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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Environmental management 18 (1994), S. 663-676 
    ISSN: 1432-1009
    Keywords: Aquaculture ; Shrimp farming ; Colombia ; Sustainability ; Resource use ; Life support system ; Carrying capacity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Shrimp farming in mangrove areas has grown dramatically in Asia and Latin America over the past decade. As a result, demand for resources required for farming, such as feed, seed, and clean water, has increased substantially. This study focuses on semiintensive shrimp culture as practiced on the Caribbean coast of Colombia. We estimated the spatial ecosystem support that is required to produce the food inputs, nursery areas, and clean water to the shrimp farms, as well as to process wastes. We also made an estimate of the natural and human-made resources necessary to run a typical semiintensive shrimp farm. The results show that a semiintensive shrimp farm needs a spatial ecosystem support—the ecological footprint—that is 35–190 times larger than the surface area of the farm. A typical such shrimp farm appropriates about 295 J of ecological work for each joule of edible shrimp protein produced. The corresponding figure for industrial energy is 40:1. More than 80% of the ecological primary production required to feed the shrimps is derived from external ecosystems. In 1990 an area of 874–2300 km2 of mangrove was required to supply shrimp postlarvae to the farms in Colombia, corresponding to a total area equivalent to about 20–50% of the country’s total mangrove area. The results were compared with similar estimates for other food production systems, particularly aquacultural ones. The comparison indicates that shrimp farming ranks as one of the most resource-intensive food production systems, characterizing it as an ecologically unsustainable throughput system. Based on the results, we discuss local, national, and regional appropriation of ecological support by the semiintensive shrimp farms. Suggestions are made for how shrimp farming could be transformed into a food production system that is less environmentally degrading and less dependent on external support areas.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Global production of farmed fish and shellfish has more than doubled in the past 15 years. Many people believe that such growth relieves pressure on ocean fisheries, but the opposite is true for some types of aquaculture. Farming carnivorous species requires large inputs of wild fish for feed. ...
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 19 (1988), S. 0 
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. 1. The biomass distribution of submerged vascular vegetation and benthic fauna were investigated by diving in Lake Kariba. The vegetation was well correlated with transparency of the water. Maximum biomass (1400 g dryweight m−2) and a depth penetration of 6 m were found in areas little influenced by river inflow, while these were only 110 g m−2 and 2 m, respectively, in the basin receiving water from the Zambezi river.2. The lake is mesotrophic-oligotrophic. The total biomass for the lake was 101,000 tons dryweight of rooted vegetation composed of Lagarosiphon ilicifolius Oberm. (52%), Najas pectinata (Parl) Magnus (33%), Vatlisneria aethiopica Frenzl (11%), Ceratophyllum demersum L. (3%) and Potamogeton octandrus L. (0.5%). Average plant biomass for the potentially colonizable depth zone of 0-12 m and for the total lake amounted to 79.9 g m−2 and 18.8 g m−2, respectively.3. The distribution of the benthic fauna generally followed that of the vegetation. The total animal biomass of 118,840 tons dryweight. including shells, consisted of mussels (95.8%), snails (4.1%) and insect larvae (0.1%). Four species of mussels were found: Caelatura mossambicensis (von Martens) (81% of mussel biomass), Corbicula africana (Krauss) (9%). Mutela dubia (Gmelin) (5%) and Aspatharia wahlbergii (Krauss) (5%). Among the snails Melnoides tuberculuta (Müller), Cleopatra spp. and Bellamya capillata (Frauenfeld) dominated.4. The average animal biomass was high compared to most other lakes perhaps due to lack of predators. For the colonizable 0-12 m depth interval and the total lake it was 96.2 g m−2 including shells (15.0 g m−2 shell-free dryweight) and 22.6 g m−2 including shells (3.4 g m−2 shell-free dryweight). respectively. Biomass of plants and animals was even higher prior to the recent lowering of the water level by 7 m, which was estimated to have stranded 84,000 tons of mussels on the shore.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 39 (1998), S. 0 
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We studied trophic interactions in experimental rockpools with three different food web structures: phytoplankton and small-bodied zooplankton; phytoplankton, small-bodied zooplankton and Daphnia; and phytoplankton, small-bodied zooplankton, Daphnia and Notonecta. Nutrients, primary productivity, chlorophyll a and zooplankton species composition and biomass were measured over eight weeks.2. Daphnia had a negative impact on other zooplankton and reduced the phytoplankton biomass and primary productivity. In the absence of Daphnia, small-bodied zooplankton species were abundant, in particular cyclopoid copepods. Concentrations of dissolved nutrients were lower and the standing crop of primary producers was higher when Daphnia was absent.3. The presence of the invertebrate predator Notonecta produced a top-down effect which was similar to that reported for planktivorous fish, i.e. a selective reduction of daphnids followed by an increase of small-bodied zooplankton species and phytoplankton biomass.4. The study showed that consumer regulation of Daphnia by Notonecta and of algae by Daphnia are important, but also demonstrated that trophic level biomasses were controlled by a combination of predation and resource limitation.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-5117
    Keywords: biofilter ; environmental sustainability ; Gracilaria ; salmonids ; seaweeds ; tank cultivation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Oncorhynchus kisutch, O. mykiss and Gracilaria chilensis cultivation in intensive tank systems is feasible. The environmental benefits associated with the development of integrated tank cultivation were established by analyzing previously published and unpublished data on fish production and food conversion efficiency, particle discharges in fish effluents, as well as biomass production, nutrient uptake efficiency data of Gracilaria, with special emphasis on ammonium. The results indicate that fish production can reach 30 kg m−3 during a production cycle, and food conversion can be maintained stably at 1.4 g food g fish−1 production during the entire cultivation period. The solid particle discharges can be as high as 2.1 g (dry) kg fish−1 day−1 during the spring and summer, when salmon cultivation reaches its highest densities. The nutrient that increases most in fish effluents is ammonium, reaching concentrations as high as 500 µg 1−1, also in spring and summer. Gracilaria production can reach production rates as high as 48.9 kg m−2 year−1 and is able to remove 50% of the dissolved ammonium in winter, increasing to 90–95% in spring. These results are integrated into an income-analysis model, adding the extra income for Gracilaria harvesting and internalizing the environmental benefits for a 100-ton salmon production unit, which indicates that an additional total revenue of over US$ 60 000, representing around 10% of the total income, is possible.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-5117
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The productivity and ecological role of benthos in man-made Lake Kariba was assessed through the use of P/B-ratios and by measuring the metabolism (respiration, N and P excretion) of the most abundant mussel species (Aspatharia wahlbergi, Corbicula africana and Caelatura mossambicensis) in laboratory experiments. For A. wahlbergi also filtration rate was estimated. The annual production of benthos for the populated 0–12 m interval was estimated at 11.0 g m −2 yr−1 (shellfree dry weight) of which mussels contributed for 8.81 g (80%), snails 2.16 g (20%) and insects 0.03 g (0.3%) respectively. The most important mussel species in the lake were Caelatura mossambicensis (4.97 g m−2 yr−1) and Corbicula africana (3.33 g). The dominant snail species was Melanoides tuberculata (1.63 g). For the total lake, also including deeper unpopulated bottoms, the annual production of benthos was 2.70 g m−2 yr−1 (shell-free dry weight). Respiration and excretion varied with temperature displaying a bell-shaped relationship. Metabolic rates in Aspatharia wahlbergi increased about 5× between 16.5 °C and the maximum at 34.0 °C and then decreased again at 39.0 °C, when the mussels showed signs of severe stress. Metabolism in Corbicula africana had a lower optimum with fairly constant activity between 18.6 and 29.2 °C, rapidly decreasing above this temperature. The average respiration, nutrient excretion and water filtration rates for mussels in Lake Kariba at 25.2 °C were estimated to about 0.6 mg O2 85 µg NH4−N, 1.5 µg PO4−P and 0.51 water filtered h−1 g−1 shellfree dry weight. This gives that a volume corresponding to about the total epilimnion of the lake is filtered by the mussels annually. Further, mussels can be estimated to remineralise % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0Jf9crFfpeea0xh9v8qiW7rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaGymaiaac+% cacaaI0aaaaa!3A2B!\[1/4\] of the total load of phosphate, and 8 times the total load of nitrogen every year. The population needs 3.5 × 104 tons of organic carbon for its maintainance, which indicates that about 5% of the annual phytoplankton production is channeled through mussels. We conclude that the mussels, rather than being an important food source for fish, seem to play a large role in the nutrient dynamics of Lake Kariba.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Water, air & soil pollution 83 (1995), S. 237-252 
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Metal mining is carried out in the drainage basin of Lake Kariba, Zimbabwe. In an attempt to assess the distribution of heavy metals in the lake ecosystem, the concentrations of chromium (Cr), cadmium (Cd), copper (Cu), lead (Pb), manganese (Mn), nickel (Ni), zinc (Zn), and selenium (Se) were analysed in the following ecosystem components at different locations in the lake; water, sediment, aquatic macrophytes, mussels, and carnivorous and herbivorous fish. Concentrations were generally in the same range as in other temperate and tropical aquatic ecosystems, except for Pb and Cd, which were higher in marcrophytes and fish from the lake. Apart from Cd, there were no signs of biomagnification and the highest levels of metals were found in the macrophytes and sediments. While metal contamination in fish is probably a combination of uptake from the food and an equilibrium with the surrounding water, the levels in macrophytes appear to be determined mainly by uptake from the sediment through the roots.
    Type of Medium: Electronic Resource
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  • 8
    Publication Date: 2020-03-12
    Description: We consider two aspects of the human enterprise that profoundly affect the global environment: population and consumption. We show that fertility and consumption behavior harbor a class of externalities that have not been much noted in the literature. Both are driven in part by attitudes and preferences that are not egoistic but socially embedded; that is, each household’s decisions are influenced by the decisions made by others. In a famous paper, Garrett Hardin [G. Hardin,Science162, 1243–1248 (1968)] drew attention to overpopulation and concluded that the solution lay in people “abandoning the freedom to breed.” That human attitudes and practices are socially embedded suggests that it is possible for people to reduce their fertility rates and consumption demands without experiencing a loss in wellbeing. We focus on fertility in sub-Saharan Africa and consumption in the rich world and argue that bottom-up social mechanisms rather than top-down government interventions are better placed to bring about those ecologically desirable changes.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 9
  • 10
    Publication Date: 1996-09-01
    Print ISSN: 0018-8158
    Electronic ISSN: 1573-5117
    Topics: Biology
    Published by Springer
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