Final Activity Report Summary - PROTISTAN DIVERSITY (The Application of Protistan Diversity and Community Analysis, an integrated approach to Water Quality Assessment) Protists are microbial eukaryotes that are ubiquitous, diverse and major participants in oceanic food webs and marine biogeochemical cycles. Diversity underpins ecosystem functioning and the services that support human well-being, yet protistan diversity and its relationship with water quality in coastal ecosystems is not yet fully appreciated. This project sought to provide Dr Gong with an array of molecular skills to investigate the relationship between protistan diversity and water quality or environmental stresses during his return phase. We collected samples from five sites of the Jiaozhou Bay, a heavily polluted bay connecting with Yellow Sea. By using Polymerase chain reaction (PCR), construction of 18S recombinant deoxyribonucleic acid (rDNA) libraries, screening and sequencing, protistan diversity, as indicated by Operational taxonomic units (OTUs), was correlated with environmental parameters. Our preliminary conclusions were that water temperature and nutrients explained the distribution of planktonic protists most, while heavy metals might affect the benthic community. A relevant manuscript was in preparation by the time of the project completion. Picoeukaryotes in mariculture waters though remained understudied. Through the use of clone library, Fluorescence in situ hybridisation (FISH) technique with specific probes and electronic microscopy, we were able to get insight into their diversity and distribution for the first time. Our data provided evidence that four picoeukaryotic populations served as a trophic link between bacteria and nanoplankton, thus they might play an important role in eutrophic seawaters and could be a potential bioindicator in environmental biomonitoring. A relevant manuscript was also in preparation by the time of the project completion. In addition, Dr Gong collaborated with Prof. J. K. Choi from Inha Univ, Korea, and Prof. W.C. Zhang from the Institute of Oceanology, Qingdao, on linking morphotypes with molecular signatures of a widely distributed planktonic ciliate. A manuscript on systematics of favella ehrenbergii was submitted to the Journal Eukariotic Microbiology for review. Collaborative work on the ecological roles of protists and prokaryotic microbes in sediments was also in progress between Dr Gong and Prof. C. Dupuy from the Centre National de la Recherche Scientifique (CNRS), Universite de La Rochelle, France.