| In order to reduce carbon emission,a worldwide transition of the energy structure is taking place from fossil fuels to renewable energy sources.The number of offshore wind farms(OWFs),as renewable energy devices,has increased rapidly around the world.Offshore wind farm is a new anthropogenic pressure for the marine environment.The potential environmental impacts generated by these new structures on marine ecosystems has attracted wide attention.Macrobenthos is an important part of marine ecosystem,and has a vital role in nutrient cycling and energy flow of marine food webs.At present,China’s basic research on the impact of offshore wind farms on the marine environment,ecosystems and natural resources is relatively lagging.There is no enough observation data involved benthic environment.In this study,monitoring of water quality and sediment sampling are conducted in close vicinity to a high-rise cap pile wind-turbine foundations in Pinghai Bay,Fujian,and to investigate the changes in environmental factors and macrobenthic community composition around it.This study provided the significant data for the assessment of the mesoscale and large scale ecological effect of offshore wind farm on marine environment,and provided a basis for competent department of Marine environment to strengthen the supervision and management of the ecological impact of offshore wind power projects.The main results are as follows:(1)The sediment type in the study area was clayey silt,mainly comprising silt and clay.The sediment grain size ranged from 6.22 μm to 7.66 μm,and the total organic matter content ranged from 5.89%to 6.38%.A total of 97 species were identified,including 61 Annelida,22 Arthropoda,eight Mollusca,four Echinodermata,one Sipuncula and one Chordata.The macrobenthic abundance and biomass was 605±310 ind/m2 and 8.2 ± 7.3 g/m2 respectively.The dominant species are Loimia medusa,Neoxenophthalmus obscurus,Aglaophamus dibranchis,Praxillella affinis,Barantolla sp.,Laonice cirrata and Notomastus aberans.(2)The establishment of OWF had little effect on the distribution of sediment particles and TOM%in Pinghai Bay.The species number,abundance and biomass of macrobenthos have significant differences in space.With the decrease of the distance from wind-turbine foundation,the abundance and the species number of macrobenthos showed an upward trend,and the biomass showed a downward trend.(3)Compared with historical data,the abundance increased by 158.92%for Annelida,59.68%for Arthropoda,and 450%for Echinodermata,whereas the abundance of Mollusca decreased by 78.46%,from 65± 100 to 14 ± 22 ind/m2.It is likely that most macrobenthos were able to recover quickly after the deployment of wind-turbine foundation,whereas more time might be needed for Mollusca to recover,and the Annelida had become the dominant group in the macrobenthic community.(4)Assessment results of The Shannon-Wiener diversity index shows that the benthic environment at each station is slightly disturbed and the habitat quality is "good";Assessment results of AMBI and M-AMBI indexes indicate that the environment of each station is slightly interfered,and the habitat quality is "high".Benthic assemblage was mainly composed of EG Ⅱand EGⅢ.Assessment results of BO2A index indicate that the ecological quality at each station is "good" or "high". |
