Interstitial water chemistry, Deep Sea Drilling Project, Leg 96

On Leg 96 of the Deep Sea Drilling Project (DSDP), holes were drilled in Orca and Pigmy basins on the northern Gulf of Mexico continental slope and on the Mississippi Fan. The holes on the fan encountered interbedded sand, silt, and mud deposited extremely rapidly, most during late Wisconsin glacial time. Pore-water chemistry in these holes is variable, but does not follow lithologic changes in any simple way. Both Ca and SO4 are enriched in the pore water of many samples from the fan. Two sites drilled in the prominent central channel of the middle fan show rapid SO4 reduction with depth, whereas two nearby sites in overbank deposits show no sulfate reduction for 300 m. Calcium concentration decreases as SO4 is depleted and Li follows the same pattern. Strontium, which like Li, is enriched in samples enriched in Ca, does not decrease with SO4 and Ca. Potassium in the pore water decreases with depth at almost all sites. Sulfate reduction was active at the two basin sites and, as on the fan, this resulted in calcium carbonate precipitation and a lowering of pore water Ca, Mg, and Li. The Orca Basin site was drilled through a brine pool of 258? salinity. Pore-water salinity decreases smoothly with depth to 50 m and remains well above normal seawater values to the bottom of the hole at about 90 m. This suggests constant sedimentation under anoxic hypersaline conditions for at least the last 50,000 yr.

Occurrence of radiolarians in DSDP Hole 11-98 (Table 1)

Site 634, drilled during ODP Leg 101, was essentially a reoccupation of Site 98, drilled during DSDP Leg 11 (Hollister, Ewing, et al., 1972, doi:10.2973/dsdp.proc.11.1972; Table 1, Fig. 1). At Site 634, the upper 144 m of sediment was washed in an attempt to reach the Upper Cretaceous target horizon in the time remaining for the cruise (Austin, Schlager, et al., 1986, doi:10.2973/odp.proc.ir.101.1986). Figure 2 illustrates the spatial relationship of Site 98 (2750 m water depth) and Site 634 (2835 m water depth), 0.2 nmi to the northwest. Radiolarians were observed in Site 98 samples from 100 to 240 meters below seafloor (mbsf) during Leg 11, but no detailed biostratigraphic analyses were conducted. Thus, Site 98 presented us an opportunity to sample material correlating with the washed section at Site 634. Samples were taken from Cores 101-634A-2R through 101-634A-4R to study radiolarians, but all proved barren, nor were radiolarians observed in shipboard smear slides. A correlation between Sites 98 and 634 (Fig. 2) suggests that these cores represent the same interval as that recovered in Cores 11-98-10 and 11-98-11, which were also barren. These results are presented separately from other Leg 101 radiolarian studies (Palmer, 1988, datasets: doi:10.1594/PANGAEA.743055) because the Site 98 fauna was predominantly Eocene, while other radiolarian assemblages studied were Oligocene and Miocene.

Spatiotemporal monitoring of water quality in coral reefs of Tayrona National Natural Park, Colombian Caribbean, 2011-2013

Tayrona National Natural Park (TNNP; 11°17' - 11°22' N and 73°53' - 74°12' W) is a hotspot of coral reef biodiversity in the Colombian Caribbean, located between the city of Santa Marta (>455,000 inhabitants) and several smaller river mouths (Rio Piedras, Mendihuaca, Guachaca). The region experiences a strong seasonal variation in physical parameters (temperature, salinity, wind, and water currents) due to alternating dry seasons with coastal upwelling and rainy seasons. Here, a range of water quality parameters relevant for coral reef functioning is provided. Water quality was measured directly above local coral reefs (~10 m water depth) by a monthly monitoring for up to 25 months in the four TNNP bays (Chengue, Gayraca, Neguanje, and Cinto) and at sites with different degree of exposition to winds, waves and water currents (exposed vs. sheltered sites) within each bay. The water quality parameters include: inorganic nutrient (nitrate, nitrite and soluble reactive phosphorus), chlorophyll a, particulate organic carbon and nitrogen concentrations (with a replication of n=3) as well as oxygen availability, biological oxygen demand, seawater pH, and water clarity (with a replication of n=4). This is by far the most comprehensive coral reefs water quality dataset for the region. A detailed description of the methods can be found within the referenced publications.

Chlorophyll a concentration, and proportion of time in the water column obtained by instrumented bowhead whales

Sixty hours of direct measurements of fluorescence were collected from six bowhead whales (Balaena mysticetus) instrumented with fluorometers in Greenland in April 2005 and 2006. The data were used to (1) characterize the three-dimensional spatial pattern of chlorophyll-a (Chl-a) in the water column, (2) to examine the relationships between whale foraging areas and productive zones, and (3) to examine the correlation between whale-derived in situ values of Chl-a and those from concurrent satellite images using the NASA MODIS (Moderate Resolution Imaging Spectroradiometer) EOS-AQUA satellite (MOD21, SeaWifs analogue OC3M and SST MOD37). Bowhead whales traversed 1600 km**2, providing information on diving, Chl-a structure and temperature profiles to depths below 200 m. Feeding dives frequently passed through surface waters ( >50 m) and targeted depths close to the bottom, and whales did not always target patches of high concentrations of Chl-a in the upper 50 m. Five satellite images were available within the periods whales carried fluorometers. Whales traversed 91 pixels collecting on average 761 s (SD 826) of Chl-a samples per pixel (0-136 m). The depth of the Chl-a maximum ranged widely, from 1 to 66 m. Estimates of Chl-a made from the water-leaving radiance measurements using the OC3M algorithm were highly skewed with most samples estimated as <1 mg/m**3 Chl-a, while data collected from whales had a broad distribution with Chl-a reaching >9 mg/m**3. The correlation between the satellite-derived and whale-derived Chl-a maxima was poor, a linear fit explained only 10% of the variance.

Concentrations of aliphatic hydrocarbons and hexachlorocyclohexane isomers in under-ice water, snow, and sea ice from the Greenland Sea

Data on concentrations of aliphatic hydrocarbons and isomers of hexachlorocyclohexane in specimens of various natural environments (water, snow, and ice) of the Greenland Sea obtained during field studies on the ice breaker Otto Shmidt are presented. Analyses were carried out with gas chromatographs using capillary and packed columns. Concentrations of aliphatic and chlorinated hydrocarbons were higher in snow and ice specimens than in sea water and were also higher in less saline water beneath ice. It is concluded that pollutants in this ocean area are at the background level.

Slope stability analyses based on sediment cores of the Ligurian Margin, Southern France

Submarine slope failures of various types and sizes are common along the tectonic and seismically active Ligurian margin, northwestern Mediterranean Sea, primarily because of seismicity up to ~M6, rapid sediment deposition in the Var fluvial system, and steepness of the continental slope (average 11°). We present geophysical, sedimentological and geotechnical results of two distinct slides in water depth >1,500 m: one located on the flank of the Upper Var Valley called Western Slide (WS), another located at the base of continental slope called Eastern Slide (ES). WS is a superficial slide characterized by a slope angle of ~4.6° and shallow scar (~30 m) whereas ES is a deep-seated slide with a lower slope angle (~3°) and deep scar (~100 m). Both areas mainly comprise clayey silt with intermediate plasticity, low water content (30-75 %) and underconsolidation to strong overconsolidation. Upslope undeformed sediments have low undrained shear strength (0-20 kPa) increasing gradually with depth, whereas an abrupt increase in strength up to 200 kPa occurs at a depth of ~3.6 m in the headwall of WS and ~1.0 m in the headwall of ES. These boundaries are interpreted as earlier failure planes that have been covered by hemipelagite or talus from upslope after landslide emplacement. Infinite slope stability analyses indicate both sites are stable under static conditions; however, slope failure may occur in undrained earthquake condition. Peak earthquake acceleration from 0.09 g on WS and 0.12 g on ES, i.e. M5-5.3 earthquakes on the spot, would be required to induce slope instability. Different failure styles include rapid sedimentation on steep canyon flanks with undercutting causing superficial slides in the west and an earthquake on the adjacent Marcel fault to trigger a deep-seated slide in the east.

Physical oceanography from the Drake Passage and Bransfield Strait during Meteor cruise M56

This data publication is the electronic version of hydrographical and fluorometric data which were taken during the Antarctic cruise ANT I No. 56 of 'Meteor' from November 13th to December 18th 1980. The data were measured by means of the Optik Sonde (OS) of the SFB95. The data set contains the temperature and salinity profiles, the profiles of attenuation (extinction) coefficient at 670 nm wavelength and the fluorescence of chlorophyll expressed as chlorophyll a concentration values.

Occurrence, abundance and biomass of photo- and heterotrophic plankton in Norwegian coastal waters

The purpose of the present study was to explore the composition and variation of the pico-, nano- and micro-plankton communities in Norwegian coastal waters and Skagerrak, and the co-occurrence of bacteria and viruses. Samples were collected along three cruise transects from Jaeren, Lista and Oksoy on the south coast of Norway and into the North Sea and Skagerrak. We also followed a drifting buoy for 55 h in Skagerrak in order to observe diel variations. Satellite ocean color images (SeaWiFS) of the chlorophyll a (chl a) distribution compared favorably to in situ measurements in open waters, while closer to the shore remote sensing chl a data was overestimated compared to the in situ data. Using light microscopy, we identified 49 micro- and 15 nanoplankton sized phototrophic forms as well as 40 micro- and 12 nanoplankton sized heterotrophic forms. The only picoeukaryote (0.2-2.0 µm) we identified was Resultor micron (Pedinophyceae). Along the transects a significant variation in the distribution and abundance of different plankton forms were observed, with Synechococcus spp and autotrophic picoeukaryotes as the most notable examples. There was no correlation between viruses and chl a, but between viruses and bacteria, and between viruses and some of the phytoplankton groups, especially the picoeukaryotes. Moreover, there was a negative correlation between nutrients and small viruses (Low Fluorescent Viruses) but a positive correlation between nutrients and large viruses (High Fluorescent Viruses). The abundance of autotrophic picoplankton, bacteria and viruses showed a diel variation in surface waters with higher values around noon and late at night and lower values in the evening. Synechococcus spp were found at 20 m depth 25-45 nautical miles from shore apparently forming a bloom that stretched out for more than 100 nautical miles from Skagerrak and up the south west coast of Norway. The different methods used for assessing abundance, distribution and diversity of microorganisms yielded complementary information about the plankton community. Flow cytometry enabled us to map the distribution of the smaller phytoplankton forms, bacteria and viruses in more detail than has been possible before but detection and quantification of specific forms (genus or species) still requires taxonomic skills, molecular analysis or both.

Organic geochemistry of water and bottom sediments during a seasonal flood in 2006 in the North Dvina River estuary

Heavy contaminant load released into the Northern Dvina River during flooding increased the concentrations of aliphatic (AHC) and polcyclic aromatic (PAH) hydrocarbons in water and bottom sediments. The composition of hydrocarbons was different from that of the summer low flow season. The concentrations of dissolved and particulate AHC ranged from 12 to 106 and from 192 to 599 µg/l, respectively, and bottom sediments contained from 26.2 to 329 µg/g AHC and 4 to 1785 ng/g PAH. As the transformation of AHC occurred at low spring temperatures, the alkane composition was shown to be dominated by terrigenous compounds, whereas more stable PAH showed elevated contents of petrogenic and pyrogenic compounds. It was also shown that the Northern Dvina-Dvina Bay geochemical barrier prevents contaminant input into the White Sea, i.e., acts as a marginal filter.