ABSTRACT

Climate change globally accelerates the shrinkage of inland lakes, resulting in increases in both water salinity and dissolved inorganic carbon (DIC). The increases of salinity and DIC generate contrasting effects on microbial primary producers and primary production, however, their combined effects remain unclear in aquatic ecosystems. We hypothesized that increased DIC mitigates the constraints of enhanced salinity on microbial primary producers and primary production. To test this, we employed isotope labeling and molecular methods to explore primary production and four dominant types of microbial primary producers (form IA, IB, IC and ID) in lakes on the Tibetan Plateau. Results showed that DIC was positively correlated with the abundance of the form IAB and ID microbial primary producers and primary production (all P < 0.001) and offset salinity constraints. Structural equation models elucidated that DIC substantially enhanced primary production by stimulating the abundance of form ID microbial primary producers. The abundance of form ID primary producers explained more variations (14.6%) of primary production than form IAB (6%) and physicochemical factors (6.8%). Diatoms (form ID) played a determinant role in primary production in the lakes by adapting to high DIC and high salinity. Our findings suggest that inland lakes may support higher primary productivity in future climate change scenarios.

中文翻译：

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溶解无机碳决定青藏高原湖泊微生物初级生产者和初级生产的丰度

摘要

全球气候变化加速内陆湖泊萎缩，导致水盐度和溶解无机碳（DIC）增加。盐度和 DIC 的增加对微生物初级生产者和初级生产产生对比影响，然而，它们在水生生态系统中的综合影响仍不清楚。我们假设增加的 DIC 减轻了盐度增加对微生物初级生产者和初级生产的限制。为了验证这一点，我们采用同位素标记和分子方法来探索青藏高原湖泊的初级生产和四种主要微生物初级生产者类型（形式 IA、IB、IC 和 ID）。结果表明，DIC 与 IAB 和 ID 型微生物初级生产者和初级生产的丰度呈正相关（所有P< 0.001) 并抵消盐度限制。结构方程模型阐明 DIC 通过刺激形式 ID 微生物初级生产者的丰度显着提高初级生产。与 IAB 型 (6%) 和物理化学因素 (6.8%) 相比，ID 型初级生产者的丰度解释了初级生产的更多变化 (14.6%)。硅藻（形态 ID）通过适应高 DIC 和高盐度，在湖泊初级生产中发挥了决定性作用。我们的研究结果表明，在未来的气候变化情景中，内陆湖泊可能支持更高的初级生产力。