Comparison of Freshwater Mussels Unio tumidus and Unio crassus as Biomonitors of Microplastic Contamination of Tisza River (Hungary)

Abstract

Unio crassus and Unio tumidus mussels were collected at four sampling sites in the Tisza River (Hungary) to investigate their applicability as sentinel species for the biomonitoring of microplastic contamination. Since mussels, as filter feeders, are able to ingest particles only below a physically defined size, it was expected that their sentinel role in rivers is restricted to small particles, including fibers or microfibers. This assumption was confirmed by our results, as fibers were detected as the dominant particles in all the 80 mussel samples investigated. The length and diameter of the fibers changed in the size range of 20–1000 μm and 10–75 μm, respectively. The number of fibers in the individuals originating from the same sampling site was nearly two times higher in Unio tumidus than in Unio crassus and amounted to 2.7–4.9 and 5.2–8.3 items/individual. The fiber/g soft tissue ratio between these species could be characterized by a factor of three. After applying Raman spectrometry, mostly indigo-dyed polyethylene terephthalate and cellulose-based fibers, as well as a few larger (200 um) polyamide fragments, were identified. The microplastic particles stored temporarily by mussels provide only restricted qualitative information on the microplastic load of the Tisza River, and as our observations confirmed, the sampling efficiency of these ‘living sampling devices’ is highly species-specific.

First report on microplastics in a freshwater clam, Corbicula baudoni, in Vietnam

“…Generally, the shorter fiber length was, the higher fiber number was in both large and small clams (Figure 3). The two MP shapes of fiber and fragment in C. baudoni of our study (Figure 4) were in line with those in some other freshwater clam species from Italian lakes and Hungarian river in previous investigations [23,24,26]. However, we did not find the MP shapes of film or pellet in C. baudoni from the Mekong River which were noted in some other freshwater clams from Chinese and Turkish lakes [20,25].…”

“…Our study firstly reported the MPs in the freshwater clam, C. baudoni. The MP abundance in the C. baudoni in present study (3.4 -14.6 items/idv) was within the range with those in two other freshwater bivalve species (Unio tumidus, 2.7 -4.9 items/idv; and Unio crassus, 5.2 -8.3 items/idv) from a river in Hungary [24] and another bivalve species (Anodonta sp., 0.75 -10 items/idv) from a lake in Turkey [25]. However, the MP abundance in C. baudoni from Mekong River was much higher than the that in some other freshwater bivalves from Italy and Turkey such as Unio elongalulus (0.04 -1.39 items/idv), Unio damescensis (0.50 -2.50 items/idv), Corbicula fluminea (0.17 -1.78 items/idv), and Dreissena polymorpha (0.02 -1.00 items/idv; [23, 25,26]).…”

“…(5.7 -7.9 cm) and Anodonta sp. (9.33 cm) in previous studies [23,24,25,26]. Therefore, the similar or different MP abundance in the C. baudoni (our study) and other freshwater bivalves [20,23,24,25,26] should be due to (i) different bivalve species could have different food/ particle ingestion rate; and (ii) the levels of MP contamination in surrounding environments of the bivalves from the field.…”

“…(9.33 cm) in previous studies [23,24,25,26]. Therefore, the similar or different MP abundance in the C. baudoni (our study) and other freshwater bivalves [20,23,24,25,26] should be due to (i) different bivalve species could have different food/ particle ingestion rate; and (ii) the levels of MP contamination in surrounding environments of the bivalves from the field. The presence of MPs in clams from the Mekong River gave rise of potential health risks to local people which is discussed in the section 3.4 below.…”

“…So far, there have been a lot of studies on MPs in marine bivalves such as blue mussels, hard clams, and oysters in the world (e.g. reviewed by [22]), but only a few studies dealing with MPs in freshwater bivalves [20,23,24,25,26] especially no report on MPs in freshwater clams in Southeast Asia. Our study firstly reported the MPs in the freshwater clam, C. baudoni.…”