Effects of tropical cyclone Amphan on the copepods of the Ganges estuary

ABSTRACT

Tropical cyclones are increasingly affecting estuarine communities. The effects of category-5 tropical cyclone Amphan (landfall on 20 May 2020 near the Ganges estuary mouth) on the copepod community of the Ganges estuary were studied. Copepod assemblages were sampled before (February–December 2019), shortly after (31 May–12 June 2020) and post-(September–November 2020) Amphan periods. It was hypothesized that shortly after Amphan a relatively homogeneous community consisting of a few estuarine specialists would succeed but that would soon be replaced by a heterogeneous one; however, those specialists would continue their dominance. Shortly after Amphan species richness declined but the recovery process was completed within months, led by Paracalanus parvus, Bestiolina similis, Acartia spinicauda, Acartiella tortaniformis and Oithona brevicornis. Spatial homogeneity of the community that prevailed in pre- and shortly after Amphan was lost in post-Amphan. The unilateral dominance of B. similis observed in the pre-Amphan period was challenged by P. parvus, A. spinicauda, A. tortaniformis and O. brevicornis after Amphan. Shortly after Amphan A. spinicauda proliferated and co-dominated the estuary with A. tortaniformis but the latter replaced the former within a few months. The copepod community experienced rearrangements in species composition, abundance and dominance hierarchy; therefore, its regular monitoring is recommended.

KEYWORDS:

• Diversity
• abundance
• dominance
• Indian Sundarbans

Acknowledgements

The authors thank Ms Papiya Bhattacharya for her help in fieldwork and Ms Susmita Raulo for her help in preparation of the map of the study area. Thanks to the anonymous reviewers who helped in improving the manuscript through their constructive comments. Dr Paul thanks DST Inspire Faculty Award [Sanction no: DST/INSPIRE/04/2016/0000036] of the Government of India for his fellowship and funding the research. Dr Paul further extends his gratitude to the Core Research Grant sanctioned by the Science and Engineering Research Board (SERB) [Sanction: EMR/2017/001111 dated 24 July 2018] of the Government of India which met the fellowship of Mr Karan. Dr Bhattacharya extends his gratitude to the Estuarine and Coastal Studies Foundation for financial assistance received during the course of the study. Thanks to Head of Department of Zoology, University of Calcutta and the Director of Estuarine and Coastal Studies Foundation, West Bengal for providing facilities related to this research. The authors thank the Intergovernmental Oceanographic Commission, UNESCO for endorsing the present study as a part of the (Decade Action: No. 122.2 – ‘Periodic cyclone effects on Gangetic food web) United Nation Decade of Ocean Science for Sustainable Development (2021–2030).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Declaration

Conflicts of interest

All authors declare that they have no conflict of interest on connection with this study.

Ethical approval

Biological samples were collected in accordance with the ethical standards of University of Calcutta, India.

Author contributions

Conceptualization: Sourav Paul; Methodology: Bhaskar Deb Bhattacharya, Samya Karan, Sourav Paul; Formal analysis and investigation: Sourav Paul, Bhaskar Deb Bhattacharya, Samya Karan; Writing – Sourav Paul; Writing – review and editing: Sourav Paul, Bhaskar Deb Bhattacharya, Samya Karan; Funding acquisition: Sourav Paul; Resources: Sourav Paul; Supervision: Sourav Paul.

Sampling and field studies

All necessary permits for sampling and observational field studies have been obtained by the authors from the competent authorities and are mentioned in the acknowledgements, if applicable. The study is compliant with CBD and Nagoya protocols.

Data availability

The datasets generated during and/or analysed during the current study are not publicly available but are available from the corresponding author on reasonable request.

Additional information

Funding

This work was supported by Department of Science and Technology, Government of India [Grant Number Sanction no: DST/INSPIRE/04/2016/0000036]; Science and Engineering Research Board [Grant Number Sanction: EMR/2017/001111 dated 24 July 2018].