Why are coral susceptible to OA?
Coral is a shell-building organism likely to be affected by ocean acidification. Red tree coral (Primnoa pacifica), found in Alaska waters, are made of the most soluble form of calcium carbonate (high magnesium calcite). This puts it at a risk of physiological effects in a lower pH environment.
What questions are we trying to answer?
Research on the effects of ocean acidification on deep-sea corals has been limited. Red tree coral are ecologically important in the North Pacific Ocean and provide habitat for a wide range of commercial and other important fish and invertebrates.
To better understand the effects of ocean acidification on coral species in Alaska we are interested in a number of questions:
- Do coral polyps (animals that colonize to excrete and form calcium carbonate coral) survive changes in ocean pH?
- Does ocean acidification affect the deposition of calcium carbonate (growth) in a coral colony?
- Is the sclerite (needle-like calcium carbonate structure) density or morphology (shape) changed by ocean acidification?
- How is the reproductive biology affected by lower pH?
How can we test our hypotheses in the lab?
Laboratory studies have been conducted to first ensure that snippets of coral can successfully be kept alive in a laboratory, and then to test effects of ocean acidification by controlling pH. Coral are held in replicate tanks at a constant water temperature (~5°C) at an ambient and lower pH. The lower pH is set at what we expect these coral to experience within 100 years.
Divers collect red tree coral (normally found below 400 m) under glaciers in Southeast Alaska and collect a small portion of a colony to bring back to the laboratory.
What have we learned so far?
Initial studies have indicated that red tree coral can be successfully raised in the laboratory. Recent minerology analysis has shown that red tree coral are made of a particularly soluble form of calcium carbonate, and are therefore at risk of physiological effects due to ocean acidification. Coral are currently being held in treatments at the NOAA Kodiak Laboratory where initial size has been recorded. The experiment is expected to run for months (until winter 2017).
Thank you to the Alaska Fisheries Science Center for providing the information for this page.
Links and references
Alaska Fisheries Science Center OA page – contacts, reports, activities
Stone, R. P., M. M. Masuda, and J. F. Karinen. 2014. Assessing the ecological importance of red tree coral thickets in the eastern Gulf of Alaska. ICES Journal of Marine Science: doi: 10.1093/icesjms/fsu190.
Stone, R. P., J. Guinotte, A. Helbling, A. Cohen, and S. D. Cairns. In review. Potential effects of ocean acidification on Alaskan corals based on calcium carbonate mineralogy and other factors.
Stone, R. P., and J. Mondragon. In preparation. Deep-sea emergence of red tree corals (Primnoa pacifica) in Southeast Alaska glacial fjords.
Waller, R. G., R. P. Stone, J. Johnstone, and J. Mondragon. 2014. Sexual reproduction and seasonality of the Alaskan red tree coral, Primnoa pacifica. PLoSONE 9:e90893. doi:10.1371/journal.pone.0090893.