Deep Seas

For the world seas, marine areas with depths exceeding 200 m, the lower limits of the continental shelf, are described as ‘deep seas’.  These sensitive ecosystems are home to mostly localized, non-migratory, long-lived, slow-maturing species with particular, species-specific, specialized ecological strategies (Politou et al., 2003).

As light can penetrate approximately up to 200 metres in the seas (Lalli and Parsons, 2006), deep seas tend to be dark and high pressure habitats.  This region, formed after long geological and biological processes, has many unique and unparalleled ecosystems while being threatened by various anthropological activities.  We have very limited knowledge about this dark world.

Deep seas are difficult to reach and study in terms of scientific research due to lack of proper equipment and specialists, as well as financial difficulties.  Insufficient number of scientific work exists for our deep sea regions.  Only biological studies with narrow fields of research and survey efforts with foreign partners have been possible.  Deep sea research is not only extremely costly but also requires great effort because of difficulties in application.  In recent years, with rapid developments in underwater technology, number of deep sea research has greatly increased with several countries racing to discover the dark world beneath, trying novel equipment, leading to new exploration and increasing interest in underwater mining.

Size of deep sea species are adapted to their unique ecological strategies and habitats.  Increased predation, less competition and limited food supply in these isolated environments cause complex evolutionary process and in their body size.  While decreased size is correlated to limited food supply in taxon, gigantism is correlated to decreased predation and temperature.  As an example to gigantism, (growth in species’ body sizes with increasing depth) fish from the Regalecidae family are excellent as they can reach up to 8 m with increasing depth (Froese and Pauly, 2007). Macrocheira kaempferi (Japanese spider crab) is found at up to 600 m of depth and 3.7 m in size (McClain et al., 2015).  Jellyfish belonging to the genus of Stygiomedusa can reach up to 10 meters in size are thought to be one of the biggest invertebrate hunters in the ecosystem (Bourton, 2010; MSIP, 2020).  Giant squid Architeuthis dux can reach up to 13 m and may be found at 1000 m of depth (Atkinson, 2008).  These are only a few examples of just how large a deep sea marine organism can become (Figure 1).

Figure 1. Giant squid and Japanese spider crab

Deep Sea Research

First comprehensive data about the depths of the ocean was from the Challenger study between 1872 and 1876.  First findings about the deep sea marine organisms of the Mediterranean were gathered by the studies of Pola between 1890 and 1893, by Dana between 1908 and 1910 and by Thor between 1921 and 1922 (Cartes et al. 2004).  First findings about the creatures that live in the depths of the Mediterranean was presented by Risso (1816) according to Cartes et al. 2004. First comprehensive study on the Eastern Mediterranean Sea fauna was from the Danish Oceanography research, conducted between 1908 and 1910 (Danovaro et al., 2010).

Our nation’s deep sea research remains insufficient. First study conducted on the deep sea species of our seas by Turkish researchers was the study by Demir (1958).  In 1955 and 1956 spring and summer, first Turkish research vessel ‘Arar’ (Searcher) conducted surveys with a 2 m scoop and discovered Cyclothone braueri (Jespersen & Tåning, 1926) at the Northern Aegean Sea, 450 to 830 m of depth, Stomias boa (Risso, 1810) and Benthosema glaciale (Reinhardt, 1837) in the Marmara Sea at 100 to 860 m of depth, obtaining first records of these 3 fish species.

After these initial attempts, the most comprehensive deep sea studies were conducted in 2007 and 2008 by the YUNUS – ship of the İstanbul University, Department of Aquaculture, in the national and international waters of Eastern Mediterranean and Aegean Sea.  These expeditions are first in the history of Turkish marine sciences and resulted in important scientific data published on the seas of our nation.  Samples from Anaximander seamount have been analyzed and this region was declared as a Specially Protected Area on 22 July 2013 with the contributions of TUDAV.

Onur Gönülal’s PhD thesis (advised by Prof. Dr. Bayram Öztürk, our foundations president) took place at the depths of the Northern Aegean Sea from 500 m to 1500 m and sampled, for the first time, marine organisms living under 1000 m of depth.  Aside from multiple new records for the Turkish waters, a new tomopterid worm, Augeneria profundicola sp. has been discovered and named.

Deep Sea Vehicles and Equipment

The main reason for us having so little information of dep seas stems from the extremely high cost and razor-edge technological equipment necessary for the studies, placing them next to space exploration in humanity’s timeline.  Russian Federation sent its first spaceship ‘Luna 2’ to the moon in 1915 and sent cosmonaut Yuri Gagarin to Earth’s orbit with Vostok 1 in 1961.  Around the same time in 23 January 1960, Swiss scientist Jacques Piccard and US Navy general Donald Walsh descended to the deepest marine region known to man, the Mariana Trench, with a midget submarine named Trieste (Anonymous, 2011). Designed by the Swiss and built by Italians, this submarine has been used in numerous research expeditions.  It’s been on exhibition in USA Navy’s National Museum in Washington Navy Gardens since 1980 (Anonymous, 2015).  Operated by Canadian Director James Cameron, Deepsea Challenger (DSV 1) has descended into the Mariana Trench for the second time in 26 March 2012, 52 years after the first dive that made history.  A depth of 10,898 m has been reached after diving for 2 hours and 36 minutes.  Submarine Archimede belonging to the French army, built in 1961, has been used for deep sea exploration until 1970s.  Along with Trieste, Archimede spearheaded deep sea exploration with the 9300 m Kuril-Kamchatka Trench dive south of Tokyo ın 1962 and with the 8400 m Puerto Rico Trench dive in 1964.

Designed by U.S. Triton submarines and operated by Victor Vescovo, the submarine DSV Limiting Factor broke a new record by reaching 10,928 m of depth in the Mariana Trench on 28 April 2019.  Plastic waste has been recorded at these depths (Thebault, 2019). Victor Vescovo has also been the first person to reach 5550 m at the Arctic Ocean’s Molloy Trench on 24 August 2019 (Amos, 2019).  As of 2019, the submarine system has been valued at 5 million dollars (Triton, 2019).

SHINKAI 6500, belonging to Japan, was made in 1990 and held the title of deepest manned submarine for a long time, until Deepsea Challenger began its expeditions (Figure 2).

Figure 2. SHINKAI 6500

Last but not least, the highest number of expeditions were made by DSV Alvin, a midget submarine owned by the U.S. army and belonging to Woods Hole Oceanographic Institution – more than 5000 dives resulting in approximately 2000 scientific articles (Figure 3).  Hydrothermal vents in the Northern Pacific Ocean have been semi-regularly visited by deep sea researchers as year-round monitoring sites for the last two decades (Luther et al.,2012).  Almost every discovery in this area has been made with DSV Alvin. Mustafa Yücel and Batuhan Yapan became the deepest diving Turkish citizens when they dived with DSV Alvin at the ATL-37-11 expedition.  Since May 2017 public scientific forums have been held on TUDAV and METU ‘s public web sites (Yücel et al. 2017).

Figure 3. DSV Alvin

Our country has few studies conducted with midget submarines.  In October 1992, in a Turkey-Russia partnership, Argus submarine dived to 575 m of depth to gather information about the current situation of the Marmara Sea ecosystem (Öztürk et al. 2017).  The Turkish researchers joining the expedition included Prof. Bayram Öztürk, Dr. Meriç Albay, Dr. Ayhan Dede, Adnan Sümer, Mustafa Cebeci and Gürol Şimşek.  In another midget submarine study, Prof. Dr. Naci Görür Kuzey from ITU dived to 1239 metres of on 31 May 2007 to investigate the Marmara line of a Anatolia faultline and the visuals have been shared on the CD of the book ‘Travel to the Faultline’ (Görür, 2000) (Figure 4).


Figure 4. Argus midget submarine

In our country, underwater (submarine) activities are conducted for military purposes and sadly without scientific intention or application.

Cost-effective ROVs (Remotely Operated Underwater Vehicles) are usually preferred to midget submarines in deep sea studies.  Numerous ROVs are used for scientific purposes.  One of the most technologically advanced ROVs is Nereus, built by Woods Hole Oceanographic Institution (WHOI), able to dive 11,000 m of depth.  Hercules and Argus on the Ocean Exploration Trust’s (Dr. Robert Ballard, 2008) E/V Nautilus expedition vessel are two other valuable ROVs.  E/V Nautilus held expeditions in our country between 2009 and 2012, and discovered numerous eddies and sunken ships.  In 2010, at depths between 1300 to 2000 m in the Eastern Mediterranean, numerous underwater volcanic mountains with complex tectonic structures such as Anaximander seamount and dirt volcanoes have been explored (Tüzün, 2017).  TUDAV board member Dr. Onur Gönülal attended some of the research.

In recent years, various private firms have begun building ROVs, most able to descend to 1000 m of depth.  THE ROV used by MTA can work at 3000 m.

More cost effective methods are preferred in most studies.  Cages with feeders are productive for scientific and fisheries purposes, as well as harmless to the ecosystem.  Fishing with bottom nets in the North Atlantic Ocean at more than 600 m of depth was common, but most boats switched to the Indian Ocean after bans and prohibitions were put in place (Figure 5).

Figure 5. Cage and bottom nets used for deep seas

Deep Sea Mining

Discovery of minerals at seabeds in deep sea was made between 1872 and 1876 with H.M.S. Challenger expeditions – also known as the beginning of ocean science.  Governments began showing interest in seabed mining towards mid-20th century.  Mining the deep sea is a novel concept even though undersea mining has existed for years.  Numerous developed countries have gravitated towards deep sea mining, primarily to obtain crude materials, but also for geopolitical and economic reasons (Birney et al., 2006).  Research indicates that seabeds of the deep have 22 billion tons of industrially important elements like Nickel, Zinc and Cobalt in manganese nodules (Figure 6).  The tenor of the of deep sea ores are estimated to be 2 to 10 times more than land-based sources, but this subject has only recently been on governmental agendas (Karapınar, 2015; Demirsoy, 1972).

Figure 6. Manganese nodules discovered in the Atlantic Ocean in 2019

D/V Chikyu (JAMSTEC), a marine and earth sciences focused Japanese National Research Institute ship is world’s first scientific ship equipped with amplifier (Figure 7).  The drill’s length is approximately 10,000 m long with the amplifier.  D/V Chikyu continues to gather scientific data to measure deep sea energy from underwater life, underwater resources and global climate change levels.

Figure 7. D/V Chikyu Scientific Drilling Vessel

First ocean-deep sea mining application is the Solwara project by the Canadian Nautilus firm in 2005.  Drilling area is the Bismarck Sea near Papua New Guinea.  The project takes place at approximately 1550 m of depth and aims to unearth between 1.2 to 1.6 tons of minerals (Solwara, 2019).  Another mining license was given to Saudi Arabia – Canada consortium for 30 years.  The project, named Atlantis II, takes place at the Red Sea between, Saudi Arabia and Sudan.

The high hydrocarbon (oil and gas) potential of the depths of Eastern Mediterranean, studies in the region and Turkey’s responsibilities have been explained in detail by Demirel, 2013.  Mud volcanoes (MVs) useful for sediment-gas separation are found frequently in the region (Lykousis et al., 2009).  We have only a few studies on our mineral deposits despite that.  This subject, however, has been raised in the official gazette number 14949, on 18 July 1974, with the provision of petroleum exploration license in the Aegean Sea and the Mediterranean Sea, to Turkey Oils Anonymous Partnership.  Taking these global and Eastern Mediterranean development into account, we need to begin comprehensive studies as soon as possible, and limit this work to our own territorial waters.

Sadly, desired scientific progress on Turkey’s deep sea regions hasn’t been made.  The first scientific meeting concerning deep seas was organized by TUDAV on 19 June 2017 at the Istanbul University, Department of Aquatic Sciences, Gökçeada Marine Research Unit.  30 scientists from 17 institutions, working on relevant skills, gathered together and made presentations. These works have been published by TUDAV in the least in the ‘Proceedings of 1st Turkish Deep Sea Ecosystem Workshop’.  On the other hand, deep sea and research strategy document has been published in the official gazette number 29137 (Official Gazette, 2014) and emphasized necessary steps to be taken for deep seas, giving us hope for the future of this field.  Scientific production is necessary for political backup. Turkey has the means and the responsibility to conduct deep sea research with its current ships, research background and scientific personnel.



Anonymous, 2015. “Trieste Bathyscaphe”. Machine-History.Com. from Time article 12 October 1953. Archived from the original on 6 September 2015. Retrieved 27 April 2015.

Anonymous, 2011.

Amos, J. (2019). “US adventurer reaches deepest points in all oceans”. Retrieved September 10, 2019.

Atkinson, K. (2008). “Size matters on ‘squid row’ (+photos, video)”. The New Zealand Herald

Benson, Keith R. & Rehbock, Phillip F., eds. (2002) [1993]. Oceanographic History: The Pacific and Beyond. University of Washington Press. p. 388.

Birney, KA., Griffin, J., Gwiazda, J., Kefaver, J., Nagai, T., Varchol, D. 2006. Potential Deep-Sea Mining of Seafloor Massive Sulfides: A Case Study in Papua New Guinea,

Bourton, J. (2010). “BBC – Earth News – Giant deep sea jellyfish filmed in Gulf of Mexico”. BBC News. Retrieved 2010-07-08.

Demirel, İ.H. 2013. Doğu Akdeniz Havzası Hidrokarbon (Petrol-Gaz) Potansiyeli. In: Başeren S. H. Doğu Akdeniz’de Hukuk ve Siyaset. Ankara Siyasal Bilgiler Fakültesi. Yayın no:608 Syf: 1-78

Demirsoy S. (1972), “Deniz Hukukundaki Yeni Gelişmeler ve Madencilikle İlişkisi”, Maden, Tetkik ve Arama Enstitüsü Dergisi, 79, 76-99,

Froese, Rainer, and Daniel Pauly, eds. (2007). “Regalecidae” in FishBase. March 2

Görür, N. 2000. Marmara Denizi’nde Argus Denizaltısıyla Yapılan Çalışmalar. Türkiye Is Bankasi Kültür Yayinlari, 2000 – 136 sayfa

Luther, G.W. III, Gartman, A., Yücel, M., Madison, A.S., Moore, T.S., Nees, H.A., Nuzzio, D.B., Sen, A., Lutz, R.A., Shank, T.M., Fisher, C.R. (2012) Chemistry,7 temperature, and faunal distributions at diffuse-flow hydrothermal vents: Comparison of two geologically distinct ridge systems. Oceanography, 25(1):234–245.

Karapınar, N. 2015. Derin Deniz Madenciliği. MTA Genel Müdürlüğü. Madencilik Türkiye. Syf: 72-82

Lykousis, V., Alexandri, S., Woodside, J., De Lange, G., Dählmann, A., Perissoratis, C., Rousakis, G. (2009). Mud volcanoes and gas hydrates in the Anaximander mountains (Eastern Mediterranean Sea). Marine and Petroleum Geology, 26(6), 854-872.

McClain, Craig R.; Balk, Meghan A.; Benfield, Mark C.; Branch, Trevor A.; Chen, Catherine; Cosgrove, James; Dove, Alistair D.M.; Gaskins, Lindsay C.; Helm, Rebecca R. (2015-01-13). “Sizing ocean giants: patterns of intraspecific size variation in marine megafauna”. PeerJ. 3

MSIP, 2020. Marine Species Identification Portal : Stygiomedusa gigantea”. 007 version

Öztürk, B., Dede, A., Sümer, A. 2017. Marmara Denizi’nde Argus Denizaltısıyla Yapılan Çalışmalar. In: Gönülal O., Öztürk B., Başusta N., (Ed.) 2017. I. Türkiye Derin Deniz Ekosistemi Çalıştayı Bildiriler Kitabı, Türk Deniz Araştırmaları Vakfı, İstanbul, Türkiye, TÜDAV Yayın no: 45

Solwara, 2019.

Than, K. 2012. “James Cameron Completes Record-Breaking Mariana Trench Dive”. National Geographic Society. Retrieved 25 March 2012.

Thebault, R. 2019. “He went where no human had gone before. Our trash had already beaten him there”. The Washington Post. Retrieved May 23, 2019.

Triton, 2019.

Tüzün, S. 2017. Derinleri Keşfetmek: E/V Nautılus Teknoloji, İşleyiş Ve Türkiye Denizlerinde Araştırmalar. In: Gönülal O., Öztürk B., Başusta N., (Ed.) 2017. I. Türkiye Derin Deniz Ekosistemi Çalıştayı Bildiriler Kitabı, Türk Deniz Araştırmaları Vakfı, İstanbul, Türkiye, TÜDAV Yayın no: 45

Yücel, M., Yapan, B. Ç., Görünmez, S., Luther, G. W. 2017. Alvin Denizaltısı ile Derin Deniz Hidrotermal Ekosistemleri Araştırmaları. In: Gönülal O., Öztürk B., Başusta N., (Ed.) 2017. I. Türkiye Derin Deniz Ekosistemi Çalıştayı Bildiriler Kitabı, Türk Deniz Araştırmaları Vakfı, İstanbul, Türkiye, TÜDAV Yayın no: 45