Subfossil cladocerans as quantitative indicators of past ecological conditions in Yangtze River Basin lakes, China

The research article “Subfossil cladocerans as quantitative indicators of past ecological conditions in Yangtze River Basin lakes, China”, co-authored by METU visiting researcher Prof. Erik Jeppesen, has been published in Science of the Total Environment.

Cladocerans (Crustacea: Branchiopoda) are an essential component of the food webs of shallow lakes. However, their potential significance as sentinels of environmental change in subtropical regions of South-East Asia, is not well elucidated. In this study, we examined the distribution pattern of cladoceran subfossils in the surface sediments of 64 shallow lakes located in the middle and lower reaches of the Yangtze River Basin (MLYB). Using constrained ordination and multivariate regression trees (MRT), we explored the relationships between the distribution of cladocerans and contemporary environmental variables. The results indicated that macrophyte abundance is the most important regulator, followed by chlorophyll a and total phosphorus that all were important drivers of cladoceran community dynamics. Despite intensive aquaculture in the MLYB lakes over the past decades, fish predation did not have a significant influence on the cladoceran community, likely because the fish predation pressure was generally high. The MRT analysis showed distinct variations in the composition of cladoceran communities and was able to identify the key indicator species of various stressors, including Bosmina coregoni, small Alona (A. intermedia, A. rectangula) and Leydigia acanthocercoides, Leydigia leydigi and Chydorus sphaericus. Boosted Regression Tree (BRT), a novel numerical model, was employed to establish the quantitative relationship between cladoceran composition and environmental variables. The model was used to reconstruct historical macrophyte coverage over the past 60 years in a typical Yangtze lake, Liangzi Lake, based on sedimentary cladoceran records. The BRT-inferred macrophyte coverage was validated well by the macrofossil records in the same lake. Using subfossil cladocerans as indicator of the past environmental change in MLYB lakes is potentially useful given their key ecological roles. However, caution should be taken due to species-specific differences in preservation in the sediment and confounding environmental processes that to some extent may bias the conclusions.

Dong, X., Kattel, G., & Jeppesen, E. (2020). Subfossil cladocerans as quantitative indicators of past ecological conditions in yangtze river basin lakes, china. Science of the Total Environment, 728 doi:10.1016/j.scitotenv.2020.138794

Article access: https://www.sciencedirect.com/science/article/abs/pii/S0048969720323111?via%3Dihub

Keywords:

Boosted regression tree; Cladoceran; Macrophyte; Middle and lower reaches of the Yangtze River; Shallow lakes

Other authors:

Dong, X., & Kattel, G.

Acknowledgments:
We would like to thank Anne Mette Poulsen from Aarhus University for the language editing. This work was supported by the National Natural Science Foundation of China (Nos. # 41772372 and # 41530753 ) and Guangzhou University . EJ was supported by Tübitak , BIDEB 2232, and GK acknowledges the Visiting Professorial Fellowship at Guangzhou University and the National Key Research Program of China Grants (# 2016YFC0402900 ) for their support while working at various institutions in China.