David Van Rooij

Marine litter distribution and density in European seas, from the shelves to deep basins

Anthropogenic litter is present in all marine habitats, from beaches to the most remote points in the oceans. On the seafloor, marine litter, particularly plastic, can accumulate in high densities with deleterious consequences for its inhabitants. Yet, because of the high cost involved with sampling the seafloor, no large-scale assessment of distribution patterns was available to date. Here, we present data on litter distribution and density collected during 588 video and trawl surveys across 32 sites in European waters. We found litter to be present in the deepest areas and at locations as remote from land as the Charlie-Gibbs Fracture Zone across the Mid-Atlantic Ridge. The highest litter density occurs in submarine canyons, whilst the lowest density can be found on continental shelves and on ocean ridges. Plastic was the most prevalent litter item found on the seafloor. Litter from fishing activities (derelict fishing lines and nets) was particularly common on seamounts, banks, mounds and ocean ridges. Our results highlight the extent of the problem and the need for action to prevent increasing accumulation of litter in marine environments.

Terrigenous fluxes at the Celtic margin during the last glacial cycle

The sedimentary sections of three cores from the Celtic margin provide high-resolution records of the terrigenous fluxes during the last glacial cycle. A total of 21 14 C AMS dates allow us to define age models with a resolution better than 100 yr during critical periods such as Heinrich events 1 and 2. Maximum sedimentary fluxes occurred at the Meriadzek Terrace site during the Last Glacial Maximum (LGM). Detailed X-ray imagery of core MD95-2002 from the Meriadzek Terrace shows no sedimentary structures suggestive of either deposition from high-density turbidity currents or significant erosion. Two paroxysmal terrigenous flux episodes have been identified. The first occurred after the deposition of Heinrich event 2 Canadian ice-rafted debris (IRD) and includes IRD from European sources. We suggest that the second represents an episode of deposition from turbid plumes, which precedes IRD deposition associated with Heinrich event 1. At the end of marine isotopic stage 2 (MIS 2) and the beginning of MIS 1 the highest fluxes are recorded on the Whittard Ridge where they correspond to deposition from turbidity current overflows. Canadian icebergs have rafted debris at the Celtic margin during Heinrich events 1, 2, 4 and 5. The highresolution records of Heinrich events 1 and 2 show that in both cases the arrival of the Canadian icebergs was preceded by a European ice rafting precursor event, which took place about 1^1.5 kyr before. Two rafting episodes of European IRD also occurred immediately after Heinrich event 2 and just before Heinrich event 1. The terrigenous fluxes recorded in core MD95-2002 during the LGM are the highest reported at hemipelagic sites from the northwestern European margin. The magnitude of the Canadian IRD fluxes at Meriadzek Terrace is similar to those from oceanic sites. = 2002 Elsevier Science B.V. All rights reserved.

Northeastern Atlantic cold-water coral reefs and climate

U-series age patterns obtained on reef framework-forming cold-water corals collected over a nearly 6000-km-long continental margin sector, extending from off Mauritania (17 degrees N; northwest Africa) to the southwestern Barents Sea (70 degrees N; northeastern Europe), reveal strong climate influences on the geographical distribution and sustained development of these ecosystems. Over the past three glacial-interglacial cycles, framework-forming cold-water corals (Lophelia pertusa and Madrepora oculata) seem to have predominantly populated reefs, canyons, and patches in the temperate East Atlantic and the Mediterranean Sea. Above 50 degrees N corals colonize reefs in the northern East Atlantic primarily during warm climate periods with the biogeographic limit advancing from similar to 50 degrees N to similar to 70 degrees N. We propose that north-south oscillations of the biogeographic limit of reef developments are paced by ice ages and may occur synchronously with north-south displacement of cold nutrient-rich intermediate waters and surface productivity related to changes of the polar front.

Deep-water corals of the northeastern Atlantic margin: carbonate mound evolution and upper intermediate water ventilation during the Holocene

We present combined 230Th/U and 14C dating on deep-water corals from the northeastern North Atlantic in order to investigate coral growth and sedimentation on carbonate mounds, as well as past changes of intermediate water ventilation. Within European projects GEOMOUND and ECOMOUND reef forming Lophelia pertusa deep-water corals were raised from intermediate depth (∼610 to 888 m bsl) from top of carbonate mounds at southeast Rockall Bank and at Porcupine Seabight. XRD analyses, δ234U, and 230Th/232Th indicate negligible alteration of the investigated corals, i.e. open system U-series behavior. 230Th/U ages from coral specimens of the uppermost coral sequence of the investigated mounds range from today to 10,950 CAL yr BP, i.e. coral growth during the Holocene. A modern Lophelia gave a 230Th/U age of 1983±6 AD, close to the date of collection in 2001 AD. Deep-water coral growth is the driving process of sediment accumulation on the summit of carbonate mounds, with sediment accumulation rates in the order of ∼0.3 mm yr−1. However, coral growth is discontinuous and irregular, and complete coral sequences are frequently altered (dissolved) likely due to organic matter consumption by oxidizing pore fluids. Mound top sediments indicate the presence of corals over several glacial/interglacial cycles, but corals of glacial origin could not be identified on the investigated mounds.

Integrated stratigraphy and palaeoecology of the Lower and Middle Miocene of the Porcupine Basin

A high-resolution palynological analysis and a detailed palaeomagnetic study of a marine sequence recovered during IODP Expedition Leg 307 in the Porcupine Basin southwest of Ireland provide new insights into the regional depositional history and palaeoenvironmental evolution during Early Neogene times. The Hole 1318B studied was drilled on the upper slope of the continental margin in a water depth of 409 m, upslope from a province of carbonate mounds (the Belgica mound province). The diverse and well-preserved dinoflagellate cyst associations consist typically of deep neritic and oceanic species, mixed with a neritic component transported from the shelf, reflecting the deep depositional setting at the continental margin. The palaeomagnetic record together with the ranges of key dinoflagellate cyst species constrain the age of the studied sequence between 16.7 Ma and 12.01 Ma, that is, between the late Burdigalian and late Serravallian. The distinct unconformity terminating the Miocene sequence correlates to the global sequence boundary Ser4/Tor1 dated at 10.5 Ma, and represents, according to previous extensive seismic studies, a basin-wide erosional event. The overlying sediments are of Middle Pleistocene or younger age. Downslope from IODP Site 1318, carbonate mounds root on the erosional surface. The dinoflagellate cyst associations from the Porcupine Basin distinctly mirror the global cooling phase following the Middle Miocene Climatic Optimum. Cooling phase Mi3, a short-lived glaciation, is particularly well expressed and here dated at 13.6 Ma. The palynomorph record furthermore indicates a reduction of the productivity and an increase of oceanic oligotrophic species after 14 Ma, suggesting a reduction or perhaps even a shutdown of the upwelling.

First sighting of active fluid venting in the Gulf of Cadiz

The Mercator mud volcano, located in the Gulf of Cadiz off the coasts of Spain, Portugal, and Morocco (Figure 1), may provide an accessible field laboratory for studying local active venting and its possible internal and external controls. The recent discovery of the first active deep ocean ‘brown smoker’ chimney in this area can possibly be linked with the disintegration of a gas hydrate layer between the seafloor and a subsurface level that is dependent on pressure and temperature. For more than a decade, the international marine scientific community has deployed considerable efforts in exploring the Gulf of Cadiz. Since the discovery of the Gulfs first mud volcano in 1999, research cruises have steadily unveiled one mud volcano after another [Gardner, 2001; Pinheiro et al., 2003; Somoza et al., 2003]. These mud volcanoes are clustered in several fields on the Portuguese, Spanish, and Moroccan margins (Figure 1). Extensive geophysical evidence of shallow gas and subsurface fluid flow has been reported in the Gulf of Cadiz [Baraza and Ercilla 1996; Pinheiro et al., 2003].

Habitat Mapping of a Cold-Water Coral Mound on Pen Duick Escarpment (Gulf of Cadiz)

Publisher Summary The Pen Duick Escarpment is a 6 km long, NW-SE oriented, 80–125 m high escarpment with a southwest-facing slope of 8–12°. It is located within the El Arraiche mud volcano field on the Moroccan continental margin (southern Gulf of Cadiz) in water depths of 550–650 m. This chapter provides acase study about habitat mapping of cold-water coral mound, Beta Mound, using a multibeam echosounder, ROV observations, and boxcore sampling. This habitat mapping revealed the presence of four different habitats: soft (bioturbated) sediment, soft sediment with patchy coral rubble, dense cold-water coral rubble fields, and rock slabs. All cold-water corals are dead except for one living Dendrophyllia cornigera . The coral rubble consists mainly of dead Dendrophyllia , Lophelia pertusa , and Madrepora oculata . On top of the coral rubble, numerous crinoids were observed, while the soft sediment is mostly colonized by several species of soft corals. Sponges, squat lobsters, echinoids, and holothurians were also observed. Cold-water corals provide hard-bottom substrate, refuge, and nursery for a large variety of species and are therefore considered important biodiversity hotspots. On Beta Mound, several invertebrate and fish species are living in the three-dimensional framework formed by the dead cold-water coral rubble. The megafauna of the coral rubble patches or fields is dominated by crinoids (Echinodermata, Crinoidea), which cover most of the surface of the rubble. Poriferans and crustaceans such as squat lobsters (Decapoda, Galatheidae) are also commonly found on the coral rubble areas. The fish Helicolenus dactylopterus was found in all the four habitats.

South Atlantic intermediate water advances into the North‐east Atlantic with reduced Atlantic meridional overturning circulation during the last glacial period

The Nd isotopic composition (eNd) of seawater and cold-water coral (CWC) samples from the Gulf of Cadiz and the Alboran Sea, at a depth of 280–827 m were investigated in order to constrain middepth water mass dynamics within the Gulf of Cadiz over the past 40 ka. eNd of glacial and Holocene CWC from the Alboran Sea and the northern Gulf of Cadiz reveals relatively constant values (−8.6 to −9.0 and −9.5 to −10.4, respectively). Such values are similar to those of the surrounding present-day middepth waters from the Mediterranean Outflow Water (MOW; eNd ∼ −9.4) and Mediterranean Sea Water (MSW; eNd ∼ −9.9). In contrast, glacial eNd values for CWC collected at thermocline depth (550–827 m) in the southern Gulf of Cadiz display a higher average value (−8.9 ± 0.4) compared to the present-day value (−11.7 ± 0.3). This implies a higher relative contribution of water masses of Mediterranean (MSW) or South Atlantic origin (East Antarctic Intermediate Water, EAAIW). Our study has produced the first evidence of significant radiogenic eNd values (∼ −8) at 19, 23–24, and 27 ka, which are coeval with increasing iceberg discharges and a weakening of Atlantic Meridional Overturning Circulation (AMOC). Since MOW eNd values remained stable during the last glacial period, it is suggested that these radiogenic eNd values most likely reflect an enhanced northward propagation of glacial EAAIW into the eastern Atlantic Basin.