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Changes in prey-predator interactions in an Arctic food web under climate change
Get PDFGlobal warming affects marine ecosystems by changing environmental conditions, ecosystem structure, and ecosystem functioning. In parts of the Arctic, increased sea temperature and decreased sea ice have led to a poleward expansion of boreal species and increased their interactions with native Arctic species. To investigate and quantify the changing interactions in an Arctic marine food web under new environmental conditions, we studied the interactions between key prey fish species in the seasonally ice-covered parts of the Barents Sea: adult polar cod (Boreogadus saida) and capelin (Mallotus villosus) and one of the major predators in the system: Atlantic cod (Gadus morhua). For this, we compared the predictive performance of threshold models predicting the abundance of adult polar cod as a function of Atlantic cod. Each model was associated with a hypothesis describing prey-predator interactions in different environmental conditions defined by threshold values of summer sea-ice or capelin stock biomass. The best predictive model showed that the predation effect of Atlantic cod on polar cod was strongest in years of low summer sea ice cover and low capelin stock biomass. Our results exemplified that Arctic species such as polar cod may experience increased predation pressure under climate change from boreal species such as Atlantic cod. These effects depend, however, not only on changes in abiotic drivers of species distributions, but also on food-web interactions involving mid-trophic level species such as capelin.publishedVersio
Post-mortem tissue migration of Anisakis simplex (s.s.) larvae (Nematoda: Anisakidae) in three commercially harvested fish species from the Northeast Atlantic: The role of storage time and temperature
Get PDFAnisakis simplex sensu stricto is a parasite infecting several commercial fish species in the Northeast (NE) Atlantic, known to be the aetiological agent of the human zoonosis anisakiasis. The present study investigated the response of A. simplex (s. s.) third stage larvae (identified to species level by mtDNA cox2 sequencing) to the storage time and temperature of Atlantic herring (Clupea harengus), Atlantic mackerel (Scomber scombrus) and blue whiting (Micromesistius poutassou) from NE Atlantic fishing areas. A total of 300 fish per species were divided in batches of 50 individuals straight after catch. Each batch was stored at different temperature conditions (2 °C, 5 °C, 15 °C) for different time intervals (24h and 48h). A batch of 50 fish of each species was frozen immediately after catch and used as control (time zero). All fish were inspected by the UV-press method. Blue whiting was the most infected fish species while mackerel harboured the highest proportion of intra-vitam A. simplex (s. s.) larvae in the musculature. In blue withing there was a significant increase in the proportion of larvae in the muscle with increasing storage temperatures (5 °C < 15 °C) and time (24h < 48h). Herring showed a weak trend of increasing parasite infection in the muscle with increasing temperature/time. In contrast, no significant differences of muscle/viscera larval distribution were observed between batches of mackerel stored at different temperatures for different time intervals. Storage temperature and time seem to play a role in the post-mortem motility of A. simplex (s. s.) larvae in herring and blue whiting. Keeping the temperature at ≤ 2 °C seems to prevent post-mortem larval migration into the flesh during fish storage, handling, and transport. Besides abiotic variables, the differences observed in larval post-mortem motility in the different fish species are biologically determined, and attributable to species-specific host-parasite interactions.publishedVersio
Expanding Influence of Atlantic and Pacific Ocean Heat Transport on Winter Sea-Ice Variability in a Warming Arctic
Get PDFThe gradual anthropogenic-driven retreat of Arctic sea ice is overlaid by large natural (internal) year-to-year variability. In winter, sea-ice loss and variability are currently most pronounced in the Barents Sea. As the loss of winter sea ice continues in a warming world, other regions will experience increased sea-ice variability. In this study, we investigate to what extent this increased winter sea-ice variability in the future is connected to ocean heat transport (OHT). We analyze and contrast the present and future link between Pacific and Atlantic OHT and the winter Arctic sea-ice cover using simulations from seven single-model large ensembles. We find strong model agreement for a poleward expanding impact of OHT through the Bering Strait and the Barents Sea under continued sea-ice retreat. Model differences on the Atlantic side can be explained by the differences in the simulated variance of the Atlantic inflows. Model differences on the Pacific side can be explained by differences in the simulated strength of Pacific Water inflows, and upper-ocean stratification and vertical mixing on the Chukchi shelf. Our work highlights the increasing importance of the Pacific and Atlantic water inflows to the Arctic Ocean and highlights which factors are important to correctly simulate in order to capture the changing impact of OHT in the warming Arctic.publishedVersio
Successful large-scale and long-term kelp forest restoration by culling sea urchins with quicklime and supported by crab predation
Get PDFIn 2013, a large scale (70 hectare) kelp forest restoration experiment was conducted in a sea urchin barren that had been stable for 45 years. We used 200 tons of quicklime to eradicate the sea urchin population. Kelp recovered within a year in the lime-treated sites. Quickliming did not significantly affect the abundance of non-target species. Mobile kelp fauna colonized the restored kelps, but at a slower rate than kelp and other macroalgae, probably due to slower dispersal abilities. The monitoring period (2012–2021) encompassed the expansion of invasive red king crabs, which emerged as a novel predator of sea urchins. This led to a gradual decline in sea urchin populations and facilitated kelp recovery also in the control sites. This delayed recovery does not invalid the conclusions of the short-term efficiency of the quicklime treatment, but it makes it difficult to conclude about the long-term effects. The study shows that quickliming can initiate kelp recovery within large urchin barrens. We postulate that the recovery of kelps outside the limed areas was due to crab predation, and that successful kelp restoration in areas with recruitment of sea urchins depends on a persistent top-down control of the urchins.publishedVersio
Report on evaluation of harvest rules for Barents Sea capelin in subareas 1 and 2 (northeast arctic), excluding division 2.a west of 5°W - full report
Get PDFFollowing a recent benchmark for capelin (Mallotus villosus) in the Barents Sea (ICES 2023), the Joint Norwegian-Russian Fisheries Commission requested that alternative configurations of the existing capelin harvesting rule be reassessed. The existing rule has been in place since 1991 and states that TAC shall not exceed the value corresponding to a 95% probability of allowing 200,000 tonnes to spawn. The 200,000 tonnes limit was previously interpreted as the biological reference point Blim. During the benchmark however, Blim was differentiated from the limit used in the harvest control rule, now called Bescapement, which is now the biomass that must escape to spawn each spring with 95% probability. Blim was reassigned 68,000 tonnes and 200,000 tonnes was assigned to Bescapement at the benchmark. Three sets of harvest rules were requested to be evaluated: the first is the existing rule, which specifies Bescapement=200,000 tonnes; the second rule encompasses several alternative Bescapement values (100,000, 150,000, and 400,000 tonnes); and the third rule includes several fixed minimum quota values to be paired with the Bescapement values of the first two rules.Report on evaluation of harvest rules for Barents Sea capelin in subareas 1 and 2 (northeast arctic), excluding division 2.a west of 5°W - full reportpublishedVersio
Invertebrate Responses to Large- and Small-Scale Drivers in Coastal Phragmites australis Beds in the Northern Baltic Sea
Get PDFPhragmites australis is a common helophyte, covering much of the sheltered and shallow soft bottoms along the coasts of the Baltic Sea. Despite the expansion of P. australis over the past decades, there is little information on aquatic macroinvertebrates within P. australis beds. In this study, we examined the effect of large-scale (wave exposure, nutrients) and small-scale (distance from the seaward edge, live and dead stalk density, epiphyte and rhizome biomass) drivers on the density, taxa richness, diversity, and community structure of epifauna and infauna in monospecific P. australis beds around the Åland Islands and the Archipelago Sea. We found that higher wave exposure and nutrient levels generally supported higher epi- and infauna abundance and taxa richness. The effects on Shannon–Wiener diversity were less evident apart from an increase of the infauna diversity in the Archipelago Sea with increasing nutrient levels. On a local scale, the distance from the seaward edge, live and dead stalk density, and epiphyte biomass had varying effects on both epi- and infauna communities in the different regions. Rhizome biomass had no effect on either the epi- or infauna abundance, taxa richness, or diversity. Furthermore, according to existing studies, other habitats, e.g., Zostera marina meadows, Fucus vesiculosus belts, and vegetated soft-bottomed shallow bays, are generally characterized by more abundant fauna, except for the infauna, which had a higher density in P. australis beds than in vegetated soft-bottomed shallow bays. P. australis are a widespread, expanding, and understudied habitat with an important role in supporting coastal biodiversity.publishedVersio
Particle exchange between coast and fjords and its biological implications
Get PDFThe exchange of water and particles between coastal and fjord areas is crucial for the overall health of fjord ecosystems. In this study, we use a Lagrangian ocean particle tracking model combined with zooplankton field data in the Hardangerfjord region of western Norway, to investigate advective exchange of particles between the coast and fjord and to provide insights on its biological implications. Our findings indicate that particles in the coastal region have a limited time-window to enter the fjord and an even lower chance of reaching the inner part, especially during spring compared to autumn, driven by seasonal variation of physical conditions at the coast. The low connectivity between the coastal area and the inner part of the fjord leads to the observed decreasing gradient in the abundance of drifting zooplankton with oceanic origins, such as Calanus spp., and a shift in zooplankton composition along the fjord axis. The vertical distribution of zooplankton also plays a critical role in the exchange of these organisms between the coast and fjord. Our study shows that the population of Calanus spp. in the Hardangerfjord in spring depends on advective inputs from coastal waters as well as local production inside the fjord. Despite the low chance of particles being advected into the fjord, the large number of individuals in the advective layer at the coast in spring serves as a significant source. In contrast, local production becomes more critical than advective inputs in autumn when Calanus spp. descend to deeper depths in coastal waters. Our study further suggests that the recolonization of northern shrimp in Hardangerfjord is likely to be a slow process due to the low connectivity between the coast and fjord. This finding calls for caution in coastal management regarding resident or local species in fjords which are more vulnerable and harder to restore than drifting species.publishedVersio
Report on cruises and data stations 2023
Get PDFThe report gives an overview of cruises in 2023, by the Institute of Marine Research, University of Bergen and Tromsø and Norwegian Polar Institute, on board our research vessels and many of the hired commercial vessels. Each cruise has a short description and a track chart showing CTD and trawl stations. A table displaying the coverage of the oceanographic sections in addition to a table showing the number of observations per month for the fixed stations are included at the end of the report. Meta data about the cruises are reported to the International Council for the Exploration of the Sea (ICES) using the form “Cruise Summary Report”: https://www.seadatanet.org/Metadata/CSR-Cruises. Research data are available from the Norwegian Marine Data Centre at Institute of Marine Research (https://www.nmdc.no). Charts are generated by Silje Smith-Johnsen using ggOceanMaps by Mikko Vihtakari (IMR).Report on cruises and data stations 2023publishedVersio
National monitoring program for bivalves and other molluscs – samples analysed in 2023 for chemical contaminants and micro organisms
Get PDFMikrobiologi I den mikrobiologiske delen av tilsynsprogrammet for skjell, tok Mattilsynet i 2023 ut i alt 194 prøver fordelt gjennomåret. Av disse var 128 blåskjell (Mytilus edulis), 21 kamskjell (Pecten maximus), 11 flatøsters (Ostrea edulis), femstillehavsøsters (Crassostrea gigas), 10 teppeskjell (Politapes rhomboides), ni oskjell (Modiolus modiolus), ni knivskjell (Solenidae spp) og èn Drøbak-kråkebolle (Strongylocentrotus droebachiensis). Prøvene ble sendt til Havforskningsinstituttet (HI) etter instruks utarbeidet av Mattilsynet. Ved HIs laboratorier ble antall E. coli bestemt ved en flerrørs fortynningsmetodikk (MPN) i henhold til EUs referansemetode (Donovans metode, ISO 16649-3) og undersøkt med hensyn på forekomst av Salmonella ved hjelp av ISO 6579-1:2017 metoden. 194 av prøvene ble undersøkt for antall E. coli, mens et utvalg på 30 prøver ble analysert for Salmonella spp. I 24 (8,1 %) av 194 analyserte prøver var innholdet av E. coli > 230/100 g. Av disse prøvene var 16 blåskjell, tre teppeskjell, og en hver av Stillehavsøsters, flatøsters og stort kamskjell. Den høyeste målte verdien av E. coli var på over 180 000/100g i to prøver av blåskjell. Av prøvene som ble undersøkt med tanke på E. coli var 31 sluttprodukter. Fire av disse prøvene hadde E. coli konsentrasjoner over 230/100 g, en prøve av Stillehavsøsters (3500/100g), en prøve av flatøsters (1100/100g), en prøve av stort kamskjell (490/100g), og en prøve av blåskjell (260/100g). Bakterier i slekten Salmonella ble ikke påvist i noen av de undersøkte prøvene. I tillegg til prøvene innsendt av Mattilsynet ble det også gjennomført mikrobiologisk analyse på 335 prøver sendt inn av næringen. Av disse var 316 prøver av blåskjell, 15 var flatøsters, to av stort kamskjell og to av Drøbak- kråkebolle. Av disse var innholdet av E. coli > 230/100 g i 28 av prøvene (8,4 %), hvorav alle var blåskjell, og høyeste avleste konsentrasjon av E. coli var 5400/100g. De øvrige 307 prøvene (91,6 %) hadde et innhold av E. coli lik eller under 230/100 g. Kjemiske fremmedstoffer Prøvetakingen av skjell og andre bløtdyr utført av Mattilsynets inspektører i 2023 for bestemmelse av fremmedstoffer omfattet 27 prøver av blåskjell, 8 prøver av kamskjell, én prøve av flatøsters, tre prøver av oskjell, to prøver av haneskjell, to prøver av knivskjell og én prøve av Drøbak-kråkeboller. I tillegg tok næringen ut 23 prøver av blåskjell og én prøve av flatøsters. Prøvene ble sendt til Havforskningsinstituttet i henhold til instruks utarbeidet av Mattilsynet. Prøvene ble analysert for metallene kobber, sink, arsen, selen, sølv, kadmium, kvikksølv og bly, samt uorganisk arsen. I tillegg ble prøver tatt ut om høsten analysert for dioksiner/furaner, dioksinlignende PCB, ikke- dioksinlignende PCB (PCB ), PBDE, polyaromatiske hydrokarboner (PAH) og TBT. Alle fremmedstoffanalysene ble gjort på frysetørket materiale. Metallbestemmelsene ble utført med ICPMS, uorganisk arsen med HPLC-ICPMS, TBT med GC-ICPMS, dioksiner, furaner og non-orto PCB med høyoppløsende GC-MS, mono-orto PCB og PCB med GC-MSMS, PBDE med GC-MSMS (EI) og PAH med GC-MSMS. Alle bestemmelser ble utført ved Havforskningsinstituttet, og akkrediteringer er i henhold til NS-EN-ISO 17025. Som for tidligere år ble det i 2023 stort sett funnet lave nivåer av metaller i prøvene og svært lave verdier av organiske miljøgifter. Dette året ble det funnet én overskridelse for prøver av flatøsters som oversteg grenseverdien for kadmium på 1,0 mg/kg våtvekt med 1,5 mg/kg våtvekt. Det ble også funnet en verdi for kadmium på 3,0 mg/kg våtvekt i hel innmat av haneskjell, mens en prøve av muskel som var renset ut etter at innmaten var fryst hel hadde en konsentrasjon av kadmium på 0,67 mg/kg våtvekt. Resultatene fra prøvene innsendt av næringen er på nivå med prøvene sendt inn i regi av Mattilsynet.Nasjonalt tilsynsprogram for produksjon av skjell og andre bløtdyr – prøver analysert i 2023 for kjemiske forurensende stoffer og mikroorganismerNational monitoring program for bivalves and other molluscs – samples analysed in 2023 for chemical contaminants and micro organismspublishedVersio
