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861.
Martin G. J. Löder Cédric Meunier Karen H. Wiltshire Maarten Boersma Nicole Aberle 《Marine Biology》2011,158(7):1551-1580
Mesocosm experiments coupled with dilution grazing experiments were carried out during the phytoplankton spring bloom 2009.
The interactions between phytoplankton, microzooplankton and copepods were investigated using natural plankton communities
obtained from Helgoland Roads (54°11.3′N; 7°54.0′E), North Sea. In the absence of mesozooplankton grazers, the microzooplankton
rapidly responded to different prey availabilities; this was most pronounced for ciliates such as strombidiids and strobilids.
The occurrence of ciliates was strongly dependent on specific prey and abrupt losses in their relative importance with the
disappearance of their prey were observed. Thecate and athecate dinoflagellates had a broader food spectrum and slower reaction
times compared with ciliates. In general, high microzooplankton potential grazing impacts with an average consumption of 120%
of the phytoplankton production (P
p
) were measured. Thus, the decline in phytoplankton biomass could be mainly attributed to an intense grazing by microzooplankton.
Copepods were less important phytoplankton grazers consuming on average only 47% of P
p
. Microzooplankton in turn contributed a substantial part to the copepods’ diets especially with decreasing quality of phytoplankton
food due to nutrient limitation over the course of the bloom. Copepod grazing rates exceeded microzooplankton growth, suggesting
their strong top-down control potential on microzooplankton in the field. Selective grazing by microzooplankton was an important
factor for stabilising a bloom of less-preferred diatom species in our mesocosms with specific species (Thalassiosira spp., Rhizosolenia spp. and Chaetoceros spp.) dominating the bloom. This study demonstrates the importance of microzooplankton grazers for structuring and controlling
phytoplankton spring blooms in temperate waters and the important role of copepods as top-down regulators of microzooplankton. 相似文献
862.
Lena von Harbou Corinna D. Dubischar Evgeny A. Pakhomov Brian P. V. Hunt Wilhelm Hagen Ulrich V. Bathmann 《Marine Biology》2011,158(9):2009-2026
Feeding dynamics of the Antarctic salps Ihlea racovitzai and Salpa thompsoni were studied in the Lazarev Sea in fall 2004, summer 2005–2006 and winter 2006. Pigment concentrations in the guts of both
species were positively correlated with ambient surface chlorophyll a (chl a). No evidence was found for salp clogging even at dense surface concentrations of up to 7 μg chl a L−1. However, gut pigment concentrations had a lower range than ambient pigment concentrations, suggesting that salps increased
retention times of ingested material in low-food environments. For medium-sized I. racovitzai and S. thompsoni, estimated individual daily rations reached 7–10 and >100% of body carbon in winter and summer, respectively. Daily respiratory
needs of I. racovitzai and S. thompsoni accounted for 28 and 22% of daily carbon assimilation based on pigment ingestion rates in winter, and for 2 and 1% in summer,
respectively. The grazing impact of the salp populations on the phytoplankton standing stock was negligible during all seasons
due to generally low salp densities. Fatty acid trophic biomarkers in the salps suggest high year-round contributions of flagellates
and modest contributions of diatoms to the salp’s diet. These markers showed low seasonal variability for I. racovitzai. The more pronounced seasonality of trophic markers in S. thompsoni were likely related to their generally deeper residence depth in winter linked to a seasonal alternation of sexual and asexual
generations. 相似文献
863.
Siegfried Franck Werner von BlohChristoph Müller Alberte BondeauB. Sakschewski 《Ecological modelling》2011,222(12):2019-2026
The maximum population, also called Earth's carrying capacity, is the maximum number of people that can live on the food and other resources available on planet Earth. Previous investigations estimated the maximum carrying capacity as large as about 1 trillion people under the assumption that photosynthesis is the limiting process. Here we use a present state-of-the-art dynamic global vegetation model with managed planetary land surface, Lund-Potsdam-Jena managed Land (LPJmL), to calculate the yields of the most productive crops on a global 0.5° × 0.5° grid. Using the 2005 crop distribution the model predicts total harvested calories that are sufficient for the nutrition of 11.4 billion people. We define scenarios where humankind uses the whole land area for agriculture, saves the rain forests and the boreal evergreen forests or cultivates only pasture to feed animals. Every scenario is run in an extreme version with no allowance for urban and recreational needs and in two soft versions with a certain area per person for non-agricultural use. We find that there are natural limits of the maximum carrying capacity which are independent of any increase in agricultural productivity, if non-agricultural land use is accounted for. Using all land planet Earth can sustain 282 billion people. The save-forests-scenario yields 150 billion people. The scenario that cultivates only pasture to feed animals yields 96 billion people. Nevertheless, we should always have in mind that all our calculated numbers for the carrying capacity refer to extreme scenarios where humankind may only vegetate on this planet. Our numbers are considerably higher than the general median estimate of upper bounds of human population found in the literature in the order of 10 billion. 相似文献
864.
Erik Olsen Alf Ring Kleiven Hein Rune Skjoldal Cecilie H. von Quillfeldt 《Journal of Coastal Conservation》2011,15(2):257-269
Place-based management is any management action having implications for a specified area. Place-based management is seen as
a key component to practical implementation of ecosystem approach to management, with marine spatial planning (MSP) being
the currently most promoted approach. In the present paper we address the challenges of place-based management at local, regional
and global (oceanic) spatial scales using case studies from the Northeast Atlantic with examples from Norway. Both ecological,
governance and management complexity increases with increasing geographic scale, with associated increases in uncertainty
and thus increasing need for managing under the precautionary approach. A process where (ecologically) valuable and vulnerable
areas are defined early on is essential to successful place-based management under the ecosystem approach. Integrating across
sectors and achieving necessary cooperation between involved institutions and stakeholders is also necessary. 相似文献
865.
Massimo?TavoniEmail author Bob?van der?Zwaan 《Environmental Modeling and Assessment》2011,16(5):431-440
In this paper, we analyze the relative importance and mutual behavior of two competing base-load electricity generation options
that each are capable of contributing significantly to the abatement of global CO2 emissions: nuclear energy and coal-based power production complemented with CO2 capture and storage (CCS). We also investigate how, in scenarios developed with an integrated assessment model that simulates
the economics of a climate-constrained world, the prospects for nuclear energy would change if exogenous limitations on the
spread of nuclear technology were relaxed. Using the climate change economics model World Induced Technical Change Hybrid,
we find that until 2050 the growth rates of nuclear electricity generation capacity would become comparable to historical
rates observed during the 1980s. Given that nuclear energy continues to face serious challenges and contention, we inspect
how extensive the improvements of coal-based power equipped with CCS technology would need to be if our economic optimization
model is to significantly scale down the construction of new nuclear power plants. 相似文献
866.
Birgit K. Boogaard Bettina B. Bock Simon J. Oosting Johannes S. C. Wiskerke Akke J. van der Zijpp 《Journal of Agricultural and Environmental Ethics》2011,24(3):259-282
Society’s relationship with modern animal farming is an ambivalent one: on the one hand there is rising criticism about modern
animal farming; on the other hand people appreciate certain aspects of it, such as increased food safety and low food prices.
This ambivalence reflects the two faces of modernity: the negative (exploitation of nature and loss of traditions) and the
positive (progress, convenience, and efficiency). This article draws on a national survey carried out in the Netherlands that
aimed at gaining a deeper understanding about the acceptance of modern dairy farming in Dutch society. People take two dimensions
into account when evaluating different aspects of modern dairy farming: (1) the way living beings are used for production
and (2) the way a dairy farm functions as a business. In both these dimensions people appeared to adopt cautious opinions:
most people preferred relatively traditional and natural farms and were concerned about the use of nature and treatment of
animals in modern production—although this did not imply an outright rejection of modern animal farming. The study also looked
for (and sought to explain) differences of opinion between social groups. Besides socio-demographic factors such as age and
gender, farming experience and value-orientation (such as socially minded and professional) appeared to be important variables.
The values and convictions within modern society can help to explain why some people are greatly concerned about animal welfare
while some show less concern. This diversity also helps to explain why general information campaigns are quite ineffective
in allaying concerns about modern animal farming. 相似文献
867.
Maria Molnarne Volkmar Schröder 《Journal of Loss Prevention in the Process Industries》2011,24(6):900-907
The classification of flammable gas mixtures is based on either testing or calculation methods proposed by the revised international standard ISO 10156. This standard is used for classification of physical hazards in Chapters 2.2 and 2.4 of the UN Globally Harmonized System of Classification and Labelling of Chemicals (GHS) and in the UN Recommendations on Transport of Dangerous Goods (TDG). The test methods of flammability and oxidizing potential in this standard were developed by BAM. Earlier versions of this standard are not based on triangular diagrams and on the reference combustible substance “ethane”. The old material characteristics, especially in case of oxidizing potential, are based mostly on practical experience without any quantifiable test results. First time it is possible to compare experimental results from the CHEMSAFE database with the newly developed calculation method. In this paper the basic principles of the calculation methods are presented and the methods are validated by examples. A comparison of experimental flammability data with classification results gained by the calculation methods of ISO 10156 is demonstrated. 相似文献
868.
Ruiping Liu Tingting Guo Min M Mingquan Yan Jing Qi Chengzhi Hu Gang Liu Huijuan Liu Jiuhui Qu Walter van der Meer 《环境科学学报(英文版)》2019,31(2):1-11
Coagulation is the best available method for removing intracellular organic matter (IOM), which is released from algae cells and is an important precursor to disinfection by-products in drinking water treatment. To gain insight into the best strategy to optimize IOM removal, the coagulation performance of two Al salts, i.e., aluminum chloride (AlCl3) and polyaluminum chloride (PACl, containing 81.2% Al13), was investigated to illuminate the effect of Al species distribution on IOM removal. PACl showed better removal efficiency than AlCl3 with regard to the removal of turbidity and dissolved organic carbon (DOC), owing to the higher charge neutralization effect and greater stability of pre-formed Al13 species. High pressure size exclusion chromatography analysis indicated that the superiority of PACl in DOC removal could be ascribed to the higher binding affinity between Al13 polymer and the low and medium molecular weight (MW) fractions of IOM. The results of differential log-transformed absorbance at 254 and 350?nm indicated more significant formation of complexes between AlCl3 and IOM, which benefits the removal of tryptophan-like proteins thereafter. Additionally, PACl showed more significant superiority compared to AlCl3 in the removal of < 5?kDa and hydrophilic fractions, which are widely viewed as the most difficult to remove by coagulation. This study provides insight into the interactions between Al species and IOM, and advances the optimization of coagulation for the removal of IOM in eutrophic water. 相似文献
869.
Rennio F. de Sena José L. Tambosi Silvia L. Floriani Elaine Virmond Horst Fr. Schröder Regina F.P.M. Moreira Humberto J. José 《Waste management (New York, N.Y.)》2009,29(9):2574-2581
The biosolids (BS) generated in the wastewater treatment process of a meat processing plant were monitored and the priority pollutant content was characterized. The trace metal and organic pollutant content – polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/PCDF) – were determined quantitatively and compared to guideline limits established by the US EPA and EU. PCBs were not detected in the solid samples, while trace metals, PAHs and PCDD/PCDF were detected in concentrations below the limits established by international standards. Toxic equivalent factors were evaluated for the biosolids, and the results proved that these wastes can be safely deposited on land or used in combustion/incineration plants. Since no previous data were found for meat processing waste, comparisons were made using municipal sewage sludge data reported in the literature. Since, this report monitored part of the priority pollutants established by the US EPA for meat and poultry processing wastewater and sludge, the results verified that low pollution loads are generated by the meat processing plant located in the southern part of Brazil. However, the BS generated in the treatment processes are in accordance with the limits established for waste disposal and even for soil fertilizer. 相似文献
870.