Ecosystem services provided by the exotic bivalves Dreissena polymorpha, D. rostriformis bugensis, and Limnoperna fortunei

Tracking the micro- and nanoplastics in the terrestrial-freshwater food webs. Bivalves as sentinel species

Micro- (MPs) and nanoplastics (NPs) are currently ubiquitous in the ecosystems, and freshwater biota is still insufficiently studied to understand the global fate, transport paths, and consequences of their presence. Thus, in this study, we investigated the role of bivalves and a trophic transfer of MPs and NPs in an experimental food chain. The food chain consisted of terrestrial non-selective detritivore Dendrobaena (Eisenia) sp., freshwater benthic filter feeder Unio tumidus, and freshwater benthic detritivore-collectors Asellus aquaticus or Gammarus sp. Animals were exposed to different fluorescently labeled micro- and nanoplastics (PMMA 20 μm, nanoPS 15-18 nm, and 100 nm, PS 1 μm and 20 μm, PE from cosmetics) as well as to the faeces of animals exposed to plastics to assess their influence on the environmental transportation, availability to biota, and bioaccumulation of supplied particles. Damaged and intact fluorescent particles were observed in the faeces of terrestrial detritivores and in the droppings of aquatic filter feeders, respectively. They were also present in the guts of bivalves and of crustaceans which were fed with bivalve droppings. Bivalves (Unio tumidus, and additionally Unio pictorum, and Sphaerium corneum) produced droppings containing micro- and nanoparticles filtered from suspension and deposited them onto the tank bottom, making them available for broader feeding guilds of animals (e.g. collectors, like crustaceans). Finally, the natural ageing of PS and its morphological changes, leakage of the fluorescent labelling, and agglomeration of particles were demonstrated. That supports our hypothesis of the crucial role of the characterization of physical and chemical materials in adequately understanding the mechanisms of their interaction with biota. Microscopical methods (confocal, fluorescent, scanning electron) and Raman and FT-IR spectroscopy were used to track the particles' passage in a food web and monitor structural changes of the MPs' and NPs' surface.

Insights on the Organ-Dependent, Molecular Sexual Dimorphism in the Zebra Mussel, Dreissena polymorpha, Revealed by Ultra-High-Performance Liquid Chromatography-Tandem Mass Spectrometry Metabolomics

The zebra mussel, Dreissena polymorpha, is extensively used as a sentinel species for biosurveys of environmental contaminants in freshwater ecosystems and for ecotoxicological studies. However, its metabolome remains poorly understood, particularly in light of the potential molecular sexual dimorphism between its different tissues. From an ecotoxicological point of view, inter-sex and inter-organ differences in the metabolome suggest variability in responsiveness, which can influence the analysis and interpretation of data, particularly in the case where males and females would be analyzed indifferently. This study aimed to assess the extent to which the molecular fingerprints of functionally diverse tissues like the digestive glands, gonads, gills, and mantle of D. polymorpha can reveal tissue-specific molecular sexual dimorphism. We employed a non-targeted metabolomic approach using liquid chromatography high-resolution mass spectrometry and revealed a significant sexual molecular dimorphism in the gonads, and to a lesser extent in the digestive glands, of D. polymorpha. Our results highlight the critical need to consider inter-sex differences in the metabolome of D. polymorpha to avoid confounding factors, particularly when investigating environmental effects on molecular regulation in the gonads, and to a lesser extent in the digestive glands.

What we know and don't know about the invasive zebra (Dreissena polymorpha) and quagga (Dreissena rostriformis bugensis) mussels

We summarized existing knowledge on Dreissena polymorpha (the zebra mussel) and D. r. bugensis (the quagga mussel), including data on their taxonomy, systematics, evolution, life cycle, reproduction, feeding, growth and longevity, population dynamics, interspecific competition, habitat requirements, and distribution within and among waterbodies. We analyzed the history of spread of both species and the major pathways and vectors of their spread in Europe and North America. Special consideration was given to their ecological and economic impacts and their natural enemies, like waterfowl, fishes, and parasites, as well as the prevention of their introduction, early detection, control, and containment. We also outlined the most salient ecosystem services provided by zebra and quagga mussels, including water purification, nutrient recycling, culling the effects of eutrophication, biomonitoring, and their role as a food resource for fish and waterfowl. Finally, we identified major knowledge gaps and key studies needed to better understand the biology, ecology, and impacts of these aggressive freshwater invaders. Our review indicates that much crucial information on the quagga mussel is still missing, including key life history parameters, like spawning cues, fecundity, and longevity, particularly for the profundal zone of deep lakes.