Ecologica Montenegrina 39: 30-45 (2021) This journal is available online at: www.biotaxa.org/em http://dx.doi.org/10.37828/em.2021.39.4 First researches of the underwater ecosystem communities of an underground channel built in 1950s (Balaklava bay, Sevastopol) NELLY G. SERGEEVA1*, YURIY S. TARARIEV2, ROMAN V. GORBUNOV1, NIKOLAY K. REVKOV1 , NATALYA A. BOLTACHOVA1, GENNADIY V. SAMOKHIN3, ALEXANDER M. SHCHERBICH1, MAKSIM P. KIRIN 1, OLGA A. MIRONYUK1, LYUDMILA F. LUKYANOVA1 & VITALIY A. TIMOFEEV1 1 A.O. Kovalevsky Institute of Biology of the Southern Seas of RAS, Sevastopol, Russia 2 Military History Museum of Fortifications «Balaklava», Sevastopol, Russia 3 V.I. Vernadsky Crimean Federal University, Simferopol, Russia *E-mail: [email protected] Received 24 November 2020 │ Accepted by V. Pešić: 11 January 2021 │ Published online 20 January 2021. Abstract The results of the first studies of the ecosystem state of the underwater part of the channel, artificially created in the middle of the 20th century on the western shore of the Balaklava Bay (Sevastopol) as a naval base of the Black Sea Fleet for the submarines repair, are presented. Channel's ecosystem is determined by uniqueness of anthropogenic formation and considered as analogue of natural Black Sea cave. Hydrospelological survey of the channel and biological studies allowed assessing its current state, the nature of biofouling of its walls and anthropogenic and technical pollution of the bottom. Macrofauna of the channel wall biofouling is represented by the Mytilaster lineatus community, which has a high level of species abundance (about 80 species have been registered) and quantitative development. Both in taxonomic diversity and in quantitative terms, this community is comparable to the rocky substrate community near open Crimean coasts, but with a smaller share of crustacean group development. Due to weakened hydrodynamics, well developed fauna of bryozoans forming plurannual crusty structures and single sponges is observed on the channel's walls. In contrast to the channel walls biofouling, its bottom macrofauna has relatively lower quantitative and qualitative composition. Meiobenthos in the channel’s wall biofouling is represented by 18 higher taxa (type, class, order) of Protozoa and Metazoa with predominance of harpacticoids by abundance. Meiobenthos of the soft bottom of underground channel is represented by 15 higher taxa with predominance of free-living nematodes and harpacticoids by abundance. Average density of meiobenthos in the channel’s bottom sediments is comparable with similar parameters of its development in open water areas and Sevastopol bays. Key words: meiobenthos, macrobenthos, biodiversity, bottom sediments, biofouling, underwater channel, Balaklava bay, Black Sea. Ecologica Montenegrina, 39, 2021, 30-45 SERGEEVA ET AL. Introduction In connection with the planning of studies of the Black Sea coastal underwater caves and grottoes ecosystems of various genesis in the Crimea and the Caucasus by the Institute of Biology of Southern Seas of the Russian Academy of Sciences (Sevastopol), it is consistently that there is interest in the study of anthropogenic origin grottoes. The former secret facility of the Black Sea Fleet in the Balaklava Bay in Sevastopol is unique in this respect regard. Where it was housed the 155th Submarine Brigade, command and headquarters of the 14th Submarine Division after World War II. In the mid-1950s there began large-scale construction of a combined anti-nuclear shelter of the first class stability, which was completed in 1961. The underground complex was intended to shelter and service submarines in the event of a nuclear strike. It had a total area of 19 thous. square meters, cut down in Mount Tavros, which rises 126 meters above the western shore of the bay (Fig. 1A). The underground water channel runs through the mountain, which allowed to place 7 submarines of the project 613 or 9 submarines of the project A615 in it. By the end of XX century the anti-nuclear shelter lost its importance as a military facility, due to the rearmament of the fleet. In the early 2000s, the tunnel shafts of the underground complex for repair and maintenance of submarines were transformed into the Naval Museum Complex «Balaklava», which was opened on June 1, 2003. At that time, it was part of the Central Museum of the Ukrainian Armed Forces. On April 1, 2014 the museum complex was transformed into the Museum of Military History of Fortifications of the Russian Black Sea Navy Fleet. At present, the museum successfully conducts a multifaceted educational work. On the basis of surviving underground constructions, there are organized expositions about Sevastopol's Fortifications’ history, about former USSR Black Sea Fleet's submarine forces, and about military and political aspects of the «Cold War». The museum development plan provides for the creation of an underwater depository in the channel’s facility, installation of a decommissioned submarine in the museum, repair work on museum territories and creation of expositions devoted to the history of the Black Sea Federal Submarine Forces formation and development there. In this connection the task is set: to carry out underwater survey of underground channel by hydrospaeologists to determine current channel depth, bottom structure, presence of dangerous objects in its area, etc. Such information allow correct approach to channel area cleaning, if necessary, for further expansion of the unique underwater exposition. The second very important task is to describe the underwater ecosystem of the channel. In USSR times, no biological studies were conducted in this complex due to its special status. It seemed obvious that during the complex existence, the Black Sea fauna and flora of Balaklava Bay were able to inhabit the channel and adapt to new conditions of existence. However, during the study of bottom sediments in the entrance part of the tunnel shaft in 1992, no living forms of macrozoobenthos were found (Mironov et al. 1999). The tasks of our work included a detailed survey of the channel soft bottom sediments populations (macro- and meiobenthos) and wall fouling throughout the channel, as well as an assessment of taxonomic diversity and quantitative development of its fauna. Material and methods Research area. The study object is a channel (or tunnel shaft), which is a structure of atomic protection of the first class stability (protection against direct hit of atomic bomb with capacity of 100 kt, which is 5 times higher than the capacity of atomic bombing of Japan), which includes an underground water channel with a dry dock, section for repair of submarines, POL storage, mine-thorpedic section. This facility was especially important after the atomic bombing of Japanese cities Hiroshima and Nagasaki. The establishment of the underground complex has lasted for almost 8 years – from 1954 to 1961. Over 400 thousand cubic meters of rock were removed during construction. The thickness of concrete wall facing of the underground complex is 110 cm on average. The channel is located in Tavros Mountain (44°30'1.8"N, 33°35'48.48"E). It has an entrance closer to the apex part of the bay (Fig. 1A). Previously, if necessary, the entrance to the channel was blocked by a locking device – a gate caisson, whose weight reached 150 tons. Exit from the channel was equipped on the Ecologica Montenegrina, 39, 2021, 30-45 31 ECOSYSTEM COMMUNITIES OF AN UNDERGROUND CHANNEL IN CRIMEA southern side of the mountain and also overlapped with a gate caisson in the form of a stoplog gate (Fig. 1 B,C). Previously, both holes in the rock were skillfully closed with camouflage devices and nets. The total channel length is 608 meters, its central and southern sections have 12 meters wide and its northern section has 22 meters wide. Originally, its depth had reached 8 meters. The volume of water space (the channel and dry dock) is 76 thousand m3. Natural illumination of the water surface is available only in the entrance and exit areas; the channel has artificial illumination along its main length (Fig. 1 D,E). Figure 1. Museum of Military History of Fortifications "Balaklava" in Mount Tavros: A – entrance to the Museum from the side of the Balaklava Bay embankment (photo by A. Zatsepin); B – northern entrance part of the channel from the side of the embankment of the bay; C – southern entrance part of the channel; D, E – internal view of the channel with artificial illumination in its different parts. Local climate and microclimate of underground space. Description of the Balaklava Bay climate is presented in the special literature (Ved & Ena 2000). However, due to isolation of the investigated facility, we should be most interested in microclimate of artificial underground space located above the channel. Actual data on temperature regime monitoring are not available in the literature due to the facility specificity. However, according to microclimatic and morphological features the object "Submarine Base" can be classified as an "artificial cave" and take for the underground atmosphere the corresponding values of the average annual temperature of Sevastopol equal to + 13.2 ºC (Ilyin et al. 2012). To reveal the degree of influence of underground atmosphere temperature on water mass temperature in the underground channel – special studies are needed. Apart from the temperature, the category of factors that may determine the development of the channel photophilic biota should include the absence (in the central part of the channel) or limitation (in the entrance areas of the channel) of natural illumination. Physicochemical and hydrodynamic properties of water. No inflow of natural waters has been detected within this artificial structure. During the operation of the facility from 1950s to 2000s there was a potential possibility of both fresh and sewage water inflow in the form of leakages from communications into the artificial channel. However, at present, due to the museum status of the facility, fresh water leakages are practically eliminated.