Enhancement of phytoplankton biomass near island and atoll reef ecosystems—termed the Island Mass Effect (IME)—is an ecologically important phenomenon driving marine ecosystem trophic structure and fisheries in the midst of oligotrophic tropical oceans. This study investigated the occurrence of IME at Rangiroa Atoll in the French Polynesian Tuamotu archipelago, and the physical mechanisms driving IME, through the analysis of satellite and in situ data. Comparison of chlorophyll-a concentration near Rangiroa Atoll with chlorophyll-a concentration in open ocean water 50 km offshore, over a 16-year period, showed phytoplankton enhancement as high as 130% nearshore, over 75.7% of the study period. Our statistical model examining physical drivers showed the magnitude of IME to be significantly enhanced by higher sea surface temperature (SST) and lower photosynthetically active radiation (PAR). Further, in situ measurements of water flowing through Tiputa Channel revealed outflowing lagoon water to be warmer, lower in salinity, and higher in particulate load compared to ocean water. We suggest that water inside Rangiroa’s lagoon is enriched in nutrients and organic material by biological processes and advected as a result of tidal and wave forcing to coastal ocean waters, where it fuels primary production. We suggest that a combination of oceanographic and biological mechanisms is at play driving frequency and magnitude of IME at Rangiroa Atoll. Understanding the underlying processes driving IME at Rangiroa is essential for understanding future changes caused by a warming climate and changing environmental conditions for the marine ecosystem.

中文翻译：

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法属波利尼西亚朗吉罗阿环礁岛屿质量效应的长期存在

岛屿和环礁生态系统附近浮游植物生物量的增加——被称为岛屿质量效应 (IME)——是一种重要的生态现象，在贫营养热带海洋中推动海洋生态系统的营养结构和渔业。本研究通过对卫星和原位数据的分析，调查了法属波利尼西亚土阿莫土群岛朗吉罗阿环礁 IME 的发生，以及驱动 IME 的物理机制。在 16 年的时间里，朗吉罗阿环礁附近的叶绿素 a 浓度与离岸 50 公里的开阔海水中的叶绿素 a 浓度的比较表明，近岸浮游植物的增强率高达 130%，超过了研究期间的 75.7%。我们检查物理驱动因素的统计模型表明，较高的海面温度 (SST) 和较低的光合有效辐射 (PAR) 显着增强了 IME 的大小。此外，对流经蒂普塔海峡的水进行的现场测量显示，与海水相比，流出的泻湖水温度更高，盐度更低，颗粒负荷更高。我们认为，Rangiroa 泻湖内的水通过生物过程富含营养物质和有机物质，并由于潮汐和波浪强迫而平流到沿海海水，在那里为初级生产提供燃料。我们认为，海洋学和生物机制的结合正在驱动朗吉罗阿环礁 IME 的频率和幅度。