An international team of scientists reports that a bacterial group is driving disease and mass die-offs of sea sponges in the Mediterranean. They warn of an epidemic pattern linked to warming ocean waters, triggering cascading disruptions across marine ecosystems.
Sea sponges, much like corals, are considered habitat engineers. Their presence and biological activity help create habitats for a wide range of species. When this habitat is degraded, many organisms may perish or migrate away in search of healthier environments.
Researchers from Spain and Turkey identify a group of bacteria, Vibrio, as the culprits behind sponge disease and mortality. These bacteria live as free-swimming organisms or form symbiotic relationships with fishes, crustaceans, and corals. The findings are published today in Frontiers in Microbiology (Citation: Frontiers in Microbiology).
The presence of Vibrio bacteria has previously been linked to bleaching in tropical and subtropical corals worldwide. Scientists have detected these pathogens in various diseased crustacean species and suspect that the same agents may have contributed to mass die-offs of stony corals in shallow waters of the northern Aegean Sea (Citation: Frontiers in Microbiology).
Many benefits of sponges
Ezgi Dinçtürk from İzmir Katip Çelebi University cautions about climate change effects on marine ecosystems and explains that healthy sponges improve light penetration, enhance water quality, absorb and release inorganic nutrients, and provide shelter for a broad range of organisms. In short, disease and epidemics carry heavy consequences for the sea (Citation: İzmir Katip Çelebi University).
Manuel Maldonado, a scientist with the Sponge Ecobiology and Biotechnology group at the Blanes Centre for Advanced Studies, notes that these Vibrio bacteria are related to cholera-causing bacteria in humans and can trigger epidemics with high mortality. Sponges and corals are described as habitat engineers due to their foundational role in reef and coastal ecosystems (Citation: CEAB-CSIC).
The study highlights that water quality is higher in regions with abundant sponges, where light-loving organisms such as Posidonia and corals also flourish. When conditions deteriorate, those key species suffer, leading to a cascade of effects that are difficult to predict and measure (Citation: CEAB-CSIC).
The researchers remind readers that epidemic deaths in sponges have been observed for over a century, with some outbreaks affecting traditional bath sponge industries in the Greek and Caribbean regions. The current trend shows an acceleration tied to heat waves and ocean warming (Citation: CEAB-CSIC).
Although significant die-offs have occurred in various seas, the Mediterranean appears especially vulnerable due to its relatively enclosed nature and extensive scientific attention. Epidemic-related deaths were detected earlier there, and their consequences are being studied in greater detail (Citation: CEAB-CSIC).
Manuel Maldonado explains that the core aim of this research is not simply to quantify sponge mortality in the Mediterranean but to identify the Vibrio bacteria involved in the disease, examine their growth, and assess their capacity to harm other organisms under warming conditions (Citation: CEAB-CSIC).
The researcher notes that sponges were among the earliest animals on Earth, and their genomes hold critical information for understanding later animal diversification and the evolution of organ systems, including humans. This underlines their biotechnological importance and potential in fields such as biomaterials and natural products (Citation: CEAB-CSIC).