Tube growth and calcification of two reef-building ecosystem engineers in southern New Zealand: Galeolaria hystrix and Spirobranchus cariniferus (Polychaeta: Serpulidae)

Two common New Zealand serpulid polychaetes, Galeolaria hystrix Mörch, 1863 and Spirobranchus cariniferus (Gray, 1843), occur solitarily and in dense serpulid aggregations, therefore locally increasing biodiversity and altering sediments. We present detailed data on tube growth and calcification of these reef-building ecosystem engineers. At Harington Point, Otago Harbour, New Zealand, subtidal G. hystrix individuals showed a mean tube growth of 4.0 cm y− 1 and calcification of 1.4 g y− 1 while individuals of S. cariniferus in the intertidal had a mean tube growth of 1.7 cm y− 1 and calcification of 0.3 g y− 1. With approximate longevities of 10-12 yrs for the two serpulids in Otago Harbour, G. hystrix may produce a tube up to 21 cm long and deposit 16.8 g of carbonate, while S. cariniferus could construct a tube of about 11 cm in length and deposit 3.6 g of carbonate during its lifetime. Assuming serpulid calcification rates are similar across the South Island of New Zealand, healthy G. hystrix patch reefs in Big Glory Bay, Stewart Island (4500-9700 worms m− 2) have the potential to deposit 6.3-13.6 kg CaCO3 m− 2 y− 1 while undamaged S. cariniferus aggregations at Sumner Beach, Banks Peninsula (45,000-55,000 worms m− 2) may produce 13.5-16.5 kg CaCO3 m− 2 y− 1. Typically sized (1 m high, 5 m in diameter), healthy G. hystrix patch reefs may deposit 220-476 kg CaCO3 y− 1, be 6-19 yrs old and involve 4-12 generations of worms. The oldest S. cariniferus aggregations could be 26 yrs old and involve about 15 generations of worms. Serpulid aggregations in New Zealand may locally deposit a ~ 1-2 cm thick sediment layer every year. With sedimentation and calcification rates similar to those of coral reefs, alongside locally enhanced biodiversity, aggregations in New Zealand can be seen as temperate carbonate reefs, the counterpart of tropical coral reefs. Protection of these biodiversity hotspots is highly recommended.