Abstract
The present study evaluates the spatio-temporal variation and magnitude of total mercury (THg) contamination in two diving bird species, the Little Cormorant (Microcarbo niger) and the Oriental Darter (Anhinga melanogaster), across diverse wetland habitats in India. Sampling was conducted seasonally from 2022 to 2024 across six sites: freshwater agricultural lands, saline agricultural lands, and both freshwater and coastal mangrove ecosystems. Bird droppings (n = 72) were collected using non-invasive methods, followed by acid digestion and atomic absorption spectrophotometry to quantify THg concentrations. Using a full-factorial ANOVA, we found strong main effects of year, species, and location, alongside significant interactions, suggesting a complex interplay of factors influencing Hg exposure in piscivorous birds. Coastal wetlands, notably Puthuvype and Ulavaipu, showed elevated THg concentrations and an increasing temporal trend, in both piscivorous species, with higher exposure in Little Cormorants than Oriental Darters, reaching up to 48.79 mg/kg and 36.72 mg/kg in droppings, respectively, by 2024. In contrast, inland sites like Maramangalam showed minimal contamination, likely due to reduced anthropogenic inputs. Temporal trends suggest a nearly three-fold rise in THg over three years, potentially associated with anthropogenic inputs and environmental changes in Hg cycling. This significant difference in mercury levels could be associated with species-specific foraging strategies and habitat use. Our findings demonstrate the utility of bird droppings as a non-invasive indicator of recent, diet-derived THg exposure, revealing pronounced site-specific contamination patterns that may pose neurotoxic risks to avian health and reproduction. These results emphasize the urgent need for targeted monitoring and mitigation strategies to address Hg contamination in rapidly urbanising tropical coastal ecosystems, safeguarding biodiversity and ecosystem integrity.
Acknowledgements
The first and last authors are grateful to Mr. Jaffer for his support in collecting droppings at various sites during the study period.
Funding
The authors declare that no funds, grants, or other support were received during the preparation of this manuscript.
Author information
Authors and Affiliations
Corresponding authors
Ethics declarations
Competing interests
The authors declare no competing interests.
Additional information
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Supplementary Information
Below is the link to the electronic supplementary material.
Supplementary Material 1 (download DOCX )
Rights and permissions
Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.
Reprints and permissions
About this article
Cite this article
Shadiya, F., Galić, V., Bjedov, D. et al. Spatio-temporal dynamics of total mercury contamination in diving birds as bioindicators of tropical wetlands in India.
Sci Rep (2026). https://doi.org/10.1038/s41598-026-55158-9
Received:
Accepted:
Published:
DOI: https://doi.org/10.1038/s41598-026-55158-9
Keywords
- Mercury bioaccumulation
- Waterbirds
- Coastal wetlands
- Temporal-spatial variation
- Non-invasive biomonitoring
Source: Ecology - nature.com
