Introduction
Lake ecosystem is a typical spatial heterogeneous ecosystem formed by the interaction between lake biological community and the lake environment. The dynamic process can be shown by the four-dimensional changes of its biological and environmental elements(Protasov, 2008; Ward, 1989). If a lake is in a state of natural evolution and undisturbed by human beings possess a reasonable structure and perfect function, the lake is in a healthy state (Beck & Hatch, 2009; Cooke, Welch, Peterson, & Nichols, 2016). Because of the increase in human population, the speedy development of industrial production and domestic life, the human demand for water resources has been increasing in the recent decades. The problems such as the over-exploitation of water resources, the pollution of water ecological environment have become increasingly prominent. The structure and function of lake ecosystem had been seriously destroyed, and the health of lake ecosystems is gradually deteriorating (Likens, 2010; Tilzer & Serruya, 2012).
As important groups of lake ecosystems, macroinvertebrates play an important role in lakes, altering the geochemical condition of sediments, promoting nutrient cycling and facilitating the transfer of energy among food webs (Cai, Gong, & Qin, 2012; Odountan, de Bisthoven, Abou, & Eggermont, 2019; Vaughn & Hakenkamp, 2001). Macroinvertebrates are also commonly used as indicators of aquatic ecosystem integrity because of their wide range of sensitivity to pollution and relative longevity (Du et al., 2021; Richman & Somers, 2010; Selvanayagam & Abril, 2016).
The distribution of macroinvertebrate communities in aquatic systems is mainly affected by both natural factors and human activities (Z. Yu et al., 2020). The natural factors mainly include water temperature, water depth, dissolved oxygen, pH and spatial heterogeneity of habitats (Bazzanti, Della Bella, & Grezzi, 2009; Free et al., 2009; Shostell & Williams, 2007). Human activities such as agricultural production indirectly affect the community structure of macroinvertebrates by altering the nutrient level of within-lake water bodies (Wijesiri, Deilami, & Goonetilleke, 2018).
Previous studies have showed that there is a strong correlation between macroinvertebrate community and environmental factors especially in streams and rivers (Kłonowska-Olejnik & Skalski, 2014; S. Li et al., 2018; Zhang, Yang, Wan, Wang, & Wang, 2021). However, little is known about macroinvertebrate assemblages and the environmental factors regulating their dynamics in lakes (Jiang et al., 2020; Song et al., 2007; White & Irvine, 2003). Thus, analyzing the response relationship between macroinvertebrates and environmental factors has important guiding significance for improving lake ecological environment.
Lianhuan Lake which is located in Heilongjiang Province, is the largest alkaline lake in northern China. Lianhuan Lake was formed by tectonic slump and it consists of 18 small lakes around (Wen-hua, 2012). As an important lake in northern China, Lianhuan Lake plays an important role in climate regulation, replenishing groundwater, supporting biodiversity habitat and economic resource development (Lianjiang & Shulan, 2011; Ma et al., 2018). However, in the recent years, with the agricultural reclaimed area in the lake catchment and tourism activities within the lake, the biodiversity loss and degradation of habitat and other problems have been more seriously (Jing, Shuying, Yanshan, Haifeng, & Deqing, 2009; Sun, Zang, Xiao, & Sun, 2010). At present, most of the studies which have been conducted in Lianhuan Lake are about assessment of heavy metals and nutrient elements in core sediments (Haifeng et al., 2010; Sun et al., 2010).
In this study, the community composition of macroinvertebrate assemblages and their relationships with environmental variables in 13 small lakes within Linhuan Lake was investigated. The 13 small lakes were chosen because they belong to the same watershed but differ in natural condition (e.g., lake morphology and environmental characteristics) which could result in different relationships between macroinvertebrate assemblages and environment factors. The aims of the study were as follows: (a) To determine the spatial and temporal patterns of the macroinvertebrate communities and the community groups, (b) To identify the indicator taxa’s characterizing of each community group, and (c) To determine the important environmental variables shaping the community structure of macroinvertebrates in Lianhuan Lake. We expected that within-lake environmental variables would explain substantial amounts of variation in macroinvertebrates, so as to provide a scientific basis for protecting the health and biodiversity of the ecosystem in Lianhuan Lake.