Day 23: The Coral Doctor explains all.....

Since our early morning arrival at the Hebrides Terrace seamount, and Helen's excitement about getting water samples from nearly 2000 m, the ROV has been busy surveying the seafloor. The coral biologists among us weren't too excited about the swaths of mud in every direction, but each to their own!

So, today's blog is written by one of those coral biologists, Janina Buscher from GEOMAR......
As a member of Team Coral on board the RRS James Cook, I am involved in the work that goes on outside with the experimental tanks in the hanger of this ship,  related to future scenarios of climate change conditions. As already explained by Helen, Laura and Penny, we are investigating the question of what might happen to the animals in our oceans – especially the most abundant cold-water coral Lophelia pertusa – when the ocean warms up and gets more acidic. Ocean warming and acidification caused by elevated atmospheric carbon dioxide concentrations is of greatest concern in higher latitudes and in cold deep waters. This is because carbon dioxide, which is mostly absorbed by the ocean from the atmospheres, dissolves more easily in these areas and is, hence, expected to have a stronger impact on the animals living there.

Preparing samples
 As a “coral doctor” – as I was called in an earlier blog – I am specifically interested in the health of the corals. I am trying to find out how fit the corals are and how this will change in response to more acidic waters or higher temperatures or even both in combination, like is expected to occur by the end of this century. So, how am I doing this? Well, I am analysing the fitness of the corals as well as the respiration rates. But unlike a human doctor, who would probably make you pedal on a training bike to measure your pulse after exercise, I estimate the coral’s fitness via a molecular method and the respiration rates via oxygen consumption.

Janina's samples
Measuring fitness on a molecular basis is possible in different ways. The way I am measuring is by examining the amount of Ribonucleic acid (RNA) compared to the amount of Deoxyribonucleic acid (DNA). RNA is the actively transcribed part of the genetic information, which is translated into proteins that are needed for all the corals metabolic processes. Therefore, the ratio of RNA to DNA shows how much of the genetic information is actually active, which gives us a hint of the coral’s fitness. The higher the RNA content, the more active and so the fitter they are. As I can’t analyse the RNA on board, I have to preserve the tissues in a specific solution for later analysis in my laboratory in Germany. So that I can compare how the fitness of the corals changes in response to future ocean acidification and warming, I fix the coral tissue of a few polyps before and after being incubated in the different experimental conditions.

I also have coral colonies from the Mingulay Reef Complex, in which I am measuring how much oxygen the coral fragments respire in a specific time span. I can do this is small sealed chambers with oxygen sensors. After I measured the respiration in all of the fragments, I incubated them for 10 days in the different climate change scenario treatment tanks. As I write this, I am currently halfway through my second period of respiration measurements. By measuring respiration rates in all fragments again, I can see if Lophelia pertusa breathes more under acidified or warmer water conditions, or if they might be able to acclimatise to oceanic conditions that are predicted for the future.

Old-school gas mixers
Aside from the corals, I am happy to see that the old-school gas-mixing pumps that enrich two of the treatment tanks in the hanger with a CO2-air gas mixture of about 750 µatm (predicted value for the end of this century), work pretty well and do their job quite precisely. The deep water pump, which I brought from Germany, purrs quietly ahead and regularly delivers water from deeper water layers, so that the corals get water similar to their natural environment. Above all, I am happy that Germany won the game against Portugal yesterday ;) and if everything goes on like this, the cruise will be completely successful!