Cresswell Anna K, Ryan Nicole M, Heyward Andrew J, Smith Adam N H, Colquhoun Jamie, Case Mark, Birt Matthew J, Chinkin Mark, Wyatt Mathew, Radford Ben, Costello Paul, Gilmour James P
Australian Institute of Marine Science, Perth, WA, Australia.
Oceans Institute, University of Western Australia, Perth, WA, Australia.
PeerJ. 2021 Apr 14;9:e11090. doi: 10.7717/peerj.11090. eCollection 2021.
Novel tools and methods for monitoring marine environments can improve efficiency but must not compromise long-term data records. Quantitative comparisons between new and existing methods are therefore required to assess their compatibility for monitoring. Monitoring of shallow water coral reefs is typically conducted using diver-based collection of benthic images along transects. Diverless systems for obtaining underwater images (e.g. towed-cameras, remotely operated vehicles, autonomous underwater vehicles) are increasingly used for mapping coral reefs. Of these imaging platforms, towed-cameras offer a practical, low cost and efficient method for surveys but their utility for repeated measures in monitoring studies has not been tested. We quantitatively compare a towed-camera approach to repeated surveys of shallow water coral reef benthic assemblages on fixed transects, relative to benchmark data from diver photo-transects. Differences in the percent cover detected by the two methods was partly explained by differences in the morphology of benthic groups. The reef habitat and physical descriptors of the site-slope, depth and structural complexity-also influenced the comparability of data, with differences between the tow-camera and the diver data increasing with structural complexity and slope. Differences between the methods decreased when a greater number of images were collected per tow-camera transect. We attribute lower image quality (variable perspective, exposure and focal distance) and lower spatial accuracy and precision of the towed-camera transects as the key reasons for differences in the data from the two methods and suggest changes to the sampling design to improve the application of tow-cameras to monitoring.
用于监测海洋环境的新型工具和方法可以提高效率，但绝不能损害长期数据记录。因此，需要对新方法和现有方法进行定量比较，以评估它们在监测方面的兼容性。浅水珊瑚礁监测通常是通过潜水员沿样带收集底栖生物图像来进行的。用于获取水下图像的非潜水员系统（如拖曳式摄像机、遥控潜水器、自主水下航行器）越来越多地用于珊瑚礁测绘。在这些成像平台中，拖曳式摄像机为调查提供了一种实用、低成本且高效的方法，但其在监测研究中进行重复测量的效用尚未得到检验。我们将拖曳式摄像机方法与在固定样带上对浅水珊瑚礁底栖生物群落进行重复调查的方法进行了定量比较，并与潜水员照片样带的基准数据进行了对比。两种方法检测到的覆盖百分比差异部分可归因于底栖生物群体形态的差异。礁体栖息地以及场地的坡度、深度和结构复杂性等物理描述符也影响了数据的可比性，拖曳式摄像机和潜水员数据之间的差异随着结构复杂性和坡度的增加而增大。当每个拖曳式摄像机样带收集更多图像时，两种方法之间的差异会减小。我们将较低的图像质量（视角、曝光和焦距可变）以及拖曳式摄像机样带较低的空间准确性和精度视为两种方法数据存在差异的关键原因，并建议对采样设计进行改进，以提高拖曳式摄像机在监测中的应用。
