Seasonal Variation Affects Aquatic Macrophyte Litter Decomposition and Invertebrate Colonization in a Subtropical Eutrophic Shallow lake, China

In eutrophic lakes, the decomposition of aquatic macrophytes is a fundamental process driven by aquatic microbes and invertebrates. We examined how seasonal variation and plant community vegetation type affect litter decomposition and the associated invertebrate colonization by immersing litter bags of Trapa natans and Typha orientalis species under conspecific vegetation as well as under other species vegetation in autumn and summer in a eutrophic lake located in China for 50 days. A significant effect of seasonality on litter decay was observed under T. natans vegetation, with T. natans litter exhibiting the highest decomposition rate in summer under its own vegetation (0.104 day- 1). No home-field advantage (HFA, litter decomposes faster at home than away habitat) was observed in either season.Invertebrate biomass and microbial respiration were also found to be higher during summer under T. natans vegetation. The invertebrate assemblage composition shifted between seasons and vegetations, with most being collectors Chironomidae that may utilize litter material as a substrate or indirect food source. Conversely, the presence of scrapers Gastropoda had a noticeable impact on litter decomposition, particularly in the warmer season, indicating that scrapers can directly contribute to litter mass loss in eutrophic lakes. Our results provide evidence to suggest that aquatic macrophyte litter decomposition in eutrophic lakes is dependent upon litter type, vegetation type, seasonal variation and their interactions. Our research can help us better understand the characteristics of aquatic plant decomposition in eutrophic lakes as well as provide scientific support for the management and preservation strategies for lake ecosystems.