Long-term trends in diatom diversity and palaeoproductivity: a 16 000-year multidecadal record from Lake Baikal, southern Siberia
Long-term trends in diatom diversity and palaeoproductivity: a 16 000-year multidecadal record from Lake Baikal, southern Siberia
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DOI：
10.5194/cp-18-363-2022
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发表时间：
2022-02
影响因子：
4.3
通讯作者：
A. Mackay;V. A. Felde;D. Morley;N. Piotrowska;P. Rioual;A. Seddon;George E. A. Swann
中科院分区：
文献类型：
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作者：
A. Mackay;V. A. Felde;D. Morley;N. Piotrowska;P. Rioual;A. Seddon;George E. A. Swann
摘要。生物多样性与群落稳定性和生态系统功能有着密不可分的联系，但我们对淡水生态系统中这些关系的理解在很大程度上是基于短期观察、实验和建模方法。利用贝加尔湖过去约16000年的硅藻记录，我们研究了在气候快速波动和相对气候稳定时期，硅藻多样性和古生产力是如何响应气候变化的。我们展示了过去16000年硅藻群落的动态变化，物种优势的年代际变化打断了千年尺度的季节趋势。我们首次描述了贝加尔湖硅藻群落从春季到秋季的逐渐转变，这种转变始于新仙女木时期，并在全新世晚期达到顶峰，这可能代表了轨道驱动的生态系统对季节性长期变化的响应。通过多元分类树，我们发现浮游硅藻和微浮游硅藻的趋势广泛地反映了与北半球冰盖消亡相关的长期气候变化和与新仙女木期（例如新仙女木期）相关的突变气候变化。事实上，硅藻群落在大约8.2 cal kyr BP的全新世早期和中期之间的边界之前和之后差异最大，分别与北半球冰盖的存在和消亡有关。利用希尔物种数量估算的硅藻丰富度和多样性也显示出对以气候突变为特征的时期非常敏感，并且利用贝加尔湖硅藻技术的知识，从资源可用性方面解释了多样性趋势。利用硅藻生物体积积累速率（BVARs；µm3 cm−2 yr−1），我们发现春季硅藻作物在我们记录的几乎所有时期都主导着古生产力，除了晚全新世的一个短暂时期外，该时期在1.8-1.4 cal kyr BP之间秋季生产力占主导地位。古生产力在新仙女木时期尤其不稳定，在约12.3 calkyr BP时达到18.3 × 103µm3 cm−2 yr−1的峰值。广义加性模型（GAMs）在预先定义的气候期间探索生产力-多样性关系（pdr），揭示了复杂的关系。在新仙女木期、全新世早期和全新世晚期，即气候快速变化时期，发现了GAMs最有力的统计证据。我们从气候介导的资源可用性和贝加尔湖特有硅藻物种适应这一独特生态系统中极端生活形式的能力方面考虑了这些差异。我们的分析提供了在未来气候变暖的情况下生产力-多样性关系如何发展的见解。
Abstract. Biological diversity is inextricably linked to community stability and ecosystem functioning, but our understanding of these relationships in freshwater ecosystems is largely based on short-term observational, experimental, and modelling approaches. Using a multidecadal diatom record for the past ca. 16 000 years from Lake Baikal, we investigate how diversity and palaeoproductivity have responded to climate change during periods of both rapid climate fluctuation and relative climate stability. We show dynamic changes in diatom communities during the past 16 000 years, with decadal shifts in species dominance punctuating millennial-scale seasonal trends. We describe for the first time in Lake Baikal a gradual shift from spring to autumnal diatom communities that started during the Younger Dryas and peaked during the Late Holocene, which likely represents orbitally driven ecosystem responses to long-term changes in seasonality. Using a multivariate classification tree, we show that trends in planktonic and tychoplanktonic diatoms broadly reflect both long-term climatic changes associated with the demise of Northern Hemisphere ice sheets and abrupt climatic changes associated with, for example, the Younger Dryas stadial. Indeed, diatom communities are most different before and after the boundary between the Early and Middle Holocene periods of ca. 8.2 cal kyr BP, associated with the presence and demise of Northern Hemisphere ice sheets respectively. Diatom richness and diversity, estimated using Hill's species numbers, are also shown to be very responsive to periods characterized by abrupt climate change, and using knowledge of diatom autecologies in Lake Baikal, diversity trends are interpreted in terms of resource availability. Using diatom biovolume accumulation rates (BVARs; µm3 cm−2 yr−1), we show that spring diatom crops dominate palaeoproductivity for nearly all of our record, apart from a short period during the Late Holocene, when autumnal productivity dominated between 1.8–1.4 cal kyr BP. Palaeoproductivity was especially unstable during the Younger Dryas, reaching peak rates of 18.3 × 103 µm3 cm−2 yr−1 at ca. 12.3 cal kyr BP. Generalized additive models (GAMs), which explore productivity–diversity relationships (PDRs) during pre-defined climate periods, reveal complex relationships. The strongest statistical evidence for GAMs were found during the Younger Dryas, the Early Holocene, and the Late Holocene, i.e. periods of rapid climate change. We account for these differences in terms of climate-mediated resource availability, and the ability of endemic diatom species in Lake Baikal to adapt to extreme forms of living in this unique ecosystem. Our analyses offer insight into how productivity–diversity relationships may develop in the future under a warming climate.