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This article discusses environmental sustainability in aquaculture and its contribution to poverty alleviation, based on field studies in Sri Lanka and the Philippines. The aquaculture practices studied are the monoculture of the black tiger prawn (Penneaus monodon) and milkfish (Chanos chanos) and the polyculture of the two species together with the mud crab (Scylla serrata). Factors affecting economic viability, social equity and environmental impacts in aquaculture are discussed and used to illuminate local and regional differences between aquaculture in Sri Lanka and the Philippines. Findings indicate that the most significant difference is the level of participation by local people (i.e., people originating ≤10 km away from the farm location). In the Philippines, 84 % of the people involved in aquaculture are locals, whereas in Sri Lanka, 55% are outsiders. Whether differences between the two areas can be explained by analyzing regional conditions, which might have resulted in different aquaculture practices, is discussed. In Sri Lanka, semi-intensive shrimp monoculture is currently the most common practice, whereas in the Philippines, extensive shrimp/fish polyculture is more common. Previous studies, as well as fieldwork, indicate that extensive culture practices reduce environmental impacts and benefit local people more. Sustainability in aquaculture is, however, also dependent on the extent of mangrove conversion into ponds. As such, extensive and locally owned farms do not necessarily result in an all but sustainable situation. Keeping this in mind, it is discussed if extensive polyculture practices might result in a more sustainable aquaculture, both environmentally and socioeconomically.  相似文献   
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Seasonal variation in settlement and spiculation of sponge larvae   总被引:2,自引:0,他引:2  
A settlement study, based in the Hauraki Gulf, Auckland, New Zealand, has revealed 3 different seasonal reproductive patterns among Demospongiae. Species which settled on our substrates can be divided into summer settlers, winter settlers, or all-year-round settlers. The composition of these groups is given, and the affinities and habitats of the constituent species are commented on. Variation in aspects of the spicule complement have been observed and discussed for three species: Mycale macilenta, Microciona coccinea and Ectyomyxilla kerguelensis.  相似文献   
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Free amino acid patterns and the classification of the Demospongiae   总被引:1,自引:0,他引:1  
An investigation of the free amino acid patterns of 67 species representing 50 genera of West Indian Demospongiae has been undertaken to examine the value of this biochemical approach in adding another parameter to phylogenetic inquiries. Two-dimensional thin-layer electrophoresis and chromatography were used to separate mixtures of naturally occurring ninhydrin-positive compounds. Individual components were identified as far as possible, and the fingerprints or patterns of the species studied were used as a basis for evaluating relationships. The subclass Ceractinomorpha is a relatively homogeneous group, with free amino acid patterns characterized by a consistent representation of protein amino acids and by the absence of compounds other than taurine and hypotaurine in the neutral region of the chromatogram. Two variants of this general pattern can be recognized, one found in the orders Dictyoceratida and Poecilosclerida, the other occurring in the order Haplosclerida and the family Halichondriidae of the order Halichondrida. Unexpected results within this subclass are the wide separation of the dictyoceratid families Spongiidae and Verongiidae, the anomolous patterns of the genera Agelas and Iotrochota and of the family Callyspongiidae, and the suggestive affinities of the family Hymeniacidonidae with the order Hadromerida. The subclass Tetractinomorpha appears to represent a polyphyletic assemblage in which 5 recognizable patterns can be distinguished. These represent the orders Homosclerophorida, Choristida, Spirophorida, Hadromerida and Axinellida. Of interest are the suggestions that the order Choristida is in itself a heterogeneous group, and that certain genera now placed in the order Axinellida may in fact be more closely related to the Poecilosclerida.  相似文献   
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Portovelo-Zaruma, Ecuador is an artisanal and small-scale gold mining (ASGM) region with approximately 6000 gold miners working with mercury and cyanide. Although artisanal gold mining (AGM) has taken place in Portovelo-Zaruma for centuries, highly mechanized small-scale gold mining (SGM) processing plants capable of increased throughput began being built in the 1990s. While there are benefits associated with ASGM, there are also negative impacts experienced by the miners and the surrounding communities. To take advantage of ASGM as a poverty-alleviating mechanism while reducing unwanted externalities, the cumulative impacts must be understood. Numerous challenges to measuring, monitoring, and addressing ASGM impacts result from the complexity of the impacts themselves, the nature of the gold mining as an informal industry, and the shortfalls in the current regulatory framework. These are discussed in the context of ongoing, unresolved issues including efforts to address trans-boundary water pollution, management of mining waste, and conflicts regarding priorities, ambiguities, and enforcement of existing regulations and policies. Internationally, interventions to address both AGM and SGM impacts have typically focused almost exclusively on technological changes through the elimination of mercury use. Our analysis suggests that to better address ASGM and their cumulative impacts in Ecuador, it will be beneficial to revisit the legal definitions of AGM and SGM. Additionally, promotion of information-based strategies including educational outreach programs and cross-scale and cross-level mitigation methods may also be beneficial. The success of these strategies to reduce ASGM-related cumulative impacts will depend on sufficient funding and the commitment of stakeholders.  相似文献   
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One goal of the Swedish survey project is to discover possible sources of PCDD/F. Bottom sediment and pike were sampled at various sites near different types of industries along the coast line of two lakes and one river. The results show background levels of PCDD/F in some lakes which can only be explained by atmospheric input. In some lakes paper mill emissions of chlorinated PCDD/F give high levels of local contamination (≈1 ng/g IG) within short distances (<1 km) from the source. PCDD/F from paper mill effluents are transported long distances and traces can be detected over the entire lake area. The PCDD/F levels in pike are correlated with levels in the underlying sediment.  相似文献   
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Thirty species of temperate-zone sponges representative of all orders of the Demospongiae have been tested for antibacterial activity. The results indicate the following: that a higher percentage of temperate than tropical species produced active extracts (87% as opposed to 58%); that sponge extracts more frequently inhibited the growth of marine bacteria than they did non-marine bacteria (76.5% compared to 56%); that 46.5% of the extracts tested inhibited growth of Gram-negative bacteria while only 6.5% inhibited growth of Gram-positive bacteria. There is no obvious correlation between incidence of antibacterial activity and latitude of occurrence, systematic group or growth form of the sponge. It is suggested that antibacterial agents produced by sponges may have a role in enhancing the efficiency with which sponges retain bacterial food.  相似文献   
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In 2000, Florida's fast-growing hard clam aquaculture industry became eligible for federal agricultural crop insurance through the US Department of Agriculture, but the responsibility for identifying the cause of mortality remained with the grower. Here we describe the continuous water quality monitoring system used to monitor hard clam aquaculture areas in Florida and show examples of the data collected with the system. Systems recording temperature, salinity, dissolved oxygen, water depth, turbidity and chlorophyll at 30 min intervals were installed at 10 aquaculture lease areas along Florida's Gulf and Atlantic coasts. Six of these systems sent data in real-time to a public website, and all 10 systems provided data for web-accessible archives. The systems documented environmental conditions that could negatively impact clam survival and productivity and identified biologically relevant water quality differences among clam aquaculture areas. Both the real-time and archived data were used widely by clam growers and nursery managers to make management decisions and in filing crop loss insurance claims. While the systems were labor and time intensive, we recommend adjustments that could reduce costs and staff time requirements.  相似文献   
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One of the fastest growing areas of natural gas production is coal bed methane (CBM) due to the large monetary returns and increased demand for energy from consumers. The Powder River Basin, Wyoming is one of the most rapidly expanding areas of CBM development with projections of the establishment of up to 50,000 wells. CBM disturbances may make the native ecosystem more susceptible to invasion by non-native species, but there are few studies that have been conducted on the environmental impacts of this type of resource extraction. To evaluate the potential effects of CBM development on native plant species distribution and patterns of non-native plant invasion, 36 modified Forest Inventory and Analysis plots (each comprised of four 168-m2 subplots) were established in the Powder River Basin, Wyoming. There were 73 168-m2 subplots on control sites; 42 subplots on secondary disturbances; 14 on major surface disturbances; eight on well pads; and seven on sites downslope of CBM wells water discharge points. Native plant species cover ranged from 39.5 ± 2.7% (mean ± 1 SE) in the secondary disturbance subplots to 17.7 ± 7.5% in the pad subplots. Non-native plant species cover ranged from 31.0 ± 8.4% in the discharge areas to 14.7 ± 8.9% in the pad subplots. The control subplots had significantly less non-native species richness than the combined disturbance types. The combined disturbance subplots had significantly greater soil salinity than the control sites. These results suggest that CBM development and associated disturbances may facilitate the establishment of non-native plants. Future research and management decisions should consider the accumulative landscape-scale effects of CBM development on preserving native plant diversity.  相似文献   
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