Coral diseases have increased in frequency over the past few decades and have important influences on the structure and composition of coral reef communities. However, there is limited information on the etiologies of many coral diseases, and pathways through which coral diseases are acquired and transmitted are still in question. Furthermore, it is difficult to assess the impacts of disease on coral populations because outbreaks often co-occur with temperature-induced bleaching and anthropogenic stressors. We developed spatially explicit population models of coral disease and bleaching dynamics to quantify the impact of six common diseases on Florida Keys corals, including aspergillosis, dark spots, white band, white plague, white patch, and Caribbean yellow band. Models were fit to an 8-year data set of coral abundance, disease prevalence, and bleaching prevalence. Model selection was used to assess alternative pathways for disease transmission, and the influence of environmental stressors, including sea temperature and human population density, on disease prevalence and coral mortality. Classic disease transmission from contagious to susceptible colonies provided the best-fit model only for aspergillosis. For other diseases, external disease forcing, such as through a vector or directly from pathogens in the environment, provided the best fit to observed data. Estimates of disease reproductive ratio values (R0) were less than one for each disease, indicating coral colonies were below densities required for diseases to become established through contagious spread alone. Incidences of white band and white patch disease were associated with greater susceptibility or slower recovery of bleached colonies, and no disease outbreaks were associated with periods of elevated sea temperatures alone. Projections of best-fit models indicated that, atleast during the period of this study, disease and bleaching did not have substantial impacts on populations and impaired rates of population growth appeared to be attributable to other stressors. By applying epidemiological models to field data, our study gives qualitative insights into the dynamics of coral diseases, relative stressor impacts, and directions for future research. 相似文献
Estuaries in the world are affected by different contamination sources related to urbanisation and port/industrial activities. Identifying the substances responsible for the environmental toxicity in estuaries is challenging due to the multitude of stressors, both natural and anthropogenic. The Toxicity Identification and Evaluation (TIE) is a suitable way of determining causes of toxicity of sediments, but it poses difficulties since its application is labour intensive and time consuming. The aim of this study is to evaluate the diagnosis provided by a TIE based on microscale embryotoxicity tests with interstitial water (IW) to identify toxicants in estuarine sediments affected by multiple stressors. TIE showed toxicity due to different combinations of metals, apolar organic compounds, ammonia and sulphides, depending on the contamination source closest to the sampling station. The microscale TIE was able to discern different toxicants on sites subject to different contamination sources. There is good agreement between the results indicated in the TIE and the chemical analyses in whole sediment, although there are some disagreements, either due to the sensitivity of the test used, or due to the particularities of the use of interstitial water to assess the sediment toxicity. The improvement of TIE methods focused on identifying toxicants in multiple-stressed estuarine areas are crucial to discern contamination sources and subsidise management strategies.
Environmental Science and Pollution Research - Increased industrialization and consumption of fossil fuels in the Metropolitan Region of São Paulo (MRSP), Brazil, have caused a growth of the... 相似文献
Deposition and storage of fine sediment on channel beds represents an important component of a catchment’s sediment budget
and can have important implications for sediment-associated P fluxes, due to storage and remobilisation, and for P concentrations
through water–sediment interactions. Spatial and temporal variations in P content and storage in fine bed sediment have been
studied in two UK lowland catchments, the Rivers Frome and Piddle in Dorset. Fine bed sediment was sampled in representative
reaches on a bi-monthly basis using a re-suspension cylinder, and the resulting samples were analysed for total P, a range
of P fractions and particle size. The results demonstrate significant spatial and temporal variability in PP concentrations
and storage, with maximum and minimum P concentrations and storage occurring in late summer and winter, respectively. Temporal
variations in concentrations reflect residence times of the sediment and ambient P concentrations, while variations in storage
are mainly due to hydrological regimes. Spatial variations reflect catchment characteristics, the location of inputs and local
variations in hydrological and channel bed conditions. 相似文献
This paper concerns the effects on biodiversity of depletion of the South African abalone Haliotis midae, which is a long-lived species with a large corrugated shell that provides a habitat for diverse benthic organisms. We compared community structure on H. midae shells with that on adjacent rock at three sites (Cape Point and Danger Point sites A and B) and at two different times of the year at one of these sites. Shells of H. midae consistently supported communities that were distinctly different from those on rock. In particular, three species of non-geniculate (encrusting) corallines, Titanoderma polycephalum, Mesophyllum engelhartii and Spongites discoideus, were all found either exclusively or predominantly on shells, whereas another non-geniculate coralline, Heydrichia woelkerlingii, occurred almost exclusively on adjacent rock. The primary rocky substratum, however, supported a higher number of species than abalone shells. Possible reasons for the differences between the two substrata include the relative age, microtopography and hardness of the substrata; the abundance of grazers on them; and the relative age of different zones of the abalone shell, which support communities at different stages of succession. Diversity on shells was lowest in zones that were either very young or very old, in keeping with the intermediate disturbance hypothesis. The distinctiveness of shell epibiota will increase β diversity despite having a lower α diversity than that of adjacent rock. Decimation of H. midae by overfishing therefore has implications for biodiversity conservation. 相似文献
Young asthmatic adult volunteers (N = 27) were exposed in an environmental chamber to sulfuric acid aerosol at concentrations near 0, 122, 242, and 410 μg/m3, in purified background air at 22° C and 50 percent relative humidity. The polydisperse aerosol had a mass median aerodynamic diameter near 0.6 μm. Exposures occurred in random order at one-week intervals. Each lasted 1 h, during which subjects exercised (mean ventilation 42 L/min) and rested during alternate 10-min periods. Specific airway resistance and forced expiratory function were measured pre-exposure, after the initial exercise, and at end-exposure. Bronchial reactivity was determined by challenge with cold air immediately post-exposure. Symptoms were monitored during exposure for one week afterward. Exercise-induced bronchospasm was observed under all conditions. Physiologic and symptom changes possibly attributable to sulfuric acid exposure were small and not statistically significant. Our largely negative results contrast with positive findings elsewhere at lower acid doses. Possible explanations include different clinical characteristics of subjects and different routes of breathing. 相似文献
We examined how the foraging ecology of the seed-harvesting ant Messor andrei depends upon the distribution of resources and the presence of conspecifics. Bait experiments showed that colonies can recruit
to high-density patches of seeds. However, at the seasonal scale, natural resource distribution did not affect the distribution
of foraging activity. We conducted the study in years of high rainfall and thus seed availability may not have been a limiting
factor. Colonies always preferred to forage in areas closer to their nest, which may reduce travel time between the nest and
foraging sites. On a day-to-day scale, encounters between neighboring colonies at a site increased the probability that colonies
would return to forage at that site; this was true both for natural and experimental encounters. In the summer, this resulted
in colonies foraging at the sites of intraspecific encounters on more days than in areas where no encounter had occurred.
Encounters between colonies included fighting, and there was little overlap between the foraging areas of neighboring colonies:
both results suggest that one function of encounters is to defend foraging space. The high probability of return to the site
of an encounter between colonies suggests that encounters may have a second function: to indicate the presence of resources.
Received: 28 June 1999 / Received in revised form: 12 October 1999 / Accepted: 16 October 1999 相似文献