Earth’s climate may be changing too rapidly for coral to adapt through natural selection. Other mechanisms, however, may help the offspring of corals that have been exposed to the environmental stressors of a warmer and a more acidic ocean, conditions that have caused coral bleaching and slowed new growth of coral reefs.
To test for such mechanisms, two researchers at the University of Hawaii, Hollie Putnam and Ruth Gates, placed colonies of adult cauliflower coral (Pocillopora damicornis) either in tanks where water temperature and acidity were similar to their collection site in Kaneohe Bay, Hawaii (ambient treatment), or in water with higher temperature and higher acidity (high treatment). The adults lived in these environments for a month and a half, slightly longer than the time needed for larvae to develop.
Toward the end of this period, during a four-day lunar peak of release, just over half the adult colonies produced larvae. The larvae were collected and then moved to a secondary treatment in one or the other water condition. After five days in their new environment, the size and metabolic rate of the newborns were measured.
Parents subjected to high treatment were negatively affected by their exposure, and their offspring were smaller than offspring from parents in ambient water. Surprisingly, the offspring showed some striking differences in their respiration rate. Whereas the offspring of ambient treatment adults had the same respiration rate regardless of which kind of water they later landed in, the offspring of high treatment adults showed a lower respiration rate when they were in ambient water and a higher respiration rate in the high treatment water. They were able to adjust their metabolism in the face of harsh environmental conditions.
“Our finding of trans-generational acclimatization suggests there may be more rapid response mechanisms that could help to buffer corals against the quickly changing climate then we previously thought,” said Putnam. She cautions, however, that so far only one generation of newborn corals have been studied, and the long-term impact of parental exposure remains unknown. “More research is required to track the corals over months to years, which we are doing.” (The Journal of Experimental Biology)