Nutrients and contaminants are monitored in commercially produced feed materials, fish feed and farmed Atlantic salmon (Salmo salar) in Norway. In this study, we present data for several nutrients such as fatty acids, vitamin D and selenium, and contaminants like dioxins, polychlorinated biphenyls (PCBs), organochlorine pesticides, mercury, cadmium, lead and arsenic in fish feed and fillet of Atlantic salmon for the years 2006–2021. The results showed co-occurring trends in concentrations of several of the nutrients and contaminants in fish feed and fillet of Atlantic salmon for the time period studied. The long-chain omega-3 fatty acids eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and docosapentaenoic acid (DPA) decreased in concentrations over the time period studied, while the concentrations of alpha-linolenic acid, linoleic acid and oleic acid increased in both feed and fillet. The concentration of several contaminants, including polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (dioxins) and dioxin-like PCBs (dl-PCBs), non-dioxin-like indicator PCBs (PCB-6), DDT and mercury, decreased in both feed and salmon fillet. The most pronounced changes in concentration were observed between 2006 and 2014, while the levels remained more stable from 2014 to 2021. Although the level of some of the nutrients decreased, a portion of Atlantic farmed salmon fillet remains a good source of EPA, DHA, vitamin D and selenium. The reduction in levels of contaminants, such as dioxins and dl-PCBs and mercury, in salmon fillets, has lowered the health risk associated with the presence of these contaminants in salmon.

Commercially cultivated kelp (seaweed) species represent a potential dietary source of iodine but may also put consumers at risk of excessive intakes upon frequent consumption. This study investigated warm seawater (WSW) treatment as a simple method for reducing the iodine content of Alaria esculenta and Saccharina latissima. Iodine concentrations decreased in both kelps upon W-SW exposure at 45( degrees)C, i.e. by 38 % and 78 %, respectively, in A. esculenta and S. latissima after 1 min and 51 % and 88 % after 2 min. Longer treatments resulted in further decrease in A. esculenta whereas only marginal further reduction in iodine concentrations were achieved in S. latissima. No reduction in iodine concentration was measured in S. latissima following treatment at 35 C-degrees (not tested for A. esculenta). W-SW treatment at 45 C-degrees induced loss of biomass in both kelps although the total retention was notably higher in A. esculenta compared to S. latissima. Among the analysed macronutrients, potassium and mannitol were associated with the lowest retentions. Losses of micronutrients (incl. vitamin B1 and B9) and trace elements were also measured in both kelps. The retention of free glutamate was high in both species suggesting that W-SW exposure does not negatively affect the umami potential of the final ingredients for food. Based on portions contributing 600 mu g iodine, W-SW-treated A. esculenta was more nutritious than a comparable ingredient from S. latissima, with nutritionally relevant contribution (> 15 % of dietary reference intake (DRI)) per portion (4.6 g dry A. esculenta vs. 1.2 g S. latissima) of sodium, and notable contributions (> 5 % of DRI) of other minerals (calcium, magnesium and potassium) and vitamin B9. Short W-SW treatment is a simple approach that could be implemented in commercial kelp production and contribute to reducing the risk of excessive dietary iodine exposure from seaweed consumption.

Fillets from a total of 1245 Northeast Atlantic mackerel (Scomber scombrus) sampled in different fishing areas of the Northeast Atlantic during 2007-2016 were analysed for mercury, cadmium, arsenic and lead using ICPMS. Mercury levels varied from <0.01 to 0.36 mg/kg wet weight (ww) with a total mean of 0.046 mg/kg ww and were significantly higher in Skagerrak than in the North Sea, the Norwegian Sea and west of Scotland. Cadmium concentrations varied from <0.002 to 0.16 mg/kg ww with a mean value of 0.015 mg/kg ww. Only 0.24 % and 0.16 % of the sampled fish exceeded the EU's maximum levels for cadmium and mercury, respectively. Arsenic levels varied between 0.43 and 6.9 mg/kg ww with a mean value of 2.2 mg/kg ww and showed seasonal variation following variations in fat content. Lead concentrations were low and below the analytical limit of quantification (LOQ) in 97 % of the samples.

Seaweeds must be stabilised shortly after harvesting to avoid rapid deterioration. To handle large amounts harvested during a short period, freezing and frozen storage until utilisation or further processing is one of the methods used industrially. The aim of this study was to assess the effects of different freezing and thawing procedures on Alaria esculenta by analysis of the chemical composition of the seaweed and the drip loss expelled during thawing. Thawing of industrially frozen A. esculenta resulted in a drip loss of 57% of wet weight. The drip loss had a dry matter content of 7% of wet weight, of which 71% was mineral content. Analysis showed that, of the dry matter excluding ash, alanine, aspartic acid, and mannitol were the main components lost to the drip loss. Experiments with a second batch of A. esculenta looking at quick and slow freezing and thawing showed that quick freezing resulted in a significantly lower drip loss than slow freezing; 20% compared to up to 42% of wet weight. Dry matter and mineral content of the drip loss of these samples were all around 6% of wet weight and 31% of dry weight. For some applications it might be of interest to reduce the concentration of potentially toxic elements such as iodine and heavy metals, but due to a high loss of other biomass this was not very effectively done by freezing and thawing. For preservation purposes, quick freezing is the best alternative to retain seaweed biomass.

The effects of steam- or warm water treatments of the brown seaweed Saccharina latissima on iodine content and nutrient and sensory profiles were investigated. Warm freshwater or seawater treatments reduced the dry weight iodine content by 73% and 59%, respectively. Steam treatment was less efficient and only reduced the iodine content by 26%. Freshwater treatment resulted in a greater reduction in total solids and loss of water-soluble components, mainly reducing the content of ash and carbohydrates. Seawater treatment had a small effect on total solid content but altered the mineral profile leading to an increase in sodium and decrease in potassium content. The sensory profiles reflected the observed differences in composition as it revealed a significantly higher saltiness of the seawater-treated sample compared to other treatments, as well as a higher umami intensity compared to the freshwater-treated sample. The latter was characterized by low scores across all sensory attributes, indicating greater loss of flavour-active compounds. Further, including seawater-treated S. latissima at relatively low levels (0.5% and 1%) significantly altered the flavour of a commercial spinach soup compared to the same preparation without seaweed. Therefore, warm water treatment using seawater could be an alternative method for lowering the iodine content in brown seaweed while limiting nutrient loss and maintaining its flavour potential for applications in the food industry.

The Norwegian Research Council project SusKelpFood addresses the challenges of producing kelp for Nordic and European food industries. Project Leader, Dr Pierrick Stévant, Ph.D and Dr Arne Duinker, Ph.D explain their research, undertaken to bolster the efficient production of safe, nutritious and tasty seaweed food products.

Raw oysters are considered a culinary delicacy but are frequently the culprit in food-borne norovirus (NoV) infections. As commercial depuration procedures are currently unable to efficiently eliminate NoV from oysters, an optimisation of the process should be considered. This study addresses the ability of elevated water temperatures to enhance the elimination of NoV and Tulane virus (TuV) from Pacific oysters (Crassostrea gigas). Both viruses were experimentally bioaccumulated in oysters, which were thereafter depurated at 12 °C and 17 °C for 4 weeks. Infectious TuV and viral RNA were monitored weekly for 28 days by TCID50 and (PMAxx-) RT-qPCR, respectively. TuV RNA was more persistent than NoV and decreased by < 0.5 log10 after 14 days, while NoV reductions were already > 1.0 log10 at this time. For RT-qPCR there was no detectable benefit of elevated water temperatures or PMAxx for either virus (p > 0.05). TuV TCID50 decreased steadily, and reductions were significantly different between the two temperatures (p < 0.001). This was most evident on days 14 and 21 when reductions at 17 °C were 1.3–1.7 log10 higher than at 12 °C. After 3 weeks, reductions > 3.0 log10 were observed at 17 °C, while at 12 °C reductions did not exceed 1.9 log10. The length of depuration also had an influence on virus numbers. TuV reductions increased from < 1.0 log10 after seven days to > 4.0 log10 after 4 weeks. This implies that an extension of the depuration period to more than seven days, possibly in combination with elevated water temperatures, may be beneficial for the inactivation and removal of viral pathogens.

The Northeast Arctic cod (Gadus morhua) is the world's northernmost stock of Atlantic cod and is of considerable ecological and economic importance. Northeast Arctic cod are widely distributed in the Barents Sea, an environment that supports a high degree of ecosystem resiliency and food web complexity. Here using 121 years of ocean temperature data (1900-2020), 41 years of sea ice extent information (1979-2020) and 27 years of total mercury (Hg) fillet concentration data (1994-2021, n = 1999, >= 71% Methyl Hg, n = 20) from the Barents Sea ecosystem, we evaluate the effects of climate change dynamics on Hg temporal trends in Northeast Arctic cod. We observed low and consistently stable, Hg concentrations (yearly, least-square means range = 0.022-0.037 mg/kg wet wt.) in length-normalized fish, with a slight decline in the most recent sampling periods despite a significant increase in Barents Sea temperature, and a sharp decline in regional sea ice extent. Overall, our data suggest that recent Arctic amplification of ocean temperature, "Atlantification," and other perturbations of the Barents Sea ecosystem, along with rapidly declining sea ice extent over the last similar to 30 years did not translate into major increases or decreases in Hg bioaccumulation in Northeast Arctic cod. Our findings are consistent with similar long-term, temporal assessments of Atlantic cod inhabiting Oslofjord, Norway, and with recent investigations and empirical data for other marine apex predators. This demonstrates that Hg bioaccumulation is highly context specific, and some species may not be as sensitive to current climate change-contaminant interactions as currently thought. Fish Hg bioaccumulation-climate change relationships are highly complex and not uniform, and our data suggest that Hg temporal trends in marine apex predators can vary considerably within and among species, and geographically. Hg bioaccumulation regimes in biota are highly nuanced and likely driven by a suite of other factors such as local diets, sources of Hg, bioenergetics, toxicokinetic processing, and growth and metabolic rates of individuals and taxa, and inputs from anthropogenic activities at varying spatiotemporal scales. Collectively, these findings have important policy implications for global food security, the Minamata Convention on Mercury, and several relevant UN Sustainable Development Goals.

Risk- benefit assessments of seafood require high-quality food composition data. In accordance with EU regulations, Atlantic salmon (Salmo salar) has conventionally been sampled using the Norwegian Quality Cut (NQC), a sub-cut of the middle section of the fish, in Norwegian surveillance programs. By comparing the contents of nutrients and contaminants in 34 samples of farmed Atlantic salmon, we aimed to evaluate the representativeness of the NQC compared with the whole fillet. Of the 129 analytes evaluated, eight single analytes, in addition to 25 different fatty acids, showed significant differences between the cuts. Significant differences were evident for total fat, including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and sum PCB-6, but not for the sum of dioxins and dioxin-like PCBs. We further suggest that the NQC may still be used in large-scale sampling of Atlantic salmon, and that the whole fillet would be preferable when analysing the content of nutrients.

Bioaccumulation of persistent organic pollutants (POPs) in marine fish may pose a health risk to human consumers. Using data from ∼8400 individuals of 15 fish species collected in the North-East Atlantic Ocean (NEAO), we assessed concentrations of individual POP congeners, including dioxins, polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs). POPs analyses were performed with accredited methods using high-resolution gas chromatography/high-resolution mass spectrometry, gas chromatography/tandem mass spectrometry (GC-MS/MS) and GC/MS. The results showed that POPs congener composition profiles were more influenced by fish species than by geography. However, due to long range transport from emissions at lower latitudes, lighter congeners made a larger contribution to the total POPs concentrations in the northernmost areas compared to southern regions. A model was developed to elucidate the relative effects of several factors on POPs concentrations and showed that variation among and within fish species was associated with fat content, fish size, trophic position, and latitude. For the first time, POPs concentrations were shown to increase nonlinearly with fat content, reaching an asymptotic plateau when fat content was > 10%. This study explored detailed POP congener profiles and the factors associated with POPs accumulation in commercially relevant fish harvested from the NEAO.

Suboptimal iodine status is a prominent public health issue in several European coun-tries. Brown algae have a high iodine content that, upon intake, may exceed the recommended dietary intake level, but iodine bioavailability has been reported to be lower than from potassium iodide (KI) and highly depends on algae species. Further, potential negative effects from other components in algae, such as cadmium (Cd) and arsenic (As), have also been addressed. In this study, we observed a lower bioavailability of iodine from farmed sugar kelp (Saccharina latissima) than from KI in female Wistar IGS rats. Urinary iodine excretion was 94–95% in rats fed KI and 73–81% in rats fed sugar kelp, followed by increased faecal iodine levels in rats fed sugar kelp. No effects on body weight, feed efficiency, or plasma markers for liver or kidney damage were detected. The highest dose of iodine reduced plasma free thyroxine (fT4) and total T4 levels, but no significant effects on circulating levels of thyroid-stimulating hormone (TSH) and free triiodo-thyronine (fT3) were detected. Faeces and urine measurements indicate that 60–80% of total As and 93% of Cd ingested were excreted in rats fed 0.5 and 5% kelp. Liver metabolomic profiling demonstrates that a high inclusion of sugar kelp in the diet for 13 weeks of feeding modulates metabolites with potential antioxidant activity and phytosterols.

Oily seafood is an important food source which contains several key nutrients beneficial for human health. On the other hand, oily seafood also contains persistent organic pollutants (POPs), including the dioxin-like compounds (DLCs) polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDD/Fs) and dioxin-like-polychlorinated biphenyls (dl-PCBs), potentially detrimental to human health. For a comprehensive comparison of the beneficial and potentially adverse health effects of seafood consumption, risk-benefit analyses are necessary. Risk-benefit analyses require reliable quantitative data and sound knowledge of uncertainties and potential biases. Our dataset comprised more than 4000 analyses of DLCs and more than 1000 analyses each of docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and vitamin D in the three most important Norwegian commercial oily seafood species: Atlantic herring (Clupea harengus), Atlantic mackerel (Scomber scombrus) and farmed Atlantic salmon (Salmo salar). The levels of several DLC congeners were below the limit of quantification (LOQ), making estimation of true levels challenging. We demonstrate that the use of upper bound substitution of censored data will overestimate, while lower bound substitution will underestimate the actual levels of DLCs. Therefore, we implement an alternative robust statistical method by combining Maximum Likelihood Estimation, Regression on Order Statistics and Kaplan-Meier analyses, which is better suited for providing estimations of levels of these contaminants in seafood. Moreover, we illustrate the impact of the toxic equivalency factor (TEF) system on estimation of the sums of DLCs by comparing the TEF system to an alternative system of relative effect potency (REP) factors (Consensus Toxicity Factors). The levels of nutrients and contaminants were related to adequate intake (AI) and tolerable weekly intake (TWI), respectively. We used AI and the TWI values established by the European Food Safety Authority (EFSA). The benefit and the risk were further viewed in the context of the Norwegian average intake of oily fish, and the Norwegian governmental official dietary recommendations of oily fish. Our results showed that both benefit and risk are met at the levels found of nutrients and DLCs in oily seafood. The comprehensive quantitative data presented here will be a key for future risk-benefit assessment of oily fish consumption. Together, our results underline that a refined formalized integrative risk-benefit assessment of oily fish in the diet is warranted, and that the data and methodology presented in this study are highly relevant for future integrated and multidisciplinary assessment of both risks and benefits of seafood consumption for human health.

Mercury (Hg) pollution in the ocean is an issue of global concern, however bioaccumulation regimes of this ubiquitous pollutant in marine apex predators have important knowledge gaps. Our fish length and stable isotope (delta N-15 and delta C-13) normalized data of Greenland halibut (GH) (Reinhardtius hippoglossoides) showed that Hg bioaccumulation in fillet tissue decreased by similar to 35-50 %, over a ten-year period from 2006 to 2015 (n = 7 individual sampling years). Hg was predominantly in the methylmercury form (>77 %). Results from a Bayesian information theoretic model showed that GH Hg concentrations decreased with time and its associated declines in Hg air emissions, estimated trophic position, and a potentially lower degree of demersal prey use as indicated by temporal trend shifts in nitrogen (delta N-15) and carbon (delta C-13) stable isotope values. GH trophic shifts accounted for about one third of the observed temporal reduction in Hg. Our study demonstrates the importance of simultaneously considering Hg emissions, food web dynamics and trophic shifts as important drivers of Hg bioaccumulation in a marine, deep water fish species and highlights the effectiveness of Hg regulations on ocean apex predator Hg concentrations and overall seafood safety.

There is a lack of scientific evidence regarding the stability of iodine and mercury during cooking and processing of seafood. In this study, the iodine and mercury content were determined after thawing frozen fillets of Atlantic cod (Cadus morhua), and further in raw compared to boiled, pan-fried, and oven baked fillets. Iodine was determined by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) and mercury by atomic absorption spectrophotometry with Direct Mercury Analyzer (DMA-80). Thawing of the cod resulted on average in a 12% loss of iodine to the thawing water. Boiling significantly decreased the total content of iodine per slice of cod fillet corresponding to the concentration of iodine found in the boiling water. Pan-frying and oven-baking did not cause any significant changes of the total iodine content per slice of cod fillet, although iodine content per 100 g increased due to weight reduction of the cod slices from evaporation of water during preparation. For mercury, we found minimal changes of the different cooking methods. In summary, the findings in our study show that boiling had the greatest effect on the iodine content in the cod fillets. Type of cooking method should be specified in food composition databases as this in turn may influence estimation of iodine intake.

The increase in the global population demands more biomass from the ocean as future food and feed, and the mesopelagic species might contribute significantly. In the present study, we evaluated the food and feed safety of six of the most abundant mesopelagic species in Norwegian fjords. Trace elements (i.e., arsenic, cadmium, mercury, and lead), organic pollutants (i.e., dioxins, furans, dioxin-like polychlorinated biphenyls, and polybrominated flame-retardants), and potentially problematic lipid compounds (i.e., wax esters and erucic acid) were analyzed and compared to existing food and feed maximum levels and intake recommendations. Furthermore, contaminant loads in processed mesopelagic biomass (protein, oil, and fish meal) was estimated using worst-case scenarios to identify possible food and feed safety issues. While most undesirables were low considering European food legislation, we identified a few potential food safety issues regarding high levels of fluoride in Northern krill, wax esters in glacier lanternfish, and long-chain monounsaturated fatty acids in silvery lightfish. Our estimates in processed biomass indicated high levels of undesirable trace elements in the protein fraction, frequently exceeding the maximum levels for feed ingredients. However, in fish meal, almost no exceedances were seen. In the oil fraction, dioxins and furans were above the maximum levels, given for food and feed ingredients. The present study is crucial to enable an evaluation of the value of these species; however, more data is needed before proceeding with large-scale harvesting of mesopelagic biomass.

Brown crab Cancer pagurus is appreciated as seafood in several European countries. However, cadmium levels in crabs can be elevated and their consumption may pose a hazard for human health. To assess if cadmium poses a threat to food safety in Norway, crabs were sampled at two different locations along the Norwegian coast: one in the South of Norway and one in the North of Norway. Cadmium levels were determined in different tissues (claw meat, hepatopancreas and inner meat). To highlight specific risk factors for cadmium, the concentration of cadmium was related to different exogenous (location, cooking and season) and physiological (size, sex, moulting stage, gonad maturation stage, condition) factors. The results confirmed previous findings of much higher cadmium levels in brown crab sampled in the North of Norway compared to the South. Cooking of crabs further led to higher concentrations in claw meat. The effect of season on cadmium levels was different in the North and South and no clear patterns could be identified, probably due to a high inter-individual variation in cadmium levels. Size showed a correlation with the total amount of cadmium for crabs in the North indicating an accumulation of cadmium over time; together with a slower growth, this may lead to the higher cadmium levels, observed in the crabs from Northern Norway. The risk connected to cadmium exposure when consuming brown crab mainly depends on the consumption pattern, the parts of the crab consumed and the origin of the crab. Regardless of origin, the consumption of claw meat does not display a consumer health risk. However, the consumption of meals consisting of inner meat only and inner meat of brown crab from Northern Norway may pose a health risk.

Samples of cultivated edible kelps Alaria esculenta and Saccharina latissima were analysed for their cadmium, iodine and inorganic arsenic contents. The inorganic arsenic levels were low in both species but samples of A. esculenta had relatively high cadmium contents (up to 2.01 mg kg −1 dry weight (DW)), and iodine levels were high in S. latissima samples (up to 6568 mg kg −1 DW), exceeding the limits established by the French food safety authority for both elements. Simple soaking treatments in warm fresh water (32 °C) reduced the iodine in S. latissima and treatment of A. esculenta in hypersaline solution (2.0 M NaCl) reduced the relative cadmium content. However, both treatments affected the nutrient content of the biomass, illustrated by considerable variations in DW and the content of bioactive compounds (e.g. minerals, polyphenols, fucoxanthin). Health risks associated with the consumption of these seaweed species were estimated using risk factors based on established tolerable intake levels. The contribution of A. esculenta to dietary cadmium intake does not appear to pose a threat to the consumer while the daily consumption of S. latissima leads to excessive iodine intakes. The moderate consumption of these kelps will, on the other hand, improve the iodine status in iodine-deficient populations.

Methylmercury (MeHg) is a potent neurotoxin that bioaccumulates in seafood. Co-occurrence of selenium (Se) may affect the bioavailability and toxicity of MeHg in organisms. Here we report the concentrations of total mercury (Hg) and Se in 17 teleost fish species (n = 8459) sampled during 2006-2015 from the North East Atlantic Ocean (NEAO) and evaluate species variation and effects of geography. Mean Hg concentration ranged from 0.04 mg kg-1 ww in Atlantic mackerel (Scomber scombrus) and blue whiting (Micromesistius poutassou) to 0.72 mg kg-1 ww in blue ling (Molva dypterygia). Se concentrations were less variable and ranged from 0.27 mg kg-1 ww in Atlantic cod (Gadus morhua) to 0.56 mg kg-1 ww in redfish (Sebastes spp.). The mean Se:Hg molar ratio ranged from 1.9 in blue ling to 43.3 in mackerel. Pelagic species had the lowest Hg concentrations and the highest Se:Hg ratios, whereas demersal species had the highest Hg concentrations and the lowest Se:Hg ratios. Se and Hg concentrations were positively correlated in 13 of the 17 species. Hg concentrations increased from the North to South in contrast to the Se:Hg molar ratio which exhibited the opposite trend. Fish from fjord and coastal areas had higher concentrations of Hg and lower Se:Hg molar ratios compared to fish sampled offshore. All species had average Se:Hg molar ratios >1 and Hg concentrations were largely below the EU maximum level of 0.5 mg kg-1 ww with few exceptions including the deep water species tusk (Brosme brosme) and blue ling sampled from fjord and coastal habitats. Our results show that two fillet servings of tusk, blue ling or Atlantic halibut (Hippoglossus hippoglossus) exceeded the tolerable weekly intake of MeHg although the surplus Se may possibly ameliorate the toxic effects of MeHg. However, some individuals with selenium deficiencies may exhibit greater sensitivity to MeHg.