Quantifying parameter uncertainty in a coral reef model using Metropolis-Coupled Markov Chain Monte Carlo

Coral reefs are threatened ecosystems, so it is important to have predictive models of their dynamics. Most current models of coral reefs fall into two categories. The first is simple heuristic models which provide an abstract understanding of the possible behaviour of reefs in general, but do not describe real reefs. The second is complex simulations whose parameters are obtained from a range of sources such as literature estimates. We cannot estimate the parameters of these models from a single data set, and we have little idea of the uncertainty in their predictions.We have developed a compromise between these two extremes, which is complex enough to describe real reef data, but simple enough that we can estimate parameters for a specific reef from a time series. In previous work, we fitted this model to a long-term data set from Heron Island, Australia, using maximum likelihood methods. To evaluate predictions from this model, we need estimates of the uncertainty in our parameters. Here, we obtain such estimates using Bayesian Metropolis-Coupled Markov Chain Monte Carlo. We do this for versions of the model in which corals are aggregated into a single state variable (the three-state model), and in which corals are separated into four state variables (the six-state model), in order to determine the appropriate level of aggregation. We also estimate the posterior distribution of predicted trajectories in each case.In both cases, the fitted trajectories were close to the observed data, but we had doubts about the biological plausibility of some parameter estimates. We suggest that informative prior distributions incorporating expert knowledge may resolve this problem. In the six-state model, the posterior distribution of state frequencies after 40 years contained two divergent community types, one dominated by free space and soft corals, and one dominated by acroporid, pocilloporid, and massive corals. The three-state model predicts only a single community type. We conclude that the three-state model hides too much biological heterogeneity, but we need more data if we are to obtain reliable predictions from the six-state model. It is likely that there will be similarly large, but currently unevaluated, uncertainty in the predictions of other coral reef models, many of which are much more complex and harder to fit to real data.     

Mineralization of particulate organic matter derived from coral-reef organisms in reef sediments of the Gulf of Aqaba

In situ and laboratory incubation experiments in a fringing reef in the Gulf of Aqaba were performed to study degradation rates of particulate organic matter in reef sediments. Coral mucus, clam eggs, and zooxanthellae were used as model particulate organic compounds for these experiments. Aerobic and anaerobic mineralization rates were calculated by dissolved inorganic carbon (DIC) and O₂ fluxes from the sediments under different particulate organic matter additions. Fast enhancement (approximately twofold) of O₂ and DIC fluxes were found with the addition of coral mucus and clam eggs compared with control incubations without addition. Most of the degradation is believed to have occurred anaerobically rather than aerobically (DIC:O₂ ratios were 4.3–28.1). Higher degradation rates of coral mucus and clam eggs were estimated in carbonate sediment than in silicate sediment (1.2–1.6-fold), which was attributed to the different physical and chemical properties of both sediments. Our study shows the significance of the reef sediment as a suitable site for microbial degradation of particulate organic material excreted from different reef community organisms. This may increase the regeneration of nutrients in the reef environment necessary to sustain high biological productivity.     

润滑油废白土的应用探索

针对炼油企业废白土排放污染环境问题,在实验室中利用溶剂进行脱油处理,其脱油率及脱油废渣活性度都较高,但再生后的脱油废渣仍难以重复利用。而利用废白土作型砂添加剂的试验研究,其工业试验结果较为理想,且能彻底解决废渣的污染问题,实现其环保利用。     

微库仑法测定制浆造纸漂白废水的AOX研究

介绍Multi X2500总有机卤素分析仪对制浆造纸漂白废水中可吸附有机卤素(AOX)的测定;水样用硝酸调pH ＜2后,以双根活性炭玻璃填充柱法或振荡法进行吸附;将吸附有机物的活性炭在氧气流中燃烧热解、用微库仑法测定其卤化氢.试验结果显示,双根活性炭玻璃填充柱吸附法优于振荡吸附法.纯水中不同含氯量的加标实验平均回收率为86.0％～ 108％,实际水样加标实验回收率为86.3％～ 107％.     

水解酸化-生物接触氧化-漂白脱色工艺处理纺织综合废水

溢达纺织有限公司纺织综合废水水质为 :pH 10～ 14、CODCr10 0 0～ 15 0 0mg L、BOD530 0～ 4 5 0mg L、SS 30 0mg L、S2 - 3mg L ,水温 4 0～ 5 0℃、色度 4 0 0～ 6 0 0倍 ,采用水解酸化 生物接触氧化 漂白氧化脱色处理工艺 ,处理后出水达到排放目标。经过 2a多时间的运行实践 ,结果表明 ,处理的出水水质稳定。     

西沙永乐群岛岛礁海岸线变迁监测与分析

我国对南海诸岛及其附近海域拥有神圣不可侵犯的主权,珊瑚岛礁的开发、利用与保护,具有重要的战略价值。研究充分利用遥感影像宏观、快速、直观等优势,通过自动化识别与人机交互解译相结合的方法,对西沙永乐群岛岛礁岸线变迁情况进行变化监测。结果表明研究区内存在珊瑚礁岸线、基岩岸线和人工岸线三类岸线类型,以珊瑚礁岸线为主。通过对各岛礁在不同时期海岸线变迁的幅度与速度情况进行对比分析,发现珊瑚礁岸线变迁幅度最为剧烈,主要受自然因素影响,淤涨与侵蚀变迁交替作用,该类岸线处于一种不稳定的状态,其淤涨速率在不同时期不同岸段差异较大;其次为人工岸线,随着海岛的开发建设日益频繁,对土地的需求量不断增加,填海造地速度与幅度也大大增加;基岩岸线基本无变化,相对稳定。     

Coastal issues for oceanic islands: implications for human futures

Compared to continental areas, most islands have exceptionally long coastlines relative to their total land area. For this reason, islands are uncommonly vulnerable to problems associated with coasts. The future of the human inhabitants of many island states depends intrinsically on the sustainable management of their coasts, a challenge which grows more pressing as island populations increase and the associated demands on island coastlines change and grow. These issues are presented and discussed in this article. The mechanics of the sustainable management of island coasts is itself an important issue. At the national or local level, management is plagued by problems of insufficient and/or imprecise data and understanding that may lead to inappropriate solutions that even exacerbate the problems they are intended to solve. At an inter-governmental or international level, problems associated with the understanding of island environments need to be resolved before optimal management strategies can be developed. This article presents a brief explanation of the nature of coastal vulnerability on oceanic islands, followed by a discussion of several key problems associated with their sustainable development and the role of human and non-human factors in recent environmental change. It discusses the future of oceanic island coasts in the face of both internal and external threats to their sustainable management. It concludes with a blueprint for their survival.     

草浆漂白过程中二噁英类生成机理探讨

本文以氯苯、氯酚、二苯并二噁英（DBD）和二苯并呋喃（DBF）为PCDD/Fs前生体,模拟工业草浆漂白条件,探讨了次氯酸盐和氯气漂白苇浆过程中二噁英类的生成机制,研究表明,在苇浆中加入二噁英类前生体如DBD/F,其氯化产物与在木浆中有所区别,在实验条件下,二噁英类的生成量分别为:15μg PCDDs·mg~（-1）DBD。1.5μg PCDFs·mg~（-1）DBF。     

漂白废水白腐菌脱色的条件

碳源、氮源、Mn^2 浓度及pH值对F7菌漂白废水脱色有较大的影响,最佳培养基组成为：ρ（葡萄糖）10g/L,ρ（NH4Cl）0．13g/L,ρ（Mn^2 )20mg/L,随葡萄糖和NH4Cl添国量的增加,菌体生物量增加,但高浓度的NH4Cl对F7菌脱色有抑制作用,F7菌适宜生长pH值为4－5,适宜脱色pHwfhgo 3-6,最适脱色pH值为5．0另外,经脱色处理的漂白废水的毒性明显下降。     

Marine litter in coral reef areas along the Jordan Gulf of Aqaba, Red Sea

Composition and abundance of submerged marine litter at six selected sites within a coral reef area along the Jordanian coast of the Gulf of Aqaba have been estimated. The litter was collected in clean up voluntary campaigns that took place in the period between 25 August 2003 and 29 February 2004. A total of 10,506 items weighing 1159 kg were collected during the survey. Mean litter density in the individual sampling sites varied between 1 and 6 items/m(2) with an overall mean density of 2.8 items/m(2). The mean weight of the collected items per sampling site varied between 0.06 and 1.06 kg/m(2) with an overall mean of 0.31 kg/m(2). Plastic accounted for 42% of the collected items, fishing gear was the second most abundant (31%) while metal was the third most abundant item (17%). By comparison, cardboard constituted 1%, and rubber and other items accounted for less than 1% of the total items collected during the campaigns. Approximately 61% of the plastics consisted of bags followed by bottles (24%), plastic containers and sheets accounted for 13 and 2%, respectively. Statistical analysis indicates no significant differences between the sites in terms of litter count and weight. Potential sources are pointed out and recommendations and actions to address the problem are suggested.