Deep-sea ecosystems are particularly important to the cycling of matter and energy in the oceans and therefore in regulating Earth’s climate. The Atlantic Ocean is already experiencing significant abiotic changes, with expected warmer temperatures coupled with decreased particulate organic carbon (POC) export flux. However, there is yet a large gap in our understanding of warming impacts on deep benthic ecosystems and in the organic matter processing by benthic organisms in the seafloor. This study employed an experimental approach to assess the single and cumulative effects of two climate change stressors, temperature and POC quality, on macrofaunal benthic assemblages in the Cabo Verde Basin (CVB, Equatorial Atlantic) bathyal continental slope. Incubation enrichment experiments with 13C and 15N labelled diatoms Phaeodactylum tricornutum simulated climate projections for the next century with a balanced design, studying the effect of either increased temperature (+2°C), reduced POC quality (dialysed labile fraction), or both, against a control treatment. We found that echinoderms and polychaetes rapidly ingested labelled algae at rates between 0.02 and 21.9 µg C m−2 d-1. Given a strong spatial variability in macrofaunal biomass, the carbon and nitrogen incorporation by macrofauna was not affected by a + 2 °C warming, by a decreased organic matter quality, or the combination of both factors. Our study provides valuable insights into the biodiversity, biomass, and ecosystem functioning (C and N uptake rates) of deep-sea benthic ecosystems in the N Atlantic, and stress that potential effects of warmer temperatures and POC quality on carbon and nitrogen incorporation by macrofauna remain uncertain. We highlight the value of these experiments to better understand the effects of climate change on deep-sea ecosystems.

中文翻译：

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温度升高和 POC 组成改变对大西洋东北部佛得角深海大型动物群落的影响


深海生态系统对于海洋中物质和能量的循环以及调节地球气候特别重要。大西洋已经经历了重大的非生物变化，预计气温升高，加上颗粒有机碳（POC）出口通量减少。然而，我们对变暖对深层底栖生态系统和海底生物处理有机物的影响的理解还存在很大差距。本研究采用实验方法来评估两种气候变化压力源（温度和 POC 质量）对佛得角盆地（CVB，赤道大西洋）深海大陆坡大型底栖动物组合的单一和累积影响。使用 13C 和 15N 标记的硅藻三角褐指藻进行孵化富集实验，采用平衡设计模拟下个世纪的气候预测，研究温度升高 (+2°C) 和/或 POC 质量降低（透析不稳定部分）的影响对照治疗。我们发现棘皮动物和多毛类动物以 0.02 至 21.9 µg C m−2 d-1 的速率快速摄入标记的藻类。鉴于大型动物生物量存在很强的空间变异性，大型动物的碳和氮吸收不受+2°C变暖、有机质质量下降或这两种因素的组合的影响。我们的研究为北大西洋深海底栖生态系统的生物多样性、生物量和生态系统功能（碳和氮吸收率）提供了宝贵的见解，并强调气温升高和 POC 质量对大型动物碳氮吸收的潜在影响仍然不确定。 我们强调这些实验的价值，以更好地了解气候变化对深海生态系统的影响。