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We present here results supporting the use of Medium Resolution Imaging Spectrometer (MERIS)-based Near Infrared-Red algorithms for estimating chlorophyll-a (chl-a) concentration in complex coastal waters. The objective of the study was to test the potential of universal applicability of NIR-Red algorithms, calibrated with (a) radiometric measurements and in situ data from inland waters in Nebraska, (b) MERIS data, acquired over Azov Sea in Russia, and (c) data synthetically generated using a radiative transfer model, to estimate chl-a concentration in the Hudson/Raritan Estuary of New York/New Jersey. We used a set of in situ reflectance and water samples collected in the Hudson/Raritan Estuary of New York/New Jersey for this validation. The NIR-Red algorithms produced consistently accurate estimates of chl-a concentration, ranging from 3.9 mg m -3 to 26.3 mg m 3 , with the root mean square error (RMSE) below 2 mg m -3 . The algorithms do not need re-parameterization and it presents a strong case for the use of NIR-Red algorithms for real-time quantitative monitoring of Hudson/Raritan Estuary, and potentially other inland and coastal waters.

The dazzling diversity of the phytoplankton has puzzled biologists for decades(1-5). The puzzle has been enlarged rather than solved by the progressive discovery of new phototrophic microorganisms in the oceans, including picocyanobacteria(6,7), pico-eukaryotes(8), and bacteriochlorophyll-based(9-11) and rhodopsin-based phototrophic bacteria(12,13). Physiological and genomic studies suggest that natural selection promotes niche differentiation among these phototrophic microorganisms, particularly with respect to their photosynthetic characteristics(14-16). We have analysed competition for light between two closely related picocyanobacteria of the Synechococcus group that we isolated from the Baltic Sea(17). One of these two has a red colour because it contains the pigment phycoerythrin, whereas the other is blue-green because it contains high contents of the pigment phycocyanin. Here we report theory and competition experiments that reveal stable coexistence of the two picocyanobacteria, owing to partitioning of the light spectrum. Further competition experiments with a third marine cyanobacterium, capable of adapting its pigment composition, show that this species persists by investing in the pigment that absorbs the colour not used by its competitors. These results demonstrate the adaptive significance of divergence in pigment composition of phototrophic microorganisms, which allows an efficient utilization of light energy and favours species coexistence.

International audience; Phytoplankton observation in the ocean can be a challenge in oceanography. Accurate estimations of its biomass and dynamics will help to understand ocean ecosystems and refine global climate models. Relevant data sets of phytoplankton defined at a functional level and on a sub-meso-and daily scale are thus required. In order to achieve this, an automated, high-frequency, dedicated scanning flow cytometer (SFC, Cytobuoy b.v., the Netherlands) has been developed to cover the entire size range of phytoplankton cells whilst simultaneously taking pictures of the largest of them. This cytometer was directly connected to the water inlet of a PocketFerryBox during a cruise in the North Sea, 08–12 May 2011 (DYMAPHY project, INTERREG IV A " 2 Seas "), in order to identify the phytoplankton community structure of near surface waters (6 m) with a high spatial resolution basis (2.2 ± 1.8 km). Ten groups of cells, distinguished on the basis of their optical pulse shapes, were described (abundance, size estimate, red fluorescence per unit volume). Abundances varied depending on the hydrological status of the traversed waters, reflecting different stages of the North Sea blooming period. Comparisons between several techniques analysing chlorophyll a and the scanning flow cytometer, using the integrated red fluorescence emitted by each counted cell, showed significant correlations. For the first time, the community structure observed from the automated flow cytometry data set was compared with PHYSAT reflectance anomalies over a daily scale. The number of matchups observed between the SFC automated high-frequency in situ sampling and remote sensing was found to be more than 2 times better than when using traditional water sampling strategies. Significant differences in the phyto-plankton community structure within the 2 days for which matchups were available suggest that it is possible to label PHYSAT anomalies using automated flow cytometry to resolve not only dominant groups but also community structure .

The effect of external conditions on the growth morphology of gibbsite, γ-Al(OH)3, grown under a range of conditions has been studied. The results show that during growth the morphology of gibbsite crystals evolves from thin, rounded hexagons and faceted lozenges into faceted plates and blocks with well-formed basal, prismatic and chamfered faces. This morphology evolution shows only a weak dependence on the growth conditions. Moreover, increasing the driving force or the caustic concentration leads to larger crystals, up to tens to a hundred μm in size. The influence of small amounts of inorganic impurities on the growth of gibbsite crystals turns out to be negligible. Different growth morphologies are obtained from potassium and cesium hydroxide solutions. This indicates that the alkali ions of the solution have a major influence on the morphology of gibbsite. The twinning behaviour is similar for gibbsite crystals grown from sodium, potassium or cesium aluminate solutions.

Gibbsite, γ-Al(OH)3, is an important technical product, used mostly as an intermediate in the production of aluminium. According to the literature, the morphology of natural and industrial gibbsite crystals is pseudohexagonal with {0 0 1} basal, and {1 0 0} and {1 1 0} side faces. Laboratory experiments on the growth of γ-Al(OH)3 crystals from unseeded sodium aluminate/sodium hydroxide solutions result in crystals (and agglomerates) with various morphologies, such as lozenge-shaped or hexagonal plates, as well as prisms. Optical polarisation microscopy shows many of the crystals to be twinned. Three kinds of reflection twin with both mirror and composition planes {1 1 0}, {0 0 1} and {1 0 0} were identified. In addition, [1 3 0] rotation twins with {0 0 1} as composition plane were found. The effect of various kinds of twinning on the growth morphology and growth kinetics of γ-Al(OH)3 crystals is studied.

Single crystals of (Pu 1− x U x )Sb (with x =0.25, 0.5 and 0.75) and (Pu 1− x Y x )Sb (with x =0.05, 0.1, 0.4, 0.6, 0.75 and 0.85) were prepared by mineralization and encapsulated for resistivity measurements down to 1.5 K. Resistivity of Pu 0.75 U 0.25 Sb shows two anomalies at 96 and 56 K suggesting two magnetic transitions, respectively, of antiferromagnetic and ferromagnetic type. Pu 0.5 U 0.5 Sb displays a more complex behavior. A first transition is observed around 155 K, followed by a sharp maximum at 120 K and a second anomaly around 35 K. Pu 1− x Y x Sb measured samples show a logarithmic increase of the resistivity with decreasing temperature, suggesting a Kondo behavior. For x =0.4 and 0.6 two magnetic transitions are deduced at 36/20 K and 24/7 K, respectively, and for x =0.75 only one transition is seen around 14 K.

A chlorophyll-retrieval algorithm for use with imagery from the Medium Resolution Imaging Spectrometer (MERIS) aboard ENVISAT relying on wavebands centred at 665, 705 and 775 nm was described in a previous paper (Gons et al. 2002, J. Plankton Res., 24, 947-951). The present study reexamined the performance for the current nominal setting to 708.75 nm of the previously envisaged 705 nm band. Validation of the algorithm with revised coefficients gave the same standard error of estimate for the inland and coastal waters as in the original work. The algorithm has been transcribed for direct application with the MERIS level-2 standard product ‘water-leaving reflectance’. By this correction, chlorophyll estimation will generally improve, especially for high concentrations.

Contains fulltext : 60480.pdf (Publisher’s version ) (Closed access) In-situ optical microscopy was used to measure the growth rate of gibbsite single crystals growing from aqueous sodium aluminate solutions. The growth rate was measured for various crystal faces, i.e., {100} and {001} faces in case of twinned hexagons and {110} faces for single crystalline lozenges. A considerable dispersion in crystal growth rate was measured: the growth rates varied from crystal to crystal within the same experiment as well as from experiment to experiment. They also fluctuated in time. The origin of this dispersion in growth rates is discussed. The results of the growth rates measured as a function of the driving force, which were averaged over several crystals, were fitted with growth rate equations for various growth mechanisms. It is shown that the birth and spread-type growth rate equation defined by Nielsen (J. Cryst. Growth 1984, 67, 289-310) as well as an equation derived in this paper for step nucleation growth at the intersection line of contacting crystallites can be used to describe the growth rates of gibbsite in all crystallographic directions.

A chlorophyll (Chl) a retrieval algorithm, originally developed for spectral subsurface irradiance reflectance determined from above-water shipboard measurements, was adapted for use with satellite imagery to be acquired by the MERIS (Medium Resolution Imaging Spectrometer) instrument. This MERIS algorithm was calibrated for Chl a concentrations in the range 3-185 mg m-3 using spectral reflectance calculated from shipboard measurements on the IJssel Lagoon (The Netherlands). Next, the algorithm was validated for various inland and coastal waters covering this concentration range. Despite the lower spectral resolution of MERIS as compared to the shipboard spectroradiometer, the standard error of estimate is expected to be similar, i.e. similar to 9 mg m-3 of Chl a in mesotrophic and eutrophic lakes, rivers, estuaries and coastal waters.

Optical, scanning electron and atomic force microscopy were used to examine the surface topography of gibbsite (γ-Al(OH) 3 ) crystals grown from supersaturated caustic soda solutions. Several growth phenomena like monomolecular and higher steps, growth hillocks, contact nucleation of steps and planar faults were observed. It turned out that the growth features observed are related to the defect structures of the different gibbsite crystal morphologies found. Single crystalline lozenges of a few μm thickness have hillocks on the basal {0 0 1} faces, which are related to one or a few dislocations. For ultrathin lozenges (few tens of nm thick and an aspect ratio larger than 1000), the surface morphology is flawless and no dislocation sources emerging the {0 0 1} surface were found. Here growth proceeds by 2D nucleation. The second type of crystals, sixfold twinned hexagons, has irregular {0 0 1} surfaces as a result of many defects. The introduction of defects leads to enhanced growth parallel to the c -axis. Lateral expansion proceeds by a 2D nucleation of the fast growing {1 0 0} side faces and the enhanced 2D nucleation at the re-entrant corners at the outcrops of twin planes. Crystals of the third major crystal morphology found, i.e. prisms, also exhibit many defects. Mosaicity was observed and related to the presence of misaligned crystallites or impurities. The fact that the prismatic crystals do not show a pronounced lateral growth as the hexagons do, suggests that besides defects also other factors influence gibbsite crystal growth.

A hand-held spectroradiometer was used for above-water determination of subsurface spectral irradiance reflectance in the Scheldt Estuary (Belgium/The Netherlands), the North Sea off the Belgian coast, and the Hudson/Raritan Estuary (New York/New Jersey). On the North Sea the measurement conditions were adverse, and elsewhere broken cloud caused considerable spectral variation. Despite this variation the retrieval of chlorophyll a (Chl-a) from three reflectance spectra at all sampling stations was stable. The algorithm calibrated for the freshwater IJssel Lagoon (The Netherlands) proved to be applicable to these estuarine and coastal waters(N=30; standard error of estimate = 7 mg m(-3) for corrected Chi-a ranging from 1 to 93 mg m(-3)). [KEYWORDS: OCEANIC WATERS; INLAND WATERS; SATELLITE; PHYTOPLANKTON; REFLECTANCE; MATTER; COLOR; LAKE]

(1991). Role of detritus in the phosphorus balance of Lake Loosdrecht water. SIL Proceedings, 1922-2010: Vol. 24, No. 2, pp. 726-728.

The closed-loop threeway catalyst on the European market has considerably reduced the emissions of passenger cars in an absolute sense. The question arose if gaseous fuels still have a real advantage. To answer this question an extensive programme was set up to compare gasoline and diesel with LPG and natural gas. Not only the regulated components, but also a whole range of unregulated components were measured. The resulting data were grouped into environmental aspects, such as direct local toxicity, longterm toxicity, smog, acidification and global warming. The conclusion is that gaseous fuels still hold an advantage over liquid fuels. 4 refs., 1 fig., 18 tabs.

In shallow, eutrophic Lake Loosdrecht, light attenuation and spectral changes with depth are pronounced due to high concentration of algae and tripton. Calculations of integrated daily primary production have been based on the photosynthesis-irradiance relationship (P/E-curve) obtained with the incubator technique. The suitability of this technique for estimating primary production in such a turbid lake was investigated by comparing P/E-curves for two differently pigmented algae, Oscillatoria limnetica and Prochlorothrix hollandica, in two laboratory systems differing in light regime. System (1) consisted of an incubator filled with tapwater, and system (2) was an algal culture in a laboratory scale enclosure (LSE). For O. limnetica the P/E-curves were identical. The P/E-curves for P. hollandica diverged considerably: the photosynthetic efficiency in the LSE (0.19 mg O2 (mg Chl)−1 h−1 (W m−2)−1 was about half of that obtained in the incubator (0.35 mg O2 (mg Chl)−1 h−1 (W m−2)−1. These results were explained by the interspecific variation in pigmentation. The photosynthetic efficiency of P. hollandica changed due to the dependence on the chlorophyll specific absorption for the whole photosynthetic waveband on the spectral light distribution, which for O. limnetica was approximately the same in the two light regimes. Column-integrated primary production computed with the photosynthetic characteristics of P. hollandica obtained in LSE, was 10–30% lower than the production based on incubator data.

An oscillating steady state is described of phytoplankton, dominated by Prochlorothrix hollandica and Oscillatoria limnetica, and sestonic detritus in shallow, eutrophic Lake Loosdrecht (The Netherlands). A steady-state model for the coupling of the phytoplankton and detritus is discussed in relation to field and experimental data on phytoplankton growth and decomposition. According to model predictions, the phytoplankton to detritus ratio decreases hyperbolically at increasing phytoplankton growth rate and is independent of a lake’s trophic state. The seston in L. Loosdrecht contains more detritus than phytoplankton as will apply to many other lakes. The model provides a basis for estimating the loss rate of the detritus, including decomposition, sedimentation and hydraulic loss. In a shallow lake like L. Loosdrecht detritus will continue to influence the water quality for years.

A study was made of the mortality and aerobic decomposition of light- and phosphorus-limited cultures of Oscillatoria limnetica, a dominant phytoplankton species in shallow, eutrophic Lake Loosdrecht (The Netherlands). When placed in the dark at 20 °C, most cells died and lysed within twelve days. The labile organic matter was completely decomposed within three weeks. Absorbance spectra indicated that blue green algae may contributed significantly to the refractory dissolved substances in the lake. Refractory particulate matter constituted from 7 to 24% of the biomass of O. limnetica, depending on the growth rate before incubation in the dark. The decomposition rate of this fraction was 0.005 d−1. On a basis of a steady-state model of the dynamics of phytoplankton detritus, the areal organic dry weight concentration of the detritus in the lake is ca. 60 g m−2. This means the quantities of detritus in the seston and epipelon are about equal.

Light conditions in laboratory scale enclosures (LSE) of shallow, eutrophic Lake Loosdrecht (The Netherlands), including a method for simulating a ‘natural’ incident light course, are described. Total PAR (400–700 nm) and spectral irradiance distribution were measured at sestonic chlorophyll a and dry weight concentrations ≥ 100 mg m−3 and 16 g m−3, respectively. Phytoplankton was dominated by Oscillatoria spp. The euphotic depth (Z eu) was 0.7–1.0 m. Shortly after filling the LSE with lake water, diffuse attenuation coefficients ranged from 14 m−1 for blue to 5 m−1 for red light. Around Zeu, attenuation in the blue region was markedly lower and irradiance reflectance (R) continued to increase; these anomalies were caused by lateral incident light from the LSE’s waterbath. Spectrophotometry indicated that absorption was mainly by particles, but dissolved humic substances (gilvin) were also important. The particles were likely to be dominated by detritus absorbing more blue relative to red light. Subsurface R in lake water in the LSE had a maximum around 705 nm and low values in the blue band, but was lower than that previously reported for measurements in situ. Wash-out of detritus, presumably both dissolved and particulate fractions, by flow-through with synthetic medium, greatly affected the spectral reflectance measured outside the LSE. The maximum value of R decreased from 0.022 to 0.009, and the peak shifted to 550 nm.

Two-band algorithms that use the ratio of reflectances at 672 and 704 nm have already proved successful for chlorophyll a retrieval in a range of coastal and inland waters. An analysis of the effect of reflectance measurement errors on such algorithms is made. It provides important indications of the range of validity of these algorithms and motivates the development of an entirely new type of adaptive two-band algorithm for hyperspectral data, whereby the higher wavelength is chosen for each input spectrum individually. When one selects the wavelength at which reflectance is equal to the reflectance at the red chlorophyll a absorption peak, chlorophyll a retrieval becomes entirely insensitive to spectrally flat reflectance errors, which are typical of imperfect atmospheric correction, and is totally uncoupled from the retrieval or an estimation of backscatter. This new algorithm has been tested for Dutch inland and Belgian coastal waters. (C) 2001 Optical Society of America. [KEYWORDS: CASE-II WATERS, ATMOSPHERIC CORRECTION, OCEAN COLOR, INLAND WATERS, COASTAL WATERS, SEAWIFS IMAGERY, TURBID COASTAL, PHYTOPLANKTON, MODEL, REFLECTANCE]

Two chronic toxicity experiments were conducted with Daphnia magna. In a semi-static experiment with cohorts, the no effect level for bromide in respect of the intrinsic rate of natural increase (derived from age-specific survival and fecundity) was 10 mg l−1. A second test was started with small populations in an intermittent-flow system. These populations had a stable age distribution, were composed of cohorts of different ages, and showed an almost perfect logistic growth. Model calculations showed that bromide reduced the upper numerical limit (carrying capacity). It also increased the time-lag required to attain the maximum reproduction rate. For the first parameter, a no effect level of 14 mg l−1 was calculated. For the latter a threshold could not be detected. The EC50 and EC10 were 27 and 18 mg l−1, respectively. Additional experiments showed that individual growth of D. magna in time could also be described by a logistic equation. The age structure of the populations changed when food became limiting. This was parallelled by a reduction of the mean brood size. In conclusion it is stated that the results of the toxicity studies with populations support Halbach's view (1984), that population dynamics can be used like a ‘magnifying glass’ to detect small sublethal ecotoxicological effects of environmental pollutants.

(1988). The relationship between oxygen exchange and changes in seston in laboratory scale enclosures. SIL Proceedings, 1922-2010: Vol. 23, No. 2, pp. 756-761.

Since “Actinides 81” the main progress in the preparation of samples for solid state actinide research has been in the growth of single crystals of plutonium compounds. Plutonium metal is obtained by the metallothermic reduction of the ovide or the carbide. It is refined by selective evaporation and vacuum melting. The plutonium compounds are prepared by direct synthesis from the elements using non-contaminating technivues. Single crystals of plutonium monopnictides and monochalcogenides are grown using the mineralivation technivue. Pulling from the melt by the Cvochralski technivue is used to grow single crystals of congruently melting compounds (Laves phases). Single crystals of PuAs, PuSb, PuBi, PuS, PuSe, PuTe, PuvY1−vSb, PuSbi1−vTev, as large as 1 cm3 in volume can be obtained. The crystals are cleaved, oriented and encapsulated for physical property measurements. Specific heat, resistivity, magnetivation, elastic, polarived and inelastic neutron scattering measurement are made in different laboratories of the European Communities.

Ten substances were tested to compare two methods that can be used in chronic toxicity studies with the Cladoceran Daphnia magna. In semistatic experiments with cohorts (life-table studies) survival appeared to be a dominant factor in exponential population growth. Specific inhibition of reproduction as a result of toxic stress was observed only in tests with bromide and 2,4-dichloroaniline. For some substances (cadmium, bichromate, metavanadate, and bromide) individual growth (carapace length) was found to be a sensitive parameter. In intermittent-flow experiments with small expanding populations the yield (carrying capacity) proved to be a highly sensitive parameter, probably owing to the fact that in these tests populations grow logistically, i.e., become additionally stressed by food limitation. Chemically induced reductions in food ingestion and conversion efficiency may thus become very predominant. In view of the place of these crustaceans in the food web such reductions in the carrying capacity would seem to be of great ecotoxicological importance.

Summer populations of the phytoplankton of the Loosdrecht Lakes were enclosed in laboratory scale enclosures (LSE), supplied with 7.5 μg P.l−1.d−1 and 105 μg P.l−1.d−1, respectively. The maximum initial phosphate uptake rate (Vm) was related to irradiance and primary production. At phosphate uptake saturating light-irradiance Vm values up to 4 times the Vm values in the dark were measured.

Important progress has been achieved in solid state physics of the element uranium since large and perfect single crystals of uranium metal and compounds are available. To allow similar progress in the solid state physics of the other actinide elements, a large effort has been undertaken at the European Institute for Transuranium Elements to grow single crystals of actinide compounds with cubic crystal structure like the dioxides, the monopnictides, the monochalcogenides, and some intermetallic compounds. The single crystals enable the measurement of physical properties related to the electronic structure in order to extend the knowledge of chemical bonding in the 5 f transition elements. The different steps allowing the preparation of actinide samples for solid state physics investigations are: • preparation of actinide metals • refining of actinide metals • preparation of compounds by direct synthesis between the elements of the highest available purity • crystal growth • characterization, orientation and encapsulation of the single crystals Actinide dioxides. Actinide dioxide single crystals are obtained by chemical vapour transport (UO2, NpO2) using TeCl4 as transporting agent or by high temperature solution growth with lead vanadate as solvent (ThO2, NpO2, PuO2). Actinide monopnictides. Actinide monopnictide single crystals are grown by the mineralisation technique. Large single crystals (up to 1 2 cm3 of PuAs, PuSb, PuBi were prepared. Actinide intermetallic compounds. Pulling from the levitated melt in a Hukin crucible by the Czochralski technique allows the preparation of intermetallic compound single crystals (AnX3 or Laves phases). A single crystal of PuFe2 (θ 4 mm, 1 = 5 cm) was prepared.