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Many people unfamiliar with the Southern Ocean regard this ice-bound region as still largely unexplored biologically. This is far from the truth, for the study of the diversity and distribution of organisms in the Southern Ocean has a long and distinguished history. James Cook got close to the Antarctic continent in 1774 aboard HMS Resolution, although he never saw it. His reports of the abundant wildlife led to an explosion of commercial sealing activity, but sadly none of this contributed much to a wider understanding of Southern Ocean biology as the knowledge gained was of powerful commercial interest and largely remained within the community of fisherman to whom it was valuable economically.

Some Antarctic marine species were, however, described as early as the 19th century, reflecting how even
the earliest voyages of exploration contributed something to science. The initial exploration of Antarctica
was dominated by political, geographical and economic considerations, but even so many of the expeditions undertook biological collections and observations. These were typically fairly limited in scope and often undertaken by participants whose primary role was elsewhere. This early work was dominated by collection of shallow-water benthos and fish, although Bellingshausen did undertake some plankton tows.

Although these early collections were valuable, we can trace the dedicated scientific investigation of the
Southern Ocean fauna and flora to the seminal voyages of HMS Challenger (1872-1876), which penetrated
to the Antarctic Circle off Queen Maud Land in the Southern Indian Ocean whilst sailing eastwards in 1874.
The concept of a purely scientific voyage was novel at that time and although the equipment and approach
were perhaps somewhat conservative, this voyage revolutionised our understanding of the biology and chemistry of the oceans. Working up the material took a great many years, but in the end some fifty volumes of scientific findings were published, all beautifully illustrated, and these remain an important scientific resource to this day.

During the Heroic Era of Antarctic exploration, many national expeditions included biologists in their complement and these added incrementally to our knowledge. For some expeditions science was a minor component, whereas for others it was integral to the enterprise as a whole. The next significant contribution to our knowledge of Southern Ocean marine diversity, however, came from the Discovery Investigations. Field-work was initiated in 1925, based at South Georgia, and the work was intended to provide an understanding of the biology of the great whales on which the whaling industry depended. In doing so, these extensive voyages of biological oceanography covered the entire Southern Ocean and provided the single greatestadvance in our understanding of the system since the voyage of HMS Challenger.

The legacy of this important early work can be seen in the sharp increase in the rate of description of new
marine species from the Southern Ocean during the early half of the 20th century. At this time ecology as a discipline was developing rapidly, and the attention of many biologists was moving away from the documentation of new species to understanding how species interacted with each other and with their environment. Although the description of new taxa continued to be important in museums, university researchers were busy exploring this new field of ecology and the rate of description of new Antarctic taxa slowed markedly.

The later decades of the 20th century were a time when Antarctic science started to flourish and many new young researchers starting their careers in Antarctic research at this time rapidly became aware of the importance of this early work. When I started my first Antarctic work in 1970, I decided to explore aspects of the biology and physiology of the caridean decapod Chorismus antarcticus in the shallow waters of South Georgia. In those days there was no easy way to identify Antarctic marine invertebrates, and so to be certain I was working on the animal I thought I was, I had to find a copy of the original description by Georg Johann Pfeffer, from specimens collected by the German South Georgia expedition which was based at Moltke Harbour for the first International Polar Year in 1882/83.

In the late 20th century many funding agencies became less interested in funding primary taxonomy, but the documentation of Antarctic marine diversity remained important for many national Antarctic programmes. The next important phase in the study of Southern Ocean diversity and biogeography was the support of Antarctic marine biology by the Scientific Committee on Antarctic Research (SCAR), and in particular the EASIZ (Ecology of the Antarctic Sea Ice Zone) programme which ran for ten years from 1994. Whilst this international programme was focussed primarily on ecology, it also stimulated a considerable volume of primary taxonomic work and prompted the first comprehensive assessments of marine diversity for all of Antarctica. Whilst these assessments were valuable in themselves, they were also important in directing attention at gaps in our knowledge. In particular they identified how little was known of the fauna of the continental slope and the deep-sea around Antarctica. Other important features of the EASIZ programme were the emphasis placed on understanding the relationship between marine organisms and the oceanographic environment within which they lived, and also the evolutionary context in respect of the climatic and tectonic history of the Southern Ocean.

After the EASIZ programme had drawn to a close, the ANDEEP (Antarctic Deep-Sea Biodiversity) programme undertook a series of cruises directed specifically at improving our knowledge of the Antarctic
deep-sea fauna. At about this time another significant development was the initiation, under the auspices
of SCAR and hosted by Royal Belgian Institute of Natural Sciences, of an interactive database for Antarctic
marine diversity, MarBIN (Marine Biodiversity Information Network). As science becomes ever more reliant on information being available on-line, SCAR-MarBIN has been instrumental in improving the quality of marine diversity data for Antarctica, and in disseminating this information to those who need it. The Southern Ocean is now part of the global information network, and no longer an isolated region of the world.

These important developments meant that when the Census of Antarctic Marine Life (CAML) was initiated,
and fieldwork undertaken in conjunction with the second International Polar Year (2007/08), the stage was
set for a major step forward in our knowledge and understanding of Southern Ocean marine diversity. This
volume shows the extent to which this opportunity has been taken and the potential realised. CAML has
delivered the single largest step in our knowledge of Antarctic marine diversity and biogeography since the first half of the 20th century. The Biogeographic Atlas has sections devoted to every major taxonomic group, with detailed maps of distribution, as well as chapters documenting the environmental background and evolutionary history, and synthetic analyses. This is a magnificent achievement and testament to the vision of those who planned and developed the programme. It will undoubtedly remain an important resource for
many years to come.

Andrew Clarke
Emeritus fellow
British Antarctic Survey, Cambridge

April 30, 2020