Abstract: Aquatic plants are not only natural bait and molting habitat for the crabs (Eriocheir sinensis), but also play an important role in purifying the water body of Chinese crab ponds. Elodea nuttallii, as the traditional plants in rearing ponds, usually performed poor growth or even death in hot summer, which lead to the deterioration of the crab habitat. Thus, screening candidate plants with high temperature resistance has great significance in ecological crab rearing. In this comparative study in high temperature period, three different aquatic plants, Ipomoea aquatic, Oryza sativa and Elodea nuttallii, were employed to assess their related effects on crab yields, water quality and greenhouse gas emissions for achieving stable yield as well as friendly environment for crab pond. The results show that there was no significant difference of crab yields in the three different treatments. Considering the amount of assimilated nitrogen or phosphorus, the three types of aquatic plants displayed as I. aquatic > E.nuttallii > O. sativa. Compared to E.nuttallii, O. sativa and I. aquatic treatments significantly reduced the water nitrogen concentrations from July to September whereas no significant difference was found for the phosphorus concentrations. Meanwhile, different aquatic plants changed CH₄ and N₂O emission fluxes. The accumulated CH₄ emissions of the O. sativa and I. aquatic treatments were both significantly higher than that of the E.nuttallii treatment, while no significant difference of accumulated N₂O emissions was found forthe three treatments. The E.nuttallii treatment had higher global warming potential (GWP) than the O. sativa and I. aquatic treatments. Considering the decay after grain-filling stage of O. sativa in late August, I. aquatic can be a great alternate of E.nuttallii in hot summer to improve water quality in crab rearing.

Key words: Eriocheir sinensis, high temperature season, water quality purification, greenhouse gas emissions, global warming potential