Changes of the copepod community of Ganges estuary following tropical cyclone Yass

doi:10.21203/rs.3.rs-4862370/v1

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Changes of the copepod community of Ganges estuary following tropical cyclone Yass

https://doi.org/10.21203/rs.3.rs-4862370/v1

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Tropical cyclones (TCs) are straining the lower food web of Indian estuaries but regular institutional monitoring of those changes is rare. For that the ‘Cyclone Ecology’ research program was established in February 2019 on the Muriganga stretch of the Ganges estuary. On 26 May 2021, a category-1 TC Yass disrupted the ‘Cyclone Ecology’ research program sites. A before-after impact assessment was conducted of the cyclone-mediated changes. Water and copepod samples were collected in the pre-Yass (November 2020 to March 2021) and the post-Yass (June 2021) periods. The aim was to assess changes in diversity and dominance of the copepod community following TC Yass. Post-Yass, estuary became polyhaline for a while losing its usual meso-haline characteristic. Species richness of the copepod community was higher during post-Yass than the pre-Yass period. During the pre-Yass, calanoid copepods Bestiolina similis, Paracalanus parvus and Acartiella tortaniformis co-dominated the community and Bestiolina similis was the most abundant species. Post-Yass abundances of the cyclopoid copepods were considerably higher than the pre-Yass. Further, Oithona brevicornis replaced Bestiolina similisas the most abundant species of the community. Spatial heterogeneity of the copepod community of the pre-Yass period temporarily lost in the post-Yass. Changed species richness, abundances, dominance and spatial heterogeneity of the copepod community even for a short-term may have consequences for the ecology of the lower food web of an estuary. Keeping United Nations Ocean Decade (2021-2030) as the baseline, a nation-wide cyclone impact monitoring and resilience plan of the lower food web of Indian estuaries is recommended.

Diversity and dominance

Cyclopoid copepods

salinity

estuarine monitoring

Indian estuaries

Tropical cyclones (TCs) are discreate and destructive events that temporarily disrupts the lives and livelihoods of ecological communities (Needham et al. 2015). Researchers have focused on the genesis of TCs, causes and consequences of their rising intensities and frequencies across the world, and on their impacts on biodiversity (Woodruff et al. 2013; Kang & Elsner 2015; Mondal et al. 2022; Thompson et al. 2023). Lack of predictability of a TC track, immediate mobility of the scientific infrastructures and human resources following a TC are the barriers before cyclone research programme of estuaries unless regular institutional monitoring plans are in place (Rogers 2021; Paul et al. 2020a,b, 2023). Furthermore, estuaries are of diverse shapes, sizes, physical, chemical and biological attributes; therefore, an assessment of a TC mediated changes of a specific type of estuary (e.g., open river, intermittently open/close river, lagoon, tidal lakes) may not be accurate for other types of estuaries; therefore, to some extent such a monitoring plan has to have estuary type specific requirements (Whitfield 1992; Wetz & Yoskowitz 2013; Phlips et al. 2020). A few TC research programmes that are running in North America are tracking the impacts of the hurricanes on the estuaries and their inhabitants including biogeochemical cycles, plankton and other forms of lower food web for a considerably long period of time (Paerl et al. 2019; Walker et al. 2021). Cyclone research conducted in India, Sri Lanka, China, Taiwan, South Africa have studied the impacts of the TCs on different types of estuaries such as river-estuary, coastal lagoons, brackish lakes (Martin et al. 1992; Beyrend-Dur et al. 2013; Mishra et al. 2021; Xia et al. 2022). Those studies demonstrated many extreme and abrupt changes of the water quality of an estuary that follows a TC as well as the vulnerability of the various food web components including plankton that have triggered or could potentially trigger trophic cascades (Bhattacharya et al. 2014; Srichandan et al. 2015; Kumar et al. 2020; Paul et al. 2020a,b; Acharyya et al. 2021; Paul et al. 2023). A cyclone ecology research program of a river-estuary is rare (Paerl et al. 2019; Paul et al. 2023). Cyclone research of estuaries is mostly focused on intermittently open/close estuaries, coastal lagoons and tidal lakes (Srichandan et al. 2015; Xia et al. 2022; Thompson et al. 2023). Results of those research programs suggest that the intensity of the floods associated with a TC causes the major disruptions of the plankton communities and the windspeed of a TC has less to do with that (Peierls et al. 2003; Wetz & Paerl 2008). The distance to the landfall site of a TC does affect the extent of the disruption that a plankton community of an estuary may suffer after a TC (Kumar et al. 2017). Those observation may be less applicable for the plankton communities of a river-estuary such as the Ganges estuary (GE), India (Paul et al. 2020a,b, 2023).

The intensity of the TCs are increasing in the Bay of Bengal (BoB) and the region is possibly going to receive more frequent and intense cyclones in the 21 Century (Balaguru et al. 2014; Mondal et al. 2022). It is almost inevitable that in future the structures and functions of the estuarine communities of India would be stressed from the cyclone-mediated changes (Paul et al. 2020a,b, 2023). If the TCs are going to be frequent than the estuarine communities would have less time to recover the impacts of those TCs (Paul et al. 2020b); therefore, evaluations of such impacts on various scales (e.g., immediate (a few days), short-term (a few week to a month or so), medium-term (a few months to a few years) and long-term (decadal or more)) are essential for finding effective monitoring and management plans for the components of the lower food web of an estuary (Paul et al. 2023).

Indian estuaries are not institutionally monitored on a regular basis for research programs; therefore, medium to long-term datasets are absent (Paul et al. 2023, 2024). Considering those needs of the country, the ‘Cyclone Ecology (CE)’ was established on February 2019 on the GE (Paul et al. 2020a,b, 2023). That research programme runs on the Muriganga stretch of the GE and takes a before-after sampling approach considering the various categories of the TCs which landfall in the region (Paul et al. 2023). The Muriganga runs beside the Namkhana of West Bengal and it meets the BoB within a few kilometer; therefore, it is prone to face storm surges, depressions and TCs (Bhattacharya et al. 2014; Paul et al. 2020a,b, 2023). The CE programme uses the copepods as a model community and it studies the resilience and vulnerability of that community in face of a TC and/or successive TCs (Paul et al. 2020a,b, 2023). From the CE programme sites on the Muriganga 36 species of copepods are reported (Paul et al. 2019, 2024) on various occasions and among them Bestiolina similis, Acartiella tortaniformis, Pseudodiaptomus serricaudatus, Paracalanus parvus and Acartia spinicauda are estuarine specialists which persist throughout the year (Paul et al. 2019, 2023, 2024). The programme has already studied the impacts of the TCs such as the Fani (May 2019), BulBul (November 2019) and Amphan (May 2020) which had varying intensities (Category-2 to 5); those studies suggested that the copepod community of the Muriganga suffered from the mechanical forcing that follows a TC rather from the extreme and abrupt changes of the abiotic conditions (Paul et al. 2020a,b, 2023). Those observation also include a short-term depression of species richness and abundance of the copepod community (Paul et al. 2020a,b, 2023). Even within a few days to a few weeks after a TC mediated disruption those copepods recolonize their microhabitats in the Muriganga often led by estuarine specialists (Paul et al. 2020a,b, 2023). Their spatial niches are segregated only by a few hundred meter stretch of the Muriganga stretch of the GE (Paul et al. 2019, 2024). The TCs in the recent past such as the Aila (a Category-1 TC that landfall on 25 May 2009) severely affected the composition of the copepod community of the Indian Sundarbans (Bhattacharya et al. 2014). The Fani a Category-4 TC that landfall on Puri coast of Orissa about 350 K.M. away from the CE programme sites passed it on 5 May 2019 in capacity of a major depression (Paul et al. 2020b). The post-Fani destructions and floods were limited and the copepod community of the CE programme sites is less affected by that (Paul et al. 2020b). A Category-2 TC Bulbul landfall on 9 November 2019 on the Dhanchi forest of the Indian Sundarbans which is not far from the CE programme sites (Paul et al. 2020a). The post-Bulbul floods were limited and the copepod community of the CE programme sites recovered with a few weeks from its immediate decline of abundance and richness that followed shortly after the TC (Paul et al. 2020a). On the 20 May 2020, a Category-5 TC Amphan landfall only a few kilometer from the CE programme sites on the Muriganga and it caused severe destruction of the entire region as well as floods (Halder et al. 2021; Kumar et al. 2021; Paul et al. 2023). The copepod community composition, abundance and dominance hierarchy changed after the TC Amphan passed the CE programme sites and it took months to recover the state that existed before the Amphan; however, in some cases (e.g., dominance hierarchy) neo-normal ecological trends were observed (Paul et al. 2023, 2024).

The category-1 TC Yass landfall on 26 May 2021near the Dhamra Port of the Balasore region, Odisha state of India with a maximum sustained wind speed of 130–140 K.M./h gusting up to 155 K.M./hour (Paul & Chowdhury 2021). On the same day, after its landfall the TC Yass progressed towards the coastal regions of the West Bengal that include the CE programme sites.In that time the BoB sea surface temperature dropped about 3°C, salinity and density had raised by 1 psu and ~ 2 kg/m³, respectively (Varma et al. 2023). Indian Tide Table 2021 published by the order of the Surveyor General of India in 2020, predicted astronomical high tide on 26 May 2021 of Sagar Island (which is only a few kilometer from the CE programme sites) could reach as high as 5.71 meter. The TC Yass brought with it a high storm surge of 3.5 to 5 meters in the coasts of the Odisha and West Bengal and the tidal waves of height 1 to 2 meters above the astronomical tide were observed (Mondal et al. 2022; Varma et al. 2023). During that cyclonic period 11,405.21km² of the West Bengal’s coastal regions were inundated because about 1195 mm of rainfall occurred in short-time (Paul & Chowdhury 2021; Halder & Bandyopadhyay 2022). Within a short time, massive inundation occurred in the Namkhana (78.1 km²), Sagar Island (37.1 km²) and Kakdwip (32.6 km²) blocks of the South 24 Parganas of the West Bengal which are besides the GE and are close to CE programme sites and their 43.6%, 28.3% and 19.2% human populations, respectively were affected (Paul & Chowdhury 2021). The current study hypothesized that in short-term the copepod community structure is affected (in terms of diversity, dominance, distribution) by the TC Yass which may have consequences for the lower food web of the Muriganga stretch of the GE. This study would be useful for conceptualizing a short-term monitoring plan of the zooplankton community of the river-estuaries of India against a Category-1 TC.

Study site

The study was conducted from the CE programme sites (i.e., S1, S2 and S3) which have been established in February 2019 on the Muriganga stretch of the GE (Fig.1). The present study is a part of the monitoring of the CE programme sites so for the details related to study site see Paul et al. (2023).

Sampling during the pre- and post-Yass periods

The inundation that followed the TC Yass (landfall: 26 May 2021) caused a massive damage to infrastructure including roads to the Namkhana region of the West Bengal. The COVID-19 pandemic related lockdown had made it even more difficult to mobilise scientific resources immediately after the TC Yass. The sampling begun on 4 June 2021 and the sampling went till 22 June 2021. During that period the CE programme sites were sampled on 4 occasions (once in 6 days interval). Those are samples of the post-Yass period. On 21 November 2020, 29 January 2021 and 19 April 2021 water and copepod assemblages were sampled from the CE programme sites. During that period estuary was not perturbed by any TC for a considerable period. Those samples are assumed as the samples of the pre-Yass period.

Field sampling of water and copepods, and laboratory processes

Field sampling of the water and copepod assemblages related to the current study followed the similar methods which were deployed on the CE programme sites during the studies of the TC Fani, Bulbul and Amphan so for the details please refer to Paul et al. (2020a,b, 2023). By adopting the methods of the Paul et al. (2023) the copepod assemblages were collected in triplicate, preserved in 4% formalin and brought to the laboratory for species level identification by following Kasturirangan (1963) under the microscope (Bestscope-BS30T, China) and their abundances were expressed as individual(s) per cubic metre (i.e. ind.m^-3). On the each occasion of the field sampling abiotic parameters such as the salinity (PSU), water temperature (°C) and pH of the estuary were measured from the sub-surface water by a hand held multi-parameter probe (YSI-1030; YSI, USA).

Data structure, presentation and analysis

Abiotic data of the pre- and post-Yass periods are presented in Table 1. Diversity indices such as the Shannon-diversity and the dominance (i.e., Simpson index) and the Pielou’s evenness index were calculated by using the ‘vegan’ package (version 2.6-4) using CRAN-R 4.3.2 (R Core Team 2023). Site-specific relative abundances of the copepods during the pre- and post-Yass periods were calculated (Table 3). Ordination analysis (on species abundance data after square root transformation) was conducted. At first a cluster analysis was done (see annexure 1) of both the pre- and post-Yass data using PRIMER-e version 7 (Clarke & Gorle 2015). Then a Non-metric Multidimensional Scaling (NMDS) was conducted using the Bray–Curtis measure of dissimilarity (‘Vegan’ package version 2.5.6). Finally NMDS biplots (see Figure 2) of both the pre- and post-Yass periods were drawn using PRIMER-e version 7 (Clarke & Gorle 2015). Permutational Multivariate Analysis of Variance (PERMANOVA) was conducted (i.e. Adonis test, permutations = 999, method = Bray-Curtis, package: ‘Vegan’ version: 2.5.6) to evaluate the variability of the copepod assemblages among sampling sites. Such a test was performed separately for the pre- and post-Yass periods. For PERMANOVA an assumption of homogeneity of multi-variate dispersion was tested by conducting Analysis of variance (ANOVA). Similarity percentage analysis (i.e. SIMPER) were conducted for the assessment of similarity and dissimilarity of the copepod assemblages sampled in the pre-Yass and post-Yass periods using the package ‘Vegan’ version: 2.5.6 of the CRAN-R 4.3.2 (R Core Team 2023).

Abiotic conditions of the CE program sites

During the pre-Yass period the salinity regime of the Muriganga was in between mesohaline to polyhaline ranged from 7.50 to 17.90 (Table 1). After the TC Yass the salinity of the Muriganga remained consistently in the polyhaline zone (ranged 15.90 to 20.80) for a few weeks (Table 1). Both in the pre- and post-Yass the pH of the Muriganga mostly remained slightly alkaline (Table 1). The water temperature in the post-Yass period varied within a narrow range i.e., 29.10 to 31.20°C; however, on the occasions of the pre-Yass sampling a considerable variability (range 21.40 to 30.30°C) of the water temperature was observed (Table 1).

Copepod community structure and its changes

Irrespective of the sampling sites, in the post-Yass period the species richness of the copepod community was higher than the pre-Yass period (Table 2). During the pre-Yass the species richness ranged 17 to 20 whereas in the post-Yass that was 20 to 24 (Table 2). Consequently, in the post-Yass period the Shannon Diversity, Simpson dominance and Pielou’s evenness indices of the copepod community showed higher values in comparison to the pre-Yass period (Table 2). In respect to relative abundance, during the pre-Yass period copepod species such as the Bestiolina similis, Paracalanus parvus and Acartiella tortaniformis co-dominated the community and among them Bestiolina similis was the most abundant species contributing up to 20.52% of the total community (Table 3). After the TC Yass, Bestiolina similis, Paracalanus parvus, Acartiella tortaniformis and Acartia spinicauda co-dominated the copepod community by virtue of their higher relative abundances but a noticeable decline in the relative abundances were observed for Bestiolina similis, Paracalanus parvus and Acartiella tortaniformis (Table 3). Post-Yass relative abundances of Canthocalanus pauper, Temora turbinata, Corycaeus crassiusculus Dana and different species of Oithona were higher than the pre-Yass period (Table 3). In the post-Yass period the copepod species that dominated the community in terms of its relative abundance is Oithona brevicornis (Table 3). Species such the Labidocera euchaeta and Oithona nana were not present in the copepod assemblages which were sampled in the pre-Yass period but those species were present in the post-Yass period (Table 3). During pre-Yass copepods of the Paracalanidae (cumulative abundance 49 to 59 %) family dominated the community followed by Acartiidae (cumulative abundance 27 – 33 %) and Oithonidae (cumulative abundance 3 – 8 %). After Yass Paracalindae contribution decreased to 28 to 35% and Acartiidae decreased to 17 to 29%; however, Oithonidae increased significantly to13 to 19% of the total copepod abundance. The Shannon diversity index correlating with species number also showed the trend of increased diversity in post- Yass period in all the three sites (Table 2). The NMDS analysis and the biplot of the pre-Yass period revealed the site specific variability of the copepod assemblages (Fig.2), which was found to be significant (PERMANOVA: DF = 2, Pseudo-F = 17.66, R² = 0.85, P = 0.005; homogeneity of multivariate dispersion test ANOVA: DF = 2, F = 0.4, P = 0.95). On contrary, the NDMS and the biplot (Fig.2) suggested that during the post-Yass period the spatial variability of the copepod assemblages of the Muriganga was not significant (PERMANOVA: DF = 2, Pseudo-F = 0.41, R² = 0.08, P = 0.95; homogeneity of multivariate dispersion test ANOVA: DF = 2, F = 0.28, P = 0.76). Results of the SIMPER analysis suggested that in the pre-Yass the average similarity of the copepods sampled on various occasions was 37.04% (chiefly contributed by the species such as B. similis 18.94%, P. parvus 17.82% and A. tortaniformis 14.83% and A. spinicauda 10.35%). Results further showed that the average similarity within the copepod assemblages did rise to 77.09% in the post-Yass period (chiefly contributed by the species such as A. tonsa 10.7%, O. similis 9.43; P. parvus 8.56% and A. longicornis 8.13%). Further, the average dissimilarity between the copepod assemblages sampled in the pre-and the post-Yass periods was 66.21% chiefly contributed by the species such as A. tonsa 10.84%, O. similis 9.34; A. longicornis 7.74% and B. similis 6.98%.

Habitat conditions during the pre- and post-Yass periods

Results of the abiotic variability demonstrated that the Muriganga stretch of the GE is a true estuary, which agree with previous studies conducted in the region (Mukhopadhyay et al. 2006; Chowdhury et al. 2015; Bhattacharya & Paul 2023; Paul et al. 2024). Due to the large influx of freshwater from the upstream of the Muriganga, it often remains mesohaline (Mitra et al. 2009; Paul et al. 2019; Bhattacharya & Paul 2023; Paul et al. 2024). Shortly after TC Yass, salt water intrusion from the adjacent Bay of Bengal had turned the estuary from a mesohaline to a polyhaline one and the estuary maintained such a characteristics for a few weeks which was not observed after TC Fani, Bulbul and Amphan (Paul et al. 2020a,b, 2023, 2024). After TC Aila the Muriganga did remain polyhaline for a considerable time (Mitra et al. 2011; Bhattacharya et al. 2014). The Muriganga experiences macro-tidal environment and its pH profile remains slightly alkaline throughout the year unless there is an excessive rain for a few days which lowers the pH specially in monsoon (Chowdhury et al. 2015; Paul et al. 2024). Even after TC Yass, alkalinity of the estuary remained higher. High alkaline condition of the Muriganga was observed after the TC Phailin which caused sudden influx of salt near the mouth of the estuary (Das et al. 2016). The water temperature of the Muriganga follows the typical seasonal characteristics of a tropical estuary (Mukhopadhyay et al. 2006; Chowdhury et al. 2015; Paul et al. 2024). Post-Yass the water temperature of the Muriganga did not exhibits any drastic change. Absence of drastic change in water temperature of the Muriganga was also not observed after the TC Fani, Bulbul and Amphan (Paul et al. 2020a,b, 2023). Such was the case for TC Domoina which hit the lake St. Lucia and northern estuarine systems of the Natal, South Africa (Forbes & Cyrus 1992). On contrary, a considerable decline in the water temperature of the Muriganga was observed within a few days after the TC Aila (Bhattacharya et al. 2014). Previous studies on the TCs conducted on the lagoons, tidal lakes and intermittently open/close estuaries of India and across the world have suggested that a sudden change of the salinity regime of an estuary could influence diversity and distribution of its biological communities including the copepods (Forbes & Cyrus 1992; Reay & Moore 2005; Mitra et al. 2011; Beyrend-Dur et al. 2013; Bhattacharya et al. 2014; Srichandan et al. 2021; Mishra et al. 2023a,b; Thompson et al. 2023). It was also suggested that the post-cyclone flood often exert mechanical forcing which subsequently temporarily disrupts plankton communities (Srichandan et al. 2021; Paul et al. 2023).

Copepod community of the pre- and post-Yass periods

Post TC Yass the number of species increased within the sampled copepod assemblages, the community had more cyclopoid copepods than the pre-Yass period. Species such as the A. tortaniformis had replaced the B. similis as the most dominant species of the copepod community, and the abundances of a few dominant species such as P. parvus, A. spinicauda had considerably declined. The O. brevicornis abundance had risen in the post-Yass period, and the species such as L. euchaeta and O. nana were observed in the post-Yass period which were absent in the pre-Yass period. It is, therefore, evident that in short-term the copepod community of the Muriganga is impacted and underwent several changes. Those changes in the community structure of the copepods of the Muriganga were not observed after TC Fani, Bulbul and Amphan (Paul et al. 2020a,b, 2023). The Oithona are generally omnivores that mostly eat organic debris, dinoflagellates, diatoms, and proto-zooplankton (Pond & Ward 2011; Wang et al. 2017). The sudden increment of Oithonidae family in the post- Yass samples could be attributed to the increased organic debris in the water which is common after a TC (Bhattacharya et al. 2014). The increased number of Oithonidae family is mainly due to the increment of O. brevicornis abundance in the post-Yass samples, such a phenomenon was observed after cyclone “Aila” (Bhattacharya et al. 2014) but not after TC Fani, Bulbul and Amphan (Paul et al. 2020a,b, 2023). The dominance of Oithonidae suggested their high adaptability to trophic and hydrologic conditions in the post- Yass period. After each of the TC Aila, Fani, Bulbul and Amphan there were an immediate decline in the species richness and the total abundance of the copepods (Paul et al. 2020a,b, 2023). Within a week or so after TC Fani and Bulbul about 50% of the species richness recovered (Paul et al. 2020a,b). Decline in the total abundance of the copepod community as well as in the abundances of the individual species is not that uncommon after a TC mediated disruption of estuaries of India, South Africa and Taiwan (Forbes & Cyrus 1992; Lopez-Lopez et al. 2012; Beyrend-Dur et al. 2013; Bhattacharya et al. 2014; Srichandan et al. 2021). Results of the NMDS and SIMPER analysis suggested that the TC Yass for a while had washed away some of the spatial heterogeneity within the copepod community that existed in the pre-Yass period. This is not unexpected because floods and or incessant rainfall (often associated with a TC) often temporarily wash way environmental gradients of an estuary and impact the spatial niche segregations of many estuarine biota including plankton (Payne et al. 2015, Nandy et al. 2018); therefore, the community becomes more homogenous at least for a short-term (Paul et al. 2023). Later when the environmental gradients become again prominent in an estuary that in consequence help many estuarine specialist copepods to recolonize their vacant spatial niches (Paul et al. 2020a,b, 2023).

Cyclone ecology research of Indian estuaries

In total 61 TCs of various intensities have disrupted the nine coastal states of India from 2006 to 2020; the highest numbers were recorded in Odisha (20), West Bengal (14) and Andhra Pradesh (11) (Kantamaneni et al. 2022). The cyclone ecology research of the Indian estuaries is relatively new as its roots could be traced in last two decades (Kumar et al. 2010; Joseph et al. 2011; Mitra et al. 2011; Mukherjee et al. 2012; Bhattacharya et al. 2014; Kumar et al. 2017). Literature is mostly focused on Indian Sundarbans, West Bengal and on the estuaries (e.g., Chilika lagoon) of Odisha (Mitra et al. 2011; Mukherjee et al. 2012; Bhattacharya et al. 2014; Paul et al. 2020a,b, 2023; Kumar et al. 2017; Srichandan et al. 2021; Mishra et al. 2023a,b). Little is known about the impact of TCs on the ecology of other estuaries, backwaters and lagoons of India (Joseph et al. 2011; Mangesh et al. 2016; Gunasekaran et al. 2021; Sachithanandam et al. 2022). Traditionally, the frequency of cyclones in India is higher on the eastern coast than on the western coast; however, in the recent years, the frequency of cyclones over the Arabian sea is on the rise (Baburaj et al. 2021; Kar & Banerjee 2021); therefore, cyclone ecology research would become more relevant than ever for Indian estuaries. India has no institutional mechanism placed for regular monitoring of its estuaries for cyclone-mediated changes (Paul et al. 2019, 2020a,b, 2023). Except the Chilika lagoon and mangrove estuaries of Indian Sundarbans including the GE, drawing a baseline for different types of Indian estuaries and predicting their fates facing TCs; therefore, are difficult. The other major issue is the previous studies conducted in India and elsewhere have documented the disturbance and recovery of estuaries from one or a few locations or storm events, limiting generalizations about the TC impacts and characteristic patterns of ecosystem response and recovery (Buelo et al. 2024). Considering the scarcity of scientific resources, unpredictability of a TC track and mobilization of scientific infrastructure and human resources immediately after a TC or successive TCs there shall be focus on geo-spatial science and remotely operated in-situ recordings and periodic ecological surveys for monitoring the baselines and stochastic disturbances of Indian estuaries (Mishra et al. 2023a; Paul et al. 2023; Varma et al. 2023). The Sundarbans (including the GE), Chilika lagoon, Godavari estuary, Cochin-estuary, Mandovi-Zuari estuary are some of the iconic estuaries of India that are serving millions of Indians daily by providing ecosystem services (Sarkar & Bhattacharya 2003; Bhavan et al. 2023). Those services may get seriously jeopardised if the lower food web of the Indian estuaries are strained from the periodic TCs (Paul et al. 2020a; Mishra et al. 2021; Rasquinha & Mishra 2021; Mishra et al. 2023a). United Nations Ocean Decade (2021–2030) may serve as the baseline to initiate a cyclone impact monitoring and resilience plan of the lower food web of Indian estuaries.

Acknowledgements

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 the 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. Dr. Paul thanks 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).

Financial Support

DST Inspire Faculty Award [Sanction no: DST/INSPIRE/04/2016/0000036] of the Government of India met fellowship of Dr. Sourav Paul and partial funding the research. 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 met the fellowship of Mr. Karan and partial funding for the research. Estuarine and Coastal Studies Foundation, India provided financial assistance to Dr. Bhaskar Deb Bhattacharya during the course of the study.

Competing interest

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

Ethical approval

No ethical standards were required to execute the study.

Data availability

Data would be provided with a reasonable request for non-commercial purpose.

Author Contributions

Sourav Paul: Conceptualization,Methodology,Formal analysis and investigation,writing original draft, writing - review and editing, Funding acquisition, Resources, Supervision; Samya Karan: Methodology; Bhaskar Deb Bhattacharya: Methodology, writing - review and editing.

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Tables 1 to 3 are available in the Supplementary Files section

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Changes of the copepod community of Ganges estuary following tropical cyclone Yass

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Abstract

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Introduction

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Discussion

Habitat conditions during the pre- and post-Yass periods

Copepod community of the pre- and post-Yass periods

Cyclone ecology research of Indian estuaries

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References

Tables

Additional Declarations

Supplementary Files

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