Effects of Global Warming on Functional Diversity and
Resilience of Bacterioplanktion in the North Atlantic Ocean
Aim
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.
Project Description
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.
Methodology
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.
Contact persons
Senior Lecture Søren Sørensen
Dept. of General Microbiology,
Inst of Molecular Biology,University of Copenhagen
Sølvgade 83H, DK 1307K Copenhagen
Denmark
Phone: 45 35 32 20 53, Fax: 45 35
32 20 40
e-mail: [email protected]mermaid.molbio.ku.dk
Director of research Niels Kroer
National Environmental Research
Institute
Dept. of Microbial Ecology and
Biotechnology
Frederiksborgvej 399, DK-4000
Roskilde
Denmark
Phone:
45 46 30 13 88, Fax: 45 46 30 12 00
e-mail:
[email protected]