Effects of eco-engineering drill-cored rock pools on rock revetment biodiversity on Penang Island

Rock pools are known to be an important habitat given the harsh nature of intertidal areas. While artificial rock pools mimicking the functions of natural rock pools were shown to provide valuable habitat on intertidal... [ view full abstract ]

Rock pools are known to be an important habitat given the harsh nature of intertidal areas. While artificial rock pools mimicking the functions of natural rock pools were shown to provide valuable habitat on intertidal breakwaters in the UK, the design has yet to be tested in a tropical setting. We hereby tested their ability to improve biodiversity on existing structures in Penang Island. The objectives of this study were to compare species richness and abundance between (1) drill-cored rock pools and adjacent rock surfaces, and (2) drill-cored rock pools of different depths. Thirty cylindrical drill-cored rock pools with diameters of 15 cm, separated into two depths: 12 cm (deep) and 5 cm (shallow), were drilled into granite rock revetments at three locations on Penang Island. The rock pools were monitored monthly for the first 12 months, followed by once every 6 months for 12 months. A total of 24 and 13 species were recorded within the rock pools and adjacent rock surfaces respectively. After 24 months, mean species richness was significantly higher in drill-cored rock pools than on adjacent emergent rock. There was no significant difference in mean species richness between deep and shallow drill-cored rock pools. Species abundance was higher in artificial rock pools than emergent surfaces except for barnacles, but similar between deep and shallow pools. These findings suggest that drill-cored rock pools could be installed on existing or new rock revetments in tropical as well as temperate settings to improve habitat heterogeneity and local biodiversity.