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.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Effects of food web complexity on top-down control in tropical lakes
Pujoni, Diego Guimarães Florencio ; Maia-Barbosa, Paulina Maria ; Barbosa, Francisco Antônio Rodrigues ; Fragoso, Carlos Ruberto ; Nes, Egbert H. van - \ 2016
Ecological Modelling 320 (2016). - ISSN 0304-3800 - p. 358 - 365.
Intraguild predation - Monte Carlo sensitivity analysis - Omnivory - Trophic cascade - Tropical lakes

Top-down control in ecosystems is dependent on food web structure. In this study, we developed 126 models describing different trophic link combinations in order to assess the effects of food web structure on the top-down response of shallow tropical lakes. We evaluated the effects of the presence of invertebrate predators, large-bodied herbivorous zooplankton and the degree of omnivory. The results showed that the presence of invertebrate predators and large-bodied herbivorous zooplankton can invert the relation between planktivorous/omnivorous fish and producers (algae). The fact that large herbivores are absent in tropical lakes and invertebrate predators are present in large quantities results in a positive correlation between piscivorous fish and algae biomass, contradicting the classical top-down response described for temperate lakes. We show that omnivory should not be analyzed as a feeding strategy in itself. Omnivory affects many food web processes and its effects are dependent on the trophic level. In our models, omnivory in intermediate trophic levels dampened the top-down control by fish, but omnivory in top trophic levels has an opposite effect increasing the fish carrying capacity and also the strength of the top-down trophic cascade, while simultaneously decreasing the shortest chain length between fish and algae, thus reversing the relation between these two trophic levels.

Competition for Water in the Lerma-Chapala Basin
Scott, C.A. ; Silva-Ochoa, P. ; Florencio-Cruz, V. ; Wester, P. - \ 2001
In: The Lerma-Chapala Watershed. Evaluation and management / Hansen, Anne M., van Afferden, Manfred, New York : Kluwer Academic / Plenum Publisher - ISBN 9780306467479 - p. 291 - 323.
pH-stability in anaerobic bioreactors treating methanolic wastewaters.
Florencio, L. ; Field, J.A. ; Langerak, A. van; Lettinga, G. - \ 1996
Water Science and Technology 33 (1996). - ISSN 0273-1223 - p. 177 - 184.
Substrate competition between methanogens and acetogens during the anaerobic degradation of methanol in UASB reactors.
Florencio, L. ; Field, J.A. ; Lettinga, G. - \ 1995
Water Research 29 (1995). - ISSN 0043-1354 - p. 915 - 922.
The role of cobalt on individual trophic groups in an anaerobic methanol degrading consortium.
Florencio, L. ; Field, J.A. ; Lettinga, G. - \ 1994
Applied and Environmental Microbiology 60 (1994). - ISSN 0099-2240 - p. 227 - 234.
The fate of methanol in anaerobic bioreactors
Florencio, L. - \ 1994
Agricultural University. Promotor(en): G. Lettinga; J.A. Field. - S.l. : Florencio - ISBN 9789054852728 - 137
afvalwaterbehandeling - waterzuivering - anaërobe behandeling - rioolwater - afvalwater - industrie - industrieel afval - methanol - waste water treatment - water treatment - anaerobic treatment - sewage - waste water - industry - industrial wastes
<p>Methanol is an important component of certain industrial wastewaters. In anaerobic environments, methanol can be utilized by methanogens and acetogens. In wastewater treatment plants, the conversion of methanol into methane is preferred because this conversion is responsible for chemical oxygen demand (COD) removal, whereas with the formation of volatile fatty acids (VFA) little COD removal is achieved. Moreover, the accumulation of VFA can lead to reactor instability due to pH drops, in weakly buffered systems. The undesirable formation of VFA has previously been associated with the presence of trace elements and bicarbonate in the medium.<p>This thesis investigates the environmental factors that lead to the predominance of acetogens over methanogens during anaerobic wastetewater treatment of methanol. For this purpose, batch and continuous experiment were carried out using a model medium composed of methanol and defined mineral nutrients. The main factors studied were: the effect of trace elements, the reactor pH, the bicarbonate level, and the methanol concentration in the reactor.<p>In Chapter 1 an introductory review is given about anaerobic methylotrophic metabolism in environmental biotechnology. The natural and anthropogenic sources of methanol and other methylated compounds are outlined. In addition, the anaerobic methylotophic microorganisms and the biochemistry of methanol metabolism in methanogens and acetogens are briefly described. Finally, the previous experience in environmental biotechnology with the anaerobic biodegradation of methylotrophic substrates is reviewed. Included is a summary of the reactor types, efficiencies achieved and organic loadings applied for the treatment of wastewaters containing methanol.<p>In Chapter 2, the effect of trace elements on the anaerobic conversion of methanol was studied. Cobalt was the only trace element tested which greatly enhanced methanogenesis from methanol. In continuous experiments, less acetate was formed in a cobalt-deprived reactor than in a cobalt supplemented reactor. These results suggested that cobalt levels could be used to prevent acetate formation from methanol. Therefore, in Chapter 3 the effect of cobalt addition for each individual trophic group was evaluated. Using specific inhibitors, specific activity and the kinetic parameters, μmax and Ks, were determined. Methylotrophic methanogens and acetogens were the only trophic group stimulated by cobalt addition, while the other trophic groups utilizing downstream intermediates, H <sub><font size="-2">2</font></sub> /CO <sub><font size="-2">2</font></sub> or acetate, were largely unaffected. At a low cobalt concentration, both methylotrophs had similar growth rates, whereas at high cobalt levels, acetogens grew slightly faster. The optimal cobalt concentration for both methylotrophic populations was around 0.05 mg · l <sup><font size="-2">-1</font></SUP>.<p>In Chapter 4, the possibility of the anaerobic treatment of methanol without addition of any alkalinity was investigated. Methanol can successfully be converted into methane, regardless of the low pH value of alkalinity-free medium. An astonishing high specific methanogenic activity of 3.57 g COD · g <sup><font size="-2">-1</font></SUP>VSS · d <sup><font size="-2">-1</font></SUP>was evident, which enable the conversion of 13 g COD · l <sup><font size="-2">-1</font></SUP>· d <sup><font size="-2">-1</font></SUP>to methane during continuous operation at a reactor pH 4.2. A <em>Methanosarcina-</em> like organism <em></em> was the main methanogen responsible for the conversion of methanol to methane.<p>Chapter 5 presents the effect of inorganic carbon, alkalinity addition and reactor methanol concentration in anaerobic reactors. The results indicated that acetogenesis occurred only when exogenous bicarbonate was added, when unionized VFA accumulated and in the presence of high methanol concentrations, confirming the previously determined 60 times higher substrate affinity of methanogens.<p>The results of this dissertation are summarized in Chapter 6. Methylotrophic methanogens will predominate over a broad pH range (4.2 to 7.2) if either the reactor methanol concentration, inorganic carbon content, or the cobalt concentration is low. Significant acetogenesis can only be expected to predominate if the reactor methanol concentration is high (>1000 mg COD · l <sup><font size="-2">-1</font></SUP>), exogenous inorganic carbon is supplied, cobalt is available and methanogens are inhibited, <em>e.g.</em> by undissociated VFA. All these four conditions have to be met. Addition of moderate levels of NaHCO <sub><font size="-2">3</font></sub> (approximately 10-20 meq · l <sup><font size="-2">-1</font></SUP>) were found to create such conditions if the reactor was overloaded.
Effect of cobalt on the anaerobic degradation of methanol.
Florencio, L. ; Jenicek, P. ; Field, J.A. ; Lettinga, G. - \ 1993
Journal of fermentation and bioengineering 75 (1993). - ISSN 0922-338X - p. 368 - 374.
Acidophilic degradation of methanol by a methanogenic enrichment culture.
Florencio, L. ; Nozhevnikova, A. ; Langerak, A. van; Stams, A.J.M. ; Field, J.A. ; Lettinga, G. - \ 1993
FEMS Microbiology Letters 109 (1993). - ISSN 0378-1097 - p. 1 - 6.
An acidophilic methanogenic enrichment culture was obtained in a continuous up-flow anaerobic sludge blanket reactor operated at pH 4.2 with methanol as the sole carbon source. The specific methylotrophic methanogenic activity of the enriched reactor sludge at pH 5 was 3.57 g COD g−1 volatile suspended solids day−1 and the apparent doubling time of the biomass was 15.8 h. Acidic conditions were obligatory, since the enrichment culture was not able to produce methane or to grow at pH 7. Based on morphological characteristics, the dominant methanogenic species in the enrichment culture was a Methanosarcina.
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