Data_Sheet_1_Detailed Mapping of Hydrothermal Vent Fauna: A 3D Reconstruction Approach Based on Video Imagery.pdf

Active hydrothermal vent fields are complex, small-scale habitats hosting endemic fauna that changes at scales of centimeters, influenced by topographical variables. In previous studies, it has been shown that the distance to hydrothermal fluids is also a major structuring factor. Imagery analysis based on two dimensional photo stitching revealed insights to the vent field zonation around fluid exits and a basic knowledge of faunal assemblages within hydrothermal vent fields. However, complex three dimensional surfaces could not be adequately replicated in those studies, and the assemblage structure, as well as their relation to abiotic terrain variables, is often only descriptive. In this study we use ROV video imagery of a hydrothermal vent field on the southeastern Indian Ridge in the Indian Ocean. Structure from Motion photogrammetry was applied to build a high resolution 3D reconstruction model of one side of a newly discovered active hydrothermal chimney complex, allowing for the quantification of abundances. Likewise, the reconstruction was used to infer terrain variables at a scale important for megabenthic specimens, which were related to the abundances of the faunal assemblages. Based on the terrain variables, applied random forest model predicted the faunal assemblage distribution with an accuracy of 84.97 %. The most important structuring variables were the distances to diffuse- and black fluid exits, as well as the height of the chimney complex. This novel approach enabled us to classify quantified abundances of megabenthic taxa to distinct faunal assemblages and relate terrain variables to their distribution. The successful prediction of faunal assemblage occurrences further supports the importance of abiotic terrain variables as key structuring factors in hydrothermal systems and offers the possibility to detect suitable areas for Marine Protected areas on larger spatial scales. This technique works for any kind of video imagery, regardless of its initial purpose and can be implemented in marine monitoring and management.

活跃热液喷口区（active hydrothermal vent fields）是一类复杂的小型生境，栖息有特有物种群落，其群落组成的变化尺度可达厘米级，且受地形变量调控。既往研究表明，与热液流体的距离同样是塑造群落结构的核心因子。基于二维照片拼接的影像分析，曾为解析喷口区流体出口周边的分带格局，以及热液喷口区内物种群落组成提供了认知基础。但此类研究无法充分复现复杂的三维地形表面，且群落结构及其与非生物地形变量的关联往往仅停留在描述性层面。本研究使用印度洋东南印度洋脊某热液喷口区的遥控水下机器人（Remotely Operated Vehicle，ROV）影像数据。通过运动恢复结构（Structure from Motion, SfM）摄影测量技术，构建了一处新发现的活跃热液烟囱群单侧的高分辨率三维重建模型，实现了物种丰度的定量化分析。同时，该重建模型被用于推导大型底栖生物（megabenthic specimens）生存关键尺度下的地形变量，并将其与物种群落的丰度相关联。基于上述地形变量，应用随机森林（Random Forest）模型预测物种群落分布的准确率可达84.97%。影响群落结构的核心变量包括与弥散热液流体出口、黑热液流体出口的距离，以及热液烟囱群的高度。该创新性方法使我们能够将定量化的大型底栖生物类群丰度划分为不同的物种群落，并明确地形变量与其分布的关联。对物种群落出现情况的成功预测，进一步证实了非生物地形变量作为热液系统核心结构因子的重要性，同时为在更大空间尺度上划定海洋保护区（Marine Protected Areas, MPAs）的适宜区域提供了可行路径。该技术适用于任何类型的影像数据，无需考虑其初始应用场景，可直接应用于海洋监测与管理工作中。