Seite - 166 - in Freshwater Microplastics - Emerging Environmental Contaminants?

per feeding) resulted in formations ofMPaggregates in the gut of the langoustine that might have reduced the uptake of nutrients. Effects on survival and growth as an outcome of reduced feeding have also been shown in themarine calanoid copepodCalanushelgolandicus [2].Thepresenceof20μmPSbeads (75PmL 1) reduced the feeding on algae and provoked a feeding preference for smaller algae prey. Althoughcalanoid copepods are raptorialwith strong size and taste discrimina- tion, a studybyLee et al. [53] demonstrated a nonselective ingestion of 0.05, 0.5, and 6 μm PS beads by the marine Tigriopus japonicus. While all individuals survived an acute exposure (96 h), a two-generation chronic exposure to 0.05 (>12.5 μgmL 1) and 0.5 μmbeads (25 μgmL 1) induced a concentration- and size-dependentmortalityandasignificantdecrease infecundityby0.5and6μmPS beads.Again, theobservedeffectsweremainly interpretedasrelatedtoanimpaired nutritional uptake. Inaddition to thepresumednutritionaleffects,Bundyetal. [54]haveshownthat calanoid copepods regularly attack, capture, and reject 50 μm PS beads. This pre-ingestion behaviormay result in a negative energy budget.Additionally,Cole et al. [55]documented thatMPsattach to the external carapace andappendagesof marine zooplankton, which then might interfere with locomotion, molting, and feeding. The relevance of adhered particles was also shown in the marine crabs Ucarapax andCarcinusmaenas [56, 57].Here,MPexposure led to an accumula- tion in thestomachandhepatopancreasbutalso toanaccumulation in thegills.The respiratory uptake and the following adhesion ofMPs to the gillsmight influence the branchial function. For instance, Watts et al. [58] found a significantly decreasedoxygen consumptionofMP-exposed crabs after 1 h andobserved some adaptation as oxygen consumption returned to normal after 16h. 3.1.4 Bivalves The transfer of MPs to tissues induces cellular injuries as well as inflammatory responses in themarinefilter-feedingmusselM.edulis.After3daysofexposure to 3.0 and 9.6 μm PS beads, Browne et al. [24] observed a translocation to the circulatory (hemolymph) systemwhere they remained for up to48days.Although the exact pathway is yet unknown, the transfer may be due to specialized enterocyteswhich inhumans and rodents transportMPs from thegut into follicles fromwhich they can translocate into the circulatory system. In addition, particles accumulating in thedigestiveglandwere takenupbycellsof the lysosomalsystem, which resulted inan inflammatory responseandhistological alterations (lysosomal membranedestabilization) [5].Asaconsequenceofparticle interactionwith tissue orhemolymphcells,marinebivalves canexpress an immediate stress and immune response.This results inan increasedproductionof reactiveoxygenspeciesaswell as anti-oxidant and glutathione-related enzymes but also changes the hemocyte phagocytosis activity and the ratio of granulocytes andhyalinocytes [59, 60]. 166 C.Scherer et al.