Increasing mercury bioaccumulation and biomagnification rates of Nile perch (Lates niloticus L.) in Winam Gulf, Lake Victoria, Kenya.

Autor: Drouillard KG; Great Lakes Institute for Environmental Research, University of Windsor, Windsor, Ontario, Canada. Electronic address: kgd@uwindsor.ca., Campbell L; School of the Environment, Saint Mary's University, Halifax, Nova Scotia, Canada., Otieno D; Kenya Marine and Fisheries Research Institute, Kisumu, Kenya., Achiya J; Kenya Marine and Fisheries Research Institute, Kisumu, Kenya., Getabu A; Kisii University, Kisii, Kenya., Mwamburi J; Kenya Marine and Fisheries Research Institute, Kisumu, Kenya., Sitoki L; Technical University of Kenya, Nairobi, Kenya., Omondi R; Kisii University, Kisii, Kenya., Shitandi A; Kisii University, Kisii, Kenya., Owuor B; Kisii University, Kisii, Kenya., Njiru J; Kenya Marine and Fisheries Research Institute, Kisumu, Kenya., Bullerjahn G; Biological Sciences, Bowling Green State University, Bowling Green, OH, USA., Mckay RM; Great Lakes Institute for Environmental Research, University of Windsor, Windsor, Ontario, Canada., Otiso KM; School of Earth, Environment and Society, Bowling Green State University, Bowling Green, OH, USA., Tebbs E; Department of Geography, King's College London, United Kingdom.
Jazyk: angličtina
Zdroj: The Science of the total environment [Sci Total Environ] 2024 Mar 15; Vol. 916, pp. 170059. Date of Electronic Publication: 2024 Jan 17.
DOI: 10.1016/j.scitotenv.2024.170059
Abstrakt: The Nile perch (Lates niloticus L.) commercial fishery for Lake Victoria in East Africa is an important source of revenue and employment. We focused on shifts in food web structure and total mercury (THg) bioaccumulation and biomagnification in Nile perch, and lower food web items collected from Winam Gulf (Kenya) sampled 24 years apart (1998 and 2022). Stable isotope carbon (δ 13 C) values were higher in all species from 2022 compared to 1998. Stable nitrogen isotope (δ 15 N) values in baseline organisms were lower in 2022 compared to 1998. In Nile perch, δ 15 N values were correlated with total length, but the δ 15 N-length regressions were steeper in 1998 compared to 2022 except for one large (158 cm) Nile perch from 1998 with an uncharacteristically low δ 15 N value. Total Hg concentrations were lower in lower trophic species from 2022 compared to 1998. However, the THg bioaccumulation rate (as a function of fish length) in Nile perch was greater in 2022 compared to 1998 resulting in 24.2 % to 42.4 % higher wet weight dorsal THg concentrations in 2022 Nile perch for market slot size (50 to 85 cm) fish. The contrasting observations of increased THg bioaccumulation with size in 2022 against decreases in the rate of trophic increase with size and lower THg concentrations of lower food web items imply reduced fish growth and potential bioenergetic stressors on Winam Gulf Nile perch. All samples except 1 large Nile perch (139 cm total length collected in 2022) had THg concentrations below the European Union trade limit (500 ng/g wet weight). However, for more vulnerable individuals (women, children and frequent fish eaters), we recommend a decrease in maximum monthly meal consumption for 55-75 cm Nile perch from 16 meals per month calculated for 1998 to a limit of 8 meals per month calculated for 2022.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)
Databáze: MEDLINE
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