Influence Of Shrimp Pond Effluent On The Functional Traits Of Kandelia Obovata And Functional Diversity Of Mangrove Community

In recent years,the scale of shrimp ponds has increased and the pollution has become more severe.The discharge of shrimp pond effluent may lead to changes in plant functional traits and functional diversity,thereby affecting the stability and sustainable development of the entire ecosystem.But there are few studies on the response of mangrove functional traits and functional diversity to shrimp pond effluent discharge.We sampled the roots,stems and leaves of Kandelia obovata and other mangrove plants from polluted and control areas,and compared 20 plant functional traits such as plant height,specific leaf area,and 6 functional diversity indices such as functional attribute diversity(FAD2),functional richness index(FRic),functional dispersion index(FDis),Rao’s quadratic entropy index(FDQ),to explore the effect of shrimp pond effluent on individual plants and communities.The effects of shrimp pond effluent on the functional diversity of mangrove community were compared by multi-dimensional analysis and thereby to reveal the adaptation strategies of mangrove plants to shrimp pond effluent discharges.The main findings of this study are as follows:1.The discharge of shrimp pond effluent has a significant effect on the nutrient content of sediment and pore water in mangrove.The environmental factors such as sediment electrical conductivity,sediment salinity,sediment pH,element content and nutrient concentration of sediment and pore water were affected by shrimp pond effluent significantly.Nitrogen input had the most important effect on the functional diversity of community.2.The discharge of effluent from shrimp ponds improves the nutrient-poor conditions in the habitat,mangrove plants absorb nutrients from the effluent to promote their metabolism and growth,and improved the functional traits of roots,stems and leaves.But at the same time,the discharge of effluent also had some influence on the plant,and the plant showed some defense reaction.Most of the leaf and root functional traits of Kandelia obovata were significantly different in the control area and polluted area,but the stem functional traits were not significantly different in the two environments.3.The plasticity of carbon content of stem and root,pH of leaf and root were small,which may be the inertia traits of environmental disturbance,the plasticity of diameter at breast height and canopy thickness is bigger,the relative change of plasticity of specific leaf area and dry matter content is bigger,are the sensitive traits in response to pollution.Different organs of plants may adopt different ways of nutrient absorption and growth strategies,or they may adopt a consistent way of resisting stress.4.The mangrove plants in the control area showed low disturbance.The plants could deal with the environment by maintaining the nutrient balance in the body,and they preferred the "stress-disturbance" strategy between the S strategy and the R strategy.The mangrove plants in the polluted area absorb a lot of nutrients and resources for their growth,and they tend to be competitive-disturbance type.Therefore,the disturbance of effluent may cause the mangrove plants to change from S-R to C-R,shift to the strategy of "long-term survival" and "fast-growing".5.The discharge of shrimp pond effluent reduces the species dominance and the interspecific difference,the environmental promotion is more important than the interspecific resource competition.The disturbance of shrimp pond effluent increased the convergence of traits,and the community as a whole changed from functional differentiation to functional convergence.The function richness index FRic,function dispersion index FDis and Rao’s quadratic entropy index FDQ in the polluted area were significantly lower than those in the control area.6.There are strong correlations between functional diversity indices,there is no significant correlation between plant species diversity and functional diversity,and functional diversity can indicate and predict ecosystem function and stability better than species diversity.Mangrove ecosystems have lower species richness and higher functional diversity than other ecosystems,and their net primary productivity and carbon density are higher than other ecosystems,resulting in significant carbon sink benefits,the role in the global carbon cycle cannot be ignored.