Biology subjects

Szereday, S.

Publications and source records attributed to Szereday, S..

4 recordsLinked to original sources

bioRxiv2026

Ecological bleaching trajectories under severe heat stress are only partially captured by acute heat stress assays

Global marine heatwaves have devastated tropical coral reefs, and further mortality is projected under ongoing climate change. Identifying thermally tolerant coral colonies is therefore a priority for conservation, restoration, and research. Portable acute heat stress assays (e.g., CBASS) enable rapid, standardized estimates of coral thermal tolerance under field conditions. However, it remains unresolved whether such experimentally derived metrics (ED5, ED50, DW) predict bleaching and mortality in situ. Here, we quantified acute thermal tolerance metrics for 2,068 coral colonies across 12 common Indo-Pacific species, six months prior to an unprecedented heat stress event in northeastern Peninsular Malaysia and compared experimentally derived ED and DW values to subsequent bleaching severity and mortality in the field. Experimental thermal tolerance metrics explained only a limited proportion of variation in bleaching outcomes and survival. Predictive power varied among species and was higher in slow-growing species. Our findings suggest that while acute heat stress assays capture substantial variation in coral thermal tolerance, their ability to predict in situ outcomes is context-dependent and diminishes under severe thermal stress. Ultimately, in situ coral bleaching under severe heat stress may reduce the discriminatory capacity of acute assay-derived tolerance metrics.

ecology↗

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↗

bioRxiv2022

Colony size frequency distribution across gradients of reef health in disturbed coral reefs in Northeast Peninsular Malaysia

Coral reefs globally are experiencing chronic stress leading to the deterioration of health and functionality. Analysis of size frequency distribution (SFD) of hard corals enables post hoc assessments of major demographic events (e.g., recruitment and mortality) that follow ecological disturbances. Here, we present an evaluation of current reef health, SFD and recruitment of 37 morpho-taxa in Northeast Peninsular Malaysia. Results highlight stress viable demographic structure of massive taxa (e.g., massive Porites) and significant differences of SFD across gradients of reef health, whereby degraded sites were predominantly characterized by negatively skewed (e.g., large colonies) and leptokurtic (e.g., high population turnover) distribution of dominant hard coral taxa. Ultimately, results suggest that locally coral reef degradation can exceed tipping points, after which annual monsoon conditions and degraded reef substrates interact to reinforce and manifest negative feedback loops, thereby impeding demographic recovery, and altering coral SFD and population assemblage.

ecology↗

bioRxiv2021

Successive bleaching events (2019-2020) in Northeast Peninsular Malaysia revealed selective thermal acclimatization and susceptibility of hard corals at biophysical reef scale

Due to current greenhouse gas emissions, Malaysian coral reefs are predicted to experience severe annual coral bleaching events by 2043, threatening the survival of coral reefs within this century. However, there is no field data on how Malaysian coral reefs respond to successive events of coral bleaching. Despite the notion that many scleractinian taxa exhibit increased thermal tolerance over the last decade, it remains unresolved whether these changes are a result of weeding out thermally susceptible species and actually ameliorate accelerating warming rates and increasing frequencies of heat disturbances. Moreover, complex interaction of environmental and biological factors that underlie differences in the bleaching response necessitate conducting studies at the within-reef scale (i.e., leeward shallow, windward shallow). Here, we studied two successive thermal stress events starting during the 2019 El Nino Southern Oscillation (ENSO), and determined bleaching trajectories of 29 hard coral taxa across fine spatio-temporal gradients in Northeast Peninsular Malaysia. Analysis of climate trajectories affirms accelerating warming rates (0.17{degrees}C per decade) and higher return-frequency of heat disturbance. Despite high annual maximum temperatures above the putative bleaching threshold (31.07{degrees}C and 31.74{degrees}C, respectively), accumulated thermal stress was low during both bleaching episodes (Degree Heating Weeks of 1.05{degrees}C-weeks and 0.18{degrees}C-weeks, respectively), suggesting widespread thermal sensitivity of hard coral taxa (55.21% and 26.63% bleaching incidence in 2019 and 2020, respectively). However, significant discrepancies between satellite and in-situ temperature data were found (0.63{degrees}C; SD{+/-}0.26). Bleaching severity was highly taxon-specific, varied across and within reef scales due to wind exposure and depth (e.g., less bleaching at shallow windward sites), and partially contrasted historical bleaching observations (e.g., Acropora and Montipora were less susceptible, Cyphastrea, Echinopora, Goniastrea, Heliopora and Porites were highly susceptible). While bleaching severity was higher in 2019, Galaxea and Leptastrea were bleaching more in 2020 despite lower heat stress, suggesting negative legacy effects of the 2019 bleaching event on these taxa. In conclusion, hard corals were subjected to more frequent heat stress during the last decade and remain highly vulnerable to marine heatwaves across all biophysical reef scales. Annual coral bleaching impacted all hard coral taxa and reduced thermal tolerance in at least two taxa.

ecology↗