At the University of Birmingham he initially studied physics, obtaining his first degree in 1963, but moved to marine geology for his PhD, which was awarded in 1968.

[10][11] This led to a series of papers on plankton distribution,[12][13] as well as the development of an underway fluorimeter that could be used to measure phytoplankton chlorophyll on hydrographic surveys.

[14] During the 1980s, Fasham began to direct his research toward quantitative treatments of the flows of energy and material through ocean food webs.

The study is one of the most highly cited papers in the field,[4] and won the American Society of Limnology and Oceanography John Martin Award in recognition of this in 2010.

[19] In later work, Fasham continued to advance ecosystem models by considering aspects such as parameter optimisation,[20] the balance of autotrophic and heterotrophic plankton,[21] diel vertical migration,[22] and the role of the micronutrient iron in oceanic primary production.