Nature’s Ancient Water Filters Show Remarkable Potential Against Toxic Metal Pollution

The discovery could have major implications for environmental monitoring and restoration strategies across India’s heavily polluted river systems.

Freshwater sponges—some of the earliest multicellular organisms on Earth—are emerging as powerful natural allies in combating water pollution. Known for filtering vast quantities of water and sustaining healthy aquatic ecosystems, these primitive organisms are now gaining scientific attention for an even more significant ecological service: bioaccumulation and bioremediation of toxic metals.

A recent study published in Microbiology Spectrum (American Society for Microbiology) by researchers from the Bose Institute, an autonomous organisation under the Department of Science and Technology (DST), Government of India, has revealed that freshwater sponges from the Sundarban delta possess exceptional capabilities to serve as bioindicators of metal pollution and absorbents of toxic contaminants such as arsenic, lead and cadmium.

The discovery could have major implications for environmental monitoring and restoration strategies across India’s heavily polluted river systems.

How Sponges and Their Microbes Detoxify Polluted Waters

The study, led by Dr. Abhrajyoti Ghosh of the Department of Biological Sciences, explored how the sponge–microbe consortium functions in dynamic estuarine environments. Using sponge samples collected in situ, scientists examined both metal accumulation in sponge tissues and the diversity of bacterial communities living symbiotically within them.

Their analysis revealed:

• Sponge tissues accumulated significantly higher concentrations of toxic metals compared to surrounding water.

• Bacterial communities associated with sponges were distinct, highly diverse and shaped by species and habitat conditions.

• Many of these bacteria carry genes involved in metal ion transport, heavy-metal resistance, mobilisation, and antimicrobial resistance, allowing them to thrive in polluted waters while facilitating detoxification.

These findings confirm that sponges are not passive absorbers—they operate as active biological systems, where microbes and host tissues together detoxify and cycle metals, improving overall water quality.

First Assessment of Freshwater Sponge Microbial Diversity in the Sundarbans

Supported by the DST-SERB National Post-Doctoral Fellowship awarded to Dr. Dhruba Bhattacharya, this is the first study to document bacterial diversity in Sundarban freshwater sponges. The region, better known for its mangroves and estuarine biodiversity, has remained largely unexplored with respect to freshwater sponge ecology.

The research highlights the ecological significance of these organisms in a region experiencing intensifying anthropogenic pressures, including agricultural runoff, industrial discharges and sediment-bound pollutants.

Promise for Bioremediation in the Gangetic Plain

Given the high levels of heavy metal contamination reported across the Gangetic basin, the ability of freshwater sponges to sequester metals like arsenic, cadmium and lead offers a promising pathway for:

• Bioremediation of polluted rivers and wetlands,

• Environmental monitoring, using sponges as natural indicators of water quality,

• Understanding microbial resilience in harsh environmental conditions,

• Designing nature-based solutions for restoring contaminated ecosystems.

Their natural filtering activity, combined with microbial symbionts that detoxify their surroundings, positions freshwater sponges as a cost-effective, sustainable and scalable tool for ecological restoration.

A Breakthrough for Sustainable Water Management Research

The study marks a milestone in understanding the ecological roles of sponge-associated microbes and expands scientific knowledge on freshwater sponge biology in India. Beyond identifying species-level adaptations, the research opens doors to:

• Harnessing sponge-microbe systems for targeted bioremediation projects

• Developing early-warning pollution detection systems

• Integrating natural biofilters into community-level water treatment strategies

This pioneering work contributes to global efforts aimed at developing nature-based, low-energy solutions for water purification in an era of escalating environmental challenges.