Research Activities

Generation and Field-Validation of Chronic Biotic Ligand Models for Fish

Collaborators

Current summary: Biotic ligand modelling (BLM) has shown great promise for predicting metal toxicity in aquatic animals. However, most BLM development has been conducted under tightly-controlled laboratory conditions and acute metal-exposure scenarios that are unlikely to exist in nature. The primary objective of MITHE Project A1 is to develop chronic BLMs in wild fishes inhabiting soft, sensitive waters typical of the Canadian Shield in order to improve the ecological relevance of ecological risk assessments. To do this, we are taking a three-pronged approach by studying metal dynamics at three distinct biotic ligands: (i) gill epithelium, (ii) gut epithelium, and (iii) olfactory epithelium. Most BLM development has focused on metal dynamics at the gill, which represents the benchmark against which gut and olfactory epithelium models will be compared. The gut represents a major site for metal uptake that has, until recently, been largely ignored by gill-based BLMs. Consequently, if BLMs are to predict metal effects in wild fishes, all major uptake pathways must be considered. Moreover, metal binding to the olfactory epithelium results in chemosensory impairment, which could lead to large-scale ecological effects. Together, knowledge of metal dynamics at binding epithelia coupled to ecologically-relevant effects will allow us to make meaningful predictions about metal effects in aquatic ecosystems.

Summary Archive: Current | 2007 | 2006

 

Project Metadata

Study/Sampling Design

We collect yellow perch (YP) from contaminated lakes in Sudbury, ON and from reference lakes in North Bay, ON. Using in vitro gut bag assays developed in rainbow trout we can validate metal uptake via the gut in wild-caught yellow perch. Gut bags will be exposed to a range of metal (radio-labeled) concentrations using normal intestinal saline to determine basic binding and transport constants (affinity, capacity, rates). We will then determine the effects of manipulating pH, HCO3/CO3, intestinal fluid ions, and natural organic matter (NOM) levels (most common variables in the intestinal fluids and diets of fish) on metal uptake. We will also evaluate whether wild metal-impacted YP regulate their metal uptake process in the gut to reduce metal accumulation and toxicity, a phenomenon observed in the gill

Chronic impacts of Ni and Pb will employ controlled laboratory exposures on rainbow trout as a model species. Fish will be chronically exposed to metals, both via water and diet in flow-through exposure systems in standard lab water. Field studies examining the influence of water quality, metal exposure concentrations, feeding rates, etc. will be incorporated into the design of our experiments to facilitate lab-to-field extrapolation. Here, we will employ a screening level approach and measure a variety of physiological and biochemical parameters such as gill and gut metal binding characteristics, metal burdens, energy stores, tissue and plasma electrolytes, swim performance, metabolic capacity etc. in order to identify sensitive chronic endpoints. Differences in tissue-specific metal partitioning between waterborne and dietary metal exposures will be analyzed to develop strategies for source identification of metal exposures.

We examine the effects of chronic metal exposure on chemosensory ability by collecting yellow perch and fathead minnows from clean and contaminated lakes. We employ an integrative approach incorporating physiology, neurobiology and behavioural assays to assess effects of metal contamination on olfaction. Utilizing in vivo techniques developed for the gill we compare the binding affinity and capacity of metals at the olfactory epithelium (OE) at environmentally relevant concentrations for BLM development. We then determine how metals influence the ability of fish to detect ecologically relevant chemical stimuli, e.g., alarm cues by measuring the neurophysiological activity at the OE. In addition we determine the neuron density at both the OE and olfactory bulb to assess whether metals induce changes in cell numbers in the olfactory system. Lastly, we examine the behaviour of fishes from clean and contaminated lakes. This integrative approach is being used to develop a chemosensory based BLM that can be incorporated into ERA strategies.

Number of projects providing material for study: 0

Location of Field Site(s)
North Bay:
James Lake - 46° 17’ N, 78° 59’W
Trout Lake - 46° 18’ N, 79° 18’W

Sudbury:
Hannah Lake - 46° 26’ N, 81° 02’W
Ramsey Lake - 46° 29’ N, 80° 57’ W
Silver Lake - 46° 25’ N, 81° 00’ 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
Yellow perch, Perca flavescens
Fathead minnows, Pimephales promelas

Metals, etc. Quantified
Cu, Cd, Zn, Ni and Pb

Biological Endpoint(s)

1. Binding affinity and capacity of metals to gill, gut and olfactory epithelium
2. Integrated extracellular field potential at the olfactory epithelium
3. Behavioural responses e.g., antipredator behaviour
4. Neuron counts at the olfactory rosette and bulb

Physical Material(s) Studied

Medium/Media
Water

Metals, etc. Quantified
Cu, Cd, Zn, Ni and Pb in gill, gut and olfactory epithelium

Bibliographic References on-file with Secretariat: Yes

Data Available: Yes

Data Archived with MITHE-SN: No