Paleotemperature and productivity reconstruction of sediment core D11957P on the Iberian Margin

Foraminifera counts and climatic assemblages from the Tore Seamount are used to approach the glacial and interglacial changes in temperature and productivity on the Iberian Margin over the last 225 kyr. Chronostratigraphy is based on Globigerinoides ruber and Globigerina bulloides oxygen isotopes and supported by foraminifera and carbonate stadial fluctuations. Foraminifera indicate cooling from late interglacial stage 5 to the beginning of Termination I (TI). Neogloboquadnna pachyderma-s reflects cold conditions during glacial stages 4-2. In contrast, glacial stage 6 is dominated by warmer N. pachyderma-d and dutertrei and a restricted arctic assemblage. Past sea surface temperatures confirm the general cooling, reaching 4.3°C (SIMMAX.28) during stage 2. Multiple productivity proxies such as organic carbon, productivity-related foraminifera, and delta13C constrain the changes observed. A productivity increase occurs after interglacial stage 5, enhanced from late glacial stage 3 to TI Present-day satellite-detected phytoplankton plumes off Portugal would have accounted in the past glacial stages for the general productivity increase over the Tore. On top of this, welldefined peaks of organic carbon and productivity-related foraminifera correspond with Heinrich events 1-4.

Distribution of desmoscolecida (Nematoda) in surface sediments of the Iberian Deep-Sea, North Atlantic (Table 1)

1. Desmoscolecida from the continental slope and the deep-sea bottom (59-4354 m) off the Portuguese and Moroccan coasts are described. 18 species were identified: Desmoscolex bathyalis sp. nov., D. chaetalatus sp. nov., D. eftus sp. nov., D. galeatus sp. nov., D. lapilliferus sp. nov., D. longisetosus Timm, 1970, D. lorenzeni sp. nov., D. perspicuus sp. nov., D. pustulatus sp. nov., Quadricoma angulocephala sp. nov., Q. brevichaeta sp. nov., Q. iberica sp. nov., Q. loricatoides sp. nov., Tricoma atlantica sp. nov., T. bathycola sp. nov., T. beata sp. nov., T. incomposita sp. nov., T. meteora sp. nov., T. mauretania sp. nov. 2. The following new terms are proposed: "Desmos" (ring-shaped concretions consisting of secretion and concretion particles), "desmoscolecoid" and "tricomoid" arrangement of the somatic setae, "regelmaessige" (regular), "unregelmaessige" (irregular), "vollstaendige" (complete) and "unvollstaendige" (incomplete) arrangement of somatic seta (variations in the desmoscolecoid arrangement of the somatic setae). The length of the somatic setae is given in the setal pattern. 3. Desmoscolecida identical as to genus and species exhibit no morphological differences even if forthcoming from different bathymetrical zones (deep sea, sublitoral, litoral) or different environments (marin, freshwater, coastal subsoil water, terrestrial environment). 4. Lorenzen's (1969) contention that thearrangement of the somatic setae is more significant for the natural relationships between the different genera of Desmoscolecida than other characteristics is further confirmed. Species with tricomoid arrangement of somatic setae are regarded as primitive, species with desmoscolecoid arrangement of somatic setae are regarded as more advanced. 5. Three new genus are established: Desmogerlachia gen. nov., Desmolorenzenia gen. nov. and Desmofimmia gen. nov. - Protricoma Timm, 1970 is synonymized with Paratricoma Gerlach, 1964 and Protodesmoscolex Timm, 1970 is synonymized with Desmoscolex Claparede,1863. 6. Checklists of all species of the order Desmoscolecida and keys to species of the subfamilies Tricominae and Desmoscolecinae are provided. 7. The following nomenclatorial changes are suggested: Desmogerlachia papillifer (Gerlach, 1956) comb. nov., D .pratensis (Lorenz, 1969) comb. nov., Desmotimmia mirabilis (Timm, 1970) comb. nov., Paratricoma squamosa (Timm, 1970) comb. nov., Desmolorenzenia crassicauda (Timm, 1970) comb. nov., D. desmoscolecoides (Timm, 1970) comb. nov., D. eurycricus (Filipjev, 1922) comb. nov., D. frontalis (Gerlach, 1952) comb. nov., D. hupferi (Steiner, 1916) comb. nov., D. longicauda (Timm, 1970) comb. nov., D. parva (Timm, 1970) comb. nov., D. platycricus (Steiner, 1916) comb. nov., D. viffata (Lorenzen, 1969) comb. nov., Desmoscolex anfarcficos (Timm, 1970) comb. nov.

Long chain diols and diol indices of surface sediments of the Iberian Atlantic margin

Long chain diols are lipids that have gained interest over the last years due to their high potential to serve as biomarkers and diol indices have been proposed to reconstruct upwelling conditions and sea surface temperature (SST). However, little is known about the sources of the diols and the mechanisms impacting their distribution. Here we studied the factors controlling diol distributions in the Iberian Atlantic margin, which is characterized by a dynamic continental shelf under the influence of upwelling of nutrient-rich cold deep waters, and fluvial input. We analyzed suspended particulate matter (SPM) of the Tagus river, marine SPM and marine surface sediments along five transects off the Iberian margin, as well as riverbank sediments and soil from the catchment area of the Tagus river. Relatively high fractional abundances of the C32 1,15-diol (normalized with respect to the 1,13- and 1,15-diols) were observed in surface sediments in front of major river mouths and this abundance correlates strongly with the BIT index, a tracer for continental input of organic carbon. Together with an even higher fractional abundance of the C32 1,15-diol in the Tagus river SPM, and the absence of long chain diols in the watershed riverbank sediments and soils, we suggest that this long chain diol is produced in-situ in the river. Further support for this hypothesis comes from the small but distinct stable carbon isotopic difference of 1.3? with the marine C28 1,13-diol. The 1,14-diols are relatively abundant in surface sediments directly along the northern part of the coast, close to the upwelling zone, suggesting that Diol Indices based on 1,14-diols would work well as upwelling tracers in this region. Strikingly, we observed a significant difference in stable carbon isotopic composition between the monounsaturated C30:1 1,14- and the saturated C28 1,14-diol (3.8±0.7 per mil), suggesting different sources, in accordance with their different distributions. In addition, the Long chain Diol Index (LDI), a proxy for sea surface temperature, was applied for the surface sediments. The results correlate well with satellite SSTs offshore but reveal a significant discrepancy with satellite-derived SSTs in front of the Tagus and Sado rivers. This suggests that river outflow might compromise the applicability of this proxy.

Physical properties of sediment cores from the Iberian Continental Slope

Climatic changes cause alterations in circulation patterns of the world oceans. The highly saline Mediterranean Outflow Water (MOW), built within the Mediterranean Sea crosses the Strait of Gibraltar in westerly directions, turning north-westward to stick to the Iberian Slope within 600-1500m water depths. Circulation pattern and current speed of the MOW are strongly influenced by climatically induced variations and thus control sedimentation processes along the South- and West - Iberian Continental Slope. Sedimentation characteristics of the investigated area are therefore suitable to reconstruct temporal hydrodynamic changes of the MOW. Detailed investigations on the silt-sized grain distribution, physical properties and hydroacoustic data were performed to recalculate paleo-current-velocities and to understand the sedimentation history in the Golf of Cadiz and the Portuguese Continental Slope. A time model based on d18Odata and 14C-datings of planktic foraminifera allowed the stratigraphical classification of the core material and thus the dating of the current induced sediment layers showing the variations of paleo-current intensities. The evaluation and interpretation of the gathered data sets enabled us to reconstruct lateral and temporal sedimentation patterns of the MOW for the Holocene and the late Pleistocene, back to the Last Glacial Maximum (LGM).

Distribution of gammaridean Amphipoda (Crustacea) in the Iberian deep sea basin (Table 2)

Four species of gammaridean Amphipoda are recorded from the Iberian deep sea basin at about 5000 m depth: Bathyceradocus iberiensis sp. n., Paracallisoma platepistomum sp. n., Parandaniexis cf. mirabilis Schellenberg, 1929, and Paragissa galatheae Barnard, 1961. The biology of the four species is discussed.

Meiofauna and the structure of the benthic community in the Iberian deep sea basin

1. On the cruises 3 and 15 of R.V. "Meteor" 6 grab samples, and 6 hauls with the 6 m Agassiztrawl were taken and at 2 stations the deep sea camera was lowered. This material gave quantitative results on the meiofauna and minimum counts of the macrofauna. 2. The nematodes constitute nearly 95% of the meiofauna, the copepoda only 2%. With increasing sediment depth the density of animals decrease gradually. In the uppermost centimeter of sediment 42.6% of the meiofauna are found while only 3.7% live in layer 6-7 cm. Meiofauna weight ranges from 0.6-5.7 mg/25 m**2 surface i.e. 0.24-2.8 g/m**2. 3. Mean numbers of individuals and weights show standard errors of 20-30 %. As an approximate average values for further considerations the weight of the meiofauna in the area was taken as 1 g/m**2 4. Quantitative information on the macrofauna is derived from the trawls and the photographs for the actinia Chitonanthus abyssorum only, which is found in the rate of 1 individual/36-72 m**2, but seems to be less abundant generally. 5. Animal density does not decrease steadily from nearshore to offshore biocoenoses, i.e. generally with increasing depth. The decrease is more pronounced for macro- than for meiofauna. For the deep sea the weight proportion of macrofauna : meiofauna is of the order of 1 : 1. 6. With the assumption, that adaptation of metabolism to deep sea conditions is similar in macro- and meiofauna total metabolism of invertebrates is ascribed to meiofauna to more than 80%. 7. The structure of the biocoenosis of the deep sea floor is characterized by the meiofauna living on and in the sediment and by the dominance of sediment feeders in the macrofauna. 8. Considering the large numbets and high partition rates of bacteria a comparative large part of the metabolism in the deep sea sediment must be ascribed to bacteria. This favours the hypothesis, that with increasing depth and decreasing addition of organic material to the sediment, the importance of meiofauna and microorganisms for total metabolism increases. 9. Considering the different modes of food transport to the deep sea environment, i.e. sinking of dead particles, transport by vertical migration of organisms, aggregation of organic particles, adsorption of dissoloved organic substance to inorganic particles, and heterotrophy, the sediment may be assumed to contain more food for invertebrates than the water above the bottom. 10. Suspensions feeders of macrofauna are fixed to hard substrates in the sediment surface. Some of them are shown to bend themselves down to the bottom in underwater photographs. This suggests the idea that some deep sea suspension feeders partly depend on food from the sediment surface, on which they feed directly.

Sea surface temperature and export productivity reconstructions of sediments off the western Iberian margin

Present day hydrographic conditions along the western Iberian margin are characterized by seasonal upwelling with filaments that can penetrate more than 200 km into the open ocean and constitute areas of cold and highly productive waters. In order to investigate spatial and temporal gradients in temperature and productivity conditions during the last 150 ky, high-resolution proxy records were generated in 3 cores (SU92-03, MD95-2040, MD95-2042), located along the Iberian coast between 43°12'N and 37°48'N and forming a N-S profile. In all cores, planktonic foraminifera census counts are used to reconstruct summer sea surface temperature (SSTsu) and export productivity (Pexpsu) using the modern analog technique SIMMAX 28. SSTsu and Pexpsu values similar to the present are observed throughout the Holocene and MIS 5e periods for each site, respectively, indicating fairly stable conditions equivalent to the modern ones. On glacial/interglacial timescales, SSTsu increases by 2-3 °C from the northern to southernmost site. Pexpsu, on the other hand, shows a decrease of 30-40 gC/m**2/yr from North to South at present time and during interglacial periods, and no significant variation (90-100 gC/m**2/yr) during glacial periods. The northernmost core SU92-03 reveals the coldest conditions with records more similar to MD95-2040 than to MD95-2042, the later of which is, as at present, more affected by subtropical waters. Core SU92-03 shows higher interglacial productivity similar to open ocean mid- to high latitude sites, while the other two cores monitor higher glacial productivity conform with other upwelling sites off NW Africa. A boundary between differences in glacial/interglacial productivity appears to be present in our study between 43°12'N and 40°35'N. Especially north of 40°N, coldest SSTsu and lowest Pexpsu are found during Heinrich events (H)1-H8 and H10-H11. In contrast, lowest Pexpsu do not coincide with these events at site MD95-2042, but appear to be related to the presence of relatively warm and nutrient-poor subtropical Eastern North Atlantic Central Water advected with the Azores Current.

Paleomegnetic and geochemistry of sediments from the early Aptian Oceanic Anoxic Event

The early Aptian Oceanic Anoxic Event (OAE1a, 120 Ma) represents a geologically brief time interval in the mid-Cretaceous greenhouse world that is characterized by increased organic carbon accumulation in marine sediments, sudden biotic changes, and abrupt carbon-isotope excursions indicative of significant perturbations to global carbon cycling. The brevity of these drastic environmental changes (< 10**6 year) and the typically 10**6 year temporal resolution of the available chronologies, however, represent a critical gap in our knowledge of OAE1a. We have conducted a high-resolution investigation of three widely distributed sections, including the Cismon APTICORE in Italy, Santa Rosa Canyon in northeastern Mexico, and Deep Sea Drilling Project (DSDP) Site 398 off the Iberian margin in the North Atlantic Ocean, which represent a range of depositional environments where condensed and moderately expanded OAE1a intervals are recorded. The objectives of this study are to establish orbital chronologies for these sections and to construct a common, high-resolution timescale for OAE1a. Spectral analyses of the closely-spaced (corresponding to ~5 to 10 kyr) measurements of calcium carbonate content of the APTICORE, magnetic susceptibility (MS) and anhysteretic remanent magnetization (ARM) of the Santa Rosa samples, and MS, ARM and ARM/IRM, where IRM is isothermal remanent magnetization, of Site 398 samples reveal statistically significant cycles. These cycles exhibit periodicity ratios and modulation patterns similar to those of the mid-Cretaceous orbital cycles, suggesting that orbital variations may have modulated depositional processes. Orbital control allows us to estimate the duration of unique, globally identifiable stages of OAE1a. Although OAE1a had a duration of ~1.0 to 1.3 Myr, the initial perturbation represented by the negative carbon-isotope excursion was rapid, lasting for ~27-44 kyr. This estimate could serve as a basis for constraining triggering mechanisms for OAE1a.