Effect of Kappaphycus alvarezii mariculture on the recruitment of scleractinian corals

Abstract

Currently, the red alga Kappaphycus alvarezii is the species most commonly cultivated by seaweed farmers in the tropical Indo-Pacific. Seaweed farming over coral reefs is thought to have a negative impact on scleractinian corals. This study aims to determine the effect of K. alvarezii aquaculture over coral reefs on the recruitment of scleractinian corals. The study site was in Laikang Bay, Jeneponto Regency, South Sulawesi Province, Indonesia. This study used a grouped two level factorial design. The two factors were seaweed seed/clump spacing with 3 treatments (10, 20 and 30 cm) and controls with no seaweed; and substrate depth, with 2 levels (2 and 5 m). Grouping was based on planting period with replicates at 3 stations. The K. alvarezii cultivation media were bamboo rafts (2m x 2m) with polyethylene planting ropes. The rafts were moored at each site in the coral reef ecosystem for two planting periods. The 20 x 20 cm collector plates for coral settlement (total 72 per period) were placed on the substrate (sea bed) under the seaweed farming units and in the control areas (3 per raft or control area). The results showed that recruitment differed with substrate depth, seaweed spacing and planting period. The results indicate that at 30 cm spacing the seaweed farming did not have a significant effect on coral recruitment