Characteristics Of Macrobenthic Communities In Coastal Wetlands With Different Vegetation Types In Jiulong River Estuary

Mangrove forests and salt marshes are important coastal wetland ecosystem types in the intertidal zone,and macrobenthos is an important component.Therefore,both mangrove forests and salt marshes have a large number of researches about macrobenthos.However,there was less comparative study of salt marshes and mangroves in adjacent areas.In addition,there were more reports on the effects of exotic plants on macrobenthos both in mangrove forests and salt marshes.However,few studies about the effects of exotic plants on mangrove forests and salt marshes macrobenthos at the same time were conducted.We conducted the study of the physical characteristics of sediments and sampling of macrobenthos at Kandelia obovata,Sonneratia apetala,Cyperus malaccensis,Spartina alterniflora,which are two kinds of woody plant habitats and two kinds of herbal habitat.This study was focused on the spatial and temporal changes,biological indices and secondary productivity of macrobenthos,and the correlation between macrobenthos and environmental factors in coastal wetlands with different vegetation types was analyzed by using the diversity index and abundance-biomass curve.This investigate would provide the theoretical basis for the management and protection of coastal ecosystems.(1)83 macrobenthos were collected in Jiulong River Estuary mangrove reserve.33 Polychaeta,26 Gastropoda,15 Crustacean,4 Bivalvia,3 Oligochaeta,2 Sipuncula,the other eleven.In the biotopes of Spatina alterniflora,we collected more macrobenthos species than the other three kinds of biotopes.The largest value of species was 48 in Cyperus malaccensis,the lowest value of species was 37 in Sonneratia apetala.(2)In the Jiulong River Estuarry,the average density of macrobenthos was 1334 ind·m-2.The average density of Polychaeta which was the dominant species was 306 ind·m-2 and the proportions of all the stations for Polychaeta(22.96%)were high in the group.The highest average density of macrobenthos was 1463 ind·m-2 in Kandelia obovata and the lowest 1191 ind·m-2 in Sonneratia apetala.The seasonal variation of the density of macrobenthos was very significant difference.The average biomass of macrobenthos was 45.21 g·m-2.The proportions of all the stations for Crustacean was the highest in the group and the average biomass of Crustacean is 15.86 g·m-2 and the lowest of Oligochaeta was 0.40 g·m-2.The highest average biomass of macrobenthos was 94.20 g·m-2 in Sonneratia apetala and the lowest average biomass of macrobenthos was 22.87 g·m-2 in Kandelia obovata.The biomass of macrobenthos in coastal wetlands with different vegetation types was very significant difference.(3)There were difference between the seasonal variation and different biotopes.The content of TP and TOC between different biotopes was significant differences and there was no difference between seasons.The correlation between species,density,biomass and environmental factors of macrobenthos was analyzed by Pearson correlation analysis.There were positive correlations between the species of macrobenthos and root biomess;there was no correlation between density and environmental factors and there were positive correlations between the biomass of macrobenthos and TOC,and there were negative correlations between the biomass of macrobenthos and TN,and there were negative correlations between the biomass of macrobenthos and TP.(4)The average secondary productivity was 8.40 g(AFDW)·m-2·a-1 in different biotopes.The highest average secondary production of macrobenthos was 13.68 g(AFDW)·m-2·a-1 in Sonneratia apetala and lowest was 4.26 g(AFDW)·m-2·a-1 in Kandelia obovata.In terms of seasonal difference of average secondary production of macrobenthos,winter was the highest while autumn was the lowest.Compared with the secondary productivity of macrobenthos in coastal wetlands with different vegetation types,the proportions of Polychaeta,Sipuncula and Bivalvia were highest.The proportion of Crustacean in the habitat of Spartina alterniflora was highest in the group.The proportions of Gastropods and Oligochaeta were highest in Cyperus malaccensis.(5)The environmental health of macrobenthos in Jiulong River Estuary was analyzed by using Abundance Biomass Comparison curve(ABC method).The result shows that the habitat of Kandelia obovata was slightly disturbed,the habitat of Spartina alterniflora was healthy,the habitat of Sonneratia apetala and Cyperus malaccensis was moderate interfered.Compared with the result analyzed by biological diversity index,the habitat of Kandelia obovata was slightly disturbed and the other three habitats were seriously disturbed.There was deviation between the two methods.Similarities and differences in macrobenthic assemblages of different habitats analyzed by using cluster analysis and nonmetric multidimensional scaling(MDS)shows the structure of the macrobenthos community between the two biotopes of the Cyperus malaccensis and Spartina alterniflora was similar and the two biotopes of Kandelia obovata and Sonneratia apetala was similar.