Marine algae number 165 species, with red algae making up over half of the total species listed. The seaweeds found around the Kermadecs are characteristically of small size, with most plants 15cm in height. Several algal genera show warm water affinities.
The marine communities are important for their special populations (including the endemic giant limpet (Patella kermadecensis), and the spotted black groper (Epinephalus daemelii), interesting absences (many of the tropical herbivorous fish, most of the larger brown algae), populations of species at their geographic limits (corals and crown of thorn starfish). Marine reptiles which only straggle to the mainland, such as seasnakes and green turtles, are present around the islands.
With a total marine area of 4,300,000 square kilometres, New Zealand has one of the world’s largest Exclusive Economic Zones (EEZs) – 15 times the New Zealand land mass. The Kermadec region represents around 15% of this marine environment.
The seabed around the islands is extremely deep. Almost all of it descends to over 1,000 metres and more than a third of it to over 5,000 metres. And the Kermadec – Tonga trench plunges more than 10 kilometres beneath the ocean’s surface – about five times deeper than the Grand Canyon.
The Kermadec Arc is the longest under water volcanic arc on the planet. More than 50 submarine volcanoes extend along the 2,500 km collision zone between the Pacific and Australian tectonic plates. The largest volcanic islands of the Kermadec region - Raoul, Macauley, Curtis, Cheeseman and L’Esperance - are the only uninhabited subtropical island group in the Southern Hemisphere
It is estimated as many as 35 species of dolphin and whale - including the blue whale, fin and sei whales - migrate through the Kermadec region on their seasonal journeys between the tropics and cooler waters around New Zealand. A survey in 2009 recorded more than 100 humpback whales off Raoul Island in a single day.
Of about 350 species of seabirds worldwide, 39 are found in the Kermadec region, ranging from tiny storm petrels to large wandering albatrosses. Some are found only in the this region, while others – many from mainland New Zealand and our subantarctic islands – forage for food or migrate through. Up to 6 million seabirds breed on the Kermadec Islands each year.
Three of the world’s seven sea turtle species are found in the Kermadecs: hawksbill, leatherback and green. These species regularly wander through the region en route south from their mainly tropical habitats. All are considered endangered or critically endangered.
Of the 1339 species of fish known in the New Zealand EEZ, 431 of them (32%) occur along the Kermadec Ridge and Trench. But large areas of the Kermadecs– particularly those below depths of 600 metres – are virtually unexplored and it is highly likely that future surveys will reveal new and rare species.
The Census of Marine Life (the gold standard for measuring ocean biodiversity) published in 2010, estimated there were more than 230,000 species in our oceans. But the 10-year global study by 360 scientists warned of mass extinctions.
The Kermadec region is unusual for its mix of tropical and temperate species of crustaceans (crayfish, crabs, prawns and shrimps). Altogether, 88 species of crustacean are known here, of which 17 are known only in the Kermadecs. Some are new to science and some are specialised for Kermadec habitats – for example, two species of ‘vent crabs’ have adapted to survive one of the harshest environments imaginable, including searing temperatures, high acidity and toxic chemicals.
The Kermadecs have a unique population of tiny sea anemone-like animals known as bryozoans. Of 256 species identified so far, at least 38 are endemic and many are new to science. Some are ‘living fossils’, present in the oceans since the time of the dinosaurs tens of millions of years ago.