Browsing by Author "Li, Mi-Ling"
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Item Global fishing patterns amplify human exposures to methylmercury(Proceedings of the National Academy of Sciences, 2024-09-23) Li, Mi-Ling; Thackray, Colin P.; Lam, Vicky W. Y.; Cheung, William W. L.; Sunderland, Elsie M.Significance Methylmercury (MeHg) is a potent neurotoxicant that adversely affects human health. Wild-caught marine species sold in the global commercial seafood market are the main MeHg exposure source for many populations. Here, we identify where and how much MeHg is extracted from the ocean during global marine fisheries harvests. We find that the geographic distribution of MeHg “fished” from the oceans predominantly reflects the harvesting locations of large pelagic species. Expansion of multinational industrial fisheries, particularly in low-latitude ecosystems, has exacerbated MeHg exposures for global seafood consumers. This work reveals that most subsistence fishing populations likely exceed exposure thresholds for MeHg and highlights the disproportionate impacts of global mercury pollution on subsistence fisheries in developing countries. Abstract Global pollution has exacerbated accumulation of toxicants like methylmercury (MeHg) in seafood. Human exposure to MeHg has been associated with long-term neurodevelopmental delays and impaired cardiovascular health, while many micronutrients in seafood are beneficial to health. The largest MeHg exposure source for many general populations originates from marine fish that are harvested from the global ocean and sold in the commercial seafood market. Here, we use high-resolution catch data for global fisheries and an empirically constrained spatial model for seafood MeHg to examine the spatial origins and magnitudes of MeHg extracted from the ocean. Results suggest that tropical and subtropical fisheries account for >70% of the MeHg extracted from the ocean because they are the major fishing grounds for large pelagic fishes and the natural biogeochemistry in this region facilitates seawater MeHg production. Compounding this issue, micronutrients (selenium and omega-3 fatty acids) are lowest in seafood harvested from warm, low-latitude regions and may be further depleted by future ocean warming. Our results imply that extensive harvests of large pelagic species by industrial fisheries, particularly in the tropics, drive global public health concerns related to MeHg exposure. We estimate that 84 to 99% of subsistence fishing entities globally likely exceed MeHg exposure thresholds based on typical rates of subsistence fish consumption. Results highlight the need for both stringent controls on global pollution and better accounting for human nutrition in fishing choices.Item Historical climate drivers and species’ ecological niche in the Beaufort Sea food web(ICES Journal of Marine Science, 2024-05-14) Sora, Kristen J.; Wabnitz, Colette C. C.; Steiner, Nadja S.; Sumaila, U. Rashid; Hoover, Carie; Niemi, Andrea; Loseto, Lisa L.; Li, Mi-Ling; Giang, Amanda; Gillies, Emma; Cheung, William W. L.Climate change impacts have been particularly acute and rapid in the Arctic, raising concerns about the conservation of key ecologically and culturally significant species (e.g. beluga whales, Arctic cod), with consequences for the Indigenous community groups in the region. Here, we build on an Ecopath with Ecosim model for the Canadian Beaufort Sea Shelf and Slope to examine historical (1970–2021) changes in the ecological dynamics of the food web and key species under climate change. We compare the individual and cumulative effects of (i) increased sea surface temperature; (ii) reduced sea ice extent; (iii) ocean deoxygenation; and (iv) changing ocean salinity in the ecosystem models. We found that including salinity time series in our ecosystem models reduced the diversity found within the ecosystem, and altered the trophic levels, biomass, and consumption rates of some marine mammal and fish functional groups, including the key species: beluga whales, as well as Arctic and polar cods. Inclusion of the dissolved oxygen time series showed no difference to ecosystem indicators. The model findings reveal valuable insights into the attribution of temperature and salinity on Arctic ecosystems and highlight important factors to be considered to ensure that existing conservation measures can support climate adaptation.Item Investigating the dynamics of methylmercury bioaccumulation in the Beaufort Sea shelf food web: a modeling perspective(Environmental Science: Processes and Impacts, 2022-06-24) Li, Mi-Ling; Gillies, Emma J.; Briner, Renea; Hoover, Carie A.; Sora, Kristen J.; Loseto, Lisa L.; Walters, William J.; Cheung, William W. L.; Giang, AmandaHigh levels of methylmercury (MeHg) have been reported in Arctic marine biota, posing health risks to wildlife and human beings. Although MeHg concentrations of some Arctic species have been monitored for decades, the key environmental and ecological factors driving temporal trends of MeHg are largely unclear. We develop an ecosystem-based MeHg bioaccumulation model for the Beaufort Sea shelf (BSS) using the Ecotracer module of Ecopath with Ecosim, and apply the model to explore how MeHg toxicokinetics and food web trophodynamics affect bioaccumulation in the BSS food web. We show that a food web model with complex trophodynamics and relatively simple MeHg model parametrization can capture the observed biomagnification pattern of the BSS. While both benthic and pelagic production are important for transferring MeHg to fish and marine mammals, simulations suggest that benthic organisms are primarily responsible for driving the high trophic magnification factor in the BSS. We illustrate ways of combining empirical observations and modelling experiments to generate hypotheses about factors affecting food web bioaccumulation, including the MeHg elimination rate, trophodynamics, and species migration behavior. The results indicate that population dynamics rather than MeHg elimination may determine population-wide concentrations for fish and lower trophic level organisms, and cause large differences in concentrations between species at similar trophic levels. This research presents a new tool and lays the groundwork for future research to assess the pathways of global environmental changes in MeHg bioaccumulation in Arctic ecosystems in the past and the future.