Monitoring of the in situ growth of three Acropora corals by individual identification over 5 years at the northern outer reef of Sekisei Lagoon (24°N), Okinawa

Abstract

We monitored juvenile Acropora corals (n = 719, <12 mm in the first survey) on the northern outer reef of the Sekisei Lagoon, 1 year after spawning in May 2008 and May 2009 and for the 4 subsequent years. The first-year colonies were an encrusting (EC) form. In the second year, approximately half of the colonies were of the EC form and the others grew one branch (OB) or several branches (SB). In the third year, two thirds of the colonies were of the EC–SB form, while the remainder grew wider branches (WB). After the third year, the WB colonies showed a typical species-specific growth form and spread laterally. Growth until the third year in the SB colonies was slow, while growth in the WB colonies was fast. Although we assumed that Acropora corals <12 mm in size were in their first year after a spawning event, 23 and 10 % of the second-year colonies (spawned in 2008 and 2009, respectively) were <12 mm. By the fifth year, three dominant corals were identified as different species, i.e., Acropora hyacinthus, Acropora digitifera, and Acropora nasuta, and their maximum sizes were 226, 202, and 144 mm, respectively.