Weed competition, persistent seed banks, and management costs can limit crop productivity in organic farming. A two-year field experiment was conducted in southern Finland to evaluate the effects of pea (Lathyrus oleraceus Lam.), oats (Avena sativa L.), and camelina (Camelina sativa (L.) Crantz.), grown as pure stands and as three-crop mixtures at varying seeding densities, on weed diversity and suppression. The seeding densities (%) were 50:20:30 and 33:33:33 of the pure stand density of pea, oats, and camelina in 2022 and 50:50:50 and 33:33:33 of the pure stand density in 2023. Weed diversity was assessed at five sampling times, species were identified and analyzed for biomass, richness, Shannon-Wiener index (H), evenness, and dominance. Weed diversity and suppression varied with crop composition, growth stage, and seasonal conditions. In 2022, the 33% mix had the highest H (2.22) and evenness (0.77), enhancing weed suppression while controlling dominance. In 2023, pure oats had the highest H (1.65) and evenness (0.87), and pure peas had the lowest H (1.41) and evenness (0.67). Although pure oat stands provided the strongest weed suppression, crop mixtures enhanced species diversity and evenness, suggesting potential for more balanced weed management in organic systems, with short-term results indicating potential benefits for weed control.

Nordic agricultural production faces multiple challenges in a warming climate. Although predictions indicate an overall increase in annual mean precipitation in northern Europe, increasing temperatures may lead to earlier snowmelt and drying of soil during springtime, as well as longer growing season and higher evapotranspiration increasing the risk of summer droughts. The use of cover crops in agriculture is one of the climate-smart practices that have multiple benefits, such as increasing SOC, reducing N losses, and increasing biodiversity. Still, the question whether cover crops and their diversity increase resilience against climate extremes such as drought, and how the combined effects of cover crops, their diversity and drought affect greenhouse gas (GHG) emissions from soil remain largely unknown. We studied the effect of cover crop diversity and drought on soil and crop C and N dynamics and GHG (CO2, N2O) emissions in a biodiversity cropland experiment with or without shelters that remove 50% of incoming precipitation for two years. GHG emissions were measured with the manual dark chamber method twice a week during growing season and once a week during off-season. Soil temperature and water content were measured continuously, and the soil was sampled for mineral N and total C and N analysis seasonally.The preliminary results showed that reduced rainfall did not affect N2O emissions significantly during the growing season in either year. During off-season, reduced rainfall led to elevated N2O emissions irrespective of cover crop diversity treatments. However, the effect was absent in the second year, indicating that factors other than drought were driving the N2O production. Contrary to N2O, drought did not affect CO2 emissions during off-season in either year. Overall, during both years off-season N2O emissions dominated the annual N2O balance in all diversity treatments, highlighting the importance of including off-season measurements to the annual N2O balance estimation.

The stoichiometric ratios of carbon (C), nitrogen (N) and phosphorus (P) in soils influence nutrient availability for soil microorganisms and thus the efficiency of C sequestration. Subsoil horizons are known to be potential sinks for sequestering substantial amounts of C. However, limited information is available regarding soil C:N:P stoichiometry in the subsoil and its role in regulating soil organic C stocks. This study investigated the vertical variations in C, N and P stocks and their ratios down to one meter in boreal agricultural soils. We further explored the response of soil C:N:P stoichiometry to the soil physical characteristics and the subsequent impacts on C stocks. The stocks of C and N decrease sharply with soil depth, whereas P shows a more gradual decline, resulting in a decrease in the ratios of C:P and N:P. Stoichiometric ratios were more constrained in the topsoil compared with subsoil, and were estimated to be on the average 83:6:1 and 21:2:1 in the topsoil and subsoil, respectively. C stock in the subsoil layers were more strongly limited by stoichiometric ratios (N:P) than those in the topsoil. From the stoichiometric perspective, agricultural soils in Finland exhibit an excess of total P but are limited in C and N for soil microorganisms. Soil compaction amplifies the already existing nutrient imbalance, potentially reducing C stocks in subsoil. This study deepens our understanding of the coupling and interaction among soil C, N and P in relation to soil C sequestration.

Organic agricultural products are increasingly favored by European consumers due to their environmental benefits; however, the low productivity of organic farming remains a major barrier to its adoption. While three-crop mixtures is a promising strategy to enhance the competitiveness of organic systems, its impact on primary productivity, carbon (C) balance, and greenhouse gas (GHG) emissions remains poorly understood. This study investigated the effects of three-crop mixtures—comprising pea (Lathyrus oleraceus Lam.), oat (Avena sativa L.), and camelina (Camelina sativa L.)—on GHG (N2O, CH4, and CO2) emission rates, growing-season cumulative emissions, global warming effect (GWE), crop yield, and net ecosystem carbon balance (NECB). Field experiments were conducted over two growing seasons on an organically managed clay loam soil in Finland. While three-crop triggered peak N2O emissions that were 26–53

The effect of field hydrology on microbial gas production in a black schist-based acid sulfate soil was investigated to find out if conditions in the field are conducive to greenhouse gas formation and to see if the overlying peat functions as protection against oxidation of the sulfidic material. Soil air composition and hydrological conditions were observed in an agricultural peatland, which contains black schists and acid sulfate soil properties beneath a layer of peat 15-60 cm thick at different observation sites. The field was drained with open ditches with 20 m spacing. Groundwater level was high, particularly at low elevations of the field, and the acid sulfate subsoil was at or near saturation for much of the investigated period (15 months). Within the soil profile, CO2 concentration increased and O-2 concentration decreased with increasing depth, indicating microbial activity, while the variation of N2O content within the profile was not as clear. The acid sulfate subsoil was predominantly saturated with water and consequently had slow gas exchange and only modest microbial activity. These results explain previous results of unexpectedly low greenhouse gas emissions from this location. They also suggest that a thick peat layer may protect against the oxidation of underlying sulfidic horizons, even if the extent of protection remained inconclusive.

Low yields remain a primary obstacle to the expansion of organic farming in Europe. While legume-based mixed cropping enhances land-use efficiency, three-crop mixtures remain understudied compared to binary systems. We evaluated the vegetative and generative growth of pea (Lathyrus oleraceus Lam.), oats (Avena sativa L.), and camelina (Camelina sativa (L.) Crantz.) in sole stands versus three-crop mixtures in southern Finland. Experiments were conducted over two years using varying relative seeding densities (including 50:20:30, 50:50:50, and 33:33:33). Biomass dynamics and seed quality were analyzed using analysis of variance (ANOVA), while interspecific interactions were quantified using the relative interaction index (RII) and land equivalent ratio (LER). In 2022, mixtures increased oat seed protein by 11% relative to sole crops, achieving a biomass LER of 1.17. In 2023, oats exhibited strong competitive dominance (RII > 0.3), which concurrently reduced camelina quality. Notably, the 33:33:33 mixture consistently achieved a biomass LER > 1.2 and marked improvements in pea growth rates. Across all mixtures, the seed yield LER reached 1.04. These results suggest that three-crop mixtures can enhance productivity in Nordic organic agriculture with minimal quality trade-offs. Practically, we recommend the equal seeding density (33:33:33) as the optimal configuration for maximizing resource use efficiency, though further optimization of species combinations is encouraged.

Removing sediment from lakes is effective for restoration but involves high disposal costs. Repurposing these sediments as fertilizers could address phosphorus (P) shortages. Our study evaluated the fertilizing potential of sediments from Finnish lakes (Matjarvi, Kutajarvi, Kymijarvi, and Enonselka) and two basins of Estonia's Lake Peipsi (Peipsi and Lammijarv). We conducted a greenhouse experiment with ryegrass growing in sand, by applying to sand either 25 kg ha-1 of mineral P fertilizer or sediments with the same amount of bioavailable P according to their ironbound P content, and using sand without any P fertilizer as a negative control. We also tested soil amendments like lime, biochar, or arbuscular mycorrhiza to enhance sediment-derived P availability. Results showed ryegrass biomass and P uptake in sediment treatments were 126 % and 133 % of those without added P. Sediments provided P and other macro- and micronutrients, enhancing plant growth. Organic matter contributed additional P, except for Enonselka and Lammijarv sediments. Contrary to our hypothesis, plant P uptake occurred even from sediments with high iron to P mass ratios, suggesting hypoxic conditions contributed to P solubilization. Biochar and lime amendments increased plant biomass, particularly in the Kymijarvi treatment, to 106 % of those without amendment, and decreased zinc (Zn) uptake, important for avoiding Zn contamination. These findings highlight the dual benefits of sediment removal for lake restoration and as a substitute for mineral P fertilizers. Further research is needed to explore the long-term effects of using lake sediments as fertilizers and identify optimal practices for enhancing nutrient availability under field conditions.

Cover crops are recognized as a climate-smart agricultural practice that increases soil organic carbon content (SOC). As carbon (C) and nitrogen (N) cycles are coupled, an increase in SOC can impact the N cycle and nitrous oxide (N2O) emissions. Another major driver affecting N cycling and N2O emissions is soil moisture. With the increasing risk of summer droughts and wetter conditions during the off-season in Northern Europe, it is important to understand how drying-wetting and agricultural practices together affect N cycling and N2O emissions.To address this knowledge gap, we conducted a pot experiment with clay soil in controlled greenhouse conditions simulating summer drought with bare soil pots and oats sown either alone, with Italian ryegrass, or with alfalfa as plant treatments. The pots were initially watered to 70% degree of saturation to ensure that the plants start to grow, after which half the pots were let dry to 40% degree of saturation. The plants were grown for 36 days. At the end of the growth period, soil N2O emissions were measured over three days. Following this, the pots were sampled destructively, and total N in plants, roots, and soil, as well as mineral N in soil, were analysed. Additionally, a follow-up pool-dilution incubation experiment using 15N-labelling with bare soil and soil previously covered with oats was conducted to study the effect of moisture content and rewetting on gross N transformation rates.Contrary to our expectations, the results from the pot experiment showed that N2O emissions in the plant treatments were higher in drought conditions than in moist conditions. This does not support our results from a cover crop field trial where reduced rainfall did not affect N2O emissions during the growing season. However, during off-season reduced rainfall in the field led to higher N2O emissions. Preliminary results from the incubation indicated lower N2O emissions under drought conditions, with increased emissions upon rewetting and the highest emissions under moist conditions. The presence of plants decreased soil N2O emissions in both experiments, but the plant species did not affect the emissions nor the total mineral N content in soil. As expected, in the pot experiment, total mineral N content in soil was higher in drought conditions than in moist soil as well as in bare soil compared with soil with growing plants. Results on the effects of drought and plants on gross N transformations during the incubation experiment with 15N labelling will be presented later.

BACKGROUND:The recommended transition toward more plant-based diets, particularly containing legumes, requires a wider knowledge of plant protein bioavailability. Faba beans are cultivated at different latitudes and are used increasingly in human nutrition. OBJECTIVES:We aimed to assess the nutritional quality of faba bean protein in healthy volunteers equipped with an intestinal tube to implement the ileal 15N balance method. METHODS:Nine volunteers completed the study (7 males, 2 females, aged 33 ± 10 y, BMI: 24.7 ± 2.6 kg/m2). They were equipped with a nasoileal tube. After fasting overnight, they ingested a test meal consisting of cooked mash of dehulled faba bean seeds (20 g protein per serving of approximately 250 g) intrinsically labeled with 15N. Samples of ileal contents, plasma, and urine were collected over an 8-h postprandial period. Undigested nitrogen (N) and amino acids (AAs) were determined using isotopic MS, and subsequently, ileal digestibility and digestible indispensable amino acid score (DIAAS) were calculated. The measurement of postprandial deamination allowed calculation of the net postprandial protein utilization (NPPU). RESULTS:The ileal N digestibility was 84.1% ± 7.7%. Postprandial deamination represented 19.2% ± 3.6% of ingested N, and the NPPU was 64.7% ± 9.7%. The ileal digestibility of individual AAs varied from 85.1% ± 13.7% for histidine to 94.2% ± 3.6% for glutamine + glutamate. The mean AA digestibility was ∼6 percentage points higher than the digestibility of N, reaching 89.8% ± 5.9%, whereas indispensable AA digestibility was 88.0% ± 7.3%. Histidine and tryptophan were the first limiting AAs [DIAAS = 0.77 (calculated by legume-specific N-to-protein conversion factor 5.4); 0.67 (by default factor 6.25)]. Sulfur AAs were limiting to a lesser extent [DIAA ratio = 0.94 (N × 5.4); 0.81 (N × 6.25)]. CONCLUSIONS:Protein ileal digestibility of cooked, dehulled faba beans in humans was moderate (<85%), but that of AAs was close to 90%. Overall protein quality was restricted by the limited histidine and tryptophan content. This trial was registered at clinicaltrials.gov as NCT05047757.

Biochars have notable potential in sequestering atmospheric carbon over long terms and offer various agricultural and environmental co-benefits. However, there is limited information about the long-term effects of added biochars, as there are only handful of continuously monitored biochar field experiments expanding over a decade, and especially poorly have been studied the long-term effects from boreal regions. The soils in northern colder boreal regions typically have higher carbon content and undergo continuous freeze-thaw cycles. Therefore, effects of biochars in these regions may differ from those observed in warmer climates.We studied the effects of a single application of softwood biochars on two contrasting boreal agricultural soils (nutrient-poor, coarse textured Umbrisol and fertile, fine-textured Stagnosol), both with high initial soil organic carbon contents, over 13 years following the application in 2010 or 2011. We focused on plant yield formation as well as nutrient uptake dynamics of all major Finnish field crops, as well as on soil physical properties and greenhouse gas emissions.We found that the ability of biochar to enhance the supply of nutrients to plants and hence to improve the crop biomass yield exists in boreal conditions, although these effects were minimal and not consistent over the years. Biochar notably increased plant K content, and reduced the plant content and uptake of Al and Na in several years in Stagnosol. The relative plant contents of Cd and Ni in Umbrisol, and P, K, Mg, S, Al, Cu, Fe and Ni in Stagnosol increased over the years. Despite these increased plant contents, no significant improvement was observed in crop biomass yield by added biochar over the first eight years.The enhanced plant available water and reduced bulk density previously reported during the initial years were faded in long-term, likely due to dilution of biochar concentration in topsoil. However, the potential of biochar to affect N2O emission persisted, even seven years after the application, this contributed to reduced yield-normalized non-CO2 GHG emissions. In the presentation, we will share also the preliminary results for the latest growing seasons 2019–2022.

Inefficient use of phosphorus (P) fertilizers leads to the transfer of P into water bodies, causing their eutrophication. Sediment removal is a promising lake restoration strategy that removes nutrients including P accumulated in lake sediments, and opens the opportunity to use removed nutrients in agriculture. In the present study, we investigated the effects of using a thick layer of sediment from the eutrophic Lake Mustijärv on plant growth, and estimated the environmental impacts of different sediment application methods by analyzing greenhouse gas emissions, N and P leaching, aggregate stability, and soil biota. The field experiment (2017-2020) was established on the lake shore with the following treatments: the agricultural control soil (Soil) surrounding the lake, pure sediment (Sed), biochar-treated sediment (SB), and biochar and soil mixed with sediment (SSB). The sediment-based treatments resulted in a similar grass growth performance to the Soil. The availability of most macro- and micronutrients including P (75 vs. 21 g m-3) were far greater in the Sed compared to the Soil. The sediment-based growing media emitted more CO2 than the Soil (579 vs. 400 mg CO2 - C m-2 h-1) presumably due to the high rate of organic matter decomposition. The bacterial and fungal community structures of the Sed were strongly differentiated from those of Soil. Also, Sed had lower bacterial diversity and a higher abundance of the bacterial phyla associated with solubilizing P including Proteobacteria and Chloroflexi. Sediment-based growing media increased more than seven times the risk of mineral N and P leaching, and the biochar treatment only had a short-lived beneficial effect on reduction of the sediment's leached P concentration. The sediment application rate should be adjusted to match the crop requirements to minimize greenhouse gas emissions and nutrient leaching when upscaling the case study to larger lakes with similar sediment properties.

In acid sulfate (AS) soils, organic rich topsoil and subsoil horizons with highly variable acidity and moisture conditions and interconnected reactions of sulfur and nitrogen make them potential sources of greenhouse gases (GHGs). Subsoil liming can reduce the acidification of sulfidic subsoils in the field. However, the mitigation of GHG production in AS subsoils by liming, and the mechanisms involved, are still poorly known. We limed samples from different horizons of AS and non-AS soils to study the effects of liming on the N2O and CO2 production during a 56-day oxic and subsequent 72-h anoxic incubation. Liming to pH ≥ 7 decreased oxic N2O production by 97–98 % in the Ap1 horizon, 38–50 % in the Bg1 horizon, and 34–36 % in the BC horizon, but increased it by 136–208 % in the C horizon, respectively. Liming decreased anoxic N2O production by 86–94 % and 78–91 % in Ap1 and Bg1 horizons, but increased it by 100–500 % and 50–162 % in BC and C horizons, respectively. Liming decreased N2O/(N2O + N2) in anoxic denitrification in most horizons of both AS and non-AS soils. Liming significantly increased the cumulative oxic and anoxic CO2 production in AS soil, but less so in non-AS soil due to the initial high soil pH. Higher carbon and nitrogen contents in AS soil compared to non-AS soil agreed with the respectively higher cumulative oxic N2O production in all horizons, and the higher CO2 production in the subsoil horizons of all lime treatments. Overall, liming reduced the proportion of N2O in the GHGs produced in most soil horizons under oxic and anoxic conditions but reduced the total GHG production (as CO2 equivalents) only in the Ap1 horizon of both soils. The results suggest that liming of subsoils may not always effectively mitigate GHG emissions due to concurrently increased CO2 production and denitrification.

Data from proximal soil sensors can facilitate digital soil mapping at high spatial resolutions. However, their use for predicting static soil properties, such as texture, is affected by spatio-temporal changes in environmental and measurement conditions. In this research study, seasonal changes in spatial patterns and repeatability of data provided by a platform that simultaneously measures the red (Red) and near infrared (NIR) reflectance, apparent soil electrical conductivity (ECa), temperature, and volumetric moisture content of topsoil (at 3-6 cm depth) were assessed. Test fields are located in Southern Finland with textures dominated by clay and fine sandy till. During single scans, mean relative differences between the data from duplicated measurement points ranged from similar to 4% to 6% and were the highest for temperature and Red values. The consistency of spatial patterns across seasons (spring and autumn 2021 and 2022) was the highest for ECa values, and the lowest for NIR. ECa and moisture were significant for predicting the clay contents at a cereal grain crop site, whereas temperature was significant at grass ley sites. Errors were generally lower when using spring data compared with autumn data (RMSE ranging from 4.8% to 11.1% for the data from different fields and measurement dates). For the fields, where static soil properties change at small spatial scales, spatially detailed moisture and temperature data support the understanding of seasonal changes in the spatial patterns derived from multi-sensor data, and the corresponding changes in the performance of calibration models.

Eutrophication increases the input of labile, algae-derived, organic matter (OM) into lake sediments. This potentially increases methane (CH4) emissions from sediment to water through increased methane production rates and decreased methane oxidation efficiency in sediments. However, the effect of OM lability on the structure of methane oxidizing (methanotrophic) and methane producing (methanogenic) microbial communities in lake sediments is still understudied. We studied the vertical profiles of the sediment and porewater geochemistry and the microbial communities (16S rRNA gene amplicon sequencing) at five profundal stations of an oligo-mesotrophic, boreal lake (Lake Pääjärvi, Finland), varying in surface sediment OM sources (assessed via sediment C:N ratio). Porewater profiles of methane, dissolved inorganic carbon (DIC), acetate, iron, and sulfur suggested that sites with more autochthonous OM showed higher overall OM lability, which increased remineralization rates, leading to increased electron acceptor (EA) consumption and methane emissions from sediment to water. When OM lability increased, the abundance of anaerobic nitrite-reducing methanotrophs (Candidatus Methylomirabilis) relative to aerobic methanotrophs (Methylococcales) in the methane oxidation layer of sediment surface decreased, suggesting that Methylococcales were more competitive than Ca. Methylomirabilis under decreasing redox conditions and increasing methane availability due to their more diverse metabolism (fermentation and anaerobic respiration) and lower affinity for methane. Furthermore, when OM lability increased, the abundance of methanotrophic community in the sediment surface layer, especially Ca. Methylomirabilis, relative to the methanogenic community decreased. We conclude that increasing input of labile OM, subsequently affecting the redox zonation of sediments, significantly modifies the methane producing and consuming microbial community of lake sediments.ImportanceLakes are important natural emitters of the greenhouse gas methane (CH4). It has been shown that eutrophication, via increasing the input of labile organic matter (OM) into lake sediments and subsequently affecting the redox conditions, increases methane emissions from lake sediments through increased sediment methane production rates and decreased methane oxidation efficiency. However, the effect of organic matter lability on the structure of the methane-related microbial communities of lake sediments is not known. In this study, we show that, besides the activity, also the structure of lake sediment methane producing and consuming microbial community is significantly affected by changes in the sediment organic matter lability.

The nitrogen availability, that affects the greenhouse gas emission and the trophic level of lakes, is controlled mainly by microbial processes. We measured in a boreal nitrate and iron rich lake how the rates of potential denitrification and dissimilatory nitrate reduction to ammonia (DNRA) are affected by degradability of organic matter and availability of aqueous ferrous iron. We also investigated the microbial community by using 16S rRNA gene and shotgun metagenomic sequencing approach, which allows taxonomic analyses and detection of metagenome-assembled genomes (MAGs) containing genes for both nitrate reduction and iron oxidation. The results show that truncated denitrification, leading to release of nitrous oxide, is favored over dinitrogen production in conditions where the degradability of the organic matter is low. DNRA rates were always minor compared to denitrification and appeared to be independent of the degradability of organic carbon. Reduced iron stimulated nitrate reducing processes, although consistently only DNRA. However, the proportion of MAGs containing DNRA genes was low suggesting chemistry driven stimulation by reduced iron. Nevertheless, the metagenomic analyses revealed unique taxa genetically capable of oxidizing iron and reducing nitrate simultaneously. Overall, the results highlight the spatial variability in microbial community and nitrous oxide emissions in boreal lake sediments.

Factors limiting the production of the greenhouse gases nitrous oxide (N2O) and carbon dioxide (CO2) were investigated in three incubation experiments conducted with soil from top- and subsoil horizons of a peatland which had an acid sulphate mineral subsoil derived from black schists. The effect of moisture was investigated by equilibrating undisturbed soil samples from three horizons (H-2, Cg and Cr) at -10, -60 or -100 cm matric potential and measuring the gas production. In the second experiment, the effects of temperature and various substrates were studied by incubating disturbed soil samples in aerobic conditions at 5 or 20 degrees C, and measuring basal respiration and N2O production before and after adding water, glucose or ammonium into the soil. In the third experiment, the effects of added glucose and/or nitrate on the denitrification in soil samples from four horizons (H1, H2, Cg and Cr were investigated by acetylene inhibition and monitoring of N2O production during a 48-h anaerobic incubation. The production of CO2 in the topmost peat horizon was largest at -10 cm matric potential, and it was larger than those in the mineral subsoil also at -60 and -100 cm potentials. In contrast, drainage seemed to increase N2O production, whereas in the wettest condition the production of N2O in the mineral subsoil was small and the peat horizon was a sink of N2O. Lowering of temperature (from 20 degrees C to 5 degrees C) decreased CO2 production, as expected, but it had almost no role in the production of N2O in aerobic conditions. Glucose addition increased the aerobic production of CO2 in peat, but it had a minor effect in the mineral horizons. Lack of C source (glucose) was limiting anaerobic N2O production in the uppermost peat horizon, while in all other horizons, nitrate proved to be the most limiting factor. It is concluded that peatlands with black schist derived acid sulphate subsoil horizons, such as in this study, have high microbial activity in the peaty topsoil horizons but little microbial activity in the mineral subsoil. These findings are contrary to previous results obtained in sediment-derived acid sulphate soils.

Faculty of Engineering and Natural Sciences, Tampere University, Korkeakoulunkatu 6, FI5 33720, Tampere, Finland 6 Ecosystems and Environment Research Program, Faculty of Biological and Environmental 7 Sciences, University of Helsinki, P.O. Box 65, FI-00014, Helsinki, Finland 8 Department of Agricultural Sciences (Environmental Soil Science), Faculty of Agriculture and 9 Forestry, University of Helsinki, P.O. Box 56, FI-00014, Helsinki, Finland 10 Department of Environmental and Biological Sciences, University of Eastern Finland, 11 Yliopistonranta 1 E, FI-70210, Kuopio, Finland 12 Department of Biological and Environmental Sciences, University of Jyväskylä, Survontie 9 C, 13 FI-40014, Jyväskylä, Finland 14 Department of Forest Mycology and Plant Pathology, Science for Life Laboratory, Swedish 15 University of Agricultural Sciences, Almas allé 5, SE-75651, Uppsala, Sweden 16 17 Current address: Technical University of Denmark, DTU Aqua, Section for Aquaculture, The 18 North Sea Research Centre, P.O. Box 101, DK-9850, Hirtshals, Denmark 19 20 *Corresponding author: Antti J Rissanen, Faculty of Engineering and Natural Sciences, Tampere 21 University, Korkeakoulunkatu 6, FI-33720, Tampere, Finland. Tel: +358 4