| Seagrass bed supports important ecological function,such as regulating atmosphere,purifying water quality,carbon storage and stabilizing benthic food webs.The complex interactions between seagrasses and benthos are important for understanding the ecological function of seagrass beds.In this paper,the spatiotemporal distribution and environmental impact factors of Thalassia hemprichii and Lucinid were investigated.Through seagrass transplantation the addition of Lucinid and fertilizers,sediment pore water,sediments,microbial community abundance and composition structure,morphological and physiological indicators of T.hemprichii were clarified.The main conclusions are summarized as follows:1.A survey was conducted in January,March,May,July,September,and November 2021 on T.hemprichii and Lucinid in Xincun Bay.The results showed that the effects of pore water nutrients and sulfides on the density of Lucinid were significant.Higher concentrations of nutrients significantly increased the density of Lucinid,while the density of Lucinid was significantly negatively correlated with sulfide concentration.The density of Lucinid was also significantly correlated with the growth of seagrasses.The density of Lucinid in seagrass beds with higher carbon(C)and nitrogen(N)content,larger leaf width was relatively higher than that in areas without seagrass.Due to the higher total organic carbon(TOC)content in the area without seagrasses,the density of the Lucinid was higher than other places.Temperature and salinity had significant impacts on morphological indicators such as leaf width.High temperature and salinity could reduce the C content of seagrass tissues.Nutrients and sulfides had significant impacts on the morphology and physiological indicators of seagrasses.Higher concentrations of nitrogen,phosphorus,and sulfide significantly reduced the seagrass leaf width and C content of seagrass aboveground tissues,while significantly increasing the N and sulfur(S)content of seagrass aboveground tissues.The higher TOC content of sediments significantly increased the C,N,and S contents of seagras aboveground and underground tissues.The density of Lucinid was significantly related to leaf length and width of seagrasses.2.A 6-week seagrass transplantation experiment was conducted in Xincun Bay.By adding Lucinid and fertilizers,seagrasses,environmental parameters and microbial community abundance and composition were monitored,and the synergistic effects of Lucinid and fertilizer on seagrasses were explored.The results showed that the addition of fertilizers significantly increased the nutrient content of pore water.The addition of Lucinid,and Lucinid and fertiliazer additon effectively reduced the sulfide concentration of pore water.The presence of Lucinid significantly reduced the content of dissolved organic carbon and increased the content of mineralizable organic carbon.The addition of fertilizer significantly reduced the leaf length,root diameter,and underground tissue C and N content of seagrasses,while the addition of Lucinid significantly increased the morphological indicators such as leaf width and underground tissue C and N content,therefore significantly reduced underground tissue C/N.Lucinid and fertiliazer additon also had significant positive impacts on rhizome diameter.Compared with the fertilizer treatment,the additon of Lucinid and fertilizer effectively reduced the relative abundance of sulfate educing bacteria(SRB)and sulfur oxidizing bacteria(SOB)in the sediment,and the ratio of sulfur oxidation metabolism was lower.The treatment group with the addition of Lucinid had higher communities of Bacteroidota Firmicutes,Flavobacteriaceae and Actinobacteriota.The addition of fertilizer may inhibite the activity of diazotrophic bacteria,therefore resulting in lower TN in the sediments treated with fertilizer.3.Based on the above-mentioned results,this paper provided suggestions for the protection and restoration of seagrass beds in the future as follows: strengthening the long-term monitor of seagrass bed,applying benthos to evaluate the seagrass ecosystem health,and strengthening the research on the synergistic impact mechanism of global climate change and human activities on the interaction between seagrass and benthos. |
