Data from Natural geochemical markers reveal environmental history and population connectivity of common cuttlefish in the Atlantic Ocean and Mediterranean Sea

Natural markers (δ¹³C and δ¹⁸O stable isotopes) in the cuttlebones of the European common cuttlefish (<i>Sepia officinalis</i>) were determined for individuals collected across a substantial portion of their range in the Northeast Atlantic Ocean (NEAO) and Mediterranean Sea. Cuttlebone δ¹³C and δ¹⁸O were quantified for core and edge material to characterize geochemical signatures associated with early (juvenile) and recent (sub-adult/adult) life-history periods, respectively. Regional shifts in cuttlebone δ¹³C and δ¹⁸O values were detected across the 12 sites investigated. Individuals collected from sites in the NEAO displayed more enriched δ¹³C and δ¹⁸O values relative to sites in the Mediterranean Sea, with the latter also showing salient differences in both markers among western, central and eastern collection areas. Classification success based on cuttlebone δ¹³C and δ¹⁸O values to four geographical regions (NEAO, western, central and eastern Mediterranean Sea) was relatively high, suggesting that environmental conditions in each region were distinct and produced area-specific geochemical signatures on the cuttlebones of <i>S. officinalis</i>. A modified δ¹³C and δ¹⁸O baseline was developed from sites proximal to the Strait of Gibraltar in both the NEAO and Mediterranean Sea to assess potential mixing through this corridor. Nearly, all (95%) of δ¹³C and δ¹⁸O signatures of <i>S. officinalis</i> collected in the area of the NEAO closest to the Strait of Gibraltar (Gulf of Cadiz) matched the signatures of specimens collected in the western Mediterranean, signifying potential movement and mixing of individuals through this passageway. This study extends the current application of these geochemical markers for assessing the natal origin and population connectivity of this species and potentially other taxa that inhabit this geographical area.

本研究针对采集自东北大西洋（Northeast Atlantic Ocean, NEAO）与地中海范围内欧洲普通乌贼（*Sepia officinalis*）分布区大部分区域的个体，测定了其乌贼骨内的天然标志物——碳13（δ¹³C）与氧18（δ¹⁸O）稳定同位素比值。研究分别对乌贼骨的核心组织与边缘组织进行δ¹³C与δ¹⁸O定量分析，以表征对应于幼体早期生活史阶段与亚成体/成体近期生活史阶段的地球化学指纹特征。在所调查的12个采样点中，均检测到乌贼骨δ¹³C与δ¹⁸O值的区域分异现象：相较于地中海海域采样点，东北大西洋海域采样点的个体其δ¹³C与δ¹⁸O值更为富集；且地中海海域的采样点在西、中、东三个采集区域间，两类同位素标志物也均呈现出显著差异。基于乌贼骨δ¹³C与δ¹⁸O值对4个地理区域（东北大西洋、地中海西部、中部与东部）的分类准确率相对较高，这表明各区域的环境条件存在显著差异，并在*S. officinalis*的乌贼骨上形成了具有区域特异性的地球化学指纹特征。本研究基于东北大西洋与地中海直布罗陀海峡附近的采样点，构建了修正后的δ¹³C与δ¹⁸O基线，以评估通过该生物地理廊道的潜在种群混合情况。在靠近直布罗陀海峡的东北大西洋海域（加的斯湾）采集的*S. officinalis*个体中，近95%的δ¹³C与δ¹⁸O指纹特征与地中海西部采集的标本特征相匹配，这表明有个体通过该通道发生移动并产生种群混合。本研究拓展了这类地球化学标志物在评估该物种以及栖息于该地理区域的其他类群的起源地与种群连通性方面的现有应用。