Article

Differential Impact of Anniversary-Severe Cyclones on the Water Quality of a Tropical Coastal Lagoon

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Abstract

Mapping spatio-temporal dynamics of suspended load in a lagoon before-during-after a cyclone is crucial for monitoring sudden nutrient enrichment and associated processes such as algal blooms and siltation. However, not all cyclones produce similar impact on a coastal lagoon, some trigger algal blooms after passage while others just increase the overall turbidity. Asia’s largest brackish water lagoon, Chilika Lagoon, India was hit by two anniversary-severe cyclones Phailin (12 October 2013) and Hudhud (12 October 2014) recently. Their impacts were analysed with respect to physical, biological and meteorological factors which favour or restrict a phytoplankton bloom after the passage of a storm. Moderate-resolution imaging spectroradiometer surface reflectance data were used to examine the spatio-temporal variability in total suspended sediment (TSS) and chlorophyll-a (Chl-a) concentration pre- and post-cyclone. Comparative results revealed that Phailin was associated with higher rainfall, wind speed and surface runoff compared with Hudhud. These factors contributed to higher TSS concentration in all sectors of the lagoon post-Phailin compared with post-Hudhud. Extreme TSS, limited light, high rainfall and runoff and increased flushing rate post-Phailin restricted the likelihood of a phytoplankton bloom in the lagoon, a commonly reported phenomenon after the passage of a cyclone. In contrast, sufficient light availability due to lower TSS, low runoff and flushing and stable wind supported a phytoplankton bloom post-Hudhud. The observed differential impacts were linked to the individual cyclone’s characteristics such as differences in landfall locations, wind speed, trajectory after the landfall, differences in rainfall rate and surface runoff and speed of passage.

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... These are one of the most biologically productive ecosystems on the earth due to their unique geophysical positioning between the riverine and marine ecosystems. The high nutrient inputs from surface run-off and river discharge as well as from autochthonous sources results high productivity in coastal lagoon and at the same time make them highly vulnerable to the environmental changes caused by anthropogenic and natural disturbances (Lloret et al., 2008;Kumar et al., 2017). Hydrology of a coastal lagoon is influenced by the river discharge, tidal flux, evaporation, precipitation, and extreme climatic events such as cyclones (Anthony et al., 2009;Kumar et al., 2017). ...
... The high nutrient inputs from surface run-off and river discharge as well as from autochthonous sources results high productivity in coastal lagoon and at the same time make them highly vulnerable to the environmental changes caused by anthropogenic and natural disturbances (Lloret et al., 2008;Kumar et al., 2017). Hydrology of a coastal lagoon is influenced by the river discharge, tidal flux, evaporation, precipitation, and extreme climatic events such as cyclones (Anthony et al., 2009;Kumar et al., 2017). Of these, seasonal changes in the riverine flow and its concurrent mixing with seawater are key factors which control the biota and biogeochemistry of estuarine coastal lagoons. ...
... This lagoon is currently experiencing an intense pressure from different anthropogenic activities such as aquaculture, domestic sewage discharge from surrounding villages, and water pollution from mechanized boats used in fishing and tourism activities (Mohanty et al., 2016). In addition, the lagoon is also severely impacted by cyclones such as Phailin (12 October 2013), Hudhud (12 October 2014), Titli (11 October 2018), and Fani (3 May 2019) which frequently originate in the Bay of Bengal (BoB) (Srichandan et al., 2015a;Kumar et al., 2017;Barik et al., 2017). To assess the impact of different anthropogenic and natural pressures on the zooplankton communities, a comprehensive baseline assessment of their spatiotemporal variability in relation to environmental variables is a prerequisite. ...
Article
Zooplankton communities in response to hydrological (salinity, turbidity, water temperature, nitrate, phosphate, silicate) and biological (phytoplankton density) variables were studied in the Asia’s largest brackish water lagoon, Chilika (India). Water samples were collected from 13 stations on a monthly frequency between July 2014–June 2015. A total of 141 species of holoplankton including Ciliophora, Foraminifera, Rotifera, Rhizopoda, Gastropoda, Cladocera, Copepoda, Ostracoda, Malacostraca, Chaetognatha, Chordata, Nematoda, and 18 types of planktonic larvae were identified. Copepods were the most dominant and diverse zooplankton in terms of their species richness, numerical abundance, and widespread distribution in the lagoon. The major holoplanktonic taxa were Acartia sp., Acrocalanus gibber, Acrocalanus gracilis, Acrocalanus longicornis, Euterpina acutifrons, Lecane sp., Oithona sp., Pseudodiaptomus serricaudatus, and Tintinnopsis tubulosa. The dominant planktonic larvae were bivalve veliger, copepod nauplii, cyphonautes larvae, gastropod veliger, and protozoea of lucifer. Canonical correspondence analysis showed that distribution of zooplankton assemblages was influenced by salinity, turbidity, and phytoplankton density. Indicator analysis demarcated 26 indicator zooplankton taxa. Of these, the most prominent indicator zooplankton such as Belzebub hanseni, Mesopodopsis orientalis, Chydorus sphaericus, and Corycaeus catus were characteristic to salinity gradient in southern sector, sediment resuspension in central sector, eutrophic conditions in northern sector, and intrusion of inshore forms in outer channel, respectively. Hudhud, a category 4 cyclone resulted decline in the abundances of zooplankton population. Copepod nauplii and copepodites were dominant during post-Hudhud and their succession was linked to the increased phytoplankton density due to an upsurge in the nutrient level in the northern sector of the lagoon. The present study provided a comprehensive detail on the zooplankton composition and their environmental drivers including the impact of a tropical cyclone from a tropical coastal lagoon system.
... The water quality variations in coastal aquatic ecosystems can be attributed to upland anthropogenic activities and natural processes such as changes in precipitation and river discharge, and extreme hydrometeorological events such as cyclones or hurricanes and storms (Mallin et al., 2006;Chu et al., 2011;Wang et al., 2012;Miller et al., 2019). Cyclones can produce a wide variety of ecological impact on a coastal lagoon (Mallin et al., 2002;Havens et al., 2011;Srichandan et al., 2015;Angles et al., 2015;Kumar et al., 2017;Muduli et al., 2017;Stockwell et al., 2020). The type of changes in water quality and the subsequent effect on the lagoon after the landfall depends on several physical, ecological, and meteorological factors such as the location of landfall from the lagoon, strength, and speed of the cyclone, the extent of damage to vegetation upland, trophic status of the lagoon at the time, magnitude of storm surge and runoff, and finally, the geographic-geomorphologic-bathymetric setting of the lagoon (Mallin et al., 2002;Havens et al., 2011;Huang et al., 2011;Wang et al., 2012;Srichandan et al., 2015;Angles et al., 2015;Kumar et al., 2017;Miller et al., 2019). ...
... Cyclones can produce a wide variety of ecological impact on a coastal lagoon (Mallin et al., 2002;Havens et al., 2011;Srichandan et al., 2015;Angles et al., 2015;Kumar et al., 2017;Muduli et al., 2017;Stockwell et al., 2020). The type of changes in water quality and the subsequent effect on the lagoon after the landfall depends on several physical, ecological, and meteorological factors such as the location of landfall from the lagoon, strength, and speed of the cyclone, the extent of damage to vegetation upland, trophic status of the lagoon at the time, magnitude of storm surge and runoff, and finally, the geographic-geomorphologic-bathymetric setting of the lagoon (Mallin et al., 2002;Havens et al., 2011;Huang et al., 2011;Wang et al., 2012;Srichandan et al., 2015;Angles et al., 2015;Kumar et al., 2017;Miller et al., 2019). There are many studies, some cited above, which reported a variety of impact of a cyclone on coastal waters from an immediate exponential increase in the total suspended matter (TSM) to a severe algal bloom and everything in-between. ...
... Equation R (Kumar et al., 2016;Kumar et al., 2017). Because of these seasonal and sectoral gradients in the physicochemical factors of the lagoon, the impact of the cyclones on the lagoon was quite contrasting. ...
Article
Cyclones can produce a wide variety of short-term and long-term ecological impacts on coastal lagoons depending on cyclone’s physical-meteorological characteristics and the lagoon’s geographic, geomorphic, and bathymetric characteristics. Here, we theorized that in monsoon regulated tropical coastal lagoons, another important factor that could determine the impact of a cyclone is the landfall season or time of the year with reference to the monsoon season. We analyzed the impact of two cyclones which made landfall near Chilika, Asia’s largest brackish water lagoon in different seasons, Cyclone Fani and Titli before and after the monsoon season. We compared field measured and satellite-derived water quality parameters including nutrient, salinity, water temperature, transparency, Chlorophyll-a (Chl-a), total suspended matter (TSM), and colored dissolved organic matter (CDOM) before and after the cyclones. We found that although both the cyclones were of similar intensities, after their land interaction, their impact on the lagoon’s water quality was contrasting. The post-monsoon cyclone produced a substantial increase in total nitrogen (TN) and total phosphorous (TP), a large drop in salinity, CDOM, and Chl-a. In contrast, after the pre-monsoon cyclone, TN and TP did not show any such hike, no substantial change in salinity and CDOM either, and only a slight increase in Chl-a was observed. We found that the controlling factor in determining the impact of a cyclone is the rate and duration of freshwater discharge to the lagoon, which is normally a strong pulse for pre-monsoon and a continued high flow for post-monsoon cyclones. We conclude that the antecedent conditions of the lagoon and the watershed at the time of a cyclone’s landfall is a key criterion in determining the impact. The combined use of satellite data and field data was proved critical to capture the overall impact of cyclones on the hydrological characteristics of the monsoon-regulated coastal lagoon.
... Cyclones are discrete events that can disrupt an estuary and its plankton community by drastically altering the physicochemical environment and/or altering the natural equilibrium of the top-down processes of a food web (Bhattacharya et al. 2014;Zink et al. 2020). After a cyclone, the ecological processes that regulate the structural and functional stability, diversity and productivity of the recovering planktonic food web are more likely to be bottom-up than top-down (Paerl et al. 2001;Kumar et al. 2017;Paul et al. 2020). Cyclones have abruptly changed the bottom-up processes and in consequence affected diversity and distribution of copepods in the tropical estuaries of India, South Africa and Taiwan (Bhattacharya et al. 2014;Forbes and Cyrus 1992;Beyrend-Dur et al. 2013). ...
... In 2009, cyclone Aila drastically changed the water quality of the mangrove estuaries of the Indian Sundarban, rendering the system highly turbid and oligohaline for a few months, leading to a temporary, but a major depression of mesozooplankton and fish diversity with only a few estuarine specialist species being able to adapt to such drastic changes of habitat (Mukherjee et al. 2012;Bhattacharya et al. 2014). The northern and eastern coasts of the Bay of Bengal (BoB) are occasionally affected by cyclones (Bhattacharya et al. 2014;Kumar et al. 2017 (Bhattacharya et al. 2014;Srichandan et al. 2015;Seo and Bakkensen 2017). Extremely severe cyclonic storm cyclone Fani (wind speed reaching 250 km/h (sustained for 1 min)) made landfall on the Orissa coast of India on 3 May 2019 with a wind speed of 175 km/h (Nandi 2019). ...
... India has no institutionalized monitoring program in place for following cyclone-mediated ecological changes of its estuaries (Paul et al. 2020). So, only a few ecological studies have ever reported consequences of cyclones on estuarine mesozooplankton (Bhattacharya et al. 2014;Kumar et al. 2017). These studies suggest that the intensity of a cyclone-mediated disruption of mesozooplankton community largely depends on the distance from the landfall site of a cyclone and cyclone-associated rainfall (Kumar et al. 2017;Paul et al. 2020). ...
Article
Full-text available
A cyclone temporarily disrupts copepod community structure of an estuary, and during the com- munity rebuilding process, omnivorous copepods dom- inate. This hypothesis was tested after cyclone Fani affected the Ganges River estuary of India on 5 May 2019. Copepod assemblages and environmental parameters were collected before (25 February 2019), after (24 August 2019) and immediately after (daily between 8 and 14 May 2019) cyclone Fani from three sites of the estuary. Immediately after cyclone Fani, spatial heterogeneity of the estuarine environment was washed away, salinity and temperature levels of the estuary increased, pH level declined, while the total dissolve solids remained constant at high levels of con- centration. Copepod diversity and abundance were dras- tically reduced by cyclone Fani with the exception of the omnivorous Bestiolina similis, which tolerated a wide variability of the environment and dominated the com- munity. Led by small and medium-sized copepods, within days, the community recovered from its initial disruption. Immediately after cyclone Fani, medium- sized omnivorous copepod Acartiella tortaniformis became the second most abundant species replacing the small-sized herbivorous Paracalanus parvus. Changes in species composition and abundance hierarchyobserved immediately after cyclone Fani lasted for a few months. The intensity of cyclones is increasing in the Indian Sundarban; therefore, following a cyclone, more severe and prolong disruptions of the copepod community are likely. Institutionalized monitoring of the cyclone-mediated ecological changes of the Ganges River estuary is therefore strongly recommended.
... The increasing number and intensity of tropical cyclones can mean shorter recovery times for impacted estuarine communities (Pearl et al., 2018;Wachnicka et al., 2020). Understanding of the ecological response of estuaries to a tropical cyclone or successive tropical cyclones is limited (Forbes and Cyrus, 1992;Pearl et al., 2001;Bhattacharya et al., 2014;Kumar et al., 2017). Few studies have tracked the immediate and long-term ecological effects of successive cyclones on large river estuaries of tropics (Beyrend-Dur et al., 2013). ...
... Few studies have tracked the immediate and long-term ecological effects of successive cyclones on large river estuaries of tropics (Beyrend-Dur et al., 2013). Tropical cyclone induced disruption of estuarine plankton community may result in a trophic cascade, as observed after Cyclone Tiffany in Australia, Cyclone Isabel in USA, Cyclone Domonia in South Africa and Cyclone Phailin in India (Forbes and Cyrus, 1992;McKinnon et al., 2003;Wetz and Pearl, 2008;Kumar et al., 2017). After Cyclone Aila, mangrove estuaries of Indian Sundarban turned oligohaline and highly turbid for a few months, which disrupted the mesozooplankton community (including many copepods) with few estuarine specialist species maintaining their population stability (Bhattacharya et al., 2014). ...
... (Beyrend-Dur et al., 2013). Habitat-scale changes even if temporary can trigger trophic cascades starting from the plankton, with the extent of change depending on the intensity, place of landfall and associated rainfall of a tropical cyclone, and the interval between successive tropical cyclones (Kumar et al., 2017;Paerl et al., 2018). After a tropical cyclone generally top-down ecological processes become limited because many predators disperse or perish or both, and the high environmental variability that follows a tropical cyclone mainly drives community processes of a tropical estuary (Forbes and Cyrus, 1992;Beyrend-Dur et al., 2013;Bhattacharya et al., 2014;Kumar et al., 2017). ...
Article
Excessively large river estuaries of tropics can be impacted within months by successive tropical cyclones. The effect of these disruptions on the community ecology of such estuaries has been scarcely examined. On a daily basis for a week, the copepod community of the Ganges River estuary of India, was studied immediately after Cyclone Fani and Cyclone Bulbul in May and November 2019, respectively. The objective was to understand the ecological response of the copepod community of the Ganges River estuary facing successive extreme environmental changes in short interval. Differences in landfall sites and the amount of rain associated with each tropical cyclone led to different degrees of temporal changes of salinity, pH, and water-temperature of the estuary which might have caused the observed addition-deletion of species, rearrangements of abundance-hierarchy and expansion-shrinkage of omnivore-herbivore feeding guilds of the copepod community. The copepod Bestiolina similis maintained, however, its numerical dominant status. Tropical cyclone driven changes to the copepod community of an estuary may be temporary but the changes may affect benthic-pelagic linkages. Following an extreme environmental change (e.g. cyclone, flood), an institution-backed monitoring (mix of high to low in- tensity sampling lasting for a few hours to years) with matching scales of zooplankton and biogeochemical data collection, encompassing freshwater and marine dominated sections of the Ganges River estuary is recommended. Nations bordering the Indian Ocean may consider a similar recommendation for monitoring their es- tuaries after any extreme environmental change, taking account of locale-specific modifications, and initiate a regional programme of estuaries on the United Nations Decade of Ocean (2020–2030) by collaborating through inter-governmental platforms.
... The lagoons are highly dynamic ecosystems due to continuous material influxes (dissolved and particulate) from both marine and terrestrial environments (Mitsch and Gosselink 1993). In global context, the lagoons are stressed by both natural (e.g., extreme climatic events) and anthropogenic pressures (e.g., eutrophication, sewage discharge, and overfishing) (Kumar et al. 2016;Arreola-Lizarraga et al. 2016). These natural and anthropogenic pressures on coastal lagoons along with mixing of water from riverine and marine sources yield a sharp gradient in the physicochemical factors which determine the zooplankton community composition and distribution over the spatiotemporal scales. ...
... Chilika also experiences different salinity regimes in different sectors such as oligohaline (NS: 0.5-5), mesohaline (CS and SS: 5-18), and polyhaline (OC: 18-30) (Muduli and Pattnaik 2020). In addition, extreme weather events such as Phailin (October 12, 2013) and Hudhud (October 12,2014) have been shown to cause variability in nutrient molar ratios and phytoplankton biomass leading to proliferation of blooms (Kumar et al. 2016;Srichandan et al. 2015b). ...
Chapter
Zooplankton constitutes a pivotal component in the pelagic food webs and serves as the major source of fish diet, thereby determining the productivity of coastal fisheries. Therefore, understanding zooplankton diversity and their ecology in coastal lagoon settings is a high priority research area. We examined the spatiotemporal distribution of zooplankton diversity (size >120 μm) in relation to environmental variables in Chilika lagoon. The sampling was conducted on the monthly frequency from July 2012 to June 2016 from 13 locations and identified a total of 186 zooplankton taxa which included 131 as first record from the Chilika lagoon. To date, a total inventory of 263 species of holoplankton represented by 16 diverse categories of organisms, namely, Ciliophora (51), Foraminifera (13), Tubulinea (5), Rotifera (42), Hydrozoa (1), Ctenophora (1), Nematoda (1), Polychaeta (3), Gastropoda (12), Bivalvia (5), Cladocera (13), Copepoda (95), Ostracoda (4), Malacostraca (13), Chaetognatha (2), and Chordata (2), and 23 types of meroplankton were identified. Chilika lagoon exhibited a significant variation in salinity (0–35.5) at spatiotemporal scale and consisted of marine, brackish, and freshwater zooplankton along the estuarine salinity gradient. Copepods emerged as one of the most dominant and diverse zooplankton groups in terms of species richness, abundance, and widespread distribution. Among the four orders of Copepoda (i.e., Calanoida, Cyclopoida, Harpacticoida, and Poecilostomatatoida), Calanoida was the most abundant one. An important component of total zooplankton pool, i.e., microzooplankton (20–200 μm), was also examined in relation to environmental variables. Ciliophora dominated the microzooplankton community followed by copepod nauplii and Rotifera, except in the freshwater zone of the lagoon. Foraminifera, cirripede nauplii, gastropod veliger, and bivalve veliger were minor contributors in microzooplankton. Salinity and phytoplankton abundances were the major factors influencing microzooplankton community composition. The present study highlighted the necessity of a long-term systematic monitoring of zooplankton diversity and composition in Chilika lagoon.
... This Ramsar site (no. 229) is experiencing frequent natural hazards (e.g., cyclones) and anthropogenic pressures (e.g., dredging, aquaculture, tourism, and disposal of sewage and solid waste) (Kumar et al., 2017;Mohanty et al., 2017). In the past few years, the occurrence of Cyanophyta blooms has become common in Chilika Lagoon, especially in dry season when the water temperature and nutrient load are high (Chilika Development Authority -CDA, Monitoring Records 2017). ...
... Besides the usual salinity gradient in the lagoon, which is tightly coupled with spatial and seasonal factors, acute or pulse disturbances such as cyclones can temporarily eliminate the pre-existing environmental gradients affecting phytoplankton distribution and community structure (Srichandan et al., 2015b;Mishra et al., 2021). Notably, on 12th October 2013, Phailin, a category-5 Very Severe Cyclonic Storm, made landfall at a distance of 45 km southwest of the Chilika Lagoon (Kumar et al., 2017). Exactly, a year after the Phailin, i.e., on 12th October 2014, a category-4 tropical cyclone, Hudhud made landfall at a distance of 338 km southwest of Chilika Lagoon. ...
Article
Spatial and seasonal heterogeneity in phytoplankton communities are governed by many biotic and abiotic drivers. However, the identification of long-term spatial and temporal trends in abiotic drivers, and their interdependencies with the phytoplankton communities’ structure is understudied in tropical brackish coastal lagoons. We examined phytoplankton communities' spatiotemporal dynamics from a 5-year dataset (n = 780) collected from 13 sampling stations in Chilika Lagoon, India, where the salinity gradient defined the spatial patterns in environmental variables. Generalized additive models showed a declining trend in phytoplankton biomass, pH, and dissolved PO4 in the lagoon. Hierarchical modelling of species communities revealed that salinity (44.48 ± 28.19%), water temperature (4.37 ± 5.65%), and season (4.27 ± 0.96%) accounted for maximum variation in the phytoplankton composition. Bacillariophyta (Indicator Value (IV): 0.74) and Dinophyta (IV: 0.72) emerged as top indicators for polyhaline regime whereas, Cyanophyta (IV: 0.81), Euglenophyta (IV: 0.79), and Chlorophyta (IV: 0.75) were strong indicators for oligohaline regime. The responses of Dinophyta and Chrysophyta to environmental drivers were much more complex as random effects accounted for ~70–75% variation in their abundances. Prorocentrum minimum (IV: 0.52), Gonyaulax sp. (IV: 0.52), and Alexandrium sp. (IV: 0.51) were potential indicators of P–limitation. Diploneis weissflogii (IV: 0.43), a marine diatom, emerged as a potential indicator of N–limitation. Hierarchical modelling revealed the positive association between Cyanophyta, Chlorophyta, and Euglenophyta whereas, Dinophyta and Chrysophyta showed a negative association with Cyanophyta, Chlorophyta, and Euglenophyta. Landsat 8-Operational Land Imager satellite models predicted the highest and lowest Cyanophyta abundances in northern and southern sectors, respectively, which were in accordance with the near-coincident field-based measurements from the lagoon. This study highlighted the dynamics of phytoplankton communities and their relationships with environmental drivers by separating the signals of habitat filtering and biotic interactions in a monsoon-regulated tropical coastal lagoon.
... Although these processes have been previously documented in isolation (e.g., Kumar et al., 2017;Paerl et al., 2001;Tanner et al., 1991), Maria's impact on Puerto Rico presents a unique, though unfortunate, opportunity to holistically study the hydropshere's atmospheric, terrestrial, and marine components as the land surface recovers. Thus, this paper will describe the coevolution of hydrological processes across all three components of the Puerto Rico Earth system (land, sea, and air) following Maria's mass defoliation. ...
... The 2.2-times TSM increase within Puerto Rico's estuaries corresponds well to previous hurricane-related sediment suspension studies. For instance, Kumar et al. (2017) found that TSM in a coastal lagoon increased~2.5 times following the landfalls of Cyclones Hudhud (2013) and Phailin (2014) along eastern India. Similarly, Chen et al. (2009) documented TSM increases of 2.0 times during the landfall of Hurricane Frances (2004) along the U.S. Gulf Coast. ...
Article
Full-text available
In September 2017, Hurricane Maria severely defoliated Puerto Rico's landscape, coinciding with a series of persistent hydrological consequences involving the atmospheric, terrestrial, and marine components of the water cycle. During the defoliated period, the atmosphere's thermodynamic structure more strongly explained daily cloud activity (R ²PRE = 0.02; R ²POST = 0.40) and precipitation (R ²PRE = 0.19; R ²POST = 0.33) than before landfall, indicating that post-Maria land-atmosphere interactions were comparatively muted, with similar precipitation patterns also found following Hurricanes Hugo (1989) and Georges (1998). Meanwhile, modeled post-Maria runoff exceeded statistical expectations given the magnitude of contemporaneous precipitation. Enhanced runoff also coincided with greater sediment loads in nearshore waters, increasing sediment content greater than twofold. This study offers a holistic narrative of hydrospheric disturbance and recovery, whereby the instantaneous, large-scale removal of vegetation is accompanied by hydrologic changes “upstream” in the atmosphere and “downstream” in rivers and estuaries.
... They also provide different habitats such as mudflats, marshes, open waters, and fringing wetlands which have outstanding recreational, commercial, as well as ecological importance. However, coastal lagoons are often gravely threatened by human activities (such as industrialization, land reclamation for urbanization and agriculture, disposal of sewage), sea-level rise associated with climate change, and overexploitation of natural resources (Gedan et al. 2009;Kumar et al. 2017;He and Silliman 2019). ...
Chapter
Macrophytes are one of the major components that contribute to the primary production in shallow coastal lagoons. These macroscopic plants play a vital role in maintaining the ecological health of water bodies and also in structuring the biotic communities by providing physical structure for colonization and expanding the habitat complexity and heterogeneity. Chilika, the largest brackish water, coastal lagoon of India, is situated on the east coast in the state of Odisha. The lagoon is a biodiversity hotspot with high primary productivity due to a rich and diverse community of aquatic macrophytes and phytoplankton. The present chapter summarized the macrophyte studies from coastal lagoons of India and examined the spatiotemporal distribution, composition, and biomass of macrophytes from Chilika Lagoon based on the data derived from 2 years (2018–2019) of systematic field survey. A total of 22 macrophytes belonging to 14 families were identified from 33 sites which included 4 emergent species (Alternanthera philoxeroides, Ipomoea aquatica, Phragmites karka, and Schoenoplectus litoralis), 11 submerged (Ceratophyllum demersum, Najas indica, Stuckenia pectinata, Potamogeton crispus, Potamogeton nodosus, Hydrilla verticillata, Vallisneria natans, Halophila beccarii, Halophila ovalis, Halodule pinifolia, and Ruppia maritima), 2 rooted with the floating leaves (Nymphaea pubescens and Nymphoides cristata), and 5 free-floating (Azolla pinnata, Eichhornia crassipes, Pistia stratiotes, Salvinia cucullata, and Spirodela polyrhiza). Stuckenia pectinata and Najas indica were found in all sectors except the outer channel. A total of 11 macroalgal taxa comprising 6 species of Chlorophyta and 5 species of Rhodophyta were identified. Gracilaria verrucosa was often associated with seagrasses, whereas Chaetomorpha sp. and Ulva sp. were found growing with hard substratum such as rocks, etc., in the southern and central sectors. The seasonality in total macrophyte biomass revealed that it was the highest in winter (4322.38 g m−2) followed by summer (3056.18 g m−2) and monsoon (1957.14 g m−2). Salicornia brachiata, Sesuvium portulacastrum, and Paspalum distichum were abundant salt marshes in the Nalabana Bird Sanctuary of the lagoon. The occurrence of six seagrasses, namely, Halophila ovata, Halophila ovalis, Halophila beccarii, Halodule pinifolia, Halodule uninervis, and Ruppia maritima, was recorded from southern, central, and outer channel sector. A total of 169.2 km2 area covered by seagrass meadows was mapped through ground survey, which signified the good ecological health of this coastal ecosystem.
... A sudden drop in salinity level coupled with high turbidity may hamper seagrass beds as they prefer 15-34 ppt salinity and highly transparent water. The considerable variation in nutrients, salinity, and turbidity due to "Fani" can also affect lake phytoplankton and zooplankton communities and biomass (Srichandan et al. 2015;Kumar et al. 2016). ...
Article
This article evaluates the impacts of ‘Fani’, a category four cyclone on the shoreline and ecology of the largest brackish water lagoon of Asia, Chilika, on the East Coast of India. The cyclone forced open two New Tidal Inlets (NTI) along the northern shore of the lagoon’s outer channel leading to erosion of the embankments and spits. The average rate of change due to cyclonic storm ‘Fani’ was – 6.12 m while 66.03% of the total transects registered symbol of erosion along the shoreline of Chilika lagoon. Post Fani the information made available on its impact on Chilika was minimal which made us to look into published news articles, online news channels,past published scientific literature to corroborate the likely impact of such erosion and new tidal inlets on the lake ecosystem. Experts differed on their opinions on how the plankton, fish, seagrass and critically endangered Irrawaddy Dolphin would respond to the salinity changes in the lake aftermath of the cyclone. Some of the impacts of ‘Fani’ on the lake shoreline and ecosystem were imminent, such as the opening of tidal inlets and spot death of three Irrawaddy dolphins; whereas, long-term impacts such as changes in the biomass and composition of plankton communities, fish and bird population in the lake are primarily unknown and warrants further detailed investigation. Nevertheless, the study asserts that cyclone driven shoreline damage can impact lagoon ecosystem by bringing in a rapid change in the salinity field
... However, despite this strong effect, it seems that the system was able to recover to its previous condition, both in terms of phytoplankton biomass and Pn rates, in a short period of time (within~30 days or less), suggesting a high resilience to such perturbations. The physico-chemical and biological behaviours observed before, during and after the ERE in Los Micos Lagoon is consistent with that in other TOCEs, where a significant reduction of salinity, Chla and nutrient concentration during an ERE was followed by the re-establishment of the previous biogeochemical conditions shortly thereafter (Anandraj et al., 2008;Srichandan et al., 2015;Kumar et al., 2017). Similar behavior has been observed in estuaries permanently connected with the sea, where the runoff generated by extreme precipitation (e.g. ...
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... While wind can also produce significant flows, mostly at frequencies lower than those of tides-the so-called subtidal flows (Valle-Levinson et al., 2007;Wong & Wilson, 1984), the effect is more challenging to predict because weather is much more variable and less regular than tides. Among the weather events, there are the hurricanes or cyclones (e.g., Kumar et al., 2017;Weaver, Johnson et al., 2016), winter storms (e.g., Beardsley et al., 2013), atmospheric fronts (e.g., Feng & Li, 2010;Li et al., 2018;Walker & Hammack, 2000;Weaver, Taeb et al., 2016), and sea breezes (Mohanty & Panda, 2009). The effect of wind has been recognized and studied in various estuaries and lagoons (e.g., Elliott, 1978;Smith, 1985;Sternberger, 1983;Weisberg, 1976;Winant et al., 2014;Wong, 1994;Wong & Moses-Hal, 1998;Wong & Wilson, 1984). ...
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Studies on biogeochemical cycling of carbon in the Chilka Lake, Asia’s largest brackish lagoon on the east coast of India, revealed, for the first time, strong seasonal and spatial variability associated with salinity distribution. The lake was studied twice during May 2005 (premonsoon) and August 2005 (monsoon). It exchanges waters with the sea (Bay of Bengal) and several rivers open into the lake. The lake showed contrasting levels of dissolved inorganic carbon (DIC) and organic carbon (DOC) in different seasons; DIC was higher by ∼22% and DOC was lower by ∼36% in premonsoon than in monsoon due to seasonal variations in their supply from rivers and insitu production/mineralisation. The DIC/DOC ratios in the lake during monsoon were influenced by physical mixing of end member water masses and by intense respiration of organic carbon. A strong relationship between excess DIC and apparent oxygen utilisation showed significant control of biological processes over CO2 production in the lake. Surface partial pressure of CO2 (pCO2), calculated using pH–DIC couple according to Cai and Wang (Limnol and Oceanogr 43:657–668, 1998), exhibited discernable gradients during monsoon through northern (1,033–6,522μatm), central (391–2,573μatm) and southern (102–718μatm) lake. The distribution pattern of pCO2 in the lake seems to be governed by pCO2 levels in rivers and their discharge rates, which were several folds higher during monsoon than premonsoon. The net CO2 efflux, based on gas transfer velocity parameterisation of Borges et al. (Limnol and Oceanogr 49(5):1630–1641, 2004), from entire lake during monsoon (141mmolCm−2d−1 equivalent to 2.64GgCd−1 at basin scale) was higher by 44 times than during premonsoon (9.8mmolCm−2d−1≈0.06GgCd−1). 15% of CO2 efflux from lake in monsoon was contributed by its supply from rivers and the rest was contributed by insitu heterotrophic activity. Based on oxygen and total carbon mass balance, net ecosystem production (NEP) of lake (−308mmolCm−2d−1≈−3.77GgCd−1) was found to be almost in consistent with the total riverine organic carbon trapped in the lake (229mmolCm−2d−1≈2.80GgCd−1) suggesting that the strong heterotrophy in the lake is mainly responsible for elevated fluxes of CO2 during monsoon. Further, the pelagic net community production represented 92% of NEP and benthic compartment plays only a minor role. This suggests that Chilka lake is an important region in biological transformation of organic carbon to inorganic carbon and its export to the atmosphere.
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We present a comprehensive analysis of sediment dynamics in a coastal lagoon by synthesizing various remote sensing datasets. The goal of the study was to monitor and analyze the spatio-temporal variability of total suspended sediment (TSS) concentration and associated environmental forcings in Chilika Lagoon, the largest brackish water lagoon in Asia. Moderate Resolution Imaging Spectroradiometer (MODIS) surface reflectance cloud free data was used to calibrate a TSS model. MODIS daily 250 m surface reflectance (MOD09GQ) and 8-day composite products (MOD09Q1) were chosen because they are atmospherically corrected and available for free thus making them widely applicable for frequent monitoring of environmental phenomena. Three variants of Miller & McKee (2004) TSS model were recalibrated to establish the relationship between in situ TSS and surface reflectance value in band 1 (Rrs at 645 nm). A significant relationship (R2=0.91; n=54; p<0.001) was obtained between in situ TSS and MODIS Rrs (645 nm) using a polynomial model. The other two models, exponential and linear, showed comparatively low R2 (0.77 and 0.73 respectively). Accuracy of the models were assessed by comparing the field measured TSS with MODIS derived TSS. Based on R2 values, validation analysis (RMSE=2.64 mg/L), and residual trend, the polynomial model was found to be the best performing TSS model with an estimation range of 6.5 mg/L - 200 mg/L. The model was then implemented to derive weekly time-series TSS maps of Chilika Lagoon for 14 years (2001-2014). Marked seasonal and inter-annual variations in TSS distribution were observed in different sectors (northern, central and southern) of the lagoon. It was found that the TSS variability is primarily driven by three factors: monsoon effect (precipitation and runoff), wind-driven bottom re-suspension, and river discharge into the lagoon. Further analysis of the relationship between MODIS derived time-series TSS and meteorological parameters revealed that the variability of TSS in the northern sector is highly correlated with precipitation and runoff, whereas, TSS dynamics in southern sector is mainly governed by wind induced re-suspension events. The applicability of the TSS model was demonstrated by analyzing the impact of a recent category-5 cyclone, Phailin, which showed a significant increase in TSS concentration in the lagoon. This is the first of its kind study to comprehensively examine the long term TSS dynamics of Chilika, moreover, the model developed in this research was implemented in various coastal lagoons and estuaries around the world and was proven effective in quantifying TSS.
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This paper reviews the past and present conditions and management of Chilika Lagoon, the largest lagoon on India's eastern coast. Spatial and temporal salinity gradients, because of freshwater river inflow and seasonal seawater influx, have created unique characteristics of an estuarine ecosystem, and exercised a continuous, selective influence on the biota. Unfortunately, its biodiversity and the livelihoods that depend on it were being lost at a fast rate because of a blockage of the lagoon's mouth by silt coming from upstream catchments, as well as oceanic long-shore transport. Projects to restore the dynamic characteristics of the lagoon included dredging a new mouth to the ocean, as well as prevention of soil erosion in upstream areas. Management efforts resulted in a dramatic revival of this ecosystem, and contributed to a sharp rise in the incomes of fisherfolk. The institutional aspects of implementing such large-scale policy changes also are discussed, and the remaining issues and lessons learned are presented.
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