Growth in a Modular Colonial Marine Invertebrate

Growth rate, temporal variability and secondary production were quantified for the Mediterranean gorgonianParamuricea clavataoff 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 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, net production for all colonies was 75% of gross production. Gross production was 4•4 g AFDW m−2year−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.