Ecotoxicology

Mercury uptake in benthic organisms

 Thanks to a “Best in Science” grant from the Ministry of the Environment,  Roxanne Razavi, a Masters student from Queen’s University, is working at the River Institute to test the relationship between gaseous bubbling and mercury uptake in native mussels (Elliptio complanata), invertebrates, and fish (yellow perch).  In this research project, aquatic species are placed in cages in areas of the river where high levels of gaseous bubbling were previously observed.  Gas collectors placed in these areas will sample gaseous output from the sediments.  After an appropriate time period, the species will be removed from the river and sent to the laboratory for tissue mercury analysis.   Phytoplankton species are also being sampled in these areas to assess the impact of gas bubbling on mercury uptake in plant species.

 This study will give information about exposure and uptake of mercury in aquatic organisms, and will determine whether increased gas bubbling is related to the high mercury concentrations that have been found in aquatic biota in the St. Lawrence River.   

SMART (Sources of Mercury Accumulating in Rivers and Tributaries) 

 Project SMART is a major collaborative research project that traces the sources and movement of mercury in the aquatic food chain.  Now in its third year, the study involves intricate sampling and analysis of total mercury and methyl mercury in sediments, water, and the atmosphere, as well as in zooplankton, fish, and fish predators in the St. Lawrence River.  In 2005, three large collectors were deployed underwater in the St. Lawrence River to sample and trap gas bubbles in target areas.  Results suggest that gases generated from the degradation of sediments, wood chips, and organic debris on the river floor act as a transport mechanism for volatile forms of mercury.

 This extensive project is funded by a grant from NSERC (Natural Sciences and Engineering Research Council of Canada), with support from Environment Canada, the Ontario Ministry of the Environment, and the Ontario Ministry of Natural Resources.  A team of scientists and students from the St. Lawrence River Institute, Ottawa University, Queen’s University, Environment Canada, and the Canadian Wildlife Service are working together on this project, led by Dr. David Lean from the University of Ottawa.  Dr. Jeff Ridal, Dr. Brian Hickey, Bruce Doran, and a team of students are the participating investigators from the River Institute. 

 Mercury bioavailability and uptake in fish

 To study mercury uptake in fish, several species of fish and predatory walleye were targeted at three contaminated zones along the Cornwall waterfront.  Radio-telemetry methods are being used to study the movement and location of local fish species. Further examination of stomach contents and muscle samples of perch, walleye, and other predators gives details about mercury exposure and the accumulation of mercury in the food chain.

 Elizabeth Yanch,  a Masters student from Queen’s University, is working on this project to determine feeding patterns and mercury exposure in fish.  This research will continue to define the sources and exposures of mercury, and to examine the toxicological effects of mercury on fish and bird species. 

 Bat Toxicology

 In a previous study, it was discovered that local species of bats captured at several locations in Eastern Ontario and Western Quebec had concentrations of mercury in the fur that approached or exceeded the threshold for detrimental effects in humans (Hickey et.al., 2001).  These results prompted the initiation of a new bat study by Dr. Brian Hickey and Idalia Milan, (Masters student from Royal Roads University in British Columbia), to study mercury toxicity in bats, and determine how bats are affected by biomagnification of mercury in the food chain.

The study involves several sampling parameters: capturing and radio-tagging bats to identify their feeding zones; sampling insects from these feeding areas to determine mercury concentrations; and collecting fur samples from bats for mercury analysis.  Dr. Hickey hopes to establish a link between mercury levels in the fur of bats and the mercury concentrations in the insect population.  Further study will determine whether the mercury concentrations in the fur samples are related to mercury concentrations in organ tissues such as the liver, and whether the bats demonstrate any toxicological effects related to mercury exposure.  These conclusions will then be correlated to other aspects of the SMART project, including the study of mercury in river sediments where insect larvae develop.  

Mosquito ecology relating to West Nile Virus

 In 2003, the appearance of West Nile Virus in Canada prompted provincial Ministries of Health to initiate a Mosquito Monitoring Program throughout Canada.  In Ontario, local Health Units were encouraged to develop a program to study mosquito patterns and test for the West Nile Virus.  Entomologist Bruce Doran of the St. Lawrence River Institute has been involved with this project since its inception.  In collaboration with the Eastern Ontario Health Unit, Bruce has developed and supervised an ongoing study to determine the spatial and temporal distribution of mosquito species in Eastern Ontario. 

 For three years, larvae and adult mosquito species were collected and examined to determine the rate of occurrence of species that are capable of carrying the West Nile Virus.  Results showed that mosquito larvae are not evenly distributed throughout Eastern Ontario (i.e. some municipalities have higher larval densities than others).  Although all of the larvae and adult mosquitoes collected were potential carriers of West Nile Virus, none of the mosquitoes tested were found positive for the virus.

Now that the reproductive zones have been identified, monitoring for West Nile Virus continues in adult mosquitoes in Eastern Ontario. Bruce Doran and his team have placed traps throughout the area, and adult mosquitoes are collected weekly from May to September. 

If you would like to know more about our research program, please contact Dr. Jeffery Ridal - jridal( at) riverinstitute.ca or Dr. Brian Hickey - bhickey(at)riverinstitute.ca