Authors

Mariefe B. Quiñones

Author

Policarpo L. Openiano, Jr.

Co-author

Wilfredo H. Uy

Co-author

Institute of Fisheries Research and Development, Mindanao State University at Naawan, 9023 Naawan, Misamis Oriental, Philippines

*Corresponding author: [email protected]

ABSTRACT

Three different laboratory experiments were conducted to determine the effects of seven salinity levels: 5, 10, 15, 20, 32, 35 and 42 ppt (or g/L) on the hermatypic coral, Acropora yongei, and to what extent the coral may be restricted metabolically. The Photosynthesis-Irradiance (P-I) curve was also used as a means to quantify the rate of oxygen evolution at different light irradiances and as a tool to investigate the physiological effects of salinity variations. Salinity tolerance of A. yongei ranged from 20-35 pt but the coral was observed to tolerate lower salinity levels down to 15 ppt under short-term fluctuations from 32 ppt. Large variations in salinity induced a reduction in the photosynthesis and respiration of A. yongei which were most apparent at lower salinities (<20ppt). Net photosynthesis was higher in corals subjected to 20 ppt and 32 ppt at 76.4 m1g.O₂.mg⁻¹AFDW.h⁻¹ and 57.0 mg.O₂.mg⁻¹AFDW.h⁻¹, respectively, while respiration rates were higher at 5, 10 and 42 ppt. Maximum photosynthetic rate (88.12 mg.O₂.mg⁻¹AFDW.h⁻¹) at saturating irradiance (232.3 $\mu$mol photons m⁻²s⁻¹) was higher at 32 ppt . The generally steeper slopes of the curves obtained from the three salinity levels may indicate that the coral has the ability to photoadapt or acclimatize to the ambient environment. On the other hand, the higher photosynthesis to respiration ratio (1:81) and daily oxygen production at 306.2 mg.O₂.mg⁻¹AFDW.h⁻¹ at 32 ppt were observed to be adequate for autotrophic maintenance of A. yongei. Results of the experiment suggest that the coral A. yongei is a good candidate for transplantation particularly in areas where short-term fluctuations in salinity do not reach lethal levels of salinity l2ess than 15 ppt.