| Cage culture is an important development direction of mariculture,which needs to feed a large number of baits and produce lots of excretions in the process of aquaculture.Scientifically evaluate the impact of cage culture on marine ecological environment is helpful to protect the marine ecological environment and evaluate the capacity of aquaculture,and promote the sustainable and healthy development of large-scale cage aquaculture.Maniao Bay,located in Chengmai County,Hainan Province,is a tropical sea and an ideal area for mariculturing.According to the distance gradient,28 survey stations were set up in Maniao Bay,which could be divided into aquaculture zone(P),the edge of the breeding zone(Z),0.5 km from the breeding zone(A),1.5 km from the breeding zone(B),2.5 km from the breeding zone(C).An annual survey of macrobenthos composition and sediment condition in Maniao Bay was conducted in July(summer),October(autumn),December(winter)in 2019 and May(spring)in 2020,to analyze the impact of cage culture on the sediment environment and macrobenthos community.The main results as follows:1.A total of 122 species of macrobenthos,which belonged 11 phylum were collected,Annelids were the dominant species with 59 species(48.36%);followed by 25 species of Mollusks(20.49%);20 species of Arthropods(16.39%)and 4 species of Echelminthes(3.28%),etc.The number of species in summer was the least(31),then in spring was the most(63),the number of species in autumn and winter was 38 and 32,respectively.2.In summer,the highest density was zone Z(66.67 ind/m~2),and the highest biomass was zone P(14.36 g/m~2);none of macrobenthos were collected in Zone C.The highest density in autumn was zone Z(44.44 ind/m~2)and the lowest was zone C(18.52 ind/m~2);the highest biomass was Zone C(21.45 g/m~2)and the lowest was Zone B(1.20 g/m~2).In winter,the highest density was zone Z(75.56 ind/m~2)and the lowest was zone A and B(22.22 ind/m~2);The highest biomass was zone Z(7.38 g/m~2)and the lowest was zone B(0.21 g/m~2).In spring,the highest density was zone Z(108.89 ind/m~2)and the lowest was zone B(59.26 ind/m~2);the highest biomass was zone P(16.11 g/m~2)and the lowest was zone B(1.25 g/m~2).3.A total of 11 dominant species were found,the most of dominant species were in autumn(5 species),followed by winter(4 species)and spring(4 species),summer(2species).Among all the dominant species,the optimal of dominant species was Nemertea sp.,which occupied the dominant position in four seasons;the second is Xenophthalmus pinnotheroides,which appeared in both autumn and winter.4.The range of Shannon-Wiener index(H’),Pielou index(J’),Margalef index(d)and Simplicity index(C)in summer were(0.81-2.50),(0.48-1.00),(0.22-0.82)and(0.19-0.69)respectively,the the most stable of community structure was in zone Z.In autumn,they were(0.67～0.85),(0.43～0.70),(0.15～0.41)and(0.54～0.72)respectively,the stability of community structure in zone A and zone Z were better than other zone.In winter,they were(0～1.50),(0～0.94),(0～0.52)and(0.48～1.00)respectively,the most stable of community structure was in zone Z,followed by zone P.In spring,they were(0.80～2.47),(0.51～0.98),(0.21～0.81)and(0.20～0.68)respectively,the best stability of community structure was in zone Z.5.The density of macrobenthos was significantly correlated with the distance,season,and distance×season(P<0.01),while the biomass was not significantly correlated with those.There was non-significant correlation between the contents of OC,SOx,TP,TN,sediment mass fraction and the density,biomass,community structure characteristic index of macrobenthos.In conclusion,cage culture in Maniao Bay had a certain impact on the marine ecological environment.The habitat density,biomass and diversity index of macrobenthos increased significantly in the area around the cage culture.In summer and autumn,the density in the breeding area was lower than that in the edge of the breeding area;In spring and winter,the sediment pollution was alleviated,and the density of macrobenthos increased in all regions.The density of macrobenthos was significantly correlated with distance,season and distance×season(P<0.01),but the contents of OC,SOx,TP,TN in the sediment,as well as the grain size of the sediment didn’t have significant correlation. |
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