| Coastal zone is an important ecological transition zone for material,energy and information exchange between land and marine ecosystems.Coastal zone,as the most active natural area on the earth surface and the most advantageous human activity area with the most favorable resource and environmental conditions,has the most close relationship with the survival and development of human beings.The study of it reflects the dynamic mechanism of the interaction between the three systems of land,ocean and human.The monitoring of coastal dynamic geomorphic characteristics can further understand the dynamic geomorphic environment of sandy coast and provide scientific support for the deterioration of sandy beach quality.The study of biodiversity of intertidal benthos contributes to a profound understanding of species composition,distribution and quantity of intertidal benthos and the interaction between intertidal benthos and environmental factors.It can also lay a solid foundation for the development of coastal ecology and provide references for biodiversity conservation in the intertidal zone.This paper takes Rizhao coastal zone as the study area.Based on the analysis of the beach profiles and surface sediment grain-size parameters,and using the wave and tidal data,the K,? and ? parameters were obtained,and analyzed about the present situation of Rizhao sandy beach erosion.In order to reveal the geomorphic characteristics,dynamic environment and sediment distribution characteristics of the north and south sections of the Rizhao coastal zone,and to discuss the dynamic mechanism causing the changes.Three intertidal zones with different sediment types were selected in the study area,and biological samples were taken from the high,middle and low tide zones,respectively.According to the data obtained from the field investigation,the species composition,quantity distribution,dominant species,biomass and abundance,and biodiversity index of the intertidal benthos in different sediments were analyzed,and their temporal and spatial changes were analyzed,thus the investigation and study of the intertidal biodiversity were completed.The results are as follows.Firstly,there are significant differences in the beach profiles of the study area.The beach profiles of Wujiatai and Chenjiazhuang Village show a slightly concave structure in the middle of the beach profiles,while the beach profiles of the middle and lower beaches show a significantly convex structure.The beach sections of Lijiatai and Liujiawan fluctuate slightly.In general,the profile in the study area is mainly flat or convex,and the variation trend is relatively stable.Secondly,according to the variation of particle size parameters,the mean of the beach sediments in the study area is between 0.127 mm and 0.809 mm.The sediment types are mainly medium sand,and coarse sand and fine sand are also distributed.The mean of the sediments generally shows that the high tide area is greater than the middle tide area,and the middle tide area is greater than the low tide area.The sorting of sediments ranges from0.070 to 0.381.Most of the beaches have fewer grain sizes and prominent major grain sizes,which have good sorting ability.The sorting generally shows that the high tide area is larger than the middle tide area,and the middle tide area is roughly equal to the low tide area,indicating that the high tide area has relatively good sorting ability.The variation range of sediment skewness is 0.016 to 0.320,which basically presents the form of positive skewness.The skewness values show that the high tide area,middle tide area and low tide area are roughly equal,and all of them are greater than zero trend,indicating that there are more sand and coarse sand in the sediments of each tidal area.The variation range of the sediment kurtosis is 0.959 to 1.082,the difference is small,and the distribution is relatively concentrated.The kurtosis values are roughly equal in the high tide area,middle tide area and low tide area,and the kurtosis values are all low,indicating that the sediment in each tidal area has not undergone obvious modification in the new environment.Thirdly,from the perspective of dynamic geomorphic parameters,,the K values of typical sandy beaches are all less than 1,which indicates that tidal action is relatively strong,wave action is relatively weak,and the hydrodynamic process is dominated by tidal action.The ? values of the typical sandy beaches in the study area are all greater than 20,which indicates that the beaches in the study area are all dissipative beaches with flat and broad beach surface and good sandy beach quality.The ? value in the study area is relatively low,less than 2,belong to the very obvious reflective beach.Fourthly,the coastline of the study area is relatively straight,including two coastal geomorphology types:barrier-lagoon beach and straightened beach.The beach in Lijiataibeach,Liujiawan beach and Chenjiazhuang Village beach are straightened beach.Wujiatai beach for barrier-lagoon beach.The development of coastal geomorphology in the study area is influenced by the earth's internal and external forces.The main factors controlling the development and evolution of coastal geomorphology are coastal hydrodynamic action,coastal wind action and human activities.Fifthly,a total of 117 species of intertidal benthos were identified in the study area,belonging to 11 phyla,20 classes,54 families,104 genera,including 61 molluscs,28 arthropods,15 annelids and 9 other groups.Molluscs and arthropods accounted for the most species.The dominant species in section A1 are Ocypode cordimand,Umbonium thomasi,and Coenobita rugosus.The dominant species in section A2 are Littorina brevicula,Reishia clavigera,Ruditapes philippinarum and algae.The dominant species at cross section A3 are Meretrix meretrix,Musculus senhousei,Scylla serrata and polychaetes.The dominant population in the study area changed significantly,with arthropods,annelids and mollusks appearing alternately.Sixthly,from the perspective of horizontal changes,the species of intertidal zone in the study area showed a trend that A2 section was larger than A3 section,and A3 section was larger than A1 section.The number of benthos in the intertidal zone in the study area showed a trend that A2 section was larger than A1 section,and A1 section was larger than A3 section.The biomass of section A1 was 4444.32 g/m~2,that of section A2 was 4438.66g/m~2,and that of section A3 was 9848.27 g/m~2,which showed that section A3 was larger than section A1,and section A1 was larger than section A2.The abundance of A1 section is1553.34 ind/m~2,that of A2 section is 2462.66 ind /m~2,and that of A3 section is 1566 ind/m~2,which shows that A2 section is larger than A3 section,and A3 section is larger than A1 section.The abundance of fauna in the intertidal zone at section A2 is much greater than that at section A1 and section A3.The species diversity index of A1 section was 1.184,that of A2 section was 0.878,and that of A3 section was 1.280,indicating that A3 section was larger than A1 section,and A1 section was larger than A2 section.The species evenness index of section A1 was 0.142,that of section A2 was 0.099,and that of section A3 was0.156,showing that section A3 was larger than section A1,and section A1 was larger than section A2.The species richness index of section A1 was 6.342,that of section A2 was8.225,and that of section A3 was 7.432,indicating that section A2 was larger than section A3,and section A3 was larger than section A1.Seventhly,from the perspective of vertical variation,the species distribution characteristics of different tidal areas showed that the high tide area was significantly less than the middle tide area and low tide area.The biomass generally showed a trend that the low tide area was greater than the middle tide area,and the middle tide area was greater than the high tide area.The abundance in the middle tidal area is greater than that in the low tidal area,and the low tidal area is greater than that in the high tidal area.The species diversity index was higher in low tide area than in high tide area.Species evenness index was higher in low tide area than in middle tide area and higher in middle tide area than in high tide area.Species richness index was higher in low tide area than in middle tide area,and higher in middle tide area than high tide area.The characteristics of biodiversity in intertidal zone are formed under the action of medium and long term environmental conditions of corresponding species,which are closely related to temperature,salinity,hydrodynamic,sediment type,biological competition,human activities and other factors. |
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