Fajemila Olugbenga T, Langer Martin R, Lipps Jere H
Steinmann-Institut für Geologie, Mineralogie und Paläontologie, Rheinische Friedrich-Wilhelms Universität, Bonn, Germany.
Department of Geological Sciences, Osun State University, Osogbo, Nigeria.
PLoS One. 2015 Dec 28;10(12):e0145752. doi: 10.1371/journal.pone.0145752. eCollection 2015.
Coral reefs are now subject to global threats and influences from numerous anthropogenic sources. Foraminifera, a group of unicellular shelled organisms, are excellent indicators of water quality and reef health. Thus we studied a set of samples taken in 1992 to provide a foraminiferal baseline for future studies of environmental change. Our study provides the first island-wide analysis of shallow benthic foraminifera from around Moorea (Society Archipelago). We analyzed the composition, species richness, patterns of distribution and abundance of unstained foraminiferal assemblages from bays, fringing reefs, nearshore and back- and fore-reef environments. A total of 380 taxa of foraminifera were recorded, a number that almost doubles previous species counts. Spatial patterns of foraminiferal assemblages are characterized by numerical abundances of individual taxa, cluster groups and gradients of species richness, as documented by cluster, Fisher α, ternary plot and Principal Component Analyses (PCA). The inner bay inlets are dominated by stress-tolerant, mostly thin-shelled taxa of Bolivina, Bolivinella, Nonionoides, Elongobula, and Ammonia preferring low-oxygen and/or nutrient-rich habitats influenced by coastal factors such as fresh-water runoff and overhanging mangroves. The larger symbiont-bearing foraminifera (Borelis, Amphistegina, Heterostegina, Peneroplis) generally live in the oligotrophic, well-lit back- and fore-reef environments. Amphisteginids and peneroplids were among the few taxa found in the bay environments, probably due to their preferences for phytal substrates and tolerance to moderate levels of eutrophication. The fringing reef environments along the outer bay are characterized by Borelis schlumbergeri, Heterostegina depressa, Textularia spp. and various miliolids which represent a hotspot of diversity within the complex reef-lagoon system of Moorea. The high foraminiferal Fisher α and species richness diversity in outer bay fringing reefs is consistent with the disturbance-mosaic (microhabitat heterogeneity) hypothesis. Calculations of the FORAM Index (FI), a single metric index to assess reef vitality, indicate that all fore- and most back-reef environments support active carbonate accretion and provide habitat suitability for carbonate producers dependent on algal symbiosis. Lowest suitability values were recorded within the innermost bays, an area where natural and increasing anthropogenic influences continue to impact the reefs. The presence of habitat specific assemblages and numerical abundance values of individual taxa show that benthic foraminifera are excellent recorders of environmental perturbations and good indicators useful in modern and ancient ecological and environmental studies.
珊瑚礁如今正受到来自众多人为来源的全球威胁和影响。有孔虫是一类单细胞带壳生物，是水质和珊瑚礁健康状况的优良指示生物。因此，我们研究了1992年采集的一组样本，为未来的环境变化研究提供有孔虫基线。我们的研究首次对来自莫雷阿岛（社会群岛）周边浅海海底有孔虫进行了全岛范围的分析。我们分析了来自海湾、边缘礁、近岸以及礁前和礁后环境中未染色有孔虫组合的组成、物种丰富度、分布模式和丰度。共记录了380种有孔虫分类单元，这一数量几乎是之前物种数量的两倍。有孔虫组合的空间模式以单个分类单元的数量丰度、聚类组以及物种丰富度梯度为特征，这已通过聚类分析、费希尔α多样性指数、三元图和主成分分析（PCA）得到证明。内湾入口处主要是耐胁迫的有孔虫，大多是薄壳的玻利维纳属、小玻利维纳属、类诺宁虫属、长圆虫属和氨型虫属，它们偏好受淡水径流和悬垂红树林等海岸因素影响的低氧和/或营养丰富的栖息地。较大的含共生体有孔虫（包氏虫属、双壁虫属、异壁虫属、笔石虫属）通常生活在贫营养、光照良好的礁前和礁后环境中。双壁虫科和笔石虫科是在海湾环境中发现的少数分类单元之一，这可能是由于它们偏好植物基质并能耐受中等程度的富营养化。外湾沿岸的边缘礁环境以施氏包氏虫、扁平异壁虫、编织虫属物种以及各种粟粒虫为特征，这些代表了莫雷阿岛复杂礁湖系统中的一个多样性热点。外湾边缘礁中较高的有孔虫费希尔α多样性指数和物种丰富度多样性与干扰镶嵌体（微生境异质性）假说一致。用于评估珊瑚礁活力的单一指标——有孔虫指数（FI）的计算结果表明，所有礁前和大部分礁后环境都支持活跃的碳酸盐堆积，并为依赖藻类共生的碳酸盐生产者提供适宜的栖息地。在最内侧海湾记录到最低的适宜性值，该区域自然和不断增加的人为影响持续对珊瑚礁造成冲击。特定栖息地组合的存在以及单个分类单元的数量丰度值表明，底栖有孔虫是环境扰动的优良记录者，也是现代和古代生态与环境研究中有用的指示生物。
