Miocene planktonic foraminifera of ODP Hole 130-806B

We document the waxing and waning of a "proto-warm pool" in the western equatorial Pacific (WEP) based on a study of multi-species planktic foraminiferal isotope ratios and census data spanning the 13.2-5.8 Ma interval at ODP Site 806. We hypothesize that the presence or absence of a proto-warm pool in the WEP, caused by the progressive tectonic constriction of the Indonesian Seaway and modulated by sea level fluctuations, created El Niño/La Niña-like alternations of hydrographic conditions across the equatorial Pacific during the late Miocene. This hypothesis is supported by the general antithetical relationship observed between carbonate productivity and preservation in the western and eastern equatorial Pacific, which we propose is caused by these alternating ocean-climate states. Warming of thermocline and surface waters, as well as a major change in planktic foraminferal assemblages record a two-step phase of proto-warm pool development ~11.6-10 Ma, which coincides with Miocene isotope events Mi5 and Mi6, and sea-level low stands. We suggest that these changes in the biota and structure of the upper water column in the WEP mark the initiation of a more modern equatorial current system, including the development of the Equatorial Undercurrent (EUC), as La Niña-like conditions became established across the tropical Pacific. This situation sustained carbonate and silica productivity in the eastern equatorial Pacific (EEP) at a time when carbonate preservation sharply declined in the Caribbean. Proto-warm pool weakening after ~10 Ma may have contributed to the nadir of a similar "carbonate crash" in the EEP. Cooling of the thermocline and increased abundances of thermocline taxa herald the decay of the proto-warm pool and higher productivity in the WEP, particularly ~ 9.0-8.8 Ma coincident with a major perturbation in tropical nannofossil assemblages. We suggest that this interval of increased productivity records El Niño-like conditions across the tropical Pacific and the initial phase of the widespread "biogenic bloom". Resurgence of a later proto-warm pool in the WEP ~6.5-6.1 Ma may have spurred renewed La Niña-like conditions, which contributed to a strong late phase of the "biogenic bloom" in the EEP.

Hexachlorocyclohexanes concentration in air and ocean water

Hexachlorocyclohexanes (HCHs) are ubiquitous organic pollutants derived from pesticide application. They are subject to long-range transport, persistent in the environment, and capable of accumulation in biota. Shipboard measurements of HCH isomers (a-, b- and g-HCH) in surface seawater and boundary layer atmospheric samples were conducted in the Atlantic and the Southern Ocean in October to December of 2008. SumHCHs concentrations (the sum of a-, g- and b-HCH) in the lower atmosphere ranged from 12 to 37 pg/m**3 (mean: 27 ± 11 pg/m**3) in the Northern Hemisphere (NH), and from 1.5 to 4.0 pg/m**3 (mean: 2.8 ± 1.1 pg/m**3) in the Southern Hemisphere (SH), respectively. Water concentrations were: a-HCH 0.33-47 pg/l, g-HCH 0.02-33 pg/l and b-HCH 0.11-9.5 pg/l. Dissolved HCH concentrations decreased from the North Atlantic to the Southern Ocean, indicating historical use of HCHs in the NH. Spatial distribution showed increasing concentrations from the equator towards North and South latitudes illustrating the concept of cold trapping in high latitudes and less interhemispheric mixing process. In comparison to concentrations measured in 1987-1999/2000, gaseous HCHs were slightly lower, while dissolved HCHs decreased by factor of 2-3 orders of magnitude. Air-water exchange gradients suggested net deposition for a-HCH (mean: 3800 pg/m**2/day) and g-HCH (mean: 2000 pg/m**2/day), whereas b-HCH varied between equilibrium (volatilization: <0-12 pg/m**2/day) and net deposition (range: 6-690 pg/m**2/day). Climate change may significantly accelerate the release of "old" HCHs from continental storage (e.g. soil, vegetation and high mountains) and drive long-range transport from sources to deposition in the open oceans. Biological productivities may interfere with the air-water exchange process as well. Consequently, further investigation is necessary to elucidate the long term trends and the biogeochemical turnover of HCHs in the oceanic environment.

Pigment concentrations in surface sediments of the Arabian Sea

As part of the large-scale, interdisciplinary deep-sea study "BIGSET", the relationship between the monsoon-induced regional and temporal variability of POC deposition and the small-sized benthic community was investigated at several sites 2316-4420 m deep in the Arabian Sea during four cruises between 1995 and 1998. Vertical and horizontal distribution patterns of chloroplastic pigments (a measure of phytodetritus deposition), readily soluble protein and activity, and biomass parameters of the small-sized benthic community (Electron Transport System Activity (ETSA); bacterial ectoenzymatic activity (FDA turnover) and DNA concentrations) were measured concurrently with the vertical fluxes of POC and chloroplastic pigments. Sediment chlorophyll a (chl. a) profiles were used to calculate chl. a flux rates and to estimate POC flux across the sediment water interface using two different transport reaction models. These estimates were compared with corresponding flux rates determined in sediment traps. Regional variability of primary productivity and POC deposition at the deep-sea floor creates a trophic gradient in the Arabian Basin from the NW to the SE, which is primarily related to the activity of monsoon winds and processes associated with the topography of the Arabian Basin and the vicinity of land masses. Inventories of sediment chloroplastic pigments closely corresponded to this trophic gradient. For ETSA, FDA and DNA, however, no clear coupling was found, although stations WAST (western Arabian Sea) and NAST (northern Arabian Sea) were characterised by high concentrations and activities. These parameters exhibited high spatial and temporal variability, making it impossible to recognise clear mechanisms controlling temporal and spatial community patterns of the small-sized benthic biota. Nevertheless, the entire Arabian Basin was recognised as being affected by monsoonal activity. Comparison of two different transport reaction models indicates that labile chl. a buried in deeper sediment layers may escape rapid degradation in Arabian deep-sea sediments.

Mesozooplankton community development at elevated CO2

The increasing CO2 concentration in the atmosphere caused by burning fossil fuels leads to increasing pCO2 and decreasing pH in the world ocean. These changes may have severe consequences for marine biota, especially in cold-water ecosystems due to higher solubility of CO2. However, studies on the response of mesozooplankton communities to elevated CO2 are still lacking. In order to test whether abundance and taxonomic composition change with pCO2, we have sampled nine mesocosms, which were deployed in Kongsfjorden, an Arctic fjord at Svalbard, and were adjusted to eight CO2 concentrations, initially ranging from 185 µatm to 1420 µatm. Vertical net hauls were taken weekly over about one month with an Apstein net (55 µm mesh size) in all mesocosms and the surrounding fjord. In addition, sediment trap samples, taken every second day in the mesocosms, were analysed to account for losses due to vertical migration and mortality. The taxonomic analysis revealed that meroplanktonic larvae (Cirripedia, Polychaeta, Bivalvia, Gastropoda, and Decapoda) dominated in the mesocosms while copepods (Calanus spp., Oithona similis, Acartia longiremis and Microsetella norvegica) were found in lower abundances. In the fjord copepods prevailed for most of our study. With time, abundance and taxonomic composition developed similarly in all mesocosms and the pCO2 had no significant effect on the overall community structure. Also, we did not find significant relationships between the pCO2 level and the abundance of single taxa. Changes in heterogeneous communities are, however, difficult to detect, and the exposure to elevated pCO2 was relatively short. We therefore suggest that future mesocosm experiments should be run for longer periods.

Radiocarbon age, and sedimentation and accumulation rate of core JM05-G001 obtained during Jan Mayen cruise JM050704 to the Barents Sea

Instrumental monitoring of the climate at high northern latitudes has documented the ongoing warming of the last few decades. Climate modelling has also demonstrated that the global warming signal will be amplified in the polar region. Such temperature increases would have important implications on the ecosystem and biota of the Barents Sea. This study therefore aims to reconstruct the climatic changes of the Barents Sea based on benthic foraminifera over approximately the last 1400 years at the decadal to sub-decadal scale. Oxygen and carbon isotope analysis and benthic foraminiferal species counts indicate an overall warming trend of approximately 2.6°C through the 1400-year record. In addition, the well-documented cooling period equating to the 'Little Ice Age' is evident between c. 1650 and 1850. Most notably, a series of highly fluctuating temperatures are observed over the last century. An increase of 1.5°C is shown across this period. Thus for the first time we are able to demonstrate that the recent Arctic warming is also reflected in the oceanic micro-fauna.

Stable isotopes and element concentrations of samples from the Wadi Bih, United Arab Emirates

Ocean acidification triggered by Siberian Trap volcanism was a possible kill mechanism for the Permo-Triassic Boundary mass extinction, but direct evidence for an acidification event is lacking. We present a high-resolution seawater pH record across this interval, using boron isotope data combined with a quantitative modeling approach. In the latest Permian, increased ocean alkalinity primed the Earth system with a low level of atmospheric CO2 and a high ocean buffering capacity. The first phase of extinction was coincident with a slow injection of carbon into the atmosphere, and ocean pH remained stable. During the second extinction pulse, however, a rapid and large injection of carbon caused an abrupt acidification event that drove the preferential loss of heavily calcified marine biota.

Calcareous nannofossil abundance and datum events of ODP Holes 181-1123C and 181-1124C, southwest Pacific

Seven sites were drilled off the eastern shore of New Zealand during Ocean Drilling Program Leg 181 to gain knowledge of southwest Pacific ocean history, in particular, the evolution of the Pacific Deep Western Boundary Current (DWBC). Holes 1123C and 1124C penetrated lower Oligocene to middle Eocene sediments containing moderately to poorly preserved calcareous nannofossils. Nannofossil assemblages show signs of dissolution and overgrowth, but key marker species can be identified. Nannofossil abundance ranges from abundant to barren. The lower Oligocene sediments are distinctly separated from the overlying Neogene sequences by the Marshall Paraconformity, a regional marker of environmental and sea level change. An age-depth model for Hole 1123C through this sequence was constructed using nine nannofossil age datums and three magnetostratigraphic datums. There is good agreement between the biostratigraphy and magnetostratigraphy, which indicates that the Marshall Paraconformity spans ~12 m.y. in Hole 1123C. The same sequence in Hole 1124C is disrupted by at least three hiatuses, complicating interpretation of the sedimentation history. The Marshall Paraconformity spans at least 3 m.y. in Hole 1124C. A 4- m.y. gap separates lower Oligocene and middle Eocene sediments, and a ~15 m.y. hiatus separates middle Eocene mudstones from middle Paleocene nannofossil-bearing mudstones. Nannofossil biostratigraphy from Holes 1123C and 1124C indicates that the Eocene-Oligocene transition was a time of fluctuating biota and intensification of the DWBC along the New Zealand margin.

Halocarbon and pigment profiles in the waters of the Amundsen and Ross Seas, Antarctica

Little is known regarding the distribution of volatile halogenated organic compounds (halocarbons) in Antarctic waters, and their relation to biophysical variables. During the austral summer (December to January) in 2007-08 halocarbon and pigment concentrations were measured in the Amundsen (100-130ºW) and Ross Sea (158ºW- 160ºE). In addition, halocarbons were determined in air, snow and sea ice. The distribution of halocarbons was influenced to a large extent by sea ice, and to a much lesser extent by pelagic biota. Concentrations of naturally produced halocarbons were elevated in the surface mixed layer in ice covered areas compared to open waters in polynyas and in the bottom waters of the Ross Sea. Higher concentrations of halocarbons were also found in sea ice brine compared to the surface waters. Incubations of snow revealed an additional source of halocarbons. The distribution of halocarbons also varied considerably between the Amundsen and Ross Seas, mainly due to the different oceanographic settings. For iodinated compounds, weak correlations were found with the presence of pigments indicative of Phaeocystis, mainly in the Ross Sea. Saturation anomalies for the surface water and brine (in sea ice) were determined for the two indicator halocarbons bromoform and chloriodomethane. For bromoform, the surface water anomalies varied between -83 and 11%, whereas chloroiodomethane anomalies varied between -6 and 1,200%. The saturation anomalies for brine varied between -56 to 120% for bromoform and 91 to 22,000% for chloroiodomethane, indicating that sea ice could be a possible source both to the atmosphere and the surface waters. Polar waters can have a substantial impact on global halocarbon budgets and need to be included in large-scale assessments.

Distribution of biological, anthropogenic, and volcanic constituents in the San Francisco Bay Coastal System

Although conventional sediment parameters (mean grain size, sorting, and skewness) and provenance have typically been used to infer sediment transport pathways, most freshwater, brackish, and marine environments are also characterized by abundant sediment constituents of biological, and possibly anthropogenic and volcanic, origin that can provide additional insight into local sedimentary processes. The biota will be spatially distributed according to its response to environmental parameters such as water temperature, salinity, dissolved oxygen, organic carbon content, grain size, and intensity of currents and tidal flow, whereas the presence of anthropogenic and volcanic constituents will reflect proximity to source areas and whether they are fluvially- or aerially-transported. Because each of these constituents have a unique environmental signature, they are a more precise proxy for that source area than the conventional sedimentary process indicators. This San Francisco Bay Coastal System study demonstrates that by applying a multi-proxy approach, the primary sites of sediment transport can be identified. Many of these sites are far from where the constituents originated, showing that sediment transport is widespread in the region. Although not often used, identifying and interpreting the distribution of naturally-occurring and allochthonous biologic, anthropogenic, and volcanic sediment constituents is a powerful tool to aid in the investigation of sediment transport pathways in other coastal systems.

Component analysis of three TV-guided grab sampler from the Sahul Shelf (NW Australia)

This paper constitutes a first detailed and systematic facies and biota description of an isolated carbonate knoll (Pee Shoal) in the Timor Sea (Sahul Shelf, NW Australia). The steep and flat-topped knoll is characterized by a distinct facies zonation comprising (A) soft sediments with scattered debris and scarce sponges, hydrozoans and crinoids (320-210 m water depth), (B) hardground outcrops (step-like banks, vertical cliffs) that are mainly colonized by octocorals and sponges (210-75 m), and (C) the summit region (75-21 m) where the slopes merge gently into the flat-topped summit that is densely colonized by massive and encrusting zooxanthellate corals and the octocoral Heliopora coerulea. In contrast, the sediments recovered from the summit are dominated by the green alga Halimeda, subordinate components are corals, benthic foraminifers, mollusks, and coralline red algae. Thus, the sediments are classified as chlorozoan grain assemblage. However, non-skeletal grains (fecal pellets, ooids) are almost completely absent. This discrepancy between the living biota and the sediment composition could reflect a disruption by the severe tropical cyclone Ingrid that hit the northern Australian shelf in March 2005, just before the sampling for this study took place (September 2005).