Research Activities

Multiple metal interactions with fish gills and organic matter

Collaborators

Current summary: Metal loads in contaminated waters are seldom a single metal, but usually a mixture of many metals arising from mining, industrial, or municipal inputs. Using models such as the Biotic Ligand Model (BLM), predictions can be made about the relative strength with which individual metals bind to the gill, how such binding is influenced by water chemistry, and ultimately how such metal binding affects fish health and survival. However, the BLM presently has limited applications for multiple metal mixtures. Our research goals are to: (i) develop and validate a model that predicts how mixtures of Cd, Pb and/or Zn bind to the fish gill; (ii) determine how the complexation of metals by natural organic matter (NOM) influences the fish gill and toxicity when fish are exposed to multi-metal mixtures; and (iii) confirm that observed gill-metal binding is predictive of compromised fish health and survival when fish are exposed to metal mixtures at environmentally relevant concentrations. To simulate the sensitive, NOM-rich waters of the Canadian Shield, our experiments take place in waters of low ionic strength and hardness, to which different concentrations of NOM are added. Our model organism is the rainbow trout (Oncorhynchus mykiss) because we have an in depth understanding of gill function and metal toxicity in this traditional test animal. By comparing the physiological and toxic responses of rainbow trout to environmentally relevant metal mixtures to those of potentially more sensitive fishes (e.g. artic char, brook trout, northern pike) native to Canadian Shield lakes, it will be possible draft realistic and effective guidelines for metal contaminants that are not overly stringent or permissive. This will therefore allow scarce resources to be diverted to other areas of social, economic or environmental importance to Canadians.

Summary Archive: Current | 2007 | 2006

 

Project Metadata

Study/Sampling Design

Metal loads in contaminated environments are seldom single metals, but usually a mixture of metals arising from mining, industrial or municipal sources. Our experiments take place in waters of low pH (pH 6.0), and low ionic strength to simulate the acidic, soft waters found in the Canadian Shield. The model organism for this work is the rainbow trout (Oncorhynchus mykiss) because we have an in depth understanding of gill function and metal toxicity in this traditional test animal. The metals of interest for our work are Cd, Pb and Zn, which are common environmental contaminants having similar toxic mechanisms of action. Our basic method is to use toxicological modeling (e.g., the Biotic Ligand Model) to determine the relative strength by which different metals bind to the gill. Using this information, we predict how much Cd, Pb and/or Zn will be bound to the gills when fish are exposed to mixtures containing these metals. To validate our predictions, the fish are then exposed to the metal mixtures, and gill-metal accumulation and toxicity is measured. A similar approach is then used to determine how different concentrations and types of natural organic matter (NOM) influence metal binding to the gill. The dilute soft water lakes of the Canadian Shield generally have an abundance of NOM, which may protect fishes from metal toxicity. To confirm that our observations are predictive of toxicity, physiological parameters, such as internal electrolyte concentrations, and rates of electrolyte uptake and loss across the gill, are measured to determine if metal accumulation on the gill is linked to compromised fish health and survival. In the longer-term, the toxic responses of the rainbow trout to these metal mixtures will be used as a reference to assess the impact that metal mixtures have on the health of potentially more metal-sensitive fish species (e.g., artic char, brook trout and northern pike) that are native to lakes of the Canadian Shield.

Number of projects providing material for study: 0

Location of Field Site(s)
Natural organic matter (NOM) collected from Luther Marsh, Grand Valley, Ontario
(43° 54.3’ N; 80° 24.5’ W)

Human Studies

Outcome or Process Studied
--- none provided ---

Exposure Medium, and Metals/Substances Quantified
--- none provided ---

Biological Endpoint(s) Monitored
--- none provided ---

Biota Studied

Species
Rainbow trout (Oncorhynchus mykiss)

Metals, etc. Quantified
Pb, Cd, Zn and Natural Organic Matter (NOM)

Biological Endpoint(s)
(i) 96 h LC50 for Pb and Cd in trout
(ii) 3 h LA50 and 24 h LA50 (amount of new metal bound to the gill when exposed to the 96 h LC50 for a particular metal over a defined time period)

Physical Material(s) Studied

Medium/Media
Water ion (Na+, Ca2+, Cl-) concentrations, water pH and water temperature

Metals, etc. Quantified
Pb, Cd and Zn concentrations in water, blood and tissues (gill, muscle, kidney, liver, gut); concentration of Natural Organic Matter (NOM) in water

Bibliographic References on-file with Secretariat: No

Data Available: No

Data Archived with MITHE-SN: No