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In seawater, trace metals occur in many forms: free ion, labile and non-labile complex, colloid, associated with particles, but only free ions and very labile metal complexes can cross the phytoplankton membrane and be assimilated. In this paper we review the most appropriate determination methods for those metal species, addressing particularly in situ speciation and preconcentration. Focus is on DGT-ICPMS, which is a technique that meets these criteria very well. In coastal environments, DGT probes are widely used for metal pollution monitoring, but in open ocean a carrier such as a glider, is required. In open ocean organic metal complexation has been studied using DGT-ICPMS and electrochemical methods. The use of DGTs with different diffusion domain thicknesses provides information to quantify labilities and dissociation rates of metal complex pools. Labilities of metal complexes in coastal waters appeared to be higher than in open sea.

We stoten te veel CO2 uit, dat moeten we je niet meer vertellen. Zou het niet fantastisch zijn, mochten we die CO2 gewoon uit de lucht kunnen vissen? Wél, daar zijn ze aan de VUB mee bezig. Via plankton! 't Is te zeggen: plankton doet dat al vanzelf. En nu zoekt VUB-marine-bioloog Willy Baeyens uit of hij de oceaan niet een beetje kan bemesten zodat er méér plankton groeit...

In this first in situ study of the dynamic availability of phytoplankton micronutrients, a SeaExplorer glider was combined with Diffusive Gradients in Thin Films and deployed in the Mediterranean Sea. On the basis of their labile metal complex pools, we discovered that Fe and Co can be potentially limiting and Cu co-limiting to diatom growth, contrary to the generally accepted view that phosphorus (phosphate) is the growth limiting element in the Mediterranean Sea. For flagellates and picoplankton, phosphorus remains the main element limiting growth. Our in situ measurements showed that organic complexes of Fe and Cu (>98% of total dissolved concentration), dissociate slower than inorganic complexes of Co, Cd and Ni (>99% of total dissolved concentration being free ions and inorganic complexes). This strengthens the potential growth limiting effect of Fe and Cu versus phosphate, which is present as a free ion and, thus, directly available for plankton. © 2018, The Author(s).

Smelt Osmerus eperlanus has two different life history strategies in the Netherlands. The migrating population inhabits the Wadden Sea and spawns in freshwater areas. After the closure of the Afsluitdijk in 1932, part of the smelt population became landlocked. The fresh water smelt population has been in severe decline since 1990, and has strongly negatively impacted the numbers of piscivorous water birds relying on smelt as their main prey. The lakes that were formed after the dike closure, IJsselmeer and Markermeer have been assigned as Natura 2000 sites, based on their importance for (among others) piscivorous water birds. Because of the declining fresh water smelt population, the question arose whether this population is still supported by the diadromous population. Opportunities for exchange between fresh water and the sea are however limited to discharge sluices. The relationship between the diadromous and landlocked smelt population was analysed by means of otolith microchemistry. Our interpretation of otolith strontium (88Sr) patterns from smelt specimens collected in the fresh water area of Lake IJsselmeer and Markermeer, compared to those collected in the nearby marine environment, is that there is currently no evidence for a substantial contribution from the diadromous population to the spawning stock of the landlocked population.

Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Marine Chemistry 126 (2011): 108-113, doi:10.1016/j.marchem.2011.04.004., Photosynthesis by marine phytoplankton requires bioavailable forms of several trace elements that are found in extremely low concentrations in the open ocean. We have compared the concentration, lability and size distribution (< 1 nm and < 10 nm) of a suite of trace elements that are thought to be limiting to primary productivity as well as a toxic element (Pb) in two High Nutrient Low Chlorophyll (HNLC) regions using a new dynamic speciation technique, Diffusive Gradients in Thin-film (DGT). The labile species trapped within the DGT probes have a size that is smaller or similar than the pore size of algal cell walls and thus present a proxy for bioavailable species. Total Dissolvable trace element concentrations (TD concentration) varied between 0.05 nM (Co) and 4.0 nM (Ni) at K2 (Northwest Pacific Ocean) and between 0.026 nM (Co) and 4.7 nM (Ni) in the Southern Ocean. The smallest size fractionated labile concentrations (< 1 nm) observed at Southern Ocean sampling stations ranged between 0.002 nM (Co) and 2.1 nM (Ni). Moreover, large differences in bioavailable fractions (ratio of labile to TD concentration) were observed between the trace elements. In the Northwest Pacific Ocean Fe, Cu and Mn had lower labile fractions (between 10 and 44%) than Co, Cd, Ni and Pb (between 80 and 100%). In the Southern Ocean a similar trend was observed, and in addition: (1) Co, Cd, Ni and Pb have lower labile fractions in the Southern Ocean than in the Northwest Pacific and (2) the ratios of <1nm to dissolvable element concentrations at some Southern Ocean stations were very low and varied between 4 and16 %., This research was supported by Federal Science Policy Office, Brussels, through contracts EV/03/7A, SD/CA/03A, the Research Foundation Flanders through grant G.0021.04 and Vrije Universiteit Brussel via grant GOA 22, as well as for K2, the VERTIGO program funding primarily by the US National Science Foundation programs in Chemical and Biological Oceanography

Author Posting. © Elsevier B.V., 2008. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 55 (2008): 1673-1683, doi:10.1016/j.dsr2.2008.04.020., This study focuses on the fate of exported organic carbon in the twilight zone at two contrasting environments in the North Pacific: the oligotrophic ALOHA site (22°45' N 158°W; Hawaii; studied during June–July 2004) and the mesotrophic Subarctic Pacific K2 site (47°N, 161°W; studied during July-August 2005). Earlier work has shown that non-lithogenic, excess particulate Ba (Baxs) in the mesopelagic water column is a potential proxy of organic carbon remineralization. In general Baxs contents were significantly larger at K2 than at ALOHA. At ALOHA the Baxs profiles from repeated sampling (5 casts) showed remarkable consistency over a period of three weeks, suggesting that the system was close to being at steady state. In contrast, more variability was observed at K2 (6 casts sampled) reflecting the more dynamic physical and biological conditions prevailing in this environment. While for both sites Baxs concentrations increased with depth, at K2 a clear maximum was present between the base of the mixed layer at around 50m and 500m, reflecting production and release of Baxs. Larger mesopelagic Baxs contents and larger bacterial production in the twilight zone at the K2 site indicate that more material was exported from the upper mixed layer for bacterial degradation deeper, compared to the ALOHA site. Furthermore, application of a published transfer function (Dehairs et al., 1997) relating oxygen consumption to the observed Baxs data indicated that the latter were in good agreement with bacterial respiration, calculated from bacterial production. These results corroborate earlier findings highlighting the potential of Baxs as a proxy for organic carbon remineralization. The range of POC remineralization rates calculated from twilight zone excess particulate Ba contents did also compare well with the depth dependent POC flux decrease as recorded by neutrally buoyant sediment traps, except in 1 case (out of 4). This discrepancy could indicate that differences in sinking, This research was supported by Federal Science Policy Office, Brussels through contracts EV/03/7A, SD/CA/03A, the Research Foundation Flanders through grant G.0021.04 and Vrije Universiteit Brussel via grant GOA 22, as well as the US National Science Foundation programs in Chemical and Biological Oceanography.

Author Posting. © Elsevier B.V., 2008. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 55 (2008): 1594-1604, doi:10.1016/j.dsr2.2008.04.013., This paper presents results on tracer experiments using 13C and 15N to estimate uptake rates of dissolved inorganic carbon (DIC) and nitrogen (DIN). Experiments were carried out at station K2 (47°N, 161°E) in the NW Pacific subarctic gyre during July-August 2005. Our goal was to investigate relationships between new and export production. New production was inferred from the tracer experiments using the f ratio concept (0-50m); while export production was assessed with neutrally buoyant sediment traps (NBSTs) and the e ratio concept (at 150m). During trap deployments, K2 was characterized both by changes in primary production (523 to 404 mg C m-2 d-1), new production (119 to 67 mg C m-2 d-1), export production (68 to 24 mg C m-2 d-1) and phytoplankton composition (high to low proportion of diatoms). The data indicate that 17 to 23% of primary production is exportable to deeper layers (f ratio) but only 6 to 13% collected as a sinking particle flux at 150m (e ratio). Accordingly, > 80% of the carbon fixed by phytoplankton would be mineralized in the upper 50m (1 – f), while < 11% would be within 50-150m (f – e). DIN uptake flux amounted to 0.5 mM m-2 h-1, which was equivalent to about 95% particulate nitrogen (PN) remineralized and/or grazed within the upper 150 m. Most of the shallow PN remineralization occurred just above the depth of the deep chlorophyll maximum (DCM), where a net ammonium production was measured. Below the DCM, while nitrate uptake rates became negligible because of light limitation, ammonium uptake did continue to be significant. The uptake of ammonium by heterotrophic bacteria was estimated to be 14-17% of the DIN assimilation. Less clear are the consequences of this uptake on the phytoplankton community and biogeochemical processes, e.g. new production. It was suggested that competition for ammonium could select for small cells and may force large diatoms to use nitrate. This implies that under Fe stress as observed here, ammonium uptake is pr, This research was supported by the Research Foundation Flanders through grant G.0021.04 and Vrije Universiteit Brussel via grant GOA 22, as well as the US National Science Foundation programs in Chemical and Biological Oceanography.

info:eu-repo/semantics/nonPublished

The aim of this study is to propose a strategy to implement a PAT system in the blending step of pharmaceutical production processes. It was examined whether Raman spectroscopy can be used as PAT tool for the in-line and real-time endpoint monitoring and understanding of a powder blending process. A screening design was used to identify and understand the significant effects of two process variables (blending speed and loading of the blender) and of a formulation variable (concentration of active pharmaceutical ingredient (API): diltiazem hydrochloride) upon the required blending time (response variable). Interactions between the variables were investigated as well. A Soft Independent Modelling of Class Analogy (SIMCA) model was developed to determine the homogeneity of the blends in-line and real-time using Raman spectroscopy in combination with a fiber optical immersion probe. One blending experiment was monitored using Raman and NIR spectroscopy simultaneously. This was done to verify whether two independent monitoring tools can confirm each other's endpoint conclusions. The analysis of the experimental design results showed that the measured endpoints were excessively rounded due to the large measurement intervals relative to the first blending times. This resulted in effects and critical effects which cannot be interpreted properly. To be able to study the effects properly, the ratio between the blending times and the measurement intervals should be sufficiently high. In this study, it anyway was demonstrated that Raman spectroscopy is a suitable PAT tool for the endpoint control of a powder blending process. Raman spectroscopy not only allowed in-line and real-time monitoring of the blend homogeneity, but also helped to understand the process better in combination with experimental design. Furthermore, the correctness of the Raman endpoint conclusions was demonstrated for one process by using a second independent endpoint monitoring tool (NIR spectroscopy). He, info:eu-repo/semantics/published

The ecological functioning of estuarine environments is greatly influenced by human activity. One of the most important perturbations lies in the increased inputs of nutrients, mainly nitrogen (N), to these systems. This N is submitted to various biogeochemical processes leading to recycling, retention and export to the sea. In this article we present results from 15N-incubation experiments allowing the simultaneous determination of NH4+ and NO3– uptake, nitrification and ammonification rates in the waters of a eutrophic temperate macrotidal estuary (the Scheldt in Belgium and The Netherlands) for different seasons. These are compared to whole estuarine nitrogen budgets. Results showed that nitrogen cycling in this system is dominated in all seasons by the mineralization of organic matter leading to a supply of dissolved inorganic nitrogen (DIN) exceeding river inputs. During winter, summer and fall seasons, only 6 to 10% of this DIN is recycled by microorganisms and most is eliminated (50 to 60%), probably by denitrification in the sediments, and exported (30 to 40%) to the sea. In spring, a larger fraction of DIN (around 70%) is recycled by microorganisms, while only 2% is eliminated and 26% is exported. Overall, we conclude that turbid eutrophic temperate estuaries as the Scheldt may have low DIN recycling efficiencies because of low in situ primary production except in spring., The ecological functioning of estuarine environments is greatly influenced by human activity. One of the most important perturbations lies in the increased inputs of nutrients, mainly nitrogen (N), to these systems. This N is submitted to various biogeochemical processes leading to recycling, retention and export to the sea. In this article we present results from 15N-incubation experiments allowing the simultaneous determination of NH4+ and NO3– uptake, nitrification and ammonification rates in the waters of a eutrophic temperate macrotidal estuary (the Scheldt in Belgium and The Netherlands) for different seasons. These are compared to whole estuarine nitrogen budgets. Results showed that nitrogen cycling in this system is dominated in all seasons by the mineralization of organic matter leading to a supply of dissolved inorganic nitrogen (DIN) exceeding river inputs. During winter, summer and fall seasons, only 6 to 10% of this DIN is recycled by microorganisms and most is eliminated (50 to 60%), probably by denitrification in the sediments, and exported (30 to 40%) to the sea. In spring, a larger fraction of DIN (around 70%) is recycled by microorganisms, while only 2% is eliminated and 26% is exported. Overall, we conclude that turbid eutrophic temperate estuaries as the Scheldt may have low DIN recycling efficiencies because of low in situ primary production except in spring.