Coral Reef within a Hydrothermal Vent as an Indicator to the Future of Shallow Water Tropical Reefs Threatened by Ocean Acidification

Chair: Ana Queiros

Nithiyaa Nilamani (1)*, Zulfigar Yasin (1,2), Vashiraporn Sriboonruang (2), Zulfikar (1,3), Norhanis Razalli (1), and Aileen Tan Shau Hwai (1)

1 Marine Science Lab, School of Biological Sciences, Universiti Sains Malaysia, Minden, Penang, 11800, Malaysia
2 Institute of Oceanography and Environment, Universiti Terengganu Malaysia, Kuala Terengganu, Terengganu, 21030, Malaysia
3 Universitas Malikussaleh, Lhokseumawe, Provinsi Acheh, Indonesia

Background
Naturally acidified reef ecosystem such as hydrothermal vent has become a natural laboratory for ocean acidification study. The pH of seawater at the study area ranged from 6.99 to 8.01, which approaches the projected scenarios of the year 2100.

Methods
Field survey was carried out to measure the in-situ pH, temperature and salinity at study sites. 5 meter long transect were laid parallel to the shore at 4 m depth (5 transects at hydrothermal site and 1 at control site). Photographs were taken at every meter along the transect to determine the coral cover and species diversity.

Findings
The gas produced in the vicinity of the hydrothermal vent affected the pH of the seawater in the area. The pH of seawater ranged from 6.99 to 8.01. The study also indicates a significant increase (R2=0.916, P<0.05) in live coral cover and diversity as it gets away from the vent following the increase in pH towards normal seawater values. Highest live coral cover was recorded at the furthest station from the vent (0.48 ± 0.08m2) with 13 coral genera. The dominant coral that was found to be surviving in such area was Porites sp.

Conclusions
This provides an opportunity to look at the effect of the acidified seawater on the natural ecology of shallow water reefs and adaptation of the reef to this extreme environment.