The isopod Eurydice spinigera and the chaetognath Flaccisagitta enflata: How habitat affects bioaccumulation of metals in predaceous marine invertebrates

We analyzed the concentrations of 20 trace elements in Eurydice spinigera (Isopoda) and Flaccisagitta enflata (Chaetognatha), which represent a hyperbenthic and a zooplanktonic marine species respectively, sharing the same predaceous feeding strategy, from a highly productive coastal region (Ligurian Sea, Northwestern Mediterranean). The same elements were also quantified in marine sediments, where geological anomalies were found for arsenic, chromium and nickel. Metal transfer seems to be deeply influenced by different habitats. The carnivorous isopod E. spinigera, which spends most of its lifetime on the seabed, was found to have the highest concentrations of most trace elements, such as Al, As, Cd, Ce, Cr, Fe, La, Mn, Ni, Pb, Se, V and Zn, and consequently have the highest bioaccumulation factors (BAFs). Moreover, the estimation of biota sediment accumulation factors (BSAFs) revealed that cadmium, copper and zinc concentrations were higher in the isopod than in the sediment. Conversely, in the carnivorous chaetognath F. enflata, which is not a benthonic species, the highest levels of copper and tin were found. Moreover, arsenic speciation analysis confirmed the presence of inorganic As (III + V) in E. spinigera. In the context of utilizing a marine organism as a bio-indicator of metal transfer, it is crucial to consider both feeding behavior and feeding habitat.