They collected samples of sediment from 2
different locations. The first location was Cullen Bay Marina in Darwin
Harbour, Australia, and the second was Dinah Beach, on the Eastern side of
Darwin. Cullen Bay has been subjected to the introduction of metal
contaminants, mainly copper and zinc. Copper was introduced in large quantities
in the late 1990’s because the Black Striped Mussel Mytilopsis sallei was found to have invaded the area, so this
action was taken in order to prevent their establishment and invasion. Copper
sulphate and sodium hypochlorite were added over the course of several weeks to
sterilise the water. Zinc has also been added to the water as a result of
commercial and recreational boating activities.
The particular polychaete chosen for this study was Ophelina sp.1. Opheliids are generally non-selective deposit feeders and burrow just below the surface in sandy and muddy substrates. They are also known to have recolonised the Cullen Bay area post-metal introduction, hence why this polychaete was chosen. Analyses showed that sediments from Cullen Bay contained roughly 8 times more copper, and 3 times more zinc than Dinah Beach sediments. In fact, the copper concentrations were over 170ppm, exceeding the interim sediment quality guideline (ISQG) of 65ppm, and the zinc concentrations were 290ppm, also exceeding the ISQG of 200ppm.
The bacterial community associated with Ophelina sp.1 in Cullen Bay was different to that of the Dinah Beach polychaetes. There was a similarity in diversity, however the species present were different. This coincided with the higher concentrations of copper and zinc in Cullen Bay sediments compared with the sediments at Dinah Beach. Bacteria from the order Alteromonadales were found to be more abundant on polychaetes from Cullen Bay. Alteromonadales are associated with deep-sea polychaetes and show a tolerance to high levels of copper. They have also been found to increase in abundance in areas of eutrophication and urbanisation. Some species are known to be metal resistant, and the authors suggest that Alteromonadales associated with Ophelina sp.1 in Cullen Bay may bind metals and reduce their toxicity.
The particular polychaete chosen for this study was Ophelina sp.1. Opheliids are generally non-selective deposit feeders and burrow just below the surface in sandy and muddy substrates. They are also known to have recolonised the Cullen Bay area post-metal introduction, hence why this polychaete was chosen. Analyses showed that sediments from Cullen Bay contained roughly 8 times more copper, and 3 times more zinc than Dinah Beach sediments. In fact, the copper concentrations were over 170ppm, exceeding the interim sediment quality guideline (ISQG) of 65ppm, and the zinc concentrations were 290ppm, also exceeding the ISQG of 200ppm.
The bacterial community associated with Ophelina sp.1 in Cullen Bay was different to that of the Dinah Beach polychaetes. There was a similarity in diversity, however the species present were different. This coincided with the higher concentrations of copper and zinc in Cullen Bay sediments compared with the sediments at Dinah Beach. Bacteria from the order Alteromonadales were found to be more abundant on polychaetes from Cullen Bay. Alteromonadales are associated with deep-sea polychaetes and show a tolerance to high levels of copper. They have also been found to increase in abundance in areas of eutrophication and urbanisation. Some species are known to be metal resistant, and the authors suggest that Alteromonadales associated with Ophelina sp.1 in Cullen Bay may bind metals and reduce their toxicity.
Dinas Beach
polychaetes had becteria of the order Oceanospiralles
associated with them. Oceanospiralles
are usually associated with the gut of bone-eating polychaetes and are thought
to metabolise carbon. The Oceanospiralles
associated with Ophelina sp.1 may
benefit from the higher organic carbon levels at Dinah Beach, provided by
nearby mangroves.
Bacteria which are associated with polychaete worms could be a useful indicator of pollution because polychaetes are readily available, easy to find, easy to collect and are present in most marine systems. Changes in the bacteria can be directly related to the surrounding conditions because many polychaetes are sedentary, or have specific requirements for their habitat, so movement is restricted to a local scale.
I found this study fairly interesting, however I found some parts quite confusing. I think that more studies should look at the bacteria associated with indicator species to see if and how their associated bacteria help them adapt to changes in their surroundings.
Bacteria which are associated with polychaete worms could be a useful indicator of pollution because polychaetes are readily available, easy to find, easy to collect and are present in most marine systems. Changes in the bacteria can be directly related to the surrounding conditions because many polychaetes are sedentary, or have specific requirements for their habitat, so movement is restricted to a local scale.
I found this study fairly interesting, however I found some parts quite confusing. I think that more studies should look at the bacteria associated with indicator species to see if and how their associated bacteria help them adapt to changes in their surroundings.
Hi Hannah! I find this topic very interesting, last year I wrote an essay about how mercury resistant bacteria can provide an adaptive advantage to their host. For instance, macrophytes in a polluted lake had significantly less tissue damage due to an apparent symbiosis with mercury resistant bacteria able to reduce Hg(2+) to the relatively inert Hg(0)(caslake et al. 2006). Similarly fish in a highly polluted area around Calcutta had mercury resistant bacteria in their gut, which offered protection to the host against the toxicity of mercury compounds (Sadhukan et al 1997). Horizontal gene transfer of the mer operon, the genes responsible for this mercury resistance in bacteria, is thought to have resulted in a significant increase in mercury resistance in bacteria in coastal waters (Ramaiha and De 2003).
ReplyDeleteBeyond the ecological importance of these bacteria for the environment and host, their potential application in the bioremediation of waste waters is very interesting.
Did the authors from your paper (reference?) give any reference about the degree of differences in associated bacterial communities normally expected to be found between polychaetes from two different locations (without heavy metal pollution)?
References:
Ramaiah, N. and De, J.(2003). Unusual rise in mercury resistant bacteria in coastal environs.
Microbial Ecology. 45, p444-454.
Sadhukhan, P. C., Ghosh, S., Chaudhuri, J., Ghosh, D. K. and Manal, A. (1997). Mercury and
organomercurial resistance in bacteria isolated from freshwater fish of wetland fisheries around Calcutta. Environmental Pollution. 97, p71–78.
Caslake, L.F., Harris, S.S., Williams, C., Waters, N.M. . (2006). Mercury-Resistant Bacteria Associated With Macrophytes from A Polluted Lake. Water, air, and soil pollution. 174 (1-4), p93–105.
Anna, sorry I've taken so long to reply, the dissertation has slowly been taking over my life!
ReplyDeleteI can't believe I forgot the reference, its:
Neave, M. J., Streten-Joyce, C., Glasby, C. J., McGuinness, K. A., Parry, D. L. & Gibb, K. S. (2012). The Bacterial Community Associated with the Marine Polychaete Ophelina sp.1 (Annelida: Opheliidae)is Altered by Copper and Zinc Concentrations in Sediments. Microbial Ecology. 63: 639-650.
Wow, that's really interesting, I'll definitely have a read of those papers.
No, the authors didn't state any differences in bacterial communities that would normally be expected. The only seem to say why they picked that particular polychaete, and then the difference in bacterial communities present in the host at the polluted and non-polluted areas.
Thanks for your question, I didn't think of that.