Hi Jailson, 

As per the info of Stefania and Meredith above, there appears to be a lot of variability among species on effects.  You can check out papers by Joanna Burger and Birgit Braune and others, and you will find immense variability in the levels of Hg in wild seabirds, including some high levels.  There have been cause-effect studies, too (see Science of the Total Environment 2012  443: 775-790; Ecotoxicology 2012 21: 2143), but these are often on eggs and look at hatchability, etc.  There are far fewer studies that look at effects on adults.  A recent one in Environmental Science & Technology (2014) by Fort et al. showed lower investment in egg mass by Dovekies with high Hg levels.

Ultimately, I remain unaware of an absolute "threshold" level yet, at least for seabird liver or muscle, because seabirds seem more tolerant of Hg than other taxa.  Certainly some studies have shown high levels of Hg associated with deleterious effects on the birds, but mechanisms etc. in seabirds still need to be looked at.  Mark

You could try:

Thompson DR. Mercury in birds and terrestrial mammals. In: Beyer WN, Heinz GH, Redmon-Norwood AW, editors. Environmental contaminants in wildlife: interpreting tissue concentrations. SETAC special publications series. Boca Raton, FL, USA: CRC; 1996. p. 341–56.

You may be able to view some parts of this book on Google books if you're not able to get a hard copy.

There are several factors that modify mercury concentration in seabirds, such as age, tissues, migratory pattern, and the most important, diet.

There are also species variability and recently many studies focused on feathers hg levels. Which species are you considering? Authors reported that sensitive birds can experience adverse effects at dietary concentrations of 50 to 500 mg Kg-1,  and level of 5 mg Kg-1 dry weight in feathers  have been associated with impaired reproduction.

Moreover, seabirds seem to be more resistant to the harmful effects of mercury because they are capable of detoxifying it (Ribeiro et al., 2009).

I recommend these ebooks:

Eisler, R., 1987. Mercury hazards to fish, wildlife and invertebrates: a synoptic review. In: Biological Report85(1.10).U.S. Fish & Wildlife Service, Washington, DC.

Burger, J., Gochfeld, M., 2002. Effects of chemicals and pollution on seabirds. In: Schreiber, E.A., Burger, J. (Eds.), Biology of Marine Birds. Peter L, Lutz, Boca Raton, London.

best regards, stefania

Dear all,

thank you very much for the feedback all you kindly provided.

I am working with Magellanic penguins, which I know that must be interpreted carefully when comparing the threshold based on taxonomicaly distant bird species. But, even though in the manuscript that I am working on I miss some information to discuss about the meaning of the concentrations that I found. Of course I have papers that address Hg in other penguin species and I could use it for comparison.

Anyway. I think you suggested very interesting literature that can be used in the way I am thinking about.

Thanks

J

Hi Jailson, 

As per the info of Stefania and Meredith above, there appears to be a lot of variability among species on effects.  You can check out papers by Joanna Burger and Birgit Braune and others, and you will find immense variability in the levels of Hg in wild seabirds, including some high levels.  There have been cause-effect studies, too (see Science of the Total Environment 2012  443: 775-790; Ecotoxicology 2012 21: 2143), but these are often on eggs and look at hatchability, etc.  There are far fewer studies that look at effects on adults.  A recent one in Environmental Science & Technology (2014) by Fort et al. showed lower investment in egg mass by Dovekies with high Hg levels.

Ultimately, I remain unaware of an absolute "threshold" level yet, at least for seabird liver or muscle, because seabirds seem more tolerant of Hg than other taxa.  Certainly some studies have shown high levels of Hg associated with deleterious effects on the birds, but mechanisms etc. in seabirds still need to be looked at.  Mark