北部湾涠洲岛珊瑚礁底栖贝类的群落特征

珊瑚礁是全球生物多样性最高的海洋生态系统之一,底栖贝类是该生态系统的重要组成类群。为了解北部湾涠洲岛珊瑚礁底栖贝类的群落现状及特征,于2015年秋季(10月)与2018年春季(5月)采用水肺潜水截线样条定量调查法对涠洲岛珊瑚礁区6个断面的底栖贝类进行了调查,并分析了物种组成、丰度、生物多样性指数等群落特征。综合两次调查结果显示涠洲岛珊瑚礁区共有底栖贝类128种,分别属于多板纲1科1属3种,腹足纲25科46属68种,双壳纲22科31属57种。优势种为斑顶拟舌骨牡蛎、粗衣蛤、刺荔枝螺、马蹄螺、杂色牙螺、青蚶、旗江珧、甲虫螺、蕾丝蟹守螺、珠母爱尔螺。2018年春季定量断面采集到的样品为2纲14科43种,各断面的丰度、生物量、多样性指数、物种丰度指数和均匀度指数均值分别为3.39个/m2、86.94 g/m2、3.31、3.50、0.37。通过对两年的调查数据比较,发现2015-2018年涠洲岛珊瑚礁区的贝类生物群落呈现良好演替发育趋势。南海珊瑚礁区贝类群落结构可能受到了人为干扰强度和纬度的双重影响。本研究全面掌握了涠洲岛珊瑚礁底栖贝类的种类、分布区及群落的结构与变化,可为该地区海洋生物资源开...     

西沙赵述岛海域珊瑚礁生态修复效果的初步评估

珊瑚恢复是一个协助退化、受损的珊瑚礁生态系统恢复的过程.近10 a来,西沙珊瑚礁生态系统不断退化,至2009年珊瑚覆盖率已下降至不足10%.针对西沙群岛珊瑚礁生态系统的退化状况,2011年12月于西沙赵述岛海域投放人工礁基并开展珊瑚移植实验,比较了人工修复区和自然恢复区1a后的修复效果.结果显示,投放礁基且进行珊瑚移植的区域,移植珊瑚的存活率不到10%;投放礁基但未进行珊瑚移植的区域,珊瑚补充量高达6~7 ind/m2;自然恢复区其珊瑚覆盖率提高了19.4%.依据珊瑚礁生态修复效果评估方法,人工修复且进行移植珊瑚的区域的生物修复权重值为27.5,人工修复但未移植珊瑚区及自然恢复区的生物修复权重值为39.3,珊瑚修复生物指标为亚健康.我们的结果表明,在健康、有良好珊瑚幼虫补充的珊瑚礁生态系统中,珊瑚礁群落可以自行恢复,其恢复只是一个时间的问题;而在缺少珊瑚幼虫附着基底的区域,通过人为增加一些附着基底,可加速其恢复进程.     

Change in coral reef benthic communities in the Lembeh Strait and Likupang, North Sulawesi, Indonesia

Anthropogenic impacts and natural disturbances have been intense recently in the global scale, affecting the composition of coral reef benthic communities from coral to algal dominated reefs. However, this condition does not always occur considering corals are able to recover when the stressors falter. This study aims to investigate the change in coral reef benthic communities and the relationship among benthic categories. The study was carried out in 2014 and 2016 at five sites, three sites in the Lembeh Strait and two sites in Likupang, North Sulawesi Province. Underwater Photo Transect(UPT) was used at depth of around 4–6 m in slope areas. The result indicated that the benthic communities were slightly changing: the percent covers of hard corals, sponges, soft corals, macroalgae and substrate categories were not significantly different between the years but category of others, particularly seasonally growing hydroid, increased significantly, occupying the available substrates and overtopping other benthos surrounding. The study also found that there was a significant relationship between the change in benthic gradient and the number of hard coral colonies: when the composition becomes less complex, the number of colony declines. In contrast, the hard coral diversity remained unchanged, suggesting the coral reefs apparently have an ecological resilience(sustainable species diversity) against the change although ecological complexity declines. In addition, the hard coral cover was significantly correlated with soft coral and sponge covers, which did not change significantly among the years. In general, the coral reefs in North Sulawesi might experience a temporary blip due to the increasing percent cover of others, and be predicted to recover as there was no indication of soft corals and sponges to increase significantly. However, it is necessary to investigate the dynamic of benthic communities in different depth gradients to gain a comprehensive understanding as the communities respond differently to the light intensity.     

珊瑚礁环境质量变化的价值评估——以涠洲岛为例

以涠洲岛为例,使用非市场价值评估手段对涠洲岛珊瑚礁环境质量进行了非使用价值评估,分析了珊瑚礁环境质量变化所产生的价值损益。2012年在涠洲岛通过模拟3种珊瑚礁环境质量变化,对上岛游客进行调访,游客从影响珊瑚礁环境质量的珊瑚礁覆盖度、珊瑚礁种类以及海水能见度3方面进行考虑,选择最终旅游目的地,共调查300位游客,收集有效数据900份。应用随机效应理论和混合对数模型进行分析和评估,结果显示,当涠洲岛珊瑚礁环境质量提升时,将会人均获益399元/年;当涠洲岛珊瑚礁环境质量略有下降时,将会损失人均561元/年;而当珊瑚礁环境质量下降较大时,人均损失将达到918元/年。同时,本研究的成果可以推广到其它海岛以及陆地进行环境质量变化评估,并且可以评估未来气候变化条件下对珊瑚礁生态系统的价值损失。     

南沙珊瑚礁对大气CO2含量上升的响应

本文利用南沙海域的碳酸盐化学以及相关调查资料，分析了表层CaCO3饱和度的分布特征，通过碳酸盐的热力学计算模式，定量评估了未来大气CO2增加对表层CaCO3饱和度的潜在影响，利用CaCO3饱和度与珊瑚钙化速率的经验关系式，进一步预测了珊瑚礁对大气CO2上升可能产生的生物地球化学响应．初步结果显示，工业革命前至2100年，南沙海域的CaCO3饱和度将下降43％左右，从而将引起珊瑚礁的平均钙化速率减少33％．如果未来大气CO2浓度继续保持目前的上升趋势，南沙海域珊瑚礁可能会停止生长，甚至某些造礁生物面，临灭绝的危险．     

Spatio-temporal variability of benthic macroalgae in a coral reef system highly influenced by fluvial discharge: Veracruz,Gulf of Mexico

The Veracruz Reef System, in the southern Gulf of Mexico, is a suitable area for the study of the temporal and spatial variability of macroalgae abundance, at reef settings influenced by the fluvial discharge of the Jamapa River, and by human activities in the city and port of Veracruz. With this purpose, the bottom cover of each morpho-functional group of benthic macroalgae (frondoses, turf, and crustose corallines), and hermatypic corals, was determined at ten selected coral reefs, on a seasonal basis (rainy and dry seasons), for the 2009–2015 period. The average cover of benthic macroalgae was high (53.1%), with turf as the dominant morpho-functional group (31.9%), as in several reef ecosystems in the tropical Atlantic, followed by crustose corallines (15.2%), and frondoses (6.1%). Although turf macroalgae is dominant, due to their high temporal and spatial variability, the Veracruz Reef System could not be considered to be in a stable state, but just in an intermediate unstable equilibrium state, which is highly influenced by a high sediment load. As expected, nearshore reefs presented higher macroalgae covers, and unexpectedly, the outer-shelf reefs presented the highest cover of frondoses. Despite fluvial discharge influence, no differences in cover were found between the rainy and dry seasons. There was a negative and significantly correlation between the cover of frondoses and turf, which suggests that the driver/s of the abundance of these macroalgae, act in opposite ways for each group. Three clusters of reefs, defined by community structure and conservation degree, were determined: nearshore or degraded, offshore or moderately conserved, and conserved; and the entire Veracruz Reef System is considered to be in a moderately state of conservation.     

Spatial distribution of crustaceans associated with shallow soft‐bottom habitats in a coral reef lagoon

The ecology and diversity of the shallow soft‐bottom areas adjacent to coral reefs are still poorly known. To date, the few studies conducted in these habitats dealing with macroinvertebrate fauna have focused on their abundance spatial patterns at high taxonomic levels. Thus, some aspects important to evaluate the importance and vulnerability of these habitats, such as species diversity or the degree of habitat specialization, have often been overlooked. In this study we compared the crustacean assemblages present in four different habitats at Magoodhoo Island coral reef lagoon (Maldives): coral rubble, sandy areas and two different seagrass species (Thalassia hemprichii and Cymodocea sp.). Forty‐two different crustacean species belonging to 30 families and four orders were found. ‘Site’ was a significant factor in all of the statistical analyses, indicating that tropical soft‐bottom habitats can be highly heterogeneous, even at a spatial scale between tens and hundreds of meters. Although traditionally it has been considered that seagrass beds host greater species diversity and abundance of organisms than adjacent unvegetated habitats, no differences in the univariate measures of fauna (abundance of organisms, number of species and Shannon diversity) were observed among habitats. However, sandy areas, coral rubble and seagrass beds exhibited different species composition of crustacean communities. The percentage of taxa considered as potential habitat specialists was 27% and the number of species exclusively occurring in one habitat was especially high in seagrass beds. Thus, degradation of this vegetated habitat would result in a great loss of biodiversity in tropical shallow soft‐bottom habitats.     

涠洲岛珊瑚礁生态恢复可行性评估及其恢复策略

广西涠洲岛地处世界珊瑚礁分布的北缘,其造礁石珊瑚具有较高的生态价值和科学研究价值,然而近30年来涠洲岛的造礁石珊瑚资源呈逐年下降趋势,正面临生物多样性衰退和生态服务功能下降的威胁。本研究针对涠洲岛珊瑚礁生态衰退区域,参照珊瑚礁生态恢复潜力评估决策流程进行恢复可行性评估和恢复策略探讨。结果显示,该区域有造礁石珊瑚5科10属21种;表征海水水质质量的6项指标均在I类水质标准范围,且常年处于贫营养化;大型海藻覆盖率不足1.00%,90.00%以上的珊瑚礁鱼类为杂食性,且该鱼类种群结构有利于调控大型海藻的暴发性生长,与大型藻类和浮游动植物的多样性相适应,适宜珊瑚生长。但该区域造礁石珊瑚平均覆盖率仅有5.60%,底质类型57.27%为礁石,34.30%的底质为非稳定的碎石和砂,珊瑚幼体补充量平均为3.17 ind/m²,珊瑚幼体更新缓慢。以上结果表明,涠洲岛珊瑚礁具有一定的自然恢复潜力,但珊瑚覆盖率低、幼体补充量少以及部分底质结构不稳定是限制涠洲岛珊瑚礁自然恢复的主要因素,需要加强人工干预。在减少人类活动干扰的前提下,适时进行园艺式培育珊瑚苗种、批量珊瑚原位种植和构建人工珊...     

Reef fishes recruited at midwater coral nurseries consume biofouling and reduce cleaning time in Seychelles,Indian Ocean

In coral reef restoration, coral gardening involves rearing coral fragments in underwater nurseries prior to transplantation. These nurseries become fish-aggregating devices and attract biofouling. We hypothesised that: (1) the presence of corals at a nursery is critical to recruit fish assemblages and (2) the recruited fish assemblages control biofouling, reducing person-hours invested in nursery cleaning. Three midwater coral nurseries were deployed at 8?m depth for 27 months within the marine protected area of Cousin Island Special Reserve, Seychelles, Indian Ocean. Each nursery consisted of a 6?m×6?m PVC pipe frame, layered with a recycled 5.5-cm-mesh tuna net. Human cleaning effort was calculated based on daily dive logs. Nursery-associated fish assemblages and behaviour were video-recorded prior to harvesting corals after a 20-month growth period and seven months post-coral harvesting. The density (ind. m–2) of blue-yellow damselfish Pomacentrus caeruleus was 12–16 times higher when corals were present than when corals were absent at the nurseries. Fish assemblages recruited into the nurseries included three trophic levels, from herbivores to omnivores, in six families: Ephippidae, Pomacentridae, Labridae (Scarinae), Gobiidae, Siganidae and Monacanthidae. Higher abundance of large fish (total number of individuals) resulted in 2.75 times less person-hours spent in nursery cleaning. These results have important implications for cost-effective coral reef restoration.     

20 年来涠洲岛珊瑚礁物种多样性演变特征研究

综合2007年10～11月、2008年4～5月布置的6条主剖面20条分断面的调查结果,涠洲岛珊瑚礁共出现石珊瑚10科22属46种,9个未定种,该调查区以角蜂巢珊瑚属(Favites)、滨珊瑚属(Porites)、蔷薇珊瑚属(Montipora)为优势类群,各主剖面的优势类群分布各有差异,以西南部的W2主剖面、东北部的W5主剖面的珊瑚礁属种最多,均为8科13属;涠洲岛珊瑚礁属级多样性指数H′值和均匀度指数E值均呈现东北部W5西南部W2东南部W6西南部W1西北部W3北部W4的规律,H′值差异明显,E值变化不大;其珊瑚礁群落近20 a来受到全球气候事件及区域人为活动的影响,整体呈现出衰退迹象,处于缓慢恢复状态。衰退表现在:从20世纪60年代至21世纪初期的珊瑚礁优势种群的组合变化,由较多的优势属种组合演化到相对少的优势属种组合。一直占据优势的鹿角珊瑚种群出现退化,从顶级优势类群降级更替;珊瑚礁属种的多形态组合向相对简单形态组合的演变;历年来珊瑚礁伴生生物的资料(主要是鱼群数量、海参等)显示,涠洲岛珊瑚礁群落生物多样性呈现衰退态势;从2001年至今连续的珊瑚礁健康调查(Reef Check)资料显示,该区石珊瑚礁曾大面积死亡尚未完全恢复。从涠洲岛20 a珊瑚礁多样性演变过程研究发现,影响因素主要包括全球性极端气候、区域性气候变化及不合理的破坏性人类活动影响等因素。     

Khai岛和Pathiu岛珊瑚礁沉积物细菌多样性及细菌粗提物延缓秀丽隐杆线虫衰老活性研究*

在Khai岛和Pathiu岛珊瑚礁生长海域采集2份珊瑚礁沉积物样品, 将样品预处理后采用6种分离培养基进行分离培养, 获得活性海洋细菌菌株, 通过PCR扩增和16s rRNA基因序列测定, 分析物种多样性, 并构建系统发育树。以模式生物秀丽隐杆线虫为模型考察菌株发酵提取物延缓衰老的作用。实验结果表明, 从4种样品中分离鉴定出22株细菌, 分别属于11目13科14属。16S rRNA基因序列相似性低于98.65%的细菌有2株, 疑似为潜在新种。GXIMD014 (Vibrio galatheae)和GXIMD112 (Kocuria kristinae)的500μg·mL^-1细菌粗提物具有延缓线虫衰老的活性, 能不同程度的延长线虫寿命, 提高线虫产卵量、运动能力、热激损伤能力、抗氧化损伤能力、体内酶活性以及改善虫体表皮形态。Khai岛和Pathiu岛珊瑚礁沉积物细菌具有较高的物种多样性, 蕴藏着丰富的微生物资源, 且部分细菌菌株具有延缓衰老的生物活性。     

南海西南部珊瑚礁区活动断裂分析

利用SEABAT8111多波束系统在南海西南部珊瑚礁区海域进行地形地貌探测,同时还进行了单道和多道地球物理调查。探测表明该区珊瑚礁礁体的活动断裂主要有NE、NW、SN向3组。NE向断裂主要分布在岛礁区内,是晚燕山期南海第一次海底扩张时形成的断裂系,强烈活动于晚白垩世—始新世,晚第三纪以来继承性活动,以张剪性断裂为主,现今活动性中等至弱。NW向断裂主要分布在曾母盆地,以张剪性断裂为主,切割至基底,强烈活动于渐新世至上新世,构成了曾母盆地的主要张裂期,第四纪仍有活动,均为弱活动断裂。SN向断裂主要有南海西部的滨海断裂带,它是南海SN向扩张时期的转换断层,具张剪性,为中活动断裂,是南海西南部珊瑚礁区活动性较强的断裂,该断裂带历史上曾有火山活动和地震活动的记录。     

Physical habitat and social conditions across a coral reef shape spatial patterns of intraspecific behavioral variation in a demersal fish

As coral reef ecosystems decline in health worldwide, reef‐associated fishes are being impacted by changes to their coral reef habitats. While previous studies have shown coral reef structure to affect the demography of reef fishes, changes in reef conditions may also impact the behavior of reef fishes as they cope with altered habitats. In this study, we examined spatial patterns of intraspecific behavioral variation in the bicolor damselfish (Stegastes partitus) across the fringing reefs of Curaçao (Caribbean Sea), and explored how this behavioral variation associated with physical and social conditions on the reef. Principal components analysis (PCA) condensed physical parameters of the reef into principal component 1 (PC1), comprising depth, coral cover (%), rugosity, and average hole size (cm²), and principal component 2 (PC2), which represented the number of holes. PC1, but not PC2, increased spatially across the reef as the habitat transitioned from coral rubble in the shallows to live coral on the reef slope. This transition in reef structure was paralleled by changes in social conditions including decreases in bicolor damselfish density in habitats with higher PC1 values. The behavior of bicolor damselfish also varied spatially with greater aggression and more frequent shelter use in habitats with lower PC1 values. Path analysis revealed robust associations between this behavioral variation and physical habitat conditions of the reef, indicating that physical – rather than social – habitat variation is the primary determinant of these spatial patterns of intraspecific behavioral variation. Taken as a whole, this coupling between physical reef structure and behavior suggests that reef fish may show altered behaviors on coral reefs degraded by anthropogenic impacts.     

Binogeochemical process of major elements in sinking particulate of Nansha coral reef lagoons,South

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Gradients in coral reef communities exposed to muddy river discharge in Pohnpei,Micronesia

This study analyzed how coral communities change along a gradient of increasing exposure to a mud-discharging river in the Enipein Catchment, Pohnpei, Micronesia. Using video transects, we quantified benthic communities at five sites along a gradient moving away from the river mouth towards the barrier reef. The most river-impacted site was characterized by a high accumulation of mud, low coral cover and low coral diversity. Although coral cover leveled off at ∼400 m from the river mouth to values found at the outer-most sites, coral diversity continued to increase with increasing distance, suggesting that the most distant site was still impacted by the river discharges. Fungiidae, Pavona, Acropora, Pachyseris and Porites rus all significantly increased in cover with distance from the river, while Turbinaria decreased. The combined presence and abundance of these six species groups, together with coral species richness, may help to indicate the effects of terrestrial runoff in similar runoff-exposed settings around Micronesia, whereas coral cover is not a sensitive indicator for river impact. Coral reefs are important resources for the people of Pohnpei. To prevent further degradation of this important resource, an integrated watershed approach is needed to control terrestrial activities.     

Effects of geomorphological zones, reefs and seasons on coral reef fish communities of Réunion Island, Mascarene Archipelago, SW Indian Ocean

The present work analyses the spatial and temporal fluctuations of fish communities on Réunion coral reef flats on three different reefs, each comprising three geomorphological zones, over eight seasons within a 6-year period. These three reefs are subjected to different environmental conditions and displayed various percentages of live coral cover. Our objectives were not only to describe the spatio-temporal patterns, but also to organize the factors involved in variation hierarchically, and to quantify the degree of community structuring that could be monitored over various spatial and temporal scales. We also focus on fish guilds to link the spatio-temporal patterns not only to species but also to the roles fish are playing (mainly involving trophic activity). We found that spatial attributes strongly determined fish distribution, with intra-reefal zones (back-reef, inner reef flat and outer reef flat) playing a much more important role than the different reefs. This suggests that the percentage of live coral cover of a given reef was less significant than its morpho-structural organization to explain fish distribution. Seasons had only a weak role in fish distribution, although fish communities were significantly more homogeneous in winter than in summer, possibly due to the arrival of numerous juveniles belonging to various species during summer settlement events. We also identified a marked temporal persistence of the spatial patterns found over the course of the study. This is discussed in relation to the current trend of increased surface seawater temperatures involved in the possible future increase in number/intensity of ENSO events. We consider the average squared Euclidian distance as a candidate for monitoring tools to quantify future changes in fish community structuring.     

Dietary separation between co-occurring copepods in a food-limited tropical coral reef of the Sanya Bay

Food differentiation among coexistent species in the field is important strategy for copepods to acquire materials and maintain population stabilization.In situ diet analysis of co-occurring six copepod species in coral waters of the Sanya Bay was conducted using a PCR protocol based on 18 S ribosomal gene.Various prey organisms were uncovered,including dinoflagellate,diatom,green algae and plant,protozoa and metazoan.All these spatially coexisting six species showed different dietary diversity,with the food niche breadth(B)ranging from 1.00(Temora turbinate in morning)to 10.68(Calanopia elliptica in night).While food overlap between all these copepods were low,with the average value of the diet niche overlap index being approximately 0.09.Even temporally co-existing species sampled from the same time point fed on different groups of prey items with the food overlap index of 0.04 to 0.07 in midday and night but 0 in morning.As the most important dominant copepod in the Sanya Bay,Subeucalanus subcrassus seems to be capable to regulate its feeding,by exhibiting a rhythm of herbivorous feeding in midday and carnivorous feeding in morning and night,to better coordinate with other competitors for utilization of food resources.For most copepods,none of the prey items belonged to the dominant phytoplankton in the ambient water,indicating that copepod can better their survival by widening the choice of potential food resources in food limited environment.The dietary separation observed here might be important strategy for copepod to maintain population stabilization and thriving in the Sanya coastal waters.     

Impact of hydrographic parameters and seasonal variation in sediment fluxes on coral status at Chumbe and Bawe reefs,Zanzibar, Tanzania

Coral reefs which are an important resource to coastal communities and nation at large are adversely affected by rate of sediment flux to the reefs. However, there is little information on seasonal trend in sediment flux and its impact at the reefs off Zanzibar. Two years’ monthly data on sedimentation at Chumbe and Bawe reefs were used to assess seasonal variability in sediment flux and its implication on the coral status. Sediment flux to the Bawe reefs for the duration of the study ranged from 0.2 to 41.5 mg cm⁻² d⁻¹, while it ranged from 0.8 to 65.8 mg cm⁻² d⁻¹ at the Chumbe reefs. Sediment fluxes at Bawe reefs were highest between November and March, while they were highest between April and September at Chumbe reefs. Generally, sediment fluxes at Bawe reefs were low compared to those at Chumbe. The total sediment input to the reefs ranged from 4615 to 123,403 kg d⁻¹ for Bawe reefs and 2750 to 79,636 kg d⁻¹ for Chumbe reefs. High sediment fluxes at Bawe reefs between November and March; and the Chumbe reefs between April and September can be attributed to water currents and wind pattern in the east African region which are under the influence of the monsoons. The observed trend suggests that the period for coral transplant as a management option for the two sites should be different. Coral transplant can be undertaken in such a way that stress of the corals due to sedimentation can be felt after they have overcome stress from transplant process and temperature. The results from this study contribute to the much needed information for coral transplant, restoration, and management.     

Short‐term temporal variation in gelatinous zooplankton populations over 48 hours in a coral reef at Redang Island,Malaysia

Gelatinous zooplankton abundance and species composition were investigated at 3‐h intervals for a 48‐h period at a fringing reef in Malaysia. A total of 20 gelatinous zooplankton species were observed; the community was dominated by the calycophoran siphonophore Diphyes chamissonis (79.9%), followed by the trachymedusdae Aglaura hemistoma (5.6%) and Liriope tetraphylla (4.8%). The gelatinous zooplankton were not collected in the water column during most of the daytime hours (1200, 1500 and 1800 h) but were common during the night. However, an abrupt peak in abundance was found at 0900 h on the second day. The times of appearance at night were different depending on the species, and the number of species was also different depending on the hour of sampling. Sampling at 3‐h intervals over a 48‐h period revealed that the temporal variation (or sampling availability) was large in this study. Careful consideration should be given to the sampling variability in handling the gelatinous zooplankton samples in coral reef areas.     

Microbial photosynthesis in coral reef sediments (Heron Reef, Australia)

We investigated microphytobenthic photosynthesis at four stations in the coral reef sediments at Heron Reef, Australia. The microphytobenthos was dominated by diatoms, dinoflagellates and cyanobacteria, as indicated by biomarker pigment analysis. Conspicuous algae firmly attached to the sand grains (ca. 100 μm in diameter, surrounded by a hard transparent wall) were rich in peridinin, a marker pigment for dinoflagellates, but also showed a high diversity based on cyanobacterial 16S rDNA gene sequence analysis. Specimens of these algae that were buried below the photic zone exhibited an unexpected stimulation of respiration by light, resulting in an increase of local oxygen concentrations upon darkening. Net photosynthesis of the sediments varied between 1.9 and 8.5 mmol O₂ m⁻² h⁻¹ and was strongly correlated with Chl a content, which lay between 31 and 84 mg m⁻². An estimate based on our spatially limited dataset indicates that the microphytobenthic production for the entire reef is in the order of magnitude of the production estimated for corals. Photosynthesis stimulated calcification at all investigated sites (0.2–1.0 mmol Ca²⁺ m⁻² h⁻¹). The sediments of at least three stations were net calcifying. Sedimentary N₂-fixation rates (measured by acetylene reduction assays at two sites) ranged between 0.9 to 3.9 mmol N₂ m⁻² h⁻¹ and were highest in the light, indicating the importance of heterocystous cyanobacteria. In coral fingers no N₂-fixation was measurable, which stresses the importance of the sediment compartment for reef nitrogen cycling.