FLEXING THEIR 'MUSSELS': THE WORK OF FRESHWATER MUSSELS
Freshwater mussels are a truly diverse group of animals that come in a range of different sizes, shapes, and colours. Southern Ontario is home to 41 species alone, all of which help to maintain the environmental health and biodiversity in and around the Laurentian Great Lakes. Often nicknamed “ecosystem engineers” because of their ability to alter and create habitats, these animals help clean the water by filtering it through their siphons as they eat. Not only is the water cleaned through this process, but the organic matter they produce as a result makes more sediment along the bottom. Their shells serve as a strong surface for larval water insects to attach to while completing their life cycle, and their tissue (for the unlucky ones at least) makes a tasty snack for nearby animals.
All of these benefits make freshwater mussels an important contributor to the overall health of many aquatic ecosystems. The problem is that over the years, mussel populations have been in decline for a variety of reasons ranging from the introduction of zebra mussels to the pollution of our waterbodies. Their sensitivity to contaminants has made them good indicators of water quality but has also left them quite vulnerable when unnatural chemicals enter their habitats. One chemical of concern is Bayluscide®.
WHAT IS BAYLUSCIDE?
Bayluscide® is a pesticide currently being applied to some parts of the Great Lakes and their surrounding rivers as a method to control invasive sea lamprey populations. This eel-like animal, which latches onto fish to suck their blood, has wreaked havoc on the fishing industry and caused a decline in aquatic life in the region. The introduction of two lampricides, Bayluscide® and TFM, has become an effective way of dealing with this sea lamprey problem. Despite their success, there is growing concern over the effects of these pesticides on non-target organisms. Mussels are of specific concern because Bayluscide® was originally developed as a molluscicide to kill snails, so it’s likely that mussels will experience negative effects if they lie within the application path.
FLEXING OUR MUSCLES: OUR BAYLUSCIDE®-MUSSEL EXPERIMENTS
To better understand the risk that granular Bayluscide® poses to mussels, several of us grad students came together to perform a series of experiments with the objective of determining sensitivity across various life stages. In individual tests, we looked at three different age groups: early-metamorphose (babies), juveniles, and adults. We created a range of environmentally relevant Bayluscide® concentrations based on the application rate of the chemical in the Great Lakes and exposed mussels for 7 days, after which we assessed survivorship. Preliminary results show that life stage and mortality are correlated, as the early-metamorphose were the most susceptible to the chemical, followed by the juveniles and then the adults.
In addition to the above studies, we performed another experiment on adult washboard mussels. Scope for Growth is an experimental design that examines the physiological implications of a toxin or chemical on an organism by comparing their energy input vs the output. For our mussels, we took three different physiological measurements that were compared between mussels that were and were not exposed to Bayluscide®: clearance (feeding) rate (energy input), oxygen consumption (energy output), and absorption efficiency (energy input). Our preliminary findings suggest acute exposure to Bayluscide® has limited effects on scope for growth but did elicit behavioural changes in mussels.
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