Brage IMR
Not a member yet
12041 research outputs found
Sort by
Unravelling nutrient dynamics and mixed layer depth variability in the equatorial Atlantic: insights from 10°W meridional section monitoring
Get PDFThe ocean, a pivotal component of the Earth’s climate system, exerts a profound global influence through intricate physical and biological interactions within its surface layer. This interplay centers around the mixed layer (ML), integral for energy exchange driven by oceanic currents. An essential regulatory function of the ocean involves orchestrating the distribution of chemical elements, with nitrate assuming a pivotal role in oceanic primary production. Nutrient availability, a cornerstone of primary production, hinges on the mixed layer depth (MLD) dynamics, modulated by many mechanisms, including upwelling and convection. This study unravels the interplay between nutrient variability and MLD depth, focusing on the Gulf of Guinea (GG) region in the equatorial Atlantic. Characterization of the study area reveals distinctive sea surface temperature (SST), salinity (SSS), and current patterns. The South Equatorial Undercurrent (SEUC) and Equatorial Undercurrent (EUC) play vital roles in surface nutrient transport. Nitrate distribution unveils latitudinal variations, exhibiting pronounced enrichment during boreal summer and winter. The equatorial region experiences a strengthening of MLDs from 10.5 to 35.33 m in summer, which increases the nitrate input from 0 to 2.06 mmol m-3 in the surface layers in the mixed layer. In contrast, boreal winters experience more intense MLDs that vary between 20.5 and 64.50 m, supporting high nitrate concentrations of 2.96 to 7.49 mmol m-3, challenging previous hypotheses. This equatorial enrichment is supported by low nitracline ranging from 5.47 to 46.19 m. Beyond the equator, the subequatorial and subtropical regions, despite the observed deepening of the ML, present low nitrate concentrations (less than 0.5 mmol m-3) with a nitracline that does not reach the ML. However, at 6°S and 9°S, a respective increase in nitrate content of 0.66 mmol m-3 and 1.2 mmol m-3 influenced by internal waves, advection and surface currents is observed. Temperature, salinity, and atmospheric fluxes shape nutrient distribution and primary production dynamics. These findings illuminate the intricate relationships between oceanographic processes, nutrient availability, and marine ecosystem productivity. A holistic understanding is crucial for sustainable resource management and fisheries in the equatorial Atlantic and beyond.publishedVersio
Multi-scale patterns in the structure of fish and fouling communities associated with seaweeds in marinas
Get PDFRedistribution of biodiversity represents a key challenge for understanding scales of spatial variation in natural marine communities. With increasing coastal urbanization, artificial structures are proliferating, with impacts on natural habitats, yet we have limited knowledge on the spatial scales of processes operating over their associated species assembly. This is exemplified by novel communities establishing along and around floating infrastructures, such as pontoons in marinas. In this study, we explored multi-scale patterns in the diversity and community structure of fouling seaweeds, invertebrates and fish communities associated with pontoons in 18 marinas, distributed along ∼1000 km of coastline in NW France. With respect to the distribution of marinas across 3 distinct ecoregions, we predicted that their seaweed communities would follow spatial patterns reported in native communities from rocky shores. This hypothesis was poorly supported, and the variation among ecoregions (8%) was largely explained by the abundance of nonindigenous kelps. However, as anticipated, we observed important variability among and within marinas in all response variables (e.g. richness of sessile invertebrates and fish). These variations were related to contrasting sea surface temperature regimes among marinas, along with a number of explanatory variables (e.g. distance to marina entry). As also hypothesized, fouling and fish communities covaried with kelp biomass, although covariations were strengthened at the scale of the region and at the scale of the marina and pontoon when nonindigenous and native kelp were considered, respectively. Specificities in distributions and influences of foundation species in urban environments could be worth scrutinizing to inform their management.publishedVersio
Validation of the coupled physical-biogeochemical ocean model NEMO-SCOBI for the North Sea-Baltic Sea system
Get PDFThe North Sea and the Baltic Sea still experience eutrophication and deoxygenation despite large international efforts to mitigate such environmental problems. Due to the highly different oceanographic frameworks of the two seas, existing modelling efforts have mainly focused on only one of the respective seas, making it difficult to study interbasin exchange of mass and energy. Here, we present NEMO–SCOBI, an ocean model (NEMO-Nordic) coupled to the Swedish Coastal and Ocean Biogeochemical model (SCOBI), that covers the North Sea, the Skagerrak–Kattegat transition zone and the Baltic Sea. We address its validity to further investigate biogeochemical changes in the North Sea–Baltic Sea system. The model reproduces the long-term temporal trends, the temporal variability, the yearly averages and the general spatial distribution of all of the assessed biogeochemical parameters. It is particularly suitable for use in future multi-stressor studies, such as the evaluation of combined climate and nutrient forcing scenarios. In particular, the model performance is best for oxygen and phosphate concentrations. However, there are important differences between model results and observations with respect to chlorophyll a and nitrate in coastal areas of the southeastern North Sea, the Skagerrak–Kattegat transition zone, the Gulf of Riga, the Gulf of Finland and the Gulf of Bothnia. These are partially linked to different local processes and biogeochemical forcing that lead to a general overestimation of nitrate. Our model results are validated for individual areas that are in agreement with policy management assessment areas, thereby providing added value with respect to better contributing to international programmes aiming to reduce eutrophication in the North Sea–Baltic Sea system.publishedVersio
Varying temporal trends in the levels of six groups of legacy persistent organic pollutants (POPs) in liver of three gadoid species from the North Sea
Get PDFFrom 2005 to 2019, three gadoid species, Atlantic cod (Gadus morhua), haddock (Melanogrammus aeglefinus) and saithe (Pollachius virens), were sampled approximately every third year in the northeastern part of the North Sea. Liver samples were analyzed to investigate levels and temporal trends of six groups of persistent organic pollutants (POPs): polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT) and its degradation products, hexachlorocyclohexanes (HCHs), hexachlorobenzene (HCB), trans-nonachlor (TNC), and polybrominated diphenyl ethers (PBDEs). Some of the highest average concentrations were found in cod, the levels otherwise being similar between the three species and mostly below established threshold values. The levels of all the contaminants except HCB and TNC were higher than previously reported for cod and haddock in the Barents Sea. Significantly decreasing levels were found for Σ7PCBs, ΣDDTs, ΣHCHs and Σ15PBDEs in all three species, and for TNC in haddock and saithe, while there was no significant trend for TNC in cod. HCB levels increased significantly in cod and haddock and showed only a minor decrease in saithe. The observed time trends of legacy POPs demonstrate the persistence of some of the studied pollutants despite efforts to eliminate them from the marine environment.publishedVersio
Vgll3 regulates the timing of puberty in farmed Atlantic salmon, but it does not explain family discordance in male maturation following different smolt production regimes
Get PDFAtlantic salmon (Salmo salar) farming is moving towards extended periods of land-based production to minimise the time at sea, but this increases the risk of unwanted male sexual maturation. As the timing of puberty is driven by genetics (e.g. vgll3) and the environment, optimising rearing strategies and broodstock management may help alleviate the problem. Subsequently, we used a domesticated strain of vgll3 heterozygous broodstock to produce three all-male half-sibling families using three different production regimes to assess the timing of first puberty. Firstly, “large smolts” were produced in a flow-through system on 13 °C freshwater and constant light from first feeding (day 0) up to 1 kg (day 354). The mean incidence of pubertal males increased from 2% at 30 g, up to 78% at 1 kg. Genetics explained a significant (p < 0.05) amount of the variation, with 93, 71, and 34% of the expected early, intermediate, and late maturing vgll3 genotypes being pubertal on day 354, respectively. In addition, pubertal males in the early vgll3 genotype were found at the first sampling at ≈30 g, while it was not observed in the heterozygous and late genotypes until the fish were ≈90 g and ≈280 g, respectively. Secondly, “post-smolts” were produced by switching half the large smolts to 13 °C seawater at 420 g (day 272) and growing them in tanks to 0.95 kg (day 354). This led to a significant 14% reduction in the total incidence of puberty by day 354 compared to the large smolts. However, the regulation of pubertal timing by vgll3 did not interact with salinity. Thirdly, traditional “under-yearling” smolts were produced using periods of natural or manipulated temperature and photoperiod, followed by transfer to a sea-cage at 150 g in December (day 290) where they stayed for one year until harvest at 4.75 kg (day 648). None of these fish were mature at sea transfer, but 9% were at harvest, with 22, 7, and 2% of the early, intermediate, and late vgll3 genotypes being mature, respectively. When comparing the regimes, family effects outside of vgll3 on the prevalence of sexual maturation were significant for the land-based regimes (family means from 46 to 93% on day 354), but not in sea-cages (family means from 7 to 11% on day 648) and evidence for either vgll3 allele being dominant was mixed. Vgll3 also had minimal effects on body size/growth in any regime/family. In conclusion, i) selecting for the late vgll3 allele is an effective method to delay puberty over a range of production regimes, ii) family effects outside of vgll3 were not consistent across regimes, and iii) using seawater reduced the incidence of precocious puberty during land-based production.publishedVersio
Characterizing humpback whale behavior along the North-Norwegian coast
Get PDFStudying movement patterns of individual animals over time can give insight into how they interact with the environment and optimize foraging strategies. Humpback whales (Megaptera novaeangliae) undertake long seasonal migrations between feeding areas in polar regions and breeding grounds in tropical areas. During the last decade, several individuals have had up to a 3-month stop-over period around specific fjord-areas in Northern Norway to feed on Norwegian spring-spawning (NSS-) herring (Culpea harengus L.). Their behavioral patterns during this period are not well understood, including why some whales seemingly leave the fjords and then later return within the same season.publishedVersio
Vandringsmønster hos postsmolt av laks fra Namsen i 2022 og 2023 - Rapport til Mattilsynet
Get PDFEnglish summary Sammendrag I 2022 og 2023 ble vandring av laksesmolt fra Namsen til kysten overvåket ved hjelp av akustisk telemetri, hvor lyttebøyer var plassert både i elven og fjorden. Totalt ble 389 laksesmolt merket over de to årene. Resultatene viser at mesteparten av utvandringen skjedde rundt månedsskiftet mai-juni, med en median dato på 30. mai i 2022 og 3. juni i 2023. I begge år startet utvandringen sammenfallende med økende vannføring. Utvandring fra elv til fjord ble observert gjennom hele døgnet uten noen klare preferanser for dag eller natt.Vandringsmønster hos postsmolt av laks fra Namsen i 2022 og 2023 - Rapport til MattilsynetpublishedVersio
Exploring ecosystem effects of underwater noise in the nordic seas, using the NoBa-Atlantis E2E model
Get PDFUnderwater noise generated by human activities, such as shipping and seismic surveys, has emerged as a growing concern. Despite the mounting evidence that noise negatively impacts marine mammals, fish, and invertebrates, end-to-end ecosystem models often overlook noise as a stressor. This omission is due to the complexity of studying noise’s influence on entire populations and ecosystems, making it difficult to gauge the potential total effects accurately. In this study, we implemented potential effects of underwater noise in the Atlantis ecosystem modeling framework. Noise effects on organisms were simulated through reduced growth and consumption rates, increased mortality and movement away from noisy areas. The noise module was tested by a Morris sensitivity analysis on most of the fish, mammal and invertebrate species in the model. The species were aggregated into 12 groups perturbed with six different noise levels, with the spatial dimension taken into account by repeating the analysis under varying spatial configurations. The results revealed substantial systemic effects from increased vulnerability to noise from zooplankton, while marine mammal noise vulnerability had relatively little impact, in line with earlier Atlantis studies. Additionally, the coastal area exhibited significantly higher biomass variability, indicating a need for more research in this region where noise is expected to increase the most. These results provide an initial estimation of the potential effects of noise at the ecosystem level in the Nordic and Barents Seas. However, for improved realism of the noise module in future studies, we emphasize the need to develop response functions for each species’ sensitivity to noise. Understanding such species-specific sensitivities will be crucial in devising effective strategies to mitigate the detrimental consequences of underwater noise on marine ecosystems.acceptedVersio
Creating better internships by understanding mentor challenges: findings from a series of focus groups
Get PDFDespite demands to make higher education more relevant beyond academia, and a growing body of work testifying to the benefits of work-relevance programs (e.g., work-placements, or internships) for both students and the companies that host them, there is limited information available for those aiming to optimize these programs. For example, few have explored the challenges and needs of internship supervisors. Here, we focus on the experiences of supervisors in biology and geology programs across three Norwegian institutions. Specifically, through a series of focus groups, we asked internship supervisors about their motivations for serving as student mentors, any challenges they had faced, and what higher-education institutions could do to better prepare them for hosting students at their workplaces.publishedVersio
Exogenous growth hormone (GH) increases dimension and reduces strength of vertebrae in Atlantic salmon (Salmo salar)
Get PDFGrowth hormone (GH) administration increases bone strength in rats, mainly through alterations of the dimensional proportions of vertebrae. However, similar knowledge is lacking in other clades. In order to pursue this, Atlantic salmon were fed diets with high or low vitamin C and E and administered a slow-release implant of bovine GH. While neither the diets or the GH treatment affected growth, GH reduced condition factor and carcass-somatic index, and increased the hepatosomatic and visceral-somatic indexes. GH had an impact on the dimensional proportions of the vertebrae and increased the relative dorso-ventral and lateral vertebra diameters. Moreover, GH decreased the mechanical strength of the vertebra, both with (modulus of elasticity, failure point) and without (stiffness) normalizing the mechanical data for the dimensions of the vertebrae. Diet did not impact on the vertebra morphometry or mechanical strength. RNA-seq of vertebra centra show that several genes associated with bone growth and remodelling were affected by GH, while there was an interactive effect between diet vitamin level and GH on several genes associated with lipid metabolism. The data may suggest that exogenous GH affects the bone cellular mechanisms of Atlantic salmon postsmolts in such a way that their vertebrae increase in diameter but not length, not disturbing growth in body length. The GH and diet effects on lipid metabolism associated genes indicate a complex regulation of the lipids stored inside the vertebral column by endocrine and nutritional factors.publishedVersio