Effects of hollow glass microspheres on the benthic and benthopelagic organisms Capitella sp. and Mytilus edulis

Hollow glass microspheres (HGM) are widely used as fillers in composite materials including paints and plastics. Further, due to their high reflectivity, an approach involving HGM application on Arctic sea ice surfaces has been considered as a measure to reduce ice loss and thus help mitigate climate change effects. In this study we investigated potential impacts of HGMs (average size 47 µm) on two marine species, the benthic polychaete Capitella sp. and the filter feeding blue mussel Mytilus edulis. Capitella were exposed to three concentrations of non-buoyant HGMs with and without sediment (1, 10 and 100 mg g⁻¹ sediment equalling 0.1, 1 and 10 g total HGMs). After a 42 day-exposure (juveniles to adult live stages), HGM uptake, survival and growth were determined. Adult Mytilus edulis were exposed for 10 days to three concentrations (1, 10 and 100 mg L⁻¹) of fresh and biofouled HGMs, and HGM uptake, survival, condition index, clearance rate, cytotoxic and genotoxic damage in haemocytes were analysed. Results show that, while both species ingest HGMs, there were no significant impacts on survival. Exposure to medium and high HGM concentrations in presence and absence of sediment significantly impacted growth and development of Capitella. In contrast, the shorter-term exposure to fresh or biofouled HGMs did not affect the nutritional status, condition index or filtering capacity of adult M. edulis. High concentrations of biofouled HGMs did cause a slight response on cellular level in M. edulis, as eosinophilic cell counts decreased. While responses in M. edulis were less clear, the HGM mode of action on Capitella may be related to alterations in energy budget. Further studies are needed to investigate modes of action and determine effect threshold concentrations in potential target species.