A new underwater karst phenomenon along the west coast of the Salento Peninsula (Italy): The "Enzo Manieri-Elia" Cave

On August 2019 cave divers belonging to the Apogon Submarine Speleology Centre of Nardò (Italy) explored an underwater cave located among other submerged and semi-submerged karst phenomena of the Salento (South-Est Italy) Ionian coast. The Italian caves register (which includes more than 33,000 karstic natural environments) represents an important source of information for research purposes. The Apulian register (established by the regional law 33/2009 and made by the Apulian Speleological Federation) comprehends about 2650 natural caves discovered within a territory which is more than 80% made up of carbonate rocks. The exploration and the topography, video and photographic documentation of the submerged cave allowed to include this karst phenomenon (PU/LE 1836 identification code) within the Apulian register. The investigation area is part of the Municipality of Nardò (LE), between the localities of Santa Maria al Bagno and the Regional Natural Park Porto Selvaggio e Palude del Capitano. The underwater cave was explored by the means of cave-diving techniques aiming at the planimetric representation, the documentation of the aquatic system and the protection of the naturalistic and cultural heritage represented by the karst environments thanks to the Apulian Caves official register. The diving equipment was based on a specific and redundant air breathing apparatus (A.R.A.), comprehending reels and a helmets with three or four flashlights. The first part of the cave, whose door is at about 8 meters deep, has a pebbly bottom extended for about 10 m. Then the bottom becomes muddy. The second room of the cave comprehend a central column and emerged areas (air bubbles). Following a flow of cold water it is possible to go in a small chamber oriented on the NNO-SSE axis where there is a large group of small "biostalactites strictly oriented in the direction of the current which will be for" brevity called "trays" in the following parts of the text. The first examples of trays were found along the East coast of the Salento peninsula within another submerged cave named Lu Lampiune, in Otranto (LE), in the 1990s. One of these trays was taken from Lu Lampiune and a longitudinal section was examined to ascertain the internal central axis composition, which resulted to be made by calcareous tubes of invertebrate filtering sessile polychaetes of the Serpulidae family, incorporated and coated at the death of the animal by microcrystalline material of probable sedimentary origin. The trays found in Grotta Enzo Manieri-Elia are smaller and presumably younger than those of Lu Lampiune. Future studies could evaluate their specific organogenic structure.

2019年8月，意大利纳尔杜市的阿波贡水下洞穴学中心（Apogon Submarine Speleology Centre）的洞穴潜水员，对位于意大利东南部萨伦托半岛爱奥尼亚海岸的一处水下洞穴开展了勘探，该区域分布有多处淹没及半淹没喀斯特（karst）地貌。意大利洞穴登记库（涵盖超过33000处喀斯特自然环境）是开展相关研究的重要信息来源。由2009年第33号区域法令设立、普利亚洞穴联合会（Apulian Speleological Federation）负责编制的普利亚洞穴登记库，涵盖了该区域内已发现的约2650处天然洞穴，该区域80%以上的地表由碳酸盐岩构成。本次勘探的水下洞穴经地形测绘、视频及影像记录后，已被以识别码PU/LE 1836纳入普利亚洞穴官方登记库。该勘探区域隶属于纳尔杜市（莱切省，LE）辖区，地处圣玛丽亚阿尔巴尼奥与塞尔瓦焦港及卡皮塔诺沼泽区域自然公园之间。本次水下洞穴勘探采用洞穴潜水技术，旨在通过普利亚洞穴官方登记库完成该水下水系的平面测绘、记录，并保护喀斯特环境所承载的自然与文化遗产。潜水装备采用专用冗余式空气呼吸装置（A.R.A.，Air Breathing Apparatus），配备卷线器及搭载3至4枚手电筒的头盔。该洞穴的入口位于约8米水深处，首段洞道底床为砾石质，延伸长度约10米，随后底床变为淤泥质。洞穴的第二室包含一根中央柱体与出露水面区域（伴随空气泡）。沿冷水流方向行进，可进入一处沿NNO-SSE轴延伸的小型腔室，腔内分布有大量沿水流方向严格定向生长的小型生物钟乳石（biostalactites），为行文简洁起见，下文将其统称为"托盘状构造（trays）"。1990年代，科研人员在萨伦托半岛东海岸奥特朗托市（莱切省，LE）的另一处名为卢兰皮乌内（Lu Lampiune）的水下洞穴中，发现了首批此类托盘状构造。研究人员曾从卢兰皮乌内洞穴中提取一件托盘状构造样本，并对其纵剖面开展分析以确定其内部中央轴的构成，结果显示其内部中央轴由龙介虫科（Serpulidae）固着滤食性无脊椎多毛类动物的钙质管构成，该动物死亡后，其管体被可能源自沉积作用的微晶物质包裹覆盖。本次在恩佐·马涅里-埃利亚洞穴（Grotta Enzo Manieri-Elia）中发现的托盘状构造，尺寸小于卢兰皮乌内洞穴的样本，形成时间也相对更晚。后续研究可针对其专属的有机成因结构展开进一步评估。