Trophic-functional patterns of marine periphytic protozoan communities during colonization of artificial substrates immersed at different depths in Chinese coastal waters of the Yellow Sea

Abstract

Trophic-functional patterns of periphytic protozoan communities are routinely used as a tool for marine bioassessment. In this study, a biofilm sampling approach was used to evaluate the effect of water depth on trophic-functional groupings of periphytic protozoa during the colonization process in Chinese coastal waters of the Yellow Sea. A total of 240 glass microscope slides were used to collect the protozoan assemblages at four water depths, i.e., 1, 2, 3.5 and 5 m, after immersion periods of 3, 7, 10, 14, 21 and 28 d. Four trophic-functional groups (TFgrs) were recorded from a 92-species abundance dataset, namely algivores (TFgr A), non-selectives (TFgr N), bacterivores (TFgr B) and predators (TFgr R), comprising 39, 26, 17 and 10 species, respectively. The TFgrs differed with depth in the water column in both relative species number and relative abundances. TFgrs A and N generally dominated the samples and increased in abundance with increasing depth from 1 m to 3.5 m, whereas TFgrs B and R decreased in abundance with increasing depth. Distance-based redundancy analysis (dbRDA) demonstrated that the colonization dynamics in trophic-functional patterns differed among the four depths. Multidimensional scaling ordinations (MDS) based on bootstrap average analyses revealed a clear shift in trophic-functional groupings from surface to deeper layers. This study shows that an optimal sampling strategy needs to be developed for marine bioassessment.