Download Alex Collazo February 20, 2011 Literature Summary #3 Good, but

Alex Collazo
February 20, 2011
Literature Summary #3
Good, but be careful with your writing. 10/10
Wedekind, C., M. O. Gessner, F. Vazquez, M. Maerki, and D. Steiner. 2010. Elevated resource availability
sufficient to turn opportunistic into virulent fish pathogens. Ecology 91:1251–1256.
C. Wedekind1,2,5, M. O. Gessner2,3, F. Vazquez4, M. Maerki4,6, and D. Steiner2
1
Department of Ecology and Evolution, Biophore, University of Lausanne, 1015 Lausanne, Switzerland
Department of Aquatic Ecology, Eawag: Swiss Federal Institute of Aquatic Science and Technology, 6047
Kastanienbaum, Switzerland
3
Institute of Integrative Biology (IBZ), ETH Zurich, 8600 Zurich, Switzerland
4
Department of Surface Waters, Eawag: Swiss Federal Institute of Aquatic Science and Technology, 6047
Kastanienbaum, Switzerland
2
1) The research problem or question.
How do environmental changes in aquatic environments such as inorganic or organic enrichment affect
the resource availability for some species and could thus cause an increase in pathogens/disease; an
increase in stress is also a possibility which leads to “opportunistic pathogens” turning pathogenic in
hosts.
2) The general background knowledge leading up to this study.
Adding organic or inorganic materials to an aquatic environment leads to a potential increase in the
local species contracting an infection; this may come from several parasites such as helminthes or
protozoans. Microbes play {??} have a symbiotic relationship with animals and if the conditions are
right, things like stress and poor living conditions can lead to some of these microbes becoming
pathogenic in their respective hosts. The whitefish Coregonus suitieri was studied and how the
availability of resources affects the microbial interaction with the species and whether this leads to an
opportunistic infection by the commensal microbes.
3) The methods used by the investigators.
Eggs from the species Coregonus suitieri were grown in individual wells, some of which contained a mix
of antibiotics to prevent bacterial growth while others were allowed to grow in normal water. The
embryos were prepared and placed in the experiment using as many sterile techniques as possible. Eggs
were allowed to grow and then observed daily to see: 1) which hatched and which died 2) which eggs
looked dead by examining a lack of blood flow in the embryo and an opaque, cloudy environment within
the egg.
4) The results of the study.
Resource availability in certain wells led to increased bacterial numbers, and a decrease in healthy
embryos (shown in Fig3). It was shown that there is a correlation between resource availability and
whitefish counts; which means a large amount of organic matter such as sewage becoming introduced
into an aquatic environment will give rise to large microbial populations which use up local nutrients and
change the local environment. This also causes undue stress onto the whitefish populations which leads
to a decreased immune system and a potential for opportunistic pathogens to take over the host.
5) What are the weaknesses of the study.
The study did a great job of explaining how changes in the aquatic environment could lead to
opportunistic pathogens causing illness but they failed to address a topic brought up earlier:
parasites. It was shown that large amounts of organic materials in the ecosystem would cause a
decrease in the effectiveness of the whitefish immune systems (increased stress and lack of
available resources) which may then allow parasites to easily replicate within the hosts but it was
not mentioned in the report.
6) What we learned new from the study.
We learned from this study that pollution in an aquatic environment (such as lakes, ponds, river,
oceans etc) may give rise to large colonies of pathogenic microbes which decrease the local
resource availability; this in turn causes harm to local species of fish and they are then much more
susceptible to infectious agents such as parasites, opportunistic pathogens or simply malicious
microbes.
Link: http://www.esajournals.org/doi/full/10.1890/09-1067.1