Deep-sea grenadier fish, Nezumia sp. (© NOCS 2006) Deep-sea grenadier fish, Nezumia sp. (© NOCS 2006)
Deep-sea grenadier fish, Nezumia sp. (© NOCS 2006)
Deep-sea grenadier fish, Nezumia sp. (© NOCS 2006)
Deep-sea grenadier fish, Nezumia sp. (© NOCS 2006) Deep-sea grenadier fish, Nezumia sp. (© NOCS 2006) Deep-sea grenadier fish, Nezumia sp. (© NOC 2006)
Deep-sea grenadier fish, Nezumia sp. (© NOCS 2006)

Early deep-sea exploration

Early development of deep-sea biology took place in and around UK waters. Many of the great ocean-going expeditions set sail from our own shores and many early discoveries and new theories were made by the pioneers of deep-sea research; Edward Forbes and Charles Wyville Thomson.

Edward Forbes - a pioneer of deep-sea research

The story begins with the voyage of the HMS Beacon (1841-42) and one Edward Forbes, later a Professor of Natural History at Edinburgh University. Among a great many other contributions to marine biology, Forbes carried out dredging studies in the Aegean Sea from the Beacon. From these observations Forbes developed the “Azoic Theory”, stated simply a depth limit to the distribution of life in the sea. Unfortunately, Forbes’ azoic theory has left him with a somewhat tainted reputation in the preamble to works on deep-sea biology; however in Forbes’ own words “…it is in the exploration of this vast deep-sea region that the finest field of submarine discoveries yet remains.”

Although it is debatable whether Forbes believed the “Azoic Theory” to be literally true, and despite evidence to the contrary, this view of the deep sea as a lifeless zone was prevalent until the late 1860's.

Charles Wyville Thomson - a pioneer of deep-sea research

Around this time the Norwegian scientist, Michael Sars, collected marine animals from depths near to 1000m by means of a dredger, and the deep-sea desert theory began to seem more and more unlikely. In 1868 Sars was able to produce a list of 427 animal species caught alongside the Norwegian coast at depths of 450 fathoms (about 820m). Sars created quite a stir with his description of the “sea lily” Rhizocrinus lofotensis which his son, G.O. Sars, had found in 1864 at a depth of about 550m in Lofoten. This strange echinoderm had a likeness to species which up to this date were known only from fossil finds. Being interested in crinoids, and prompted by Sars’ dredging off the Norwegian coasts, Charles Wyville Thomson (one of Forbes' brighter young students) instigated the cruises of the HMS Lightning and HMS Porcupine to the deep-waters to the north and west of Scotland.

HMS Porcupine, a wooden two-masted brigantine rigged paddle gun-vessel, built in 1844

Thomson successfully petitioned the Royal Society and the Admiralty for the funds and the means to carry out deep-sea dredging studies around Scotland and Ireland “with a view to ascertain the existence and zoological relations of animals at great depths”. He was first given use of HMS Lightning (1868), “a cranky little vessel enough, one which had the somewhat doubtful title to respect of being perhaps the very oldest paddle-steamer in her Majesty’s navy. We had not good times in the ‘Lightning’. She kept out the water imperfectly … we were in considerable discomfort.” Despite the expedition being plagued by bad weather and the poor condition of the ship, a rich catch of animals were collected in hauls from depths of 90 to 1189m. This evidence proved the existence of abundant and varied life at much greater depths than had been sampled previously.

The cruises of HMS Porcupine (1-3 in 1869, 4 in 1870)

In light of the collections made during the HMS Lightning voyage, Thomson and Carpenter urged the Royal Society to recommend their research to the Admiralty once more. The Admiralty granted their wishes and HMS Porcupine was made available to them for further research in May 1869.

HMS Porcupine set sail in May 1869 on the first of four cruises, with objectives of dredging beyond those depths achieved by HMS Lightning and to investigate further the deep water temperature anomalies discovered in the Faroe-Shetland Channel during the Lightning cruise. Many successful dredges were achieved at a variety of depths and with further impressive evidence of life in the deep sea. The deepest ever dredge haul was achieved during the course of the second leg, with animals collected from 4289m. This was an amazing achievement and finally dispelled Forbes’ azoic theory.

Armed with the results from the Lightning and Porcupine, Thomson proceeded to the organisation of the extraordinarily ambitious three and a half year global voyage of HMS Challenger (1872-76). It is the Challenger expedition that is most usually cited in the introduction to any text on deep-sea biology, but without the success of the Porcupine and the Lightning cruises it is doubtful whether that expedition would have taken place.

Early findings

Lophohelia prolifera (Lophelia pertusa), adapted from Thomson, 1873.

The coral Lophelia pertusa was dredged from several locations during the Porcupine cruises. This species is the commonest reef-building cold-water coral. It has been frequently found in the North Atlantic Ocean. See for more information about cold-water corals.

Another biological habitat of potential conservation interest, and a major favourite of Charles Wyville Thomson himself, investigated by the Porcupine were “Holtenia grounds”: mass occurrences of the hexactinellid sponge Holtenia carpenteri (now Pheronema carpenteri).

Holtenia carpenteri (Pheronema carpenteri), adapted from Thomson, 1873.

Both Lophelia and Pheronema are inhabitants of “warm areas”. The Porcupine’s discovery of both warm and cold areas in the deep waters north and west of Scotland, and the influence that water temperature had on the distribution of species was a very significant advance in the science.

Today we are better able to understand and map these warm and cold areas, but their critical importance to the distribution and biodiversity of the UK deep-sea fauna remains as determined by Charles Wyville Thomson and others aboard the HMS Lightning and Porcupine cruises of 1868-70.

See our modern day exploration pages for information about research that has taken place in the deep waters around the UK since the days of these early pioneers.

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