Chemical composition of <i>Ulva</i> species sampled in Boka Kotorska Bay (Kotor Bay) Montenegro

Abstract This study examined the taxonomic diversity and biochemical composition of Ulva spp., a macroalga that was collected from eight sites along the Boka Kotorska Bay shoreline (Montenegro). The aim was to determine whether site-specific or interspecific variation influences the biochemical traits of Ulva populations. Species were identified through morphological features supported by tufA sequencing. Elemental composition, ash, amino acids, and fatty acids were quantified to assess biochemical heterogeneity. Carbon ranged from 19.8–27.4 %, nitrogen 1.3–4.0 %, and sulfur 2.4–5.6 % DW. Ash content varied widely (25.4–48.9 %), while total amino acids (TAA) spanned 0.02–0.05 μg mg −1 . Essential amino acids (%EAA = 28.7–73.7 %) and branched-chain amino acids (%BCAA = 26.3–80.1 %) showed pronounced divergence. Total fatty acids differed significantly among samples, peaking in sample S3 (1,287 ± 29 μg mg −1 ) and were lowest in sample S6 (260 ± 8 μg mg −1 ). Palmitic acid (C16:0) dominated all samples (171–578 μg mg −1 ). These differences indicate that local environmental and taxonomic factors jointly influence Ulva biochemical composition. The intra-Bay variability highlights the adaptive potential of Ulva populations and their promise as sustainable sources of biomolecules. Future studies integrating multi-marker taxonomy, seasonal monitoring, and environmental characterization are recommended to clarify the drivers of this biochemical heterogeneity.