Salinity change effects on growth and photosynthetic efficiency of the<i> zooxanthellae Symbiodinium </i>sp. extracted from<i> Platygyra daedalea</i> in Qatar coral reefs

<p dir="ltr">This study investigates the impact of elevated <u>salinity </u>levels on the growth and <u>photosynthetic</u><u> efficiency</u> of the coral <u>endosymbiont Symbiodinium</u> sp. isolated from <i>Platygyra daedalea </i>in the coral reefs of Qatar. Cultures were exposed to a range of salinities (30–70 psu) over a 11-day<u> incubation period</u> under controlled laboratory conditions. Results revealed a significant decline in cell density and growth rate at salinities above 55 psu. Photosynthetic performance, assessed using the OJIP <u>chlorophyll fluorescence</u> protocol, showed a marked reduction in key parameters—including ABS/RC, DIo/RC, TRo/RC, ETo/RC, Vi, Vj, Mo, and Fv/Fm—at salinities exceeding 55 psu, indicating substantial stress and inactivation of PSII reaction centers. Interestingly, a partial recovery in <u>photosynthetic efficiency</u> was observed at 55 and 60 psu following initial decline. This is the first study to examine the <u>physiological response</u> of Symbiodinium sp. to salinity stress in the Arabian Gulf, providing valuable insights for coral reef restoration initiatives in this high-salinity environment amid ongoing <u>climate change </u>and coastal development.</p><h2>Other Information</h2><p dir="ltr">Published in: Marine Pollution Bulletin<br>License: <a href="http://creativecommons.org/licenses/by/4.0/" target="_blank">http://creativecommons.org/licenses/by/4.0/</a><br>See article on publisher's website: <a href="https://dx.doi.org/10.1016/j.marpolbul.2025.118187" target="_blank">https://dx.doi.org/10.1016/j.marpolbul.2025.118187</a></p>