Else Hegseth - Academia.edu (original) (raw)
Papers by Else Hegseth
Proceedings of SPIE, Dec 10, 1993
We have investigated the effects of a phytoplankton model of an area in the Barents Sea subject t... more We have investigated the effects of a phytoplankton model of an area in the Barents Sea subject to different ways of specifying the light field. Three different schemes is used to calculate the light available for photosynthesis, (1) non-spectral attenuation of light in the water column, (2) spectral attenuation, and (3) calculating the photosynthetic usable radiation from the spectral scheme. This study also investigates the effects of changes in the spectral distribution under a cloudy sky with an increase in the shortwave radiation and a decrease in radiation at longer wavelengths.
Springer eBooks, 2007
Climate change and ecosystem response 1.3 UV radiation and biological effects 1.4 Ecological impa... more Climate change and ecosystem response 1.3 UV radiation and biological effects 1.4 Ecological impacts of long range pollutants transport 1.5 Integrated aspects 1.6 Conclusions Acknowledgements References 2 An environment at risk: Arctic indigenous peoples, local livelihoods and climate change Mark Nuttall •. 2.1 Introduction 1 2.2 Indigenous Peoples and Traditional Livelihoods 2.3 Renewable Resource Use and Climate Change: Risk and Access to Food Resources 2.4 Concerns Over Irreversible Impacts 2.5 Responding to Climate Change: Flexibility, Adaptation, Barriers and Opportunities 2.6 Conclusions 3 Climate variation in the European sector of the Arctic: Observations and scenarios Inger Hanssen-Bauer viii Arctic-alpine ecosystems and people in a changing environment 3.
Journal of Marine Science and Engineering, 2022
This work summarizes ice algal studies, presented as biomass and species temporal and spatial dis... more This work summarizes ice algal studies, presented as biomass and species temporal and spatial distribution, during 11 cruises conducted between 1986 and 2012. The majority of the biomass was found as loosely attached sub-ice algal layers, and sampling required diving. A maximum of 40 mg chlorophyll m−2 and 15.4 × 109 cells m−2 was measured in May. The species diversity was separated in zones based on ice thickness, with the highest biodiversity in the medium-thick ice of 30–80 cm. Nitzschia frigida was the most common species. There was a significant positive relationship between the dominance of this species and ice thickness, and it dominated completely in thick ice. Other common species, such as N. promare and Fossulaphycus arcticus reacted oppositely, by becoming less dominant in thick ice, but the positive correlation between total cell numbers and number of these three species indicated that they would most likely dominate in most populations. Melosira arctica was found severa...
The spatial variation in mesozooplankton biomass, abundance and species composition in relation t... more The spatial variation in mesozooplankton biomass, abundance and species composition in relation to oceanography was studied in different climatic regimes (warm Atlantic vs. cold Arctic) in northern Svalbard waters. Relationships between the zooplankton community and various environmental factors (salinity, temperature, sampling depth, bottom depth, sea-ice concentrations, algal biomass and bloom stage) were established using multivariate statistics. Our study demonstrated that variability in the physical environment around Svalbard had measurable effect on the pelagic ecosystem. Differences in bottom depth and temperature-salinity best explained more than 40% of the horizontal variability in mesozooplankton biomass (DM/m**2) after adjusting for seasonal variability. Salinity and temperature also explained much (21% and 15%, respectively) of the variability in mesozooplankton vertical distribution (ind./m**3) in August. Algal bloom stage, chlorophyll-a biomass, and depth stratum accounted for additional 17% of the overall variability structuring vertical zooplankton distribution.Three main zooplankton communities were identified, including Atlantic species Fritillaria borealis, Oithona atlantica, Calanus finmarchicus, Themisto abyssorum and Aglantha digitale; Arctic species Calanus glacialis, Gammarus wilkitzkii, Mertensia ovum and Sagitta elegans; and deeper-water inhabitants Paraeuchaeta spp., Spinocalanus spp., Aetideopsis minor, Mormonilla minor, Scolecithricella minor, Gaetanus (Gaidius) tenuispinus, Ostracoda, Scaphocalanus brevicornis and Triconia borealis. Zooplankton biomasses in Atlantic- and Arctic-dominated water masses were similar, but biological ''hot-spots'' were associated with Arctic communities.
The feeding strategies of Calanus hyperboreus, C. glacialis, and C. finmarchicus were investigate... more The feeding strategies of Calanus hyperboreus, C. glacialis, and C. finmarchicus were investigated in the high-Arctic Svalbard region (77-81 °N) in May, August, and December, including seasons with algal blooms, late- to post-bloom situations, and unproductive winter periods. Stable isotope and fatty acid trophic marker (FATM) techniques were employed together to assess trophic level (TL), carbon sources (phytoplankton vs. ice algae), and diet of the three Calanus species. In addition, population development, distribution, and nutritional state (i.e. storage lipids) were examined to estimate their population status at the time of sampling. In May and August, the vertical distribution of the three Calanus species usually coincided with the maximum algal biomass. Their stable isotope and fatty acid (FA) composition indicated that they all were essentially herbivores in May, when the algal biomass was highest. Their FA composition, however, revealed different food preferences. C. hyperboreus had high proportions of 18:4n3, suggesting that it fed mainly on Phaeocystis, whereas C. glacialis and C. finmarchicus had high proportions of 16:4n1, 16:1n7, and 20:5n3, suggesting diatoms as their major food source. Carbon sources (i.e. phytoplankton vs. ice algae) were not possible to determine solely from FATM techniques since ice-diatoms and pelagic-diatoms were characterised by the same FA. However, the enriched d13C values of C. glacialis and C. finmarchicus in May indicated that they fed both on pelagic- and ice-diatoms. Patterns in absolute FA and fatty alcohol composition revealed that diatoms were the most important food for C. hyperboreus and C. glacialis, followed by Phaeocystis, whereas diatoms, Phaeocystis and other small autotrophic flagellates were equally important food for C. finmarchicus. During periods of lower algal biomass, only C. glacialis exhibited evidence of significant dietary switch, with a TL indicative of omnivory (mean TL=2.4). Large spatial variability was observed in population development, dis [...]
Sarsia, 2003
... DOI: 10.1080/00364820310002830 Rasmus Skern a * , Mette Mauritzen b , Nils T ... the aggregat... more ... DOI: 10.1080/00364820310002830 Rasmus Skern a * , Mette Mauritzen b , Nils T ... the aggregating behavior of the green sea urchin Strongylocentrotus droebachiensis (Muller) Journal of Experimental Marine Biology and Ecology 176 107 126 View all references; Christie & al. ...
Climate change and ecosystem response 1.3 UV radiation and biological effects 1.4 Ecological impa... more Climate change and ecosystem response 1.3 UV radiation and biological effects 1.4 Ecological impacts of long range pollutants transport 1.5 Integrated aspects 1.6 Conclusions Acknowledgements References 2 An environment at risk: Arctic indigenous peoples, local livelihoods and climate change Mark Nuttall •. 2.1 Introduction 1 2.2 Indigenous Peoples and Traditional Livelihoods 2.3 Renewable Resource Use and Climate Change: Risk and Access to Food Resources 2.4 Concerns Over Irreversible Impacts 2.5 Responding to Climate Change: Flexibility, Adaptation, Barriers and Opportunities 2.6 Conclusions 3 Climate variation in the European sector of the Arctic: Observations and scenarios Inger Hanssen-Bauer viii Arctic-alpine ecosystems and people in a changing environment 3.
Journal of Marine Systems, 2000
The main physical and ecological processes associated with the summer melt period in the marginal... more The main physical and ecological processes associated with the summer melt period in the marginal ice zone MIZ were Ž. investigated in a multidisciplinary research programme ICE-BAR , which was carried out in the northern Barents Sea during June-August 1995-1996. This study provided simultaneous observations of a wide range of physical and chemical factors of importance for the melting processes of sea ice, from its southernmost margins at about 77.58N to the consolidated Arctic pack ice at 81.58N. This paper includes a description of the oceanographic processes, ice-density packing and structures in cores, optical properties of water masses and the ice, characteristics of the incident spectral radiation and chlorophyll-leading to primary production. Large seasonal and inter-annual variations in ice cover in the MIZ were evident from satellite images as well as ship observations. Even if the annual variation in ice extent may be large, the inter-annual variations may be even larger. The minimum observed ice extent in March, for example, can be smaller than the maximum observed ice extent in September. Oceanographic phenomena such as the semi-permanent lee polynyas found west and southwest of Kvitøya and Franz Josef Land and the bay of open water, the AWhalers BayB, north of the Spitsbergen are structures which can change with time intervals of hours to decades. For example, the polynya south of Franz Josef Land was clearly evident in 1995 but was only seen for a short period in 1996. The observed variability in physical conditions directly affects the primary production in the MIZ. From early spring, solar radiation penetrates both leads and the ice itself, initiating algal production under the ice. Light measurements showed that the melt ponds act as windows, permitting the transmission of incoming solar radiation through to the underlying sea ice, thus, accelerating the melting process and enhancing the under-ice primary production. In June 1995, the N-S transect went through a pre-bloom area well inside the ice-covered part of the Barents Sea to a post-bloom phase in the open waters Ž. south of the ice edge. The biological conditions in the later season August of 1996 were considerably more variable. The
Eos, Transactions American Geophysical Union, 2007
Strengthened highland-lowland linkages improve sustainability for both upstream and downstream po... more Strengthened highland-lowland linkages improve sustainability for both upstream and downstream populations. Lowland-highland relationships, whether formal or informal, have the potential to pay for investments in protection and sustainable use of mountain resources. When full costs are taken into account, stewardship of upland resources generally yields greater and more sustainable economic returns both to the people living in the mountain areas and to the immediate downstream economies when compared with extractive activities. In many cases, the focal point of such interactions has been based on providing a sustainable and clean supply of water, the most important and increasingly limiting mountain resource. In steep terrain, more than anywhere else, catchment quality is intimately linked to ecosystem integrity and functioning. Thus environmental conservation and sustainable land use in the world's mountains are not only a necessary condition for sustainable local livelihoods, they are also key to human well-being for nearly half the world's population who live downstream and depend on mountain resources.
Obviously, the many challenges involving climate and stratospheric change, pollutant transport an... more Obviously, the many challenges involving climate and stratospheric change, pollutant transport and social changes are related. A number of other significant dependencies also naturally exist between the various aspects of environmental change parameters and human activities in arctic and alpine areas. The scope here is not to give a complete review of all single processes but to outline the level of interaction between the main contemporary challenges in environmental change, on the basis of the studies presented in the book. Both with respect to the physical processes as well as dealing with their biological impacts and the anthropogenic forcing factors, the changes related to the climate change processes, long range transported pollutants and UV radiation, can not be treated alone or independently but need to be analysed as multiple pressures of the high latitude and high altitude, arctic and alpine environments.
Proceedings of SPIE, Dec 10, 1993
We have investigated the effects of a phytoplankton model of an area in the Barents Sea subject t... more We have investigated the effects of a phytoplankton model of an area in the Barents Sea subject to different ways of specifying the light field. Three different schemes is used to calculate the light available for photosynthesis, (1) non-spectral attenuation of light in the water column, (2) spectral attenuation, and (3) calculating the photosynthetic usable radiation from the spectral scheme. This study also investigates the effects of changes in the spectral distribution under a cloudy sky with an increase in the shortwave radiation and a decrease in radiation at longer wavelengths.
Springer eBooks, 2007
Climate change and ecosystem response 1.3 UV radiation and biological effects 1.4 Ecological impa... more Climate change and ecosystem response 1.3 UV radiation and biological effects 1.4 Ecological impacts of long range pollutants transport 1.5 Integrated aspects 1.6 Conclusions Acknowledgements References 2 An environment at risk: Arctic indigenous peoples, local livelihoods and climate change Mark Nuttall •. 2.1 Introduction 1 2.2 Indigenous Peoples and Traditional Livelihoods 2.3 Renewable Resource Use and Climate Change: Risk and Access to Food Resources 2.4 Concerns Over Irreversible Impacts 2.5 Responding to Climate Change: Flexibility, Adaptation, Barriers and Opportunities 2.6 Conclusions 3 Climate variation in the European sector of the Arctic: Observations and scenarios Inger Hanssen-Bauer viii Arctic-alpine ecosystems and people in a changing environment 3.
Journal of Marine Science and Engineering, 2022
This work summarizes ice algal studies, presented as biomass and species temporal and spatial dis... more This work summarizes ice algal studies, presented as biomass and species temporal and spatial distribution, during 11 cruises conducted between 1986 and 2012. The majority of the biomass was found as loosely attached sub-ice algal layers, and sampling required diving. A maximum of 40 mg chlorophyll m−2 and 15.4 × 109 cells m−2 was measured in May. The species diversity was separated in zones based on ice thickness, with the highest biodiversity in the medium-thick ice of 30–80 cm. Nitzschia frigida was the most common species. There was a significant positive relationship between the dominance of this species and ice thickness, and it dominated completely in thick ice. Other common species, such as N. promare and Fossulaphycus arcticus reacted oppositely, by becoming less dominant in thick ice, but the positive correlation between total cell numbers and number of these three species indicated that they would most likely dominate in most populations. Melosira arctica was found severa...
The spatial variation in mesozooplankton biomass, abundance and species composition in relation t... more The spatial variation in mesozooplankton biomass, abundance and species composition in relation to oceanography was studied in different climatic regimes (warm Atlantic vs. cold Arctic) in northern Svalbard waters. Relationships between the zooplankton community and various environmental factors (salinity, temperature, sampling depth, bottom depth, sea-ice concentrations, algal biomass and bloom stage) were established using multivariate statistics. Our study demonstrated that variability in the physical environment around Svalbard had measurable effect on the pelagic ecosystem. Differences in bottom depth and temperature-salinity best explained more than 40% of the horizontal variability in mesozooplankton biomass (DM/m**2) after adjusting for seasonal variability. Salinity and temperature also explained much (21% and 15%, respectively) of the variability in mesozooplankton vertical distribution (ind./m**3) in August. Algal bloom stage, chlorophyll-a biomass, and depth stratum accounted for additional 17% of the overall variability structuring vertical zooplankton distribution.Three main zooplankton communities were identified, including Atlantic species Fritillaria borealis, Oithona atlantica, Calanus finmarchicus, Themisto abyssorum and Aglantha digitale; Arctic species Calanus glacialis, Gammarus wilkitzkii, Mertensia ovum and Sagitta elegans; and deeper-water inhabitants Paraeuchaeta spp., Spinocalanus spp., Aetideopsis minor, Mormonilla minor, Scolecithricella minor, Gaetanus (Gaidius) tenuispinus, Ostracoda, Scaphocalanus brevicornis and Triconia borealis. Zooplankton biomasses in Atlantic- and Arctic-dominated water masses were similar, but biological ''hot-spots'' were associated with Arctic communities.
The feeding strategies of Calanus hyperboreus, C. glacialis, and C. finmarchicus were investigate... more The feeding strategies of Calanus hyperboreus, C. glacialis, and C. finmarchicus were investigated in the high-Arctic Svalbard region (77-81 °N) in May, August, and December, including seasons with algal blooms, late- to post-bloom situations, and unproductive winter periods. Stable isotope and fatty acid trophic marker (FATM) techniques were employed together to assess trophic level (TL), carbon sources (phytoplankton vs. ice algae), and diet of the three Calanus species. In addition, population development, distribution, and nutritional state (i.e. storage lipids) were examined to estimate their population status at the time of sampling. In May and August, the vertical distribution of the three Calanus species usually coincided with the maximum algal biomass. Their stable isotope and fatty acid (FA) composition indicated that they all were essentially herbivores in May, when the algal biomass was highest. Their FA composition, however, revealed different food preferences. C. hyperboreus had high proportions of 18:4n3, suggesting that it fed mainly on Phaeocystis, whereas C. glacialis and C. finmarchicus had high proportions of 16:4n1, 16:1n7, and 20:5n3, suggesting diatoms as their major food source. Carbon sources (i.e. phytoplankton vs. ice algae) were not possible to determine solely from FATM techniques since ice-diatoms and pelagic-diatoms were characterised by the same FA. However, the enriched d13C values of C. glacialis and C. finmarchicus in May indicated that they fed both on pelagic- and ice-diatoms. Patterns in absolute FA and fatty alcohol composition revealed that diatoms were the most important food for C. hyperboreus and C. glacialis, followed by Phaeocystis, whereas diatoms, Phaeocystis and other small autotrophic flagellates were equally important food for C. finmarchicus. During periods of lower algal biomass, only C. glacialis exhibited evidence of significant dietary switch, with a TL indicative of omnivory (mean TL=2.4). Large spatial variability was observed in population development, dis [...]
Sarsia, 2003
... DOI: 10.1080/00364820310002830 Rasmus Skern a * , Mette Mauritzen b , Nils T ... the aggregat... more ... DOI: 10.1080/00364820310002830 Rasmus Skern a * , Mette Mauritzen b , Nils T ... the aggregating behavior of the green sea urchin Strongylocentrotus droebachiensis (Muller) Journal of Experimental Marine Biology and Ecology 176 107 126 View all references; Christie & al. ...
Climate change and ecosystem response 1.3 UV radiation and biological effects 1.4 Ecological impa... more Climate change and ecosystem response 1.3 UV radiation and biological effects 1.4 Ecological impacts of long range pollutants transport 1.5 Integrated aspects 1.6 Conclusions Acknowledgements References 2 An environment at risk: Arctic indigenous peoples, local livelihoods and climate change Mark Nuttall •. 2.1 Introduction 1 2.2 Indigenous Peoples and Traditional Livelihoods 2.3 Renewable Resource Use and Climate Change: Risk and Access to Food Resources 2.4 Concerns Over Irreversible Impacts 2.5 Responding to Climate Change: Flexibility, Adaptation, Barriers and Opportunities 2.6 Conclusions 3 Climate variation in the European sector of the Arctic: Observations and scenarios Inger Hanssen-Bauer viii Arctic-alpine ecosystems and people in a changing environment 3.
Journal of Marine Systems, 2000
The main physical and ecological processes associated with the summer melt period in the marginal... more The main physical and ecological processes associated with the summer melt period in the marginal ice zone MIZ were Ž. investigated in a multidisciplinary research programme ICE-BAR , which was carried out in the northern Barents Sea during June-August 1995-1996. This study provided simultaneous observations of a wide range of physical and chemical factors of importance for the melting processes of sea ice, from its southernmost margins at about 77.58N to the consolidated Arctic pack ice at 81.58N. This paper includes a description of the oceanographic processes, ice-density packing and structures in cores, optical properties of water masses and the ice, characteristics of the incident spectral radiation and chlorophyll-leading to primary production. Large seasonal and inter-annual variations in ice cover in the MIZ were evident from satellite images as well as ship observations. Even if the annual variation in ice extent may be large, the inter-annual variations may be even larger. The minimum observed ice extent in March, for example, can be smaller than the maximum observed ice extent in September. Oceanographic phenomena such as the semi-permanent lee polynyas found west and southwest of Kvitøya and Franz Josef Land and the bay of open water, the AWhalers BayB, north of the Spitsbergen are structures which can change with time intervals of hours to decades. For example, the polynya south of Franz Josef Land was clearly evident in 1995 but was only seen for a short period in 1996. The observed variability in physical conditions directly affects the primary production in the MIZ. From early spring, solar radiation penetrates both leads and the ice itself, initiating algal production under the ice. Light measurements showed that the melt ponds act as windows, permitting the transmission of incoming solar radiation through to the underlying sea ice, thus, accelerating the melting process and enhancing the under-ice primary production. In June 1995, the N-S transect went through a pre-bloom area well inside the ice-covered part of the Barents Sea to a post-bloom phase in the open waters Ž. south of the ice edge. The biological conditions in the later season August of 1996 were considerably more variable. The
Eos, Transactions American Geophysical Union, 2007
Strengthened highland-lowland linkages improve sustainability for both upstream and downstream po... more Strengthened highland-lowland linkages improve sustainability for both upstream and downstream populations. Lowland-highland relationships, whether formal or informal, have the potential to pay for investments in protection and sustainable use of mountain resources. When full costs are taken into account, stewardship of upland resources generally yields greater and more sustainable economic returns both to the people living in the mountain areas and to the immediate downstream economies when compared with extractive activities. In many cases, the focal point of such interactions has been based on providing a sustainable and clean supply of water, the most important and increasingly limiting mountain resource. In steep terrain, more than anywhere else, catchment quality is intimately linked to ecosystem integrity and functioning. Thus environmental conservation and sustainable land use in the world's mountains are not only a necessary condition for sustainable local livelihoods, they are also key to human well-being for nearly half the world's population who live downstream and depend on mountain resources.
Obviously, the many challenges involving climate and stratospheric change, pollutant transport an... more Obviously, the many challenges involving climate and stratospheric change, pollutant transport and social changes are related. A number of other significant dependencies also naturally exist between the various aspects of environmental change parameters and human activities in arctic and alpine areas. The scope here is not to give a complete review of all single processes but to outline the level of interaction between the main contemporary challenges in environmental change, on the basis of the studies presented in the book. Both with respect to the physical processes as well as dealing with their biological impacts and the anthropogenic forcing factors, the changes related to the climate change processes, long range transported pollutants and UV radiation, can not be treated alone or independently but need to be analysed as multiple pressures of the high latitude and high altitude, arctic and alpine environments.