Narrower grid structure of artificial reef enhances initial survival of in situ settled coral

The initial factors that cause a decline in the survival of in situ settled corals remain poorly understood. In this study, we demonstrated through field experiments that the design of artificial grid plates may influence the initial survival of Acropora corals, with narrower grids being the most effective. In fact, grid plates with a 2.5-cm mesh presented the highest recorded survival rate (14%) at 6 months after settlement (representing approximately 50 corals per 0.25 m² of plate). This is the first study where such high survival rates, matching those of cultures under aquarium conditions, were obtained in the field without using additional protective measures, such as guard nets against fish grazing after seeding. Therefore, our results provide a foundation for establishing new and effective coral restoration techniques for larval seeding, in parallel to clarifying the details of the early life stages of reef-building corals.     

Noble gases in Muong Nong‐type tektites and their implications

Abstract— We have the elemental abundances and isotopic compositions of noble gases in Muong Nong‐type tektites from the Australasian strewn field by crushing and by total fusion of the samples. We found that the abundances of the heavy noble gases are significantly enriched in Muong Nong‐type tektites compared to those in normal splash‐form tektites from the same strewn field. Neon enrichments were also observed in the Muong Nong‐type tektites, but the Ne/Ar ratios were lower than those in splash‐form tektites because of the higher Ar contents in the former. The absolute concentrations of the heavy noble gases in Muong Nong‐type tektites are similar to those in impact glasses. The isotopic ratios of the noble gases in Muong Nong‐type tektites are mostly identical to those in air, except for the presence of radiogenic ⁴⁰Ar. The obtained K‐Ar ages for Muong Nong‐type tektites were about 0.7 Myr, similar to ages of other Australasian tektites. The crushing experiments suggest that the noble gases in the Muong Nong‐type tektites reside mostly in vesicles, although Xe was largely affected by adsorbed atmosphere after crushing. We used the partial pressure of the heavy noble gases in vesicles to estimate the barometric pressure in the vesicles of the Muong Nong‐type tektites. Likely, Muong Nong‐type tektites solidified at the altitude (between the surface and a maximum height of 8–30 km) lower than that for splash‐form tektites.     

Upper ocean warming pattern in the past 50 years

A long-term warming pattern of global subsurface ocean was detected separately from other natural variations. Three dominant modes were extracted: a long-term warming mode, a mode related to the El Niño/Southern Oscillation, and a mode related to the Atlantic Multidecadal Oscillation. The long-term warming mode explained 78 % of the global mean temperature variance from the surface to a depth of 300 m, and the other two modes could explain most of the residual variance. Subsurface warming associated with the long-term warming mode was strong in the subtropics. In contrast, there was a local minimum of warming in the northern hemisphere subarctic ocean, and warming was suppressed in subsurface waters south of the equator. Atmospheric changes associated with the long-term warming mode showed negative (positive) sea level pressure anomalies at high (middle) latitudes in both hemispheres, and an intensification and/or a poleward expansion of mid-latitude westerlies. Wind stress curl changes were negative in the subtropics and positive in the subarctic of the northern hemisphere; changes that were consistent with the strong warming in the subtropics and the local minimum of warming in the subarctic. Warming of Southern Ocean subsurface waters coincided with southward migration and intensification of westerly winds, whereas surface warming to the south of 50°S was suppressed, probably by strengthened northward Ekman transport. Positive wind stress curl off the equator with weakening of the tropical easterly winds in the Pacific and Indian Oceans was consistent with the subsurface negative temperature anomaly there.