Åke Hagström - Academia.edu (original) (raw)
Papers by Åke Hagström
Journal of Water Pollution Control Federation, 1975
Oil spill protection in the Baltic based on investigations into the ecological effects of oil pol... more Oil spill protection in the Baltic based on investigations into the ecological effects of oil pollution and of chemicals used to combat oil spills
Identifikation av Vibrio anguillarum i fisk med hjalp av partiellt sekvenserat 16S rRNA samt en a... more Identifikation av Vibrio anguillarum i fisk med hjalp av partiellt sekvenserat 16S rRNA samt en artspecifik 16S rRNA probe. Oral presentation at Svenska Havsforskarforeningen, Goteborg
Applied and Environmental Microbiology, Jun 1, 1989
The fish pathogen Vibrio anguillarum causes a lethal infection in rainbow trout (Salmo gairdneri)... more The fish pathogen Vibrio anguillarum causes a lethal infection in rainbow trout (Salmo gairdneri). Three different avirulent mutants, constructed by transposon insertion mutagenesis (VAN20 and VAN70) or as antibiotic-resistant mutants (VAN1000), were isolated by screening 200 individual isolated mutants for avirulence. When used as live vaccines, all three avirulent mutants were able to induce protective immunity against the homologous as well as a heterologous strain of V. anguillarum. When VAN1000 was used, protective immunity could be recorded 1 week after bath vaccination with 107 bacteria per ml of water for 30 min. A single-dose immunization was effective for at least 12 weeks. Western immunoblotting showed that strains of V. anguillarum have antigenic determinants in common with Aeromonas strains. Therefore, we tested and confirmed that VAN1000 also was able to induce protective immunity against challenge with Aeromonas salmonicida.
... Vi bliver klogere De seneste par ârtiers forskning i marin eto-logi har ledt til en betydelig... more ... Vi bliver klogere De seneste par ârtiers forskning i marin eto-logi har ledt til en betydelig nuancering af vor opfattelse af havet som ekosytem. ... Pá sin vej ned gennem vandsBJlen danner disse partikler sterre aggregater - marin sne (fi-gur 11) - som synker mod bunden. ...
CHAPTER 8 CRITICAL PROCESSES IN TRANSFORMATION OF NITROGEN AND PHOSPHORUS IN THE PELAGIC ECOSYSTE... more CHAPTER 8 CRITICAL PROCESSES IN TRANSFORMATION OF NITROGEN AND PHOSPHORUS IN THE PELAGIC ECOSYSTEM Åke Hagström, Bosse Norrmun, Sarah Horrigan Johan Wikncr Marine Sciences Res. Center Department of Microbiology State University of New York ...
Marine Ecology Progress Series, 1988
Stimulation of heterotrophic bacterial growth by inorganic nitrogen (nitrate and ammonium) was ob... more Stimulation of heterotrophic bacterial growth by inorganic nitrogen (nitrate and ammonium) was observed in natural assemblages of marine bacteria grown in continuous culture with unsupplemented sea water as primary medium. In the presence of nitrogenous supplements, bacterial numbers increased approximately 3-fold. These results indicate that re-evaluation of the role of heterotrophic bacterioplankton in the pelagic nitrogen cycle may b e necessary.
Effects of oils on Baltic littoral community, as studied in an outdoor model test system. U.S
Key results o f the Medipelagos project, a 30 month collaborative effort involving 7 institutions... more Key results o f the Medipelagos project, a 30 month collaborative effort involving 7 institutions representing 4 European countries, are presented. Research efforts were focused on nutrient dynamics in the N. W. Mediterranean, an issue o f importance not only in terms o f the goal o f MTP (a system model) but also o f immediate relevance to management. The main issues addressed were: determining which o f the macronutrients likely limits production in the N. W. Mediterranean in the spring and summer months, identifying the major pathways o f nutrients within the pelagic food web, and examining the effects o f rapid changes in nutrient concentrations. Results obtained, using different lines o f evidence, strongly support the hypothesis o f phosphorus limitation in the N. W. Mediterranean during summer months. In addition to phytoplankton, bacterial uptake is likely a major nutrient uptake pathway in this system. Excretion by grazers on bacteria and small phytoplankton and viral lysis o f bacteria are probably responsible for most o f the regeneration o f phosphorus in the water column. Rapid changes in nutrient concentrations can lead to rapid changes in the structure o f the pelagic food web. However, the food webs appear to be capable o f quickly reverting back to their previous structure.
Hydrobiologia, Sep 1, 1992
Plankton production in the Bay of Villefranche was relatively constant during March and April 198... more Plankton production in the Bay of Villefranche was relatively constant during March and April 1986 but the particle size at which the production occurred was more variable. At the beginning of the study, production was dominated by the larger (ca. 6 m) flagellates but towards the end it was more or less equally divided between the nano-and picoplankton. There were considerable differences in the estimates of population growth rates, depending on the methods used, but on average the population doubling times were close to 12 hours for autotrophs and 24 hours for heterotrophs. As autotrophs do not grow during the night, each population was therefore doubling once per day. It seemed that each of the nanoor picoplankton populations could adversely affect the growth of the others. This could be either by simple predation or by some form of inhibition. Although nutrient levels in the bay were uniformly low, the addition of nutrients did not always stimulate algal growth. The plankton populations seemed to be both in a state of equilibrium and intense ecological competition.
Aquatic Microbial Ecology, 1999
Coupling between bacterioplankton species composition, population dynamics, and organic matter de... more Coupling between bacterioplankton species composition, population dynamics, and organic matter degradation Jarone pinhassil, Farooq ~z a m~, Johanna ~e m p h a l a~, Richard A. ~o n g~, Josefina ~a r t i n e z~, Ulla Li zweife13, Bike ~a g s t r o r n~l *
Oikos, 1977
Plastic pools (surface6.6m2, volume4.2 M3) were equippedwith aflow-through system providing 2.5 1... more Plastic pools (surface6.6m2, volume4.2 M3) were equippedwith aflow-through system providing 2.5 1 min-1. Except for fish predators the main components of the flora and fauna of the Baltic littoral zone were introduced into the pools to form a model of the ecosystem. During 8 weeks the macroscopic epifauna and infauna of the bladder wrack Fucus vesiculosus L. were found to be qualitatively and quantitatively fairly stable, and the number of aerobic heterotrophic bacteria showed little variation. Oxygen concentration, temperature and pH were recorded and compared with values measured in the littoral zone. The results indicate good agreement between the characters of the model system and of the natural littoral ecosystem. This together with the observed stability and the possibilities forcontrollingand measuringthe conditions inthe system makes us believe that the model is a valuable tool for assessing toxic effects on the littoral ecosystem.
Marine Ecology Progress Series, 1990
In May 1987 multidisciplinary investigations focusing on die1 variations were performed at 4 hori... more In May 1987 multidisciplinary investigations focusing on die1 variations were performed at 4 horizontally stratified (pycnocline at 5 to 12 m) stations in the open Skagerrak (North Sea). Nutrients were lower above the pycnocline than below. Phytoplankton was numerically dominated by flagellates and monads indicating a regenerating plankton community, which was confirmed by the finding that about 80 % of the nitrogen uptake in surface waters was as NH4+ and urea, and about 20 O/O was N o 3-Percentage of 'new' primary production (based on NOIIuptake) was similar to the percentage sedimentation rate (in C) of primary production (ca 20%). Growth of bacteria and grazing on bacteria were systematically dependent on time of day above, in and below the pycnocline. Abundance of bacteria and nanoflagellates was not regularly dependent on time of day, but systematically elevated in the pycnocline, as was chlorophyll a. Zooplankton grazing in the surface water was highest at night and early morning. Benthic investigations indicated heterogeneity in the area For comparison, samples of hydrography, nutrients, phytoplankton abundance and growth, and sedimentation were investigated at the same bme at a coastal station with horizontal stratification and slightly lower salinity. Here 'new' primary production was estimated to about 50 % of total production, based on percentage sedimentation. Nitrogen seemed in general to be in deficit for primary production relative to phosphorus in surface waters both in the open and coastal Skagerrak, but exceptions could occur That nutrients were in surplus just below the shallow pycnocline shows, however, that those primary producers and bacteria whi.ch could utilize this reservoir had access to unlimited nutrient resources at that time. It was estimated that bacteria and flagellates made up > 5 0 % of total pelagic respiration and consumed slightly more than the net primary production.
Aquatic Microbial Ecology, 1996
Cycling of marine dissolved organic matter. I. An experimental system Ulla Li Zweifell, Nicholas ... more Cycling of marine dissolved organic matter. I. An experimental system Ulla Li Zweifell, Nicholas lack burn', Ake ~a g s t r o r n~~'
Aquatic Microbial Ecology, 1999
Coupling between bacterioplankton species composition, population dynamics, and organic matter de... more Coupling between bacterioplankton species composition, population dynamics, and organic matter degradation Jarone pinhassil, Farooq ~z a m~, Johanna ~e m p h a l a~, Richard A. ~o n g~, Josefina ~a r t i n e z~, Ulla Li zweife13, Bike ~a g s t r o r n~l *
Aquatic Microbial Ecology, 2017
Here, we examine the use of bacterial isolates growing in artificial media or seawater as a means... more Here, we examine the use of bacterial isolates growing in artificial media or seawater as a means to investigate bacterial activity in the upper ocean. The discovery of a major role of bacteria in the ocean's carbon cycle owes greatly to the development of culture-independent assemblage-level approaches; however, this should not detract from the recognition of model isolates as representing the environmental microbiome. A long-established tool for culturing bacteria, in medicine and general microbiology, has been agar plates. In addition, a great variety of liquid substrates including seawater have been used to successfully identify and cultivate important bacteria such as Pelagibacter ubique. Yet, the discrepancy between microscopic counts and plate counts, the great plate count anomaly, has led to a biased perception of the limited relevance of isolated bacteria. Linking isolates to whole-genome sequencing, phylogenetic analysis and computational modeling will result in culturable model bacteria from different habitats. Our main message is that bacterial ecophysiology, particularly growth rates in seawater, and functionalities inferred through the identity, abundance and expression of specific genes could be mechanistically linked if more work is done to isolate, culture and study bacteria in pure cultures. When we rally behind a strategy aimed at culturing targeted phenotypes, we are not saying that cultureindependent studies of bacteria in the sea are not informative. We are suggesting that culturebased studies can help integrate the ecological and genomic views.
Journal of Water Pollution Control Federation, 1975
Oil spill protection in the Baltic based on investigations into the ecological effects of oil pol... more Oil spill protection in the Baltic based on investigations into the ecological effects of oil pollution and of chemicals used to combat oil spills
Identifikation av Vibrio anguillarum i fisk med hjalp av partiellt sekvenserat 16S rRNA samt en a... more Identifikation av Vibrio anguillarum i fisk med hjalp av partiellt sekvenserat 16S rRNA samt en artspecifik 16S rRNA probe. Oral presentation at Svenska Havsforskarforeningen, Goteborg
Applied and Environmental Microbiology, Jun 1, 1989
The fish pathogen Vibrio anguillarum causes a lethal infection in rainbow trout (Salmo gairdneri)... more The fish pathogen Vibrio anguillarum causes a lethal infection in rainbow trout (Salmo gairdneri). Three different avirulent mutants, constructed by transposon insertion mutagenesis (VAN20 and VAN70) or as antibiotic-resistant mutants (VAN1000), were isolated by screening 200 individual isolated mutants for avirulence. When used as live vaccines, all three avirulent mutants were able to induce protective immunity against the homologous as well as a heterologous strain of V. anguillarum. When VAN1000 was used, protective immunity could be recorded 1 week after bath vaccination with 107 bacteria per ml of water for 30 min. A single-dose immunization was effective for at least 12 weeks. Western immunoblotting showed that strains of V. anguillarum have antigenic determinants in common with Aeromonas strains. Therefore, we tested and confirmed that VAN1000 also was able to induce protective immunity against challenge with Aeromonas salmonicida.
... Vi bliver klogere De seneste par ârtiers forskning i marin eto-logi har ledt til en betydelig... more ... Vi bliver klogere De seneste par ârtiers forskning i marin eto-logi har ledt til en betydelig nuancering af vor opfattelse af havet som ekosytem. ... Pá sin vej ned gennem vandsBJlen danner disse partikler sterre aggregater - marin sne (fi-gur 11) - som synker mod bunden. ...
CHAPTER 8 CRITICAL PROCESSES IN TRANSFORMATION OF NITROGEN AND PHOSPHORUS IN THE PELAGIC ECOSYSTE... more CHAPTER 8 CRITICAL PROCESSES IN TRANSFORMATION OF NITROGEN AND PHOSPHORUS IN THE PELAGIC ECOSYSTEM Åke Hagström, Bosse Norrmun, Sarah Horrigan Johan Wikncr Marine Sciences Res. Center Department of Microbiology State University of New York ...
Marine Ecology Progress Series, 1988
Stimulation of heterotrophic bacterial growth by inorganic nitrogen (nitrate and ammonium) was ob... more Stimulation of heterotrophic bacterial growth by inorganic nitrogen (nitrate and ammonium) was observed in natural assemblages of marine bacteria grown in continuous culture with unsupplemented sea water as primary medium. In the presence of nitrogenous supplements, bacterial numbers increased approximately 3-fold. These results indicate that re-evaluation of the role of heterotrophic bacterioplankton in the pelagic nitrogen cycle may b e necessary.
Effects of oils on Baltic littoral community, as studied in an outdoor model test system. U.S
Key results o f the Medipelagos project, a 30 month collaborative effort involving 7 institutions... more Key results o f the Medipelagos project, a 30 month collaborative effort involving 7 institutions representing 4 European countries, are presented. Research efforts were focused on nutrient dynamics in the N. W. Mediterranean, an issue o f importance not only in terms o f the goal o f MTP (a system model) but also o f immediate relevance to management. The main issues addressed were: determining which o f the macronutrients likely limits production in the N. W. Mediterranean in the spring and summer months, identifying the major pathways o f nutrients within the pelagic food web, and examining the effects o f rapid changes in nutrient concentrations. Results obtained, using different lines o f evidence, strongly support the hypothesis o f phosphorus limitation in the N. W. Mediterranean during summer months. In addition to phytoplankton, bacterial uptake is likely a major nutrient uptake pathway in this system. Excretion by grazers on bacteria and small phytoplankton and viral lysis o f bacteria are probably responsible for most o f the regeneration o f phosphorus in the water column. Rapid changes in nutrient concentrations can lead to rapid changes in the structure o f the pelagic food web. However, the food webs appear to be capable o f quickly reverting back to their previous structure.
Hydrobiologia, Sep 1, 1992
Plankton production in the Bay of Villefranche was relatively constant during March and April 198... more Plankton production in the Bay of Villefranche was relatively constant during March and April 1986 but the particle size at which the production occurred was more variable. At the beginning of the study, production was dominated by the larger (ca. 6 m) flagellates but towards the end it was more or less equally divided between the nano-and picoplankton. There were considerable differences in the estimates of population growth rates, depending on the methods used, but on average the population doubling times were close to 12 hours for autotrophs and 24 hours for heterotrophs. As autotrophs do not grow during the night, each population was therefore doubling once per day. It seemed that each of the nanoor picoplankton populations could adversely affect the growth of the others. This could be either by simple predation or by some form of inhibition. Although nutrient levels in the bay were uniformly low, the addition of nutrients did not always stimulate algal growth. The plankton populations seemed to be both in a state of equilibrium and intense ecological competition.
Aquatic Microbial Ecology, 1999
Coupling between bacterioplankton species composition, population dynamics, and organic matter de... more Coupling between bacterioplankton species composition, population dynamics, and organic matter degradation Jarone pinhassil, Farooq ~z a m~, Johanna ~e m p h a l a~, Richard A. ~o n g~, Josefina ~a r t i n e z~, Ulla Li zweife13, Bike ~a g s t r o r n~l *
Oikos, 1977
Plastic pools (surface6.6m2, volume4.2 M3) were equippedwith aflow-through system providing 2.5 1... more Plastic pools (surface6.6m2, volume4.2 M3) were equippedwith aflow-through system providing 2.5 1 min-1. Except for fish predators the main components of the flora and fauna of the Baltic littoral zone were introduced into the pools to form a model of the ecosystem. During 8 weeks the macroscopic epifauna and infauna of the bladder wrack Fucus vesiculosus L. were found to be qualitatively and quantitatively fairly stable, and the number of aerobic heterotrophic bacteria showed little variation. Oxygen concentration, temperature and pH were recorded and compared with values measured in the littoral zone. The results indicate good agreement between the characters of the model system and of the natural littoral ecosystem. This together with the observed stability and the possibilities forcontrollingand measuringthe conditions inthe system makes us believe that the model is a valuable tool for assessing toxic effects on the littoral ecosystem.
Marine Ecology Progress Series, 1990
In May 1987 multidisciplinary investigations focusing on die1 variations were performed at 4 hori... more In May 1987 multidisciplinary investigations focusing on die1 variations were performed at 4 horizontally stratified (pycnocline at 5 to 12 m) stations in the open Skagerrak (North Sea). Nutrients were lower above the pycnocline than below. Phytoplankton was numerically dominated by flagellates and monads indicating a regenerating plankton community, which was confirmed by the finding that about 80 % of the nitrogen uptake in surface waters was as NH4+ and urea, and about 20 O/O was N o 3-Percentage of 'new' primary production (based on NOIIuptake) was similar to the percentage sedimentation rate (in C) of primary production (ca 20%). Growth of bacteria and grazing on bacteria were systematically dependent on time of day above, in and below the pycnocline. Abundance of bacteria and nanoflagellates was not regularly dependent on time of day, but systematically elevated in the pycnocline, as was chlorophyll a. Zooplankton grazing in the surface water was highest at night and early morning. Benthic investigations indicated heterogeneity in the area For comparison, samples of hydrography, nutrients, phytoplankton abundance and growth, and sedimentation were investigated at the same bme at a coastal station with horizontal stratification and slightly lower salinity. Here 'new' primary production was estimated to about 50 % of total production, based on percentage sedimentation. Nitrogen seemed in general to be in deficit for primary production relative to phosphorus in surface waters both in the open and coastal Skagerrak, but exceptions could occur That nutrients were in surplus just below the shallow pycnocline shows, however, that those primary producers and bacteria whi.ch could utilize this reservoir had access to unlimited nutrient resources at that time. It was estimated that bacteria and flagellates made up > 5 0 % of total pelagic respiration and consumed slightly more than the net primary production.
Aquatic Microbial Ecology, 1996
Cycling of marine dissolved organic matter. I. An experimental system Ulla Li Zweifell, Nicholas ... more Cycling of marine dissolved organic matter. I. An experimental system Ulla Li Zweifell, Nicholas lack burn', Ake ~a g s t r o r n~~'
Aquatic Microbial Ecology, 1999
Coupling between bacterioplankton species composition, population dynamics, and organic matter de... more Coupling between bacterioplankton species composition, population dynamics, and organic matter degradation Jarone pinhassil, Farooq ~z a m~, Johanna ~e m p h a l a~, Richard A. ~o n g~, Josefina ~a r t i n e z~, Ulla Li zweife13, Bike ~a g s t r o r n~l *
Aquatic Microbial Ecology, 2017
Here, we examine the use of bacterial isolates growing in artificial media or seawater as a means... more Here, we examine the use of bacterial isolates growing in artificial media or seawater as a means to investigate bacterial activity in the upper ocean. The discovery of a major role of bacteria in the ocean's carbon cycle owes greatly to the development of culture-independent assemblage-level approaches; however, this should not detract from the recognition of model isolates as representing the environmental microbiome. A long-established tool for culturing bacteria, in medicine and general microbiology, has been agar plates. In addition, a great variety of liquid substrates including seawater have been used to successfully identify and cultivate important bacteria such as Pelagibacter ubique. Yet, the discrepancy between microscopic counts and plate counts, the great plate count anomaly, has led to a biased perception of the limited relevance of isolated bacteria. Linking isolates to whole-genome sequencing, phylogenetic analysis and computational modeling will result in culturable model bacteria from different habitats. Our main message is that bacterial ecophysiology, particularly growth rates in seawater, and functionalities inferred through the identity, abundance and expression of specific genes could be mechanistically linked if more work is done to isolate, culture and study bacteria in pure cultures. When we rally behind a strategy aimed at culturing targeted phenotypes, we are not saying that cultureindependent studies of bacteria in the sea are not informative. We are suggesting that culturebased studies can help integrate the ecological and genomic views.