Szitenberg Amir, Beca-Carretero Pedro, Azcárate-García Tomás, Yergaliyev Timur, Alexander-Shani Rivka, Winters Gidon
Dead Sea and Arava Science Center, Dead Sea Branch, 8693500, Masada, Israel.
Ben-Gurion University of the Negev, 8858537, Eilat, Israel.
Environ Microbiome. 2022 Apr 15;17(1):18. doi: 10.1186/s40793-022-00412-6.
Halophila stipulacea seagrass meadows are an ecologically important and threatened component of the ecosystem in the Gulf of Aqaba. Recent studies have demonstrated correlated geographic patterns for leaf epiphytic community composition and leaf morphology, also coinciding with different levels of water turbidity and nutrient concentrations. Based on these observations, workers have suggested an environmental microbial fingerprint, which may reflect various environmental stress factors seagrasses have experienced, and may add a holobiont level of plasticity to seagrasses, assisting their acclimation to changing environments and through range expansion. However, it is difficult to tease apart environmental effects from host-diversity dependent effects, which have covaried in field studies, although this is required in order to establish that differences in microbial community compositions among sites are driven by environmental conditions rather than by features governed by the host.
In this study we carried out a mesocosm experiment, in which we studied the effects of warming and nutrient stress on the composition of epiphytic bacterial communities and on some phenological traits. We studied H. stipulacea collected from two different meadows in the Gulf of Aqaba, representing differences in the host and the environment alike. We found that the source site from which seagrasses were collected was the major factor governing seagrass phenology, although heat increased shoot mortality and nutrient loading delayed new shoot emergence. Bacterial diversity, however, mostly depended on the environmental conditions. The most prominent pattern was the increase in Rhodobacteraceae under nutrient stress without heat stress, along with an increase in Microtrichaceae. Together, the two taxa have the potential to maintain nitrate reduction followed by an anammox process, which can together buffer the increase in nutrient concentrations across the leaf surface.
Our results thus corroborate the existence of environmental microbial fingerprints, which are independent from the host diversity, and support the notion of a holobiont level plasticity, both important to understand and monitor H. stipulacea ecology under the changing climate.
海菖蒲海草草甸是亚喀巴湾生态系统中一个具有重要生态意义且受到威胁的组成部分。最近的研究表明，叶片附生生物群落组成与叶片形态存在相关的地理模式，这也与不同程度的水体浊度和营养物浓度相吻合。基于这些观察结果，研究人员提出了一种环境微生物指纹，它可能反映出海草所经历的各种环境压力因素，并可能为海草增加全生物水平的可塑性，帮助它们适应不断变化的环境并实现范围扩张。然而，在实地研究中，环境影响与宿主多样性依赖效应相互关联，很难将二者区分开来，尽管要确定不同地点微生物群落组成的差异是由环境条件而非宿主特征驱动，这是必需的。
在本研究中，我们进行了一项中宇宙实验，研究了升温及营养胁迫对附生细菌群落组成和一些物候特征的影响。我们研究了从亚喀巴湾两个不同草甸采集的海菖蒲，它们在宿主和环境方面均存在差异。我们发现，采集海草的源地是决定海草物候的主要因素，尽管高温会增加茎的死亡率，营养负荷会延迟新芽的出现。然而，细菌多样性主要取决于环境条件。最显著的模式是在无热胁迫的营养胁迫下红杆菌科增加，同时微丝菌科也增加。这两个分类单元共同具有维持硝酸盐还原并随后进行厌氧氨氧化过程的潜力，这可以共同缓冲叶片表面营养物浓度的增加。
因此，我们的结果证实了存在独立于宿主多样性的环境微生物指纹，并支持全生物水平可塑性的概念，这对于理解和监测气候变化下海菖蒲的生态至关重要。
