G. Evelyn Hutchinson

At the age of twenty-two, on graduating from Cambridge, Hutchinson traveled to Italy on a Rockefeller Higher Education Fellowship to work at the Stazione Zoologica. He was interested in doing research on the branchial gland of the octopus. He wanted to establish endocrine function in higher invertebrates. He thought that the branchial gland was the endocrine gland in the octopus, but an octopus shortage put an end to his research. He returned to Italy many times for Italian art, folklore, and to study his Italian ancestry.[17]

In 1926 he applied for a lectureship at the University of Witwatersrand in Johannesburg. He lectured for two years before he was fired, but he continued to study the South African water bugs. When he began his research there were fourteen known species and when he concluded his research there were nearly forty. It was here that Hutchinson discovered limnology, or the study of fresh waters. Along with Grace Pickford, he studied the chemistry and biology of the coastal lakes. He was greatly interested in limnology due to it combining of all his interests such as natural history, aquatic invertebrates, and chemistry. He was drawn to the differences in the chemistry, flora, and fauna in the different water sources.[18] While in South Africa in the late 1920s he frequently visited the southeastern portion of the country, in particular conducting biology and chemistry research in Morgans Bay and St Lucia, he also spent a lot of time around the Sani Pass and the Drakensberg Mountains as well as the area around Royal Natal National Park. He became somewhat of a minor celebrity in Natal during this time.[19]

In 1932 Hutchinson joined the Yale North India Expedition. He wanted to be the first to make ecological observations of a high-altitude lake, and to compare these with lower-altitude lakes. The work yielded insights into biogeography and new data on high elevation limnology. Most lakes had no fish, and crustaceans were the top predators. In letters to his wife, he described the different water chemistry from the Indian lakes to the South African lakes.[20] He collected hundreds of specimens for analysis by specialists. This expedition provided the material for his first book, The Clear Mirror, in which he described the colors, organisms, ecology, and the people of the Ladakh.[21]

Most of Hutchinson's contributions to American limnology came from research at Linsley Pond in Connecticut. Studies were done on small lakes, such as chemical stratification, oxygen deficits, productivity, and the ecological significance of the oxidation-reduction potential of lake waters. His four volume Treatise on Limnology became a standard for limnology students. Hutchinson expanded the field of limnology, especially in its ecological and biogeochemical aspects. He advocated the use of statistical and mathematical methods in limnology.[22] His postdoctoral associate Raymond Lindeman furthered Hutchinson's model of the trophic dynamic concept. Together they looked at energy flows through the lake in the trophic levels of ecosystems.[23] They followed the energy using Hutchinson's notation system in which each organism was given an integer to mark how many organisms the energy had to go through in order to reach it, this was designated as its trophic level. It then became possible to measure the efficiency of a given system, or the energy losses between ascending trophic levels.[3]

Hutchinson is also recognized as being the first to use radioisotopes as tracers in field experiments. In doing so he along with his graduate student Vaughan Bowen, are credited with creating Radiation Ecology, a brand new major field of ecology. He again turned to Linsley Pond, he released twenty-four portions in two lines and dispersed it uniformly across the water, a week later they collected water across different depths in the lake. They then evaporated and measured the radioactivity, what they found they deemed to be statistically significant. The rest was found to have been taken up by the aquatic plants in the shallow water area of the lake.[24]

Hutchinson and his graduate students intellectualized American ecology by "forcing its practitioners to confront all of the processes that maintain to change ecological systems, whether these processes were biological, physical or geological".[3] He built on Charles Elton's idea of an ecological niche. He defined it as "a highly abstract multi-dimensional hyperspace in which the organism's needs and properties were defined as dimensions."[3] Hutchinson created the idea of "Circular Causal Systems", the tight link between biological and physical processes, and that the activity of organisms balanced the effects on the cycles of chemicals through organisms. He said that the changes in biological productivity were related to the changes of available nutrients. He stated that the condition in which organisms existed were systems of feedback loops. In his systems view, there were both living and non-living feedback systems which followed the same mechanical principles. This led to the development of systems ecology by his student H.T. Odum.[23]