The impact of Scripps´ NAGA Expedition, on Thorson´s ´parallel´ animal community hypothesis

Gunnar Thorson, a direct disciple of C.G. Joh. Petersen, the father of quantitative sub-littoral ecology, in his seminal work of 1957, had come to the conclusion that - "the same types of bottom are everywhere inhabited by series of \´parallel\´ animal communities, in which different species, of the same genera, replace one another as "characterizing species". Despite this, however, Thorson himself was not content with the, at the time, scanty data from tropical regions. This fact leads him to stimulate further sampling taking advantage of the NAGA Expedition to the South China Sea which was originally to be directed by another Dane, Dr. Anton Bruun onboard Scripps R/V STRANGER. This paper describes the author\´s work and the impact of its preliminary findings from the intensive quantitative benthic survey that developed from the NAGA Expedition effort in the sub-littoral environments of and around the Bay of Nha-Trang, Vietnam, in early 1960. The benthic sampling was performed according to the techniques currently used at the time as applied to the soft bottom benthos, both utilizing the local facilities provided by the Institute Oceanographie de Nha Trang, and the sporadic visits of the SIO vessel. In the main, the Vietnamese survey contributed to cast doubts on the validity of Thorson\´s \´parallel\´ animal communities hypothesis, further stimulating him to pursue the investigation of tropical benthic settings. Thus, around the beginning of the 1960s a Danish expedition was organized and carried out off the west coast of Thailand under his direction in early 1965. This new but more adequate personal experience with the tropical infauna finally convinced Thorson that the tropical sub-littoral benthic animal communities were of a totally different nature as those known from temperate and cold sub-littoral regions and that his \´parallel\´ animal communities hypothesis did not apply everywhere.