Blobby chicken kidney sponges clean dirty water surprisingly well

Cleaning our planet’s filthy ports could one day get a boost from a creature with a very messy nickname. Meet the chicken kidney sponge, a true ecosystem engineer that could use its filter-feeding power to clean the degraded habitats in and around busy harbors. The process is detailed in a study published today in the journal Frontiers in Marine Science.

Filter feeders for filthy waters

While they’re necessary to power the global economy, ports are very dirty Oil, trash, toxins, and even invasive species can accumulate in enclosed harbors. Those organisms arriving in the fresh or saltwater contained in a ship’s ballast tanks can displace the wildlife native to a region, while dredging, sonar, and propellers cause noise pollution.

Sponge populations offer a potential natural way to clean up these dirty ports. They filter thousands of gallons of seawater per day, removing heavy metals, pathogenic bacteria, viruses, and organic particles. At the same time, this filtering recycles nutrients back into the water. This improves water quality, and also delivers energy and organic matter back into the food web. Sea sponges also provide a habitat for worms, crustaceans, and juvenile fish.

A reef of sponges

In this new study, a team in Spain tested sponges to find which one would be the most pollution-tolerant in Mediterranean ports. They used Marina Palamós, a recreational port in the province of Girona, Spain, to test five sponge species—Corticium candelabrum, Crambe crambe, Scalarispongia scalaris, Ircinia oros, and the chicken kidney sponge Chondrosia reniformis. These species are distantly related, yet have different functional and anatomical traits. Some have exoskeletons while others don’t, while others are made of different minerals, and house distinct populations of microbes within their tissue.

The team brought the sponges to Blanes Marine Research Center (also in Girona) and attached them to ceramic plates in 132-gallon tanks with unfiltered running seawater. Between 2024 and 2025, they transplanted these plates with a total of 42 sponges onto artificial reefs. The reefs were made of metal grids and coated in calcium carbonate, and were then fixed to the underwater seawall at Marina Palamós. The only species that did not make it onto the artificial reef was C. candelabrum, since they died in the laboratory.

sponges in a harbor — Three specimens of the chicken kidney sponge transplanted into the harbor. One specimen is migrating toward the edge of the experimental plate used as the substratum. During this migration, its body is undergoing division into two clonal descendants, which remain connected by a narrow bridge of tissue. *Image: Carlota Escarré.*

Chicken kidney reigns supreme

The chicken kidney sponge C. reniformis stuck out among all of the sponges tested as the best candidate for future clean-up experiments. It thrived in the port, reproduced asexually, and 91.7 percent of the original animals survived through the entire 455-day monitoring period. By comparison, C. crambe, S. scalaris, and I. oros gradually shrank and lived between 20 and 165 days before dying.

“Unlike many sponges, the chicken kidney sponge can ‘creep’ away if local conditions deteriorate—for example, when nearby organisms compete,” Dr. Manuel Maldonado, a study co-author and biologist at the Center for Advanced Studies of Blanes, said in a statement. “It can also relocate from the exposed upper surface of a rock, where it is subjected to UV radiation, polluted sediments, and predators, to sheltered crevices where these stresses are greatly reduced. It also reproduces asexually by fission: this allows populations to expand rapidly and later reproduce sexually, increasing the chances of successful fertilization.”

In future studies, the team plans to monitor sponges transported from the port over several years. They particularly want to track the communities of microbes present in the chicken kidney sponge to see if these microscopic organisms help them tolerate pollutants.