Jaap Van Rijn - Academia.edu (original) (raw)

Papers by Jaap Van Rijn

Modern Agriculture and the Environment, 1997

Water Research, 2011

Alkalinity DIC a b s t r a c t Interest in mariculture systems will rise in the near future due t... more Alkalinity DIC a b s t r a c t Interest in mariculture systems will rise in the near future due to the decreased ability of the ocean to supply the increasing demand for seafood. We present a trace study using stable carbon and nitrogen isotopes and chemical profiles of a zero-discharge mariculture system stocked with the gilthead seabream (Sparus aurata). Water quality maintenance in the system is based on two biofiltration steps. Firstly, an aerobic treatment step comprising a trickling filter in which ammonia is oxidized to nitrate. Secondly, an anaerobic step comprised of a digestion basin and a fluidized bed reactor where excess organic matter and nitrate are removed. Dissolved inorganic carbon and alkalinity values were higher in the anaerobic loop than in the aerobic loop, in agreement with the main biological processes taking place in the two treatment steps. The d 13 C of the dissolved inorganic carbon (d 13 C DIC ) was depleted in 13 C in the anaerobic loop as compared to the aerobic loop by 2.5e3&. This is in agreement with the higher dissolved inorganic carbon concentrations in the anaerobic loop and the low water retention time and the chemolithotrophic activity of the aerobic loop. The d 13 C and d 15 N of organic matter in the mariculture system indicated that fish fed solely on feed pellets. Compared to feed pellets and particulate organic matter, the sludge in the digestion basin was enriched in 15 N while d 13 C was not significantly different. This latter finding points to an intensive microbial degradation of the organic matter taking place in the anaerobic treatment step of the system. ª

Fish & Shellfish Immunology, 1997

ABSTRACT

Environmental Microbiology, 2003

Bacterial community structure and physiochemical parameters were examined in a sedimentation basi... more Bacterial community structure and physiochemical parameters were examined in a sedimentation basin of a zero-discharge mariculture system. The system consisted of an intensively stocked fish basin from which water was recirculated through two separate treatment loops. Surface water from the basin was pumped over a trickling filter in one loop while bottom-water was recirculated through a sedimentation basin followed by a fluidized bed reactor in the other. Ammonia oxidation to nitrate in the trickling filter and organic matter digestion together with nitrate reduction in the sedimentation basin and fluidized bed reactor, allowed zero-discharge operation of the system. Relatively high concentrations of oxygen, nitrate, sulphate and organic matter detected simultaneously in the digestion basin suggested the potential for a wide range of microbially-mediated transformation processes. In this study, physiochemical parameters were correlated to bacterial diversity and distribution in horizontal and vertical profiles within this basin in an effort to obtain a basic understanding of the chemical and microbial processes in this system. Chemical activity and microbial diversity, the latter measured by denaturing gradient gel electrophoresis (DGGE) analysis of polymerase chain reaction (PCR) amplified 16S rDNA fragments, were higher in the sludge layer than in the overlying aqueous layer of the basin. Chemical parameters in sludge samples close to the basin inlet suggested enhanced microbial activity relative to other sampling areas with evidence of both nitrate and sulphate reduction. Four of the nine DGGE bands identified in this zone were affiliated with the Bacteroidetes phylum. Detected sequences closely related to sequences of organisms involved in the sulphur cycle included Desulfovibrio , Dethiosulfovibrio and apparent sulphur oxidizers from the gamma-proteobacteria. In addition, a number of sequences from the beta and alpha-proteobacteria were identified.

Aquaculture, 1996

... Removal of small suspended solids can be accom plished by either chemical or biological oxida... more ... Removal of small suspended solids can be accom plished by either chemical or biological oxidation. Chemical oxidation by ozonation can be applied to reduce the organic load in conventional waste water treatment (Metcalf and Eddy, 1991). ...

Aquacultural Engineering, 2000

... Aquaculture sludge treatment using anaerobic and facultative lagoon system. In: Libey, GS and... more ... Aquaculture sludge treatment using anaerobic and facultative lagoon system. In: Libey, GS and Timmons, MB Editors, 1996. ... Kuba, T., Smolders, G., van Loosdrecht, MCM and Heijnen, JJ, 1997. A metabolic model for biological phosphorus removal by denitrifying organisms. ...

Applied and Environmental Microbiology, 2000

Polyphosphate accumulation by Paracoccus denitrificans was examined under aerobic, anoxic, and an... more Polyphosphate accumulation by Paracoccus denitrificans was examined under aerobic, anoxic, and anaerobic conditions. Polyphosphate synthesis by this denitrifier took place with either oxygen or nitrate as the electron acceptor and in the presence of an external carbon source. Cells were capable of poly-␤-hydroxybutyrate (PHB) synthesis, but no polyphosphate was produced when PHB-rich cells were incubated under anoxic conditions in the absence of an external carbon source. By comparison of these findings to those with polyphosphateaccumulating organisms thought to be responsible for phosphate removal in activated sludge systems, it is concluded that P. denitrificans is capable of combined phosphate and nitrate removal without the need for alternating anaerobic/aerobic or anaerobic/anoxic switches. Studies on additional denitrifying isolates from a denitrifying fluidized bed reactor suggested that polyphosphate accumulation is widespread among denitrifiers.

Aquaculture, 2003

... reactor (5 g biofilm−coated sand), the trickling filter (6 cm 2 of biofilm−coated PVC), the .... more ... reactor (5 g biofilm−coated sand), the trickling filter (6 cm 2 of biofilm−coated PVC), the ... Dry weight of particulate material was determined after overnight drying at 105 °C. ... 3). Total phosphorus in the various treatment compartments showed that phosphorus did not accumulate in ...

Water Research, 2008

A v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w... more A v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / w a t r e s 0043-1354/$ -see front matter ª w a t e r r e s e a r c h 4 2 ( 2 0 0 8 ) 4 3 8 6 -4 3 9 2

Water Research, 2009

In a previous study on a recirculating fish culture system, levels of geosmin and 2-methylisoborn... more In a previous study on a recirculating fish culture system, levels of geosmin and 2-methylisoborneol were found to decrease when culture water was recirculated through the anaerobic sludge digestion treatment stage of the system. This finding led us to the present study in which the geosmin and 2-methylisoborneol removal capacity of the sludge derived from this treatment stage was examined in vitro. It was found that reduction of off-flavor compounds by the sludge was mediated by both chemical/physical sorption and biological degradation. At geosmin and 2-methylisoborneol concentrations within the range of those experienced in fish culture systems, chemical/physical sorption by the sludge was found to account for a 93% reduction in geosmin and a 79% reduction in 2-methylisoborneol from the overlying water within 48h of incubation. Combined with the biological degradation taking place in the sludge, a complete removal of these compounds from the water phase occurred within 9 days of incubation. By means of repeated washing of the geosmin and 2-methylisoborneol contaminate sludge with clean water, relatively small amounts of these compounds were released from the sludge, a possible indication for the fact that absorption, rather than adsorption, underlies the chemical/physical removal process.

Biomolecular Engineering, 2003

While there is an urgent demand to establish reliable ecotoxicological assays for reef corals, th... more While there is an urgent demand to establish reliable ecotoxicological assays for reef corals, there has not been yet an available source material that can supply the high number of colony replicates needed for reliable tests. In past experiments, the major obstacle to obtaining as many fragments as possible had been the damage inflicted to donor colonies by pruning. In this paper, we present the application of coral nubbins, a novel source material for coral ecotoxicology assays. Nubbins from the branching Red Sea coral Stylophora pistillata (n /450) were used for evaluating the impacts of water soluble fractions from a crude oil, an oil dispersant and dispersed oil. Coral nubbins (minute coral fragments in the size of one to several polyps) harvested from a single colony are genetically identical to each other, may be obtained in any quantity needed and whenever research activities demand their use. Several dozens of nubbins can be obtained from a single small branch in branching coral species, a procedure that has minimal impact on donor genotypes. Nubbins production is a low cost procedure and requires limited maintenance space. Results of short and long-term acute ecotoxicological tests are revealed and discussed here, indicating the advantageous use of nubbins as ubiquitous coral material for toxicology assays and physiological studies. #

Marine Biology, 2006

Many coral reefs worldwide are rapidly declining, but efficient restoration techniques are not ye... more Many coral reefs worldwide are rapidly declining, but efficient restoration techniques are not yet available. Here, we evaluate methodologies for reef restoration based on the ''gardening concept''. A floating mid-water prototype nursery was placed at 6 m depth (14 m above sea-bottom) within the nutrient-enriched environment of a fish farm (Eilat, Red Sea). Ten colonies from five branching coral species provided 6,813 fragments (0.5-3 cm height). The fragments, each attached to a plastic pin, were inserted into plastic nets that were tied to a rope-net floating nursery. After 144 nursery days, only 13.1% of the fragments died and 21.2% were detached by mechanical forces. Small colonies ready for transplantation developed within 144-200 days. Ramets' ecological volumes increased 13-46 folds and their heights by a factor of 3.5. After 306 days, the ecological volumes of the colonies increased 147-163 fold as compared to original volumes (revealing a daily growth rate constant of 1.67% during the first 5-10 months) and height values by a factor of six. Building and maintenance costs of the nursery were low. This nursery prototype demonstrates the feasibility of the coral ''gardening concept'' by fulfilling several important needs, namely, mass production of coral colonies at low costs, high survivorship, fast growth, short nursery phase and improved methodologies for handling farmed colonies.

FEMS Microbiology Letters, 2002

Two relatively low-copy plasmids of 9 and 16 kb were found to comprise the extrachromosomal DNA o... more Two relatively low-copy plasmids of 9 and 16 kb were found to comprise the extrachromosomal DNA of a Paracoccus strain. Reduction of nitrate by plasmid-cured cells resulted in a significant intermediate nitrite accumulation as compared to wild-type cells. By examining nitrate reduction by transformants containing one of the two plasmids, it was found that nitrite accumulation was influenced by the 9.0-kb plasmid, designated as pYR1. Subcloning analysis showed that a 1.8-kb fragment of this plasmid affected nitrite accumulation. Sequence analysis of this fragment revealed the presence of five open reading frames. One of the six deduced proteins showed a strong homology to ABC transporters.

FEMS Microbiology Letters, 2006

In this study, microscopic and molecular microbial analyses were integrated to characterize rapid... more In this study, microscopic and molecular microbial analyses were integrated to characterize rapidly developing white filamentous tufts in a fluidized bed reactor used for nitrate removal from a marine recirculating fish culture system. Formation and rapid elongation of the tufts (often exceeding 50 mm day À1 ) was strongly correlated to transient elevated sulfide concentrations ( 4 50 mM) in the reactor. The dominant bacterial constituents of these tufts were filamentous gram-negative bacteria with densely packed intracellular sulfur granules. Using 16S rRNA gene analysis and fluorescence in situ hybridization it was found that these filamentous bacteria represented a novel Thiothrix phylotype closely related (97% sequence identity) to a previously identified Thiothrix strain endogenous to the marine crustacean Urothoe poseidonis. In addition to filamentous morphotypes, rosetteshaped morphotypes of Thiothrix were also detectable within the tufts.

FEMS Microbiology Ecology, 2000

Zero-discharge marine aquaculture systems are an environmentally friendly alternative to conventi... more Zero-discharge marine aquaculture systems are an environmentally friendly alternative to conventional aquaculture. In these systems, water is purified and recycled via microbial biofilters. Here, quantitative data on nitrifier community structure of a trickling filter biofilm associated with a recirculating marine aquaculture system are presented. Repeated rounds of the full-cycle rRNA approach were necessary to optimize DNA extraction and the probe set for FISH to obtain a reliable and comprehensive picture of the ammonia-oxidizing community. Analysis of the ammonia monooxygenase gene (amoA) confirmed the results. The most abundant ammonia-oxidizing bacteria (AOB) were members of the Nitrosomonas sp. Nm143-lineage (6.7% of the bacterial biovolume), followed by Nitrosomonas marina-like AOB (2.2% of the bacterial biovolume). Both were outnumbered by nitrite-oxidizing bacteria of the Nitrospira marinalineage (15.7% of the bacterial biovolume). Although more than eight other nitrifying populations were detected, including Crenarchaeota closely related to the ammonia-oxidizer 'Nitrosopumilus maritimus' , their collective abundance was below 1% of the total biofilm volume; their contribution to nitrification in the biofilter is therefore likely to be negligible.

FEMS Microbiology Ecology, 2010

The effect of NO 3 À addition on dissimilatory SO 4 2À reduction and sulfide conversion in organi... more The effect of NO 3 À addition on dissimilatory SO 4 2À reduction and sulfide conversion in organic-rich sludge from the digestion basin of a recirculating marine aquaculture system was studied. SO 4 2À reduction could only explain a minor fraction (up to 4-9%) of the observed total sulfide production (up to 35 mmol L À1 day À1 ), indicating that the main source of sulfide in the sludge was not SO 4 2À reduction, but desulfuration during the decomposition of organic matter. Although NO 3 À inhibited SO 4 2À reduction, but not desulfuration, the primary NO 3 À mitigation effect was the onset of NO 3 À -mediated sulfide oxidation (up to 75 mmol L À1 day À1 ), partially to elemental sulfur (S 0 ). Above NO 3 À concentrations of 0.6 mM in the bulk water, the net sulfide production and oxidation zones were moved deeper into flocs and sludge cores, which effectively prevented sulfide from entering the water column. However, the sulfide efflux from the sludge instantly recovered after NO 3 À depletion. Thus, the NO 3 À level in the water column controls the zonation and magnitude of sulfur transformations in the sludge. The effect of NO 3 À relies therefore on its sustained presence in the water column, which in turn depends on a well-functioning nitrification in the mariculture system. Fig. 4. Concentration profiles (a) of total sulfide, O 2 (diamonds) and pH in sludge cores from the full-scale DB at different NO 3 À levels in the overlying water. Average profiles of at least two measurements in cores from different positions in the DB are shown; error bars were omitted for clarity. Volumespecific net sulfide conversion rates (b) at 0.1 (hatched bars) and 4.5 mM (open bars) NO 3 À in the bulk water based on the corresponding microprofiles in (a). Zero depth indicates the sludge-water interface.

Environmental Science & Technology, 2007

Aquaculture, 2003

... reactor (5 g biofilm−coated sand), the trickling filter (6 cm 2 of biofilm−coated PVC), the .... more ... reactor (5 g biofilm−coated sand), the trickling filter (6 cm 2 of biofilm−coated PVC), the ... Dry weight of particulate material was determined after overnight drying at 105 °C. ... 3). Total phosphorus in the various treatment compartments showed that phosphorus did not accumulate in ...

Aquaculture, 1997

The accumulation of organic solids in aquaculture systems is influenced to a large extent by the ... more The accumulation of organic solids in aquaculture systems is influenced to a large extent by the decay rates of the recalcitrant compounds comprising these solids. Exponential models based on one degradation constant often provide an inadequate prediction of long-term ...

Aquaculture, 1995

Removal of organic matter and nitrate was studied in a laboratory-scale treatment system consisti... more Removal of organic matter and nitrate was studied in a laboratory-scale treatment system consisting of a digestion basin and a fluidized bed reactor. Fish feed was anaerobically degraded in the digestion basin and supernatant from the digestion basin, rich in dissolved organic degradation products, was used to fuel nitrate removal by denitrifying organisms in the fluidized bed reactor. Anaerobic digestion of the feed was determined in-situ using nylon-mesh bags. Feed degradation was described by considering the feed to consist of two fractions: a labile, rapidly degradable fraction and a recalcitrant, slowly degradable fraction. By using first-order kinetics, the degradation rate constants of each of these fractions were obtained allowing a quantitative prediction of sludge accumulation in the digestion basin. It was predicted that degradation rates and accumulation rates of sludge reached equilibrium after approximately 400 days of operation. The amount of sludge at equilibrium was approximately 23 times the weight of the feed which was added daily. The release of volatile fatty acids during fermentation of fish feed and sludge was determined as it is these organic compounds that mediate the denitrifying activity in the fluidized bed reactor. Predicted values for sludge accumulation and volatile fatty acid release were in agreement with measured values.

Modern Agriculture and the Environment, 1997

Water Research, 2011

Alkalinity DIC a b s t r a c t Interest in mariculture systems will rise in the near future due t... more Alkalinity DIC a b s t r a c t Interest in mariculture systems will rise in the near future due to the decreased ability of the ocean to supply the increasing demand for seafood. We present a trace study using stable carbon and nitrogen isotopes and chemical profiles of a zero-discharge mariculture system stocked with the gilthead seabream (Sparus aurata). Water quality maintenance in the system is based on two biofiltration steps. Firstly, an aerobic treatment step comprising a trickling filter in which ammonia is oxidized to nitrate. Secondly, an anaerobic step comprised of a digestion basin and a fluidized bed reactor where excess organic matter and nitrate are removed. Dissolved inorganic carbon and alkalinity values were higher in the anaerobic loop than in the aerobic loop, in agreement with the main biological processes taking place in the two treatment steps. The d 13 C of the dissolved inorganic carbon (d 13 C DIC ) was depleted in 13 C in the anaerobic loop as compared to the aerobic loop by 2.5e3&. This is in agreement with the higher dissolved inorganic carbon concentrations in the anaerobic loop and the low water retention time and the chemolithotrophic activity of the aerobic loop. The d 13 C and d 15 N of organic matter in the mariculture system indicated that fish fed solely on feed pellets. Compared to feed pellets and particulate organic matter, the sludge in the digestion basin was enriched in 15 N while d 13 C was not significantly different. This latter finding points to an intensive microbial degradation of the organic matter taking place in the anaerobic treatment step of the system. ª

Fish & Shellfish Immunology, 1997

ABSTRACT

Environmental Microbiology, 2003

Bacterial community structure and physiochemical parameters were examined in a sedimentation basi... more Bacterial community structure and physiochemical parameters were examined in a sedimentation basin of a zero-discharge mariculture system. The system consisted of an intensively stocked fish basin from which water was recirculated through two separate treatment loops. Surface water from the basin was pumped over a trickling filter in one loop while bottom-water was recirculated through a sedimentation basin followed by a fluidized bed reactor in the other. Ammonia oxidation to nitrate in the trickling filter and organic matter digestion together with nitrate reduction in the sedimentation basin and fluidized bed reactor, allowed zero-discharge operation of the system. Relatively high concentrations of oxygen, nitrate, sulphate and organic matter detected simultaneously in the digestion basin suggested the potential for a wide range of microbially-mediated transformation processes. In this study, physiochemical parameters were correlated to bacterial diversity and distribution in horizontal and vertical profiles within this basin in an effort to obtain a basic understanding of the chemical and microbial processes in this system. Chemical activity and microbial diversity, the latter measured by denaturing gradient gel electrophoresis (DGGE) analysis of polymerase chain reaction (PCR) amplified 16S rDNA fragments, were higher in the sludge layer than in the overlying aqueous layer of the basin. Chemical parameters in sludge samples close to the basin inlet suggested enhanced microbial activity relative to other sampling areas with evidence of both nitrate and sulphate reduction. Four of the nine DGGE bands identified in this zone were affiliated with the Bacteroidetes phylum. Detected sequences closely related to sequences of organisms involved in the sulphur cycle included Desulfovibrio , Dethiosulfovibrio and apparent sulphur oxidizers from the gamma-proteobacteria. In addition, a number of sequences from the beta and alpha-proteobacteria were identified.

Aquaculture, 1996

... Removal of small suspended solids can be accom plished by either chemical or biological oxida... more ... Removal of small suspended solids can be accom plished by either chemical or biological oxidation. Chemical oxidation by ozonation can be applied to reduce the organic load in conventional waste water treatment (Metcalf and Eddy, 1991). ...

Aquacultural Engineering, 2000

... Aquaculture sludge treatment using anaerobic and facultative lagoon system. In: Libey, GS and... more ... Aquaculture sludge treatment using anaerobic and facultative lagoon system. In: Libey, GS and Timmons, MB Editors, 1996. ... Kuba, T., Smolders, G., van Loosdrecht, MCM and Heijnen, JJ, 1997. A metabolic model for biological phosphorus removal by denitrifying organisms. ...

Applied and Environmental Microbiology, 2000

Polyphosphate accumulation by Paracoccus denitrificans was examined under aerobic, anoxic, and an... more Polyphosphate accumulation by Paracoccus denitrificans was examined under aerobic, anoxic, and anaerobic conditions. Polyphosphate synthesis by this denitrifier took place with either oxygen or nitrate as the electron acceptor and in the presence of an external carbon source. Cells were capable of poly-␤-hydroxybutyrate (PHB) synthesis, but no polyphosphate was produced when PHB-rich cells were incubated under anoxic conditions in the absence of an external carbon source. By comparison of these findings to those with polyphosphateaccumulating organisms thought to be responsible for phosphate removal in activated sludge systems, it is concluded that P. denitrificans is capable of combined phosphate and nitrate removal without the need for alternating anaerobic/aerobic or anaerobic/anoxic switches. Studies on additional denitrifying isolates from a denitrifying fluidized bed reactor suggested that polyphosphate accumulation is widespread among denitrifiers.

Aquaculture, 2003

... reactor (5 g biofilm−coated sand), the trickling filter (6 cm 2 of biofilm−coated PVC), the .... more ... reactor (5 g biofilm−coated sand), the trickling filter (6 cm 2 of biofilm−coated PVC), the ... Dry weight of particulate material was determined after overnight drying at 105 °C. ... 3). Total phosphorus in the various treatment compartments showed that phosphorus did not accumulate in ...

Water Research, 2008

A v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w... more A v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / w a t r e s 0043-1354/$ -see front matter ª w a t e r r e s e a r c h 4 2 ( 2 0 0 8 ) 4 3 8 6 -4 3 9 2

Water Research, 2009

In a previous study on a recirculating fish culture system, levels of geosmin and 2-methylisoborn... more In a previous study on a recirculating fish culture system, levels of geosmin and 2-methylisoborneol were found to decrease when culture water was recirculated through the anaerobic sludge digestion treatment stage of the system. This finding led us to the present study in which the geosmin and 2-methylisoborneol removal capacity of the sludge derived from this treatment stage was examined in vitro. It was found that reduction of off-flavor compounds by the sludge was mediated by both chemical/physical sorption and biological degradation. At geosmin and 2-methylisoborneol concentrations within the range of those experienced in fish culture systems, chemical/physical sorption by the sludge was found to account for a 93% reduction in geosmin and a 79% reduction in 2-methylisoborneol from the overlying water within 48h of incubation. Combined with the biological degradation taking place in the sludge, a complete removal of these compounds from the water phase occurred within 9 days of incubation. By means of repeated washing of the geosmin and 2-methylisoborneol contaminate sludge with clean water, relatively small amounts of these compounds were released from the sludge, a possible indication for the fact that absorption, rather than adsorption, underlies the chemical/physical removal process.

Biomolecular Engineering, 2003

While there is an urgent demand to establish reliable ecotoxicological assays for reef corals, th... more While there is an urgent demand to establish reliable ecotoxicological assays for reef corals, there has not been yet an available source material that can supply the high number of colony replicates needed for reliable tests. In past experiments, the major obstacle to obtaining as many fragments as possible had been the damage inflicted to donor colonies by pruning. In this paper, we present the application of coral nubbins, a novel source material for coral ecotoxicology assays. Nubbins from the branching Red Sea coral Stylophora pistillata (n /450) were used for evaluating the impacts of water soluble fractions from a crude oil, an oil dispersant and dispersed oil. Coral nubbins (minute coral fragments in the size of one to several polyps) harvested from a single colony are genetically identical to each other, may be obtained in any quantity needed and whenever research activities demand their use. Several dozens of nubbins can be obtained from a single small branch in branching coral species, a procedure that has minimal impact on donor genotypes. Nubbins production is a low cost procedure and requires limited maintenance space. Results of short and long-term acute ecotoxicological tests are revealed and discussed here, indicating the advantageous use of nubbins as ubiquitous coral material for toxicology assays and physiological studies. #

Marine Biology, 2006

Many coral reefs worldwide are rapidly declining, but efficient restoration techniques are not ye... more Many coral reefs worldwide are rapidly declining, but efficient restoration techniques are not yet available. Here, we evaluate methodologies for reef restoration based on the ''gardening concept''. A floating mid-water prototype nursery was placed at 6 m depth (14 m above sea-bottom) within the nutrient-enriched environment of a fish farm (Eilat, Red Sea). Ten colonies from five branching coral species provided 6,813 fragments (0.5-3 cm height). The fragments, each attached to a plastic pin, were inserted into plastic nets that were tied to a rope-net floating nursery. After 144 nursery days, only 13.1% of the fragments died and 21.2% were detached by mechanical forces. Small colonies ready for transplantation developed within 144-200 days. Ramets' ecological volumes increased 13-46 folds and their heights by a factor of 3.5. After 306 days, the ecological volumes of the colonies increased 147-163 fold as compared to original volumes (revealing a daily growth rate constant of 1.67% during the first 5-10 months) and height values by a factor of six. Building and maintenance costs of the nursery were low. This nursery prototype demonstrates the feasibility of the coral ''gardening concept'' by fulfilling several important needs, namely, mass production of coral colonies at low costs, high survivorship, fast growth, short nursery phase and improved methodologies for handling farmed colonies.

FEMS Microbiology Letters, 2002

Two relatively low-copy plasmids of 9 and 16 kb were found to comprise the extrachromosomal DNA o... more Two relatively low-copy plasmids of 9 and 16 kb were found to comprise the extrachromosomal DNA of a Paracoccus strain. Reduction of nitrate by plasmid-cured cells resulted in a significant intermediate nitrite accumulation as compared to wild-type cells. By examining nitrate reduction by transformants containing one of the two plasmids, it was found that nitrite accumulation was influenced by the 9.0-kb plasmid, designated as pYR1. Subcloning analysis showed that a 1.8-kb fragment of this plasmid affected nitrite accumulation. Sequence analysis of this fragment revealed the presence of five open reading frames. One of the six deduced proteins showed a strong homology to ABC transporters.

FEMS Microbiology Letters, 2006

In this study, microscopic and molecular microbial analyses were integrated to characterize rapid... more In this study, microscopic and molecular microbial analyses were integrated to characterize rapidly developing white filamentous tufts in a fluidized bed reactor used for nitrate removal from a marine recirculating fish culture system. Formation and rapid elongation of the tufts (often exceeding 50 mm day À1 ) was strongly correlated to transient elevated sulfide concentrations ( 4 50 mM) in the reactor. The dominant bacterial constituents of these tufts were filamentous gram-negative bacteria with densely packed intracellular sulfur granules. Using 16S rRNA gene analysis and fluorescence in situ hybridization it was found that these filamentous bacteria represented a novel Thiothrix phylotype closely related (97% sequence identity) to a previously identified Thiothrix strain endogenous to the marine crustacean Urothoe poseidonis. In addition to filamentous morphotypes, rosetteshaped morphotypes of Thiothrix were also detectable within the tufts.

FEMS Microbiology Ecology, 2000

Zero-discharge marine aquaculture systems are an environmentally friendly alternative to conventi... more Zero-discharge marine aquaculture systems are an environmentally friendly alternative to conventional aquaculture. In these systems, water is purified and recycled via microbial biofilters. Here, quantitative data on nitrifier community structure of a trickling filter biofilm associated with a recirculating marine aquaculture system are presented. Repeated rounds of the full-cycle rRNA approach were necessary to optimize DNA extraction and the probe set for FISH to obtain a reliable and comprehensive picture of the ammonia-oxidizing community. Analysis of the ammonia monooxygenase gene (amoA) confirmed the results. The most abundant ammonia-oxidizing bacteria (AOB) were members of the Nitrosomonas sp. Nm143-lineage (6.7% of the bacterial biovolume), followed by Nitrosomonas marina-like AOB (2.2% of the bacterial biovolume). Both were outnumbered by nitrite-oxidizing bacteria of the Nitrospira marinalineage (15.7% of the bacterial biovolume). Although more than eight other nitrifying populations were detected, including Crenarchaeota closely related to the ammonia-oxidizer 'Nitrosopumilus maritimus' , their collective abundance was below 1% of the total biofilm volume; their contribution to nitrification in the biofilter is therefore likely to be negligible.

FEMS Microbiology Ecology, 2010

The effect of NO 3 À addition on dissimilatory SO 4 2À reduction and sulfide conversion in organi... more The effect of NO 3 À addition on dissimilatory SO 4 2À reduction and sulfide conversion in organic-rich sludge from the digestion basin of a recirculating marine aquaculture system was studied. SO 4 2À reduction could only explain a minor fraction (up to 4-9%) of the observed total sulfide production (up to 35 mmol L À1 day À1 ), indicating that the main source of sulfide in the sludge was not SO 4 2À reduction, but desulfuration during the decomposition of organic matter. Although NO 3 À inhibited SO 4 2À reduction, but not desulfuration, the primary NO 3 À mitigation effect was the onset of NO 3 À -mediated sulfide oxidation (up to 75 mmol L À1 day À1 ), partially to elemental sulfur (S 0 ). Above NO 3 À concentrations of 0.6 mM in the bulk water, the net sulfide production and oxidation zones were moved deeper into flocs and sludge cores, which effectively prevented sulfide from entering the water column. However, the sulfide efflux from the sludge instantly recovered after NO 3 À depletion. Thus, the NO 3 À level in the water column controls the zonation and magnitude of sulfur transformations in the sludge. The effect of NO 3 À relies therefore on its sustained presence in the water column, which in turn depends on a well-functioning nitrification in the mariculture system. Fig. 4. Concentration profiles (a) of total sulfide, O 2 (diamonds) and pH in sludge cores from the full-scale DB at different NO 3 À levels in the overlying water. Average profiles of at least two measurements in cores from different positions in the DB are shown; error bars were omitted for clarity. Volumespecific net sulfide conversion rates (b) at 0.1 (hatched bars) and 4.5 mM (open bars) NO 3 À in the bulk water based on the corresponding microprofiles in (a). Zero depth indicates the sludge-water interface.

Environmental Science & Technology, 2007

Aquaculture, 2003

... reactor (5 g biofilm−coated sand), the trickling filter (6 cm 2 of biofilm−coated PVC), the .... more ... reactor (5 g biofilm−coated sand), the trickling filter (6 cm 2 of biofilm−coated PVC), the ... Dry weight of particulate material was determined after overnight drying at 105 °C. ... 3). Total phosphorus in the various treatment compartments showed that phosphorus did not accumulate in ...

Aquaculture, 1997

The accumulation of organic solids in aquaculture systems is influenced to a large extent by the ... more The accumulation of organic solids in aquaculture systems is influenced to a large extent by the decay rates of the recalcitrant compounds comprising these solids. Exponential models based on one degradation constant often provide an inadequate prediction of long-term ...

Aquaculture, 1995

Removal of organic matter and nitrate was studied in a laboratory-scale treatment system consisti... more Removal of organic matter and nitrate was studied in a laboratory-scale treatment system consisting of a digestion basin and a fluidized bed reactor. Fish feed was anaerobically degraded in the digestion basin and supernatant from the digestion basin, rich in dissolved organic degradation products, was used to fuel nitrate removal by denitrifying organisms in the fluidized bed reactor. Anaerobic digestion of the feed was determined in-situ using nylon-mesh bags. Feed degradation was described by considering the feed to consist of two fractions: a labile, rapidly degradable fraction and a recalcitrant, slowly degradable fraction. By using first-order kinetics, the degradation rate constants of each of these fractions were obtained allowing a quantitative prediction of sludge accumulation in the digestion basin. It was predicted that degradation rates and accumulation rates of sludge reached equilibrium after approximately 400 days of operation. The amount of sludge at equilibrium was approximately 23 times the weight of the feed which was added daily. The release of volatile fatty acids during fermentation of fish feed and sludge was determined as it is these organic compounds that mediate the denitrifying activity in the fluidized bed reactor. Predicted values for sludge accumulation and volatile fatty acid release were in agreement with measured values.