Correction: Comprehensive assessment of chemical and microbial inducers for coral larval settlement across diverse coral species

Sun Huiming^1,2Qingsong Yang^1,3*Dong Junde^1,4Jie Li¹Chang Chen^1,3Tang Xiaoyu¹Ying Zhang¹Juan Ling^1*

• ¹Key Laboratory of Tropical Marine Bio-Resources and Ecology, Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences (CAS), Guangzhou, China
• ²College of Marine Sciences, University of Chinese Academy of Sciences, Beijing, China
• ³Xisha Marine Environmental National Observation and Research Station, Chinese Academy of Sciences, Shansha, China
• ⁴Tropical Marine Biological Research Station in Hainan, Chinese Academy of Sciences and Hainan Key Laboratory of Tropical Marine Biotechnology, Sanya, China

Coral reefs, widely acknowledged as among the most diverse and productive ecosystems on the planet (Mumby et al., 2008; Brandl et al., 2019), are currently facing persistent challenges driven by anthropogenic factors, notably climate change (Fezzi et al., 2023), pollution (Nalley et al., 2021), and overfishing (Milne et al., 2022). Consequently, the degradation of coral reefs has intensified, resulting in a significant loss of biodiversity and ecosystem services (Bellwood et al., 2004). In response to these challenges, coral restoration efforts have been initiated to mitigate the detrimental effects and restore ecosystem vitality (Boström-Einarsson et al., 2020; Suggett and van Oppen, 2022). A fundamental aspect of coral restoration is understanding the factors influencing coral larval settlement, a crucial phase in the coral life cycle for successful reef rehabilitation. (Barton et al., 2017; Pollock et al., 2017; Omori, 2019). Settlement inducers play a critical role in this restoration process, as they activate or enhance the settlement of coral larvae on appropriate substrates (Gómez-Lemos and García-Urueña, 2022; Rodd et al., 2022). The literature on coral larval settlement has explored various natural and artificial cues (Barton et al., 2017), including crustose coralline algae (CCA) (Grasso et al., 2011; Gómez-Lemos and García-Urueña, 2022), inorganic material (Levenstein et al., 2022), calcium chloride (Yang et al., 2022), tetrabromopyrrole (TBP) (Sneed et al., 2014; Sneed et al., 2024), GLW-amide neuropeptide (Iwao et al., 2002; Erwin and Szmant, 2010), and microbial agents like Roseobacter sp. (Sharp et al., 2015), Pseudoalteromonas sp. (Tebben et al., 2011), and Metabacillus sp. (Zhang et al., 2021). CCA, a natural inducer, has long been acknowledged for its role in coral larval settlement through biochemical and structural cues (Morse et al., 1988). However, its practical applications are limited by environmental sensitivity and variability in bioactive compound production (Kuffner et al., 2008). In contrast, synthetic chemical inducers (e.g., calcium chloride) and microbial agents (e.g., Metabacillus sp.) offer advantages in consistency, productivity, and stability, making them promising alternatives for standardized restoration protocols (Zhang et al., 2021; Yang et al., 2022). These innovations highlight the potential to overcome the limitations of natural inducers in large-scale restoration efforts. Despite significant progress in identifying individual cues affecting settlement, the broader spectrum of inducers and their effects across various coral species, including both brooding and spawning corals, remain significantly understudied. Most of the current studies have focused on single species or narrow inducer categories, with limited cross-species comparisons (Pollock et al., 2017; Levenstein et al., 2022). This gap impedes the scalability of large-scale coral restoration, particularly in regions with high coral diversity such as the Coral Triangle, where over 600 coral species coexist (Barton et al., 2017; Boström-Einarsson et al., 2020). Without understanding species-specific inducer efficacy, large-scale restoration protocols risk inefficiency or failure when applied to multi-species reefs (Barton et al., 2017). For example, broadcast spawners such as Acropora spp. dominate Indo-Pacific reefs but exhibit lower post-settlement survival under generic protocols compared with brooders like Pocillopora damicornis (Bellwood et al., 2004; Pollock et al., 2017; Omori, 2019). Besides, standardized protocols often overlook interspecific physiological thresholds, and a “one-size-fits-all” inducer approach could waste resources or harm sensitive species (Omori, 2019; Boström-Einarsson et al., 2020; Suggett and van Oppen, 2022). For example, prolonged exposure to CaCl2 and strain cB07 increased their toxicity, resulting in decreased survival rates of coral larvae (Zhang et al., 2021; Yang et al., 2022). The identification of broad-spectrum inducers and the delineation of species-specific toxicity thresholds will provide actionable frameworks to improve the precision and cost-effectiveness of restoration workflows, particularly in regions with high coral diversity. Furthermore, evaluations often prioritize settlement rates alone, neglecting post-settlement physiological responses such as metabolism, morphology, and long-term survival (Boström-Einarsson et al., 2020). A comprehensive understanding of inducer effects could therefore transform restoration strategies by aligning protocols with the ecological niches and physiological limits of species, ultimately improving the resilience of reef ecosystems under escalating climatic and anthropogenic pressures. In our previous research, we identified calcium chloride (CaCl2) and Metabacillus sp. cB07 as effective settlement inducers for P. damicornis, a brooding stony coral species (Zhang et al., 2021; Yang et al., 2022). However, their settlement-inducing effect on other coral species, especially the spawning corals, remains unknown. The current study aims to address a pivotal question: How do the representative chemical and microbial inducers compare to CCA in their efficacy and physiological impacts across multiple coral species with distinct life-history strategies? We systematically evaluated CaCl2, strain cB07, and CCA on seven coral species, including both brooders and broadcast spawners, quantifying larval settlement rates, metabolic responses, morphological changes, and post-settlement survival and growth. By integrating multi-species and multi-indicator analyses, this study advances a framework for selecting inducer protocols tailored to species-specific needs, ultimately improving the scalability and success of coral reef restoration.