Arsenic concentrations were in excess of several thousand milligrams per litre in the lined-cell leachate and several hundred milligrams per litre in the ZTP-lysimeters as deep as 90 cm under the biosolid stockpile. Phosphorus, iron and manganese in excess of several thousand milligrams per litre were observed in both the lined-cell leachate and ZTP-lysimeters. Significant concentrations of other trace metals were found at depth in the zero-tension ZTP-lysimeter plot. Trace metals were largely mobilized by the DOC from the biosolids and due to the presence of anaerobic environment, especially in the underlying soil.     

Environmental impact of aquaculture and countermeasures to aquaculture pollution in China

GOAL, SCOPE AND BACKGROUND: Aquaculture activities are well known to be the major contributor to the increasing level of organic waste and toxic compound in the aquaculture industry. Along with the development of intensive aquaculture in China, concerns are evoked about the possible effects of ever-increasing aquaculture waste both on productivity inside the aquaculture system and on the ambient aquatic ecosystem. Therefore, it is apparent that appropriate waste treatment processes are needed for sustaining aquaculture development. This review aims at identifying the current status of aquaculture and aquaculture waste production in China. MAIN FEATURES: China is the world's largest fishery nation in terms of total seafood production volume, a position it has maintained continuously since 1990. Freshwater aquaculture is a major part of the Chinese fishery industry. Marine aquaculture in China consists of both land-based and offshore aquaculture, with the latter mostly operated in shallow seas, mud flats and protected bays. The environmental impacts of aquaculture are also striking. RESULTS: Case studies on pollution hot spots caused by aquaculture have been introduced. The quality and quantity of waste from aquaculture depends mainly on culture system characteristics and the choice of species, but also on feed quality and management. Wastewater without treatment, if continuously discharged into the aquatic environment, could result in remarkable elevation of the total organic matter contents and cause considerable economy lost. Waste treatments can be mainly classified into three categories: physical, chemical and biological methods. DISCUSSION: The environmental impacts of different aquaculture species are not the same. New waste treatments are introduced as references for the potential development of the waste treatment system in China. The most appropriate waste treatment system for each site should be selected according to the sites' conditions and financial status as well as by weighing the advantages and disadvantages of each system. Strategies and perspectives for sustainable aquaculture development are proposed, with the emphasis on environmental protection. CONCLUSIONS: Negative effects of waste from aquaculture to aquatic environment are increasingly recognized, though they were just a small proportion to land-based pollutants. Properly planned use of aquaculture waste alleviates water pollution problems and not only conserves valuable water resources but also takes advantage of the nutrients contained in effluent. It is highly demanding to develop sustainable aquaculture which keeps stocking density and pollution loadings under environmental capacity. RECOMMENDATIONS AND PERSPECTIVES: The traditional procedures for aquaculture waste treatment, mainly based on physical and chemical means, should be overcome by more site-specific approaches, taking into account the characteristics and resistibility of the aquatic environment. Further research needs to improve or optimize the current methods of wastewater treatment and reuse. Proposed new treatment technology should evaluate their feasibility at a larger scale for practical application.     

Protection of wetlands as a strategy for reducing the spread of avian influenza from migratory waterfowl

Highly pathogenic avian influenza (HPAI) H5N1 has led to the death or destruction of millions of domesticated and wild birds and caused hundreds of human deaths worldwide. As with other HPAIs, H5N1 outbreaks among poultry have generally been caused by contact with infected migratory waterfowl at the interface of wildlands and human-dominated landscapes. Using a case–control epidemiological approach, we analyzed the relation between habitat protection and H5N1 outbreaks in China from 2004 to 2017. We found that while proximity to unprotected waterfowl habitats and rice paddy generally increased outbreak risk, proximity to the most highly protected habitats (e.g., Ramsar-designated lakes and wetlands) had the opposite effect. Protection likely involves two mechanisms: the separation of wild waterfowl and poultry populations and the diversion of wild waterfowl from human-dominated landscapes toward protected natural habitats. Wetland protection could therefore be an effective means to control avian influenza while also contributing to avian conservation.