Seagrass meadows of Pohnpei and And Atoll, Federated States of Micronesia, derived from field surveys conducted 26 October-03 November, 2005

Approximately 4,403.6 ±324.3 hectares (ha) of predominately intertidal and shallow subtidal seagrass meadows were mapped in the waters surrounding Pohnpei Island and And Atoll between 26 October and 3 November 2005. This was the first comprehensive survey of seagrass resources surrounding Pohnpei Island and And Atoll. The survey involved examination of 508 field validation points and identified 260 individual meadows. 3 species of seagrass (Cymodocea rotundata, Enhalus acoroides and Thalassia hemprichii) were identified in the shallow waters surrounding Pohnpei Island, and 2 species at And Atoll (Enhalus acoroides was absent). 21.3 ±11.8 hectares (ha) of seagrass was mapped in 8 meadows on the inner fringe of And Atoll.
Mapping survey methodologies followed standardised global seagrass research methods (McKenzie et al. 2001, doi:10.1016/B978-044450891-1/50006-2) where observers walked or free-dived to assess survey points. Seagrass habitat characteristics including visual estimates of above-ground percentage cover (3 replicates of a 50cm x 50cm quadrat) and species composition were recorded at each point according to the Seagrass-Watch standard methodologies (McKenzie 2003, http://bit.ly/2r4hQHk). Water depth and visual/tactile description of sediment were also recorded at each survey site. A differential handheld global positioning system (GPS) was used to locate each survey point (accuracy ±5m). Seagrass meadow boundaries were determined based on the positions of survey points and the presence of seagrass, coupled with depth contours and remote sensing (e.g. aerial photography) where available. The meadow boundary accuracy varied from 5m to 15m. The resulting data of each seagrass meadow was saved as an ArcMap shapefile and projected to WGS84 UTM Zone 57N.
Most seagrasses were found in water shallower than 3m and meadows were monospecific or consisted of multispecies communities, with up to 3 species present at a single location. 21 seagrass meadow community types were identified based on species presence and proportion of cover. Seagrass distribution appears to be primarily influenced by the degree of wave action (exposure), water clarity and nutrient availability. The dominant species encountered were Enhalus acoroides and Thalassia hemprichii. Pohnpei's seagrass habitats were categorised into six types: estuary, sheltered fringing reef, exposed fringing reef, patch reef, barrier reef and atoll.

2005年10月26日至11月3日期间，科研人员对波纳佩岛（Pohnpei Island）与安德环礁（And Atoll）周边海域开展海草床测绘工作，共完成约4403.6±324.3公顷的以潮间带与浅海亚潮带海草床为主的制图工作。这是首次针对波纳佩岛及安德环礁周边海草资源的全面普查。本次调查共布设508个野外验证点位，识别出260处独立海草床。在波纳佩岛周边浅海海域共发现3种海草：圆叶丝粉藻（Cymodocea rotundata）、海菖蒲（Enhalus acoroides）与安氏泰来藻（Thalassia hemprichii）；安德环礁仅发现2种海草，未检出海菖蒲。安德环礁内缘带的8处海草床共计测绘面积为21.3±11.8公顷。
本次测绘调查遵循全球标准化海草研究方法（McKenzie等，2001，doi:10.1016/B978-044450891-1/50006-2）开展，调查人员通过步行或自由潜水的方式核验各调查点位。每个点位均按照海草监测计划（Seagrass-Watch）的标准方法（McKenzie，2003，http://bit.ly/2r4hQHk）记录海草生境特征，包括50cm×50cm样方的3次重复地上盖度目视估算结果与物种组成。此外，每个调查点位还记录了水深以及沉积物的目视/触感描述。调查点位的定位采用差分手持全球定位系统（GPS），定位精度为±5米。海草床边界基于调查点位位置、海草分布情况，结合水深等值线与可用遥感数据（如航空摄影）确定，边界精度范围为5米至15米。最终各海草床的数据以ArcMap形状文件（ArcMap shapefile）格式存储，并投影至WGS84 UTM Zone 57N坐标系。
绝大多数海草床分布于水深小于3米的海域，海草群落可分为单物种群落或多物种群落，单个点位最多可同时存在3个物种。基于物种存在情况与盖度比例，共识别出21种海草床群落类型。海草分布主要受波浪作用强度（暴露程度）、水体透明度与营养盐可获得性的影响。本次调查中优势物种为海菖蒲与安氏泰来藻。波纳佩岛的海草生境可分为6类：河口、遮蔽型岸礁、暴露型岸礁、斑礁、堡礁与环礁。