Consumption of an exotic plant (Spartina alterniflora) by the macrobenthic fauna in a mangrove wetland at Zhanjiang, China

Exotic species can affect food webs and cause cascading effects on ecosystem functioning. The exotic cordgrass, Spartina alterniflora, is an increasing threat to mangrove forests in eastern Asia. However, limited knowledge is available about the effects of S. alterniflora on the diet of macrobenthic fauna and food webs in mangrove wetlands. The stable carbon and nitrogen isotopes of primary producers and 11 common native macrobenthic fauna were examined to determine whether exotic S. alterniflora has become a food source for macrobenthic fauna in a mangrove wetland in Zhanjiang, China. The MixSIR mixing model revealed that exotic S. alterniflora served as a new food source for native macrobenthic fauna, and even as the main food source for many macrobenthic fauna. These findings suggest that this invasive plant is now part of the local benthic food web, i.e., it serves as a nutrient source for macrobenthic fauna in local mangrove wetlands. This study provides strong evidence that invasive plants can contribute to the diet of native consumers and change their diet patterns, ultimately altering the materials entering local food webs.