Effects Of Ecological Restoration Project On Morphology And Genetic Diversity Of Sinocalanus Tenellus In Chongming Dongtan National Nature Reserve

With the rapid growth of global population and the development of industrialization,more and more coastal wetlands have been used for industrial and agricultural construction.As a result,the extensive construction of coastal seawalls has sharply decreased the biodiversity of coastal wetlands and related ecosystem services,and threatened the regional ecological security and sustainable development.Chongming Dongtan Bird Nature Reserve began to carry out the“Spartina alterniflora ecological control and bird habitat optimization project”since 2013.The construction of coastal seawalls isolated the external natural tidal seawater from the internal restoration area.At the same time,due to different habitat needs,the interior of the tide-restricted area is separated from each other,and water exchanges are mainly carried out through small sluices,resulting in increasingly fragmented habitats and increasing environmental differences.In this study,the dominant copepod species（Sinocalanus tenellus）in Chongming Dongtan Wetland was selected to explore how natural populations respond to habitat changes,mainly from two aspects of morphological responses and genetic information changes.The main contents are as follows:In this study,field environmental data and zooplankton samples were collected five times to explore the environmental trends within the tide-restricted area and in natural tidal marshland and the morphological differences of natural populations between different habitats.In addition,in order to explain the possible causes of morphological changes,this study further explored the environmental factors related to morphological changes.Environmental parameters show that there are significant differences in the environment among the 16 sampling areas（15 tide-restricted salt marshes and one natural intertidal creeks）,mainly in salinity and p H.The salinity in the north-south region shows a trend of high in the north and low in the south,meanwhile the natural intertidal creeks also have relatively high salinity.Ten morphological indexes of S.tenellus population showed that there were significant differences in nine morphological indexes,which meant that the morphology in the middle of the tide-restricted salt marshes and natural intertidal creeks was larger than that in the south and north of the tide-restricted salt marshes.Through the generalized additive model（GAM）analysis,it was found that six morphological parameters had significant differences,namely,Cephalothorax Width（CW）,Genital segment Length（GL）,Genital segment Min.width（GMINW）,Furca External spine（FEX）,Genital segment Max.width（GMAXW）and Furca Length（FL）.Salinity and p H indicated as physical and chemical factors,and ammonia nitrogen（NH₄-N）and total nitrogen（TN）regarded as utritional parameters are important factors affecting the morphological differences of different populations.This research is important for exploring the morphological responses of zooplankton to environmental changes.This study provides new ideas for species morphological responses at the microgeographic scale,and also inspires us to further consider whether zooplankton responses to environmental changes may occur at the genetic level.Therefore,this study plans to study the genetic structure and genetic diversity of S.tenellus population.In this study,high-throughput sequencing technology was used to develop the microsatellite loci of copepod species S.tenellus for the first time.A total of 12microsatellite loci with high polymorphism were selected,all of which were highly polymorphic loci（PIC>0.5）.Based on the above significant morphological variation results,four sampling areas with the largest environmental differences were selected from 16 microgeographic habitats（one natural tidal creek S10 and three restoration areas,southern C2W,central B1 and northern A3）,and the genetic diversity and genetic structure of S.tenellus population in the four areas were analyzed.It was found that the genetic diversity was similar among the four populations,and the genetic diversity was at a high level,indicating that the four regions may have a large population size and stable population dynamics.Gene flow（Nm）between each population showed that the four populations of S.tenellus had strong gene exchange,and the gene flow index was close to 1.Genetic cluster showed that there was no differentiation of genetic structure among the four populations,which further indicated that the four populations shared same gene pool.In conclusion,this study found that natural populations can respond to environmental changes,especially in terms of morphology.However,there is no reliable evidence that the genetic structure of natural populations also has corresponding changes,which needs to be confirmed by more long-term observation and more studies.This study provides a scientific basis for the impact of ecological restoration project of Chongming Dongtan wetland on biological ecology and evolution.Meanwhile,the results of this study also show that the hydrological exchange among the restoration areas of Chongming Dongtan wetland maintains a high genetic diversity among different habitats,and also proves that hydrological regulation is an effective control method for ecological restoration.Therefore,hydrological regulation can be strengthened to promote water exchange and biological connections between different regions.This study can also provide some scientific evidence for the biological response brought by the seawall construction in Chongming Dongtan wetland.Since zooplankton plays an important role in the food chain,similar studies can be conducted on other taxonomic groups,such as fish and benthic organisms,in order to explore the response direction and degree of multiple groups to the same impact factor（seawall construction）,so as to draw a more objective conclusion.