Developments in aquatic microbial ecology at Cefas

Studies assessing the state of marine ecosystems aim to predict the extent to which man-made impacts may influence marine organisms. Analyses of multi-cellular benthic communities are used most frequently because as a group the organisms within these communities are largely sedentary and therefore must withstand environmental pressures or perish.

Unicellular Archaea and bacteria are not yet included in marine environmental impact studies despite these organisms playing a fundamental role in benthic ecosystem function. To date, bacteria have been used as indicators for sanitary risks and measures of general water quality in freshwaters. Furthermore, the presence of specific bacteria and viruses is also assessed in animal health surveys, especially to maintain food safety.

A new project at Cefas "Utilising molecular techniques to assess the relative roles of environmental and human pressures on aquatic microbial communities" aims to investigate the response of archaeal and bacterial communities to marine environmental change.

Marine environmental research generally focuses on the distribution and abundance of organisms and the interactions both amongst and between organisms and their environment. These interactions contributing to the functioning of biological systems and processes; such interactions ultimately affecting their surrounding environment. In cases where natural or man-made impacts (e.g. pollution) are suspected to cause changes in marine populations, different types of impact studies can be conducted to understand the type of effects caused and to assess the relative sensitivities of organisms to such impacts. In order to determine such changes the "community" is often selected as a unit for measuring such impacts. This new three year Cefas project aims to examine changes in marine microbial communities as indicators of environmental quality.

Genetic Fingerprinting methods are being applied to analyse the composition of microbial communities in marine sediments. These include DGGE (Denaturing Gradient Gel Electrophoresis), RISA (Ribosomal Intergenic Spacer Analyses) and T-RFLP (Terminal Restriction Fragment Length Polymorphism). Additionally, phylogenetic analyses will be based on sequence information of 16S rRNA gene fragments. In order to elucidate which impacts influence specific microbial communities and specific microbial phylotypes we are using multivariate statistics like nonmetric multidimensional scaling (MDS) or gradient analyses like Canonical Correspondence Analysis (CCA). The project is in its early stages but ultimately aims to improve our ability to determine the health of the marine environment.

Virtual example of a CCA biplot of DGGE fingerprints using organic C (org.C), chlorophyll a (Chl a), depth, macrobenthos and meiobenthos community, grain size, and the nutrients nitrate (NO3), nitrite (NO2). Circles indicate bacterial communities, and numbers near the symbols indicate a sampling station (2-5). Arrows indicate the direction of increasing values of the respective variable, and the length of arrows indicates the degree of correlation of the variable with community data.

If you are interested in discussing this project please contact Melanie.Sapp@cefas.co.uk