The Benthic Macro-Invertebrates And Dominant Groups Idenfication In The Yangtze Estuary

Zoobenthic community is an important part of the estuarine ecosystem, which plays a key role in ecosystem structure and function. The study is focused on the ecological study for the dominant benthic macro-invertebrates in Yangtze Estuary by the intensive on-site investigation. In order to meet the requests from different researches, the definition of the dominant species of the benthic macro-invertebrate in Yangtze Estuary is expended. The efforts include dividing the dominant species into different types, consolidating the species of different types, and describing their ecological characteristics. The results are expected to be as an improtant reference in the wise use of the benthic macro-invertebrates at the estuary.Major results of this study are:1. A list of species of benthic macro-invertebrates in Yangtze Estuary is achieved, which includes 5 phylums, 8 classes, 22 orders, 71 families, 101 genuses and 126 species. Four species used to be identified error are corrected. More than 30 species are the first reported as new records in Yangtze Estuary. Such a list is based to calculate the hierarchical diversity.2. In order to meet the demands from different researches, the definition of the dominant species of the benthic macro-invertebrate in Yangtze Estuary is expended. Thus, the whole group of dominant species is divided into into 3 types, consolidating the species of different types and studying their ecological characteristics.a. Dominant group I. It always has the highest density in whole Yangtze Estuary, thus they are dominant at the whole estuary. The group is used to conduct the resource study of the benthic macro-invertebrate in Yangtze Estuary. Details of this group are listed as belowed.There are 8 species of this group in the intertidal zone, which are: Eohaustorius cheliferus, Assiminea sp., Ilyoplax deschampsi, Corbicula fluminea, Assiminea violacea, Chinomantes dehaani, Stenothyra glabra, Assiminea latericea. 9 species in the subtidal zone, which are: Exopalaemon annandalei, Palaemon gravieri, Exopalaemon modestus, Corbicula fluminea, Neoeriocheir leptognatha, Potamocorbula amurensis, Cleantioides annandalei, Exopalaemon carinicauda, Macrobrachium nipponense.By the comparison analysis, the conclusion is drawn as that the intertidal zone are more important than subtidal zone for dominant species I as the habitat.b. Dominant group II. It contains the species dominanting the local communities. This group is used to study the community of benthic macro-invertebrate in Yangtze Estuary.The species in the subtidal zone are: Cleantioides annandalei — Corbicula fluminea, Exopalaemon annandalei - Corbicula fluminea, Neoeriocheir leptognathus+ Palaemon gravieri, Exopalaemon annandalei+ Palaemon gravieri, Nassarius variciferus, Neoeriocheir leptognathus+ Exopalaemon annandalei, Nassarius succinctus — Siliqua minima. The species in the intertidal zone are: Corbicula fluminea →Ilyoplax deschampsi → 0, Corbicula fluminea → Ilyoplax deschampsi →Chinomantes dehaan, Corbicula fluminea→Ilyoplax deschampsi + Assiminea sp. →Chinomantes dehaani, Moerella iridescens → Assiminea sp. → Cerithidea largillierl, Eohaustorius cheliferus →0 → 0, Corophium volutator + Corbicula fluminea→Assiminea sp→Chinomantes dehaani, Eohaustorius cheliferus →Assiminea sp→Chinomantes dehaani, 0→Assiminea sp→Chinomantes dehaani, Elachisina sp.→ Assiminea sp. → Cerithidea largillierli, Umbonium thomasi -Eohaustorius cheliferus →0→0, Corbicula fluminea → Ilyoplax deschampsi + Assiminea sp.→0, Glauconome chinensis→Assiminea sp.→Cerithidea largillierli, Glauconome chinensis→Assiminea sp.→Perinereis nuntia.Through the analysis with related environment factors, it's concluded that salinity is an important factor influencing the species composition and community structure of benthos in the subtidal zone while there was not any predominance factor in the intertidal zone but the synthetical function by all kind of environment factors.c. Dominant group III: euryhaline organisms whose distribution cover the whole environmental gradient of the estuary. This group is used to study the spreading, distribution, and changes of benthic macro-invertebrate in the Yangtze Estuary.For this group, there are 1 species, Neoeriocheir leptognatha in the subtidal zone, and 3 species in the intertidal zone, Corophium volutator, Dentinephtys galbra, and Assiminea latericea.Dentinephtys galbra is detailedly studied and found that it is the earlier resident of the estuary and regarded as an indicator species of the estuary.3. The changes of benthic macro-invertebrate dominant group II is studied. The variety of the short time scale (seasonal) is resulted from the general life history of the animals, i.e. the animal behavior adapting the environmental factors, such as temperature, sunshine, etc. In a longer time scale, there are no obvious changes for dominant species II. Once the lower tidal zone, the middle tidal zone, and the higher tidal zone in the intertidal zone formed completely, the structure of the dominant group II in those zone became stable. They would not change significantly only if there were certain human activities. With the land growing up, some terrestrial animals (such as insect larvae) immigrate, which leads to the changes of species composition and hierarchical diversity. Artificial engineering often increase the quantity of the dominant group II. This phenomenon shows that there are plenty of sedentary and adhering benthos juveniles. They are opportunists to grow up provided adapt circumstance occurs. With spatiotemporal interchange, the changes of dominant group II in the new emergent shoals could be forecasted, although changes process actually is a long time behavior of a system.