Philip James

Dulce (Palmaria palmata) is a high-value macroalga that is increasingly being cultivated, with strong potential for waste valorisation in nutrient-rich aquaculture systems (RASs). This study evaluated P. palmata growth in, and nutrient uptake from, commercial Atlantic salmon RAS effluent. A 12-week bench-scale experiment cultivated wild-collected P. palmata (average 10 g fresh weight, FW). These were grown in 1 L glass beakers at three effluent dilutions (25%, RAS25; 50%, RAS50; 100%, RAS100) and in seawater (SW) using 10 replicates. The water samples were analysed for ammonium nitrogen (NH₄-N), nitrate nitrogen (NO₃-N), and orthophosphate (PO₄-P) using a spectrophotometer. RAS25 and RAS50 exhibited 100% survival and maintained a dark red colour, with RAS50 achieving the highest specific growth rate (0.49 ± 0.13% day⁻¹), significantly higher than that of SW and RAS25. In contrast, RAS100 led to complete disintegration by 4–8 weeks with significant colour degradation. SW also exhibited reduced colour and 50% mortality by week 12. Sori’s presence was highest in RAS25/RAS50 (up to 80% at week 8 in RAS50), low in SW (10%), and absent in RAS100. The NH₄-N uptake was notably 3× higher than that of NO₃-N (0.16 vs. 0.05 mg g FW⁻¹ day⁻¹), without differences among the groups. The PO₄-P uptake was significantly higher for RAS50 (0.07 mg g FW⁻¹ day⁻¹) than for RAS100. P. palmata performed best in the diluted RAS effluents, as undiluted conditions led to acute tissue disintegration; the nitrogen and phosphorus uptake from the RAS effluents demonstrates significant potential for nutrient valorisation.

Seaweed aquaculture has experienced significant expansion in recent decades, with global production reaching 34.7 million tonnes in 2020, driven by advancements in cultivation techniques and diverse commercial applications. Europe, and Scandinavian countries such as Norway, are seeing increasing interest. Norwegian seaweed farming is concentrated in the south, and although it faces unique challenges in the north it also has growth potential in northern sites. In this study, a comparison was made of growth rates and biochemical composition of Saccharina latissima grown on farms in southern (Bergen) and northern (Tromsø) Norway. Although, Bergen experiences higher temperatures but less daylight availability than Tromsø, the mean length of S. latissima sporophytes at the two sites did not show a statistically significant difference. Despite generally similar biomass production between the two sites, biochemical analysis revealed significant differences in protein and tissue nitrogen content, with Bergen having higher levels. Iodine content was not significantly different between the sites. This study showed relatively high single-season yields in both Bergen and Tromsø, with Tromsø potentially higher if optimal protocols are followed. Environmental factors like light and temperature significantly affect yields, with faster growth in the north most likely due to the 24-h light periods and northern sites also experience delayed biofouling. The study suggests strong commercial potential for seaweed aquaculture across Norway, with regional differences that can be strategically exploited.

In many countries, such as Norway, there are vast quantities of sea urchins that have formed barrens over large areas of the coastline. Research has shown that removal of sufficient quantities of sea urchins from these barrens can lead to them reverting to a macroalgae forest. Identifying the chemical composition of sea urchins for various uses, such as agricultural fertiliser, would incentivise this sea urchin removal. This study investigates the composition of sea urchins and whether the composition varies when sea urchin collection sites vary both geographically and temporally. Sea urchins were collected from three sites within 10 km of each other in northern Norway at three times through the year. The sea urchins were dried, crushed, powdered, and analysed for nutrient content. An elemental analysis from the sea urchin samples showed high calcium and relatively high magnesium levels; smaller relative quantities of nitrogen, phosphorous, and potassium were also found. Micronutrients such as iron (Fe), zinc (Zn), manganese (Mn), and copper (Cu) were found. More importantly, both primary, macro-, and micronutrients showed high variability when collected from different sites and at different times of the year. This will be a critical consideration when investigating the use of this product as a plant fertiliser or for any other use.

Biofluorescence in certain seaweed species has been studied in association with their respective chlorophyll type and concentration. However, there is a paucity of information on the biofluorescent signature of macroalgal species at different life stages. Here we document that hyperspectral imaging differentiates between the fluorescent signatures of 5 macroalgal species (Ascophyllum nodosum, Fucus vesiculosus, Laminaria digitata, Palmaria palmata, and Saccharina latissima) collected from Tromsø, northern Norway (69-70 °N). Non-reproductive (NR) blades were collected for all species and reproductively mature blades (R) with sori were collected for three species. Hyperspectral imaging of collected blades was conducted under excitation lighting (~445 nm). We further assessed whether biofluorescence is reflected in the reproductive phenology of three selected species, L. digitata, P. palmata, and S. latissima. The spectral radiance of fluorescence emissions was found to be consistently different between R and NR blades. The greatest difference between R and NR blades was between the rhodophyte P. palmata (0.0075 W nm^-1sr^-1m^-2 at 725 nm) followed by the phaeophytes L. digitata (0.03 W nm^-1sr^-1m^-2 at 730-740 nm) and S. latissima (0.00225 W nm^-1sr^-1m^-2 at 735-745 nm). Biofluorescence monitoring with hyperspectral imaging should be considered for further applicability in commercial seaweed operations.

A series of three trials were conducted in the North of Norway at different times of the year. The trials consisted of harvesting sea urchins from four sites, situated within 5km of each other and then holding them in land-based enhancement facilities. They were held at ambient seawater temperatures as well as ambient plus 3.0°C. Samples were taken from the wild at the time of collection and at the end of the enhancement period as well as from the enhanced sea urchins from each site. Results showed that utilising the sea urchins from a variety of sites, even from areas where there is an abundance of sea urchins (sea urchin barrens) and the Gonad Index (GI) is almost always low, is viable in terms of the final, post roe enhancement GI. The results of the study indicate that differences in initial and final GI and the increase in GI between the sites, despite the relatively close proximity, show site selection is most likely not as important as ease of harvesting and sea urchin availability and the positive environmental impact from removal of sea urchins and these are the factors that harvesting strategies should focus on. The study has shown that it is possible to have a relatively consistent roe enhancement from S. droebachiensis from the North of Norway regardless of seasonality (time of year), site selection, and initial GI. Relatively small changes (up to 3°C) in the seawater temperature appear to have a slightly negative impact on enhancement efforts. However, this may vary when larger differences in temperature are experienced.

There is a large amount of coproduct generated by the sea urchin fisheries around the world as well as a growing interest in removing large quantities of undersize and low value sea urchins from barren areas in the northern Atlantic and Pacific coasts as well as other areas around the world. The authors believe there is scope to develop a hydrolysate product from this and this study gives preliminary observations on the characteristics of hydrolysate from the sea urchin Strongylocentrotus droebachiensis. The biochemical composition for S. droebachiensis is moisture 64.1%, protein 3.4%, oil 0.9%, and ash 29.8%. Amino acid composition, molecular weight distribution, lipid‐class, and fatty acid composition are also presented. The authors suggest a sensory‐panel mapping be undertaken on future sea urchin hydrolysates. Possible uses for the hydrolysate are unclear at this stage but the combination of amino acids and the relatively high levels of glycine, aspartic acid, and glutamic acid should be further investigated.

There is an increasing interest in the use of Saccharina latissima (sugar kelp) as food, but the high iodine content in raw sugar kelp limits the daily recommended intake to relatively low levels. Processing strategies for iodine reduction are therefore needed. Boiling may reduce the iodine content effectively, but not predictably, since reductions from 38–94% have been reported. Thus, more information on which factors affect the reduction of iodine are needed. In this paper, sugar kelp cultivated at different depths were rinsed and boiled, to assess the effect of cultivation depth on the removal efficacy of potentially toxic elements (PTEs), especially iodine, cadmium, and arsenic, during processing. Raw kelp cultivated at 9 m contained significantly more iodine than kelp cultivated at 1 m, but the difference disappeared after processing. Furthermore, the content of cadmium and arsenic was not significantly affected by cultivation depth. The average reduction during rinsing and boiling was 85% for iodine and 43% for arsenic, but no significant amount of cadmium, lead, or mercury was removed. Cultivation depths determined the relative effect of processing on the iodine content, with a higher reduction for kelp cultivated at 9 m (87%) compared to 1 m (82%). When not taken into consideration, cultivation depth could mask small reductions in iodine content during rinsing or washing. Furthermore, since the final content of PTEs was not dependent on the cultivation depth, the type and extent of processing determines whether cultivation depth should be considered as a factor in cultivation infrastructure design and implementation, or alternatively, in product segmentation.