An old topic of emerging concern: Impacts of mineral (mining) particles on early life stages of fish

Several anthropogenic activities, such as dredging for marine navigation maintenance, subsea construction including the construction of offshore windfarms, urban development, and subsea and land-based mining activities can increase suspended particle loads in the pelagic environment. In Norway, tailings from land-based mining and processing facilities are in several locations placed in the marine environment, introducing high concentrations of suspended mineral particles into the water column. In this study we investigated the impacts of mineral particle tailings from a calcium carbonate (CaCO3) processing plant on early live stages of haddock (Melanogrammus aeglefinus) and Atlantic cod (Gadus morhua). Fish eggs (3 dpf) were exposed for 48 h to nominally 1 mg L-1 (low), 10 mg L-1 (medium), and 100 mg L-1 (high), with L and M being environmentally realistic concentrations at tailing release points. Results show that tailing particles rapidly adhered to eggs of both species, causing negative buoyancy (sinking of eggs) in M and H exposures. While tailings remained on egg surfaces also after exposure termination, adhesion seemed more effective in cod, leading to larger impacts on buoyancy even after exposure. Tailing exposure further induced early hatching and significantly reduced survival in M and H exposed embryos in both fish species, and L exposure in cod. Larvae were followed up until 4 days post hatch, revealing that tailing exposure also caused increased incidences of larvae malformation, such as tail, spine and marginal finfold deformation. This study shows that mineral particles can adhere to pelagic fish eggs, affecting egg buoyancy, survival, and development. While the number of countries currently practicing submarine mine tailing placement is limited, the findings of this study are also relevant for areas subjected to anthropogenic activities introducing enhanced suspended particle loads into the water column, and areas receiving increased terrigenous runoff due to changing climatic conditions.