Invasive or Biomonitoring Species? Use of Pomacea maculata Operculum as a Tool to Determine Metal Pollutants: a Micro-PIXE Investigation

Pomacea maculata is a widely distributed agricultural and environmental pest in Asia. It is also causing ecological damage and threatening human health in the Southeastern United States. However, its limited mobility and fast consumption of aquatic vegetation may make it an excellent biomonitor to evaluate the pollution status of freshwater coastal ecosystems. This work investigated the capability of the operculum of this snail to accumulate toxic metals in a laboratory environment. We measured the elemental composition of the nucleus and edge regions on the varnish layer of the operculum by employing a MeV ion microprobe instrument. Iron, copper, and zinc were present in the operculum at trace levels. Copper was present at elevated levels in the operculum of snails exposed to copper for 2 weeks. Additionally, heterogeneity in the distribution of major and trace elements within the gastropod’s operculum was revealed by 2D elemental images obtained using microparticle-induced X-ray emission spectrometry. On average, the nucleus of the operculum showed a higher accumulation of copper than did the edge. These results demonstrate that micro-PIXE can be used to look at the within-tissue distribution of toxic metals in hard tissues like a snail’s operculum. We propose that the operculum metal concentrations can be used as a bioindicator capable of providing information on the ecosystem’s health and potentially reveal temporal changes in this health.