Monday March 24, 2025
Mollusks are often associated with ecologically harmful invasions and damaged boat engines. A laundry list of mollusks like the infamous Zebra mussel, Asian clam, and New Zealand mud snail can wreak havoc in water bodies they are not native to. However, species of the Mollusca phylum aren’t purely malevolent – in fact, some of these pocket-sized filter feeders are used by scientists as biological instruments to indicate water quality. From long-term monitoring of drinking water to studying bioremediation methods, clams, mussels, slugs, and snails can be critical research and monitoring tools.
The Mollusca phylum has been used in biomonitoring for decades and has peppered publications in the field of ecotoxicology since the 1960s. Mollusks are generally sessile, meaning they are nonmoving, and are found in a wide range of freshwater and marine environments, where they often account for the majority of aquatic biomass and occupy important ecological roles. As such wide-spread organisms with well-characterized biologies and low-maintenance lifestyles, mollusks are considered ideal for both laboratory and field studies.
These organisms exhibit telling responses to heavy metals, pesticides, and toxic organic compounds, making them highly effective biological early warning systems, much like a canary in a coal mine for aquatic toxicants. As soft-bodied invertebrates that feed by filtering water for microscopic organisms, or scraping algae and detritus from underwater surfaces, mollusks consume harmful particulates present in water which are retained and concentrated in their bodies (a process called bioaccumulation). Capitalizing on their bioaccumulating nature, scientists can analyze shell growth patterns or test organ and tissue samples to measure the concentration of certain contaminants in surrounding ecosystems.
Specifically with bivalves, scientists can attach a transducer to the animal’s shell which converts physiological responses into measurable or visible signals. Any changes occurring in the rhythmic patterns of their feeding, strength and duration of water outflow during feeding, or sudden shell closure can be measured by these devices, alerting scientists of the presence of contaminants. Such is the case for a small team of swan mussels (Anodonta cygnea) at a Polish water treatment facility that are tasked with monitoring the city’s drinking water. When pollution rises above a certain level, the mussels halt filter feeding and close their shells, triggering their transducers to record the movement and signal to engineers at the facility to shut off the water supply. In this case, the bivalves work as biosensors, providing water quality information in real-time, and they offer a cost-effective, low-maintenance water monitoring scheme.
Aside from municipal applications, mollusks can be employed as bioindicators and biomonitors, aiding in a variety of research studies. Heavy metals – including arsenic, cadmium, and zinc, among others – are toxic byproducts of fossil fuel extraction and refining that can be released into the environment and end up in natural bodies of water. Acute bladder snails (Physa acuta), an invasive species that can be found in sewer systems, were used to monitor the effectiveness of fungi for biosorption (contaminant removal) of heavy metal pollution from oil-sands mining. By analyzing antioxidant enzyme activity and the concentration of metals in snail soft tissues, the researchers successfully measured the efficacy of the bioremediation treatment. With the capacity to survive moderate pollution and bioaccumulate heavy metals in measurable quantities, even mollusks like the ‘sewage snail’ can be useful tools in advancing pollution remediation research.
As with most wide-spread and rapidly reproducing aquatic species with a propensity to end up in non-native ecosystems, it is important to remain vigilant of certain bivalves and snails as biological invaders – but on the flip side, their value in ecotoxicological research should not go unnoticed. Whether titled bio-monitors, -sensors, or -indicators, mollusks can fill dynamic roles, working alongside scientists to monitor human water supplies, predict trends in the effects of aquatic pollution, and even shape the future of pollution mitigation. In a world with increasingly vulnerable aquatic ecosystems, harnessing the utility of these organisms to understand and manage aquatic pollution is becoming evermore important.
Header Image Caption: New Zealand Mudsnails (Potamopyrgus antipodarum) are invasive species that reproduce rapidly and form thick crusts on river bed surfaces, often outcompeting other species for resources like space and food.
This post was featured in our weekly e-newsletter, the Fish Report. You can subscribe to the Fish Report here.