The eastern Mediterranean marine ecosystem is undergoing massive modification due to biological invasions, overfishing, habitat deterioration, and climate warming. Our ability to quantify these changes is severely hindered by the lack of an appropriate baseline; most ecological datasets date back a few decades only and show already strong signatures of impact. Surficial death assemblages (DAs) offer an alternative data source that provides baseline information on community structure and composition. In this study, we reconstruct the marine fish fauna of the southern shallow Israeli shelf before the opening of the Suez Canal based on fish otoliths. We quantify the age of the otolith DAs by radiocarbon dating, and describe its taxonomic composition, geographic affinity, and trophic structure. Additionally, we test by radiocarbon dating the hypothesis that Bregmaceros, a presumed Lessepsian invader with continuous presence in the Mediterranean throughout the late Cenozoic, is a relict species. The otolith DA dates back to the mid-Holocene because 75% of the dated otoliths of the native species are older than the opening of the Suez Canal in 1869, suggesting that the DA is a proper baseline for quantifying modern impacts. Consistently, 97% of the otoliths and 88% of the species we collected belong to native Mediterranean species. The native anchovy Engraulis encrasicolus dominates the DAs, although gobiids are the most diverse group (14 species, 28%). The DAs show similar trophic structure to present-day pristine Mediterranean coastal fish assemblages. Two non-indigenous species are recorded here for the first time in the Mediterranean Sea, Amblygobius albimaculatus and Callogobius sp., highlighting the importance of DAs for detecting non-indigenous species. Finally, Bregmaceros otoliths are modern, not supporting the previous hypothesis that the taxon is a Pleistocene relict.

中文翻译：

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全新世鱼类组合为快速变化的东地中海提供基线数据

由于生物入侵、过度捕捞、栖息地恶化和气候变暖，东地中海海洋生态系统正在发生大规模改变。由于缺乏适当的基线，我们量化这些变化的能力受到严重阻碍。大多数生态数据集只能追溯到几十年前，并且已经显示出强烈的影响特征。表面死亡组合 (DAs) 提供了另一种数据源，可提供有关群落结构和组成的基线信息。在这项研究中，我们基于鱼类耳石重建了苏伊士运河开通前以色列南部浅陆架的海洋鱼类群落。我们通过放射性碳测年量化耳石 DA 的年龄，并描述其分类组成、地理亲和力和营养结构。此外，我们通过放射性碳测年测试了假设 Bregmaceros 是一种遗存物种，它是一种假定的莱塞普斯入侵者，在整个新生代晚期一直存在于地中海。耳石 DA 可追溯到全新世中期，因为 75% 的本地物种的已测年耳石比 1869 年苏伊士运河开放时更古老，这表明 DA 是量化现代影响的合适基线。一致地，我们收集的 97% 的耳石和 88% 的物种都属于地中海本土物种。本地鳀鱼 Engraulis encrasicolus 在 DA 中占主导地位，尽管鳀鱼是最多样化的群体（14 种，28%）。DA 显示出与当今原始地中海沿岸鱼类组合相似的营养结构。两种非本土物种首次在地中海记录，Amblygobius albimaculatus 和 Callogobius sp.，突出了 DA 在检测非本土物种方面的重要性。最后，Bregmaceros 耳石是现代的，不支持先前的假设，即该分类群是更新世遗迹。