Changes in coral reef communities along a gradient of river discharge, Pohnpei, Micronesia

Change to coral communities along a gradient of increasing exposure to a mud-discharging river in the Enipein Catchment, Pohnpei, Micronesia were quantified by the two principal authors (PICRC) using video transects at 5 sites, each with 3 replicate stations. Site 1 was closest to the river mouth and Site 5 farthest away (just under 2 km).For each of 75 20 m transects, 200 sample points were generated by stopping the video every 2-3 s and identifying benthos under 5 fixed sample points on the screen (40 frames per transect). Cover was estimated for the benthos categories: abiotic substrata were recorded as carbonate (consolidated, including crustose coralline algae), mud (only used so thick no other substratum was visible), sand or rubble. Hard corals (scleractinia) were identified to the genus level where possible; corals in the Faviidae and Fungiidae were recorded to the family level; the three most abundant Porites taxa were recorded separately (massive Porites, Porites cylindrica, and Porites rus); unidentfied corals were grouped together - 24 species were identified. Other benthic groups recorded were: the calcareous green alga Halimeda, other macroalgae, soft corals, the calcareous hydrozoan Millepora, and sponges. To analyse in detail how, and at what scale, coral reef communities are affected by changes along a water quality gradient moving away from the mouth of a river in a small island setting.To contribute to understanding of coral reef communities and potential changes in response to increased terrestrial runoff. Corals identified: Acropora spp., Astreopora, Echinopora, Faviidae, Fungiidae, Galaxea, Goniopora, Hydnophora, massive Porites, Millepora, Montipora, Oxypora, Pachyseris spp., Pavona spp., Pectinia, Plerogyra, Pocillopora, Porites spp., Porites cylindrica, Porites foliose, Porites rus, Seriatopora, Stylophora, Symphyllia, Turbinaria spp.Lobophyllia, Echinophyllia

密克罗尼西亚联邦波纳佩州埃尼皮恩（Enipein）流域内，沿排泥河流暴露梯度变化的珊瑚群落，由两位主要作者（PICRC）通过视频样带法开展量化研究：共设置5个调查站点，每个站点布设3个重复站位。站点1紧邻河口，站点5距河口最远（距离略小于2公里）。
针对75条20米长的视频样带，每2-3秒暂停视频，识别屏幕上5个固定采样点对应的底栖生物（每条样带采集40帧），总计生成200个采样点。对以下底栖生物类别进行盖度估算：非生物基质分为碳酸盐基质（固结型，包含壳状珊瑚藻）、泥质基质（仅当泥层过厚无其他基质可见时记录）、沙质或砾石基质。
硬珊瑚（石珊瑚目（Scleractinia））尽可能鉴定至属水平；蜂巢珊瑚科（Faviidae）与石芝珊瑚科（Fungiidae）仅鉴定至科水平；3种丰度最高的滨珊瑚属（Porites）类群单独记录：块状滨珊瑚、圆柱滨珊瑚（Porites cylindrica）以及丛状滨珊瑚（Porites rus）；无法鉴定的珊瑚统一归为一类，本次研究共鉴定出24种珊瑚。
记录的其他底栖生物类群包括：钙绿藻属（Halimeda）、其他大型藻类、软珊瑚、钙质水螅虫类千手珊瑚属（Millepora）以及海绵。
本研究旨在详细解析小型岛屿环境中，沿河口向陆源径流变化的水质梯度下，珊瑚礁群落在何种尺度、以何种方式受到影响；同时助力理解珊瑚礁群落及其对增强型陆源径流的潜在响应变化。
本次鉴定的珊瑚类群包括：轴孔珊瑚属（Acropora）物种、星孔珊瑚属（Astreopora）、棘孔珊瑚属（Echinopora）、蜂巢珊瑚科（Faviidae）、石芝珊瑚科（Fungiidae）、杯形珊瑚属（Galaxea）、牡丹珊瑚属（Goniopora）、棘珊瑚属（Hydnophora）、块状滨珊瑚、千手珊瑚属（Millepora）、微孔珊瑚属（Montipora）、尖孔珊瑚属（Oxypora）、厚丝珊瑚属（Pachyseris）物种、叶状珊瑚属（Pavona）物种、梳状珊瑚属（Pectinia）、泡囊珊瑚属（Plerogyra）、杯形珊瑚属（Pocillopora）、滨珊瑚属（Porites）物种、圆柱滨珊瑚（Porites cylindrica）、叶状滨珊瑚（Porites foliose）、丛状滨珊瑚（Porites rus）、排孔珊瑚属（Seriatopora）、柱星珊瑚属（Stylophora）、脑纹珊瑚属（Symphyllia）、盾形陀螺珊瑚属（Turbinaria）物种、叶状珊瑚属（Lobophyllia）、棘叶珊瑚属（Echinophyllia）