Hadal trenches remain one of the unexplored ocean ecosystems due to the challenges of sampling at great depths. It is still unclear how a faunal community changes from the abyssal to the hadal zone, and which environmental variables are the key impacting factors. In this study, nine dives of the Human Occupied Vehicle (HOV) “ JIAOLONG ” were conducted from abyssal to hadal depths (4,435–6,796 m) in the Yap Trench on the southeastern boundary of the Philippine Sea Plate in the western Pacific, divided into 48,200 m video transects, to describe the megafaunal communities and reveal their relationship with environmental factors. A total of 1,171 megafauna organisms was recorded, 80 morphospecies (msps) from 8 phyla were identified based on the video data, most of which were reported for the first time in the Yap Trench. Arthropoda was the most abundant phylum and Echinodermata was the most diverse phylum of the megafaunal community. The faunal abundance increased with depth, whereas the Shannon diversity index decreased with depth. Cluster analysis suggested seven assemblages, with five abyssal groups, one mixed group, and one hadal dominant group. Although megafaunal communities changed gradually from abyssal zone to hadal zone, both PERMANOVA and PERMDISP analyses revealed that the communities are significantly different between abyssal zone and hadal zone, indicating 6,000 m as the boundary between the two depth zones. Depth, substrate, slope, and latitude were identified as four important environmental factors with significant influence on megafaunal community structure. This study proposed a transition pattern from the abyssal to hadal zone in the Yap Trench, highlighted the importance of habitat heterogeneity in structuring megafaunal community in a hadal trench.
Abstract Tropical cyclones (TCs) are known to bring heavy rainfall, strong winds and severe storm surges simultaneously, resulting in tremendous damage beyond the effects of a single hazard. However, the compound impacts of TC multi‐hazards remain unexplored in macroeconomic assessments. Here, we provide empirical evidence on the multi‐hazard economic losses of TC for the first time. We used a national panel of provincial economic output in China over 2000–2020. Our results show that the total macroeconomic impact of the severest TC multi‐hazards can represent up to 14 times the value of merely TC winds. Specifically, the vast majority (over 80%) of the combined TC impacts is caused by precipitation, with wider and greater economic impacts than TC winds and storm surges. Furthermore, high‐latitude and interior regions of China are more vulnerable to TCs due to the interactions with temperature variability and TC wind intensity variability. High‐income areas and secondary industries respond markedly to all TC hazards, and the economic impact of TC precipitation is significant over all sectors. Our findings provide new implications for the socio‐economic impact mechanisms of multiple hazards of TCs and valuable insights into the design of climate policy for compound hazard risks.
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