Coexisting picoplankton experience different relative grazing pressures across an ocean productivity gradient.
Coexisting picoplankton experience different relative grazing pressures across an ocean productivity gradient.
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DOI：
10.1073/pnas.2220771120
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发表时间：
2023-10-31
影响因子：
11.1
通讯作者：
Goericke, Ralf
中科院分区：
文献类型：
--
作者：
Landry, Michael R.;Stukel, Michael R.;Selph, Karen E.;Goericke, Ralf
与海洋微生物食物网中的生长过程相比，死亡相互作用了解得较少，但对于确定种群随着环境条件的变化而增加或减少同样重要。加州海流的实验研究揭示了跨越海洋生产力梯度的复杂微生物营养相互作用的新见解。高产量被证明推动了对异养菌的强化放牧，但共享捕食并不会将上移的死亡率转移到类似大小的共生微藻浮游植物上。我们发现，死亡率的数量级变化表明，高度选择性的捕食者或对微生物的环境选择，在生长优势和放牧脆弱性之间进行了紧密的权衡。研究结果挑战了海洋生态系统模型中对死亡过程的简单表述，以及病毒和食草动物在维持多样性方面的明确区别。浮游植物种群[原氯球菌、聚球藻(SYN)和微真核生物]是公海的主要初级生产者，预计随着气候变化将变得更加重要。然而，随着微生物食物网络的复杂性，它们的命运可能会有所不同。在加州目前的生态系统中，浮游微藻的生物量和丰度在中等生产力的水域达到峰值，在生产力较高的水域下降。利用八次穿越明显的CCE营养梯度的游轮的实验数据，我们检验了这样的假设，即这些下降是由对异养菌(HBAC)的强化放牧推动的，异养菌通过共享的捕食者传递给类似大小的微藻浮游植物。结果证实了先前观察到的分布以及细菌丰度、细胞生长和放牧死亡率随着初级生产的显著增加。然而，浮游微藻的死亡率与细菌死亡率趋势不同，在低生产力和高生产力水域之间，SYN上的相对放牧率比HBAC上的相对放牧率下降了12倍。共存种群死亡率比率的巨大变化不能用大小变化来解释，而是表明放牧种群的高度选择性或微生物生长优势和放牧脆弱性的紧密结合的权衡。这些发现挑战了长期以来的观点，即原生动物放牧主要决定微生物群落的总体生物量，而病毒通过“杀死获胜者”来独特地调节多样性。
Mortality interactions are less understood than growth processes in marine microbial food webs but equally important for determining population increases or decreases with changing environmental conditions. Experimental studies in the California Current reveal new insights about complex microbial trophic interactions across ocean productivity gradients. High production is shown to drive intensified grazing on heterotrophic bacteria, but shared predation does not transfer up-shifted mortality to co-occurring picophytoplankton of similar size. We found order-of-magnitude variability in mortality ratios indicative of highly selective predators or environmental selection for microbes with tightly coupled tradeoffs in growth advantages and grazing vulnerabilities. Study results challenge simplistic representations of mortality processes in marine ecosystem models and clear distinctions between virus and grazer roles in diversity maintenance. Picophytoplankton populations [Prochlorococcus, Synechococcus (SYN), and picoeukaryotes] are dominant primary producers in the open ocean and projected to become more important with climate change. Their fates can vary, however, with microbial food web complexities. In the California Current Ecosystem, picophytoplankton biomass and abundance peak in waters of intermediate productivity and decrease at higher production. Using experimental data from eight cruises crossing the pronounced CCE trophic gradient, we tested the hypothesis that these declines are driven by intensified grazing on heterotrophic bacteria (HBAC) passed to similarly sized picophytoplankton via shared predators. Results confirm previously observed distributions as well as significant increases in bacterial abundance, cell growth, and grazing mortality with primary production. Mortalities of picophytoplankton, however, diverge from the bacterial mortality trend such that relative grazing rates on SYN compared to HBAC decline by 12-fold between low and high productivity waters. The large shifts in mortality rate ratios for coexisting populations are not explained by size variability but rather suggest high selectivity of grazer assemblages or tightly coupled tradeoffs in microbial growth advantages and grazing vulnerabilities. These findings challenge the long-held view that protistan grazing mainly determines overall biomass of microbial communities while viruses uniquely regulate diversity by “killing the winners”.
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影响因子：
3.6
作者：
Chabert, P.;d'Ovidio, F.;Ohman, M. D.
通讯作者：
Ohman, M. D.
DOI：
10.1016/j.dsr.2018.08.007
发表时间：
2018-10-01
影响因子：
2.4
作者：
Kelly, Thomas B.;Goericke, Ralf;Stukel, Michael R.
通讯作者：
Stukel, Michael R.
影响因子：
2.5
作者：
Kuipers, BR;Witte, HJ
通讯作者：
Witte, HJ
影响因子：
3.7
作者：
Coello-Camba, Alexandra;Agusti, Susana
通讯作者：
Agusti, Susana
影响因子：
28.3
作者：
Dadon-Pilosof, Ayelet;Conley, Keats R.;Yahel, Gitai
通讯作者：
Yahel, Gitai