6 Did Quaternary Climate Fluctuations Affect Mediterranean Deep-Sea Coral Communities?

We generated records of radiocarbon and trace metals in deep-sea corals to investigate the role of the deep ocean during episodes of rapid environmental change. Our record of radiocarbon ages measured in a modern deep-sea coral from the northeastern Atlantic shows the transfer of bomb radiocarbon from the atmosphere to the deep ocean. We detect bomb radiocarbon at the coral growth site starting in 1975–1979. Our record documents a Delta14C increase from –80 ± 1‰ (average 1930–1979) to a plateau at –39 ± 2‰ (average 1994–2001). From a suite of fossil deep-sea corals, variability in North Atlantic intermediate water Delta14C during the Younger Dryas (13.0–11.5 ka) supports a link between abrupt climate change and intermediate ocean circulation. We observe rapid shifts in deep-sea Delta14C that require the repositioning of large Delta14C gradients within the North Atlantic. The shifts are consistent with changes in the rate of North Atlantic Deep Water formation. We also observe a decadal scale event at 12.0 ka that is marked by the transient return of radiocarbon to the eastern and western basins of the North Atlantic. To develop a nutrient proxy for use in deep-sea corals, we measured Cd/Ca in 14 modern corals. Several of these corals had anomalously high Cd/Ca that we explain with a systematic bias in Cd/Ca obscuring the signal of seawater Cd/Ca. When these high Cd/Ca corals are removed from the calibration, the best-fit coral-water partition coefficient is 1.3 ± 0.1. Examining Cd/Ca in fossil deep-sea corals, we find that our coral from the Younger Dryas (12.0 ka) resembles the high Cd/Ca corals of the modern calibration and probably does not reflect seawater Cd/Ca. The Cd/Ca record from a 15.4 ka coral resembles our low Cd/Ca calibration samples and probably reflects average seawater Cd/Ca.

We generated records of carbonate clumped isotopes and radiocarbon in deep-sea corals to investigate the role of the deep ocean during rapid climate change events. First we calibrated the carbonate clumped isotope thermometer in modern deep-sea corals. We examined 11 specimens of three species of deep-sea corals and one species of a surface coral spanning a total range in growth temperature of 2–25°C. We find that skeletal carbonate from deep-sea corals shows the same relationship of Δ47 to temperature as does inorganic calcite. We explore several reasons why the clumped isotope compositions of deep-sea coral skeletons exhibit no evidence of a vital effect despite having large conventional isotopic vital effects. We also used a new dating technique, called the reconnaissance dating method to investigate the ecological response of deep-sea coral communities in the North Atlantic and Southern Ocean to both glaciation and rapid climate change. We find that the deep-sea coral populations of D. dianthus in both the North Atlantic and the Southern Ocean expand at times of rapid climate change. The most important factors for controlling deep-sea coral distributions are likely climatically driven changes in productivity, [O2] and [CO32-]. We take 14 deep-sea corals that we had dated to the Younger Dryas (YD) and Heinrich 1 (H1), two rapid climate change events during the last deglaciation and make U-series dates and measure clumped isotopes in them. We find that temperatures during the YD and H1 are cooler than modern and that H1 exhibits warming with depth. We place our record in the context of atmospheric and marine benthic Δ14C, δ13C, and δ18O records during the deglaciation to understand the role of the deep North Atlantic during the deglaciation. We also investigated the role of climate change in the distribution of terrestrial megafauna. To help with this, we also developed a method for compound-specific radiocarbon dating of hydroxyproline extracted from bones in the La Brea Tar Pits. We find that the radiocarbon chronologies of megafauna from several locations around the world, including the La Brea Tar Pits, exhibit an increase in abundance of megafauna during Heinrich events.

The formation of cold-water coral (CWC) mounds is commonly seen as being the result of the sustained growth of framework-forming CWCs and the concurrent supply and deposition of terrigenous sediments under energetic hydrodynamic conditions. Yet only a limited number of studies investigated the complex interplay of the various hydrodynamic, sedimentological and biological processes involved in mound formation, which, however, focused on the environmental conditions promoting coral growth. Therefore, we are still lacking an in-depth understanding of the processes allowing the on-mound deposition of hemipelagic sediments, which contribute to two thirds of coral mound deposits. To investigate these processes over geological time and to evaluate their contribution to coral mound formation, we reconstructed changes in sediment transport and deposition by comparing sedimentological parameters (grain-size distribution, sediment composition, accumulation rates) of two sediment cores collected from a Mediterranean coral mound and the adjacent seafloor (off-mound). Our results showed that under a turbulent hydrodynamic regime promoting coral growth during the Early Holocene, the deposition of fine siliciclastic sediments shifted from the open seafloor to the coral mounds. This led to a high average mound aggradation rate of >130 cm kyr–1, while sedimentation rates in the adjacent off-mound area at the same time did not exceed 10 cm kyr–1. Thereby, the baffling of suspended sediments by the coral framework and their deposition within the ecological accommodation space provided by the corals seem to be key processes for mound formation. Although, it is commonly accepted that these processes play important roles in various sedimentary environments, our study provided for the first time, core-based empirical data proving the efficiency of these processes in coral mound environment. In addition, our approach to compare the grain-size distribution of the siliciclastic sediments deposited concurrently on a coral mound and on the adjacent seafloor allowed us to investigate the integrated influence of coral mound morphology and coral framework on the mound formation process. Based on these results, this study provides the first conceptual model for coral mound formation by applying sequence stratigraphic concepts, which highlights the interplay of the coral-framework baffling capacity, coral-derived ecological accommodation space and sediment supply.

<strong class="journal-contentHeaderColor">Abstract.</strong> Framework-forming cold-water corals are ecosystem engineers that build mounds in the deep-sea that can be several hundred meters high. The effect of the presence of cold-water coral mounds on their surrounding is typically difficult to separate from environmental factors that are not affected by the mounds. We investigated the environmental control on cold-water coral reefs at multiple spatial scales, using annotated video transects data, spatial variables (MEMs) and hydrodynamic model output in a redundancy analysis and with variance partitioning. Using available hydrodynamic simulations with cold-water coral mounds and simulations where the mounds were artificially removed, we investigated the effect of coral mound ecosystem engineering on the spatial configuration of reef habitat and discriminated which environmental factors are and which are not affected by the mounds. We find that, due to the interaction between the coral mound and the water flow, different hydrodynamic zones are created on a coral mound that likely determine the typical benthic zonation of coral rubble at the mound foot, dead coral framework on the mound flank, and living corals near the summit. Moreover, we observed a so-called massenerhebung effect (well-known for terrestrial mountains) meaning that benthic zonation depends on the location on the mound rather than on the height above the seafloor or water depth. Our finding that ecosystem engineering determines the configuration of benthic habitats on cold-water coral mounds has many implications, such as that cold-water corals cannot simply move towards deeper water depths to avoid the adverse effects of climate change. We further find that downward velocities in winter, related to non-engineered environmental factors, e.g., deep winter mixing and dense water cascading, correlated to substantial differences in reef cover at the broadest spatial scale (20&ndash;30 km). Such hydrodynamic processes that stimulate the food supply towards the corals in winter are more important for the reefs than similar hydrodynamic processes in summer. There is much research on the ecosystem engineering effects of cold-water corals, but our results highlight that the influence of non-engineered environmental processes that accelerate the food supply towards the cold-water corals should not be underestimated.

Cold-water coral mounds in an erosive environmental setting: TOBI side-scan sonar data and ROV video footage from the northwest Porcupine Bank, NE Atlantic

Cold-water coral (CWC) reefs are distributed globally and form complex three-dimensional structures on the deep seafloor, providing habitat for numerous species. Here, we measured the community O2 and dissolved inorganic nitrogen (DIN) flux of CWC reef habitats with different coral cover and bare sediment (acting as reference site) in the Logachev Mound area (NE Atlantic). Two methodologies were applied: the non-invasive in situ aquatic eddy co-variance (AEC) technique, and ex situ whole box core (BC) incubations. The AEC system was deployed twice per coral mound (69 h in total), providing an integral estimate of the O2 flux from a total reef area of up to 500 m2, with mean O2 consumption rates ranging from 11.6 ± 3.9 to 45.3 ± 11.7 mmol O2 m-2 d-1 (mean ± SE). CWC reef community O2 fluxes obtained from the BC incubations ranged from 5.7 ± 0.3 to 28.4 ± 2.4 mmol O2 m-2 d-1 (mean ± SD) while the O2 flux measured by BC incubations on the bare sediment reference site reported 1.9 ± 1.3 mmol O2 m-2 d-1 (mean ± SD). Overall, O2 fluxes measured with AEC and BC showed reasonable agreement, except for one station with high habitat heterogeneity. Our results suggest O2 fluxes of CWC reef communities in the North East Atlantic are around five times higher than of sediments from comparable depths and living CWCs are driving the increased metabolism. DIN flux measurements by the BC incubations also revealed around two times higher DIN fluxes at the CWC reef (1.17 ± 0.87 mmol DIN m-2 d-1), compared to the bare sediment reference site (0.49 ± 0.32 mmol DIN m-2 d-1), due to intensified benthic release of NH4+. Our data indicate that the amount of living corals and dead coral framework largely contributes to the observed variability in O2 fluxes on CWC reefs. A conservative estimate, based on the measured O2 and DIN fluxes, indicates that CWC reefs process 20% to 35% of the total benthic respiration on the southeasterly Rockall Bank area, which demonstrates that CWC reefs are important to carbon and nitrogen mineralization at the habitat scale.

Oxygen isotopic analysis of Globigerina-ooze cores from the Atlantic and adjacent seas showed that surface ocean temperatures underwent numerous, apparently periodical, variations during the past few hundred thousand years. C14 dating showed that the last temperature minimum of the deep-sea cores was synchronous with the last major glaciation, the Main Würm. Previous attempts to date deep-sea cores were based on the decay of uranium-unsupported Th230 (ionium). This method requires, among other conditions, that the supply of uranium-supported Th230 in sea water and the rate of non-carbonate sedimentation remained essentially constant over the time interval to be dated. Attempts to correct for possible variations in the non-carbonate sedimentation rate have been made by using such ratios as Th230/Th232 or Th230/Fe2O3. The validity of these corrections is questionable because Th230 produced in sea water by the decay of U238 and U234 has a geochemical history different from that of Th232 and Fe2O3. The requirements mentioned above need not be met if the ratio $$Pa^{231}/Th^{230}$$ is used. Since Pa231 and Th230 are daughters of the same element, uranium, and since they decay at different rates, their ratio is a function of time alone. While information from deep-sea cores, bearing directly on Pleistocene history, has been obtained almost exclusively by isotopic and micropaleontological analysis of the foraminiferal component of Globigerina-ooze cores, dating by the decay of uranium-unsupported Th230 or by the ratio $$Pa^{231}/Th^{230}$$ is based on the clay component where these nuclides are concentrated. Therefore, dating, by these two methods, of the stratigraphic record given by the foraminiferal component requires synchronism between the two components. Such synchronism may be exceptional, for the clay component may frequently or even generally contain some or much reworked material, even when the foraminiferal record is undisturbed. In such cases, the ages obtained may be generally greater than the ages of the events to be dated. $$Pa^{231}/Th^{230}$$ dating of two deep-sea cores from the Caribbean, about 600 km. apart, has given a set of dates which are internally consistent; identical, within the limits of error, in stratigraphically equivalent levels of the two cores; and coincident with the C14 chronology. This set of dates is believed to provide a reliable, absolute time scale, extending from the present to about 175,000 years ago. $$Pa^{231}/Th^{230}$$ and C14 measurements on deep-sea cores, C14 measurements on continental material, paleotemperature analysis of deep-sea cores, and correlation of the temperature record of the deep-sea cores with continental events provide the following ages for Pleistocene stages: postglacial, 0-10,000 years; Late and Main Wurm, 10,000-30,000 years; Main Würm-Early Würm interval, 30,000-50,000 years; Early Würm, 50,000-65,000 years; Riss/Würm interglacial, 65,000-100,000 years; Riss, 100,000-130,000 years; and Mindel/Riss interglacial, 130,000-175,000 years. These ages are very close to or identical with the ages given by Emiliani (1955a, 1958). Correlation between temperature variations of the deep-sea cores and continental stages preceding the last interglacial, however, is only tentative. The apparent identity of the C14 and $$Pa^{231}/Th^{230}$$ chronologies over the entire range of the C14 method indicates that the cosmic-ray flux did not change by more than a factor of 2 during the past 60,000 years. $$Pa^{231}/Th^{230}$$ dating of a deep-sea core from the North Atlantic gave ages which are consistently about 30,000 years greater than the $$Pa^{231}/Th^{230}$$ ages obtained from the two Caribbean cores and the C14 chronology. This is believed to result from contamination by reworked clay, an effect which may actually exist in most deep-sea cores. Rates of sedimentation of the carbonate fraction larger than 62 μ, the carbonate fraction smaller than 62 μ, and the non-carbonate fraction, calculated for the intervals between selected dated levels, appear not to have changed markedly when averaged over time intervals of some tens of thousands of years. The rates of sedimentation during the last 11,000 years, however, were lower than during previous time intervals. A generalized temperature curve, calibrated in terms of the C14-$$Pa^{231}/Th^{230}$$ chronology, is presented. This curve is very close to the curve previously constructed by Emiliani (1955a, 1958).

Within the Porcupine Bank Canyon (NE Atlantic), cold-water coral (CWC) mounds are mostly found clustered along the canyon lip, with individual disconnected mounds occurring nearby on the western Porcupine Bank. Remotely operated vehicle-mounted vibrocoring was utilized to acquire cores from both of these sites. This study is the first to employ this novel method when aiming to precisely sample two closely situated areas. Radiometric ages constrain the records from the early to mid-Holocene (9.1 to 5.6 ka BP). The cores were then subjected to 3D segmented computer tomography to capture mound formation stages. The cores were then further examined using stable isotopes and benthic foraminiferal assemblages, to constrain the paleoenvironmental variation that influenced CWC mound formation of each site. In total, mound aggradation rate in the Porcupine Bank Canyon and western Porcupine Bank was comparable to other Holocene CWC mounds situated off western Ireland. Results derived from multiproxy analysis, show that regional climatic shifts define the environmental conditions that allow positive coral mound formation. In addition, the aggradation rate of coral mounds is higher adjacent to the Porcupine Bank Canyon than on the western Porcupine Bank. Benthic foraminifera assemblages and planktic foraminiferal δ13C reveal that higher quality organic matter is more readily available closer to the canyon lip. As such, we hypothesize that coral mound formation in the region is likely controlled by an interplay between enhanced shelf currents and the existence of the Eastern North Atlantic Water-Mediterranean Outflow Water-Transition Zone. The geomorphology of the canyon promotes upwelling of these water masses that are enriched in particles, including food and sediment supply. The higher availability of these particles support the development and succession of ecological hotspots along the canyon lip and adjacent areas of the seafloor. These observations provide a glimpse into the role that submarine canyons play in influencing macro and micro benthic fauna distributions and highlights the importance of their conservation.

Glacial-interglacial cycles, occurring at a period of approximately 100,000 years, have dominated Earth's climate over the past 800,000 years. These cycles involve major changes in land ice, global sea level, ocean circulation, and the carbon cycle. While it is generally agreed that the ultimate driver of global climate is changes in insolation, glacial cycles do not look like insolation forcing. Notably, there is a highly non-linear warming response at 100,000 years to a relatively small forcing, implicating a more complicated system of biogeochemical and physical drivers. The ocean plays a pivotal role in glacial-interglacial climate through direct equator-to-pole transport of heat and its role in the carbon cycle. The deep ocean contains 60 times more carbon than the atmosphere, and therefore even small changes in ocean circulation can have a large impact on atmospheric CO2, a crucial amplifier in the climate system. In order to better understand the role that ocean circulation plays in glacial-interglacial climate we focus on the last glacial-interglacial transition. In this thesis, we present reconstructions of changes in intermediate water circulation and explore a new time-dependent dynamical box model. We reconstruct circulation using radiocarbon and clumped isotope measurements on U/Th dated deep-sea corals from the New England and Corner Rise Seamounts in the western basin of the North Atlantic and from south of Tasmania in the Indo-Pacific sector of the Southern Ocean. Our new time-dependent model contains key aspects of ocean physics, including Southern Ocean Residual Mean theory, and allows us to explore dynamical mechanisms which drive abrupt climate transitions during the last glacial period. In Chapter 2 we present a compilation of reconnaissance dated deep-sea corals from the Caltech collection. Reconnaissance dating facilitates sample selection for our high-precision radiocarbon and temperature time series and patterns in the depth distribution of deep-sea corals over time contain additional relevant climate information. In Chapter 3, we present a high-resolution radiocarbon record from south of Tasmania which highlights variability in Southern Ocean Intermediate Water radiocarbon during the deglaciation, particularly during the Antarctic Cold Reversal. We use our radiocarbon data, in combination with other deglacial climate records, to infer changes in overturning circulation configuration across this time interval. In Chapter 4 we present our time-dependent dynamical box model. Our model displays hysteresis in basin stratification and Southern Ocean isopycnal outcrop position as a function of North Atlantic Deep Water formation rate. In a dynamical system, hysteresis implies that there are multiple stable states, and switches between these states can lead to abrupt transitions, such as those observed during the middle of the last glacial period. In Chapter 5 we present paired radiocarbon and temperature time series from the North Atlantic and Southern Ocean spanning the late part of the last glacial. We explore the mechanisms driving trends in radiocarbon and temperature by looking at cross-plots of the data, and we make inferences about changes in circulation configuration using insight gained from our dynamical box model.

We study the total carbonate profiles of three coastal cores extracted from the continental shelf in the Ionian Sea and of two deep-sea cores extracted from the Tyrrhenian abissal plane. An overall similarity between the two deep-sea profiles and among the three coastal profiles is observed, indicating the complete reproductibility of this type of experimental measurements. In the case of the coastal cores, a constant sedimentation rates=(0.0646±0.0007) cm/y has been determined by radiometric methods and by tephroanalysis. For the deep-sea cores, the spectra of the upper and lower halves of the carbonate depth profiles display the same periodic components, suggesting that the sedimentation rate is nearly the same along the entire deep cores as well. The use of a careful tephroanalysis, the recognition of the Ignimbrite layers of Campanian origin at the expected depths and the similarity between the upper part (5000y) of the carbonate profile of the deep-sea core with that of the coastal cores provide the indication that, on the average, 1 cm of sediment is deposited in about 100 y. We show that the trend of the carbonate record in the deep-sea core is well approximated by a signal obtained by linearly superposing the obliquity and the precession parameters of the Earth rotation axis. Since these astronomical factors contribute to the temporal variations of the Earth insolation, and since the CaCO3 content of the sediment is presumably affected by climatic factors, this result supports the evidence of astronomical control on the Earth's climate, as already pointed out by several authors who analysed the power spectra of δ18O, δD and CO2 temporal series from sediment and ice cores. After removal of the «astronomical» trend, the carbonate record displays a dominant periodicity at approximately 12000 y. The 12000 y wave, taken with the opposite sign, corresponds to the trend of the radiocarbon record in tree-rings. This result becomes particularly relevant in view of the existence of common periodicities of about 200 y waves (Suess wiggles) which have already been detected in the carbonate profiles of the coastal cores and in tree-ring radiocarbon data.

Cold-water corals form substantial biogenic habitats on continental shelves and in deep-sea areas with topographic highs, such as banks and seamounts. In the Atlantic, many reef and mound complexes are engineered by Lophelia pertusa, the dominant framework-forming coral. In this study, a variety of mapping approaches were used at a range of scales to map the distribution of both cold-water coral habitats and individual coral colonies at the Mingulay Reef Complex (west Scotland). The new ArcGIS-based British Geological Survey (BGS) seabed mapping toolbox semi-automatically delineated over 500 Lophelia reef ‘mini-mounds’ from bathymetry data with 2-m resolution. The morphometric and acoustic characteristics of the mini-mounds were also automatically quantified and captured using this toolbox. Coral presence data were derived from high-definition remotely operated vehicle (ROV) records and high-resolution microbathymetry collected by a ROV-mounted multibeam echosounder. With a resolution of 0.35 × 0.35 m, the microbathymetry covers 0.6 km2 in the centre of the study area and allowed identification of individual live coral colonies in acoustic data for the first time. Maximum water depth, maximum rugosity, mean rugosity, bathymetric positioning index and maximum current speed were identified as the environmental variables that contributed most to the prediction of live coral presence. These variables were used to create a predictive map of the likelihood of presence of live cold-water coral colonies in the area of the Mingulay Reef Complex covered by the 2-m resolution data set. Predictive maps of live corals across the reef will be especially valuable for future long-term monitoring surveys, including those needed to understand the impacts of global climate change. This is the first study using the newly developed BGS seabed mapping toolbox and an ROV-based microbathymetric grid to explore the environmental variables that control coral growth on cold-water coral reefs.

The functional diversity and redundancy of corals

Pleistocene interglacials are often considered to be possible geological analogs for the climatic development of the Holocene epoch. Marine isotope stage 11 (MIS 11), a prominent interglacial 400 ky ago, is of particular interest because of the similarity between orbitally driven insolation variations then and now. We have examined the record of climatic conditions during MIS 11 at two locations on rapidly accumulating sediment drifts in the North Atlantic, and made a comparison with global records in order to assess the duration, stability, and amplitude of the interglacial. Deep-sea cores from ODP Sites 980 and 983 have sedimentation rates in excess of 10 cm/kyr, and have been sampled at 2-3 cm intervals, yielding century-scale resolution of millennial-scale variability. We used stable isotopes of oxygen in foraminifera to assess climatic and hydrographic conditions at the sea surface and in the deep ocean. Different age models were evaluated, including one tuned to orbital insolation variations and one based on a constant accumulation model. These chronologies indicate that the relatively ice-free portion of MIS 11 lasted longer than other peak interglacials. Sea surface warmth in the subpolar North Atlantic lasted even longer, a minimum of 30 kyr. Throughout this interval, oxygen isotope ratios in Neogloboquadrina pachyderma (dextral), a proxy for sea-surface temperature (SST), did not vary more than 0.25 per mil, or ∼1°C, from the long-term mean. This is in strong contrast to the large temperature oscillations in the subsequent glaciation, MIS 10. During both the interglacial and glacial, a gradient in planktonic oxygen isotope ratios was maintained between the two sites, counter to the modern salinity-driven gradient in seawater oxygen isotope ratios, and therefore consistent with a persistent similar N-S temperature gradient. Oxygen isotope ratios recorded during MIS 11 in both planktonic and benthic foraminifera are similar to values that characterize the Holocene. Thus ice-volume (sea-level), ocean temperature, local salinity, and the isotopic composition of ice sheets were similar, in sum, to today. Any departure from the modern values in one of these climate components would have had to be compensated by some combination of the others. We conclude that the elapsed portion of the Holocene has been similar to MIS 11 in mean climate state and degree of stability, without nearly approaching its duration. Both the forcing and response of climate during MIS 11 appear to be appropriate analogs for the natural development of recent and future climate.

Abstract. Framework-forming cold-water corals (CWCs) are ecosystem engineers that build mounds in the deep sea that can be up to several hundred metres high. The effect of the presence of cold-water coral mounds on their surroundings is typically difficult to separate from environmental factors that are not affected by the mounds. We investigated the environmental control on and the importance of ecosystem engineering for cold-water coral reefs using annotated video transect data, spatial variables (MEMs), and hydrodynamic model outputs in a redundancy analysis and with variance partitioning. Using available hydrodynamic simulations with cold-water coral mounds and simulations where the mounds were artificially removed, we investigated the effect of coral mound ecosystem engineering on the spatial configuration of reef habitat and discriminated which environmental factors are and which are not affected by the mounds. We find that downward velocities in winter, related to non-engineered environmental factors, e.g. deep winter mixing and dense-water cascading, cause substantial differences in reef cover at the broadest spatial scale (20–30 km). Such hydrodynamic processes that stimulate the food supply towards the corals in winter seem more important for the reefs than cold-water coral mound engineering or similar hydrodynamic processes in summer. While the ecosystem-engineering effect of cold-water corals is frequently discussed, our results also highlight the importance of non-engineered environmental processes. We further find that, due to the interaction between the coral mound and the water flow, different hydrodynamic zones are found on coral mounds that likely determine the typical benthic zonations of coral rubble at the mound foot, the dead coral framework on the mound flanks, and the living corals near the summit. Moreover, we suggest that a so-called Massenerhebung effect (well known for terrestrial mountains) exists, meaning that benthic zonation depends on the location of the mound rather than on the height above the seafloor or water depth. Our finding that ecosystem engineering determines the configuration of benthic habitats on cold-water coral mounds implies that cold-water corals cannot grow at deeper depths on the mounds to avoid the adverse effects of climate change.

The scientific objectives of METEOR cruise M84/5 focused on the measurement and analysis of the environmental controls of modern and fossil cold-water coral growth along a transect in the Bay of Biscay. In four working areas we successfully deployed lander systems and CTD/Ro’s to document the physical and hydrochemical characteristics of bottom water masses and the water column in general. These are used to shed light on potential linkages to modern cold-water coral growth and distribution. These investigations were flanked by plankton tows in surface waters. The base for all investigations was a thorough hydroacoustic survey to characterize potential cold-water coral bearing areas with living colonies. Based on these maps we deployed all video-guided gear such as the OFOS-video sled, the TV grab, and the lander systems. Benthic assemblages and sedimentary structures have been documented and sampled with the OFOS and a box corer. Simultaneously, genetic samples of the living coral material were taken for additional studies. Furthermore, we have taken gravity cores to investigate the paleoceanographic conditions as well as the timing of cold-water coral colonization in the Bay of Biscay. Along with the coring efforts, a detailed sampling and study of porewater properties was performed. An additional aim of this cruise was to investigate the influence of boundary exchange processes on the Neodymium isotopy in bottom waters along the pathway of the Mediterranean Outflow water (MOW) by taking multiple samples with the CTD/Ro. The new data and samples of this METEOR cruise will provide the framework to investigate the timing of cold-water coral colonization in the Bay of Biscay, as well as its interplay with the ambient hydrography and geochemistry. This successful cruise has provided the basis to investigate the scientific aims of this expedition in great detail.