This study investigated the year-round metabolomic variation in Fucus serratus (FS) and F. vesiculosus (FV) collected monthly from Danish coastal water around Aarhus Bay. Untargeted high-resolution liquid chromatography–mass spectrometry profiling (LC-HRMS), combined with multivariate data analysis and temporal clustering analysis, revealed that species identity was the primary driver of metabolic separation, followed by seasonal variation. FS showed higher levels of hydrolyzable tannins, flavonoid derivatives, aromatic amino acids, and glutamine-rich peptides, whereas FV was enriched in complex phlorotannins, tricarboxylic acid cycle intermediates, and carnitine derivatives. Temporal analysis identified recurring seasonal patterns across both species, including spring increases in amino acids, purine metabolites, and osmolytes; mid-summer peaks in mannitol and sulfated derivatives; and late-autumn elevations in phenolic compounds and betaine-type osmolytes. Despite apparent interspecific differences, several metabolite groups exhibited similar seasonal dynamics, suggesting shared physiological strategies associated with growth activation in spring, metabolic adjustment during summer to possible increased grazing pressure, and nutrient reallocation prior to winter. These findings provide a comprehensive, high-resolution view of seasonal metabolomic patterns in Fucus spp., offering new insights into their biochemical ecology and supporting the targeted utilization of these species for applications requiring specific metabolite profiles. Finally, this study contributes to the creation or expansion of metabolomic libraries for HRMS specific to Fucus seaweeds.

This pilot study investigated whether reductions in enteric CH₄ emissions could be obtained without affecting dry matter intake (DMI) when iodoform was mixed into total mixed rations (TMRs). The experiment consisted of four periods of 14 d with four rumen-cannulated Holstein dairy cows. In the pre-period, no iodoform was added to TMR, while either 8, 16, or 20 mg iodoform/kg DM was added to TMR in the remaining periods in a change-over design. However, the experiment was not balanced across treatments and periods due to unexpected animal responses in the second period. Dry matter intake and gas exchange were measured the last 3 d in each period using respiration chambers. Rumen grab samples were collected for microbial analyses on d 14. Dry matter intake was unaffected by the addition of iodoform to TMR at or below 20 mg/kg DMI. Methane and H₂ yields (g/kg DMI) quadratically decreased (up to 46%) and increased (up to 1127%), respectively, with the increasing dose. This pilot study indicated that CH₄ reductions can be obtained with an addition of up to 20 mg iodoform/kg DM in the diets of dairy cows without affecting DMI. However, high iodine concentration in iodoform limits its use in commercial herds within the EU.