Comstock Jacqueline, Henderson Lillian C, Close Hilary G, Liu Shuting, Vergin Kevin, Worden Alexandra Z, Wittmers Fabian, Halewood Elisa, Giovannoni Stephen, Carlson Craig A
Department of Ecology, Evolution and Marine Biology, Marine Science Institute, University of California Santa Barbara, Santa Barbara, CA 93106, United States.
Department of Ocean Sciences, Rosenstiel School of Marine, Atmospheric, and Earth Science, University of Miami, Miami, FL 33149, United States.
ISME Commun. 2024 Jul 12;4(1):ycae090. doi: 10.1093/ismeco/ycae090. eCollection 2024 Jan.
Passive sinking flux of particulate organic matter in the ocean plays a central role in the biological carbon pump and carbon export to the ocean's interior. Particle-associated microbes colonize particulate organic matter, producing "hotspots" of microbial activity. We evaluated variation in particle-associated microbial communities to 500 m depth across four different particle size fractions (0.2-1.2, 1.2-5, 5-20, >20 μm) collected using pumps at the Bermuda Atlantic Time-series Study site. pump collections capture both sinking and suspended particles, complementing previous studies using sediment or gel traps, which capture only sinking particles. Additionally, the diagenetic state of size-fractionated particles was examined using isotopic signatures alongside microbial analysis. Our findings emphasize that different particle sizes contain distinctive microbial communities, and each size category experiences a similar degree of change in communities over depth, contradicting previous findings. The robust patterns observed in this study suggest that particle residence times may be long relative to microbial succession rates, indicating that many of the particles collected in this study may be slow sinking or neutrally buoyant. Alternatively, rapid community succession on sinking particles could explain the change between depths. Complementary isotopic analysis of particles revealed significant differences in composition between particles of different sizes and depths, indicative of organic particle transformation by microbial hydrolysis and metazoan grazing. Our results couple observed patterns in microbial communities with the diagenetic state of associated organic matter and highlight unique successional patterns in varying particle sizes across depth.
海洋中颗粒有机物质的被动沉降通量在生物碳泵以及向海洋内部的碳输出过程中起着核心作用。与颗粒相关的微生物在颗粒有机物质上定殖，形成微生物活动的“热点”。我们在百慕大大西洋时间序列研究站点，使用泵收集了四个不同粒径级分（0.2 - 1.2、1.2 - 5、5 - 20、>20μm）的颗粒，评估了至500米深度的与颗粒相关的微生物群落变化。泵收集既捕获沉降颗粒也捕获悬浮颗粒，补充了以往仅使用沉积物或凝胶陷阱（仅捕获沉降颗粒）的研究。此外，在进行微生物分析的同时，利用同位素特征研究了分级粒径颗粒的成岩状态。我们的研究结果强调，不同粒径包含独特的微生物群落，并且每个粒径类别在群落随深度的变化程度上相似，这与之前的研究结果相矛盾。本研究中观察到的稳健模式表明，颗粒停留时间相对于微生物演替速率可能较长，这表明本研究中收集的许多颗粒可能沉降缓慢或呈中性浮力。或者，沉降颗粒上的快速群落演替可以解释不同深度之间的变化。对颗粒的补充同位素分析揭示了不同大小和深度颗粒之间组成上的显著差异，表明微生物水解和后生动物放牧导致有机颗粒发生转化。我们的结果将观察到的微生物群落模式与相关有机质的成岩状态联系起来，并突出了不同粒径在不同深度下独特的演替模式。
