Ecological mechanisms regulating the dynamics of the field rotifer population in a subtropical lake: evidence from the density, reproduction, and morphology of a case rotifer, Brachionus angularis

Abstract

Understanding the ecological mechanisms driving the dynamics of field rotifer populations remains a challenge in ecology. Brachionus angularis (Rotifera) is preferred in such studies because of their planktonic behavior, high fecundity, and absence of cryptic species. In this study, one-year zooplankton samples were collected twice a month from a subtropical lake and the roles of abiotic and biotic factors regulating the population dynamics of B. angularis were analyzed. The sampled B. angularis were composed of two discontinuous populations: ‘summer and autumn’ and ‘spring and winter’, segmented by high mixis rates. The ‘summer and autumn’ population had high egg ratios, but low egg volumes. Water temperature was the main factor driving temporal dynamics in density, thereby counteracting the negative effect of top-down force. Based on the synchronous dynamics of two fractions of chlorophyll-a, the densities of B. angularis, its potential competitors and predators, together with the reverse correlations between the egg ratio and population density, and Secchi-disk depth, we found that bottom-up and top-down forces were plausible factors regulating variations in population density in spring (March and April). However, the density peak of B. angularis in winter might be primarily ascribed to recruitment from the sediment. We further addressed the necessity for diverse evidence from the speciation of cryptic species, abundance, reproduction, and morphology, in understanding the population dynamics of a field rotifer population.

Keywords:

• Population dynamics
• Brachionus angularis
• ecological mechanisms
• abiotic and biotic factors
• comprehensive evidence

Acknowledgments

We are grateful to Shenzhen Nobel Science and Technology Service Co., Ltd. for the valuable comments on the manuscript and corrections of the English.

Disclosure statement

No potential conflict of interest was reported by the authors.

Funding

This work was funded by National Natural Science Foundation of China [grant number 41877417], the Anhui Provincial Natural Science Foundation [grant number 1808085MC79], Natural Science Foundation of Educational Committee of Anhui Province [grant number KJ2017A320], and the Foundation of Provincial Key Laboratories for Conservation and Utilization of Important Biological Resources in Anhui.

Notes on contributors

Xin-Li Wen is an associate professor at College of Life Sciences, Anhui Normal University, where he worked for many years as a teacher and ecologist, particularly in zooplankton ecology.

Ying-Hao Xue has got his master degree from College of Life Sciences, Anhui Normal University, and worked for many years at Rural Energy and Environment Agency, Ministry of Agriculture, Beijing, China.

Gen Zhang has got his master degree from College of Life Sciences, Anhui Normal University, and got his Doctor degree from the Hong Kong University of Science and Technology.

Xian-Ling Xiang is a professor at College of Life Sciences, Anhui Normal University, where he worked for many years as a teacher and ecologist, particularly in zooplankton ecology.

Yi-Long Xi is a professor at College of Life Sciences, Anhui Normal University, where he worked for many years as a teacher and ecologist, particularly in zooplankton ecology.