Data_Sheet_1_First ROV Exploration of the Perth Canyon: Canyon Setting, Faunal Observations, and Anthropogenic Impacts.pdf

This study represents the first ROV-based exploration of the Perth Canyon, a prominent submarine valley system in the southeast Indian Ocean offshore Fremantle (Perth), Western Australia. This multi-disciplinary study characterizes the canyon topography, hydrography, anthropogenic impacts, and provides a general overview of the fauna and habitats encountered during the cruise. ROV surveys and sample collections, with a specific focus on deep-sea corals, were conducted at six sites extending from the head to the mouth of the canyon. Multi-beam maps of the canyon topography show near vertical cliff walls, scarps, and broad terraces. Biostratigraphic analyses of the canyon lithologies indicate Late Paleocene to Late Oligocene depositional ages within upper bathyal depths (200–700 m). The video footage has revealed a quiescent ‘fossil canyon’ system with sporadic, localized concentrations of mega- and macro-benthos (∼680–1,800 m), which include corals, sponges, molluscs, echinoderms, crustaceans, brachiopods, and worms, as well as plankton and nekton (fish species). Solitary (Desmophyllum dianthus, Caryophyllia sp., Vaughanella sp., and Polymyces sp.) and colonial (Solenosmilia variabilis) scleractinians were sporadically distributed along the walls and under overhangs within the canyon valleys and along its rim. Gorgonian, bamboo, and proteinaceous corals were present, with live Corallium often hosting a diverse community of organisms. Extensive coral graveyards, discovered at two disparate sites between ∼690–720 m and 1,560–1,790 m, comprise colonial (S. variabilis) and solitary (D. dianthus) scleractinians that flourished during the last ice age (∼18 ka to 33 ka BP). ROV sampling (674–1,815 m) spanned intermediate (Antarctic Intermediate Water) and deep waters (Upper Circumpolar Deep Water) with temperatures from ∼2.5 to 6°C. Seawater CTD profiles of these waters show consistent physical and chemical conditions at equivalent depths between dive sites. Their carbonate chemistry indicate supersaturation (Ωcalcite ∼ 1.3–2.2) with respect to calcite, but mild saturation to undersaturation (Ωaragonite ∼ 0.8–1.4) of aragonite; notably some scleractinians were found living below the aragonite saturation horizon (∼1,000 m). Seawater δ13C and nuclear bomb produced Δ14C compositions decrease in the upper canyon waters by up to ∼0.8‰ (

本研究标志着首次采用遥控潜水器（ROV）对珀斯峡谷的探索，该峡谷是南印度洋东南部弗里曼特尔（珀斯）附近一个显著的海底峡谷系统。本研究为多学科性质，对峡谷地形、水文、人为影响进行了描述，并对巡航过程中遇到的生物群落和栖息地进行了概述。在峡谷头部至出口的六个地点，进行了ROV调查和样本采集，特别关注深海珊瑚。峡谷地形的多波束图显示了近乎垂直的悬崖壁、陡坡和宽阔的平台。对峡谷岩石的生物地层分析表明，沉积年龄属于晚始新世至晚渐新世，位于上层水深（200-700米）范围内。视频资料揭示了一个宁静的‘化石峡谷’系统，其中存在稀疏、局部的巨型和大型底栖生物群（约680-1,800米），包括珊瑚、海绵、软体动物、棘皮动物、甲壳类、腕足动物和环节动物，以及浮游生物和鱼类。孤独的（Desmophyllum dianthus、Caryophyllia sp.、Vaughanella sp.和Polymyces sp.）和群居的（Solenosmilia variabilis）石珊瑚在峡谷山谷的墙壁和悬壁下以及峡谷边缘的稀疏分布。海葵、竹状和蛋白质珊瑚存在，活珊瑚经常承载着多种生物群落。在约690-720米和1,560-1,790米之间的两个不同地点发现了广泛的珊瑚墓地，包括群居的（S. variabilis）和孤独的（D. dianthus）石珊瑚，这些珊瑚在最后一个冰河时期（约18 ka至33 ka BP）繁荣生长。ROV采样（674-1,815米）涵盖了中间水（南极中间水）和深水（上层环极深水），水温从约2.5到6°C不等。这些水域的海水CTD剖面显示，在潜水地点的等效深度上，物理和化学条件保持一致。其碳酸盐化学成分表明，相对于方解石，存在过饱和（Ωcalcite ∼ 1.3-2.2），但对方解石而言，饱和或亚饱和（Ωaragonite ∼ 0.8-1.4）；值得注意的是，一些石珊瑚被发现生活在方解石饱和层以下（约1,000米）。上层峡谷水域的海水δ13C和核爆产生的Δ14C组成减少了约0.8‰（