The bluffs overlooking Horoirangi Marine Reserve are more than a dramatic landscape, they are also the source of rocks for the rugged boulder reefs below. The reefs extend offshore up to 400 m and to a depth of around 20 m.
The boulders on the upper shore, regularly moved by the waves, are mostly devoid of life. Lower down the reefs are much more stable, forming a matrix of interlocking boulders interspersed with occasional patches of bedrock.
The reefs support a typical array of animals. Shellfish, anemones, sponges and sea squirts cling to the rocks; snails, starfish and crustaceans move secretively amongst the boulders, and various fish patrol above.
Ambush starfish are unusually common in Horoirangi, and their colours provide a sharp contrast to the subdued hues of the rocks and most of the other reef species.
A vividly coloured ambush starfish waits patiently for its prey
Brown seaweeds form a dense forest between Mackay Bluff and the dramatic rocks at Ataata Point.
Hermit crabs are common on the offshore sediments
Significant increases in the abundance and size of marine species in Tasman Bay marine reserves confirm their conservation benefits. Research shows that 20 years after the Tonga Island Marine Reserve was created, there are more than seven times as many crayfish and 40 times as many blue cod over 30 centimetres.
Horoirangi Marine Reserve brochure (PDF, 372K)