Integrated rice-fish culture: Coupled production saves resources

Rice is a key component in global food security, as it is the main ingredient in the daily diets of around 3 billion people, especially in Asia. Like all agricultural production, rice cultivation depends on scarce natural resources. This article briefly outlines the utilization of land and water in rice production, and suggests an approach for optimizing use efficiency, namely through the combination of rice and fish culture. The authors argue that the utilization of land and fresh water is optimized through integrated and complementary production of rice and fish — two basic foods items in daily local diets. The article reviews currently available scientific literature on integrated rice‐fish systems. Rice‐fish culture systems are briefly characterized, and respective yield potential and interactions between rice and fish are discussed. Results of socio‐economic surveys regarding the adoption of integrated rice‐fish culture are summarized. The article also reviews literature on the impact of fish culture on rice field ecology as outlined in studies on weed infestation, insect populations, and greenhouse gas emissions. The article concludes that rice‐fish culture can be an option to help rice producing countries keep pace with soaring domestic demand for food, especially fish. Integrated rice and fish culture optimizes the benefits of scarce land and water resources through complementary use, and exploits the synergies between fish and plant.     

CONTROL OF SUSPENDED SOLIDS AND PHYTOPLANKTON WITH FISHES AND A MUSSEL1

ABSTRACT: Filtering efficiency of the fathead minnow (Pimephales promelas), gizzard shad (Dorosoma cepedianum), carp (Cyprinus carpio), and a freshwater mussel (Elliptio coinpianata) was measured in field and laboratory trials to assess the ability of each species to control phytoplankton and suspended solid densities. All fish species tested were ineffective filterers and generally increased, rather than suppressed, algal and suspended solid concentrations. Filtering efficiencies of fish varied between -354 and 84 percent, depending on the size, shape, abundance, palatability, composition, and resistance to digestion of the particles. Because of poor filtering abilities, unpredictable feeding habits, and sensitivity to stress, the fish species examined are not effective biological controls in waste lagoons. In contrast, the freshwater mussel Elliptio was a highly effective control organism, averaging 66 percent filtering efficiency over a wide size range of algal and suspended particles. Filtration efficiency was positively correlated with mussel density. Elliptio was efficient at filtering small particles, which are particularly difficult to remove. Mean filtration rates ranged from 53 to 134 ml/mussel/h depending on the algal species consumed and algal densities (range 50–180,000 cells/ml) and 3 mg/L/mussel/h on suspended solids (range 14 to 112 mg/L). Water clarification was facilitated by both direct consumption and pseudofeces deposition. Elliptio and probably other mussel species can effectively control algae and suspended solids in wastewater lagoons and eutrophic lakes, if environmental conditions, especially dissolved oxygen levels, are suitable (>5 mg/L) for their survival.     

Securing water for people, crops, and ecosystems: New mindset and new priorities

A fundamentally new approach to water and human development will be needed during this new century if we are to secure sufficient freshwater to meet the needs of some 9 billion people while at the same time protecting the critical ecosystem services upon which the human economy depends. Signs of unsustainable water use — including falling water tables, shrinking lakes, and the drying up of rivers and streams — are widespread and spreading. In many regions, greater modification and appropriation of freshwater systems for human purposes will yield greater costs than benefits and create the risk of irreversible losses of species and ecosystem services. A new mindset is needed to guide water use and management in this new century, one that views the human water economy as a subset of nature's water economy. Living within nature's limits will require that societies satisfy the basic needs of people and ecosystems before non-essential water demands are met. It will require on the order of a doubling of water productivity. And it will require stronger institutions to encourage equitable sharing of water to alleviate tensions within and between countries.     

应用体内和体外方法评价原油水溶性组分和原油污染的地表水对淡水生物的内分泌干扰潜力

目前关于原油对淡水水生脊椎动物内分泌信号的潜在影响的认知有限。本文以非洲爪蟾(爪蟾属,X. laevis)蝌蚪和莫桑比克罗非鱼幼鱼(口孵非鲫属,O. mossambicus)为研究对象,选择风化原油和未风化提炼后的原油这2种原油的水溶性组分(WAFs)进行暴露实验,选择出可作为内分泌信号改变的生物标志物的基因,对其表达进行了研究。此外,将X. laevis蝌蚪暴露于靠近地下石油库的地表水中,对上述基因表达做了定量分析。利用重组酵母对原油、原油水溶性组分和地表水的(抗)雌激素和(抗)雄激素性进行了评价。在X. laevis对2种原油WAFs的响应中,甲状腺激素受体β表达均显著下调,而另一种与甲状腺相关的基因,2型脱碘酶,在O. mossambicus暴露于高浓度的原油WAF时被上调。此外,这2种WAFs都改变了与脂肪生成相关的过氧化物酶体增殖物激活受体γ在X. laevis中的表达。原油和WAFs在体外表现出抗雌激素和抗雄性激素的活性。然而,O. mossambicus雄激素受体2作为唯一一个代表生殖系统的基因,受到WAF暴露的影响显著。在地表水样品中发现了雌激素、抗雌激素和抗雄激素的作用;但是,在暴露于地表水的X. laevis中没有观察到任何基因表达的明显变化。在所用的2种模式生物以及2种原油中,响应各不相同。尽管如此,这些数据提供了证据证明原油污染可能会因内分泌信号转变对淡水鱼和两栖动物的健康造成不利影响。
精选自Truter, J. C., van Wyk, J. H., Oberholster, P. J., Botha, A.-M. and Mokwena, L. M. (2017), An evaluation of the endocrine disruptive potential of crude oil water accommodated fractions and crude oil contaminated surface water to freshwater organisms using in vitroand in vivo approaches. Environmental Toxicology and Chemistry, 36: 1330–1342. doi: 10.1002/etc.3665
详情请见http://onlinelibrary.wiley.com/doi/10.1002/etc.3665/full
     

Probabilistic distribution coefficients (Kds) in freshwater for radioisotopes of Ag,Am, Ba,Be, Ce,Co, Cs,I, Mn,Pu, Ra,Ru, Sb,Sr and Th – implications for uncertainty analysis of models simulating the transport of radionuclides in rivers

The objective of this study was to provide operational probability density functions (PDFs) for distribution coefficients (K_ds) in freshwater, representing the partition of radionuclides between the particulate and the dissolved phases respectively. Accordingly, the K_d variability should be considered in uncertainty analysis of transport and risk assessment models. The construction of PDFs for 8 elements (Ag, Am, Co, Cs, I, Mn, Pu and Sr) was established according to the procedure already tested in Durrieu et al. [2006. A weighted bootstrap method for the determination of probability density functions of freshwater distribution coefficients (K_ds) of Co, Cs, Sr and I radioisotopes. Chemosphere 65 (8), 1308–1320]: (i) construction of a comprehensive database where K_ds values obtained under various environments and parametric conditions were collected; (ii) scoring procedure to account for the ‘quality’ of each datapoint (according to several criteria such as the presentation of data (e.g. raw data vs mean with or without replicates), contact time, pH, solid-to-liquid ratio, expert judgement) in the construction of the PDF; (iii) weighted bootstrapping procedure to build the PDFs, in order to give more importance to the most relevant datapoints. Two types of PDFs were constructed: (i) non-conditional, usable when no knowledge about the site of concern is available; (ii) conditional PDFs corresponding to a limited range of parameters such as pH or contact time; conditional PDFs can thus be used when some parametric information is known on the site under study. For 7 other radionuclides (Ba, Be, Ce, Ra, Ru, Sb and Th), a simplified procedure was adopted because of the scarcity of data: only non-conditional PDFs were built, without incorporating a scoring procedure.     

Comparative Salinity Tolerance of Three Indigenous Tropical Freshwater Cladoceran Species; Moinodaphnia Macleayi, Ceriodaphnia Rigaudii and Diaphanosoma Brachyurum

The acute salinity tolerance of three tropical freshwater cladoceran species, M. macleayi, C. rigaudii and D. brachyurum was determined. The existence of these species represented new records for Trinidad and Tobago, a tropical Caribbean island. It has a large oil based industry, in which, the primary effluent (saline produced water) is discharged directly into many freshwater systems. Cladoceran species are used routinely in temperate regions, to assess the impacts of chemicals and effluents in freshwater systems. However, relatively few studies have assessed the salinity tolerance of these organisms. Test organisms were assayed using seven salinity treatments (0, 1, 3, 5, 10, 15, 20, 25‰) prepared by volumetrically mixing natural filtered seawater with dilution water. C. rigaudii had a 48 h LC50 of 1.6‰, M. macleayi 1.5‰ and D. brachyurum <1‰. The CSmax (critical salinity maximum) for C. rigaudii and M. macleayi was 3‰ after 48 h, compared to 1‰ for D. brachyurum. There was no salinity value at which there was 100% survival. The resulting salinity response curve was a straight line which indicated that each species was intolerant of salt. Consequently, any of these can be considered as a representative freshwater organism for toxicity testing in Trinidad and Tobago.     

Elemental concentrations in air, water, and aquatic biota in two rural provinces in northern Vietnam

The present study on environmental pollution in northern Vietnam investigates elemental concentrations in fine particulate matter (PM_2.5), freshwater, and aquatic biota at two sites with differing levels of industrial activities. An Thin is situated 47 km east of Hanoi in the neighbourhood of a coal combustion power plant, whereas the reference site, Duy Minh, is situated in the agricultural province of Ha Nam, 40 km south of Hanoi. Elemental concentrations were analysed using energy-dispersive X-ray fluorescence, total reflection X-ray fluorescence, and graphite furnace atomic absorption spectro-metry. All investigated elements in fine particles (PM_2.5) had significantly higher concentrations in An Thin, thus identifying the air at this site as polluted. In contrast to the aerosol samples, elemental concentrations as well as quantitative differences between the sampling sites were low in freshwater and biota, indicating that the impact of atmospheric deposition was limited.     

近年渤海与黄海北部沿岸底栖贝类体内微污染物的分布特征

根据近几年的海洋常规监测数据,确定渤海及黄海北部沿岸底柄贝类体内典型微污染物的含量及其空间分布.结果表明,在36%以上的站点中,贝类体内石油烃含量超过国家海洋生物质量第1类标准(15μg/g,湿重,下同),尤其是大连湾和河北新村附近海域贝类体内含量甚至高出第Ⅲ类标准(80μg/g,以湿重计),并且,近年来大部分海域贻贝...     

Freshwater Mussel Population Status and Habitat Quality in the Clinch River,Virginia and Tennessee,USA: A Featured Collection

The Clinch River of southwestern Virginia and northeastern Tennessee is arguably the most important river for freshwater mussel conservation in the United States. This featured collection presents investigations of mussel population status and habitat quality in the Clinch River. Analyses of historic water‐ and sediment‐quality data suggest that water column ammonia and water column and sediment metals, including Cu and Zn, may have contributed historically to declining densities and extirpations of mussels in the river's Virginia sections. These studies also reveal increasing temporal trends for dissolved solids concentrations throughout much of the river's extent. Current mussel abundance patterns do not correspond spatially with physical habitat quality, but they do correspond with specific conductance, dissolved major ions, and water column metals, suggesting these and/or associated constituents as factors contributing to mussel declines. Mussels are sensitive to metals. Native mussels and hatchery‐raised mussels held in cages in situ accumulated metals in their body tissues in river sections where mussels are declining. Organic compound and bed‐sediment contaminant analyses did not reveal spatial correspondences with mussel status metrics, although potentially toxic levels were found. Collectively, these studies identify major ions and metals as water‐ and sediment‐quality concerns for mussel conservation in the Clinch River.