The Expedition
This National Geographic Explorer and research scientist leads the expedition in search of a pristine, shark-filled ecosystem.
Enric Sala
This is the first island the team visits — about 2.5 miles long and less than a mile wide, and the top of an ancient volcano.
Flint Island
According to the traditional ecological model, this shape describes the expected relationship between predators and prey — many small prey supporting few top predators.
Pyramid
This colorful, symbiotic organism lives inside coral polyps, using sunlight to create energy and giving coral its color.
Algae
In the 1870s, this crop was planted by the tens of thousands on Flint Island to produce coconut oil, stripping away the native vegetation.
Coconut palms (palm trees)
This is the name of the floating laboratory ship the research team boards in the port of Papeete, Tahiti.
Hanse Explorer
Enric calls this tiny, never-inhabited island "the most pristine" because its native forest was never stripped for coconut plantations.
Vostok Island
This is the term for the total weight of a particular species or group of organisms living in an ecosystem.
Biomass
This is what happens to coral's color when it becomes stressed — it turns pale or white.
Bleaching
This nutrient-rich substance — seabird droppings mined for fertilizer on several of the islands in the 1800s and early 1900s — is sometimes called "black gold."
Guano
This remote island chain, belonging to the country of Kiribati, is the expedition's ultimate destination.
Southern Line Islands
This dry, sparsely vegetated island receives little rainfall and turned out to have the second-largest fish biomass of any coral reef ever studied.
Starbuck Island
At Starbuck and other pristine reefs, the team discovers the biomass pyramid is actually shaped like this, with predators outweighing their prey.
Upside down (inverted)
This species of coral-eating starfish is described as a "voracious coral predator."
Crown-of-thorns starfish
This is the main reason Vostok Island's ecosystem remained so untouched compared to the other islands in the chain.
Small size
This land-based scientist and National Geographic Explorer in Residence, previously known for his conservation work in Gabon, Africa, surveys the islands' ecology above water.
Mike Fay
This triangular island, the largest visited on the expedition, was the site of three low-altitude nuclear bomb tests in 1958.
Malden Island
Enric uses sharks as an indicator species because their size and number reveal this about a reef ecosystem.
Health
At Malden, these algae-grazing fish were seen helping create sand while also keeping algae in check on the reef.
Parrotfish
Even on remote, uninhabited Millennium Atoll, Enric finds this washed-up evidence of human activity threatening the reef's sharks.
Fishing hooks
This is the approximate total distance, in miles, the team covers on its roughly 30-day journey across the Southern Line Islands.
Nearly 2,000 miles
This final stop is a lagoon ringed by small islands called motus, home to swarms of blacktip reef sharks and described as Enric's "Eden."
Millennium Atoll
Even at remote, protected-seeming Flint Island, the sharks were small and few — a clue that this human activity had reached the area despite its remoteness.
Fishing
The microbiologists on the team study these microscopic organisms, discovering that certain algae on damaged reefs release food that causes them to grow out of control and kill coral.
Microbes/Bacteria
Enric argues that studying these pristine, unspoiled reefs gives scientists this kind of reference point for measuring human impact on damaged reefs elsewhere.
Baseline