Climate influences populations through a variety of processes. One mechanism that may be particul... more Climate influences populations through a variety of processes. One mechanism that may be particularly important is the role of climate in disrupting un-equally the phenology of the predator and prey in a food chain. The match-mismatch hypothesis, referring to the development and survival of a predator is affected by the synchrony with its prey is used to describe climate effects on ecological patterns and processes in both terrestrial and marine systems. We expand on the match-mismatch hypothesis by considering the simple statement: “what is bad for the predator should be good for the prey”. In other word we reversed the output of the match-mismatch hypothesis, i.e., the increase of the asynchrony lead to a better survival/recruitment for the prey. We tested the theoretical model using GAM models on marine time series. We showed that the effect of predators on prey in the top-down controlled ecosystems can be modified by the degree of asynchrony. We discuss this result in light of t...
1 Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biology, University of O... more 1 Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biology, University of Oslo, P.O. Box 1066 Blindern, N-0316 Oslo, Norway. e-mail: [email protected], [email protected], [email protected] 2 Institute of Marine Research, Flødevigen Marine Research Station, N-4817 His, Norway. email: [email protected], [email protected] 3 Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02882, USA. e-mail: [email protected], [email protected] 4 Centre National de la Recherche Scientifique (CNRS), Laboratoire d’Océanologie et de Géosciences, UMR LOG CNRS 8187, Université des Sciences et Technologies Lille, 1 BP 80, 62930 Wimereux, France. e-mail: [email protected] 5 Sir Alister Hardy Foundation for Ocean Science, The Laboratory, Citadel Hill, Plymouth PL12PB, UK 6 University of Agder, 4604 Kristiansand, Norway † current address: Norwegian Institute for Water Research (NIVA) Gaustadalléen 21, N-0349 Oslo, Norwa...
The use of monitoring data in scientific research is often limited to the purpose for which they ... more The use of monitoring data in scientific research is often limited to the purpose for which they have been collected. However, integrating different sets of data can significantly increase our ability to investigate and quantify processes and dynamics observed in the marine environment. In this research, we illustrate the relevance of existing data for answering long lasting environmental research questions. We performed a meta-analysis of three existing datasets to infer spatial patterns of anthropogenic chemicals in Norwegian marine sediments. We related these patterns to different potential pollution sources. To do so, we integrated 5036 existing data entries of concentrations of chemicals of the Norwegian Institute for Water Research, the Institute of Marine Research, and the Geological Survey of Norway that were collected at 333 sampling locations between 1986 and 2014. These data were analyzed with regression-based models and we found that atmospheric inputs are the main sourc...
• Stressor-response relationships for WFD lake assessment metrics are often poor. • We estimated ... more • Stressor-response relationships for WFD lake assessment metrics are often poor. • We estimated phosphorus runoff from the adjacent land from CORINE land use. • Lakes with high P-runoff did not have higher water nutrient concentrations. • Diatom indices were correlated with P-runoff but not with water chemistry. • High primary producer biomass seemed to reduce dissolved nutrient concentrations. Biological assessment metrics and water chemistry measurements are used to quantify the link between stressors and their effects on lake ecosystems, for the Water Framework Directive. However, correlations between metrics and water chemistry are often poor. This is seen as major weaknesses of Water Framework Directive-related monitoring and assessment. We analyzed macrophytes, benthic algae, benthic macroinvertebrates, water chemistry and sediment total phosphorus content in the littoral of six lakes in the Western Balkans and used CORINE land use data to estimate nutrient enrichment via runoff from the adjacent land. Lakes with a higher estimated phosphorus runoff from the adjacent land did not have higher littoral water nutrient concentrations, but littoral diatom assemblages indicated more eutrophic conditions. These lakes also had higher abundances of littoral benthic primary producers, which in turn were associated with low concentrations of dissolved nutrients, but only in autumn, not in spring. This is consistent with primary producers taking up nutrients during the summer growth season. In lakes with high abundances of benthic primary producers, it is likely that the littoral vegetation plays a large role in the transfer of nutrients from the water to the benthos. This process impairs correlations between biological met-rics and water nutrient concentrations. Our results suggest that CORINE land cover may be more useful to characterize littoral nutrient enrichment than lake water chemistry. Increased benthic primary producer biomasses and "eutrophic" diatom indices may indicate littoral nutrient enrichment even if water nutrient concentrations are low.
Proceedings of the Royal Society B: Biological Sciences
While many in-laboratory ecotoxicological studies have shown the adverse impact of pollutants to ... more While many in-laboratory ecotoxicological studies have shown the adverse impact of pollutants to the fitness of an individual, direct evidence from the field on the population dynamics of wildlife animals has been lacking. Here, we provide empirical support for a negative effect of pollution on Atlantic cod (Gadus morhua) population dynamics in coastal waters of Norway by combining unique time series of juvenile cod abundance, body size, environmental concentration of toxic contaminants and a spatially structured population dynamics model. The study shows that mercury concentration might have decreased the reproductive potential of cod in the region despite the general decline in the environmental concentration of mercury, cadmium and hexachlorobenzene since the implementation of national environmental laws. However, some cod populations appeared to be more resistant to mercury pollution than others, and the strength and shape of mercury effect on cod reproductive potential was fjord-specific. Additionally, cod growth rate changed at scales smaller than fjords with a gradient related to the exposure to the open ocean and offshore cod. These spatial differences in life-history traits emphasize the importance of local adaptation in shaping the dynamics of local wildlife populations. Finally, this study highlights the possibility to mitigate pollution effects on natural populations by reducing the overall pollution level, but also reveals that pollution reduction alone is not enough to rebuild local cod populations. Cod population recovery probably requires complementary efforts on fishing regulation and habitat restoration.
Abstract To test if phytobenthic algae provide additional important information to macrophytes an... more Abstract To test if phytobenthic algae provide additional important information to macrophytes and phytoplankton for lake monitoring, we sampled two large lakes in Norway. In each lake, we analyzed water chemistry and phytoplankton above the deepest site, recorded macrophytes and non-diatom phytobenthic algae at 20 sites around the shoreline and estimated site-specific nutrient input from land cover. Since no ready-to-use phytobenthos index exists for lakes in Norway, we tested the PIT index developed for rivers, commonly perceived signs of disturbance such as high algal cover, and taxon richness as well as similarity patterns. Both lakes were nutrient poor, but had potential local nutrient inputs (villages, agriculture). In neither of the lakes did phytobenthos indicate a worse overall ecological status than macrophytes and phytoplankton. Our data therefore, did not suggest that it would be useful to add phytobenthos into surveillance monitoring of lakes in Norway. There was a loose correlation between macrophyte and phytobenthic site-specific taxon richness and similarities. This means that macrophytes and phytobenthos do indeed give partly redundant information. High algal cover was found at sites with both high and low phosphorus input. Using algal cover as indicator of site-specific nutrient input is therefore overly simplistic. Urban and cultivated areas were associated with a more eutrophic PIT. This indicates that the PIT, despite being developed for lotic waters, may be used to detect site specific nutrient input in lakes.
We characterized spatial patterns of surface sediment concentrations of seven polychlorinated bip... more We characterized spatial patterns of surface sediment concentrations of seven polychlorinated biphenyls (PCBs), seven polycyclic aromatic hydrocarbons (PAHs), three chlorinated pesticides, and five metals in Norwegian waters and Skagerrak. In total, we analyzed 5036 concentrations of 22 chemical substances that were measured between 1986 and 2014 at 333 sampling sites by means of generalized additive models (GAMs). We found that GAMs with organic carbon content of the sediment and latitude and longitude as co-variates explained as ca. 75% of the variability of the contaminant sediment concentrations. For metals, a predominantly hotspot-driven spatial pattern was found, i.e., we identified historical pollution hotspots (e.g., Sørfjord in western Norway) for mercury, zinc, cadmium, and lead. Highest concentrations of PAHs and PCBs were found close to densely populated and industrialized regions, i.e., in the North Sea and in the Kattegat and Skagerrak. The spatial pattern of the PCBs ...
The Pacific oyster, Crassostrea gigas, was introduced to Europe for aquaculture purposes, and has... more The Pacific oyster, Crassostrea gigas, was introduced to Europe for aquaculture purposes, and has had a rapid and unforeseen northward expansion in northern Europe. The recent dramatic increase in number of C. gigas populations along the species' northern distribution limit has questioned the efficiency of Skagerrak as a dispersal barrier for transport and survival of larvae. We investigated the genetic connectivity and possible spreading patterns between Pacific oyster populations on the southern Norwegian coast (4 localities) and Swedish and Danish populations by means of DNA microsatellite analysis of adult oysters, and by simulating larvae drift. In the simulations we used a 3D oceanographic model to explore the influence of recent climate change (1990-2010) on development, survival, and successful spreading of Danish and Swedish Pacific oyster larvae to Norwegian coastal waters. The simulations indicated adequate temperature conditions for development, survival, and settlem...
Mercury (Hg) in Atlantic cod (Gadus morhua) is one of many parameters that are monitored through ... more Mercury (Hg) in Atlantic cod (Gadus morhua) is one of many parameters that are monitored through OSPAR's Joint Assessment and Monitoring Programme. Time series for cod in the Inner Oslofjord (Norway) go back to 1984. Until 2014, annual median Hg-concentrations in cod from the Inner Oslofjord showed both significant upward long-term (whole time series) and short-term (recent 10 years) trends (when 2015 was included, the short-term trend was not significant). However, the median length of the cod sampled also showed upward trends. This may have been caused by low cod recruitment in the area since the start of the 2000s, as indicated by beach seine surveys. To investigate how length would impact the trend analysis, the Hg-concentrations in the cod were normalised to 50 cm. No significant short-term trend in Hg-concentrations could be detected for length-normalised concentrations. The results indicated that most of the upward trend in Hg-concentrations could be attributed to the sam...
Contaminant bioaccumulation was studied in blue mussels (Mytilus edulis spp.) using the harbor wa... more Contaminant bioaccumulation was studied in blue mussels (Mytilus edulis spp.) using the harbor waters of Kristiansand (Norway) as a case study. A suite of chemical contaminants (trace metals, PAHs and PCBs) was analyzed in caged and native mussels as well as in passive samplers (Diffusive Gradients in Thin films (DGT)-devices and silicone rubbers) placed alongside the mussels for estimation of contaminant concentrations in water and uptake rates and bioaccumulation factors (BAFs) in mussels during a six-months deployment period. Estimated logBAFs were in the ranges 2.3-5.5, 3.8-5.2 and 3.2-4.4 for metals, PCBs and PAHs, respectively. Contaminant levels in caged mussels increased rapidly to stable levels for trace metals, whereas for hydrophobic organic contaminants the increase was steady but slow and for many compounds did not reach the levels observed in native mussels. Some key issues related to mussel caging design, such as mussel deployment time and confounding influence from s...
The Pacific oyster, Crassostrea gigas, is an invasive species with a large increase in prevalence... more The Pacific oyster, Crassostrea gigas, is an invasive species with a large increase in prevalence globally, and with potential of spreading even more because of climate-change effects. We examined how future climate might affect its potential for spread at its northern distribution limit in a temperate ecoregion, by simulating spawning, larval dispersal, larvae settlement and adult survival, given different climate scenarios. The simulations were performed using a three-dimensional current model (GEMSS) and a specially designed oyster module, applied at the study site in the Oslofjord, Norway. The simulations showed that the expected climate in the middle and latter part of this century, with warmer summers and winters, very likely will lead to increased prevalence of the species within northern Europe. The warmer summers will more often provide favourable temperature conditions for oyster spawning and settlement, and warmer winters will more seldom cause high winter mortality. The ...
Chara has been suggested a good model to study uptake of xenobiotics into cytoplasm due to their ... more Chara has been suggested a good model to study uptake of xenobiotics into cytoplasm due to their large internode cells surrounded by a layer of cortex cells. We studied the uptake and elimination of pyrene (nominal concentration of 5 μg L(-1)) in the freshwater alga Chara rudis during 22 days in two treatments mimicking epilimnetic (warm and light) and hypolimnetic (cold and dark) conditions. The growth of Chara during the exposure was higher in epilimnetic conditions (40%) compared to both hypolimnetic pyrene exposed Chara and controls (epilimnetic and hypolimnetic, no pyrene). In the water, a more rapid dissipation of pyrene was observed in epilimnetic conditions, possibly as a result of the increased algal growth. In the cortex, pyrene, 1-OH-pyrene (minor metabolite) and an unknown hydrophobic major metabolite was measured. Pyrene amounts decreased over time, while amounts of the unknown metabolite increased. In internode cytoplasm, pyrene and 1-OH-pyrene showed initially increas...
Males of many species of grasshoppers and crickets (Orthoptera) form aggregations when calling fo... more Males of many species of grasshoppers and crickets (Orthoptera) form aggregations when calling for females. However, to our knowledge it has not been reported that the males' spatial position within aggregation correlates with mating success, such as in many species of lekking birds and mammals. Males of the wart-biter Decticus verrucivorus, a bush-cricket (Tettiginiidae), are attracted by other males' song and so have an innate tendency to aggregate. They also provide no parental care. Their mating system therefore resembles a lek (but not a "classical" lek, since males hold floating territories). In this experiment, I "created" animals of good and poor condition by rearing approximately half of the animals under suboptimal conditions. The animals were released in equal density in eight experimental patches of three sizes (20, 40 and 80 m 2), and subsequently tracked by recording their positions four times per day during three weeks. Males that were raised under suboptimal conditions moved less, sang less and had lower song amplitude than the other animals, confirming that they were of poorer condition. The movement patterns revealed that in medium-sized patches, poor-condition animals of both sexes stayed more in the edge zone (< 1 m from habitat edge) than expected by chance, while good-condition animals used the edge zone and interior equally much. The same tendency was found in the only small patch with good-condition animals during most of the experiment. During the peak hours of male singing, however, poor-conditioned females (but not poor-conditioned males) moved towards the center of the patch, where predominantly good-condition males were advertising. In the large patches, however, animals used the interior and the periphery equally much regardless of condition. The results indicate that in the small and medium patches, poor-condition males are repelled by males of better condition because they latter sing louder or more frequently. The spatial segretation between good-and poor-condition females was surprising; the most plausible explanation appears to be that females compete for access to attractive males. Wartbiter males may only mate once a day under ideal conditions, and more infrequently under Norwegian climatic conditions. The lack of differences in the edge-interior use in the large patches may be caused by larger habitat area (less need or higher cost of defending the interior) or by larger population size (the optimal behavioral strategy depends on population size). The interaction between condition and patch size is interesting in the light of the excessive habitat fragmentation of many habitats, including the wart-biters' natural habitat.
Climate influences populations through a variety of processes. One mechanism that may be particul... more Climate influences populations through a variety of processes. One mechanism that may be particularly important is the role of climate in disrupting un-equally the phenology of the predator and prey in a food chain. The match-mismatch hypothesis, referring to the development and survival of a predator is affected by the synchrony with its prey is used to describe climate effects on ecological patterns and processes in both terrestrial and marine systems. We expand on the match-mismatch hypothesis by considering the simple statement: “what is bad for the predator should be good for the prey”. In other word we reversed the output of the match-mismatch hypothesis, i.e., the increase of the asynchrony lead to a better survival/recruitment for the prey. We tested the theoretical model using GAM models on marine time series. We showed that the effect of predators on prey in the top-down controlled ecosystems can be modified by the degree of asynchrony. We discuss this result in light of t...
1 Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biology, University of O... more 1 Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biology, University of Oslo, P.O. Box 1066 Blindern, N-0316 Oslo, Norway. e-mail: [email protected], [email protected], [email protected] 2 Institute of Marine Research, Flødevigen Marine Research Station, N-4817 His, Norway. email: [email protected], [email protected] 3 Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02882, USA. e-mail: [email protected], [email protected] 4 Centre National de la Recherche Scientifique (CNRS), Laboratoire d’Océanologie et de Géosciences, UMR LOG CNRS 8187, Université des Sciences et Technologies Lille, 1 BP 80, 62930 Wimereux, France. e-mail: [email protected] 5 Sir Alister Hardy Foundation for Ocean Science, The Laboratory, Citadel Hill, Plymouth PL12PB, UK 6 University of Agder, 4604 Kristiansand, Norway † current address: Norwegian Institute for Water Research (NIVA) Gaustadalléen 21, N-0349 Oslo, Norwa...
The use of monitoring data in scientific research is often limited to the purpose for which they ... more The use of monitoring data in scientific research is often limited to the purpose for which they have been collected. However, integrating different sets of data can significantly increase our ability to investigate and quantify processes and dynamics observed in the marine environment. In this research, we illustrate the relevance of existing data for answering long lasting environmental research questions. We performed a meta-analysis of three existing datasets to infer spatial patterns of anthropogenic chemicals in Norwegian marine sediments. We related these patterns to different potential pollution sources. To do so, we integrated 5036 existing data entries of concentrations of chemicals of the Norwegian Institute for Water Research, the Institute of Marine Research, and the Geological Survey of Norway that were collected at 333 sampling locations between 1986 and 2014. These data were analyzed with regression-based models and we found that atmospheric inputs are the main sourc...
• Stressor-response relationships for WFD lake assessment metrics are often poor. • We estimated ... more • Stressor-response relationships for WFD lake assessment metrics are often poor. • We estimated phosphorus runoff from the adjacent land from CORINE land use. • Lakes with high P-runoff did not have higher water nutrient concentrations. • Diatom indices were correlated with P-runoff but not with water chemistry. • High primary producer biomass seemed to reduce dissolved nutrient concentrations. Biological assessment metrics and water chemistry measurements are used to quantify the link between stressors and their effects on lake ecosystems, for the Water Framework Directive. However, correlations between metrics and water chemistry are often poor. This is seen as major weaknesses of Water Framework Directive-related monitoring and assessment. We analyzed macrophytes, benthic algae, benthic macroinvertebrates, water chemistry and sediment total phosphorus content in the littoral of six lakes in the Western Balkans and used CORINE land use data to estimate nutrient enrichment via runoff from the adjacent land. Lakes with a higher estimated phosphorus runoff from the adjacent land did not have higher littoral water nutrient concentrations, but littoral diatom assemblages indicated more eutrophic conditions. These lakes also had higher abundances of littoral benthic primary producers, which in turn were associated with low concentrations of dissolved nutrients, but only in autumn, not in spring. This is consistent with primary producers taking up nutrients during the summer growth season. In lakes with high abundances of benthic primary producers, it is likely that the littoral vegetation plays a large role in the transfer of nutrients from the water to the benthos. This process impairs correlations between biological met-rics and water nutrient concentrations. Our results suggest that CORINE land cover may be more useful to characterize littoral nutrient enrichment than lake water chemistry. Increased benthic primary producer biomasses and &quot;eutrophic&quot; diatom indices may indicate littoral nutrient enrichment even if water nutrient concentrations are low.
Proceedings of the Royal Society B: Biological Sciences
While many in-laboratory ecotoxicological studies have shown the adverse impact of pollutants to ... more While many in-laboratory ecotoxicological studies have shown the adverse impact of pollutants to the fitness of an individual, direct evidence from the field on the population dynamics of wildlife animals has been lacking. Here, we provide empirical support for a negative effect of pollution on Atlantic cod (Gadus morhua) population dynamics in coastal waters of Norway by combining unique time series of juvenile cod abundance, body size, environmental concentration of toxic contaminants and a spatially structured population dynamics model. The study shows that mercury concentration might have decreased the reproductive potential of cod in the region despite the general decline in the environmental concentration of mercury, cadmium and hexachlorobenzene since the implementation of national environmental laws. However, some cod populations appeared to be more resistant to mercury pollution than others, and the strength and shape of mercury effect on cod reproductive potential was fjord-specific. Additionally, cod growth rate changed at scales smaller than fjords with a gradient related to the exposure to the open ocean and offshore cod. These spatial differences in life-history traits emphasize the importance of local adaptation in shaping the dynamics of local wildlife populations. Finally, this study highlights the possibility to mitigate pollution effects on natural populations by reducing the overall pollution level, but also reveals that pollution reduction alone is not enough to rebuild local cod populations. Cod population recovery probably requires complementary efforts on fishing regulation and habitat restoration.
Abstract To test if phytobenthic algae provide additional important information to macrophytes an... more Abstract To test if phytobenthic algae provide additional important information to macrophytes and phytoplankton for lake monitoring, we sampled two large lakes in Norway. In each lake, we analyzed water chemistry and phytoplankton above the deepest site, recorded macrophytes and non-diatom phytobenthic algae at 20 sites around the shoreline and estimated site-specific nutrient input from land cover. Since no ready-to-use phytobenthos index exists for lakes in Norway, we tested the PIT index developed for rivers, commonly perceived signs of disturbance such as high algal cover, and taxon richness as well as similarity patterns. Both lakes were nutrient poor, but had potential local nutrient inputs (villages, agriculture). In neither of the lakes did phytobenthos indicate a worse overall ecological status than macrophytes and phytoplankton. Our data therefore, did not suggest that it would be useful to add phytobenthos into surveillance monitoring of lakes in Norway. There was a loose correlation between macrophyte and phytobenthic site-specific taxon richness and similarities. This means that macrophytes and phytobenthos do indeed give partly redundant information. High algal cover was found at sites with both high and low phosphorus input. Using algal cover as indicator of site-specific nutrient input is therefore overly simplistic. Urban and cultivated areas were associated with a more eutrophic PIT. This indicates that the PIT, despite being developed for lotic waters, may be used to detect site specific nutrient input in lakes.
We characterized spatial patterns of surface sediment concentrations of seven polychlorinated bip... more We characterized spatial patterns of surface sediment concentrations of seven polychlorinated biphenyls (PCBs), seven polycyclic aromatic hydrocarbons (PAHs), three chlorinated pesticides, and five metals in Norwegian waters and Skagerrak. In total, we analyzed 5036 concentrations of 22 chemical substances that were measured between 1986 and 2014 at 333 sampling sites by means of generalized additive models (GAMs). We found that GAMs with organic carbon content of the sediment and latitude and longitude as co-variates explained as ca. 75% of the variability of the contaminant sediment concentrations. For metals, a predominantly hotspot-driven spatial pattern was found, i.e., we identified historical pollution hotspots (e.g., Sørfjord in western Norway) for mercury, zinc, cadmium, and lead. Highest concentrations of PAHs and PCBs were found close to densely populated and industrialized regions, i.e., in the North Sea and in the Kattegat and Skagerrak. The spatial pattern of the PCBs ...
The Pacific oyster, Crassostrea gigas, was introduced to Europe for aquaculture purposes, and has... more The Pacific oyster, Crassostrea gigas, was introduced to Europe for aquaculture purposes, and has had a rapid and unforeseen northward expansion in northern Europe. The recent dramatic increase in number of C. gigas populations along the species' northern distribution limit has questioned the efficiency of Skagerrak as a dispersal barrier for transport and survival of larvae. We investigated the genetic connectivity and possible spreading patterns between Pacific oyster populations on the southern Norwegian coast (4 localities) and Swedish and Danish populations by means of DNA microsatellite analysis of adult oysters, and by simulating larvae drift. In the simulations we used a 3D oceanographic model to explore the influence of recent climate change (1990-2010) on development, survival, and successful spreading of Danish and Swedish Pacific oyster larvae to Norwegian coastal waters. The simulations indicated adequate temperature conditions for development, survival, and settlem...
Mercury (Hg) in Atlantic cod (Gadus morhua) is one of many parameters that are monitored through ... more Mercury (Hg) in Atlantic cod (Gadus morhua) is one of many parameters that are monitored through OSPAR's Joint Assessment and Monitoring Programme. Time series for cod in the Inner Oslofjord (Norway) go back to 1984. Until 2014, annual median Hg-concentrations in cod from the Inner Oslofjord showed both significant upward long-term (whole time series) and short-term (recent 10 years) trends (when 2015 was included, the short-term trend was not significant). However, the median length of the cod sampled also showed upward trends. This may have been caused by low cod recruitment in the area since the start of the 2000s, as indicated by beach seine surveys. To investigate how length would impact the trend analysis, the Hg-concentrations in the cod were normalised to 50 cm. No significant short-term trend in Hg-concentrations could be detected for length-normalised concentrations. The results indicated that most of the upward trend in Hg-concentrations could be attributed to the sam...
Contaminant bioaccumulation was studied in blue mussels (Mytilus edulis spp.) using the harbor wa... more Contaminant bioaccumulation was studied in blue mussels (Mytilus edulis spp.) using the harbor waters of Kristiansand (Norway) as a case study. A suite of chemical contaminants (trace metals, PAHs and PCBs) was analyzed in caged and native mussels as well as in passive samplers (Diffusive Gradients in Thin films (DGT)-devices and silicone rubbers) placed alongside the mussels for estimation of contaminant concentrations in water and uptake rates and bioaccumulation factors (BAFs) in mussels during a six-months deployment period. Estimated logBAFs were in the ranges 2.3-5.5, 3.8-5.2 and 3.2-4.4 for metals, PCBs and PAHs, respectively. Contaminant levels in caged mussels increased rapidly to stable levels for trace metals, whereas for hydrophobic organic contaminants the increase was steady but slow and for many compounds did not reach the levels observed in native mussels. Some key issues related to mussel caging design, such as mussel deployment time and confounding influence from s...
The Pacific oyster, Crassostrea gigas, is an invasive species with a large increase in prevalence... more The Pacific oyster, Crassostrea gigas, is an invasive species with a large increase in prevalence globally, and with potential of spreading even more because of climate-change effects. We examined how future climate might affect its potential for spread at its northern distribution limit in a temperate ecoregion, by simulating spawning, larval dispersal, larvae settlement and adult survival, given different climate scenarios. The simulations were performed using a three-dimensional current model (GEMSS) and a specially designed oyster module, applied at the study site in the Oslofjord, Norway. The simulations showed that the expected climate in the middle and latter part of this century, with warmer summers and winters, very likely will lead to increased prevalence of the species within northern Europe. The warmer summers will more often provide favourable temperature conditions for oyster spawning and settlement, and warmer winters will more seldom cause high winter mortality. The ...
Chara has been suggested a good model to study uptake of xenobiotics into cytoplasm due to their ... more Chara has been suggested a good model to study uptake of xenobiotics into cytoplasm due to their large internode cells surrounded by a layer of cortex cells. We studied the uptake and elimination of pyrene (nominal concentration of 5 μg L(-1)) in the freshwater alga Chara rudis during 22 days in two treatments mimicking epilimnetic (warm and light) and hypolimnetic (cold and dark) conditions. The growth of Chara during the exposure was higher in epilimnetic conditions (40%) compared to both hypolimnetic pyrene exposed Chara and controls (epilimnetic and hypolimnetic, no pyrene). In the water, a more rapid dissipation of pyrene was observed in epilimnetic conditions, possibly as a result of the increased algal growth. In the cortex, pyrene, 1-OH-pyrene (minor metabolite) and an unknown hydrophobic major metabolite was measured. Pyrene amounts decreased over time, while amounts of the unknown metabolite increased. In internode cytoplasm, pyrene and 1-OH-pyrene showed initially increas...
Males of many species of grasshoppers and crickets (Orthoptera) form aggregations when calling fo... more Males of many species of grasshoppers and crickets (Orthoptera) form aggregations when calling for females. However, to our knowledge it has not been reported that the males' spatial position within aggregation correlates with mating success, such as in many species of lekking birds and mammals. Males of the wart-biter Decticus verrucivorus, a bush-cricket (Tettiginiidae), are attracted by other males' song and so have an innate tendency to aggregate. They also provide no parental care. Their mating system therefore resembles a lek (but not a "classical" lek, since males hold floating territories). In this experiment, I "created" animals of good and poor condition by rearing approximately half of the animals under suboptimal conditions. The animals were released in equal density in eight experimental patches of three sizes (20, 40 and 80 m 2), and subsequently tracked by recording their positions four times per day during three weeks. Males that were raised under suboptimal conditions moved less, sang less and had lower song amplitude than the other animals, confirming that they were of poorer condition. The movement patterns revealed that in medium-sized patches, poor-condition animals of both sexes stayed more in the edge zone (< 1 m from habitat edge) than expected by chance, while good-condition animals used the edge zone and interior equally much. The same tendency was found in the only small patch with good-condition animals during most of the experiment. During the peak hours of male singing, however, poor-conditioned females (but not poor-conditioned males) moved towards the center of the patch, where predominantly good-condition males were advertising. In the large patches, however, animals used the interior and the periphery equally much regardless of condition. The results indicate that in the small and medium patches, poor-condition males are repelled by males of better condition because they latter sing louder or more frequently. The spatial segretation between good-and poor-condition females was surprising; the most plausible explanation appears to be that females compete for access to attractive males. Wartbiter males may only mate once a day under ideal conditions, and more infrequently under Norwegian climatic conditions. The lack of differences in the edge-interior use in the large patches may be caused by larger habitat area (less need or higher cost of defending the interior) or by larger population size (the optimal behavioral strategy depends on population size). The interaction between condition and patch size is interesting in the light of the excessive habitat fragmentation of many habitats, including the wart-biters' natural habitat.
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Papers by Dag Hjermann