Chew, K. L. | bioRxiv Science

bioRxiv2026

Lessons from the equator: a window on the future of vibriosis in a warming Earth

Vibrios are important aquatic human pathogens, causing gastroenteritis, wound infections, and cholera. Vibriosis (non-cholera infection) has been increasing in temperate climates due to correlation between Vibrio abundance and water temperature. However, how warming oceans differentially influence various Vibrio species, and whether incidence is higher in tropical regions, remains understudied. We assembled the first comprehensive dataset of culture-confirmed vibriosis cases outside a temperate climate from equatorial Singapore. Comparison to cases from the detailed United States (US) CDC COVIS system revealed that vibriosis incidence is over two times higher in Singapore than the United States. Causative species also differ markedly, with Vibrio fluvialis and non-toxigenic Vibrio cholerae dominating in Singapore (>40%) but are much less prominent in the United States (<15%). Singapore cases have remained stable in the last decade, while US incidence is rising rapidly, especially for V. fluvialis and V. cholerae (13% and 17% per year). Differences in causative species in Singapore and the United States suggest ecological factors may shape infection dynamics, with some species benefitting more from warming oceans, raising their equatorial prominence. Incidence is stable in Singapore, likely due to slower warming of waters near the equator. In contrast, vibriosis in the United States will likely continue to increase steadily, with changing species composition, likely becoming tropicalized.

microbiology↗

bioRxiv2025

Species-specific bleaching trajectories during the 4th global coral bleaching event in northeastern Peninsular Malaysia

During the 4th global coral bleaching event (2023-2025), over 80% of the worlds coral reefs experienced bleaching-level heat stress above 4 {degrees}C-weeks (DHW). Inevitably, the large spatial extent of this event substantially impacted coral reefs worldwide, and data are needed to quantify bleaching trajectories and coral mortality. In northeastern Peninsular Malaysia, heat stress accumulated to record levels by June 2024 (DHW=9.6 {degrees}C-weeks), resulting in severe mass coral bleaching. Here, we quantified species-specific bleaching and mortality trajectories for 12 abundant reef-building coral species of the genera Acropora, Diploastrea, Echinopora, Heliopora, Montipora, and Porites, by tracking 1850 tagged colonies from September 2023 to October 2024 using a novel Colony Bleaching Response Index (CBRI) that considers scales of discoloration and colony surface extent. In June 2024, 92.9% of all surveyed corals were bleached, resulting in 40.6% mortality by October 2024. However, bleaching trajectories varied across species, whereby the least bleached species in June were not the first to recover nor the least affected by mortality, suggesting inherent species-specific bleaching trajectories and recovery pathways. Mortality of Porites cf. lobata and Diploastrea heliopora was [≤]1%, whereas severe mortality was recorded for Acropora species (five species, range 46.3-95.4%), Echinopora cf. horrida (44.7%), and Montipora cf. aequituberculata (27.8%). Among susceptible species was Heliopora coerulea, a species commonly considered heat tolerant. Our findings challenge previous regional studies that concluded a reversal of bleaching hierarchies of species over time, whereby historically ascribed heat tolerant species (i.e., slow-growing massive species) became susceptible and historically susceptible fast-growing species became heat tolerant. Importantly, bleaching severity did not decrease with depth. These data represent the first regional accounts of species-specific coral bleaching mortality in Malaysia, highlighting distinctive ecological bleaching and recovery trajectories of species.

ecology↗