Assessing food web health with network topology and stability analysis in aquatic ecosystem

Abstract Degeneration of aquatic ecosystem has become one of the ecological problems facing the whole world. However, due to the uncertainty and complexity, it is difficult to assess the food web health and apply them to ecosystem management. In this research, we established a TIO-IS (Total-input-output-interaction strength analysis) method to assess food web health, combining topology and interspecific interaction. In detail, we selected eight three-species modules containing six types of interspecific interaction and 64 four-species modules to evaluate food-web health (FWH). Furthermore, we used ANOVA (Analysis of Variance) analysis to test correlation between network complexity and interspecific interaction. This work will enhance the traditional methods in terms of (a) constructing a systematic and integrative indicators system to assess food web health; (b) analyzing community stability under different topology structures; (c) coding different types species in aquatic ecosystem. As the results, omnivory and trophic cascade had higher FWH than other interactions. By ranking, we got the health degree of the interaction of these six species respectively: omnivory, trophic cascade, multi-predators, exploitive competition, interguild predator and loop. The occurrence frequency of interaction relationship were respectively 0.88, 0.84, 0.68, 0.52, 0.12, 0. Additionally, about 16% of network structures have been shaping the uniform pattern for each species node. It is concluded that the health food web should be satisfied with three primary conditions: a) there exist multiple component types (i.e. species with multiple trophic levels); b) it is with high probability that there have coexistence with omnivory and trophic cascade relationship for sub-module types (the weak interaction swamping hypothesis); c) it is likely that some nodes shape high connectivity, which lead to the inhomogeneous distribution of connectivity in a web (keystone species hypothesis). This research will improve the development of ecosystem management, provide an indicator to evaluate aquatic ecosystem, and conducive to realize manual design of food web.