In many ways a typical of temperate New Zealand marine environment, the added factor of a constant current streaming South from the tropics adds a truly unique flavour. The warm waters support a myriad of tropical visitors who have found a niche amongst the kelp forests, rocky reefs and more usual local inhabitants.
A rich pantry
The Poor Knights lie close to the continental shelf and its upwelling of nutrient-rich waters. This lush food source flows close to the Islands and provides a continuous supply of food for filter feeders. Archways and vertical walls are thick with an astonishing array of encrusting life that support an incredible bio-mass of fish and other invertebrates.
The shady recesses of archways and caves offer comfort to species usually only found at depth, and act as safe havens for juveniles. In the protected back recesses of Rikoriko Cave a sponge usually found only at 200 metres thrives just 10 metres below the surface.
During summer vast numbers of stingray gather in archways to mate, the volcanic structures providing protection by confusing the radar of predatory orca.
Tropical visitors - some larval, some larger - arrive in the summer months, brought down on the East Auckland current. Originating from tropical waters off the Australian east coast, the current passes Lord Howe and Norfolk Islands before turning Southeast to run parallel to Northland’s East coast.
The Islands must seem like an oasis; many tropical visitors settle on the reef permanently. The Island are too cool for some visitors; the manta, humpbacks and turtles only pass through.
Tropical settlers include Lord Howe coral fish, spotted black grouper, yellow-banded perch and banded coral shrimp. A number of tropical wrasses have found their way down and settled; the rainbow fish, elegant wrasse and the blue-headed wrasse. Not all survive the winter temperatures, but individuals manage to find a niche and remain happily for years.
Although too cool in these waters for delicate coral reefs, the seaweed and kelp flourish. There are kelp forests, gardens and carpets of red and green seaweed. The dense forests stalks are home to an abundant community of animals.