A new species of Corallana Dana, 1852 (Crustacea: Isopoda: Corallanidae) from the Andaman Islands, northern Indian Ocean

Corallana mishrai sp. nov. collected from dead mangrove roots at Kodiyaghat, South Andaman, Andaman Islands, India is described and illustrated in detail. Corallana mishrai sp. nov. the first definitive record of the genus from India, is characterized by: frontal lamina with short straight (or very weakly convex) lateral margins and the anterior margin forming a strong acute median point; pleotelson length 0.76 greatest width, posterior margin with 5 robust setae; uropodal exopod 7 times longer than greatest width, extending beyond endopod by one fourth of its length; endopod lateral margin slightly convex with 4 RS and PMS, apex forms a slightly obtuse angle with long simple setae, mesial margin weakly convex with 2 RS and PMS; mandible bidentate; transverse row of 6 tubercles present on pereonite 1 and pleonites 2, 3 and 4 lacking lateral tubercles. The status of the genus and its species are reviewed, and two species are transferred to new combinations: Argathona kulai (Bruce, 1982) comb. nov. and Tachaea bidentata (Jones et al. 1983) comb. nov.

Evaluating the large-scale hydrological cycle response within the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2) ensemble

The mid-Pliocene (∼3 Ma) is one of the most recent warm periods with high CO2 concentrations in the atmosphere and resulting high temperatures, and it is often cited as an analog for near-term future climate change. Here, we apply a moisture budget analysis to investigate the response of the large-scale hydrological cycle at low latitudes within a 13-model ensemble from the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2). The results show that increased atmospheric moisture content within the mid-Pliocene ensemble (due to the thermodynamic effect) results in wetter conditions over the deep tropics, i.e., the Pacific intertropical convergence zone (ITCZ) and the Maritime Continent, and drier conditions over the subtropics. Note that the dynamic effect plays a more important role than the thermodynamic effect in regional precipitation minus evaporation (PmE) changes (i.e., northward ITCZ shift and wetter northern Indian Ocean). The thermodynamic effect is offset to some extent by a dynamic effect involving a northward shift of the Hadley circulation that dries the deep tropics and moistens the subtropics in the Northern Hemisphere (i.e., the subtropical Pacific). From the perspective of Earth's energy budget, the enhanced southward cross-equatorial atmospheric transport (0.22 PW), induced by the hemispheric asymmetries of the atmospheric energy, favors an approximately 1∘ northward shift of the ITCZ. The shift of the ITCZ reorganizes atmospheric circulation, favoring a northward shift of the Hadley circulation. In addition, the Walker circulation consistently shifts westward within PlioMIP2 models, leading to wetter conditions over the northern Indian Ocean. The PlioMIP2 ensemble highlights that an imbalance of interhemispheric atmospheric energy during the mid-Pliocene could have led to changes in the dynamic effect, offsetting the thermodynamic effect and, hence, altering mid-Pliocene hydroclimate.

Role of eccentricity in early Holocene African and Asian summer monsoons

The effect of precession on paleoclimate changes depends on eccentricity. However, whether and to what degree eccentricity relates to millennial-scale monsoonal changes remain unclear. By investigating climate simulations with a fixed precession condition of 9 ka before the present, we explored the potential influence of eccentricity on early-Holocene changes in the Afro–Asian summer monsoons. Compared with the lower eccentricity of the present day, higher eccentricity in the early Holocene strengthened the continental summer monsoons, Pacific anticyclone, and Hadley circulation, particularly over the ocean. Over Africa, the eccentricity-induced “dry-gets-wetter” condition could be related to the Green Sahara, suggesting a superimposed effect of precession. Over the western Pacific, the tropical response to eccentricity may have been competitive in terms of what an extremely high obliquity may have caused. A downscaled modulation of eccentricity in relation to precession and obliquity cannot be ignored when paleomonsoon records are studied. Regarding early-Holocene monsoonal changes in South Asia, however, a high eccentricity may have had only a secondary effect on enhancing the monsoonal precipitation in the southern edge of the Tibetan Plateau, exhibiting the weak power of candle-like heating. This suggested that sizable monsoonal changes over the northern Indian Ocean and India–Pakistan region are unrelated to early-Holocene eccentricity.

Reproductive and feeding biology of unicorn leatherjacket, Aluterus monoceros from the Bay of Bengal, Northern Indian Ocean

No prior comprehensive information on the reproductive biology and trophodynamics of Aluterus monoceros was globally available. The present study was performed on 1036 individuals landed along the western Bay of Bengal during 2017 to 2019. Length ranged between 25.3–64.4 cm in females (mean at 48.34 cm) and from 21.5–64.1 cm in males (mean at 47.83 cm). Growth was negatively allometric with no significant difference between sexes. Sex ratio (F:M) was 1.03 with variations based on sizes and months. Size at sexual maturity for females and males was 40.85 and 41.60 cm, respectively. The species spawned throughout the year with major and minor peaks during February to May and October and November. Absolute fecundity increased linearly with length and weight and ranged from 33,640 eggs to 12,39,202 eggs. Stomachs were empty or with trace amounts of food in 59.17%, part-full in 34.07% and full in 6.76% of the fishes. Stomach vacuity and fullness and predator–prey weight ratios varied with an increase in body size, implying higher feeding intensity in large-sized fishes. Feeding activity was more intense during June–August and less during the peak spawning months. The species is omnivorous and a bottom feeder. Teleosts contributed the most to the prey items (43.23% by Index of Preponderance) implying preference for carnivory. Ontogenetic shifts and seasonal variations in prey items were observed. The present study provides paramount information that can significantly contribute to the management and conservation of monacanthid stocks in northern Indian Ocean.

Simultaneous Occurrence of Tropical Cyclones in the Northern Indian Ocean: Differential Response and Triggering Mechanisms

The northern Indian Ocean, comprising of two marginal seas, the Arabian Sea (AS) and the Bay of Bengal (BoB), is known for the occurrence of tropical cyclones. The simultaneous occurrence of the cyclones Luban in the AS and Titli in the BoB is a rare phenomenon, and, in the present study, we examined their contrasting upper ocean responses and what led to their formation in October 2018. Being a category-2 cyclone, the maximum cooling of sea surface temperature associated with Titli was 1°C higher than that of Luban, a category-1 cyclone. The higher tropical cyclone heat potential in the BoB compared with the AS was one of the reasons why Titli was more intense than Luban. The enhancement of chlorophyll a (Chl-a) and net primary productivity (NPP) by Luban was 2- and 3.7-fold, respectively, while that by Titli was 3- and 5-fold, respectively. Despite this, the magnitudes of both Chl-a and NPP were higher in the AS compared with the BoB. Consistent with physical and biological responses, the CO2 outgassing flux associated with Titli was 12-fold higher in comparison to the pre-cyclone value, while that associated with Luban was 10-fold higher. Unlike the Chl-a and NPP, the magnitude of CO2 flux in the BoB was higher than that in the AS. Although the cyclones Luban and Titli originated simultaneously, their generating mechanisms were quite different. What was common for the genesis of both cyclones was the pre-conditioning of the upper ocean in 2018 by the co-occurrence of El Niño and the positive phase of Indian Ocean dipole along with the cold phase of the Pacific decadal oscillation, all of which worked in tandem and warmed the AS and parts of the BoB. What triggered the genesis of Luban in the AS was the arrival of the Madden–Julian oscillation (MJO) and the mixed Rossby-gravity wave during the first week of October. The genesis of Titli in the BoB was triggered by the eastward propagation of the MJO and the associated enhanced convection from the AS into the region of origin of Titli along with the arrival of the downwelling oceanic Rossby wave.