Biomass and stable isotope composition of plankton in five size fractions along a zonal transect (24°N) from the Canary Islands to Florida in January-March 2011

The spatial variability of biomass and stable isotopes in plankton size fractions in the upper 200 m was studied in a high spatial resolution transect along 24°N from Canary Islands to Florida (January - March 2011) during Leg 8 of the Malaspina-2010 expedition (http://www.expedicionmalaspina.es) to determine nitrogen and carbon sources. Plankton samples were collected by vertical tows of a microplankton net (40 mm mesh size) and a mesoplankton net (200 mm mesh size) through the upper 200 m of the water column. Sampling was between 10:00 and 16:00 h GMT. Plankton was separated into five size fractions (40 - 200, 200 - 500, 500 - 1000, 1000 - 2000 and > 2000 mm) by gentle filtration of the samples by a graded series of nylon sieves (2000, 1000, 500, 200 and 40 mm). Large gelatinous organisms were removed before filtration. Aliquots for each size fraction were collected on pre-weighed glass-fibre filters, dried (60°C, 48 h) and stored in a desiccator before determination of biomass (dry weight), carbon and nitrogen content and natural abundance of stable carbon and nitrogen isotopes ashore. Vertical advection of waters predominated in lateral zones while the central Atlantic (30-70°W) was characterized by a strong stratification and oligotrophic surface waters. Plankton biomass was low in the central zone and high in both eastern and western sides, with most of the variability due to either large (>2000 µm) and small plankton (<500 µm). Carbon isotopes reflected mainly the advection the deep water in lateral zones. Stable nitrogen isotopes showed a nearly symmetrical spatial distribution in all fractions, with the lowest values (delta15N <1per mill) in the central zone, and were inversely correlated to carbon stable isotopes (delta13C) and to the abundance of the nitrogen-fixer Trichodesmium. Diazotrophy was estimated to account for >50% of organic nitrogen in the central zone, and even >30% in eastern and western zones. The impact of diazotrophy increased with the size of the organisms, supporting the wide participation of all trophic levels in the processing of recently fixed nitrogen. These results indicate that atmospheric sources of carbon and nitrogen prevail over deep water sources in the subtropical North Atlantic and that the zone influenced by diazotrophy is much larger than reported in previous studies.

Distribution of deep-sea foraminifera in surface sediments east of New Zealand

Paleobathymetric assessments of fossil foraminiferal faunas play a significant role in the analysis of the paleogeographic, sedimentary, and tectonic histories of New Zealand's Neogene marine sedimentary basins. At depths >100 m, these assessments often have large uncertainties. This study, aimed at improving the precision of paleodepth assessments, documents the present-day distribution of deep-sea foraminifera (>63 µm) in 66 samples of seafloor sediment at 90-700 m water depth (outer shelf to mid-abyssal), east of New Zealand. One hundred and thirty-nine of the 465 recorded species of benthic foraminifera are new records for the New Zealand region. Characters of the foraminiferal faunas which appear to provide the most useful information for estimating paleobathymetry are, in decreasing order of reliability: relative abundance of common benthic species; benthic species associations; upper depth limits of key benthic species; and relative abundance of planktic foraminifera. R mode cluster analysis on the quantitative census data of the 58 most abundant species of benthic foraminifera produced six species associations within three higher level clusters: (1) calcareous species most abundant at mid-bathyal to outer shelf depths (<1000 m); (2) calcareous species most abundant at mid-bathyal and greater depths (>600 m); (3) agglutinated species mostly occurring at deep abyssal depths (>3000 m). A detrended correspondence analysis ordination plot exhibits a strong relationship between these species associations and bathymetry. This is manifest in the bathymetric ranges of the relative abundance peaks of many of the common benthic species (e.g., Abditodentrix pseudothalmanni 500-2800 m, Bolivina robusta 200-650 m, Bulimina marginata f. marginata 20-600 m, B. marginata f. aculeata 400-3000 m, Cassidulina norvangi 1000-4500 m, Epistominella exigua 1000-4700 m, and Trifarina angulosa 10-650 m), which should prove useful in paleobathymetric estimates. The upper depth limits of 28 benthic foraminiferal species (e.g., Fursenkoina complanata 200 m, Bulimina truncana 450 m, Melonis affinis 550 m, Eggerella bradyi 750 m, and Cassidulina norvangi 1000 m) have potential to improve the precision of paleobathymetric estimates based initially on the total faunal composition. The planktic percentage of foraminiferal tests increases from outer shelf to upper abyssal depths followed by a rapid decline within the foraminiferal lysocline (below c. 3600 m). A planktic percentage <50% is suggestive of shelf depths, and >50% is suggestive of bathyal or abyssal depths above the CCD. In the abyssal zone there is dramatic taphonomic loss of most agglutinated tests (except some textulariids) at burial depths of 0.1-0.2 m, which negates the potential usefulness of these taxa in paleobathymetric assessments.

Re-OS and Pb isotope ratios of sediments from Saanich Inlet, Western Canada

Re-Os and Pb-Pb isotopic analysis of reduced varved sediments cored in the deeper basin of Saanich Inlet (B.C.) are presented. From core top to 61 cm down-core, spanning approximately the last 100 yrs of sedimentation, 187Os/188Os ratio and Os concentration respectively increase from ~0.8 to ~0.9 and from 55 to 60 ppt, whereas Re concentration decreases from 3600 to 2600 ppt. Re correlates with Corg (R2=0.6) throughout the entire section, whereas Os follows Re and Corg trends deeper down-core, suggesting a decoupling of a Re- and Os-geochemistry during burial and/or very early diagenesis. No systematic compositional differences are observed between seasonal laminae. 204Pb-normalized lead isotope ratios increase from sediment surface down to 7 cm down-core, then decrease steadily to pre-industrial levels at ~50 cm down-core. This pattern illustrates the contamination from leaded gasoline until the recent past. The measured Pb isotopic ratios point primarily toward gasoline related atmospheric lead from the USA. The osmium isotopic values measured are significantly lower than those of modern seawater-Os. In comparison with other anoxic environments, the osmium content of Saanich Inlet sediments is low, and its Os isotopic composition suggests significant inputs from unradiogenic sources (detrital and/or dissolved). Ultramafic lithologies in the watershed of the Fraser River are suspected to contribute to sedimentary inputs as well as to the input of dissolved unradiogenic osmium in the water of Saanich Inlet. The presence of some unradiogenic Os from anthropogenic contamination cannot be discounted near the core top, but since deeper, pre-anthropogenic levels also yielded unradiogenic Os results, one is led to conclude that the overall low 187Os/188Os ratios result from natural geochemical processes. Thus, the bulk sediment of Saanich Inlet does not appear to record 187Os/188Os composition of the marine end-member of the only slightly below normal salinity, fjord water. The low seawater-derived Os content of the sediment, coupled with unradiogenic Os inputs from local sources, explains the overall low isotopic values observed. As a consequence, such near-shore anoxic sediments are unlikely to record changes in the past ocean Os isotopic composition.

Quaternary radiolarian counts from Site 181-1123

In the present work Quaternary radiolarian assemblages from the Southwest Pacific were investigated due to their importance for correlation and identification of climatic changes. The studied Ocean Drilling Program (ODP) Site 1123 (Leg 181) is situated on the northern flanks of the Chatham Rise, 1100 kilometres offshore eastern New Zealand and in a water depth o f 3290 metres. It is situated just north of the Subtropical Convergence (STC) in temperate climatic conditions, influenced by the cold deep Deep Western Boundary Current (DWBC) and by the subtropical East Cape Current (ECC) in shallow water depths. A continuous record of 79 sediment samples from this site with a temporal resolution of ~15,000 years provided a medium-resolution record of radiolarian assemblages through the Quaternary. This allowed investigations on how radiolarian assemblages are influenced by climatic variations at obliquity and eccentricity bandwidth, with periodic variations of 40,000, 100,000 and 400,000 years, respectively. Emphasis was given to changes in radiolarian assemblages through the Mid-Pleistocene climate transition (MPT) that marks a fundamental reorganisation in Earth's climate system by change from 40,000 to 100,000 year cycles. Glacial and interglacial variations in oceanography were investigated. Especially the influence of the DWBC was examined due to its input of deep and cold waters to the Pacific Ocean, which plays an important role in Earth's climate system. 167 radiolarian counting groups were examined concerning variations in radiolarian abundance, preservation, diversity, the relative abundance of orders, families, and selected species in order to detect influences of past climatic variations in the Southwest Pacific. No significant changes in radiolarian assemblages were found in coincidence with the onset of the MPT. Investigations led to the recognition of four characteristic phases within the last 1.2 million years. Within one of these phases (Phase Ill), about 160,000 years after the onset of the MPT, fundamental changes in radiolarian assemblages occurred. Investigations yielded highest diversity and highest numbers of nassellarians in abundant samples, whereas sparse samples were mostly poorly preserved and were dominated by spumellarians. Abundance of certain radiolarian families in interglacials or glacials indicated their usefulness as indicators for climatic conditions at Site 1123. Trends o f selected taxa within these families supported the significance of warm- or cool-water preference of these families. Use of 67 radiolarian species as climate indicators showed abundance of warm-water assemblages within interglacials, whereas abundance of cool-water species was increased within glacials. Depth distributional patterns of 52 radiolarian species indicated a strong influence of shallow waters, possibly the EEC, within interglacials and increased influence of deep and intermediate waters, possibly of southern-sourced character and the DWBC in glacial stages.

Sediment geochemistry and water trace metal concentration in Potter Cove

Recent rapid climate warming at the western Antarctic Peninsula (WAP) results in elevated glacial melting, enhanced sedimentary run-off, increased turbidity and impact of ice-scouring in shallow coastal areas. Discharge of mineral suspension from volcanic bedrock ablation and chronic physical disturbance is expected to influence sessile filter feeders such as the Antarctic soft shell clam Laternula elliptica ( King and Broderip, 1832). We investigated effects of sedimentary run-off on the accumulation of trace metals, and together with physical disturbance, the cumulative effect on oxidative stress parameters in younger and older L. elliptica from two stations in Potter Cove (King George Island, Antarctica) which are distinctly impacted by turbidity and ice-scouring. Fe, Mn, Sr, V and Zn concentrations were slightly higher in sediments of the station receiving more sediment run-off, but not enriched in bivalves of this station. The only element that increased in bivalves experimentally exposed to sediment suspension for 28 days was Mn. Concentration of the waste accumulation biomarker lipofuscin in nervous tissue was higher in L. elliptica from the "exposed" compared to the "less exposed" site, whereas protein carbonyl levels in bivalve mantle tissue were higher at the less sediment impacted site. Tissue metal content and lipofuscin in nervous tissue were generally higher in older compared to younger individuals from both field stations. We conclude that elevated sediment ablation does not per se result in higher metal accumulation in L. elliptica. Instead of direct absorbance from sediment particles, metal accumulation in gills seems to indicate uptake of compounds dissolved in the water column, whereas metals in digestive gland appear to originate from enriched planktonic or detritic food. Accumulation of cellular waste products and potentially reactive metals over lifetime presumably alters L. elliptica physiological performance with age and may contribute to higher stress susceptibility in older animals.

Physical properties and geochemical pore-water analysis of sediment core GeoB16423-1

Several studies indicate that the 2011 Tohoku-Oki earthquake (Mw 9.0) off the Pacific coast of Japan has induced slip to the trench and triggered landslides in the Japan Trench. In order to better understand these processes, detailed mapping and shallow-coring landslides at the trench as well as Integrated Ocean Drilling Program (IODP) deep drilling to recover the plate boundary décollement (Japan Trench Fast Earthquake Drilling Project, JFAST) have been conducted. In this study we report sediment core data from the rapid response R/V SONNE cruise (SO219A) to the Japan Trench, evidencing a Mass Transport Deposit (MTD) in the uppermost section later drilled at this JFAST-site during IODP Expedition 343. A 8.7 m long gravity core (GeoB16423-1) recovered from ~7,000 m water depth reveals a 8 m sequence of semi-consolidated mud clast breccias embedded in a distorted chaotic sediment matrix. The MTD is covered by a thin veneer of 50 cm hemipelagic, bioturbated diatomaceous mud. This stratigraphic boundary can be clearly distinguished by using physical properties data from Multi Sensor Core Logging and from fall-cone penetrometer shear strength measurements. The geochemical analysis of the pore-water shows undisturbed linear profiles measured from the seafloor downcore across the stratigraphic contact between overlying younger background-sediment and MTD below. This indicates that the investigated section has not been affected by a recent sediment destabilization in the course of the giant Tohoku-Oki earthquake event. Instead, we report an older landslide which occurred between 700 and 10,000 years ago, implying that submarine mass movements are dominant processes along the Japan Trench. However, they occur on local sites and not during each megathrust earthquake.

Multibeam and seismic survey, physical oceanography, and sea-bottom videos from the Bay of Biscay

We report the northernmost and deepest known occurrence of deep-water pycnodontine oysters, based on two surveys along the French Atlantic continental margin to the La Chapelle continental slope (2006) and the Guilvinec Canyon (2008). The combined use of multibeam bathymetry, seismic profiling, CTD casts and a remotely operated vehicle (ROV) made it possible to describe the physical habitat and to assess the oceanographic control for the recently described species Neopycnodonte zibrowii. These oysters have been observed in vivo in depths from 540 to 846 m, colonizing overhanging banks or escarpments protruding from steep canyon flanks. Especially in the Bay of Biscay, such physical habitats may only be observed within canyons, where they are created by both long-term turbiditic and contouritic processes. Frequent observations of sand ripples on the seabed indicate the presence of a steady, but enhanced bottom current of about 40 cm/s. The occurrence of oysters also coincides with the interface between the Eastern North Atlantic Water and the Mediterranean Outflow Water. A combination of this water mass mixing, internal tide generation and a strong primary surface productivity may generate an enhanced nutrient flux, which is funnelled through the canyon. When the ideal environmental conditions are met, up to 100 individuals per m² may be observed. These deep-water oysters require a vertical habitat, which is often incompatible with the requirements of other sessile organisms, and are only sparsely distributed along the continental margins. The discovery of these giant oyster banks illustrates the rich biodiversity of deep-sea canyons and their underestimation as true ecosystem hotspots.

Radium concentration in water samples from the Northeast Atlantic

We present field measurements of air-sea gas exchange by the radon deficit method that were carried out during JASIN 1978 (NE Atlantic) and FGGE 1979 (Equatorial Atlantic). Both experiments comprised repeated deficit measurements at fixed position over periods of days or longer, using a previously descibed precise and fast-acquiaition, automatic radon measuring system. The deficit time series exhibit variations that only partly reflect the expected changes in gas transfer. By evaluating averages over each time series we deduce the following gas transfer velocities (average wind velocity and water temperature in parentheses): JASIN phase 1: 1.6 ± 0.8 m/d (at ~6 m/s, 13°C) JASIN phase 2: 4.3 ± 1.2 m/d (at ~8 m/s, 13°C) FGGE: 1.2 ± 0.4 m/d (at ~5 m/s, 28°C) 0.9 ± 0.4 m/d (at ~7 m/s, 28°C) 1.5 ± 0.4 m/d (at ~7 m/s, 28°C) The large difference betwen the JASIN phase 2 and FGGE values despite quite similare average wind velocity becomes even larger when the values are, however, fully compatible with the range of gas transfer velocities observed in laboratory experiments and the conclusion is suggested that their difference is caused by the highly different wind variability in JASIN and FGGE. We conclude that in gas exchange parameterization it is not sufficinent to consider wind velocity only. A comparison of our observations with laboratory results outlines the range of variations of air-sea gas transfer velocities with wind velocity and sea state. We also reformulate the radon deficit method, in the light of our observed deficit variations, to account explicitely for non-stationary and horizontal inhomogeneity in previous radon work introduces considerable uncertainty in deduced gas transfere velocity. We furthermore discuss the observational rewuirements that have to be met for an adequate exploitation of the radon deficit method, of which an observation area of minimum horizontal inhomogeneity and monitoring of the remaining inhomogeneities are thought to be the most stringent ones.

High-resolution sedimentological and paleontological record of ODP Site 167-1019

Holocene and latest Pleistocene oceanographic conditions and the coastal climate of northern California have varied greatly, based upon high-resolution studies (ca. every 100 years) of diatoms, alkenones, pollen, CaCO3%, and total organic carbon at Ocean Drilling Program (ODP) Site 1019 (41.682°N, 124.930°W, 980 m water depth). Marine climate proxies (alkenone sea surface temperatures [SSTs] and CaCO3%) behaved remarkably like the Greenland Ice Sheet Project (GISP)-2 oxygen isotope record during the Bølling-Allerod, Younger Dryas (YD), and early part of the Holocene. During the YD, alkenone SSTs decreased by >3°C below mean Bølling-Allerod and Holocene SSTs. The early Holocene (ca. 11.6 to 8.2 ka) was a time of generally warm conditions and moderate CaCO3 content (generally >4%). The middle part of the Holocene (ca. 8.2 to 3.2 ka) was marked by alkenone SSTs that were consistently 1-2°C cooler than either the earlier or later parts of the Holocene, by greatly reduced numbers of the gyre-diatom Pseudoeunotia doliolus (<10%), and by a permanent drop in CaCO3% to <3%. Starting at ca. 5.2 ka, coastal redwood and alder began a steady rise, arguing for increasing effective moisture and the development of the north coast temperate rain forest. At ca. 3.2 ka, a permanent ca. 1°C increase in alkenone SST and a threefold increase in P. doliolus signaled a warming of fall and winter SSTs. Intensified (higher amplitude and more frequent) cycles of pine pollen alternating with increased alder and redwood pollen are evidence that rapid changes in effective moisture and seasonal temperature (enhanced El Niño-Southern Oscillation [ENSO] cycles) have characterized the Site 1019 record since about 3.5 ka.

Plankton abundances in water samples of cruise EBENE

The Etude du Broutage en Zone Equatoriale (EBENE) transect (8°S-8°N) explored the equatorial high-nutrient, low-chlorophyll (HNLC) zone and adjacent oligotrophic areas during a La Niña period (October-November 1996). During this time the passage of a tropical instability wave also influenced the region north of the equator. We present a brief summary of EBENE findings, with an emphasis on phytoplankton utilization by the assemblage of protistan and animal consumers. Despite significant variability over the diel cycle, phytoplankton biomass at the equator was relatively constant on a 24-hour timescale, denoting a dynamic balance between growth and losses. The magnitude of the daily cycle in phytoplankton biomass was well constrained by in situ observations of the diel variability in pigments and suspended particulates, by 14C uptake rates from in situ incubations, and from experimental determinations of specific growth and grazing rates. The general equilibrium of production and grazing processes is illustrated by applying biomass-specific grazing rates from the equatorial station to measured planktonic biomass along the EBENE transect and comparing them to measured 14C uptake. Most of the grazing turnover is supported by the production of Prochloroccus (31%) and picoeukaryotic algae (34%). Among the consumers, microzooplankton (<200 µm) account for 59-98% of the grazing losses. The coherence of the results obtained by independent methods suggests that the essential features of the system have been adequately represented by rate and standing stock assessments from the EBENE study.