Combining metal and stable isotope analyses to disentangle contaminant transfer in a freshwater community dominated by alien species

Metal accumulation in relation to size and body condition in an all-alien species community

“…It should also be noted that the Fulton factor is correlated with the body fat content (Schloesser and Fabrizio 2017), which can vary between individuals and species, and that metal accumulation can be positively or Table 1 Results of the significant linear models with log 10 -transformed metal concentration as response variable and length (CTL, cephalothorax length for crayfish; TL, total length for fish) and Fulton factor (K) as predictors Asterisks refer to the significance level: p < 0.05 (*); p < 0.01 (**); p < 0.001 (***) negatively related to the lipid content, depending on the metal (Sassd 2011;Charette et al 2021). Interspecific (as well as intraspecific, among tissues) differences in metal accumulation compared with the environmental concentrations and biomagnification processes in the Arno River community were disentangled in a recent study by Balzani et al (2021). Nonetheless, by comparing intraspecific relationships, additional information on interspecific patterns can be derived.…”

“…The absence of clear patterns is likely due to fish belonging to the same age class (adults) except for I. punctatus, for which comparable concentrations in both young and old animals were found. This latter result could be due to different reasons: the young for higher metabolism and ingestion rate, the old for the longer exposure to pollutants (Yi and Zhang 2012;Liu et al 2015;Jia et al 2017), and for predators, the greater consumption of contaminated prey from higher trophic levels (Balzani et al 2021). Moreover, the variability we identified in the sign of metal-size relationships is also in line with other studies (Jezierska and Witeska 2001;Dragun et al 2016;Jia et al 2017).…”

“…Second, the relationship between Mg and total length was found to be significant for adult specimens. These observations could be due to ontogenetic differences in habitat use, behavior, and diet (Haubrock et al 2018(Haubrock et al , 2020(Haubrock et al , 2021b that are reflected in different metal accumulations (Balzani et al 2021). Indeed, I. punctatus juveniles live close to the riverbank and feed more on detritus, while adults live on the bottom and feed in the whole water column (Endo et al 2015;Haubrock et al 2020), possibly leading to Cr bioaccumulation in young individuals and a reduction with age in Mg concentrations in adults.…”

“…Therefore, as organisms grow, it can be expected that larger (i.e., older) individuals have accumulated higher metal concentrations than smaller (i.e., younger) ones. Another factor potentially affecting metal bioaccumulation is the species richness and biomass of the recipient environment (McKinley and Johnston 2010); as prey-rich ecosystems typically have more diverse pathways, metals can more easily transfer along the food chain (Balzani et al 2021). As such, it can be assumed that generalist predators relying on multiple prey species with diverse metal accumulation levels will express higher accumulation variability depending on the food web complexity, while at the same time differing from specialized consumers (Yevtushenko 1998).…”

“…Thus far, little is known on how metals accumulate within alien species assemblages and how this may be affected by intraspecific characteristics (Balzani et al 2021). Since alien species can generally tolerate higher pollutant concentrations than native species (El Haj et al 2019), studying the sublethal effects on their fitness is an interesting avenue of research.…”