Growth of deepsea coral: assessing potential impacts of ocean acidification

Chair: Peter Thor

Tracey, Di (1)*; Gammon, Malindi(2); Marriott, Peter(1); Cummings, Vonda(1); Neil, Helen(1); Davy, Simon(2)

1 National Institute of Water and Atmospheric Research (NIWA), Wellington 6022, New Zealand.
2 Victoria University of Wellington (VUW), Wellington 6012, New Zealand.

The large reef–forming scleractinian stony coral ( Solenosmilia variabilis) is one of New Zealand’s most common deepsea habitat forming coral species. It has a wide spatial distribution, thrives at depths of 800 – 1200 m, and provides important habitat and refuge for many deepsea invertebrates and fish. Such deep, cold water environments are predicted to be affected by ocean acidification much sooner than more temperate regions. Previous work on S. variabilis has shown it to be a robust species for in aquaria studies and with several newly sampled colonies taken from the region, we have initiated an experiment to improve our knowledge of its growth patterns, both under ambient conditions and in response to elevated pCO2, the latter in order to assess its potential resilience to levels of ocean acidification. The experiment began in mid-September, 2014. Colony morphology (growth), weight, and polyp health are being assessed at 2 monthly intervals. The colonies have survived well in their laboratory environment and remain alive 20 months on since collection. There have been 8 intermediate sampling points to date and our analysis of bi-monthly photographs to measure linear extension and the buoyant weight data indicate no significant changes in growth. This is expected for such a slow growing organism as S. variabilis where linear growth rates estimated for this species from radiocarbon dating range from 0.3 to 1.3 mm/yr. The experiment will need to run for several years, periodically assessing growth along with intracellular functioning of individual colonies. It is hoped that this study will help inform predictions of how deep sea ecosystems might be impacted by ocean acidification and help assess recovery potential from this and other anthropogenic impacts.