Growth and carbonate production by Adeonellopsis (Bryozoa: Cheilostomata) in Doubtful Sound, New Zealand

The erect arborescent bryozoan Adeonellopsis sp. is an important component of the attached fauna on rock faces in Doubtful Sound, New Zealand. A program of marking and harvesting, radiocarbon dating, and morphometric study was undertaken to determine age, growth rate, and carbonate production rate of these colonies. Data from 40 branches on each of five colonies show a growth rate of 6.9 mm/yr in branch length. Colony growth rate varied, with 71% of growth (5 mm per branch) occurring from mid-summer and to mid-winter, and 29% (2 mm per branch) from mid-winter to late summer. Since proximal secondary thickening is common in adeoniform species, and occurs in Adeonellopsis, additional carbonate may be precipitated annually by this means. The largest colonies found in Doubtful Sound, some up to 30 cm in diameter, may be as much as 20 yr old, and precipitate calcium carbonate at a rate of 24 g CaCO3/yr. At Bauza Island, where our study was carried out, population densities of one large colony/m produced carbonate at a rate of 24 g CaCO3/m2/yr; maximum theoretical density could produce carbonate at 1042 g CaCO3/m2/yr. Carbonate produced at these rates would accumulate in sediments at 4–174 cm/kyr, reasonable rates for temperate carbonates. Adeonellopsis provides substrate for epizoa and hiding places for motile organisms. They form a potentially important fiord microhabitat, and their longevity allows both more ephemeral organisms and young longer-lived colonies to grow under their protection.