Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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Data from: Warming enhances sedimentation and decomposition of organic carbon in shallow macrophyte-dominated systems with zero net effect on carbon burial
Velthuis, Mandy ; Kosten, S. ; Aben, Ralf ; Kazanjian, Garabet ; Hilt, Sabine ; Peeters, E.T.H.M. ; Donk, Ellen van; Bakker, Elisabeth S. - \ 2019
carbon cycle - decomposition - global warming - mineralization - phenology - primary production - sedimentation - submerged aquatic plant
Temperatures have been rising throughout recent decades and are predicted to rise further in the coming century. Global warming affects carbon cycling in freshwater ecosystems, which both emit and bury substantial amounts of carbon on a global scale. Currently, most studies focus on the effect of warming on overall carbon emissions from freshwater ecosystems, while net effects on carbon budgets may strongly depend on burial in sediments. Here, we tested whether year‐round warming increases the production, sedimentation, or decomposition of particulate organic carbon and eventually alters the carbon burial in a typical shallow freshwater system. We performed an indoor experiment in eight mesocosms dominated by the common submerged aquatic plant Myriophyllum spicatum testing two temperature treatments: a temperate seasonal temperature control and a warmed (+4°C) treatment (n = 4). During a full experimental year, the carbon stock in plant biomass, dissolved organic carbon in the water column, sedimented organic matter, and decomposition of plant detritus were measured. Our results showed that year‐round warming nearly doubled the final carbon stock in plant biomass from 6.9 ± 1.1 g C in the control treatment to 12.8 ± 0.6 g C (mean ± SE), mainly due to a prolonged growing season in autumn. DOC concentrations did not differ between the treatments, but organic carbon sedimentation increased by 60% from 96 ± 9.6 to 152 ± 16 g C m−2 year−1 (mean ± SE) from control to warm treatments. Enhanced decomposition of plant detritus in the warm treatment, however, compensated for the increased sedimentation. As a result, net carbon burial was 40 ± 5.7 g C m−2 year−1 in both temperature treatments when fluxes were combined into a carbon budget model. These results indicate that warming can increase the turnover of organic carbon in shallow macrophyte‐dominated systems, while not necessarily affecting net carbon burial on a system scale.
Warming enhances sedimentation and decomposition of organic carbon in shallow macrophyte-dominated systems with zero net effect on carbon burial
Velthuis, Mandy ; Kosten, Sarian ; Aben, Ralf ; Kazanjian, Garabet ; Hilt, Sabine ; Peeters, Edwin T.H.M. ; Donk, Ellen van; Bakker, Elisabeth S. - \ 2018
Global Change Biology 24 (2018)11. - ISSN 1354-1013 - p. 5231 - 5242.
carbon cycle - decomposition - global warming - mineralization - phenology - primary production - sedimentation - submerged aquatic plant

Temperatures have been rising throughout recent decades and are predicted to rise further in the coming century. Global warming affects carbon cycling in freshwater ecosystems, which both emit and bury substantial amounts of carbon on a global scale. Currently, most studies focus on the effect of warming on overall carbon emissions from freshwater ecosystems, while net effects on carbon budgets may strongly depend on burial in sediments. Here, we tested whether year-round warming increases the production, sedimentation, or decomposition of particulate organic carbon and eventually alters the carbon burial in a typical shallow freshwater system. We performed an indoor experiment in eight mesocosms dominated by the common submerged aquatic plant Myriophyllum spicatum testing two temperature treatments: a temperate seasonal temperature control and a warmed (+4°C) treatment (n = 4). During a full experimental year, the carbon stock in plant biomass, dissolved organic carbon in the water column, sedimented organic matter, and decomposition of plant detritus were measured. Our results showed that year-round warming nearly doubled the final carbon stock in plant biomass from 6.9 ± 1.1 g C in the control treatment to 12.8 ± 0.6 g C (mean ± SE), mainly due to a prolonged growing season in autumn. DOC concentrations did not differ between the treatments, but organic carbon sedimentation increased by 60% from 96 ± 9.6 to 152 ± 16 g C m−2 yaer−1 (mean ± SE) from control to warm treatments. Enhanced decomposition of plant detritus in the warm treatment, however, compensated for the increased sedimentation. As a result, net carbon burial was 40 ± 5.7 g C m−2 year−1 in both temperature treatments when fluxes were combined into a carbon budget model. These results indicate that warming can increase the turnover of organic carbon in shallow macrophyte-dominated systems, while not necessarily affecting net carbon burial on a system scale.

Patterns of Manufacturing Growth in Sub-Saharan Africa : From Colonization to the Present
Austin, G. ; Frankema, E.H.P. ; Jerven, M. - \ 2017
In: The Spread of Modern Industry to the Periphery since 1871 / O'Rourke, Kevin Hjortshoj, Williamson, Jeffrey Gale, Oxford : Oxford University Press - ISBN 9780198753643
Africa - manufacturing - factor endowments - economic policy - primary production - economic history
This chapter reviews the ‘long twentieth-century’ development of ‘modern’ manufacturing in Sub-Saharan Africa from colonization to the present. It argues that classifying Africa generically as a ‘late industrializer’ is inaccurate. To understand the distinctively African pattern of manufacturing growth, the discussion focuses on the dynamic interplay between the region’s specific endowment structures, global economic relationships, and government policies. It concludes that Sub-Saharan Africa is best characterized as a case of interrupted industrial growth instead of sustained convergence on world industrial leaders. This is partly because, until very recently, factor endowments made it very costly for states to pursue industrialization; and partly because successive rulers, colonial and post-colonial, have rarely had both the capacity to adopt and the dedication to sustain policies that modified the region’s existing comparative advantage in primary production, by using their fiscal and regulatory powers effectively to promote industrialization.
Shifts of community composition and population density substantially affect ecosystem function despite invariant richness
Spaak, Jurg W. ; Baert, Jan M. ; Baird, Donald J. ; Eisenhauer, Nico ; Maltby, Lorraine ; Pomati, Francesco ; Radchuk, Viktoriia ; Rohr, Jason R. ; Brink, Paul J. van den; Laender, Frederik De - \ 2017
Ecology Letters 20 (2017)10. - ISSN 1461-023X - p. 1315 - 1324.
Algae - biodiversity - coexistence - community ecology - modelling - primary production

There has been considerable focus on the impacts of environmental change on ecosystem function arising from changes in species richness. However, environmental change may affect ecosystem function without affecting richness, most notably by affecting population densities and community composition. Using a theoretical model, we find that, despite invariant richness, (1) small environmental effects may already lead to a collapse of function; (2) competitive strength may be a less important determinant of ecosystem function change than the selectivity of the environmental change driver and (3) effects on ecosystem function increase when effects on composition are larger. We also present a complementary statistical analysis of 13 data sets of phytoplankton and periphyton communities exposed to chemical stressors and show that effects on primary production under invariant richness ranged from −75% to +10%. We conclude that environmental protection goals relying on measures of richness could underestimate ecological impacts of environmental change.

Schatting van de primaire productie in de Waddenzee in de laatste drie decennia
Riegman, R. - \ 2014
Den Helder : IMARES (Rapport / IMARES Wageningen UR C186/13) - 20
schaal- en schelpdierenvisserij - mosselteelt - primaire productie - waddenzee - oosterschelde - modellen - ecologische modellering - shellfish fisheries - mussel culture - primary production - wadden sea - eastern scheldt - models - ecological modeling
In dit rapport wordt een schatting gepresenteerd van de primaire productie in de oostelijke en de westelijke Waddenzee gedurende de laatste drie decennia. Deze gegevens worden in een ander onderdeel van het project Meerjarige effect- en productiemetingen aan MZI's in de Westelijke Waddenzee en Oosterschelde gebruikt voor het valideren van een model dat het effect berekend van opschaling van MZI’s (mosselzaadinvangsystemen) op de draagkracht voor schelpdieren in de Waddenzee.
Remote sensing of sun-induced fluorescence to improve modeling of diurnal courses of gross primary production (GPP)
Damm, A. ; Elbers, J.A. ; Erler, A. ; Giolis, B. ; Hamdi, K. ; Hutjes, R.W.A. ; Kosvancova, M. ; Meroni, M. ; Migliettas, F. ; Moersch, A. ; Moreno, J. ; Schickling, A. ; Sonnenschein, R. ; Udelhoven, T. ; Linden, S. van der; Hostert, P. ; Rascher, U. - \ 2010
Global Change Biology 16 (2010)1. - ISSN 1354-1013 - p. 171 - 186.
koolstofcyclus - primaire productie - remote sensing - fluorescentie - spectroscopie - planten - fotosynthese - modelleren - carbon cycle - primary production - remote sensing - fluorescence - spectroscopy - plants - photosynthesis - modeling - light-use efficiency - induced chlorophyll fluorescence - photochemical reflectance index - net primary production - eddy covariance - photosynthetic efficiency - leaf senescence - photosystem-ii - carbon-dioxide - boreal forest
Terrestrial gross primary production (GPP) is an important parameter to explore and quantify carbon fixation by plant ecosystems at various scales. Remote sensing (RS) offers a unique possibility to investigate GPP in a spatially explicit fashion; however, budgeting of terrestrial carbon cycles based on this approach still remains uncertain. To improve calculations, spatio-temporal variability of GPP must be investigated in more detail on local and regional scales. The overarching goal of this study is to enhance our knowledge on how environmentally induced changes of photosynthetic light-use efficiency (LUE) are linked with optical RS parameters. Diurnal courses of sun-induced fluorescence yield (FSyield) and the photochemical reflectance index of corn were derived from high-resolution spectrometric measurements and their potential as proxies for LUE was investigated. GPP was modeled using Monteith's LUE-concept and optical-based GPP and LUE values were compared with synoptically acquired eddy covariance data. It is shown that the diurnal response of complex physiological regulation of photosynthesis can be tracked reliably with the sun-induced fluorescence. Considering structural and physiological effects, this research shows for the first time that including sun-induced fluorescence into modeling approaches improves their results in predicting diurnal courses of GPP. Our results support the hypothesis that air- or spaceborne quantification of sun-induced fluorescence yield may become a powerful tool to better understand spatio-temporal variations of fluorescence yield, photosynthetic efficiency and plant stress on a global scale
Lake and watershed characteristics rather than climate influence nutrient limitation in shallow lakes
Kosten, S. ; Huszar, V.M. ; Mazzeo, N. ; Scheffer, M. ; Sternberg, L.S.L. ; Jeppesen, E. - \ 2009
Ecological Applications 19 (2009)7. - ISSN 1051-0761 - p. 1791 - 1804.
waterkwaliteit - voedingsstoffen - meren - stikstof - fosfor - cyanobacteriën - eutrofiëring - herstel - klimaat - zuid-amerika - primaire productie - water quality - nutrients - lakes - nitrogen - phosphorus - cyanobacteria - eutrophication - rehabilitation - climate - south america - primary production - phytoplankton community structure - fresh-water - meteoric precipitation - nitrogen-retention - subtropical lakes - trophic state - danish lakes - n-p - denitrification
Both nitrogen (N) and phosphorus (P) can limit primary production in shallow lakes, but it is still debated how the importance of N and P varies in time and space. We sampled 83 shallow lakes along a latitudinal gradient (5°–55° S) in South America and assessed the potential nutrient limitation using different methods including nutrient ratios in sediment, water, and seston, dissolved nutrient concentrations, and occurrence of N-fixing cyanobacteria. We found that local characteristics such as soil type and associated land use in the catchment, hydrology, and also the presence of abundant submerged macrophyte growth influenced N and P limitation. We found neither a consistent variation in nutrient limitation nor indications for a steady change in denitrification along the latitudinal gradient. Contrary to findings in other regions, we did not find a relationship between the occurrence of (N-fixing and non-N-fixing) cyanobacteria and the TN:TP ratio. We found N-fixing cyanobacteria (those with heterocysts) exclusively in lakes with dissolved inorganic nitrogen (DIN) concentrations of
Toward a consistency cross-check of eddy covariance flux-based and biometric estimates of ecosystem carbon balance
Luyssaert, S. ; Reichstein, M. ; Schulze, E.D. ; Janssens, I.A. ; Law, B.E. ; Papale, D. ; Dragoni, D. ; Goulden, M.L. ; Granier, A. ; Kutch, W.L. ; Linder, S. ; Matteucci, G. ; Moors, E.J. ; Munger, J.W. ; Pilegaard, K. ; Saunders, M. ; Falge, E.M. - \ 2009
Global Biogeochemical Cycles 23 (2009). - ISSN 0886-6236 - 13
netto ecosysteem koolstofbalans - schattingen - eddy-covariantie - primaire productie - biometrie - meetsystemen - net ecosystem carbon balance - estimates - eddy covariance - primary production - biometry - measurement systems - net primary production - gross primary production - ponderosa pine forests - mixed hardwood forest - water-vapor exchange - soil co2 efflux - european forests - beech forest - chamber measurements - spatial variability
Quantification of an ecosystem's carbon balance and its components is pivotal for understanding both ecosystem functioning and global cycling. Several methods are being applied in parallel to estimate the different components of the CO2 balance. However, different methods are subject to different sources of error. Therefore, it is necessary that site level component estimates are cross-checked against each other before being reported. Here we present a two-step approach for testing the accuracy and consistency of eddy covariance–based gross primary production (GPP) and ecosystem respiration (Re) estimates with biometric measurements of net primary production (NPP), autotrophic (Ra) and heterotrophic (Rh) respiration. The test starts with closing the CO2 balance to account for reasonable errors in each of the component fluxes. Failure to do so within the constraints will classify the flux estimates on the site level as inconsistent. If the CO2 balance can be closed, the test continues by comparing the closed site level Ra/GPP with the Rh/GPP ratio. The consistency of these ratios is then judged against expert knowledge. Flux estimates of sites that pass both steps are considered consistent. An inconsistent ratio is not necessarily incorrect but provides a signal for careful data screening that may require further analysis to identify the possible biological reasons of the unexpected ratios. We reviewed the literature and found 16 sites, out of a total of 529 research forest sites, that met the data requirements for the consistency test. Thirteen of these sites passed both steps of the consistency cross-check. Subsequently, flux ratios (NPP/GPP, Rh/NPP, Rh/Re, and Re/GPP) were calculated for the consistent sites. Similar ratios were observed at sites which lacked information to check consistency, indicating that the flux data that are currently used for validating models and testing ecological hypotheses are largely consistent across a wide range of site productivities. Confidence in the output of flux networks could be further enhanced if the required fluxes are independently estimated at all sites for multiple years and harmonized methods are used
Primary production and eddy correlation measurements of CO2 exchange over an intertidal estuary
Zemmelink, H.J. ; Slagter, H.A. ; Slooten van, C. ; Snoek, J.W. ; Heusinkveld, B.G. ; Elbers, J.A. ; Bink, N.J. ; Klaassen, W. ; Philippart, C.J.M. ; Baar, H. de - \ 2009
Geophysical Research Letters 36 (2009)19. - ISSN 0094-8276 - 5
mariene gebieden - waterkwaliteit - primaire productie - kooldioxide - waddenzee - noordzee - estuaria - broeikasgassen - marine areas - water quality - primary production - carbon dioxide - wadden sea - north sea - estuaries - greenhouse gases - gas transfer velocity - continental-shelf - carbon-dioxide - sea - ocean - fluxes - variability - scheldt - budget - flow
Field measurements by eddy correlation indicate an average CO2 uptake of 1.9 g C m-2 d-1 by the intertidal Wadden Sea estuary in spring 2008. The flux did not show a dependency on the tide and fluxes during high and low tide were comparable. We hypothesize that biological production in the water column and in microbial mats that cover sediments lead to an undersaturation of CO2 that is strong enough to support the observed fluxes. The total carbon uptake by this intertidal estuary from day of the year 101–168 is estimated to be -1.7 Tg C. Extrapolation of this flux over three months in spring suggests that the uptake of CO2 by this estuary over this period is comparable to 24% of the yearly carbon flux over the North Sea and the European estuaries
Ecology and risk assessment of E. coli O157:H7 and Salmonella typhimurium in the primary production chain of lettuce
Franz, E. - \ 2007
Wageningen University. Promotor(en): Ariena van Bruggen, co-promotor(en): Aad Termorshuizen. - [S.l.] : S.n. - ISBN 9789085047285 - 216
lactuca sativa - slasoorten - voedselbesmetting - escherichia coli - salmonella typhimurium - stalmest - risicofactoren - microbiële ecologie - bodem - biologische landbouw - biologische voedingsmiddelen - primaire productie - lactuca sativa - lettuces - food contamination - escherichia coli - salmonella typhimurium - farmyard manure - risk factors - microbial ecology - soil - organic farming - organic foods - primary production
Survival of the green fluorescent protein-transformed human pathogens Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium was studied in a laboratorysimulated lettuce production chain. Dairy cows were fed 3 different roughage types: high digestible grass silage + maize silage (6:4), low digestible grass silage and straw. Each was adjusted with supplemental concentrates to a high and low crude protein level. The pathogens were added to manure which was subsequently mixed (after 56 and 28 d for resp. E. coli O157:H7 and Salmonella serovar Typhimurium) with 2 pairs of organically and conventionally managed loamy and sandy soil. After another 14 d, iceberg-lettuce seedlings were planted and checked for pathogens after 21 d of growth. Survival data were fitted to a logistic decline function (exponential for E. coli O157: H7 in soil). Roughage type significantly influenced the decline rate of E. coli O157: H7 in manure with the fastest decline in manure from the pure straw diet and the slowest in manure from the grass-silage + maize-silage diet. Roughage type showed no effect on the rate of decline of Salmonella serovar Typhimurium, although decline was significantly faster in the manure derived from straw compared to the manure from the grass-silage + maize-silage diet. The pH and fiber content of the manure were significant explanatory factors and were positively correlated with the rate of decline. With E. coli O157:H7 there was a trend of faster decline in organic compared to conventional soils. No pathogens were detected in the edible lettuce parts. The results indicate that cattle diet and soil management are important factors with respect to the survival of human pathogens in the environment.
Determinants of terrestrial ecosystem carbon balance inferred from European eddy covariance flux sites
Reichstein, M. ; Papale, D. ; Valentini, R. ; Aubinet, M. ; Bernhofer, C. ; Knohl, A. ; Laurila, T. ; Lindroth, A. ; Moors, E.J. ; Pilegaard, K. ; Seufert, G. - \ 2007
Geophysical Research Letters 34 (2007). - ISSN 0094-8276 - 5
netto ecosysteem koolstofbalans - eddy-covariantie - primaire productie - koolstofcyclus - terrestrische ecosystemen - net ecosystem carbon balance - eddy covariance - primary production - carbon cycle - terrestrial ecosystems - spatial variability - water-vapor - respiration - exchange - forests - climate - productivity - temperature - vegetation - dioxide
Pioneering work in the last century has resulted in a widely accepted paradigm that primary production is strongly positively related to temperature and water availability such that the northern hemispheric forest carbon sink may increase under conditions of global warming. However, the terrestrial carbon sink at the ecosystem level (i.e. net ecosystem productivity, NEP) depends on the net balance between gross primary productivity (GPP) and ecosystem respiration (TER). Through an analysis of European eddy covariance flux data sets, we find that the common climate relationships for primary production do not hold for NEP. This is explained by the fact that decreases in GPP are largely compensated by parallel decreases in TER when climatic factors become more limiting. Moreover, we found overall that water availability was a significant modulator of NEP, while the multivariate effect of mean annual temperature is small and not significant. These results indicate that climate- and particularly temperature-based projections of net carbon balance may be misleading. Future research should focus on interactions between the water and carbon cycles and the effects of disturbances on the carbon balance of terrestrial ecosystems.
Biologische landbouw in Midden- en Oost-Europa
Meeusen-van Onna, M.J.G. ; Bont, C.J.A.M. de; Berkum, S. van; Goddijn, S.T. - \ 2005
Den Haag : LEI (Rapport / LEI : Domein 5, Ketens ) - ISBN 9052429316 - 91
biologische landbouw - economische situatie - aanbod - vraag - verwerking - distributie - polen - hongarije - tsjechië - primaire productie - organic farming - economic situation - supply - demand - processing - distribution - poland - hungary - czech republic - primary production
Dit rapport geeft inzicht in de concurrentiekracht van de biologische landbouwsector in Mid-den- en Oost-Europa. Daarbij is vooral gekeken naar de landen waarvan de concurrentiekracht het grootst wordt geacht: Hongarije, Polen en de Tsjechische Republiek. Er wordt een be-schrijving gegeven van de ontwikkelingen in zowel aanbod als vraag in de betreffende landen, waarbij het niet alleen gaat om de primaire productie maar ook de verwerking en distributie.
Ontwikkeling van de biomassa van het microfytobenthos in het Eems-Dollard estuarium in de periode 1992-1999
Boer, W.F. de - \ 2000
Haren : Koeman & Bijkerk - 66
benthos - waterplanten - biomassa productie - habitats - estuaria - nederland - primaire productie - groningen - eems-dollard - aquatic plants - biomass production - estuaries - netherlands - primary production
De 10 meest gestelde vragen over koolstofvastlegging in bos
Nabuurs, G.J. ; Verkaik, E. - \ 1999
Nederlands Bosbouwtijdschrift 71 (1999)1. - ISSN 0028-2057 - p. 2 - 5.
koolstof - koolstofcyclus - kooldioxide - fotosynthese - biomassa - bio-energie - energie - planten - nuttig gebruik - bossen - bosbouw - bosbedrijfsvoering - milieubescherming - luchtverontreiniging - verontreinigingsbeheersing - conservering - kosten-batenanalyse - cost effective analysis - nederland - primaire productie - biobased economy - carbon - carbon cycle - carbon dioxide - photosynthesis - biomass - bioenergy - energy - plants - utilization - forests - forestry - forest management - environmental protection - air pollution - pollution control - conservation - cost benefit analysis - cost effectiveness analysis - netherlands - primary production
Uitleg en cijfers over de koolstofvoorraden en koolstofvastlegging in het Nederlandse bos, de mogelijkheden om de CO2 uitstoot te compenseren via bosaanplant, de kosteneffectiviteit van dergelijke maatregelen, en het gewenste bostype en bosbeheer om CO2 vast te leggen en de CO2 emissie te reduceren
Linking remote sensing, GIS and crop growth simulation modelling to evaluate regional production scenarios : annual and 6-months progress report, reporting period: 01-05-1997 to 31-10-97 : project 10705.50 (DME-Sur): (integrating remote sensing, GIS and modelling for land-use monitoring in the arid/semi-arid Andes) 1996-1999
Jongschaap, R.E.E. - \ 1997
Wageningen : AB-DLO (Nota / AB-DLO 85) - 26
geografische informatiesystemen - remote sensing - simulatiemodellen - landbouwproductie - zuid-amerika - primaire productie - geographical information systems - simulation models - agricultural production - south america - primary production
Photosystem II electron flow as a measure for phytoplankton gross primary production = [Fotosysteem II elektronentransport als een maat voor de bruto primaire produktie van fytoplankton]
Geel, C. - \ 1997
Agricultural University. Promotor(en): W.J. Vredenberg; J.F.H. Snel. - S.l. : Geel - ISBN 9789054857891 - 110
fotosynthese - fytoplankton - vegetatie - ecosystemen - membranen - bio-energetica - elektrische eigenschappen - planten - biomassa - primaire productie - photosynthesis - phytoplankton - vegetation - ecosystems - membranes - bioenergetics - electrical properties - plants - biomass - primary production
Saturating pulse fluorescence measurements, well known from studies of higher plants for determination of photosystem II (PS II) characteristics, were applied to cultures of the green alga Dunaliella teitiolecta (Chapter 2). The actual efficiency of PS II (φ PS II ), the maximal efficiency of PS II (F v /F m ), and both photochemical and non- photochemical fluorescence quenching were determined for cultures of D. tertiolecta growing under varying light intensities. The rate of PS II electron flow (J E ) estimated as the product of φ PS II , and the photon flux density (PFD), appeared to correlate well with growth rates determined for the D. tertiolecta cultures . The results indicated that the saturating pulse fluorescence method may be successfully used to determine photosynthetic characteristics of phytoplankton. However, an increase of sensitivity by a factor 1000 was found to be needed for the application of this technique to in situ measurements. Conditions were outlined which have led to the development of the Xe-PAM fluorometer with a manyfold higher sensitivity.

The relation between photosynthetic oxygen evolution (J 0 , expressed as oxygen production per chlorophyll a ) and J E was investigated for the marine algae Phaeodactylum tricornutum, D. tertiolecta, Tetraselmis sp., Isochrysis sp. and Rhodomonas sp , by varying the ambient PFD (Chapter 3). At limiting light a linear relation was found in all species. At PFD's approaching light saturation linearity was lost. The observed non-linearity at high M's is most probably not caused by photorespiration but by a Mehler-type of oxygen reduction. The relationship could be modelled by including a redox-state dependent oxygen uptake. The linear range between J E and J 0 extends to a PFD which is 2 to 10 times higher than the PFD at which the species were grown. The ratio of J E and J 0 in the light-limited range is species dependent and related to differences in absorption cross-section of PS II (σ PS II ). The ratio of J E and J 0 in the light-limited range is not dependent on temperature. F v /F m was found to be temperature dependent with an optimum near 10 °C in the diatom P. tricornutum .

The photosynthetic electron flux in a phytoplankton sample (PEF) was shown to depend on the product of J E (= φ PS II · PFD), σ PS II and the number of PS II (n PS II ) in the sample (Chapter 4). A mathematical expression was derived which relates the minimal fluorescence (F 0 ) to n PS II and σ PS II under the condition that the spectral distribution of the ambient light and the measuring light are identical. This condition can be approximated measuring F 0 with the Xe-PAM fluorometer. The experimental conditions under which the relationship between PEF, φ PS II , and F 0 is valid, were examined. The maximal value of φ PS II (F v /F m ) was shown to be independent on the wavelength under the measuring conditions. The apparent F v /F m depends on the intensity of the measuring light and the duration and intensity of the saturating light pulse. It is shown that, under certain conditions, the minimal fluorescence can be used as a measure of PS II excitation in the light. F 0 , obtained with the broad band excitation light of a filtered Xenon flash lamp, thus was used as a measure for the product of n PS II and σ PS II . The relationship between PEF calculated with this expression and net oxygen evolution (phytoplankton oxygen flux, POF, expressed as oxygen production per sample volume) was found to be similar in the diatom P tricornutum and the green alga D. tertiolecta. Therefore we conclude that the use of PEF as a measure for POF yields better results than the use of J E for J 0 . The Xe-PAM fluorometer was found to be sensitive enough for coastal applications.

The relation between PEF and carbon fixation (phytoplankton carbon flux, PCF, expressed as the carbon dioxide fixed per sample volume) was examined in cultures of Isochrysis sp. , Phaeocystis sp. macroflagellates and Skeletonema costatum (Chapter 5). The F 0 used to calculate PEF was measured at the start of the experiments. Both the PFD and the duration of the incubation were varied. As found before for the relation between J E and J 0 , the relation between PEF and PCF was also approximately linear at limiting light and deviated from linearity at saturating light. The linear range between PCF and PEF also extends to a PFD which is 2 to 10 times higher than the PFD at which the species were grown. The length of the incubation did not affect PEF and PCF except for the highest PFD (1530 μmol m -2s -1). The decline of F v /F m of the samples irradiated at the highest PFD showed a fast component within 30 minutes incubation and a minor slow component, indicating that photoinhibition was induced in the first 30 minutes.

PEF, PCF, oxygen production and their relationships were furthermore examined during phytoplankton development in a mesocosm at the field station (Chapter 6). PEF was calculated from F 0 , φ PS II and the PFD which were continuously monitored for three weeks in the upper water layer of the mesocosm. In addition PEF and PCF were estimated from laboratory measurements on samples taken from the mesocosms. Daily primary production in the mesocosm, measured as either PSII electron flow (PPE) or carbon fixation (PPC), was calculated using a photosynthesis model. Daily photosynthetic oxygen evolution (PPO) was calculated from changes in the oxygen concentration over the day. In the period between the 2 blooms the ration of PPO and PPE was higher than during the peak of the blooms. The ratio of PPC and PPE was much more constant. In general PPE gave a reasonable measure of both PPC and PPO.

The effects of chlororespiration and state transitions on F 0 were determined in the diatom P. tricornutum (Chapter 7). Inhibition of chlororespiration by antimycin A or anaerobiosis did not affect F v /F m . The observed F 0 was insignificantly (8%) increased upon addition of antimycin A and slightly decreased upon illumination with farred light (6 μmol m -2s -1). These effects might be attributed to chlororespiratory activity, but could as well be caused by reduction of Q A by the weak fluorescence measuring light. Addition of the uncouplers CCCP or nigericin did not increase the maximal fluorescence (F M ). The data show that under our conditions reduction of Q A and energy dependent quenching in the dark by chlororespiration do not occur in P. tricornutum . Light-induced increases in F M , therefore, are suggested to be caused by state transitions. Use of the F 0 to estimate photon capture in the light might lead to an underestimation of the PEF The error is estimated to be not more than about 10 % as calculated from the increase in maximal fluorescence in the light.

The present work illustrates that the fluorescence pulse method is a reliable technique to get insight into the photosynthetic performance and gross primary production of the population of algal cells in a marine ecosystem.

Simulation of primary production
Anonymous, - \ 1988
Geneva : WMO (CAgM report, Agricultural meteorology programme no. 33A) - 127
agronomie - akkerbouw - biocenose - computersimulatie - ecosystemen - veldgewassen - simulatie - simulatiemodellen - primaire productie - agronomy - arable farming - biocoenosis - computer simulation - ecosystems - field crops - simulation - simulation models - primary production
Le projet Production Primaire au Sahel (PPS) : survol : amélioration de la planification des programmes de développement de l' élevage et de la gestion des ressources naturelles : diffusion des résultats d'une étude des pâturages sahéliens
Breman, H. ; Uithol, P.W.J. - \ 1986
Wageningen : CABO - 117
landbouwproductie - bedrijfssystemen - sahel - bibliografieën - primaire productie - agricultural production - farming systems - bibliographies - primary production
Simulation of primary production in even-aged stands of Douglas-fir
Mohren, G.M.J. ; Gerwen, C.P. van; Spitters, C.J.T. - \ 1984
Forest Ecology and Management 9 (1984). - ISSN 0378-1127 - p. 27 - 49.
biocenose - biomassa - computersimulatie - ecosystemen - bosbouw - houtaanwas - nederland - simulatie - simulatiemodellen - opstandsontwikkeling - opstandsstructuur - bomen - gelijkjarige opstanden - primaire productie - biocoenosis - biomass - computer simulation - ecosystems - forestry - increment - netherlands - simulation - simulation models - stand development - stand structure - trees - even-aged stands - primary production
The Global Carbon Cycle
Bolin, B. ; Degens, E.T. ; Kempe, S. ; Ketner, P. - \ 1979
Chichester : Wiley - 491
biogeochemie - atmosfeer - geochemie - aquatisch milieu - ecosystemen - biocenose - koolstof - primaire productie - biogeochemistry - atmosphere - geochemistry - aquatic environment - ecosystems - biocoenosis - carbon - primary production
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