Growth in a modular colonial marine invertebrate

Growth rate, temporal variability and secondary production were quantified for the Mediterranean gorgonian Paramuricea clavata off Medes Islands, NW Mediterranean. Fifty-four colonies ranging in size between 5 and 860 cm in total length (3-55 cm maximum height) were monitored photographically for 2 years. Growth varied between and within years. Primary branches accounted for 91% of production, though their growth rates were highly variable (on average 23% of branches displayed zero growth). The gross growth rate of primary branches in colonies <20 cm was higher (0.8 cm year(-1)) than that of colonies >20 cm (0.5 cm years(-1)). On average, net growth of primary branches (0.4 cm year(-1)) was approximately 60% of positive growth. There was a significant size-specific negative growth effect in which year smaller colonies displayed higher rates of loss. Mean growth in colony height was 1.8 cm year(-1) (range: 0.2-6.4 cm year(-1)). Based on growth rate data, the largest colonies in the population (55 cm) were around 31 years old. On average, year net production for an colonies was 75% of gross production. Gross production was 4.4 g AFDW m(-2) year(-1), the production/biomass value was 0.11, and the turnover time was 9 years. Growth rate and its variation with colony size are discussed within the framework of the life history traits of the species. (C) 1998 Academic Press.