14. August 2014

Lophelia, how are you?

Scientists recover instruments and long-term experiments from two Norwegian cold-water coral reefs

How do cold-water corals react to changing environmental conditions such as rising water temperatures and ocean acidification? Will the fragile reefs survive climate change?

The 473rd expedition of the German research vessel POSEIDON helps to answer urgent questions about the future of marine ecosystems. The cruise that is led by GEOMAR Helmholtz Centre for Ocean Research Kiel takes place in the framework of the German research network on ocean acidification BIOACID (Biological Impacts of Ocean Acidification) also involves scientists from Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, the Institute of Marine Research Bergen, the University of Fribourg and the Senkenberg am Meer, Wilhelmshaven. It starts on Friday, August 15 in Tromsø, Northern Norway, and ends on September 4, 2014 in Esbjerg, Denmark.

One year ago, the research team had placed so-called “landers” at coral reefs in the outer Trondheim Fjord and the Sula Reef off the coast of Central Norway. Over a period of twelve months, these measurement units recorded water temperature, salinity, pressure, pH, oxygen, currents, tides and other parameters in water depths between 175 and 300 meters. Now the landers are recovered. “We are very excited about the data. Never before had so many physical and biogeochemical parameters been measured in a cold-water coral reef over such a long period of time”, says chief scientist Dr. Armin Form of GEOMAR. “It is very important for us to see the natural development over days and seasons. With this knowledge we can give more accurate predictions for the future of the reefs and make our laboratory experiments more realistic.”

To measure growth rates of cold water corals in their natural environment, single individual coral branches were recovered from the reefs in July 2013 and weighed. The outer layers of their carbonate skeleton were colour-marked before these samples were put back into the reefs in small plastic cages. Now investigations shall show how the animals have evolved. “Lophelia pertusa, the coral we mainly work with, grows about a centimetre per year,” GEOMAR marine biologist Janina Büscher explains. “We will check the layers that have grown since last year thoroughly and match our observations with the lander measurements. We will also test the metabolic rate and fitness. It will be particularly interesting to compare samples from the Sula Reef far out at sea with the samples from the Trondheim Fjord, where the corals are much more exposed to human influences.”

The research submersible JAGO will carefully bring the samples back to the surface. Furthermore, the researchers are going to collect corals for new experiments with the help of JAGO. Long-term experiments will be conducted to investigate how ocean acidification, rising water temperatures and food availability affect basic physiological mechanisms of cold-water corals, shells and sponges. To further track the changes in the reef further and to quantify the biodiversity extensive video documentations are planned.

The participants of the expedition POS 473 are going to publish news from board regularly in their blog at www.oceanblogs.org/pos473