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Termination of harmful algal blooms (HABs) and coexistence of phytoplankton–zooplankton populations are of great importance to human health, ecosystem, environment, tourism and fisheries. In this paper, we propose a three component model consisting of non-toxic phytoplankton (NTP), toxin producing phytoplankton (TPP) and zooplankton (Z). The growth of zooplankton species is assume to reduce due to toxic chemicals released by TPP population. We have extended the model proposed by Chattopadhyay et al. [Chattopadhyay, J., Sarkar, R.R., Pal, S., 2004. Mathematical modelling of harmful algal blooms supported by experimental findings. Ecol. Comp. 1, 225–235] by including competition terms between TPP and NTP. We observe the effect of competition factors both in the presence and absence of the environmental fluctuation. From our field as well as model analysis we observe that competition helps in the coexistence of the species, but if the effect of competition is very high on the TPP population, it results in planktonic bloom. It is shown that the coexistence equilibrium loses its stability when the competition coefficient crosses a critical value and resulting Hopf-bifurcation around the positive equilibrium depicting oscillations phenomena of the populations. 相似文献
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通过对Bloom分类学,即对教育活动三个领域划分方法的研究,从心理学角度详细分析了教育活动中认知、情感学习、运动三个领域子层面的内涵,指出该方法对教育工作者科学有效地开展教育活动具有重要的现实指导意义。 相似文献
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Faouzi Herzi Natacha Jean Huiyu Zhao Stéphane Mounier Hassine Hadj Mabrouk Asma Sakka Hlaili 《Chemosphere》2013
In this study, metal contamination experiments were conducted to investigate the effects of copper and cadmium on the growth of the marine toxic dinoflagellate Alexandrium catenella and on the production of dissolved organic matter (Dissolved Organic Carbon: DOC; Fluorescent Dissolved Organic Matter: FDOM). This species was exposed to increasing concentrations of Cu2+ (9.93 × 10−10–1.00 × 10−7 M) or Cd2+ (1.30 × 10−8–4.38 × 10−7 M), to simulate polluted environments. The drastic effects were observed at pCu2+ = 7.96 (Cu2+: 1.08 × 10−8 M) and pCd2+ = 7.28 (Cd2+: 5.19 × 10−8 M), where cyst formation occurred. Lower levels of Cu2+ (pCu2+ > 9.00) and Cd2+ (pCd2+ > 7.28) had no effect on growth. However, when levels of Cu2+ and Cd2+ were beyond 10−7 M, the growth was totally inhibited. The DOC released per cell (DOC/Cell) was different depending on the exposure time and the metal contamination, with higher DOC/Cell values in response to Cu2+ and Cd2+, comparatively to the control. Samples were also analyzed by 3D-fluorescence spectroscopy, using the Parallel Factor Analysis (PARAFAC) algorithm to characterize the FDOM. The PARAFAC analytical treatment revealed four components (C1, C2, C3 and C4) that could be associated with two contributions: one, related to the biological activity; the other, linked to the decomposition of organic matter. The C1 component combined a tryptophan peak and a characteristic humic substances response, and the C2 component was considered as a tryptophan protein fluorophore. The C3 and C4 components were associated to marine organic matter production. 相似文献
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Critical review of actually available chemical compounds for prevention and management of cyanobacterial blooms 总被引:3,自引:0,他引:3
Cyanobacteria proliferation is among the most threatening consequences of freshwater pollution. Health risks from human and other-organism exposure to cyanobacteria have led to an effort to find practical methods for cyanobacterial water-bloom reduction. Hence, methods and techniques have been developed in order to reduce the amount of phosphorus or to decrease the abundance of nuisance phytoplankton species directly in the water bodies (in-lake measures). Although these “acute” methods do not solve the problem of catchment area eutrophication, they are cheaper, easier to manage, and for some areas they are the only way to protect human and environmental health against massive cyanobacterial proliferation. This review summarizes the extent of knowledge and published data about the management using metals (Al, Fe, Cu, Ag, Ca), photosensitizers (hydrogen peroxide, phthalocyanines, TiO2), herbicides and chemicals derived from natural compounds as fast and efficient removal agents of cyanobacteria. This review concludes that some compounds, when non-persistent and ecotoxicologically acceptable may help to manage cyanobacterial blooms in an efficient way compared to previous methods (e.g. copper sulfate). 相似文献
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