Substrate availability may limit the response of tropical bacterioplankton biomass to warming

IF 3.8 1区 地球科学 Q1 LIMNOLOGY
Xosé Anxelu G. Morán, Maria Ll. Calleja, Federico Baltar, Luis Silva, Mohd Ikram Ansari, Paloma Carrillo de Albornoz, Carlos M. Duarte, Christian Lønborg
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Abstract

The response of heterotrophic bacterioplankton to the addition of macrophytic dissolved organic matter (DOM) and temperature was investigated in the Red Sea. We added 40 μmol C L−1 of leachates obtained from seagrass and mangrove leaves to natural bacterial communities, incubated them at three temperatures (25.5°C found in situ plus 3°C below and above that value) and monitored the microbial and biogeochemical responses over 4 d. Seagrass and mangrove DOM, important allochthonous sources in tropical oligotrophic regions, had distinct chemical characteristics compared to unamended seawater, with mangrove substrates containing comparatively more nitrogen and protein-like fluorescent DOM than seagrass. Specific growth rates (μ) increased twofold in the seagrass and mangrove treatments (1.0 and 0.8 d−1, respectively) relative to the seawater control (0.4 d−1). The biomass of heterotrophic bacteria generally reflected μ changes, reaching maximum values of 16.8 and 17.3 μg C L−1 in the seagrass and mangrove treatments, respectively, compared to just 2.6 μg C L−1 in seawater. The increase in μ values due to experimental warming followed the metabolic theory of ecology, mostly because of enhanced exoenzymatic activity, while cell size decreased as predicted by the temperature–size rule (mean −3% per °C increase). Although the labile nature of the specific seagrass and mangrove DOM leachates was clearly demonstrated, we conclude that tropical heterotrophic bacteria may have limited capability to increase their biomass as a consequence of future warming, even in the presence of high loadings of macrophytic DOM.

Abstract Image

底质可用性可能限制热带浮游细菌生物量对气候变暖的反应
我们在红海研究了异养浮游细菌对添加大型溶解有机物(DOM)和温度的反应。我们向天然细菌群落中添加了 40 μmol C L-1 的海草和红树林叶片浸出物,在三种温度下(原位 25.5°C 加上低于和高于该值的 3°C)进行培养,并在 4 d 内监测微生物和生物地球化学反应。海草和红树林 DOM 是热带寡营养地区重要的同源物,与未加添加剂的海水相比,它们具有不同的化学特征,其中红树林基质比海草含有更多的氮和蛋白质类荧光 DOM。与海水对照组(0.4 d-1)相比,海草和红树林处理的特定生长率(μ)增加了两倍(分别为 1.0 和 0.8 d-1)。异养细菌的生物量普遍反映了 μ 的变化,在海草和红树林处理中分别达到 16.8 和 17.3 μg C L-1 的最大值,而在海水中仅为 2.6 μg C L-1。实验升温导致的 μ 值增加遵循了生态学的新陈代谢理论,主要是由于外酶活性增强,而细胞大小则根据温度-大小规则预测有所减小(平均每升高一摄氏度减小 3%)。尽管特定海草和红树林 DOM 浸出物的易变性得到了清楚的证明,但我们得出的结论是,热带异养细菌在未来气候变暖的情况下增加生物量的能力可能有限,即使在大型 DOM 负荷较高的情况下也是如此。
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来源期刊
Limnology and Oceanography
Limnology and Oceanography 地学-海洋学
CiteScore
8.80
自引率
6.70%
发文量
254
审稿时长
3 months
期刊介绍: Limnology and Oceanography (L&O; print ISSN 0024-3590, online ISSN 1939-5590) publishes original articles, including scholarly reviews, about all aspects of limnology and oceanography. The journal''s unifying theme is the understanding of aquatic systems. Submissions are judged on the originality of their data, interpretations, and ideas, and on the degree to which they can be generalized beyond the particular aquatic system examined. Laboratory and modeling studies must demonstrate relevance to field environments; typically this means that they are bolstered by substantial "real-world" data. Few purely theoretical or purely empirical papers are accepted for review.
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