Abstract
Tropical coral reefs are threatened by local-scale stressors that are exacerbated by global ocean warming and acidification from the post-industrial increase of atmospheric CO2 levels. Despite their observed decline in the past four decades, little is known on how Philippine coral reefs will respond to ocean warming and acidification. This study explored individual and synergistic effects of present-day (pH 8.0, 28°C) and near-future (pH 7.7, 32°C) scenarios of ocean temperature and pH on the adult Favites colemani, a common massive reef-building coral in Bolinao-Anda, Philippines. Changes in seawater temperature drive the physiological responses of F. colemani, whereas changes in pH create an additive effect on survival, growth, and photosynthetic efficiency. Under near-future scenarios, F. colemani showed sustained photosynthetic competency despite the decline in growth rate and zooxanthellae density. F. colemani exhibited specificity with the Cladocopium clade C3u. This coral experienced lower growth rates but survived projected near-future ocean warming and acidification scenarios. Its pH-thermal stress threshold is possibly a consequence of acclimation and adaptation to local environmental conditions and past bleaching events. This research highlights the importance of examining the susceptibility and resilience of Philippine corals to climate-driven stressors for future conservation and restoration efforts in the changing ocean.
Highlights
Global warming and ocean acidification due to the unprecedented increase in anthropogenic CO2 emissions pose a serious threat to coral reefs worldwide (Hoegh-Guldberg et al, 2007)
Favites colemani corals still thrive in the Lucero reef in BARC, which is near Guiguiwanen channel. Could this be a consequence of acclimation and adaptation to local environmental conditions? To address this, we focused our work on this encrusting, submassive to massive reef-building coral F. colemani (Family Faviidae) commonly found in the Philippines (Veron, 2000; Maboloc et al, 2015)
This study aims to explore physiological responses of adult F. colemani from Lucero reef to near-future scenarios of ocean warming and acidification
Summary
Global warming and ocean acidification due to the unprecedented increase in anthropogenic CO2 emissions pose a serious threat to coral reefs worldwide (Hoegh-Guldberg et al, 2007). The ocean’s storage of 90% accumulated excess energy in the climate system over the past century led to a 0.6 ± 0.2◦C increase in global sea surface temperatures (IPCC, 2001; Hoegh-Guldberg et al, 2007). Under business-as-usual scenarios of atmospheric CO2 emission levels, global sea surface temperatures are projected to increase another 0.3–4.8◦C, and sea surface pH to further decrease by 0.06–0.32 pH units by the end of the twentyfirst century (IPCC, 2014). With the climate-driven changes in the ocean, coral reefs worldwide are
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