National Institute of Ocean Technology

Rearing mud crabs in floating cages adversely affects their growth due to exposure to higher surface and subsurface temperatures, which are unfavourable for these benthic organisms. Usually, mud crabs are cultivated in floating cages. An easy-to-manage submersible cage has been developed to address the issues of the floating cage while evaluating culture performance compared to the conventional floating system in terms of crab growth. Surface and bottom water quality were monitored for three months, and the growth performance of the crab was compared between the two systems. The temperature of the bottom water was found to be significantly lower than that of the surface water. From the initial to the end of the experiment, a steady temperature difference of 4℃ was observed between the surface and bottom water of the pond. Initial body weight (109.65 ± 7.70 g) of crabs for both systems was not significantly different. Specific growth rate (1.13 ± 0.09% d− 1) and weight gain (199.17 ± 23.04 g) were significantly higher in submersible cages compared to the floating system (0.85 ± 0.08% d− 1 and 122.8 ± 11.86 g). Size increment percentage was also significantly higher at the submersible system (40.07 ± 4.01%) than floating cages (28.43 ± 2.99%). 100% survival was observed in submersible cages, whereas 76.19% in floating cages after three months of rearing. Feed Conversion Ratio (FCR) was found significantly lower in the submersible system (4.61 ± 0.59) compared to the floating one (6.54 ± 0.53). Moreover, results indicated that the submersible cage system notably improved profitability through enhanced growth, survival, and feed efficiency. Overall, these results indicated that adopting submersible cage systems could significantly improve mud crab farming efficiency, making them a more practical and sustainable choice for aquaculture operations in tropical environments.

Abstract Tuticorin Bay (TB), a shallow semi-enclosed coastal system on the southeast coast of India, exemplifies the escalating challenges faced by urbanized tropical bays, where anthropogenic stressors interact with complex biogeochemical processes. This study investigates the spatial and seasonal variability of carbonate system dynamics and air–sea carbon dioxide (CO₂) fluxes across three hydrologically distinct periods: the southwest monsoon (SWM, August 2018), northeast monsoon (NEM, October 2018), and summer (SUM, May 2019). Surface waters exhibited a wide range of pCO₂ (380–1036 μatm), revealing spatial heterogeneity across distinct biogeochemical regimes. Elevated pCO₂ levels in most regions confirm the bay’s dominant role as a CO₂ source; however, localized undersaturation (~ 380 μatm) during the SWM indicates short-term CO₂ uptake, associated with intense biological production and high chlorophyll-a concentrations (> 50 μg L⁻ 1 ) in the nutrient-enriched north region of the bay. In contrast, the southern bay showed persistently high pCO₂, driven by elevated temperatures (> 36 °C) and enhanced respiration promoted by thermal effluent discharges. Dissolved Inorganic Carbon (DIC) exhibited non-conservative behaviour across seasons, with ΔDIC ranging from –487 to + 639 μmol kg⁻ 1 , highlighting the influence of terrestrial inputs and local metabolic processes. Peak air–sea CO₂ fluxes reached 17.23 mmol C m⁻ 2 d⁻ 1 during SUM, particularly in low-oxygen zones (< 60% saturation) of the southern bay. These findings demonstrate how seasonally shifting physical conditions and localized anthropogenic pressures govern CO₂ dynamics in a spatially confined tropical bay, underscoring the need for high-resolution assessments of such vulnerable systems to improve regional carbon budget estimates.

ABSTRACT Partial shading is crucial in reducing the performance of the photovoltaic (PV) array. The static reconfiguration is a viable option for alleviating the partial shading. The scattering of shade relies on its puzzle pattern. This research proposes a static Kropki puzzle‐based reconfiguration to scatter the shade effectively, thereby alleviating the consequence of partial shading. The Kropki puzzle pattern offers the benefits of simple rules and faster execution. The position of the panels is modified in accordance with the Kropki puzzle pattern and tested experimentally on a 4 × 4 total‐cross‐tied array. The Kropki reconfiguration is validated by relating to total‐cross‐tied, Sudoku, Skyscraper, and Odd–Even configurations by performance parameters. Overall, the experimental results show that the Kropki puzzle has superior shade capability and improved PE by 54% compared to conventional TCT.