Short-term effects of the heavy metals, silver and copper, on polyps of the common jellyfish, Aurelia aurita

Heavy metals are prominent in the coastal marine environment, especially copper due to its use in anti-fouling paints and, increasingly, silver due to its use in manufacturing processes and hygiene products. Aurelia aurita is a common and widespread species of scyphozoan jellyfish found in many coastal habitats, including those impacted by human activities. While A. aurita is known to be highly tolerant of a wide range of environmental conditions including large variations in temperature, salinity and dissolved oxygen, nothing is known about its tolerance to heavy metal pollution. This study examined the independent and interactive effects of copper and silver on aspects of polyp condition including budding, strobilation, deformities and mortality. The results show that 200 μg Cu l− 1 is above the polyps' tolerance for this metal and leads to rapid mortality. When this treatment was excluded, silver had the greatest impact on polyp condition. All metals generally had a greater impact on polyp condition at higher concentrations. Combination treatments had a lesser effect than single-metal treatments, suggesting an antagonistic relationship. Copper reduced the detrimental impacts of silver when present at a high enough concentration. Despite reactions to the metals, mortality and deformity responses generally diminished over time. With budding being proportionally higher than mortality, and increasing over time, it is suggested that sub-lethal concentrations of metals could actually lead to population growth over time by the process of hormesis.