ENSO climate forcing of the marine mercury cycle in the Peruvian upwelling zone does not affect methylmercury levels of marine avian top predators

ENSO climate forcing of the marine mercury cycle in the Peruvian upwelling zone does not affect methylmercury levels of marine avian top predators Renedo M. auteur aut IRD Point David auteur aut IRD Sonke J. E. auteur aut IRD Lorrain Anne auteur aut IRD Demarcq Hervé auteur aut IRD Graco M. auteur aut IRD Grados D. auteur aut IRD Gutierrez D. auteur aut IRD Medieu A. auteur aut IRD Munaron Jean-Marie auteur aut IRD Pietri A. auteur aut IRD Colas F. auteur aut IRD Tremblay Yann auteur aut IRD Roy Amédée auteur aut IRD Bertrand Arnaud auteur aut IRD Bertrand S. L. auteur aut IRD text journalArticle eng text/pdf born digital access Climate change is expected to affect marine mercury (Hg) biogeochemistry and biomagnification. Recent modeling work suggested that ocean warming increases methylmercury (MeHg) levels in fish. Here, we studied the influence of El Nino Southern Oscillations (ENSO) on Hg concentrations and stable isotopes in time series of seabird blood from the Peruvian upwelling and oxygen minimum zone. Between 2009 and 2016, La Nina (2011) and El Nino conditions (2015-2016) were accompanied by sea surface temperature anomalies up to 3 degrees C, oxycline depth change (20-100 m), and strong primary production gradients. Seabird Hg levels were stable and did not co-vary significantly with oceanographic parameters, nor with anchovy biomass, the primary dietary source to seabirds (90%). In contrast, seabird Delta Hg-199, proxy for marine photochemical MeHg breakdown, and delta N-15 showed strong interannual variability (up to 0.8 and 3%, respectively) and sharply decreased during El Nino. We suggest that lower Delta Hg-199 during El Nino represents reduced MeHg photodegradation due to the deepening of the oxycline. This process was balanced by equally reduced Hg methylation due to reduced productivity, carbon export, and remineralization. The non-dependence of seabird MeHg levels on strong ENSO variability suggests that marine predator MeHg levels may not be as sensitive to climate change as is currently thought. specialized Hg stable isotopes MIF Northern Humboldt current system climate change ecology PEROU PACIFIQUE 034 032 021 Environmental Science and Technology 55 23 15754-15765 2021 0013-936X https://www.documentation.ird.fr/hor/fdi:010084335 10.1021/acs.est.1c03861 0013-936X [F B010084335] https://www.documentation.ird.fr/hor/fdi:010084335 https://www.documentation.ird.fr/intranet/publi/2022-04/010084335.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2022-04-06 2025-02-24 fdi:010084335 fre