Testate amoebae as indicators of 20th century environmental change in Lake Zhangdu, China

Abstract

We investigated the response of lacustrine testate amoeba communities to 20 th century environmental changes in Lake Zhangdu, China. The lake and surrounding region have undergone dramatic changes in the past century, including the expansion of agricultural and industrial activities, and associated hydrological modifications that led to the isolation of the lake from Yangtze River. We assessed the potential effects of these activities on testate amoeba communities of the lake by examining subfossil assemblages in contiguous samples along a 35-cm long, 210 Pb dated sediment core. A total of 25 testate amoeba taxa belonging to 4 genera (Difflugia, Centropyxis, Neztelia, and Pentagonia) were encountered in the core. The largest change in the composition of testate amoeba communities occurred in the 1960s, coincident with the expansion of human activities in the watershed. Testate amoeba communities shifted from species characteristic of relatively oligotrophic lakes (e.g. Difflugia biwae, D. tuberspinifera and D. pristis) to species more common to mesotrophic and eutrophic systems (e.g. Difflugia oblonga, D. corona, D. smilion and D. lanceolata). Our results provide valuable baseline data on testate amoebae and water conditions before and after major 20 th century human impact on the lake ecosystem. Lake Zhangdu was recently reconnected with the Yangtze River as part of ongoing conservation efforts, and future monitoring of testate amoeba communities could be used to inform management and assess restoration success.