Professor Alan Southward was one of the leading marine biologists of the past 50 years. He conducted seminal research in marine ecology, studying the impact on organisms of environmental changes such as climate and pollution, and how they are adapted to life in the deep sea. In the 1970s, when climate change research was still in its infancy, he demonstrated important links between climate and biological changes in the sea, work that laid the foundations for all subsequent studies worldwide.

Alan James Southward was born in Liverpool in 1928. He attended the Liverpool Collegiate School — where his studies were interrupted by meningitis, which left him profoundly deaf — and the University of Liverpool where he took a first-class degree and a doctorate. He began his scientific career in 1953 at the Laboratory of the Marine Biological Association of the UK (MBA) in Plymouth. His doctoral studies concerned the ecology of intertidal animals such as limpets and barnacles, and with his wife and lifelong science collaborator, Dr Eve Southward, this work was continued at Plymouth by establishing long-term monitoring stations.

These were to prove invaluable when in 1967, the Torrey Canyon oil spill contaminated much of the shores of Cornwall. He was one of the small team of scientists who studied its aftermath. His monitoring of animals and plants on rocky shores, serendipitously sampled before, and then after the spill, showed that applying toxic chemicals to disperse the oil slick was more detrimental to wildlife in the long term than the oil itself. Another first was that his work also quantified the time periods needed for ecosystem recovery. His innovative and patient research was hugely influential at the time and he was largely responsible for governments and agencies abandoning the widespread use of toxic chemicals to tackle oil slicks.

Southward's research at Plymouth came under the guidance of Sir Frederick Russell, and his investigations moved offshore when he was invited to co-ordinate the laboratory's plankton and larval fish time series. The work that followed became a classic: the discovery of how marine species respond to climate change. In the western Channel it was noticed that cold-water herrings and plankton, once common in the 1920s, had declined and were replaced by warm-water pilchards and plankton in the 1940s and 1950s. During the 1960s and 1970s boreal fish species once again predominated. Relating these to fluctuations in long-term sea temperature records and other physical data, Southward realised that the shifts in animal distributions and changes in abundance were closely linked with climate oscillations. He then set about documenting these in detail and proposing several biological mechanisms, leading the way for all subsequent research on the topic.

His other important contribution was on the evolution of symbiosis between chemoautotrophic bacteria and marine invertebrates, such as the worms and molluscs. The strange new species he and his wife discovered were found to derive nutrition from internal bacterial flora, and included deep-water worms and bivalve molluscs from slope habitats. Such discoveries were made during the course of long research cruises, sometimes in mountainous seas — a fortunate consequence of Southward's deafness was that it gave him complete immunity to seasickness.

It is a testament to Southward's strength of character, balanced by a mischievous sense of humour, that despite prejudice against his deafness early in his career, he went on to achieve great heights of scientific discovery.

He produced more than 200 publications including journal articles — 21 articles in Nature alone, an unusually large number for an ecologist — book chapters and books, most notably Life on the Sea-shore (1965); Barnacle Biology (1987) and British Barnacles, which he completed shortly before his death and which is to be published in 2008. He was series editor of Advances in Marine Biology, the premier marine biology review journal, for more than 20 years. He was appointed honorary Professor of Marine Biology, Port Erin Marine Laboratory, University of Liverpool, in 1989 and Adjunct Professor of Marine Biology, University of Victoria, British Columbia, in 1990.

The impact of Southward's research is broad and long-lasting. Reference to his early work on climate impacts on animals continues to increase now that worldwide concerns about global warming have galvanised the international research effort and funding. In this sense he was a scientist very much ahead of his time.

Southward is survived by his wife, Eve.

Professor Alan J. Southward, marine biologist, was born on April 17, 1928. He died of a heart attack on October 27, 2007, aged 79