Effects of Global Warming on Functional Diversity and Resilience of Bacterioplanktion in the North Atlantic Ocean
The aim of this Ph.D. project is to establish a reference point for studies on effects of global climate changes on bacterioplankton diversity and turnover of dissolved C and N in the North Atlantic Ocean.
It has recently been demonstrated that the flow of cold dense water from the Nordic Sea into the Atlantic Ocean via the Faroe Bank Channel has decreased during the last 50 years (Hansen et al. 2001; Nature 411: 927-930), possibly as a result of global warming. If this trend continues the Gulf Stream may be severely reduced resulting in a cooling of the North Atlantic Ocean.
Heterotrophic bacteria are recognized as links between the primary producers (or more correctly, dissolved organic matter) and higher trophic levels via the microbial loop. Therefore, changes in the composition of the bacterial communities - induced by temperature and salinity shifts - may possibly influence the flux of dissolved carbon and nitrogen through the food webs and, hence, affect top-predators of commercial value (e.g. fish). While the functional diversity and resilience of the bacterioplankton communitites in the North Atlantic Ocean are largely unknown, the lability of marine bacterial communities in response to environmental changes have been documented (e.g. Frette et al. 2002; Appl. Environ. Microbiol. submittted). Also, studies on disease causing bacteria, and how they may be affected by global climate changes, have been published (e.g. Rose et al. 2001; Environ. Health Perspectives, 109, suppl. 2: 211-221; Oliver et al. 1995; Appl Env Microbiol, 61: 2624-2630). Thus, there is a need for baseline studies on diversity, functionality, and natural variability of pelagic bacterial communities in the North Atlantic to allow assessment of potential global warming effects.
Water samples needed for the investigations will be provided by the Faroese Fisheries Laboratories, as part of their monitoring program. Samples will be repeatedly collected throughout a year at three different localities to allow examination of the natural (annual and spatial) variation.
Water samples will be examined at the community as well as the single cell levels, by use of culture dependent and culture independent techniques. At the community level, the genotypic diversity will be examined by novel clone libraries of partial 16S rDNA gene sequences, and by DGGE or T-RFLP profiles. The functional diversity will be examined by BIOLOG assay, microarray DNA-chips (development in progress at University of Copenhagen) or microautoradiography along with Fluorescence In Situ Hybridisation (FISH). To allow correlation between the genetic and functional diversity, and the turnover of C and N by the planktonic communities, total bacterial counts (flow cytometry), bacterial production (uptake of tritiated thymidine), phytoplankton biomass (Chl A) and primary production will be measured. Some of these measurements will be performed onboard the research vessel. At the single cell level, measurements will include FISH to investigate in situ distribution of bacterial groups, and activity measurements by the use of fluorescent probe techniques. Culturing and functional characterisation of isolates will also be performed.
Senior Lecture Søren Sørensen
Dept. of General Microbiology, Inst of Molecular Biology,University of Copenhagen
Sølvgade 83H, DK 1307K Copenhagen
Phone: 45 35 32 20 53, Fax: 45 35 32 20 40
Director of research Niels Kroer
National Environmental Research Institute
Dept. of Microbial Ecology and Biotechnology
Frederiksborgvej 399, DK-4000 Roskilde
Phone: 45 46 30 13 88, Fax: 45 46 30 12 00
e-mail: [email protected]