The harbor at Marina Palamós in Spain looks like any other busy port — boats bobbing, sailors tightening ropes, seagulls squawking overhead. But beneath the surface, scientists have discovered an unlikely ally in the fight against ocean pollution: a lumpy, beige sponge that grows on rocks and smells faintly like a wet kitchen sponge. They call it the chicken kidney sponge, and it might be nature's answer to cleaning up the world's dirtiest harbors.
Ports are among the most polluted spots in the ocean. Trash, oil, and toxic chemicals from boat paints slowly build up in the calm, enclosed waters. Ship propellers churn up sediment, and loud engine noises disrupt the communication of fish and dolphins. Cleaning up these messes has always been difficult and expensive.
Now, a team of researchers from the Center for Advanced Studies of Blanes in Spain thinks sponges might help. These simple sea creatures — relatives of corals and jellyfish — act like living water filters. A single sponge can process thousands of liters of seawater every single day, pulling out heavy metals like lead and mercury, along with harmful bacteria, viruses, and tiny particles of dirt. The cleaned water flows back out, while nutrients get recycled into the ocean food web.
The scientists wanted to find out which sponge species could survive the harsh conditions of a working harbor. Dr. Manuel Maldonado led the research team as they tested five different species off the coast of Girona, Spain. They attached 42 sponges to ceramic plates and hung them on underwater structures at Marina Palamós. Then they waited and watched.
Most of the sponges struggled. Three species gradually shrank and died within 20 to 165 days. But the chicken kidney sponge, scientifically named Chondrosia reniformis, didn't just survive — it flourished. Nearly 92 percent of these sponges were still alive after 455 days. Some even split into two connected pieces, a kind of asexual reproduction that lets them spread without needing a mate.
The researchers described the results as outstanding. Unlike many sea creatures, the chicken kidney sponge can "creep" — slowly relocating its entire body if conditions turn unfavorable, such as when neighboring organisms compete for space. This flexibility seems to be a key reason why it thrives in waters that kill other species.
The findings suggest that one day, harbors around the world might use these humble sponges as a natural cleanup crew. Divers could transplant young sponges onto artificial reefs, and the creatures would quietly filter pollutants while providing shelter for small fish, worms, and crabs. It's a low-tech solution borrowed straight from nature.
"Here we show that some sponge species have exceptional potential for use in the restoration of degraded harbor habitats," Maldonado said.
The next step is testing whether the sponges can filter pollution as effectively in a real harbor as they do in controlled tanks. If the results hold up, the humble chicken kidney sponge could become an unexpected hero in the effort to restore the health of the world's oceans.