Correlation Between Nematode Population And Micro-animal Community Structure In Urban Sludge Food Web(chain)

The technology of urban sewage treatment tends to mature,and certain achievements have been made in sewage treatment,and the effect has been greatly improved.After treatment of urban sewage,many sludges will be produced.Micro-animals are important biological groups in the sludge,which constitute a complex food web system in the sludge.The interaction between various functional groups completes the sludge degradation.The nematodes in urban sludge have complex feeding habits,occupying different consumption levels in the urban sludge food web,and have predation and competition relationships with other micro-animals.In this paper,through biological observation,the species diversity and community dynamics of nematodes during the natural degradation of urban sludge were studied at 20?.The nematodes were classified and cultured at different stages of degradation,and the proliferation behavior of nematode populations in different organic matter environments was studied.At the same time,through the observation of the biological phase,the dynamic changes of the micro-animal community during the degradation process were clarified,and the relationship between nematodes and micro-animals was analyzed.Combining physical and chemical indicators such as electrical conductivity?EC?,organic matter?OM?,water-soluble organic carbon?SWC?,pH,total nitrogen?TN?,ammonia nitrogen?NH4⁺-N?,and nitrate nitrogen?NO3^--N?,it is possible to study the influence of nematodes and micro-animals on the degradation of organic matter during mud degradation.Through the above research,on the one hand,it can lay the foundation for the study of biodiversity and the correlation between biology and environment in the treatment and disposal of urban sludge;on the other hand,it also provides basic data for the study on the proliferation behavior of nematodes in different organic matter content environments..The main conclusions reached are as follows:?1?The overall number of nematodes is increasing during the experiment of sludge organic matter degradation.At the end,the nematode density was 44 times that of the initial sludge,so it can be said that the nematodes proliferated in the sludge.In the early stage of degradation,the number of nematodes increased rapidly,and in the middle and late stages began to show volatile growth.Two peaks of nematode numbers appeared at 20d and 35d,respectively.Bacterial nematodes dominated at 20d,accounting for 70%,and at 35d,bacterial and fungal nematodes each accounted for 40%,and omnivorous nematodes accounted for a small proportion.According to the nematode community structure analysis,the bacterial-feeding nematodes dominated at the beginning of the experiment.At the end of the experiment,the numbers of bacterial-feeding and fungal-feeding nematodes were similar,and they were 2.85times that of omnivorous nematodes.During the experiment,the bacteria-feeding nematode reached the peak of proliferation at the earliest?20 d?,and the peak numbers were 1.5 and 5times that of the fungus-feeding nematode?40 d?and omnivorous nematode?35 d?,respectively.?2?The number of nematodes separated from the initial sludge,the sludge that degraded for 20 days,and the sludge that lasted for 35 days increased in order,and the trophic group of nematodes changed from a single bacterial-feeding nematode to a coexistence of three types of nematodes.Cultivate nematodes in sludge culture media with different organic matter contents,it was found that with relatively rich organic matter contents?41%and 38%?,the number of nematodes would increase with time,and when the organic matter contents were relatively low?35%?,the number of nematodes decreases.With the decrease of organic matter content,the proliferation ability of bacterial-feeding nematodes weakened,the proliferation ability of fungus-feeding nematodes was enhanced,and the proliferation ability of omnivorous nematodes was the strongest in the case of medium organic matter content.?3?The frequency distribution of micro-animals in the urban sludge food web is as follows:tcstatc amocbac,bacterial-feeding nematodes>omnivorous nematodes>fungus-feeding nematodes>rotifers>scssilc ciliates.The degree distribution of abundance is as follows:scssilc ciliates>bacterial-feeding nematodes>tcstatc amocbac>fungus-feeding nematodes>omnivorous nematodes>rotifers.The abundance of scssilc ciliates is 10 times that of other micro-animals.The frequency of scssilc ciliates is the smallest,while the abundance is the largest,indicating that they are abundant in a short period of time and are the dominant species for the degradation of organic matter in sludge for a certain period of time.The abundance and frequency of bacterial-feeding nematodes are high,and the maximum and minimum values are higher than those of the other two types of nematodes,which are relatively dominant populations.?4?There are three types of micro-animals structure changes during sludge degradation.The growing type is represented by tcstatc amocbac,the decreasing type is represented by scssilc ciliates and rotifers,and the first increasing and then decreasing types are represented by bacterial-feeding nematodes,fungi-feeding nematodes and omnivorous nematodes.According to the correlation analysis,there may be a symbiotic relationship between the fungus-feeding nematodes and tcstatc amocbac.The omnivorous nematodes and scssilc ciliates are both competitive and predatory.Bacterial-feeding nematodes,fungus-feeding nematodes,and scssilc ciliates also compete,and the competition strength is:bacterial-feeding nematodes>omnivorous nematodes>fungus-feeding nematodes.There is a certain competitive relationship between rotifers and nematodes.However,due to the different predatory abilities of each micro-animal,the competitive relationship is strong.The strength of the competitive relationship is fungus-feeding nematodes>omnivorous nematodes>bacterial-feeding nematodes.?5?Correlation changes between sludge physical and chemical indicators and micro-animals can be divided into three categories.The correlations between OM,SWC,TN and micro-animals are consistent,and the correlations between EC,pH and NO3^--N are consistent with those of micro-animals.The correlation between NH4⁺-N and micro-animals is unique.Fungus-feeding nematodes,omnivorous nematodes,and tcstatc amocbac were significantly negatively correlated with OM and SWC,respectively,and were significantly positively correlated with EC.With the decrease of OM and SWC,the number of fungus-feeding nematodes,omnivorous nematodes and tcstatc amocbac was increased sharply,and the contribution to the mineralization of sludge organic matter was greater.And in the early stage?before 25d?of sludge degradation,their utilization of OM and SWC was stronger than in the later stage.However,the contribution of bacterial-feeding nematodes is small,and the contribution of rotifers and scssilc ciliates is weak.NH₄⁺-N was very significantly positively correlated with omnivorous nematodes,and significantly positively correlated with bacterial-feeding nematodes.Due to the predation of omnivorous nematodes on bacterial-feeding nematodes,the effect of bacterial-feeding nematodes on nitrogen mineralization was weakened.Fungus-feeding nematodes and tcstatc amocbac have little effect on nitrogen mineralization.NO₃^--N has a very significant negative correlation with rotifers,a very significant positive correlation with tcstatc amocbac,fungal-feeding nematodes,and a significant positive correlation with omnivorous nematodes.