The year was 1983. Star Wars: Return of the Jedi had just hit theaters, The Police’s “Every Breath You Take” topped the charts, and Amos Barkai was a new graduate student at the University of Cape Town in South Africa. He’d recently gotten his bachelor’s from Tel Aviv University, and was excited to start his graduate work under George Branch. Little did he know he was about to discover an ecological phenomenon that would earn him a prestigious paper in Science.
Branch had been investigating the effects of bird guano runoff from islands on life in the intertidal—the zone between high tide and low tide—and he was interested in seeing whether the effects extended into deeper waters. Since Barkai was an experienced diver (he’d worked as a professional diver for the Israeli Navy and as a commercial diver after that), Branch sent him 100 kilometers or so away to Saldanha Bay, a protected coastal kelp ecosystem. “I packed him off to one of the islands we’d been working on, callled Marcus Island,” Branch explained. “I told him, You’re fully qualified as a diver, so I want you to go and do some exploratory dives. Take a look around there, and see if you can see anything interesting.”
It just so happened the area was experiencing a once-in-a-lifetime storm with waves over 18 meters high. “I didn’t know I was exposing him to hell on Earth, and he came back completely shell-shocked,” said Branch. “I think he wondered what kind of supervisor he was getting involved with.” But once things calmed down a bit, Barkai did get in the water, and looked for evidence that the birds nesting on Marcus and other nearby islands were affecting the communities near shore. He didn’t find any—but he did notice something strange.
Near to Marcus was Malgas Island—so named for the gannets, a kind of seabird, which nest there (Malgas is old Dutch for “mad geese”)—which looks entirely similar to Marcus Island from the surface. The seabed, however, told Barkai a very different story. Although they’re just a few kilometers apart, the species he saw “were strikingly different,” he said. West Coast Rock Lobsters (Jasus lalandii) or ‘kreef’ as they are known locally were everywhere around Malgas. Several hundred of them per square meter crowded into crevices and under ledges—there was “basically nothing else.” To find anything that wasn’t a lobster, he had to peek under the holdfasts connecting the kelp to the substrate. There, he found mussels and a few Burnupena papyracea—small whelks (a kind of marine snail).
Around Marcus Island, though, “the bottom was covered with anything but lobster,” Barkai said. A dense mat of mussels lined the benthos, and it was decorated with whelks, sea urchins, and sea cucumbers galore, but nary a lobster to be seen.
