Approved Abstracts

Assessment of the dormant toxicity exerted by polluted sediments from four estuaries of the Bay of Biscay using in vivo and in vitro bioassays with Hediste diversicolor polychaetes

Author(s): Garcia-Velasco N; Doni L; Fernandez-Egileor J; Carrero JA; Urionabarrenetxea E; Gredilla A; de Diego A.; Izagirre U; Soto M;
Presenter: Nerea Garcia-Velasco

Estuaries have historically been subjected to urban, industrial and port development, leading to pollution due to untreated waste disposal. Sediments in these areas are considered reservoir of environmental changes since they accumulate discharged pollutants associated to organic matter, silt and clay. The presence of high levels of ancient pollutants in subsurface sediments poses a high potential environmental risk if physico-chemical conditions are altered (e.g. storm events, dredging operations). In order to assess the dormant hazards resulting from high levels of pollutants in sediments bioassays with environmentally relevant species should be used. In fact, sediment toxicity tests are fundamental to determine effects-thresholds for risk assessment and for dredging operations management. Presently, innovative in vivo and in vitro tests with Hediste diversicolor polychaetes were implemented to assess the toxicity of sediment from four estuaries of the Bay of Biscay. Sediments were sampled in the Nerbioi-Ibaizabal (4 sites: Udondo, Kadagua, Benedicta, Zorroza), in Butroe (Plentzia-reference site-), in La Gironde (Plassac) and Charente (Rochefort) estuaries. Samplings were performed in October 2018 and March, July and October 2019. Physico-chemical and metal characterization was done for all the sediments collected. For in vivo assays, polychaetes from Galician coasts of similar size (2.3-3.3 g) were weighted in groups of 5 and introduced into the different sediments collected in the Bay of Biscay during 7 d. After, metal accumulation, mortality, weight loss, histopathology and oxidative stress were measured. Regarding in vitro approaches, coelomocytes were extruded and exposed to sediment elutriates prepared following DIN 38414-S4. After 2 and 24 h coelomocytes viability was measured with the aid of Calcein-AM viability assay. In parallel the Sea Urchin Embryo Test was carried out (ICES, 2012), exposing larvae to elutriates coming from the sampled sediments. The characterization indicated that sediments collected at different estuaries and seasons were all loamy and with high OM content (>3 %), with the exception of Benedicta which was sandy and low in OM. Sediments from Udondo and Benedicta showed the highest concentrations of metals (As, Cr, Cu Ag, Cd, Hg, Zn, Ni) while in the rest of the sampled sediments metals were much lower. Likewise, polychaetes maintained in sediments from Udondo and Benedicta showed the highest metal accumulation in tissues. The mortality found after in vivo exposure of polychaetes was not treatment dependent and the differences in weight loss between treatments could be related to the OM content of the different sediments. After histopathology, a trend of major blood irrigation in the digestive epithelia of polychaetes maintained in Udondo and Benedicta was found. Regarding in vitro, a significant decrease in cell viability was observed after exposure to elutriates from Benedicta in all season, probably due to the presence of As, Cd and Pb in elutriates. The Sea Urchin Embryo test reinforced these results since embryos exposed to elutriates from Udondo and Benedicta showed the lowest capacity to grow and evident malformations, mainly in Udondo collected in Oct 2019. The in vivo and in vitro approaches developed for H. diversicolor appeared to be accurate for estuarine sediment toxicity testing since indicated severe effects exerted by sediments with high contamination levels (Udondo and Benedicta in Nerbioi-Ibaizabal estuary). Acknowledgements: Basque Gov. (IT1302-19, IT1213-19), U. Basque Country and MINECO (seaDIMENTOX CTM2017-87766-R).

Keywords: Sediment ecotoxicology; Innovative bioassays; Polychaetes




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