AUTUMN. Frail morning sunlight shimmers on Auckland’s Hauraki Gulf. I clamber across black scoria rocks with my guide, emeritus Professor John Morton, now in his late seventies. We’re on Milford Reef, fossicking while the tide is out. Regarded by many as New Zealand’s greatest marine biologist, Morton squats over a shell-encrusted ridge and runs his fingers lovingly across the backs of its inhabitants. His voice, low and gravelly, mixes with the waves: “Elminius modestus, Saccostrea glomerata... Lepsiella scobina... Nerita atramentosa...”—otherwise known as barnacle, rock oyster, oyster borer and common black nerita.

Suddenly a shadow falls across us. “Is that Professor Morton?”

A middle-aged man with bare feet is standing on the rocks above us. He’s delighted to have stumbled upon Morton. Could he ask the professor a question?

“Certainly,” says Morton, smiling as he straightens up.

“I want to know,” says the man, “why so many horse mussels are being washed up on the beach these days.”

A gleam of excitement comes into Morton’s eyes. “That’s a very interesting question.”

We crouch on the rocks together and Morton starts to tell us about the changing ecology of the waters around Auckland—how increasing silt levels are forcing plants and animals to relocate. Shellfish once found in the upper reaches of the Waitemata are finding new homes on the edge of the Hauraki Gulf. An influx of horse mussels seems to be part of the pattern.

John Morton has been coming to Milford Beach for enough decades to know a thing or two about the place. His family lived in Morrinsville but used to visit Milford for summer holidays. Here, under the watchful eye of his solicitor father, Morton junior began a study of the seashore and its natural history that would eventually take him from one end of the Pacific to the other. Something else happened in those years: a profound allegiance was forged with the Christian faith. In Morton’s words, it became “the invisible thread that runs through it all”—his scientific, academic and public lives.

After becoming dux of Morrinsville High—excelling not just in science but also in history, classics and English—Morton entered the somewhat primitive precincts of the zoology department at Auckland University in 1942. The head of zoology, Professor W.R. McGregor—or Barney McGregor, as he was usually known—was an unusual figure: charismatic and forceful in the lecture theatre, but poorly qualified to preside over a scientific discipline that was on the threshold of rapid change. Essentially insecure, he ran the department with a rod of iron, suppressing dissenters and, by and large, discouraging scientific debate.

McGregor quickly recognised Morton’s exceptional talents, making him his demonstrator in his second year and teaching him the old micro-anatomical skills of wax-section cutting and staining. But McGregor’s authoritarianism brought out a rebellious streak in his gifted student and the relationship soured.