Freshwater Snail Emerges as a Sensitive Sentinel of Arsenic Pollution

Arsenic is one of the most persistent and worrying contaminants in the world’s freshwater systems, leaching from geological deposits, mining spoils, industrial runoff, and agricultural practices into rivers, lakes, and ponds that supply drinking water and sustain aquatic food webs. Yet while the toxicology of arsenic in fish and crustaceans has been studied extensively, freshwater gastropods—snails that sit at the base of many aquatic food chains and process enormous volumes of sediment and periphyton—have received far less mechanistic scrutiny. A new laboratory study published in the journal Ecotoxicology now provides one of the most integrated pictures to date of how a common Asian freshwater snail copes with arsenic exposure, combining survival data, antioxidant enzyme kinetics, and tissue bioaccumulation measurements into a single toxicological profile.

The research, conducted by Ji Hoon Kim, Thodhal Yoganandham Suman, Junsik Woo, and Ihn Sil Kwak of Chonnam National University and the Geosystem Research Corporation in the Republic of Korea, focused on Radix plicatula, a pulmonate snail first described by W. H. Benson in 1842. These animals are ideal candidate biomonitors: they are widespread, sedentary, easy to culture in the laboratory, and, as benthic grazers, they are in constant contact with both dissolved and particulate contaminants in the water column and on submerged surfaces. The team exposed the snails to three different arsenic concentrations over a 21-day period, tracking mortality, the activity of key antioxidant enzymes, and the amount of arsenic that accumulated in snail tissues.

The survival results told a clear and sobering story. In control tanks, 98.3 percent of snails survived the full three weeks. In the highest arsenic treatment, survival fell to 83.3 percent by day 21, with mortality increasing in a manner that was dependent on both the concentration of arsenic and the duration of exposure. This dose- and time-dependent pattern is exactly what toxicologists look for when evaluating whether a contaminant is acting in a predictable, cumulative fashion, and it confirms that even sublethal concentrations of arsenic impose measurable physiological costs on these animals over ecologically relevant timescales.

Perhaps the most biologically revealing findings came from the antioxidant enzyme measurements. When aquatic animals are exposed to arsenic, the metalloid triggers the generation of reactive oxygen species—highly reactive molecules that damage lipids, proteins, and DNA. Cells respond by ramping up enzymatic defenses, chief among them superoxide dismutase (SOD), which converts superoxide radicals into hydrogen peroxide, and catalase (CAT), which then breaks hydrogen peroxide down into water and oxygen. In the exposed snails, these two enzymes displayed what the researchers describe as biphasic responses. Catalase activity peaked early, on day 7, and then declined as the exposure continued. Superoxide dismutase followed a different trajectory, peaking on day 14 at a striking four times the activity measured in control animals before subsiding.

This temporal separation between the two enzymes is more than a curiosity; it offers a mechanistic window into how the snails’ defenses are overwhelmed. The early catalase surge suggests an initial attempt to neutralize peroxide produced by arsenic-induced oxidative stress, while the later SOD peak indicates that the front line of radical detoxification continued to be mobilized well into the exposure period. The eventual decline of both enzymes hints at either regulatory exhaustion or damage to the enzymatic machinery itself as arsenic accumulated—a pattern ecotoxicologists associate with the transition from a compensatory stress response to overt physiological impairment. Staggered enzyme kinetics of this kind, the authors argue, can serve as a sensitive early-warning signal of contaminant stress long before mortality becomes apparent.

The bioaccumulation data were equally telling. Tissue arsenic concentrations in the snails rose in a strongly dose-dependent manner, and the relationship between water concentration and body burden was highly linear, with coefficient of determination values ranging from 0.85 to 0.97. Such tight linearity means that the snails’ tissues effectively function as an integrated chemical record of the arsenic they have encountered, making them a reliable passive archive of contamination history. Even more significant was the effect of time: the biota-sediment accumulation factor, or BSAF, shifted from values at or below 1 at the start of the exposure to values of 2 or greater as the experiment progressed. In practical terms, this means that with prolonged exposure, the snails were concentrating arsenic in their tissues to levels well above those in their surroundings, intensifying the risk that the metalloid will move up the food web.

That last point matters because snails are eaten by fish, birds, and other predators, and arsenic accumulated in gastropod tissue can therefore enter and travel through aquatic food chains. Previous work on other freshwater snails, including the apple snail Pomacea canaliculata and the lymnaeid Lymnaea stagnalis, has documented arsenic and cyanobacterial toxin accumulation and its consequences for reproduction and life history. The new study extends this picture to Radix plicatula and adds quantitative toxicokinetic evidence that bioaccumulation is not a static endpoint but a process that accelerates as exposure lengthens—a critical consideration for ecosystems subjected to chronic, low-level contamination rather than acute spills.

One of the study’s most methodologically interesting components was the use of diffusive gradients in thin films, or DGT, an in situ sampling technique that measures the fraction of a contaminant in water that is truly available for biological uptake rather than simply its total concentration. DGT devices accumulate labile arsenic on a binding layer at a rate governed by diffusion, giving a time-weighted average of bioavailable concentration. In this experiment, DGT measurements correlated strongly with the arsenic concentrations measured in snail tissue, yielding a coefficient of determination of 0.71. That level of agreement, the authors note, confirms DGT as a reliable indicator of arsenic bioavailability—a valuable tool for environmental agencies that need to assess ecological risk from water chemistry data without waiting for biological responses to appear.

Taken together, the findings position Radix plicatula as a sensitive and mechanistically well-characterized bioindicator of arsenic contamination in freshwater ecosystems. A good bioindicator must satisfy several criteria simultaneously: it must accumulate the contaminant predictably, it must show measurable sublethal responses at environmentally relevant exposures, and it must be robust enough to interpret across sites and seasons. This study demonstrates that the snail meets all three, with survival, enzyme activity, and tissue burden each providing complementary information about the severity and duration of contamination. The integrated approach—linking organismal survival, molecular defense responses, and chemical bioaccumulation with an independent bioavailability measurement—represents a template for how modern ecotoxicology can move beyond single-endpoint tests toward a mechanistic understanding of contaminant toxicity.

For regulators and conservation biologists, the implications are concrete. Because antioxidant enzyme responses appeared within the first week of exposure, these biomarkers could be deployed to detect arsenic stress in field populations before population-level declines occur. Because tissue accumulation increased linearly with exposure concentration and intensified over time, snail body burdens could serve as a cost-effective monitoring metric for chronic contamination. And because DGT measurements tracked tissue concentrations closely, water-based monitoring programs could combine chemical and biological indicators in a single assessment framework. As arsenic contamination continues to threaten freshwater resources across South and East Asia and beyond, studies like this one show that some of the most effective sentinels of environmental harm may be quietly grazing on the streambeds beneath our feet.

Subject of Research: Arsenic toxicity, antioxidant responses, and bioaccumulation in the freshwater snail Radix plicatula

Article Title: Survival, antioxidant enzyme activities, and bioaccumulation response in freshwater snail Radix plicatula (W. H. Benson, 1842) to arsenic

Article References: Kim, J. H., Suman, T. Y., Woo, J., & Kwak, I. S. (2026). Survival, antioxidant enzyme activities, and bioaccumulation response in freshwater snail Radix plicatula (W. H. Benson, 1842) to arsenic. Ecotoxicology, 35(8), Article 171. https://doi.org/10.1007/s10646-026-03151-3

Image Credits: AI Generated

DOI: 10.1007/s10646-026-03151-3

Keywords: arsenic, bioaccumulation, freshwater gastropods, antioxidant enzymes, Radix plicatula, environmental biomonitoring, ecotoxicology, oxidative stress, DGT, biota-sediment accumulation factor, water pollution, bioindicator