SS3.17 Global Mercury Cycling: From Natural to Anthropogenic Sources
Date: Tuesday, June 11, 2002
Time: 4:30:00 PM
Location: Carson C
 
SaricaJ, Université du Québec, INRS-ETE, Sainte-foy. QC, Canada, saricajo@inrs-eau.uquebec.ca
Amyot, M, , Université du Québec, INRS-ETE, Sainte-Foy, QC, Canada, marc_amyot@inrs-eau.uquebec.ca
Hare, L, , Université du Québec, INRS-ETE, Sainte-Foy, QC, Canada, landis_hare@inrs-eau.uquebec.ca
Stanfield, L, , Ontario Ministry of Natural Resources, Glenora, Canada, les.stanfield@mnr.gov.on.ca
 
THE ROLE OF FISH CARCASSES IN HG CYCLING IN AQUATIC SYSTEMS
image
Because the concentrations of methylmercury (MeHg) increase along aquatic food chains, the majority tends to be present in fish. In spite of the importance of fish as a MeHg sink, processes involved in the recycling of MeHg following their death are little known. Here, we consider two scales of fish mortality for which the environmental consequences could be different. The first case deals with Hg released by the occasional natural mortality of fish in lakes, the impacts of which are small but sustained. In the second instance, we investigated case of massive fish mortality during the spawning of Pacific salmon, introduced in the 1970’s in an Ontario river. Our results suggest that, in both cases, total Hg concentrations of aquatic and terrestrial invertebrates feeding directly (eating carcasses) or indirectly (eating the decomposition products) on fish carcasses increased from 50% to 1500%. At the site of massive mortality, fish decomposition resulted in local increases in Hg levels of 15% in water and 175% in sediments. Fish carcasses can therefore represent an important source of Hg for aquatic and terrestrial food webs.