THE ROLE OF UPPER TROPHIC LEVEL PREDATORS IN MAINTAINING THE PELAGIC AND LITTORAL HABITAT ENERGY COUPLING IN SHALLOW LAKES

Lakes are complex ecosystems composed of distinct subsystems or habitats. The interactions among these habitats and the energy and material flow of the food web have been the focus of ecological research. In lake ecosystems, there are great differences in environmental conditions between pelagic and littoral habitats, but few studies investigated how the food webs of these two habitats related closely to realize the transfer and flow of matter and energy. Predators play an important role in the energy flow and material circulation of food webs between different habitats due to their high mobility and wide range of activities. Culters, a high nutrient consumer of lakes and reservoirs, play an important role in regulating aquatic biological communities. This study analyses the stable isotope (δ¹³C and δ¹⁵N) data of upper trophic level predators (Culter dabryi and Cultrichthys erythropterus) and their food sources from pelagic and littoral habitats in Bao’an Lake. We integrated the food sources of Culter dabryi and Cultrichthys erythropterus according to their feeding habits, forming four types of nutrient sources, zooplankton, zoobenthos, pelagic prey fish, and littoral prey fish for model construction. Differences in food sources between these predators in different habitats are analyzed by the stable isotope mixing model and nonmetric multidimensional scaling (NMDS). Stable isotope mixing model, which can be used to analyze consumer nutrition sources, to determine a variety of food sources contribute to the consumers’ nutrition proportion. Results showed no significant differences in food sources of culters between pelagic and littoral habitats, and the food sources are relatively extensive and include pelagic prey fish, littoral prey fish, zooplankton, and zoobenthos. The results suggested that these culters are in the process of movement and predation, causing the integration of energy and nutrients from the discontinuous food chains in pelagic and littoral habitats, and increasing the degree of habitat coupling. Hence, the two predators play an important role in maintaining the nutrients cycle and food web structure and stability in the Bao’an Lake ecosystem.