Auto- and heterotrophic responses of the coralPorites luteato large amplitude internal waves

Abstract

SUMMARYLarge amplitude internal waves (LAIW) cause frequent and severe changes in the physico-chemical environment of Andaman Sea coral reefs and are a potentially important source of disturbance for corals. To explore the coral response to LAIW, prey capture disposition and photosynthesis were investigated in relation to changes in seawater temperature, pH, flow speed and food availability in LAIW simulation studies under controlled laboratory conditions, using Porites lutea as a model organism. Although food presence stimulated polyp expansion, we found an overriding effect of low temperature (19°C) causing retraction of the coral polyps into their calices, particularly when pH was altered concomitantly. Decreases in pH alone, however, caused the expansion of the polyps. The exposure history of the colonies played a crucial role in coral responses: prior field exposure to LAIW yielded lower retraction levels than in LAIW-inexperienced corals, suggesting acclimatization. Low temperature (19°C) exposure did not seem to influence the photosynthetic performance, but LAIW-experienced corals showed higher values of maximum dark-adapted quantum yield (F v /F m ) of photosystem II than LAIW-inexperienced controls. Collectively, these data suggest that P. lutea, the dominant hermatypic coral in the Andaman Sea, can acclimatize to extreme changes in its abiotic environment by modulating its mixotrophic nutrition, through polyp expansion and potential feeding, as well as its photosynthetic efficiency. Supplementary material available online at

Reduced heterotrophy in the stony coral Galaxea fascicularis after life-long exposure to elevated carbon dioxide

“…In contrast, another study observed that polyps from the coral P. lutea extended further under high CO 2 conditions24. During the second expedition, however, G. fascicularis polyps were expanded more, which happened to occur during a new moon compared to the first expedition that had a full moon.…”

Mangrove lagoons of the Great Barrier Reef support coral populations persisting under extreme environmental conditions

“…greater pH homeostasis at the site of calcification (Tambutté et al 2011(Tambutté et al , 2015. P. lutea has also previously been documented to acclimate to high environmental variance in temperature and pH through adjustments of heterotrophy versus photosynthetic nutrition (Pacherres et al 2013).…”

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“…This is in line with previous studies showing different sensitivities of phytoplankton or corals to UVR and temperature (Halac et al ). In T. reniformis , thermal stress alone decreased zooplankton grazing rates, most likely due to polyp retraction (L. C., personal observation), which is known to depend on environmental factors such as light, flow, and temperature (Pacherres et al ). However, this significant reduction in heterotrophic nutrient acquisition (CHAR dropped from 96% to 34%) did not affect the short‐term calcification and photosynthesis of T. reniformis , which remained equivalent to control condition.…”