Introduction

R/V Pelagia Cruise CARBONATE

INTRODUCTION	Map of a part of the Atlantic Ocean with Ireland and the United Kingdom. The stars indicate the approximate locations of the areas we will visit during this cruise.

If asked where you would find corals, most people would probably mention places like the Great Barrier Reef, atolls in the Pacific Ocean, the Antilles, The Bahamas or other warm water areas of the world. However there is another group of corals. This group does not live in the warm and shallow parts of the oceans but is found in the cold and often deep ocean basins. Although cold water corals are known already for several hundreds of years, it is only since the late 1990's that these cold water corals attract the scientific attention on the scale they deserve.
During the past decade several research projects in which universities and research institutes of various European countries have participated have studied the corals along the European continental margin from the Mediterranean Sea up to Norway. Along the European continental margin the corals live for instance in the North Sea attached to oil platforms, in Norwegian fjords and attached to stones and rocky outcrops in the deeper parts of the Atlantic Ocean. West of Ireland, in the Atlantic Ocean, these corals form reefs in the shape of mounds consisting of a mix of coral debris, the calcareous skeletons of small single cellular animals, shells and other particles. The mounds range in height from about 5 to 380 metres and can be several kilometres across. In the past projects the focus of research has been on the life of the corals as such and the way in which the mounds are formed. In the present project, called CARBONATE, we will look at the mounds in a larger context. The main aim of the project is to study the role of these systems in the global carbon cycle. Carbon dioxide (CO₂) in the atmosphere is an important greenhouse gas. There is a continuous exchange of CO₂ between the atmosphere and the oceans. Corals and other animals (and some algae) that build a skeleton from calcium carbonate (CaCO₃) use (via some intermediate steps) CO₂that is dissolved in the ocean water to build their skeletons. Carbon (C) stored in the mounds as CaCO3 at the seafloor can not easily find its way back to the atmosphere as CO₂and contribute to the green house effect. In the CARBONATE project we want to find out how much carbon is stored in the cold water coral mounds and to what extend this influences the global carbon cycle, and thus the green house effect. In order to do so we want to drill through some of these mounds. If we recover the drilled sediments we will determine how old they are and then we can calculate how fast the mounds were growing during several periods in the geological past. So we can see how much carbon is stored in a certain amount of time and whether this is changing under different climate conditions (for instance, ice ages versus warm periods). During the present cruise we will not drill, that will be done sometime during the summer of 2008. The goal of the present cruise is to determine the most suitable locations for drilling. We will do this by means of seismic imaging (to look at the sediments below the seabed), video observations (to directly observe the corals), lander deployments (to measure currents and water temperature), multibeam mapping (to map the mounds), and box and piston coring (to sample the upper few decimetre to metres of sediments). Read our diary on this website to see how this equipment works, how we will use it and what else will happen on board until we return to Galway on 23 October.