Invasive alien species have the potential to alter biodiversity and ecosystem processes. In freshwaters, detritus decomposition is a major ecosystem service but it remains uncertain whether invasive alien decapods process detritus differently to natives. This study examined leaf litter processing, and cascading effects on biofilms, by the European native white clawed crayfish (Austropotamobius pallipes) compared to two invasive alien decapod species: the American signal crayfish (Pacifastacus leniusculus) and the Chinese mitten crab (Eriocheir sinensis). Invasive alien decapods were responsible for higher leaf litter decomposition than the native. In comparison with native crayfish, invasive alien crab and crayfish showed higher rates of litter consumption, increased production of smaller leaf fragments, fine particulate organic matter (FPOM) and dissolved organic carbon. Nutrients (ammonia and soluble reactive phosphorous) derived from excretion (measured separately in the absence of biofilms) varied among decapod species, being lower for P. leniusculus. However, nutrient concentrations did not vary among species in the detritivory experiments with biofilm, implying nutrients were utilised for biofilm production and respiration as no differences in biomass were evident among decapod treatments. These results show invasive alien decapods have the potential to increase the magnitude of detrital processing to FPOM in rivers, but indirect impacts on primary producers due to nutrient release are uncertain based on this experimental context.
suggest that cercarial predation effects on disease risks will depend on the specific species 32 composition of ambient communities and not on non-host biodiversity per se.
Marine parasites such as trematodes often compromise the fitness of their hosts. Such effects are generally considered to be density-dependent, i.e. the greater the infection intensity in the host, the greater the detrimental impact on host fitness. However, the mechanisms determining infection in marine hosts are still poorly understood. Here, we investigated the effect of cercarial dose and exposure frequency (single vs. trickle infections) of a marine trematode parasite, Himasthla elongata (Trematoda: Echinostomatidae), on infection intensity and success in its second intermediate host, the blue mussel Mytilus edulis, an abundant and widely distributed bivalve in European coastal waters. In our laboratory experiment, we tested 4 levels of parasite doses and showed that mussels faced higher parasite infection intensity at higher doses of cercarial exposure and that they acquired more infections when repeatedly exposed to smaller doses compared to a single high dose. However, the infection success of cercariae did not differ among 4 dose levels but was only significantly different between trickle and single exposures. This indicates that cercariae were not subjected to a dose-dependent regulation of their infectivity, suggesting that infection intensity in mussels is largely driven by factors mediating the abundance of infective stages. With the combined investigation of the effect of cercarial dose and exposure frequency at realistic dose levels, our study contributes to our currently very limited understanding of the determinants of infection intensity in marine hosts and highlights the usefulness of experimental studies in advancing our knowledge in this field.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.