Seasonal variability in free-living marine nematode community structure in a sandy beach of the Taiping Bay of Qingdao, China

Nematode assemblage composition,trophic structure and biodiversity were followed over an annual cycle in a sandy beach of the Taiping Bay of Qingdao,China.Nematode assemblage in the sandy beach maintained a high genus diversity (75 genera).Micro-laimus and Bathylaimus were the dominant genus of the nematode assemblage,accounting for 66% of the total nematode abun-dance.The nematodes' dominant trophic structure changed seasonally as a response to the seasonal changes in food quality.Epi-growth-feeder nematodes (2A) were the dominant trophic groups in the trophic structure with the highest abundance in spring be-cause of phytoplankton bloom,while the feeding type (1B) showed higher abundance in summer that was due to the increasing of sediment detritus after spring bloom.Furthermore,species diversity and evenness calculated on nematodes identified to the genus level displayed significant temporal changes,which was also reflected by the index of trophic diversity.According to the cluster analysis,the nematode community structure of the whole year was clearly separated into two periods ( A and B).Biota-Environ-ment matching (BIOENV) results showed that seawater temperature,sediment Chl a and grain size were responsible for the nema-tode community structure variation in spring and summer period (Period A).However,seawater/interstitial water temperature,interstitial water dissolved oxygen concentration,interstitial water salinity,and sediment Ph a a were more important in construc-ting the autumn and winter period ( Period B) nematode community structure.