Marine Disposal of Mine Tailings: Impacts on Pelagic Ecosystem Components in Norwegian Fjords

Mineral exploration is increasing worldwide due to rising resource demands. Mining activities generate large quantities of waste called mine tailings that need to be disposed. Several mineral-processing plants in Norway dispose their tailings in adjacent fjords, which may adversely affect organisms inhabiting marine ecosystems. While not necessarily leading to immediate death, fine-grained tailings can potentially cause sub-lethal stress to exposed organisms, which affects the organism's energy balance. This means that the organisms' energy has to be used to maintain basic body functions and handling of stress and less energy is available for development, growth and reproduction. Early life stages of animals, including larval stages of fish and copepods, are particularly vulnerable to stress, since their energy requirements for development and growth are high. In the DiTail project, we are studying how mine tailings and mine tailing components (particles, metals and contained processing chemicals) can affect early life stages of marine fish and copepods at the molecular and physiological level, as well as the animal?s energy balance. Acute exposure studies showed that Cu (administered as CuSO4) was toxic to C. finmarchicus at concentrations ranging from µg/L, with nauplii being more sensitive than adults and eggs being least sensitive. Corresponding exposure experiments showed that Ni was less toxic to C. finmarchicus, causing mortality in the mg/L concentration range, however, hatching of eggs was inhibited at 200 µg/L. Exposure experiments with early life stages (nauplii and copepodites) of C. finmarchicus feeding on tailing particles showed developmental delays, likely due to impacts on the animals' energy budget. In contrast, exposure experiments with adult C. finmarchicus showed that marble tailings were taken up by copepods but were not acutely toxic. To identify which tailing components are responsible for effects, we tested developmental effects of CaCO3 tailings containing processing chemicals, pure CaCO3 particles and tailings from a Cu ore. All tailing types in high concentrations caused developmental delays, reduced growth and lipid accumulation in C. finmarchicus. The DEB-kiss model predicted that the effects were caused by reduced energy assimilation in the presence of mineral particles. The presence of chemicals and metals did not increase the observed effects. In adult CV-stage Calanus, treatment with limestone particles (CaCO3-tailings) gave a stronger effect than Cu (5 and 30 µg Cu/L). Exposure to particles affected a broad range of metabolites linked to metabolism in the animals, including energy metabolism, amino and free fatty acids, nucleic acids, and cofactors, and pathways that support growth. The strongest effect was seen on the glutathione pathway, indicating that particle exposure induces oxidative stress. Surprisingly, Cu exposure alone did not induce oxidative stress. Experiments with environmental realistic concentrations of Cu (up to 6 µg/L) showed small effects in Atlantic cod larvae on survival, hatching success, respiration, and deformities after 14 days of exposure. In cod larvae, Cu (30 µg/L) induced early hatching and increased mortality. Studies with Atlantic cod and haddock larvae exposed to different concentrations of CaCO3 tailings containing processing chemicals (1, 10 and 100 mg/L) showed that particles rapidly attach to fish eggs, thereby decreasing their buoyancy and making them sink. Atlantic cod and haddock larvae exposed to 10 or 100 mg/L of CaCO3 tailings had a reduced hatching success, increased larvae morality and deformation rate. This was probably caused by the attachment of the tailings to the egg surfaces, covering them completely. To determine whether the presence of processing chemicals influences tailing attachment to fish eggs, we performed experiments on cod eggs comparing exposures of tailings with and without chemicals. The results showed that the timepoint of exposure onset is important, as tailings attached more to eggs that were exposed later in development and caused more severe effects than in eggs exposed early. Attachment was slightly more efficient in tailings containing chemicals. A reduction in positive buoyancy was observed already after 3 to 4 hours of exposure to a concentration that can be found in close vicinity to deposition sites. Experiments further showed that eggs start to sink after approximately 10 h of exposure. Metabolomics analysis of cod eggs and larvae exposed to 5, 15 and 30 µg Cu/L showed that eggs were less responsive than larvae. In contrast to the responses seen in adult Calanus, Cu exposure alone induced oxidative stress in early life stages of cod. In Cu exposed larvae, the metal induced increased protein turnover, and affected several vitamins. The highest Cu concentration had a profound effect on energy metabolism, and disturbed energetic pathways including glycolysis, fatty acid synthesis and ?-oxidation.

Data, knowledge, working techniques and models established in this project can directly aid future risk assessment and decision making for marine mine tailing disposal activities in fjord ecosystems. This was achieved through characterization of tailing materials in exposure studies and linking the observed effects to main effect drivers, as well as the progress made in modelling studies.

High demands for mineral resources are driving the rapid increase of mining activities worldwide. This activity generates large quantities of waste, so called tailings that need to be disposed of. Despite a current lack of knowledge on environmental implications, disposal of tailings in the sea, marine tailing disposal (MTD), is practiced in several countries including Norway. The introduction and spreading of fine inorganic particles, associated metals and processing chemicals in the water column may cause significant stress for exposed organisms. This is problematic because biological processes in the pelagic zone are crucial for both pelagic and benthic habitats and many bottom living organisms have pelagic larval stages. While exposure to mine tailings, especially to inorganic particles, does not necessarily cause acute toxicity, it will likely lead to effects such as reduced food intake and impaired physiological functioning. This can in turn cause reduced growth and development, which has severe consequences especially for early life stages of animals, e.g. fish larvae. However, such impacts of MTD have not been studied yet. In this project we are going to investigate impacts of mine tailings and mine tailing components on the planktonic copepod species Calanus finmarchicus, and early life stages of stages of cod (Gadus morhua). We want to gain an in-depth understanding on tailing effects from a molecular to individual level, applying state of the art molecular techniques and measuring tailored physiological endpoints. Through integration of effects data into tailing spreading models that will be develop within this project, we will be able to assess the exposure of individuals to tailings, which in turn can give valuable information about effects on local populations in terms of impacts to recruitment. The data and models produced in this project will substantially support environmental risk assessment of MTD.