Using Sponges to Monitor Long-term Pollution

Phoebe Zito (right), assistant professor of chemistry at the University of New Orleans, and Tamieka Palmer, a former undergraduate student at Baton Rouge Community College, collect sponge tissue for heavy metal analysis at Big Lake in New Orleans City Park.

Heavy metals are widespread contaminants in aquatic systems. However, their prevalence and the threat they pose to local ecosystems are not easy to monitor.

In a Louisiana Sea Grant-funded project, Stephanie Archer, assistant professor at Louisiana Universities Marine Consortium (LUMCON); Mary Miller, professor of biology at Baton Rouge Community College (BRCC); and Phoebe Zito, assistant professor at the University of New Orleans (UNO), looked at freshwater sponges as an indicator species for environmental heavy metal concentrations. Freshwater sponges are widespread filter feeders that remove up to 90 percent of the bacteria and viruses from the water they inhabit.

After analyzing 60 sponges from 45 sites, along with water and sediment samples from the same locations, the researchers discovered that more than half of the sponge samples exhibited detectable levels of heavy metals, such as aluminum, arsenic, cadmium, chromium, copper, nickel, lead and zinc. Notably, the sponges often exhibited significantly higher concentrations of heavy metals compared to the water samples, while concentrations in sediments were comparable.

“The initial results of this study suggests that sponges serve not only as effective bio-indicators but also as valuable tools for monitoring long-term pollution in freshwater ecosystems,” stated Archer. “The elevated heavy metal levels detected in sponge tissue, particularly in comparison to surrounding water, underscores their remarkable sampling capabilities.”

The research team employed Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to quantify heavy metals in water, sponge tissue and sediment samples. A specific focus was placed on Ephydatia fluviatilis, the most commonly collected sponge in the study, providing insights into species-specific bio-accumulation patterns. A strong positive correlation was observed between heavy metal levels in water and those in E. fluviatilis, particularly for metals such as copper and lead.

Genetic analysis is currently underway for unidentified sponges, as some were challenging to identify due to the absence of gemmosclere spicules — essential microscopic characteristics required for definitive species identification.

One undergraduate-led project within this study investigated the presence of mercury in sponge tissue, although results are incomplete as of this writing. Furthermore, researchers observed malformed sponge structures potentially associated with heavy metal exposure — an area that necessitates further investigation.

Project findings will be shared at the upcoming 2025 World Sponge Community Conference, where the team will present new insights into bio-concentration factors and species-specific heavy metal accumulation.