DataSheet_1_Trophic Ecology of Deep-Sea Megafauna in the Ultra-Oligotrophic Southeastern Mediterranean Sea.docx

The trophic ecology of fourteen species of demersal fishes and six species of demersal decapod crustaceans from the continental slope and rise of the Southeastern Mediterranean Sea (SEMS) was examined using stable isotope analysis. Mean δ13C values among fish species varied by ca. 4.0‰, from -20.85‰ (Macroramphosus scolopax) to -16.57‰ and -16.89‰ (Conger conger and Centrophorus granulosus), showing an enrichment in 13C as a function of depth (200 – 1400 m). Mean δ13C values of the crustaceans showed smaller variation, between -18.54‰ (Aristeus antennatus) and -16.38‰ (Polycheles typhlops). This suggests a shift from pelagic to regenerated benthic carbon sources with depth. Benthic carbon regeneration is further supported by the low benthic-pelagic POM-δ13C values, averaging -24.7 ± 1.2‰, and the mixing model results, presenting relatively low contribution of epipelagic POM to the deep-sea fauna. Mean δ15N values of fish and crustacean species ranged 7.91 ± 0.36‰ to 11.36 ± 0.39‰ and 5.96 ± 0.24‰ to 7.73 ± 0.46‰, respectively, resulting in trophic position estimates, occupying the third and the fourth trophic levels. Thus, despite the proximity to the more productive areas of the shelf, low number of trophic levels (TL~1.0) and narrow isotopic niche breadths (SEAC<1) were observed for demersal crustaceans (TL = 2.94 ± 0.18) and fishes (TL = 3.62 ± 0.31) in the study area – probably due to the ultra-oligotrophic state of the SEMS resulting in limited carbon sources. Our results, which provide the first trophic description of deep-sea megafauna in the SEMS, offer insight into the carbon sources and food web structure of deep-sea ecosystems in oligotrophic marginal seas, and can be further used in ecological modeling and support the sustainable management of marine resources in the deep Levantine Sea.

本研究采用稳定同位素分析（stable isotope analysis），对地中海东南部（SEMS）大陆坡与陆隆区域的14种底层鱼类及6种底栖十足目甲壳动物的营养生态学开展了研究。不同鱼类的平均δ¹³C值差异约4.0‰，范围为-20.85‰（*Macroramphosus scolopax*）至-16.57‰与-16.89‰（*Conger conger*和*Centrophorus granulosus*），结果显示δ¹³C值随水深（200–1400 m）增加而发生¹³C富集。
甲壳动物的平均δ¹³C值变异幅度更小，范围为-18.54‰（*Aristeus antennatus*）至-16.38‰（*Polycheles typhlops*），这表明随着水深增加，碳源从浮游源向再生底栖碳源转变。
底栖-浮游颗粒有机质（particulate organic matter, POM）的δ¹³C值较低，平均值为-24.7 ±1.2‰，混合模型结果显示上层浮游POM对深海动物群的贡献相对较低，进一步佐证了底栖碳的再生过程。
鱼类与甲壳动物的平均δ¹⁵N值范围分别为7.91 ±0.36‰至11.36 ±0.39‰、5.96 ±0.24‰至7.73 ±0.46‰，据此估算得到的营养级位置显示它们分别占据第三、第四营养级。
尽管研究区域毗邻陆架高生产力海域，但底栖甲壳动物（TL=2.94±0.18）与底层鱼类（TL=3.62±0.31）所在的食物网仍呈现出营养级总数偏低、营养级跨度较小（TL差约1.0）以及同位素生态位宽度较窄（SEAC<1）的特征，这大概率是由于地中海东南部处于超寡营养状态，碳源供给有限所致。
本研究首次对地中海东南部的深海大型动物群开展了营养生态学描述，为寡营养边缘海的深海生态系统碳源与食物网结构提供了新的认知视角，同时可进一步应用于生态建模，并有助于黎凡特海深海区域的海洋资源可持续管理。