Gao, X.; Wang, M.; Wu, H.; Wang, W., and Tu, Z., 2018. Effects of Spartina alterniflora invasion on the diet of mangrove crabs (Parasesarma plicata) in the Zhangjiang Estuary, China.

Spartina alterniflora , an exotic invasive plant, has become the most serious threat colonizing mangrove areas in China in the past two decades. The diets of a dominant mangrove crab, Parasesarma plicata, in two mangrove habitats (Kandelia obovata forest and Avicennia marina forest) and adjacent S. alterniflora marsh in a subtropical mangrove estuary in Fujian, China, were investigated using stable isotopes, while a feeding experiment was carried out. The results showed that in the Avicennia forest, Parasesarma was herbivorous, feeding mainly on macroalgae. In the Kandelia forest, the contribution of mangrove leaves, macroalgae, and sediment to the diet of Parasesarma were about 75.5%, 24.2%, and 0.2%, respectively. While Parasesarma had a higher δ¹³C value and also a higher δ¹⁵N value in the Spartina marshes relative to the two mangrove habitats, suggesting that they were feeding on Spartina detritus as well as some small invertebrates. The feeding experiment showed that the δ¹³C value of Parasesarma after 90-day feeding only on Spartina leaves was very close to the δ¹³C value of the crab caught from the Spartina marshes, indicating that Spartina was the main carbon source. These results demonstrated that the invasion of Spartina has changed the main food resources of native crabs by providing food resources, which could affect the impact of crabs as ecological engineers and eventually affect the integrity and function of native ecosystems.