Nocturnal seston: A key to explain the cadmium transfer from seawater to mussels (Mytilus chilensis).

The objective of this work was to discover a biochemical pathway to explain the transfer of cadmium, a toxic element, from seawater to cultured mussels. Understanding the intricacies of this transfer is crucial for global mussel crops, as it has the potential to mitigate risks to human health and prevent economic losses in the industry. We focused our investigation on Yal Bay, a typical area with intense mussel aquaculture activity (16,000 t y-1) in the inland sea of southern Chile. Seasonal samples of blue mussels (Mytilus chilensis) were collected and analyzed from September 2014 to December 2015 at two integrated depths (0-5 m and 5-10 m). Diurnal and nocturnal seston, seawater, benthic sediments and decanted suspensions from the water column were recorded. Our findings indicate that nocturnal seston satisfactorily explains the presence of cadmium in Mytilus chilensis aquaculture throughout its annual temporal distribution (Spearman rs = 0.63, p = 0.002).

Drastic difference in cadmium concentration in mussels (Mytilus chilensis) observed between seasons in natural bed and aquaculture systems in Chile.

Globally, Chile is the second largest producer of mussels, with 99% of production concentrated in the inland sea of the Los Lagos Region, Southern Chile. This study reveals that seasons produce a drastic difference in the cadmium concentration (Cd) in marine mussels in bay, channel, and fjord ecosystems in this area. As the global mussel industry continues its rapid expansion, a complete understanding of cadmium pathways is critical in order to minimize the cadmium content in harvests. In this study, biweekly sampling was conducted in Chiloé (Southern Chile), during five consecutive seasons from June 2014 to November 2015. Cadmium in the soft tissues (ST) and in the content of the digestive gland (CDG) of Mytilus chilensis were investigated, in addition to resuspensions and seston to determine the effect of the seasons on metal bioassimilation capacity. In spring, the (Cd) between CDG and ST varied by approximately 2 mg Cd kg-1 dry mass (DM). In summer and autumn, the (Cd) in CDG increased from 3 to 6 mg Cd kg-1 while the (Cd) in ST decreased from 2.5 to 1.5 mg Cd kg-1 DM. The three ecosystems showed the same cadmium bioconcentration trends in all seasons, revealing coherent global trends. These findings should caution the industry and coastal populations about the seasonal variability and intensity of cadmium metal transfer to biofilters, especially because of the adverse effects of cadmium consumption on human health. Additionally, this study found that mussels in natural beds concentrate more Cd (> 1 mg Cd kg-1 DM) than in industrial facilities. Multiregression analysis showed and explained the cadmium in CDG for three ecosystems: channel (R2 0.9537), bay (R2 0.5962), and fjord (R2 0.4009). The independent variable nocturnal seston was able to explain the increase in cadmium.

Cadmium determination in Chilean blue mussels Mytilus chilensis: Implications for environmental and agronomic interest.

Cadmium is present in agricultural soil composition and is assimilated by plants. The mussel industry generates large volumes of calcareous valves as a byproduct of processing in factories. This solid waste is ground, stored and disposed of in the form of agricultural supplies near production areas in almost all regions of the world. Cd content was recorded in these calcareous substrate by-products of industrial processes. In this study, mussel shells were investigated in three areas in the sea of Chile; two areas with high aquaculture activity and one in a non-production area. Mass Spectrometry was used for [Cd] readings. There are no significant differences (p=0.92) in [Cd] between the studied areas. Additionally, the [Cd] observed in valves was also similar relative to different depths. The low [Cd] observed in valves (~0.014±0.0049mgCdkg-1 dry) suggests the potential use of this industrial byproduct in agricultural applications.