Temporal Variability of Co-Occurring Calanus finmarchicus and C. helgolandicus in Skagerrak

The congeneric copepods Calanus finmarchicus and C. helgolandicus co-occur in the northern North Sea and Skagerrak where they play important roles as prey for higher trophic levels. This study analyses a 26-year time series (1994-2019) with a ~ two-week temporal resolution for Calanus spp. at a fixed monitoring station in Skagerrak, off southern Norway. Seasonal variation, inter-annual variability and long-term trends for the two species were examined. Strong differences in the species-specific seasonality were revealed, with C. finmarchicus dominating in spring and C. helgolandicus in autumn. The seasonal peak of C. finmarchicus was associated with relatively low temperatures (6-8°C) and high chlorophyll a concentration, while C. helgolandicus displayed its seasonal maximum at higher temperatures (11-16°C). C. finmarchicus was found to produce one dominant annual generation (in spring), but two or more generations are considered likely. Contrasting long-term trends in abundances were found for the two species, suggesting that their population sizes were affected by different mechanisms. The abundance of C. helgolandicus showed an increasing trend over the time period studied, apart from the last years. The abundance of C. finmarchicus was more variable and displayed no unidirectional long-term trends over the time series. The study revealed a shift in the phenology of Calanus spp. over the last 25 years at this site. Since 1994 the timing of the annual peaks in both C. finmarchicus and C. helgolandicus have advanced by about one month. Moreover, the seasonal pattern of C. helgolandicus, switched from a unimodal to a bimodal pattern around 2002, with a small additional peak also appearing in spring. The results suggest that the proximity to the Norwegian Trench influences the demography and abundance of C. finmarchicus in this coastal area, both as a gateway for the advective supply, as well as a habitat for local overwintering.publishedVersio

The Continuous Plankton Recorder Survey – Monitoring plankton in the Nordic Sea

The warm-temperate calanoid copepod Calanus helgolandicus is becoming more common in the Nordic Seas with high records in 2016, which continued into 2017. The Pacific diatom Neodenticula seminae (an indicator of trans-Arctic migration) was recorded off Svalbard in 2016, which is its most easterly record in the Nordic Seas.publishedVersio

Comparison of two multiple plankton samplers: MOCNESS and Multinet Mammoth

To ensure an optimal continuation of a long time series of zooplankton monitoring surveys, two types of equipment for depth-stratified mesozooplankton sampling were compared. The Institute of Marine Research (Norway) has applied the MOCNESS with good results since 1985, but recent events have made it necessary to change to the Multinet Mammoth. During a cruise in March 2019, both sampling devices were calibrated before 17 paired deployments of the 2 gears were undertaken. During each deployment, three nets and depth-strata covering ~ 425–200, 200–100, and 100–0 m were sampled. All samples were size-fractionated or taxonomically fractionated into 10 different biomass categories. The results revealed no significant differences between the two gears when comparing total depth-integrated biomass (2.46 ± 0.36 vs. 2.61 ± 0.59 gDW m−2) or depth-integrated biomass of any specific biomass category. Running paired t-tests separately for all combinations of biomass categories and nets, the differences were only significant for zooplankton biomasses in the 180–1000 μm size fraction and only for Net 2. Possible reasons for this result are discussed in the paper. Gears produced similar catches whether sampling during day or night. We conclude that the MOCNESS and Multinet Mammoth in this study provided comparable results regarding abundances of various zooplankton categories.publishedVersio

Seasonal and interannual variability in abundance and population development of Calanus finmarchicus at the western entrance to the Barents Sea, 1995–2019

Data on copepodid abundance and stage composition of Calanus finmarchicus was collected with seasonal resolution (5–6 times a year) from four stations along an oceanographic transect across the western Barents Sea Opening over 25 years (1995–2019). The stations were located in the Norwegian Coastal Current (NCC), inflowing Atlantic water (two stations), and near the Arctic polar front south of Bear Island. Mean copepodite abundance in the water column for the four stations increased from a level around 1000–10,000 individuals m−2 in winter to 30,000–100,000 individuals m−2 in summer (maximum 670,000 m−2). The overwintering (G0) population was dominated by copepodite stage 5 (CV) (40–70%) but with a relatively high fraction also of stage CIV (25–35%) in January. During winter, there was a progressive development of CVs into adult males and females, with mean abundances from 1500 to 4000 adult females m−2 in April and May for the stations in the NCC and Atlantic water. Young copepodids of the new spring generation (G1) appeared with relatively high abundances in April at the NCC station and in May at the Atlantic water stations. The data showed a gradient of later development from south to north, reflected both in the maturation of the overwintering generation and in the development of the spring generation. Back-calculations based on temperature-dependent development time suggested peak spawning around late April to mid-May for the Atlantic water stations, and a month or so earlier (in March) for the NCC station, during an early phase of the spring phytoplankton growth. The spring generation developed as a distinct cohort but with large interannual variability in numbers. In Atlantic water, the composition of the copepodid developmental stages in August resembled the situation in June, although it was slightly more advanced. This is interpreted to reflect development of a second generation (G2) spawned upstream sometime in June or early July. The June data suggests that only a small fraction of the G1 cohort develops into adults that spawn and form the G2. There was a tendency of increased summer abundance of C. finmarchicus in the inflow region of the southwestern Barents Sea after about 2005. This may be related to the wind regime with more eastward wind-stress at the Barents Sea opening in recent ‘high Calanus’ years compared to ‘low Calanus’ years in the early 2000s.publishedVersio

Asynchronized spawning responses of small pelaigic fish to a short-term enviromental change

We provide substantial evidence on how short-term changes in environmental conditions activate and deactivate spawning activities in small pelagic fishes. An ichthyoplankton survey was conducted along the southernmost part of the Canary Current upwelling ecosystem in May 2013, covering the area twice within 20 d. This period coincided with a strong environmental change from a cold productive upwelling regime to a warmer and less productive upwelling relaxation event. This change triggered a shift in spawning activity from European anchovy Engraulis encrasicolus to round/flat sardinella Sardinella spp. We used zero-altered negative binomial regression models with a generalized additive structure based on integrated nested Laplace approximations to link early larval distribution patterns to the 2 different regimes. The models confirmed 2 species-specific temperature spawning windows, suggesting a spawning pause of anchovy during upwelling relaxation while simultaneously activating spawning in sardinella. Observing immediate spawning responses to the 2 environmental regimes underlines the assumption that windows of spawning opportunity are the main drivers of small pelagic fish fluctuations in upwelling regions. The duration of a specific environmental condition can, therefore, increase or decrease the chances for reproductive success. The observations of this study may explain why certain small pelagic fish species can dominate over others during a particular period and might also apply to other upwelling regions of the world oceans where upwelling and relaxation events alternate.publishedVersio

Diversity and seasonal development of large zooplankton along physical gradients in the Arctic Barents Sea

Due to ongoing climate change, a new Arctic Ocean ecosystem is emerging. Within the framework of the Nansen Legacy project, we investigated the community composition of the large zooplankton and its seasonal development along a latitudinal gradient in the northern Barents Sea. Total biomass was maximal in summer and early winter, and minimal in spring, with copepods contributing considerably in all seasons. Euphausiids represented a minor fraction of the biomass, whereas chaetognaths and other gelatinous zooplankton contributed substantially to the sampled zooplankton at all stations, particularly in winter. Amphipod biomass was high in early winter, but otherwise low. Temperature in the water column interior and bottom-depth had the highest explanatory power for the community composition of the large zooplankton, both revealing the same distinct Atlantic and Arctic domains along the studied section. The continental shelf of the northern Barents Sea had an Arctic signature and was in terms of biomass characterized by a dominance of cold-water species, such as Themisto libellula, and Calanus glacialis. The copepod Calanus hyperboreus was the dominant over the continental slope. Locations at the southern and northern end of the studied section were influenced by Atlantic Water (at intermediate depth at the northern stations), and contained a mixture of temperate species, deep-water species, and sympagic amphipods in northern ice-covered waters. In the northern Barents Sea, a seasonal change was observed in the biomass fractions of different zooplankton feeding guilds, with dominance of herbivores in summer and carnivores in winter. This suggests switching between bottom-up and top-down control through the year. On the continental slope, species that are typically considered omnivores seemed to increase in importance. The role of seasonally changing food preferences to bridge periods outside of the main primary production season is discussed in light of ecosystem resilience to the expected changes in the Arctic Ocean.publishedVersio

Pelagiske økosystem i De nordiske hav - grunnlagsstudie knyttet til åpningsprosess for utforskning og utvinning av havbunnsmineraler på norsk kontinentalsokkel

Denne rapporten er en leveranse til bestillingen «Grunnlagsstudie: Pelagisk økosystem» fra Oljedirektoratet til Havforskningsinstituttet. Studien er bestilt i forbindelse med at regjeringen har igangsatt en prosess for åpning av norsk sokkel for havbunnsmineralvirksomhet. Rapporten sammenstiller vår nåværende kunnskap om de pelagiske økosystemenes struktur og funksjon og belyser viktige kunnskapshull. Det er lagt særlig vekt på å beskrive økosystemkomponenter og prosesser som er essensielle for arbeidet med planprogram for konsekvensutredning av havbunnsmineralvirksomhet i norske havområder, og fokus vil derfor tidvis være litt annerledes enn det man vil finne i en generell beskrivelse av Norskehavet, Islandshavet og Grønlandshavet. Vi har lagt mer vekt på eksisterende kunnskapshull, og fokusert mer på utredningsområdet og på økologi og prosesser i pelagisk sone i dyphavet, enn det som kan forventes i for eksempel en lærebok om plankton-, fisk eller sjøpattedyrøkologi. Selv om formålet dermed har farget fokuset for beskrivelsene, beskriver kapitlene generell fordeling og økologi i de pelagiske systemene i Norskehavet, Islandshavet og Grønlandshavet.publishedVersio

Toktrapport fra det norsk/russiske økotoktet i Barentshavet og nærliggende områder

The aim of the joint Norwegian/Russian ecosystem survey in the Barents Sea and adjacent waters, August-October (BESS) is to monitor the status and changes in the Barents Sea ecosystem and provide data to support stock advice and research. The survey has since 2004 been conducted annually in the autumn, as a collaboration between the Institute of Marine Research (IMR) in Norway and the Polar branch of the VNIRO (PINRO) in Russia. The general survey plan and tasks were agreed upon at the annual IMR-PINRO Meeting in March 2022. Ship routes and other technical details are agreed on by correspondence between the survey coordinators. BESS aims at covering the entire Barents Sea. Ecosystem stations are distributed in a 35×35 nautical mile regular grid, and the ship tracks follow this design. Exceptions are the area around Svalbard (Spitsbergen), some additional bottom trawl hauls for demersal fish survey indices estimation, and additional acoustic transects for the capelin stock size estimation. Survey start for the Russian vessel was significantly delayed, resulting in REEZ being covered two-three months later than NEEZ. This resulted in reduced area coverage, decrease in the numbers of trawl hauls, and lack of standard pelagic trawl sampling. In NEEZ, RV “Kronprins Haakon” was cancelled due to difficult economic situation, making it necessary to allocate one of the two remaining vessels to the area west and north of Svalbard (Spitsbergen). This resulted in low coverage in this area, and problems with synoptic coverage in north-east of Svalbard (Spitsbergen) and thus increased uncertainty in assessment of demersal fish (e.g. Greenland halibut) and capelin. The 19-th joint Barents Sea autumn Ecosystem Survey (BESS) was carried out in two periods. The Norwegian research vessels “G.O. Sars” and “Johan Hjort” covered NEEZ in the period 16-th August to 03-th October, providing data to stock assessment, 0-group fish abundance indices, and state and changes descriptions which is comparable with earlier survey years in NEEZ. The Russian research vessel “Vilnyus” covered REEZ in the periods 20-th to 30-th September and 22-th October to 3-rd December. Survey coordinators in 2022 were Dmitry Prozorkevich (PINRO) and Geir Odd Johansen (IMR). Exchange of Russian and Norwegian experts between each country’s respective vessels did not take place in 2022. We would like to express our sincere gratitude to all the crew and scientific personnel onboard RVs “Vilnyus”, “G.O. Sars” and “Johan Hjort” for their dedicated work, as well as all the people involved in planning and reporting of BESS 2022. This report is a summary of observations and status assessment based on the survey data. Even though the survey was not well completed, the data obtained are the main source of knowledge about the ecosystem of the Barents Sea.Survey report from the joint Norwegian/Russian Ecosystem Survey in the Barents Sea and the adjacent waters August- December 2022publishedVersio

Innspill til høring - Forslag til program for konsekvensutredning for mineralvirksomhet på norsk sokkel

Rapporten er et høringssvar sendt til Olje- og Energidepartementet i forbindelse med et forslag til konsekvensutredningsprogram for mineralvirksomhet på norsk kontinentalsokkel. I høringssvaret påpeker Havforskningsinstituttet at det er stor mangel på kunnskap, både med hensyn til biomangfold og økologiske forhold, men også når det gjelder teknologien som vil anvendes for utvinning av mineraler og metaller på havbunnen. Denne kunnskapsmangelen representerer en usikkerhet som bør synliggjøres i konsekvensutredningen, blant annet gjennom en risikoanalyse. Havforskningsinstituttet påpeker også at ulike initiativ når det gjelder kunnskapsinnhenting burde vært ferdigstilt før gjennomføringen av høringen. En grundigere oppsummering av rapportens innhold er gitt i første kapittel.publishedVersio

First results from the L3+C experiment at CERN

The L3+C experiment combines the high-precision spectrometer of the L3 detector at LEP, CERN, with a small air shower array. The momenta of cosmic ray induced muons can be measured from 20 to 2000 GeV/c. During the 1999 data taking period 5 billion muon events were recorded in the spectrometer. From April until mid Summer 2000 an additional 3 billion muon events have been recorded as well as 25 million air shower events. Here the first results on the muon momentum spectrum and charge ratio will be presented