DNA Bacording And Spatial Distribution Of Invertebrates Resting Eggs In Coastal Zones Of South China Sea

Resting eggs of invertebrates can survive for decades or longer in sediments.They constitute an evolutionary and ecological reservoir impacting the rate and direction of population and community responses to change of environmental conditions.This research was conducted to explore species composition and community structure of invertebrates resting eggs in coastal shallow sea areas of the South China Sea,Daya Bay of typical bay and terrestrial fresh waters of the South China Sea,while previous studies had focused on temperate regions.Problems of time and labor and low success rate of the resting eggs identification had solved by single-egg DNA barcoding.The study included the dynamics of resting egg banks in tropical and subtropical waters and the spatial distribution pattern model of resting eggs community structure under different spatial scales and different habitat types,and further explored the driving factors under different distribution patterns.The influence of latitude variation on the community structure of invertebrates resting eggs was studied on a large scale by taking the coastal shallow waters of the South China Sea as a representative.A total of 79 species were identified by individual resting egg DNA barcoding,including 8 species of rotifers,19 species of copepods,12species of cladocerans and 40 species of others.Surface sediments were separated by sugar suspension method showed eggs densities ranged between 0.15 ind g^-11 to 5.88 ind g^-1 and species richness ranged between 6 to 30,the tendency in abundance and species richness had inapparent relationship with latitude.Chla and water temperature were the main factors driving the difference of resting egg community structure.The community structure of the coastal shallow water sample was more similar in the same city while there is a difference among different cities.The influence of anthropogenic disturbance on the community structure of invertebrates resting eggs was studied on a samll scale by taking the Daya Bay as a representative.A total of 25 species were identified by individual resting egg DNA barcoding,including 8 species of rotifers,7 species of copepods,5 species of cladocerans and 5 species of others.Eggs densities in Daya Bay ranged between 0.27ind g^-1 to 4.18 ind g^-1,and the declined tendency in number of resting eggs and dominant species from outer bay to inner bay.Resting eggs and viable resting eggs were found down to 60 cm and 40 cm respectively,and the greatest number of resting eggs occurred in the 4-5cm in cores,below this,the number of resting eggs declined sharply.The maximum age of resting eggs was 92.3 year and calculated by sediment rate.The annual egg survival was 94.56%,calculated by regressing ln?egg abundance?on the age of the sediment.The differences in the resting eggs community structure between ponds and rivers and the environmental factors which driving the differences were investigated on the large and small scale by taking terrestrial fresh waters of the South China Sea as a representative.A total of 217 species were identified by individual resting egg DNA barcoding,including 64 species of rotifers,10 species of copepods,50 species of cladocerans and 93 species of others.Rotifers had an absolute advantage in abundance and species richness.The abundances of ponds and rivers in the coastal cities of the South China Sea are 0.02-18.70 ind.g^-11 and 0.07-3.90 ind g^-1 respectively,abundance of ponds is much higher than that of rivers.The average abundance had inapparent relationship with latitude on a large scale,and the community structure of resting eggs in the two habitats is different and subject to driven by different environmental factors on a small scale.Salinity and rainfall,pH of sediment had a great effect on the community structure of resting eggs in ponds and rivers respectively,and both habitats affected by temperature.The study provides evidence for the presence of invertebrates resting eggs in tropical and subtropical waters,and reveals the effects of latitude changes,human activities,and environmental factors on community structure,while anthropogenic disturbance can potentially interfere with resting egg banks,active individuals,and even the entire aquatic ecosystem.The factors driving the difference of community structure were diverse in different spatial scales,and the community structure of resting eggs was also diverse in different habitats.Egg banks can be used not only as a preventive mechanism for biodiversity reduction,but also as a response to environmental changes.The link between community structure of resting eggs and environmental factors can be used to predict environmental changes.It is worth mentioning that single-egg DNA barcoding had greatly improved the accuracy and efficiency of the research,and solved the limitations,time-consuming and laborious problems of hatching method based on morphology identification.The structure and characteristics of egg banks have potential and important influence on structure and dynamics of communities.The study on invertebrates resting eggs in the coastal zone of the South China Sea not only complemented the deficiency of dormant egg research,it also provided valuable information and new research ideas for the study of aquatic system ecology.