629 resultados para Bleaching.
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Includes bibliography.
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No more published. --cf. Wilson cat., no. 39, 1933.
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Mode of access: Internet.
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"Presenting a review of the year's advances in the bleaching, dyeing, printing, and finishing of textiles."
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Imperfect; wanting the volume entitled, "Paper, by Prof. Archer, Printing, by Joseph Hatton, etc."
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The indefinite determiner yi 'one'+ classifier' is the most approximate to an indefinite article, like the English a, in Chinese. It serves all the functions characteristic of representative stages of grammaticalization from a numeral to a generalized indefinite determiner as elaborated in the literature. It is established in this paper that the Chinese indefinite determiner has developed a special use with definite expressions, serving as a backgrounding device marking entities as of low thematic importance and unlikely to receive subsequent mentions in ensuing discourse. 'yi+ classifier' in the special use with definite expressions displays striking similarities in terms of semantic bleaching and phonological reduction with the same determiner at the advanced stage of grammaticalization characterized by uses with generics, nonspecifics and nonreferentials. An explanation is offered in terms of an implicational relation between nonreferentiality and low thematic importance which characterize the two uses of the indefinite determiner. While providing another piece of evidence in support of the claim that semantically nonreferentials and entities of low thematic importance tend to be encoded in terms of same linguistic devices in language, findings in this paper have shown how an indefinite determiner can undergo a higher degree of grammaticalization than has been reported in the literature-it expands its scope to mark not only indefinite but also definite expressions as semantically nonreferential and/or thematically unimportant. (C) 2003 Elsevier B.V. All rights reserved.
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Recent reports of contamination of the Great Barrier Reef Marine Park by herbicides used in antifouling paints and in agriculture have caused concern over the possible effects on corals in nearshore areas. Pulse-Amplitude Modulated (PAM) chlorophyll fluorescence techniques were used to examine changes in the maximum effective quantum yield (ΔF/Fm′) of symbiotic dinoflagellates within the host tissues (in hospite) of the coral Seriatopora hystrix exposed to a number of Photosystem II (PSII) inhibiting herbicides in short-term toxicity tests. The concentration of herbicide required to reduce ΔF/Fm′ by 50% (median effective concentration [EC50]) differed by over 2 orders of magnitude: Irgarol 1051 (0.7 μg l-1) > ametryn (1.7 μg l-1) > diuron (2.3 μg l-1) > hexazinone (8.8 μg l -1) > atrazine (45 μg l-1) > simazine (150 μg l-1) > tebuthiuron (175 μg l-1) > ionynil (> 1 mg l-1). Similar absolute and relative toxicities were observed with colonies of the coral Acropora formosa (Irgarol 1051 EC50: 1.3 μg l-1, diuron EC50: 2.8 μg l-1), Time-course experiments indicated that ΔF/Fm′ was rapidly reduced (i.e. within minutes) in S. hystrix exposed to Irgarol 1051 and diuron. On return to fresh running seawater, ΔF/Fm′ recovered quickly in diuron-exposed corals (i.e. in minutes to hours), but slowly in corals exposed to Irgarol 1051 (i.e. hours to days). Time-course experiments indicated that the effects of diuron (3 μg l-1) on S. hystrix were inversely related to temperature over the range 20 to 30 °C, although initially the effects were less at the lower temperatures. Repeated exposure to pulses of Irgarol 1051 (daily 2 h exposure to 30 μg l -1 over 4 d) resulted in a 30% decrease in the density of symbiotic dinoflagellates in the tissues of S. hystrix.
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There is concern of the effects of Produced Formation Water (PFW, an effluent of the offshore oil and gas industry) on temperate/tropical marine organisms of the North West Shelf (NWS) of Australia. Little is known of the effects of PFW on tropical marine organisms, especially keystone species. Exposing the coral Plesiastrea versipora to a range (3-50% v/v) of PFW from Harriet A oil platform resulted in a reduction in photochemical efficiency of the symbiotic dinoflagellate algae in hospite ( in the coral tissues), assessed as a decrease in the ratio of variable fluorescence (F-v) to maximal fluorescence (F-m) measured using chlorophyll fluorescence techniques. Significant differences were noted at PFW concentrations >12.5% ( v/v). In corals where F-v/F-m was significantly lowered by PFW exposure, significant discolouration of the tissues occurred in a subsequent 4-day observation period. The discolouration ( coral bleaching) was caused by a loss of the symbiotic dinoflagellates from the tissues, a known sublethal stress response of corals. PFW caused a significant decrease in F-v/F-m in symbiotic dinoflagellates freshly isolated from the coral Heliofungia actiniformis at 6.25% PFW, slightly lower than the studies in hospite. Corals exposed to lower PFW concentrations (range 0.1%-10% PFW v/v) for longer periods (8 days) showed no decrease in F-v/F-m, discolouration, loss of symbiotic dinoflagellates or changes in gross photosynthesis or respiration ( measured using O-2 exchange techniques). The study demonstrates minor toxicity of PFW from Harriet A oil platform to corals and their symbiotic algae.
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The diversity, frequency, and scale of human impacts on coral reefs are increasing to the extent that reefs are threatened globally. Projected increases in carbon dioxide and temperature over the next 50 years exceed the conditions under which coral reefs have flourished over the past half-million years. However, reefs will change rather than disappear entirely, with some species already showing far greater tolerance to climate change and coral bleaching than others. International integration of management strategies that support reef resilience need to be vigorously implemented, and complemented by strong policy decisions to reduce the rate of global warming.
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Coral reefs are the most diverse marine ecosystem and embrace possibly millions of plant, animal and protist species. Mutualistic symbioses are a fundamental feature of coral reefs that have been used to explain their structure, biodiversity and existence. Complex inter-relationships between hosts, habitats and symbionts belie closely coupled nutrient and community dynamics that create the circumstances for something from nothing (or the oasis in a nutrient desert). The flip side of these dynamics is a close dependency between species, which results in a series of non-linear relationships as conditions change. These responses are being highlighted as anthropogenic influences increase across the world's tropical and subtropical coastlines. Caribbean as well as Indo-Pacific coral populations are now in a serious decline in many parts of the world. This has resulted in a significant reorganization of how coral reef ecosystems function. Among the spectra of changes brought about by humans is rapid climate change. Mass coral bleaching - the loss of the dinoflagellate symbionts from reef-building corals - and mortality has affected the world's coral reefs with increasing frequency and intensity since the late 1970s. Mass bleaching events, which often cover thousands of square kilometres of coral reefs, are triggered by small increases (+1-3degreesC) in water temperature. These increases in sea temperature are often seen during warm phase weather conditions (e.g. ENSO) and are increasing in size and magnitude. The loss of living coral cover (e.g. 16% globally in 1998, an exceptionally warm year) is resulting in an as yet unspecified reduction in the abundance of a myriad of other species. Projections from general circulation models (GCM) used to project changes in global temperature indicate that conditions even under the mildest greenhouse gas emission scenarios may exceed the thermal tolerances of most reef-building coral communities. Research must now explore key issues such as the extent to which the thermal tolerances of corals and their symbionts are dynamic if bleaching and disease are linked; how the loss of high densities of reef-building coral will affect other dependent species; and, how the loss of coral populations will affect the millions of people globally who depend on coral reefs for their daily survival.
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During the austral summer of 2001/2002, a coral epizootic occurred almost simultaneously with a bleaching event on the fringing reefs of Magnetic Island (Great Barrier Reef region), Australia. This resulted in a 3- to 4-fold increase in the mean percentage of partial mortality rate in a population of the hard coral Montipora aequituberculata. The putative disease state, ‘atramentous necrosis’, was observed on both bleached and normally-pigmented M. aequituberculata, and presented blackened lesions that spread within days across the colony surface and throughout the population. Diseased portions of the corals were only visible for 3 to 4 wk, with diseased tissues becoming covered in sediment and algae, which rapidly obscured evidence of the outbreak. Diseased colonies were again observed in the summer of 2002/2003 after being absent over the 2002 winter. Analysis of when diseased and bleached corals were first observed, and when and where the mortality occurred on individual colonies, indicated virtually all the mortality over the summer could be attributed to the disease and not to the bleaching. Fluorescence in situ hybridisation (FISH) techniques and cloning, and analysis of the 16S rRNA genes from diseased coral tissue, identified a mixed microbial assemblage in the diseased tissues particularly within the Alphaproteobacteria, Firmicutes and Bacteroidetes. While it is not possible in this study to distinguish between a disease-causing microbial community versus secondary invaders, the bacterial 16S rDNA sequences identified within the blackened lesions demonstrated high similarity to sequences from black band disease and white plague infected corals, suggesting either common aetiological agents or development of a bacterial community that is specific to degrading coral tissues. Temperature-induced coral disease outbreaks, with the potential for elevated levels of mortality, may represent an added problem for corals during the warmer summer months and an added dimension to predicted increases in water temperature from climate change.
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The effects of the herbicide diuron on the early life history stages of broadcast spawning and brooding corals were examined in laboratory experiments. Fertilisation of Acropora millepora and Montipora aequituberculata oocytes were not inhibited at diuron concentrations of up to 1000 mu gl(-1). Metamorphosis of symbiont-free A. millepora larvae was only significantly inhibited at 300 mu gl(-1) diuron. Pocillopora damicornis larvae, which contain symbiotic dinoflagellates, were able to undergo metamorphosis after 24h exposure to diuron at 1000 mu gl(-1). Two-week old P. damicornis recruits on the other hand were as susceptible to diuron as adult colonies, with expulsion of symbiotic dinoflagellates (bleaching) evident at 10 mu gl(-1) diuron after 96 h exposure. Reversible metamorphosis was observed at high diuron concentrations, with fully bleached polyps escaping from their skeletons. Pulse amplitude modulation (PAM) chlorophyll fluorescence techniques demonstrated a reduction in photosynthetic efficiency (Delta F/F'(m)) in illuminated P. dami- cornis recruits after a 2h exposure to 1 mu gl(-1) diuron. The dark-adapted quantum yields (F-v/F-m also declined, indicating chronic photoinhibition and damage to photosystem H. Crown Copyright (c) 2004 Published by Elsevier Ltd. All rights reserved.
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Photosynthetic endolithic algae and cyanobacteria live within the skeletons of many scleractinians. Under normal conditions, less than 5% of the photosynthetically active radiation (PAR) reaches the green endolithic algae because of the absorbance of light by the endosymbiotic dinoflagellates and the carbonate skeleton. When corals bleach (loose dinoflagellate symbionts), however, the tissue of the corals become highly transparent and photosynthetic microendoliths may be exposed to high levels of both thermal and solar stress. This study explores the consequence of these combined stresses on the phototrophic endoliths inhabiting the skeleton of Montipora monasteriata, growing at Heron Island, on the southern Great Barrier Reef. Endoliths that were exposed to sun after tissue removal were by far more susceptible to thermal photoinhibition and photo-damage than endoliths under coral tissue that contained high concentrations of brown dinoflagellate symbionts. While temperature or light alone did not result in decreased photosynthetic efficiency of the endoliths, combined thermal and solar stress caused a major decrease and delayed recovery. Endoliths protected under intact tissue recovered rapidly and photoacclimated soon after exposure to elevated sea temperatures. Endoliths under naturally occurring bleached tissue of M. monasteriata colonies (bleaching event in March 2004 at Heron Island) acclimated to increased irradiance as the brown symbionts disappeared. We suggest that two major factors determine the outcome of thermal bleaching to the endolith community. The first is the microhabitat and light levels under which a coral grows, and the second is the susceptibility of the coral-dinoflagellates symbiosis to thermal stress. More resistant corals may take longer to bleach allowing endoliths time to acclimate to a new light environment. This in turn may have implications for coral survival.
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Adaptation to localised thermal regimes is facilitated by restricted gene flow, ultimately leading to genetic divergence among populations and differences in their physiological tolerances. Allozyme analysis of six polymorphic loci was used to assess genetic differentiation between nine populations of the reef-building coral Acropora millepora over a latitudinal temperature gradient on the inshore regions of the Great Barrier Reef (GBR). Small but significant genetic differentiation indicative of moderate levels of gene flow (pairwise F-ST 0.023 to 0.077) was found between southern populations of A. millepora in cooler regions of the GBR and the warmer, central or northern GBR populations. Patterns of genetic differentiation at these putatively neutral allozyme loci broadly matched experimental variation in thermal tolerance and were consistent with local thermal regimes (warmest monthly-averages) for the A. millepora populations examined. It is therefore hypothesized that natural selection has influenced the thermal tolerance of the A. millepora populations examined and greater genetic divergence is likely to be revealed by examination of genetic markers under the direct effects of natural selection.
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Heating the scleractinian coral, Montipora monasteriata (Forskal 1775) to 32 degrees C under < 650 mu mol quanta m(-2) s(-1) led to bleaching in the form of a reduction in Peridinin, xanthophyll pool, chlorophyll c(2) and chlorophyll a, but areal dinoflagellates densities did not decline. Associated with this bleaching, chlorophyll (Chl) allomerization and dinoflagellate xanthophyll cycling increased. Chl allomerization is believed to result from the interaction of Chl with singlet oxygen (O-1(2)) or other reactive oxygen species. Thermally induced increases in Chl allomerization are consistent with other studies that have demonstrated that thermal stress generates reactive oxygen species in symbiotic dinoflagellates. Xanthophyll cycling requires the establishment of a pH gradient across the thylakoid membrane. Our results indicate that, during the early stages of thermal stress, thylakoid membranes are intact. Different morphs of M. monasteriata responded differently to the heat stress applied: heavily pigmented coral hosts taken from a high-light environment showed significant reductions in green fluorescent protein (GFP)-like homologues, whereas nonhost pigmented high-light morphs experienced a significant reduction in water-soluble protein content. Paradoxically, the more shade acclimated cave morph were, based on Chl fluorescence data, less thermally stressed than either of the high-light morphs. These results Support the importance of coral pigments for the regulation of the light environment within the host tissue.