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Bjørn A. Krafft

Bio: Bjørn A. Krafft is an academic researcher from Norwegian Polar Institute. The author has contributed to research in topics: Antarctic krill & Euphausia. The author has an hindex of 19, co-authored 46 publications receiving 1000 citations. Previous affiliations of Bjørn A. Krafft include SINTEF & Norwegian University of Life Sciences.
Topics: Antarctic krill, Euphausia, Krill, Whale, Pusa hispida

Papers
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Journal ArticleDOI
TL;DR: In this article, the authors review the overall impact of climate change on krill and Antarctic ecosystems, discuss implications for an ecosystem-based fisheries management approach and identify critical knowledge gaps.
Abstract: Antarctic krill Euphausia superba (hereafter `krill') occur in regions undergoing rapid environmental change, particularly loss of winter sea ice. During recent years, harvesting of krill has in creased, possibly enhancing stress on krill and Antarctic ecosystems. Here we review the overall impact of climate change on krill and Antarctic ecosystems, discuss implications for an ecosystem-based fisheries management approach and identify critical knowledge gaps. Sea ice decline, ocean warming and other environmental stressors act in concert to modify the abundance, distribution and life cycle of krill. Although some of these changes can have positive effects on krill, their cumulative impact is most likely negative. Recruitment, driven largely by the winter survival of larval krill, is probably the population parameter most susceptible to climate change. Predicting changes to krill populations is urgent, because they will seriously impact Antarctic ecosystems. Such predictions, however, are complicated by an intense inter-annual variability in recruitment success and krill abundance. To improve the responsiveness of the ecosystem-based management approach adopted by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), critical knowledge gaps need to be filled. In addition to a better understanding of the factors influencing recruitment, management will require a better understanding of the resilience and the genetic plasticity of krill life stages, and a quantitative understanding of under-ice and benthic habitat use. Current precautionary management measures of CCAMLR should be maintained until a better understanding of these processes has been achieved. [GRAPHICS] .

270 citations

Journal ArticleDOI
TL;DR: An updated version of KRILLBASE is provided that contains data from 15 194 net hauls, including 12 758 with krill abundance data and 9726 with salp abundance data, and illustrates the seasonal, inter-annual, regional and depth coverage of sampling, and provides both circumpolar- and regional-scale distribution maps.
Abstract: Antarctic krill (Euphausia superba) and salps are major macroplankton contributors to Southern Ocean food webs and krill are also fished commercially. Managing this fishery sustainably, against a backdrop of rapid regional climate change, requires information on distribution and time trends. Many data on the abundance of both taxa have been obtained from net sampling surveys since 1926, but much of this is stored in national archives, sometimes only in notebooks. In order to make these important data accessible we have collated available abundance data (numerical density, no. m−2) of postlarval E. superba and salp individual (multiple species, and whether singly or in chains). These were combined into a central database, KRILLBASE, together with environmental information, standardisation and metadata. The aim is to provide a temporal-spatial data resource to support a variety of research such as biogeochemistry, autecology, higher predator foraging and food web modelling in addition to fisheries management and conservation. Previous versions of KRILLBASE have led to a series of papers since 2004 which illustrate some of the potential uses of this database. With increasing numbers of requests for these data we here provide an updated version of KRILLBASE that contains data from 15 194 net hauls, including 12 758 with krill abundance data and 9726 with salp abundance data. These data were collected by 10 nations and span 56 seasons in two epochs (1926–1939 and 1976–2016). Here, we illustrate the seasonal, inter-annual, regional and depth coverage of sampling, and provide both circumpolar- and regional-scale distribution maps. Krill abundance data have been standardised to accommodate variation in sampling methods, and we have presented these as well as the raw data. Information is provided on how to screen, interpret and use KRILLBASE to reduce artefacts in interpretation, with contact points for the main data providers.

75 citations

Journal ArticleDOI
TL;DR: The size of adult males was correlated with their testosterone levels, but it was not necessarily the largest males that had the most adult female neighbors, which suggests that experience (age) likely plays a strong role in achieving reproductive success for male ringed seals.
Abstract: Spatial distribution of various age- and sex groups of ringed seals (N = 94; 19 adult males, 33 adult females and 42 subadults) was studied in their fast-ice breeding habitat in Kongsfjor- den, Svalbard, during May 2004. Adult females occupied the inner, most stable ice area, while subadults were found predominantly in the outer parts of the fast-ice, where the ice conditions are more unstable. Adult males were scattered across these 2 areas; some were intermingled with breed- ing females while others were found further out towards the ice edge in areas mainly dominated by subadults. This pattern suggests territorial behaviour with competitive exclusion of the subadults and adult males that cannot compete for territories in the prime breeding areas. The size of adult males was correlated with their testosterone levels, but it was not necessarily the largest males that had the most adult female neighbors. The adult males that had the most adult female neighbors were how- ever significantly older than the adult males with fewer female neighbors (18 ± 1 vs. 12 ± 1 yr). This suggests that experience (age) likely plays a strong role in achieving reproductive success for male ringed seals. A male:female sex ratio of 1:2.4 was found in the prime breeding area, which suggests a slightly polygynous mating system.

59 citations

Journal ArticleDOI
TL;DR: Investigation of the spring molting period of 2003 in Kongsfjorden, Svalbard, Norway found that time of day and date significantly affected the number of ringed seals hauled out on the ice surface, and adult females had the greatest number of haul-out periods that exceeded 24 h.
Abstract: Haul-out behavior of ringed seals (Pusa hispida) was investigated during the spring molting period of 2003 (May‐July) in Kongsfjorden, Svalbard, Norway. Hourly counts were conducted on the land-fast ice in six spatially defined sectors in the inner fjord, from an elevated land-based vantage point from early May through until the ice began to break up in June, from 0600 to 2200 daily (total counts n = 478). Concomitantly, measurements were made of a variety of weather parameters. Multiple regression analyses revealed that time of day (P < 0.001) and date (P < 0.001) significantly affected the number of ringed seals hauled out on the ice surface. Other factors influencing the number of seals counted on the ice were air temperature (P = 0.011) and wind speed (P < 0.001). Daily peaks occurred in the early afternoon between 1300 and 1400 and the seasonal high (n = 385) was registered during the first week in June, after which the number of seals on the ice in the fjord declined. In addition to the visual counts, 24 ringed seals were equipped with VHF transmitters, and the haul-out behavior of individuals was monitored from May through July via an automatic recording station. The VHF-tagged seals exhibited the same diurnal pattern seen in the total counts, with haul-out most frequent from 1300 to 1400. Pups exhibited short and frequent haul-outs, whereas longer haul-out periods were seen in the older age classes; adult females had the greatest number of haul-out periods that exceeded 24 h. The seasonal peak of haul-out for the tagged seals preceded the peak seasonal counts by approximately 3 wk. This may reflect significant out- and influx of seals from and to the area, a phenomenon warranting further attention because of its implications for assessment studies.

51 citations

Journal ArticleDOI
TL;DR: In this article, the size selection of krill in a commercially applied codend during experimental fishing was quantified, and it was shown that the trawl body contributes significantly to the total size selection process, demonstrating that size selectivity of Antarctic krill is affected by both the traw body and the codend.

49 citations


Cited by
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Journal ArticleDOI
03 Jul 2015-Science
TL;DR: The physics, chemistry, and ecology of the oceans might be affected based on two CO2 emission trajectories: one business as usual and one with aggressive reductions, consistent with the Copenhagen Accord of keeping mean global temperature increase below 2°C in the 21st century.
Abstract: The ocean moderates anthropogenic climate change at the cost of profound alterations of its physics, chemistry, ecology, and services. Here, we evaluate and compare the risks of impacts on marine and coastal ecosystems—and the goods and services they provide—for growing cumulative carbon emissions under two contrasting emissions scenarios. The current emissions trajectory would rapidly and significantly alter many ecosystems and the associated services on which humans heavily depend. A reduced emissions scenario—consistent with the Copenhagen Accord’s goal of a global temperature increase of less than 2°C—is much more favorable to the ocean but still substantially alters important marine ecosystems and associated goods and services. The management options to address ocean impacts narrow as the ocean warms and acidifies. Consequently, any new climate regime that fails to minimize ocean impacts would be incomplete and inadequate.

1,053 citations

Journal ArticleDOI
TL;DR: Based on a pan-Arctic quantitative index of species sensitivity to climate change, the hooded seal, the polar bear, and the narwhal appear to be the three most sensitive Arctic marine mammal species, primarily due to reliance on sea ice and specialized feeding.
Abstract: We review seven Arctic and four subarctic marine mammal species, their habitat requirements, and evidence for biological and demographic responses to climate change. We then describe a pan-Arctic quantitative index of species sensitivity to climate change based on population size, geographic range, habitat specificity, diet diversity, migration, site fidelity, sensitivity to changes in sea ice, sensitivity to changes in the trophic web, and maximum population growth potential (Rmax). The index suggests three types of sensitivity based on: (1) narrowness of distribution and specialization in feeding, (2) seasonal dependence on ice, and (3) reliance on sea ice as a structure for access to prey and predator avoidance. Based on the index, the hooded seal, the polar bear, and the narwhal appear to be the three most sensitive Arctic marine mammal species, primarily due to reliance on sea ice and specialized feeding. The least sensitive species were the ringed seal and bearded seal, primarily due to large circumpolar distributions, large population sizes, and flexible habitat requirements. The index provides an objective framework for ranking species and focusing future research on the effects of climate change on Arctic marine mammals. Finally, we distinguish between highly sensitive species and good indicator species and discuss regional variation and species-specific ecology that confounds Arctic-wide generalization regarding the effects of climate change.

633 citations

Ove Hoegh-Guldberg, Daniela Jacob, Marco Bindi, Sally Brown, I. A. Camilloni, Arona Diedhiou, Riyanti Djalante, Kristie L. Ebi1, Francois Engelbrecht1, Joel Guiot, Yasuaki Hijioka, S. Mehrotra, Antony J. Payne2, Sonia I. Seneviratne3, Adelle Thomas3, Rachel Warren4, G. Zhou4, Sharina Abdul Halim, Michelle Achlatis, Lisa V. Alexander, Myles R. Allen, Peter Berry, Christopher Boyer, Edward Byers, Lorenzo Brilli, Marcos Silveira Buckeridge, William W. L. Cheung, Marlies Craig, Neville Ellis, Jason P. Evans, Hubertus Fischer, Klaus Fraedrich, Sabine Fuss, Anjani Ganase, Jean-Pierre Gattuso, Peter Greve, Tania Guillén Bolaños, Naota Hanasaki, Tomoko Hasegawa, Katie Hayes, Annette L. Hirsch, Chris D. Jones, Thomas Jung, Markku Kanninen, Gerhard Krinner, David M. Lawrence, Timothy M. Lenton, Debora Ley, Diana Liverman, Natalie M. Mahowald, Kathleen L. McInnes, Katrin J. Meissner, Richard J. Millar, Katja Mintenbeck, Daniel M. Mitchell, Alan C. Mix, Dirk Notz, Leonard Nurse, Andrew Emmanuel Okem, Lennart Olsson, Michael Oppenheimer, Shlomit Paz, Juliane Petersen, Jan Petzold, Swantje Preuschmann, Mohammad Feisal Rahman, Joeri Rogelj, Hanna Scheuffele, Carl-Friedrich Schleussner, Daniel Scott, Roland Séférian, Jana Sillmann, Chandni Singh, Raphael Slade, Kimberly Stephenson, Tannecia S. Stephenson, Mouhamadou Bamba Sylla, Mark Tebboth, Petra Tschakert, Robert Vautard, Richard Wartenburger, Michael Wehner, Nora Marie Weyer, Felicia S. Whyte, Gary W. Yohe, Xuebin Zhang, Robert B. Zougmoré 
01 Jan 2018
TL;DR: In this article, the authors present a survey of women's sportswriters in South Africa and Ivory Coast, including: Marco Bindi (Italy), Sally Brown (UK), Ines Camilloni (Argentina), Arona Diedhiou (Ivory Coast/Senegal), Riyanti Djalante (Japan/Indonesia), Kristie L. Ebi (USA), Francois Engelbrecht (South Africa), Joel Guiot (France), Yasuaki Hijioka (Japan), Shagun Mehrotra (USA/India), Ant
Abstract: Lead Authors: Marco Bindi (Italy), Sally Brown (UK), Ines Camilloni (Argentina), Arona Diedhiou (Ivory Coast/Senegal), Riyanti Djalante (Japan/Indonesia), Kristie L. Ebi (USA), Francois Engelbrecht (South Africa), Joel Guiot (France), Yasuaki Hijioka (Japan), Shagun Mehrotra (USA/India), Antony Payne (UK), Sonia I. Seneviratne (Switzerland), Adelle Thomas (Bahamas), Rachel Warren (UK), Guangsheng Zhou (China)

614 citations

Journal ArticleDOI
TL;DR: Kongsfjorden is a glacial fjord in the Arctic (Svalbard) that is influenced by both Atlantic and Arctic water masses and harbours a mixture of boreal and Arctic flora and fauna as discussed by the authors.
Abstract: Kongsfjorden is a glacial fjord in the Arctic (Svalbard) that is influenced by both Atlantic and Arctic water masses and harbours a mixture of boreal and Arctic flora and fauna. Inputs from large tidal glaciers create steep environmental gradients in sedimentation and salinity along the length of this fjord. The glacial inputs cause reduced biomass and diversity in the benthic community in the inner fjord. Zooplankton suffers direct mortality from the glacial outflow and primary production is reduced because of limited light levels in the turbid, mixed inner waters. The magnitude of the glacial effects diminishes towards the outer fjord. Kongsfjorden is an important feeding ground for marine mammals and seabirds. Even though the fjord contains some boreal fauna, the prey consumed by upper trophic levels is mainly Arctic organisms. Marine mammals constitute the largest top-predator biomass, but seabirds have the largest energy intake and also export nutrients and energy out of the marine environment. Kongsfjorden has received a lot of research attention in the recent past. The current interest in the fjord is primarily based on the fact that Kongsfjorden is particularly suitable as a site for exploring the impacts of possible climate changes, with Atlantic water influx and melting of tidal glaciers both being linked to climate variability. The pelagic ecosystem is likely to be most sensitive to the Atlantic versus Arctic influence, whereas the benthic ecosystem is more affected by long-term changes in hydrography as well as changes in glacial runoff and sedimentation. Kongsfjorden will be an important Arctic monitoring site over the coming decades and a review of the current knowledge, and a gap analysis, are therefore warranted. Important knowledge gaps include a lack of quantitative data on production, abundance of key prey species, and the role of advection on the biological communities in the fjord.

574 citations

Journal ArticleDOI
TL;DR: It is unlikely that polar bears will survive as a species if the sea ice disappears completely as has been predicted by some, but the effects of climate change are likely to show large geographic, temporal and even individual differences and be highly variable, making it difficult to develop adequate monitoring and research programs.
Abstract: SYNOPSIS. Polar bears (Ursus maritimus) live throughout the ice-covered waters of the circumpolar Arctic, particularly in near shore annual ice over the continental shelf where biological productivity is highest. However, to a large degree under scenarios predicted by climate change models, these preferred sea ice habitats will be substantially altered. Spatial and temporal sea ice changes will lead to shifts in trophic interactions involving polar bears through reduced availability and abundance of their main prey: seals. In the short term, climatic warming may improve bear and seal habitats in higher latitudes over continental shelves if currently thick multiyear ice is replaced by annual ice with more leads, making it more suitable for seals. A cascade of impacts beginning with reduced sea ice will be manifested in reduced adipose stores leading to lowered reproductive rates because females will have less fat to invest in cubs during the winter fast. Non-pregnant bears may have to fast on land or offshore on the remaining multiyear ice through progressively longer periods of open water while they await freeze-up and a return to hunting seals. As sea ice thins, and becomes more fractured and labile, it is likely to move more in response to winds and currents so that polar bears will need to walk or swim more and thus use greater amounts of energy to maintain contact with the remaining preferred habitats. The effects of climate change are likely to show large geographic, temporal and even individual differences and be highly variable, making it difficult to develop adequate monitoring and research programs. All ursids show behavioural plasticity but given the rapid pace of ecological change in the Arctic, the long generation time, and the highly specialised nature of polar bears, it is unlikely that polar bears will survive as a species if the sea ice disappears completely as has been predicted by some.

455 citations