Beschreibung: Sinking particles, once caught in sediment trap jars, release dissolved elements into the surrounding medium through leaching from their pore fluids, chemical dissolution and the activity of free exoenzymes. This results in an increase in dissolved elements in the trap jar supernatant. Elemental fluxes as traditionally measured by sediment traps underestimate total export when this particle-associated dissolved flux is not considered. The errors introduced are variable and alter both the absolute levels of flux as well as the stoichiometry of export. These errors have been quantified and corrections applied for samples from sediment traps in the North Atlantic based on measurements of excess dissolved carbon, nitrogen, phosphorus, silica and calcium in the supernatant of the collection cups. At the base of the winter mixed layer, on average 90±6% of phosphorus fluxes are found as excess phosphate whereas for carbon and nitrogen dissolved concentrations account for 30 (±8)% and 47(±11)% of total fluxes respectively. Excess dissolved silica is on average 61 (±17)% of total biogenic silica flux. Little (〈10%) of calcium is solubilized. The proportion of dissolved to total flux decreases with trap deployment depth. Calculations of the C:N:P ratios for particles only are well above the Redfield ratios of 106:16:1 (Redfield et al., 1963), although the mid-water dissolved N:P and N:Si values as well as the C:N:P ratios of remineralisation along isopycnals conform to the Redfield ratios at this site. Accounting for dissolved fluxes of all these elements brings the stoichiometry of export in agreement with the Redfield Ratio and with other geochemical estimates of winter mixed layer export. A factor of 3 to 4 higher ratios of organic: inorganic carbon export also implies that the net atmospheric CO2 sequestration by the biological pump is about 50% higher at this site when the dissolved elemental fluxes are considered. Solubilization is thus a process that should be accounted for in protocols used to measure vertical fluxes with sediment traps.

Beschreibung: Taxon-specific microzooplankton dynamics were studied along a transect through the North Atlantic Drift from 70°N 04°E to 40°N 20°W during July 1997 using serial dilution and nutrient-enrichment experiments. Nutrient concentrations and microzooplankton composition indicated postbloom conditions at 40°N, 47°N, and 50°N, a transitional system at 54°N, and bloom conditions at 62°N and 70°N. The ratio of microzooplankton to phytoplankton biomass was inversely related to nitrate and phosphate concentrations. Potential grazing thresholds were observed in four of nine experiments at 40–66% of the initial phytoplankton concentration. Grazing losses were determined for six pigment-specific classes of phytoplankton. Selective grazing losses of phytoplankton taxa ranged from 73% to 248% of the nonselective grazing losses predicted according to their biomass contributions. The grazing selectivity varied considerably between communities, with the microherbivores showing positive selection for cyanobacteria and dinoflagellates and predominantly avoidance of chlorophyta and bacillariophyceae. Microzooplankton did not show a preference for the dominant phytoplankton taxa, but grazed preferentially on fast-growing phytoplankton with minor contributions (〈15%) to the phytoplankton biomass. However, bacillariophyceae were the major contributors to phytoplankton biomass and accounted for major fractions of the total losses through microzooplankton grazing. Microzooplankton consumed the equivalent of 0.12–5.5 times their own biomass daily on a carbon basis, amounting to 65–197% of gross phytoplankton production. With the conservative assumption that 20% of the consumed phytoplankton was converted to microzooplankton biomass, the latter was estimated to contribute 27–381% to the net production of the entire microzooplankton community. We therefore conclude that the taxonomic structure and the net production of the microzooplankton communities were significantly affected by the intensity and selectivity of herbivorous microzooplankton grazing.

Beschreibung: Pelagic processes and their relation to vertical flux have been studied in the Norwegian and Greenland Seas since 1986. Results of long-term sediment trap deployments and adjoining process studies are presented, and the underlying methodological and conceptional background is discussed. Recent extension of these investigations at the Barents Sea continental slope are also presented. With similar conditions of input irradiation and nutrient conditions, the Norwegian and Greenland Seas exhibit comparable mean annual rates of new and total production. Major differences can be found between these regions, however, in the hydrographic conditions constraining primary production and in the composition and seasonal development of the plankton. This is reflected in differences in the temporal patterns of vertical particle flux in relation to new production in the euphotic zone, the composition of particles exported and in different processes leading to their modification in the mid-water layers. In the Norwegian Sea heavy grazing pressure during early spring retards the accumulation of phytoplankton stocks and thus a mass sedimentation of diatoms that is often associated with spring blooms. This, in conjunction with the further seasonal development of zooplankton populations, serves to delay the annual peak in sedimentation to summer or autumn. Carbonate sedimentation in the Norwegian Sea, however, is significantly higher than in the Greenland Sea, where physical factors exert a greater control on phytoplankton development and the sedimentation of opal is of greater importance. In addition to these comparative long-term studies a case study has been carried out at the continental slope of the Barents Sea, where an emphasis was laid on the influence of resuspension and across-slope lateral transport with an analysis of suspended and sedimented material.

Beschreibung: A decade of particle flux measurements providse the basis for a comparison of the eastem and westem provinces ofthe Nordic Seas. Ice-related physical and biological seasonality as well as pelagic settings jointly control fluxes in the westem Polar Province which receives southward flowing water of Polar origin. Sediment trap data from this realm highlight a predominantly physical flux control which leads to exports of siliceous particles within the biological marginal ice zone as a prominent contributor. In the northward flowing waters of the eastem Atlantic Province, feeding Strategie . life histories and the succession of dominant mesozooplankters (copepods and pteropods) are central in controlling fluxes. Furthermore, more calcareous matter is exported here with a shift in flux seasonality towards surnrner/autumn. Dominant pelagic processes modeled numerically as to their impact on annual organic carbon exports for both provinces confirrn that interannual flux variability is related to changes in the respective control mechanisms. Annual organic carbon exports are strikingly similar in the Polar and Atlantic Provinces (2.4 and 2.9 g m-2 y-1 at 500 m depth). despite major differences in flux control. The Polar and Atlantic Provinces. however, can be distinguished according to annual fluxes of opal ( l.4 and 0.6 g m-2 y-1) and carbonate (6.8 and 10.4 g m-2 y-1). lnterannual variability may blur this in single years. Thus. it is vital to use multi-annual data sets when including particle exports in general biogeochemical province descriptions. Vertical flux profiles (collections from 500 m, l000 min both provinces and 300-600 m above the seafloor deviate from the general vertical decline of fluxes due to particle degradation during sinking. At depths 〉 1000 m secondary fluxes (laterally advected/re uspended particles) are often juxtaposed to primary (pelagic) fluxes, a pattem which is most prominent in the Atlantic Province. Spatial variability within theAtlantic Province remains poorly understood. and the same holds true for interannual variability. No proxies are at hand for this province to quantitatively relate fluxes to physical or biological pelagic properties. For the easonally ice-covered Polar Province a robust relationship exists between particle export and ambient ice-regime (Ramseier et al. this volume; Ramseier et al. 1999). Spatial flux pattems may be differentiated and interannual variability can be analyzed in this manner to improve our ability to couple pelagic export pattems with benthic and geochemical sedimentary processes in seasonally ice-covered seas.

Beschreibung: The changing climate of the planet is closely linked to biogeochemical processes in the oceans with important feedbacks between oceanic, atmospheric and terrestrial components of the earth system. This chapter identifies key processes that mediate the response of marine ecosystems to a changing environment and recommends implementation strategies for future studies. Technological and methodological advances such as the use of new biochemical and molecular techniques have led to the discovery of unknown metabolic pathways and identification of genetic diversity in marine systems. Ecosystem changes, reflected in shifts in dominant plankton groups are likely to have a !arge global but also regional impact in the European context. In terms of marine biogeochemical cycling, key processes that respond to a changing climate include photosynthesis (and its modulation by trace meta! availability and nitrogen fixation), calcification and the production and release of a suite of volatile, climate-reactive gasses. Implementation of future research strategies should focus on the ability to monitor key variables from stationary platforms and ships of opportunity with sufficient stability and accuracy to resolve natural and anthropogenic signals. Large-scale in situ manipulation experiments and mesocosm studies are also recommended as well as the application of molecular and genetic techniques that are a powerful means to investigate physiological and biogeochemical transformations that drive the oceans's response to climate change.

Beschreibung: We present barium data for sediment traps deployed in a northeast Atlantic margin environment (Bay of Biscay). Fluxes of excess barium were measured with the objective of calculating carbon export production rates from the surface mixed layer and thus contribute to the understanding of organic carbon transport in a margin environment. Therefore, it was necessary to properly understand the different processes that affected the barium fluxes in this margin environment. Seasonal variability of POC/Ba flux ratios and decrease of barium solubilisation in the trap cups with increasing depth in the water column probably indicate that the efficiency of barite formation in the organic micro-environment varies with season and that the process is relatively slow and not yet completed in the upper 600 m of water column. Thus barite presence in biogenic aggregates will significantly depend on water column transit time of these aggregates. Furthermore, it was observed that significant lateral input of excess-Ba can occur, probably associated with residual currents leaving the margin. This advected excess-Ba affected especially the recorded fluxes in the deeper traps (〉1000 m) of the outer slope region. We have attempted to correct for this advected excess-Ba component, using Th (reported by others for the same samples) as an indicator of enhanced lateral flux and assigning a characteristic Ba/Th ratio to advected material. Using transfer functions relating excess-Ba flux with export production characteristic of margin areas, observed Ba fluxes indicate an export production between 7 and 18 g C m−2 yr−1. Such values are 3–7 times lower than estimates based on N-nutrient uptake and nutrient mass balances, but larger and more realistic than is obtained when a transfer function characteristic of open ocean systems is applied. The discrepancy between export production estimates based on excess-Ba fluxes and nutrient uptake could be resolved if part of the carbon is exported as dissolved organic matter. Results suggest that margin systems function differently from open ocean systems, and therefore Ba-proxy rationales developed for open ocean sites might not be applicable in margin areas.

Beschreibung: Microzooplankton grazing and algae growth responses to increasing pCO2 levels (350, 700 and 1050 μatm) were investigated in nitrate and phosphate fertilized mesocosms during the PeECE III experiment 2005. Grazing and growth rates were estimated by the dilution technique combined with taxon specific HPLC pigment analysis. Microzooplankton composition was determined by light microscopy. Despite a range of up to 3 times the present CO2 levels, there were no clear differences in any measured parameter between the different CO2 treatments. During days 3–9 of the experiment the algae community standing stock, measured as chlorophyll a (Chl-a), showed the highest instantaneous grow rates (k=0.37–0.99 d−1) and increased from ca. 2–3 to 6–12 μg l−1, in all mesocosms. Afterwards the phytoplankton standing stock decreased in all mesocosms until the end of the experiment. The microzooplankton standing stock, that was mainly constituted by dinoflagellates and ciliates, varied between 23 and 130 μg C l−1 (corresponding to 1.9 and 10.8 μmol C l−1), peaking on day 13–15, apparently responding to the phytoplankton development. Instantaneous Chl-a growth rates were generally higher than the grazing rates, indicating only a limited overall effect of microzooplankton grazing on the most dominant phytoplankton. Diatoms and prymnesiophytes were significantly grazed (12–43% of the standing stock d−1) only in the pre-bloom phase when they were in low numbers, and in the post-bloom phase when they were already affected by low nutrients and/or viral lysis. The cyanobacteria populations appeared more affected by microzooplankton grazing which generally removed 20–65% of the standing stock per day.

Beschreibung: A synopsis of results from two sediment trap moorings deployed at the mid- and outer slope (water depths 1450 and 3660 m, respectively) of the Goban Spur (N.E. Atlantic Margin) is presented. Fluxes increase with trap deployment depth; below 1000 m resuspended and advected material contributes increasingly to bulk flux. Fluxes of dry weight, POC and diatoms in the traps 400 m above bottom (mab) are smaller than those recorded at the sediment surface due to lateral fluxes in the benthic nepheloid layer. These near-bottom fluxes are larger at shallower water depths. 231Pa/230Th ratios in sedimenting material suggest that boundary scavenging is not significant at the Goban Spur. Fluxes of 210Pb in the intermediate and deep traps are comparable to the 210Pb supply rate at this site. At the outer slope, sediment 210Pb fluxes are similar to those measured in the traps 400 mab; at the mid-slope they are a factor of 2 higher, once again indicating large near-bottom lateral particle input. Based on POC-normalised biomarkers in sedimenting material, we followed changes in the quality of sedimenting material with differing trap depth and on seasonal and event-related time scales. In spring fresh, diatom-dominated sedimentation occurs, with progressive degradation of POC with time (to winter) and depth (from 600 to 3220 m). Deeper traps are distinguished on the basis of opal and aluminium fluxes that are dominant in lateral input. A storm event during late September 1993 was clearly reflected in the δ15N isotope ratio of sedimenting material, with a time lag of 2–3 weeks. Diatom and opal fluxes were elevated in this storm-related signal, and its biomarker composition in the 600-m trap was similar to that during spring. An estimate made of upward nitrate flux (new production) at the shelf break and at the outer slope indicated a 2-fold higher new (export) production at the shelf break. Particulate organic carbon export from the shelf break to below the depth of maximal seasonal mixing ranges between 3 and 9% of primary production.

Beschreibung: Protecting the ocean has become a major goal of international policy as human activities increasingly endanger the integrity of the ocean ecosystem, often summarized as “ocean health.” By and large, efforts to protect the ocean have failed because, among other things, (1) the underlying socio-ecological pathways have not been properly considered, and (2) the concept of ocean health has been ill defined. Collectively, this prevents an adequate societal response as to how ocean ecosystems and their vital functions for human societies can be protected and restored. We review the confusion surrounding the term “ocean health” and suggest an operational ocean-health framework in line with the concept of strong sustainability. Given the accelerating degeneration of marine ecosystems, the restoration of regional ocean health will be of increasing importance. Our advocated transdisciplinary and multi-actor framework can help to advance the implementation of more active measures to restore ocean health and safeguard human health and well-being.