ALBERT

Description: A seasonally-varying sedimentation pattern was observed for the alkenone flux measured with sediment traps in the northern North Atlantic. In the Norwegian Sea (traps were set at 500, 1000 and 3000 m) the alkenone flux varied between 0.1 and 7.1 μg m−2 d−1 and followed the seasonal pattern of the bulk parameters. Maximum fluxes occurred from mid-October until mid-November and were also high in May. A surprising result was that considerably higher particle fluxes were observed at 3000 m. For the alkenone flux, the highest additional input of 250% was observed during the period when sediment resuspension was greatest in summer. At the Barents Sea continental margin (traps at 1840 and 1950 m) the alkenone fluxes follow the sedimentation pattern of the bulk parameters, with a less visible signal of distinct seasonality observed in the 1950 m trap. The sedimentation of total alkenones varied between 0.8 and 144 μg m−2 d−1 at 1840 m and between 0.5 and 31.0 μg m−2 d−1 at 1950 m. Resuspension and lateral advection contributed significantly to measured fluxes in the two near-bottom traps. Alkenone concentrations were determined in faecal pellets of Appendicularia, ostracods and euphausids from selected samples at the Barents Sea site. The alkenone flux in pellets (4% to 24% of total) was 5 to 6 times higher at 1950 m depth than at 1840 m and the major part (77–78%) of the total flux of C37:3 reaching the near-bottom trap at 1950 m was associated with faecal pellets of the meso-zooplankton. Spatial and temporal variations of the U37k′ signals were observed, indicating that the imprint in the alkenone signal depends on the origin and transport pathway of the organic material. Strong deviations occur in areas where nepheloid layers contribute particles of long residence times to the primary flux.

Description: Long-term observations of the deep ocean particle flux from three sites in the northeast Atlantic (33 degrees N, 22 degrees W; 47 degrees N, 20 degrees W; 54 degrees N, 20 degrees W) provide the basis for comparison and characterization of the biogeochemical provinces in terms of sedimentation pattern. Deep ocean particle flux data (2000 in) for fluxes of total mass and the flux composition are presented and compared to published sediment trap data from this area to consider regional-scale variations in the quantity and composition of settling material. The observations show that in the northeast Atlantic gradient of decreasing mass flux from North to South, exists consistent with known changes of biological productivity in surface waters. This gradient is associated with similar trends in opal and particulate organic carbon, whereas calcium carbonate shows trend in the opposite direction. The changes in the composition of the settling material found along the transect are indicating that the calcium carbonate flux is critical in removing organic matter from the upper ocean to the deeper sink. Its role declines from the subtropical ocean (60-80% of the particle flux) towards North (〈 40%) reflecting the decreasing importance of coccolithophorid/foraminiferal blooms for particle flux from the subtropical to the subpolar North Atlantic. In contrast, the role of biogenic silica (opal) in regard to the ballasting effect increases towards North. The northern sites have much higher percentage of biogenic silica than the sites in the South, because of the deep winter mixing and the seasonality of phytoplankton dominated by diatom blooms during spring and summer. The comparison of the seasonal pattern of particle flux with the seasonal pattern of surface chlorophyll a concentrations from SeaWiFS together with the similarity of the pattern observed in calcium carbonate and opal leads to the conclusion that the particle flux at two positions (33 degrees N, 22 degrees W; 47 degrees N, 20 degrees W) is fast and directly coupled to the phytoplankton dynamics in the overlying euphotic zone.

Description: The subtropical northeast Atlantic has previously been identified as a marine environment with an apparent imbalance between low nitrate supply to the surface and concurrent high export production. To better constrain the sources and fluxes of mixed layer nitrate and to assess the potential role of N2 fixation in providing new nitrogen (N), we investigated the depth distribution of nitrate δ15N and δ18O at six stations across the Azores Front in the NE Atlantic. In addition, we measured the δ15N of dissolved organic N (DON) in surface waters and of sinking particulate N collected in sediment traps at 2000 m depth between 2003 and 2005 at Station KIEL276. The nitrate isotope profiles at the majority of the hydrographic stations displayed a decrease in the δ15N from depth toward low-nitrate surface waters, concomitant with an increase in δ18O. Given that nitrate uptake by phytoplankton leads to a proportional increase in nitrate δ15N and δ18O, the observed surface water nitrate isotope anomalies (Δ(15;18) up to −6‰) indicate that nitrate assimilation is not the sole process controlling the isotopic composition of nitrate in the photic zone and implicate a significant addition of newly fixed N that is remineralized in surface and subsurface waters. Both the concentration of DON and its δ15N in surface water were spatially invariant, showing mean values of 4.7 ± 0.5 μmol L−1 and 2.6 ± 0.4‰ (n = 35), respectively, supporting the conjecture of a mostly recalcitrant DON pool. The weighted biannual mean δ15N of sinking particulate N (1.8 ± 0.8‰, n = 33) was low with respect to thermocline nitrate. The anomalous dual nitrate isotope signatures together with the low δ15N of export production and elevated nitrate-to-phosphate ratios in surface and subsurface waters strongly suggest that N2 fixation represents a substantive source of N in this part of the subtropical northeast Atlantic. Simple isotope mass balance suggests that, locally, N2 fixation supplies between 56 and 259 mmol N m−2 a−1 for phytoplankton growth in the photic zone, accounting for up to ∼40% of the estimated export production.

Description: Planktic foraminiferal (PF) flux and faunal composition from three sediment trap time series of 2002–2004 in the northeastern Atlantic show pronounced year-to-year variations despite similar sea surface temperature (SST). The averaged fauna of the in 2002/2003 is dominated by the species Globigerinita glutinata, whereas in 2003/2004 the averaged fauna is dominated by Globigerinoides ruber. We show that PF species respond primarily to productivity, triggered by the seasonal dynamics of vertical stratification of the upper water column. Multivariate statistical analysis reveals three distinct species groups, linked to bulk particle flux, to chlorophyll concentrations and to summer/fall oligotrophy with high SST and stratification. We speculate that the distinct nutrition strategies of strictly asymbiontic, facultatively symbiontic, and symbiontic species may play a key role in explaining their abundances and temporal succession. Advection of water masses within the Azores Current and species expatriation result in a highly diverse PF assemblage. The Azores Frontal Zone may have influenced the trap site in 2002, indicated by subsurface water cooling, by highest PF flux and high flux of the deep-dwelling species Globorotalia scitula. Similarity analyses with core top samples from the global ocean including 746 sites from the Atlantic suggest that the trap faunas have only poor analogs in the surface sediments. These differences have to be taken into account when estimating past oceanic properties from sediment PF data in the eastern subtropical North Atlantic.

Description: Concentrations of 23 individual chlorobiphenyls (CBs) and 6 polyaromatic hydrocarbons (PAHs) were determined in different water masses of the North Atlantic Ocean around Iceland. The study was carried out in the framework of the second Intergovernmental Oceanographic Commission (IOC) baseline studies of contaminants in the North Atlantic Ocean, involving trace organics and trace elements. Concentrations of individual CBs were extremely low. In solution, they varied between 〈2 and 126 fg dm−3 and in suspension between 〈2 and 1400 fg dm−3. The values for their sum (∑CB) were between 10 and 1048 in solution, and 286–11 241 fg dm−3 in suspension. ∑PAHs were present in the 〈5–65 pg dm−3 range, p,p′-DDE and hexachlorobenzene were 〈2 fg dm−3. The concentrations of CBs and PAHs decreased from the surface towards the bottom at each station. The lowest concentrations were found in Norwegian Sea Deep Water (∑CB 10 fg dm−3), concurrent with the lowest halocarbon concentrations found during the cruise. Values in near-surface waters were considerably lower than those determined at mid-latitudes of the North Atlantic. These findings reflect the mixing of water bodies with higher CB concentrations from the central North Atlantic with less contaminated waters from the Arctic Ocean. Concentrations in suspension exceeded those in solution in most samples, as a result of the relatively high suspended matter concentrations in the waters around Iceland. Particulate CB and PAH concentrations were positively correlated with particulate organic carbon concentrations. This suggests that suspended organic material is a carrier for these relatively apolar organic compounds in the water column. The data do not support the co-distillation concept suggested in the literature.

Description: A system for in-situ filtration and extraction of organics in natural waters has been developed and tested down to 4000 m in the Atlantic Ocean. Up to 2000 dm3 water can be filtered and extracted at low suspended matter concentrations. The sampling equipment has new features for the analysis of trace organic compounds: contamination is extremely low, this can be checked and cured, if necessary, and water flow can be selected and maintained at a constant rate. Various resins can be applied, with different optimum flow rates for the efficient extraction of the compounds of interest. The properties of the resin (here XAD-2) do not change with depth. The operation of the unit is controlled by menu-driven software. All relevant data are stored for later evaluation. Tests in the deep Atlantic resulted in total procedural blanks, including sampling, as low as 0/003 pg dm−3 for individual chlorobiphenyls (CBs), HCB and DDE and 0.5 pg dm−3 for individual PAHs. Actual dissolved concentrations were in the range 0.005–0.1 pg dm−3 for CBs, HCB and DDE and 0.5–140 pg dm−3 for PAHs.

Description: Metabolism of chlorobiphenyls (CBs) was studied in harbour porpoise by comparing patterns of CB-X/CB-153 ratios in blood, brain, liver and blubber with the patterns in herring, the main food source. The CBs were classified in five groups, based on the presence/absence of vicinal H-atoms (vic. Hs) in meta,para (m,p) and/or ortho,meta (o,m) positions and the number of ortho-Cl-atoms (ortho-Cls). Plots of CB-X/CB-153 ratios in porpoise tissue vs the ratios in herring appeared to be linear for each CB group in all tissues. Slopes of these plots (metabolic slopes) were used as quantitative indicators of metabolic activity. In this way, activity of PB-type isozymes of the P450 monooxygenase system was apparent: in contrast to existing literature data, harbour porpoise appears to be able to metabolize congeners with m,p vic. Hs, even in the presence of more than 2 ortho-Cls. The presence of 3-MC-type (MC-type) isozymes was also detected. The metabolic slopes were also used as basis for risk assessment. Due to their metabolism the most toxic non-ortho CBs were not present in the tissues at detectable levels. We suggest a risk assessment approach which takes this into account. It is considered to be an alternative and more reliable basis for risk assessment than the use of toxic equivalent factors. The results support the model of equilibrium distribution of CBs in harbour porpoise and the role of blood as central transport medium. The model has been developed for persistent compounds; it appears to hold for metabolizable CB congeners as well.

Description: A PYE 2-(1-pyrenyl)ethyldimethylsilylated silica gel] column HPLC in combination with MDGC-ECD has been developed for a sensitive and selective determination of toxic mono- and non-ortho PCBs in environmental samples. This technique was applied to environmental samples such as coastal water, suspended particulate material (SPM), coastal sediment, mussels, fish, bird and marine mammal. Determination of PCB 156 along with non-ortho congeners acted as matrix-integrated quality control parameter. This hyphenated technique offers one of the most sensitive way of determining non-ortho PCBs but also reveals the immense complexity of the coelution problem which unnoticed results in over estimation of toxic PCBs in the environmental samples.

Description: The effect of the supply of chlorinated biphenyls by the river Oder into some adjacent areas of Baltic Sea was studied in nine sediment cores and in 10 suspended matter samples. Congener-specific analysis was carried out on 28 individual chlorobiphenyls (CBs). ∑CB concentrations in suspension ranged from 2.4 pg dm-3 in the southern Bornholm Basin to 986 pg dm-3 in the Achterwasser. ∑CB contents in surface sediment decreased with increasing distance from the river mouth. Highest contents were found in the Oderhaff (18 ng g-1 dw) decreasing to 2 ng g-1 dw in the Bornholm Basin. The ∑CB contents generally decreased more or less regularly with increasing depth. The compositions of the CB mixtures in surficial sediment and suspension samples were rather similar, suggesting a common source. Compositions of the CB mixtures in the sediment cores showed distinct differences. These may reflect variations in source strength over time. Mass balance considerations on the basis of the 28 CBs resulted in an estimation of a total storage of approximate 733±158 kg ∑CBs in the Oderhaff, Achterwasser, Greifswalder Bodden, Oder Rinne, Arkona Basin and Bornholm Basin in the past 65 years, covering the time period since CBs were first produced. Based on river data about 500 kg of ∑CBs were supplied during this time by river Oder, that may thus be the major source of these compounds for the southern Baltic Sea.

Description: Individual chlorinated biphenyls (CBs) and chlorinated pesticides (p,p′-DDT and metabolites, HCHs and HCB) were determined in blubber samples of 40 harbour porpoises (Phocoena phocoena) of different age and sex from the North Sea, the Baltic Sea and Greenland coastal waters. Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were analysed in a selected group of animals. ΣCB concentrations (medians) in North Sea immature specimens were similar (14.9 μg/g lipid) to those from the Baltic Sea (17.0 μg/g lipid) and exceeding those in Greenland specimens by an order of magnitude (1.3 μg/g lipid). The median concentrations (μg/g lipid) of HCB, p,p′-DDE, p,p′-DDD and γ-HCH were in the order Greenland〈North Sea〈Baltic Sea. The highest concentrations of α-HCH (0.14 μg/g lipid) were found in the Greenland population, and p,p′-DDT was detected only in this group. The North Sea and Baltic Sea populations were identified as distinctly separate on the basis of levels and compositions of these contaminants. The ecological risk associated with dioxin-like toxicity was dominated by the CB congeners 118 and 170; the PCDD/Fs were playing only a minor role.