Extractive activities in the deep sea are poised to advance faster than the science needed to evaluate risks. Here, we call for a strong precautionary approach in developing these industries.Food and energy insecurity have been exacerbated by climate change, conflict, and disease, with global energy demands only expected to grow. Seabed mining and deep-sea fishing have been suggested as ways to support shifting to renewable energy and increasing food supply. These industries are likely to impact one of the largest habitats on Earth, our ocean's mesopelagic zone, at depths between ~200 and 1000 m. Once assumed to be lifeless, we now know the mesopelagic zone is rich with life and a vital component of the global ecosystem. Recently, industries have begun exploratory extractive activities, while our scientific understanding of the impacts of these activities on the mesopelagic zone is trailing behind (Fig. 1). Here, we outline five reasons why we advocate for a precautionary approach to deep-sea exploitation in order to make evidencebased decisions.
Since the phasing out and eventual ban on the production of organohalogen flame retardants, the use of organophosphate flame retardants (OPFRs) has increased rapidly. This has led to the detection of OPFRs in various environments including the Arctic. Two of the most prevalent OPFRs found in the Arctic are tris(2-chloroisopropyl) phosphate (TCPP), and 2-ethylhexyl diphenyl phosphate (EHDPP). The impacts of exposure to OPFRs on Arctic organisms is poorly understood. The objective of the present study was to determine the effects of exposure to TCPP, EHDPP, and a mixture of OPFRs on gene expression patterns in Atlantic cod, Gadus morhua. Precision-cut liver slices from Atlantic cod in vitro were exposed to either TCPP or EHDPP alone or in a mixture and sampled at 2 different time points to quantify gene expression patterns using RNA sequencing. We exposed the liver slices to 2 concentrations of TCPP and EHDPP, one of which was chosen based on the levels found in the Arctic environment. The RNA sequencing results demonstrated differential expression of hundreds of genes in response to exposure. The genes representing cholesterol biosynthesis and lipid metabolism pathway were significantly enriched in all the treatment groups. Almost all the cholesterol biosynthesis genes were significantly down-regulated in response to OPFR exposure. The effects on these pathways could involve various physiological processes including reproduction, growth, and behavior as well as adaptation to changing temperatures. Membrane fluidity is an important adaptive mechanism among aquatic organisms. Altered cholesterol homeostasis could have long-term consequences by altering the adaptive potential of aquatic organisms to changing water temperatures, particularly those living in polar environments. These results suggest that OPFRs could have unique effects on the organisms living in the Arctic compared with other environments. Further studies are needed to understand the long-term impacts of exposure to environmentally realistic concentrations using laboratory and field-based studies.
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