| In recent decades,habitat degradation,fishery resources depletion and biodiversity lost in the north Yellow Sea have become increasingly prominent caused by various anthropogenic and natural factors,including overfishing,population explosion,pollution and climate change.To rebuild marine habitats,restore fishery resources and cultivate sea treasures,artificial reefs represented by rocky reefs,concrete reefs and ship reefs transformed from derelict fishing ships have been widely deployed along the coast of the northern Yellow Sea.Subsequently,related evaluation of ecological effect of artificial reefs have been carried out to clarify the mechanism of ecosystem functioning and to improve the theoretical basis for the design,planning and deployment of reefs.These studies mentioned above are usually based on spatial and temporal perspectives,focusing on the impact of the same type of artificial reefs on natural ecosystems and the dynamic changes of ecosystems after reefs establishment,but the evaluation of ecological performance of artificial reefs with different types has not yet been reported.It is necessary to comparative study the ecological effects of different types of artificial reefs scientifically and systematically,which can not only meet the policy requirements of establishment programs for marine ranching,but also provide basic reference for the construction of the marine ranching mode of the whole life history of fishes.Based on the above research background,concrete artificial reef habitat,rocky artificial reef habitat,ship artificial reef habitat and adjacent natural habitat in Xiaoshi Island waters,Weihai were selected to carry out the comparative studies of three typical types of artificial reef habitats from the perspectives of community structure of benthic fish,nutrient information of dominant species,energy flow characteristics of the ecosystem and environmental quality of artificial habitats,respectively.The main results are as follows:(1)To investigate the effects of different types of artificial reef habitats on the community structure of benthic fish,the monthly sampling of benthic fish communities in three types of artificial reef habitats and adjacent natural habitat was performed by using trap units from September 2020 to August 2021.The results showed that all three types of artificial reef habitats can enhance the diversity variables of benthic fish communities,fish abundance,species richness and Shannon-Wiener’s index of concrete artificial reef habitat were generally better than the other two,and the fish biomass of ship artificial reef habitat was significantly higher than that in rocky artificial reef habitat(P<0.001).For the spatial distribution patterns ofbenthic fish with different size classes,rocky artificial reef habitat hosted more small fish,while ship artificial reef habitat supported more big fish.The nMDS ordination revealed that only concrete artificial reef habitat and rocky artificial reef habitat hosted similar community composition of benthic fish,and all types of habitats showed significant differences in community composition between winter-spring and summer-autumn(P<0.001).In addition,Environmental factors,especially water temperature,can also affect the community composition by affecting the migration of temperature-preferred species.(2)To understand the differences in trophic ecology information of rocky reef fish in different types of artificial reef habitats,a case study of typical rocky reef fish in the north Yellow Sea,Hexagrammos otakii and Sebastes schlegelii were investigated for the comparative analyses of both dietary composition and trophic niches in this study.The stomach content analysis showed that H.otakii displayed a higher diversity of prey composition than S.schlegelii,and the highest diversity values for both entire populations were in concrete artificial reef habitat;when constrained by size class,the highest diversity values of 0-15 cm groups were both in rocky artificial reef habitat,while the bigger size classes were higher in ship artificial reef habitat.For prey composition,similar patterns of spatial difference were observed in different size classes of both H.otakii and S.schlegelii to their entire populations,and the differences were also mainly concentrated between ship artificial reef habitat and concrete artificial reef habitat or rocky artificial reef habitat.However,the disproportionation prey species that caused spatial differences in dietary composition differed by species and size class,including decapodas,teleosts,polychaetas and amphipods.The results of SIMMR mixing models indicated that the diets of both fish species differed significantly with species,habitat and size class,and were generally consistent with the results of stomach content analysis.The analysis of trophic niche revealed that the highest trophic niches of both entire populations were in concrete artificial reef habitat,while the trophic niches for small-sized and large-sized fish were higher in rocky artificial reef habitat and ship artificial reef habitat,respectively.(3)Based on the survey data of Xiaoshi Island waters and relevant references,Ecopath models at concrete artificial reef habitat,rocky artificial reef habitat,ship artificial reef habitat and adjacent natural habitat in Xiaoshi Island waters were established to evaluate the effects of the construction of artificial reef habitats with different types on the energy flow patterns and system characteristics of the ecosystem.The results showed that the total system throughputs in concrete artificial reef habitat,rocky artificial reef habitat and ship artificial reef habitat were 8071.42t/km2/year,6336.55t/km2/year and 7864.71 t/km2/year,respectively,which were higher than the value of natural habitat(4183.58t/km2/year),indicating that all types of artificial reef habitats enhanced the scale of the ecosystems.The function groups could be clustered into five trophic levels in all four Ecopath models,with energy occupied by the function groups with lower trophic levels outweighed others.Phytoplankton,algae and detritus were the main energy sources for all four ecosystems,whereas the proportion of energy directly derived from primary productivity in trophic level Ⅱ was higher,from highest to lowest in rocky artificial reef habitat(65.16%),concrete artificial reef habitat(59.58%),ship artificial reef habitat(56.84%)and natural habitat(53.80%).The mean trophic level value of natural habitat(2.92)was significantly higher than that of artificial habitats,while the value of ship artificial reef habitat(2.84)was higher than that for concrete artificial reef habitat(2.35)and rocky artificial reef habitat(2.24).In addition,the ecosystem attributes of the three types of artificial reef habitats such as total primary production/total respiratory,system omnivory index and connectance index were in the middle and upper levels compared with natural habitat and other artificial ecosystems in adjacent areas,suggesting that all three artificial reef ecosystems have achieved high level maturity and stability.(4)Meiofauna is a common biological indicator for aquatic ecosystem quality assessment.In this research,meiofauna communities in concrete artificial reef habitat,rocky artificial reef habitat,ship artificial reef habitat and adjacent natural habitat were characterized based on highthroughput sequencing,and the response mechanism of these communities to different types of artificial reef habitats was also explored.The results showed that a and β diversity of meiofauna communities differed significantly on both spatial and temporal scales(P<0.001),for example,Shannon-Wiener’s diversity index and Pielou’s evenness index were significantly higher in rocky artificial reef habitat than in other habitats;and all habitats supported significantly different community composition except for concrete artificial reef habitat and ship artificial reef habitat in winter and spring.The spatial differences were mainly contributed to the flow field effects and biological effects generated by artificial reef habitats,while temporal differences were driven by temperature and dissolved oxygen.The dominant taxa of meiofauna included arthropods,annelids,platyhelminths and nematodes.Platyhelminths were mainly positively influenced by artificial habitats but annelids were the opposite.Co-occurrence network analysis revealed that the communities in natural habitat were more sensitive to environmental change than that in artificial reef habitat,while the performances of the communities in concrete artificial reef habitat and ship artificial reef habitat were more stable.In summary,meiofauna can respond accordingly to flow field and biological effects generated by different types of artificial reef habitats,and could be superimposed over the normal seasonal effects. |
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