Aix-Marseille Université et Université de Toulon, Mediterranean Institute of Oceanography (MIO), CNRS/INSU, IRD, UM 110, Campus Universitaire de Luminy, case 901, 13288, Marseille cedex 9, France.
Université de La Nouvelle-Calédonie, UMR Entropie (UR/IRD/CNRS/IFREMER/UNC), LabEx-CORAIL, BP R4, 98851, Nouméa cedex, New Caledonia.
Mar Environ Res. 2023 Sep;190:106123. doi: 10.1016/j.marenvres.2023.106123. Epub 2023 Aug 4.
To gain insight into the impact of bottom-up changes in the plankton community on planktivorous fish in the context of the decline of small pelagic fisheries in the Northwestern Mediterranean Sea, we have conducted an extensive year-long study. The investigation combined biochemical analyses (proteins, carbohydrates, and lipids) with C and N stable isotope analyses (SIA) to simultaneously study phytoplankton, zooplankton, and eight planktivorous fish species (Engraulis encrasicolus, Sardina pilchardus, Sardinella aurita, Sprattus sprattus, Cepola macrophthalma, Chromis chromis, Boops boops, and Spicara maena). This study is the first to analyze both stable isotope and biochemical compositions in coastal particulate organic matter (POM) size classes (0.7-2.7 μm, 2.7-20 μm, and 20-200 μm), zooplankton size classes (200-300 μm, 300-500 μm, 500-1000 μm, 1000-2000 μm, and >2000 μm), and taxonomic groups. We demonstrated that: (1) POM stable isotope compositions varied based on its spatial origin, the taxonomic composition of its biota, and its biochemical content; (2) δN values increased with zooplankton size classes and groups, indicating different trophic levels; (3) Phytoplankton exhibited a lipid-rich composition (∼55%), while zooplankton and fish muscles were protein-rich (∼61% and ∼66%, respectively). Bayesian stable isotope mixing models revealed that, on average: (1) POM from oceanic waters contributed the most to the POM in the bay (>51%), with a dominance of pico-POM (∼43%); (2) The 200-1000 μm zooplankton primarily consumed nano-POM, the 1000-2000 μm zooplankton mostly consumed micro-POM (∼64%), and the >2000 μm zooplankton also mostly consumed micro-POM; (3) Mesozooplankton (200-2000 μm) constituted the main portion (∼42%) of the diet for planktivorous fish species, while macrozooplankton organisms (>2000 μm) were the primary food resource (∼43%) for both B. boops and S. sprattus. Our study underscores the complexity of the pelagic food web and highlights the bottom-up transfer of organic matter from the smallest phytoplankton size fractions to planktivorous fish.
为了深入了解西北地中海小型中上层渔业衰退背景下浮游生物群落的自下而上变化对食浮游动物鱼类的影响，我们进行了一项广泛的年度研究。该研究结合了生化分析（蛋白质、碳水化合物和脂质）和 C 和 N 稳定同位素分析（SIA），同时研究了浮游植物、浮游动物和 8 种食浮游动物鱼类（Engraulis encrasicolus、Sardina pilchardus、Sardinella aurita、Sprattus sprattus、Cepola macrophthalma、Chromis chromis、Boops boops 和 Spicara maena）。这项研究首次分析了沿海颗粒有机物质（POM）大小类别的稳定同位素和生化组成（0.7-2.7μm、2.7-20μm 和 20-200μm）、浮游动物大小类别的稳定同位素和生化组成（200-300μm、300-500μm、500-1000μm、1000-2000μm 和>2000μm）和分类群。我们证明：（1）POM 的稳定同位素组成取决于其空间来源、生物区系的分类组成和生化含量；（2）δN 值随浮游动物大小类群和组的增加而增加，表明不同的营养水平；（3）浮游植物表现出富含脂质的组成（约 55%），而浮游动物和鱼类肌肉富含蛋白质（分别约为 61%和 66%）。贝叶斯稳定同位素混合模型显示，平均而言：（1）来自海洋的 POM 对海湾内的 POM 贡献最大（>51%），其中以微微 POM 为主（>43%）；（2）200-1000μm 的浮游动物主要消耗纳米 POM，1000-2000μm 的浮游动物主要消耗微 POM（>64%），>2000μm 的浮游动物也主要消耗微 POM；（3）中型浮游动物（200-2000μm）构成了食浮游动物鱼类饮食的主要部分（约 42%），而大型浮游动物（>2000μm）是 B.boops 和 S.sprattus 的主要食物来源（约 43%）。我们的研究强调了浮游食物网的复杂性，并突出了从最小的浮游植物粒径到食浮游动物鱼类的有机物质的自下而上转移。
