Coral bleaching and habitat effects on colonisation of reef fish assemblages: An experimental study

Degradation and mortality of corals is increasing worldwide and is expected to have significant effects on coral reef fish; hence studies on these effects are essential. In the present study, a field experiment was set up within Mafia Island Marine Park in Tanzania (East Africa) to examine the effects of bleaching and habitat structure on colonisation of coral reef fish assemblages. Live and bleached staghorn coral Acropora formosa was transplanted onto plots in a site dominated by sand and rubble, and the experimental design comprised of three treatments: live coral, bleached coral and eroded coral rubble. There was an immediate increase (within 24 h) in fish abundance and diversity in the two treatments with standing corals. Overall, live and bleached coral plots showed similar effects, but differed from the eroded coral plots which had a much lower abundance and diversity of fish. In general, fish species diversity changed with time over the study period while fish abundance did not. Multivariate analyses showed that while there were differences in fish assemblage structure between standing corals and the eroded coral treatment, there was neither a difference between live and bleached coral treatments nor any temporal effects on fish assemblage structure. Our findings suggest that physical structure and complexity of habitat have stronger effects on colonisation of reef fish assemblages than changes in coral health (such as bleaching) which do not affect coral structure. This may have important implications for appropriate coral reef management.     

在细胞水平上对高温珊瑚白化的初步研究

全球变暖背景下的异常高温能够导致珊瑚及其虫黄藻组成的共生体系崩溃,虫黄藻大量损失,出现珊瑚白化,并可能进一步导致珊瑚礁生态系统退化.文章通过对6种造礁石珊瑚的急性高温胁迫实验,分析不同种属的石珊瑚虫黄藻共生体系对高温的耐受性差异,为全球变暖背景下珊瑚群落演替趋势提供理论依据.结果显示:1)在急性高温胁迫下,石珊瑚耐受的差异性与其形态有关,枝状珊瑚耐受性最低,在高温胁迫下最先白化、死亡,而叶片状和块状珊瑚对高温的耐受性较强,这与野外珊瑚礁白化的现场观测结果一致.2)在高温胁迫下,不同种属珊瑚共生虫黄藻损失的方式不同:珊瑚持续排出虫黄藻,如鹿角杯形珊瑚 Pocillopora damicornis;珊瑚先排出一定的共生藻,之后珊瑚组织携带大量虫黄藻与珊瑚骨骼分离,如风信子鹿角珊瑚 Acropora hyacinthus 和松枝鹿角珊瑚 Acropora brueggemanni;先排出部分虫黄藻后,虫黄藻以有丝分裂增殖的方式迅速补充其数量,如十字牡丹珊瑚 Pavona decussata;虫黄藻细胞直接坏死而损失虫黄藻,如澄黄滨珊瑚 Porites lutea.研究强调,预测珊瑚对全球变化的响应问题时,应当同时考虑珊瑚宿主和共生藻的作用.     

福建东山海域柳珊瑚种类空间分布与多样性

调查并分析了福建东山珊瑚省级自然保护区内柳珊瑚的种类多样性及其空间分布,结果表明：（1）共发现柳珊瑚15种,分别属于6科11属,其中新记录属和新记录种各2个,分别为Gua-iagorgia anas和星柳珊瑚（Astrogorgia dumbea）.结合2005年7月和本次对东山柳珊瑚的采样调查,共发现柳珊瑚19种,全部为不含共生藻的种类.（2）东山柳珊瑚优势种为小月柳珊瑚（Menella sp.）、刺柳珊瑚（Echinogorgia sp.）和小尖柳珊瑚（Muricella sp.）.（3）东山柳珊瑚主要分布在实验区,如塔屿东面、铁钉屿南面和龙屿南面,而在缓冲区和核心区也有柳珊瑚分布较为丰富的站位.在靠近主要污染源的站位,未见到或者很少见到柳珊瑚的分布.东山珊瑚保护区内柳珊瑚的空间分布与食物的丰富程度、海流以及陆源输入等都有较大的关系.     

基于放射性核素的沉积物源识别技术探索与优化以红树林−海草床−珊瑚礁系统为例

物质来源是沉积学研究的关键问题。沉积地球化学是沉积学的重要研究手段,放射性核素在沉积地球化学中的应用探索仍较为匮乏。本研究利用高纯锗γ谱仪同时测量红树林、海草床、珊瑚礁三大典型生态系统的沉积物中天然放射性核素（²³⁸U、²²⁶Ra、²²⁸Ra、⁴⁰K）,分析3种生态系统的沉积物中放射性核素分布特征,探索基于放射性核素的一维视角下活度特征、二维视角下核素对与活度比值、三维视角下三角图解的指纹表征技术,识别沉积物中不同物质的来源,并尝试推广至中国不同海域。本研究强调三维指纹表征技术—基于核素活度的²³⁸U-²³²Th(²²⁸Ra)-⁴⁰K/10三角图解可以综合展示3种放射性核素的活度大小、组成比例、空间分布等信息,指出²³⁸U-²³²Th(²²⁸Ra)-⁴⁰K/10三角图解可能是沉积物中物源识别的一种优化方法,可为沉积地球化学研究中的现有代用指标工具库提供有益补充。     

Evaluation of spatial correlation between nutrient exchange rates and benthic biota in a reef-flat ecosystem by GIS-assisted flow-tracking

A Geographic Information System (GIS)-aided flow-tracking technique was adopted to investigate nutrient exchange rates between specific benthic communities and overlying seawater in a fringing reef of Ishigaki Island, subtropical Northwestern Pacific. Net exchange rates of NO₃ ⁻, NO₂ ⁻, NH₄ ⁺, PO₄ ³⁻, Total-N and Total-P were estimated from concentration changes along the drogue trajectories, each of which was tracked by the Global Positioning System and plotted on a benthic map to determine the types of benthic habitat over which the drogue had passed. The observed nutrient exchange rates were compared between 5 typical benthic zones (branched-coral (B) and Heliopora communities (H), seaweed-reefrock zone (W), bare sand area (S), and seagrass meadow (G)). The dependence of nutrient exchange rates on nutrient concentrations, physical conditions and benthic characteristics was analyzed by multiple regression analysis with the aid of GIS. The spatial correlation between nutrient exchange rates and benthic characteristics was confirmed, especially for NO₃ ⁻ and PO₄ ³⁻, which were usually absorbed in hydrographically upstream zones B and W and regenerated in downstream zones H and G. NO₃ ⁻ uptake in zones B and W was concentration-dependent, and the uptake rate coefficient was estimated to be 0.58 and 0.67 m h⁻¹, respectively. Both nutrient uptake in zone W and regeneration in zone H were enhanced in summer. The net regeneration ratio of NO₃ ⁻/PO₄ ³⁻ in zone H in summer ranged 5.2 to 34 (mean, 17.4), which was somewhat higher than previously measured NO₃ ⁻/PO₄ ³⁻ for sediment pore waters around this zone (1.1–8.5). Nutrient exchanges in zone S were relatively small, indicating semi-closed nutrient cycling at the sediment-water interface of this zone. NH₄ ⁺ efflux from sediments was suggested in zone G. The data suggest that the spatial pattern of nutrient dynamics over the reef flat community was constrained by zonation of benthic biota, and that abiotic factors such as nutrient concentrations and flow rates, influenced nutrient exchange rates only in absorption-dominated communities such as zones B and W.     

Non-hydrostatic modelling of regular wave transformation and current circulation in an idealized reef-lagoon-channel system

The wave-induced setup and circulation in a two dimensional horizontal (2DH) reef-lagoon-channel system is investigated by a non-hydrostatic model. The simulated results agree well with observations from the laboratory experiments, revealing that the model is valid in simulating wave transformation and currents over reefs. The effects of incident wave height, period, and reef flat water depth on the mean sea level and wave-driven currents are examined. Results show that the distributions of mean sea level and current velocities on the reef flat adjacent to the channel vary significantly from those in the area close to the side walls. From the wave averaged current field, an obvious alongshore flux flowing from the reef flat to the channel is captured. The flux from the reef flat composes the second source of the offshore rip current, while the first source is from the lagoon. A detailed momentum balance analysis shows that the alongshore current is mainly induced by the pressure gradient between the reef flat and the channel. In the lagoon, the momentum balances are between the pressure and radiation stress gradient, which drives flow towards the channel. Along the channel, the offshore current is mainly driven by the pressure gradient.     

南海北部珊瑚Ba/Ca比值的季节变化及其环境意义

利用等离子体普技术分析了取自海南岛南部沿岸的现代演珊瑚高分辨率的Ｂａ／Ｃａ。结果表明,该珊瑚的Ｂａ／Ｃａ比值具有明显的双峰态的季节变化,其中春季和秋季Ｂａ／Ｃａ比值较镐,而冬、夏两季则较低。海南岛南部及邻近地区季节降雨的变化所控制的原Ｂａ输入是这些珊瑚Ｂａ／Ｃａ比值变化的重要控制因素,而该区夏季相对较镐的表层海水生产力可能也对其有重要影响。     

华南热带海岸生物地貌过程*

海岸生物地貌过程研究海岸带生物过程和动力-沉积-地貌过程之间的双向相互作用,是海岸生态系统响应和反馈全球变化的重要机制,被列为全球变化核心项目海岸带陆海相互作用研究的重点内容。20世纪90年代以来的调查研究揭示了华南红树林和珊瑚礁热带生物海岸生物地貌过程的主要特点。造礁石珊瑚的高生长率和珊瑚礁高堆积速率是珊瑚礁生物地貌过程的物质基础;红树林生态系统的高生产力、高归还率和捕沙促淤功能是红树林生物地貌过程的物质基础。热带生物海岸地貌结构显示分带性和生物地貌类型和动力地貌类型的叠加和共存,潮汐水位严格控制群落分布格局并形成重要的生物地貌界限。热带生物海岸生物地貌过程有利于消除或减缓海平面上升的浸淹效应。热带生物海岸不断加剧的人类活动干扰和生态破坏导致生物地貌功能削弱和海岸资源环境恶化。     

南海东北部两种软珊瑚

金黄编笠软珊瑚Morchellana boleliformis(Ridley)和黎明编笠软珊瑚Morchellana auroro(Ridley)隶属于棘软珊瑚科Nephtheidae编笠软珊瑚属Morchellana,于1979—1983年采自南海东北部水域。     

珊瑚岛礁淡水透镜体的生物修复研究

运用半模理论,研制了高1.2 m、直径1.5 m的半圆柱体实验平台,对受到有机污染的珊瑚岛礁淡水透镜体进行原位曝气生物修复研究.研究了溶解氧(DiSSOlvecl 0xygen,DO)在地下水中的.分布规律及脱色和化学耗氧量(Chemical oxygen demanol,COD)的去除效果.结果表明:(1)径向上,在主流区半径R为0.2～0.5 m的范围内,D0的质量浓度随R的增大而增大.R0.5 m,DO的质量浓度随R的增大而降低.垂向上,DO的质量浓度随高度的增大而迅速增大.(2)地下水色度和COD均随曝气时间的增加而降低,色度为40度、COD为96 mg/L的原水,曝气18 d后,色度均不超过15度,曝气30 d后,色度不超过10度,COD为21～36 mg/L.以色度不超过15度作为修复的标准,修复区半径R达0.7 m,修复区高度H为0.9 m.(3)修复1 m3的上述原水和1.3 m3土壤所需的空气量约为211 m3.