Coral Reefs on Oto Ndole-Ndole Blue Hole and Its Potential as Conservation Area
Blue hole is underwater depression (sinkhole), with circular shape in shallow water, and it has striking deep feature. Oto Ndole-Ndole blue hole (5o14'47.68"S and 123o32'18.29"E) is one of four in lines blue hole which is located in Wangi-Wangi island, Wakatobi National Marine Park. It has 9 m depth and directly towards to Banda Sea. Blue hole has circular shape, 5.543 m2 in area, 85m in length (from east to west), 55m in wide (from north to south). Bottom substrate is sandy rocky. Blue hole is located around 182m from shoreline. Blue hole waters is stable and protected from wave and current. This condition makes blue hole as unique marine habitat. The aim of this study is to determine coral reef biodiversity of blue hole and its potential as conservation area.
Coral reef coverage analysis was conducted with line intercept transect (LIT) method by surrounding along 100m blue hole. The ecosystem of coral reef coverage in Oto Ndole-Ndole blue hole was in good condition. It contains of 45,93% Heliopora; 7,97% Acropora; 3,73% Fungia; 1,68 % Montipora; 1,29% Milleopora; 1,01% Porites; 0,15 Platygyra; 0,07% Pocillipora and 10,52% soft coral.
The blue hole is habitat for hermathypic coral Heliopora coerulea (blue coral) and gorgonian Isis hippuris (bamboo coral). Blue coral dominates this area with 45,93% coverage, make columnar colonies following slope around blue hole from surface to the bottom.
Isis hippuris in this area has yellow-brownish in coloration; planar morphotype; short branch; 4,43±0,38 mm in diameter and 67,98 ±6,72 cm in height. This bamboo coral was found in 1-7 m depth and has association with other coral. Blue hole slope contour is appropriate with upward growth pattern of bamboo coral. The cleared, closed, and protected blue hole waters allow bamboo coral to grow and multiply with external brooding and asexual fragmentation. Bamboo coral's density in this area may reach 17 colonies/100m.
Coral reef in blue hole is different from surface coral reef in northside area. This area contain of 53,25% hard coral life 19,3% soft coral without any presence of Isis hippuris.
Protection of Oto Ndole-Ndole blue hole is necessary to protect vulnerable blue coral and overexploited bamboo coral that protected by Ministery of Marine Affairs and Fisheries regulation No.46/2014.