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Over-summering of shorebirds refers to the phenomenon where certain species of shorebirds, primarily migratory, remain on their non-breeding grounds during the summer months for one or more years instead of migrating to their breeding grounds. The present study investigates the presence and abundance of over-summering shorebird species at four distinct sites covering 24 scanning points along the southeastern coasts of Tamil Nadu for 2017-2023. A total of 13 species were observed over-summering, with Lesser Sand Plover being the most dominant species, followed by Greater Sand Plover. Notably, 10 species were found across all four sites, while three species--Black-tailed Godwit, Bar-tailed Godwit, and Common Sandpiper--were exclusive to Dhanushkodi Lagoon, observed only during 2023. The study examined the year-wise abundance of these species, revealing a decline in over-summering shorebirds across all study sites. The Eurasian Curlew, Curlew Sandpiper, Bar-tailed & Black-tailed Godwits are the 'Near Threatened' species observed during the study. Furthermore, the research highlighted variations in Shannon species diversity index (H) location-wise and year-wise - Manoli Island (H = 2.25) in 2023; Dhanushkodi Lagoon (H = 1.8) in 2023; Valinokkam Lagoon (H = 1.63), and Pillaimadam Lagoon (H = 2.08) in 2017. Key findings are that among the study sites, in Pillaimadam Lagoon all 10 species' abundance declined; in Valinokkam Lagoon, Greater Sand Plover and Little Stint marginally increased, and eight species declined; Common Redshank and Ruddy Turnstone marginally increased in Manoli Island, while other eight species declined; Grey Plover population increased in Dhanushkodi Lagoon along with a marginal decrease in Common Redshank and Ruddy Turnstone as other species declined, over the years of study. [ABSTRACT FROM AUTHOR]

The spatial distribution of the C/N ratios and variations in δ13C and δ15N of suspended particulate matter were used to characterise their source in Asia’s largest brackish water lagoon, Chilika, India. In addition, the significance of re-mineralised nutrients in the primary productivity of the shallow lagoon was also determined through quantification of the subsurface nitrogen uptake conditions at two relatively stable locations in the lagoon. The results indicated that the influence of terrestrial organic matter was the maximum in the northern sector and was relatively limited at the central and southern part of the lagoon.In situ15N uptake experiments (daytime) under biogeochemically stable conditions revealed that the N uptake by phytoplankton ranged between 0.24 and 1.01 mM m−3 h−1during pre-monsoon and post-monsoon seasons. New production and regenerated production in the shallow lagoon was also estimated by calculatingf-ratios (ratio of nitrate assimilation by phytoplankton to total nitrogenous nutrient assimilation, have been estimated), which varied from 0.52 in the post-monsoon to 0.38 in the pre-monsoon. Lowering of thef-ratio from post- to pre-monsoon indicated a dominance of mineralisation over the new production. [ABSTRACT FROM AUTHOR]

Chilika, a lagoon along the east coast of India, is undergoing transformation due to frequent shoreline change near inlet(s). Shoreline change near inlet includes change in position and shape of inlet, inlet channel length, and spit growth/erosion. These variable features of lagoon inlet(s) critically depend on alongshore sediment transport (LST) and discharge (water and sediment) from the lagoon to the sea. The LST and the processes responsible for sand spit growth/erosion, considered as important attributes of inlet stability, are the subject matter of the present investigation and hence the study assumes importance. The study includes integration of observational and modeling framework. Observations include nearshore wave, bathymetry, beach profile, shoreline and sediment grain size of spits while numerical modeling includes simulation of the wave using MIKE 21 Spectral Wave model and LST simulation using LITtoral DRIFT. The results indicate that the predominant wave directions as S and SSE, which induces round the year south to north alongshore transport with significant seasonal variation in magnitude. The estimated LST closely matches with previous studies near Chilika inlet and for other locations along the Odisha coast. Besides temporal variability, the study reveals spatial variability in alongshore transport near Chilika inlet and considers it as one of the important attributes along with northward spit growth for inlet migration/closure/opening. [ABSTRACT FROM AUTHOR]

Occurrence of fluid mud (mud banks) in the southwest coast of India is an enigma for the scientific community. Over the years, several multi-disciplinary studies were conducted and various hypotheses were postulated on the occurrence and sustenance of fluid mud. Nevertheless, none of them could be proved or disproved with field data. In the present study, an attempt was made to assess the validity of some of the prevailing hypothesis on its occurrence such as subterranean conduit flow of mud/water from a coastal lagoon, submarine groundwater discharge, river flows etc. by integrating field surveys, refining the hydrogeological understanding of the area and application of environmental isotopes ( 222 Rn, δ 18 O, δ 2 H and 3 H) in the ‘Alappuzha mud bank’ region, Kerala, during its formation in the southwest monsoon period. In-situ 222 Rn monitoring survey in the coastal waters of Pallana showed that 222 Rn activities in the fluid mud region were negligible compared to the suspected continental end members such as Pamba River, Vembanad Lagoon, shallow and deep groundwater indicating that there was no freshwater inputs from these sources. Comparison of the characteristic stable isotopic signatures of δ 18 O and δ 2 H in the samples from the fluid mud region and the suspected continental end members implied that there was no mixing of these water sources with the seawater. 3 H results indicated that the shallow groundwater is modern and recharged annually from precipitation while deep groundwater in the Warkali aquifer within the study area is old (>50 years). It also indicated that there is no vertical interconnection between the Vembanad Lagoon and the deep Warkali aquifers. Hence, from the study, it appears that river flows, submarine groundwater discharge or subterranean (conduit flow) flow from the Vembanad Lagoon may not be responsible for the occurrence and sustenance of fluid mud in Pallana coast, Alappuzha. [ABSTRACT FROM AUTHOR]

A study was conducted in Lakshadweep islands to determine the feasibility of using Indian Remote Sensing (IRS) satellites for detecting changes in the seagrass from other coastal features. IRS ID and IRS P6 LISS III having spatial resolution of 23.5 m with lower cost compared to all other contemporary satellites with the same spatial resolution have not been widely used for monitoring the changes in seagrass cover. In this context, the present study attempted to explore the effectiveness of LISS III data for mapping seagrasses and to inform the international community about the usefulness of these low-cost imageries for coastal resource monitoring. Supervised classification and change detection studies found a significant decrease in seagrass cover of 73.03 ha in the Lakshadweep group of islands. An overall accuracy of 67.5% was obtained for the change maps, and seagrass cover and its changes vary at different islands. [ABSTRACT FROM PUBLISHER]