A Preliminary Study On Bioremediation Effect Of Tidal Flats Habitat By Perinereis Aibuhitensis

Different densities of perinereis aibuhitensis (both1#and2#were divided into six plots,denoted as A, B, C, D, E, F. A was control group, not sowing perinereis aibuhitensis. Nereisdensity gradually decreased, the density ratio of B, C, D, E, F was1:1/2:1/3:1/4:1/5) werereleased onto the sediment of the tidal flats of1#section (Tegillarca granosa test area) and2#section (Sinonovacula constricta test area) in ecological restoration demonstration area of Xipivillage, Xiwei town of Fuan city. Ecological risk of Fuan Sea was evaluated by using the singlefactor pollution index, Nemerow pollution index and potential ecological risk index. Thephysical and chemical factors(total nitrogen, total phosphorus, organic carbon, sulfur oxide,oxidation reduction potential)，as well as biological index(abundance of nematodes, the ratio ofnematodes and copepod abundance, and the ratio of epistrate nematodes and copepodsabundance, community structure) were monitored to assess bioremediation effect of tidal flatshabitat by perinereis aibuhitensis. The results were as follows:1. Heavy metals pollution and potential ecological risk evaluation of sediment samplescollected from Fuan SeaThe average contents of heavy metals (Hg, As, Cu, Pb, Cd, Cr) in sediment was0.115mg/kg,8.25mg/kg,12.38mg/kg,54.7mg/kg,0.118mg/kg,58.4mg/kg, respectively. Except for thecontent of As, significant correlationships existed between all the contents of the heavymetals(P<0.05), the single factor indexs of heavy metals was sorted in the order of Cd (0.237)<Cu (0.413)<As (0.550)<Hg (0.577)<Cr (0.973)<Pb (2.187), The contents of Hg, As, Cu, Cd,Cr were at the low-polluted level, while the content of Pb was at the moderate polluted level. Theaverage value of heavy metal’s Nemerow pollution index was1.653, belonging to the middlepollution levels. Ecological risk index (RI) was50.62, belonging to low potential ecological riskareas.2. The effect of different densities of perinereis aibuhitensis on some physical and chemicalfactors(1) There was no significant difference between the different groups of1#section, as wellas2#section(P>0.05). Compared with the control group1#A, total nitrogen content inexperimental groups of1#B,1#C,1#D,1#E,1#F decreased by19.17%,16.43%,13.69%,26.70%,21.91%, respectively,1#E showed the largest decrease. Compared with the controlgroup2#A, total nitrogen content of2#B,2#C,2#D,2#E,2#F increased by35.71%,43.45%, 26.19%,20.23%,32.14%, respectively,2#E showed the least accumulation of total nitrogencontent;(2) There was no significant difference between the different groups of1#section, aswell as2#(P>0.05). Compared with the control group1#A, total phosphorus content ofexperimental group1#B,1#C,1#D,1#E,1#F decreased by6.61%,5.44%,5.63%,2.33%,7.19%,respectively,1#F showed the sharpest decline. Compared with the control group2#A, totalphosphorus content of2#B,2#C increased by3.40%,0.68%, total phosphorus content of2#D,2#E and2#F decreased by4.53%,0.45%,4.99%,2#F showed the least accumulation of totalphosphorus content;(3) There existed significant difference among1#(P<0.05), compared with1#A, the organic carbon content of1#B,1#C increased by2.86%,3.40%, the organic carboncontent of1#D,1#E,1#F decreased by2.14%,7.87%,10.55%,1#F showed the biggest drop.There was no significant difference between the different groups of2#section(P>0.05).Compared with the control group2#A, the organic carbon content of2#B,2#C,2#D,2#Fincreased4.24%,1.94%,0.18%,2.12%, respectively, the organic carbon content of2#Edecreased by1.77%;(4) There was no significant difference between the different groups of1#section, as well as2#section(P>0.05). Compared with the control group1#A, sulfur content of1#E increased0.84%, the sulfur content of1#B,1#C,1#D,1#F decreased by8.80%,6.20%,5.63%,3.79%, respectively,1#B showed the biggest drop. Compared with the control group2#A,the sulphide content of2#B,2#C,2#D,2#E increased by9.25%,0.14%,45.70%,12.23%,respectively, sulphide content of2#F dropped11.92%;(5) There was no significant differencebetween the different groups of1#section, as well as2#section(P>0.05). Compared with thecontrol group1#A, the oxidation reduction potential of1#C increased2.70%, the oxidationreduction potential of1#B,1#D,1#E,1#F decreased26.18%,13.59%,1.74%,10.84%,respectively,1#B showed the largest decrease; Compared with the control group2#A, theoxidation reduction potential of2#B,2#C increased by1.84%,0.83%, respectively,2#D,2#E,2#F decreased by1.86%,2.29%,1.66%,2#E showed the largest decrease.3. The effect of different densities of perinereis aibuhitensis on nematode abundanceThere were no significant differences of nematode abundance between the different plots ofsction1#. The experimental group of2#D on nematode abundance showed significant increasecompared with2#A (P<0.05), the rest of the experiment groups did not exist siginificantdifference compared with2#A (P>0.05); As to the ratio of nematodes to copepods abundance,the ratio in1#E is lower than50, and there was significant difference between1#E and thecontrol group of1#A (P<0.05), the rest of the experimental group and the control group of1#Adid not exist significant differences (P>0.05). No significant differences existed between anyexperimental group in section2#and the control group of2#A; As to the ratio of epistrate nematode abundance to abundance of copepods, there were no significant differences amonggroups of1#and2#(P>0.05).4. The effect of different densities of perinereis aibuhitensis on nematode communitystructure(1) Twenty-nine genera of nematode appeared in1#section, dominant genera were asfollows: Terschellingia, Sabatieria, Daptonema, Parodontophora, Theristus, accounting for24.38%,18.23%,17.08%,10.56%,8.93%, respectively, and79.18%in total. Within1#section,the most dominant nematode genus in the experimental group1#D (Sabatieria),1#E(Daptonema) were inconsistent with the control group1#A (Terschellingia). There were20genera of nematode in2#section, dominant genera were as follows, Parodontophora,Daptonema, Terschellingia, Sabatieria, Theristus, accounting for26.93%,21.09%,18.81%,18.61%,5.54%, respectively, and90.98%in total. Within2#section, the most dominantnematode genus in the experimental group2#D (Sabatiera and Terschellingia),2#E(Terschellingia),2#F (Daptonema) were inconsistent with the control group2#A(Parodontophora);(2) As to nematodes feeding types, the overall trend was1B>2B>1A>2A,1A, selective deposit feeder of nematode was dominant in1#C group, and the other groups aremainly1B, non-selective deposit feeders. Nematode feeding type trends in2#in October was1B>2B>1A>2A,1B was the dominant feeding type among the experimental group and thecontrol group, but different dominance;(3) Except for1#C group, the diversity index H’ ofthe other groups increased in different degrees compared with the control group1#A, of which1#D and1#E groups have higher diversity index. The value of diversity index of2#E increasedcompared with the control group2#A, the value of diversity index H’ in the other groups in2#section declined compared with the2#A.