The Unseen Drivers of Coral Health; Coral Microbiome; The Hope for Effective Coral Restoration

Abstract

Coral restoration is important in ocean engineering because corals play a crucial role for sustainable marine ecosystems and in global carbon cycle. Coral microbiome controls the host life and functions by occupying different coral components such as tissue, skeleton, mucus and surrounding water. They work together as a complementary community to create the circle of healthy life for coral reefs. In addition to their role in carbon, nitrogen and sulfur cycling, metabolism and defence, their pattern of abundance and diversity shapes coral resilience and adaptation to the changing environment. As coral reefs are facing a tremendous decline by climate change and human activities, we here review the motors shifting the pattern of natural coral microbiome, and how this microbiome shift could affect coral health or drive coral adaptation to both climate change and anthropogenic disturbances. The available coral restoration techniques and their limitations are also discussed, particularly the new arising trend of coral restoration through coral microbiome. After presenting the high value of microbial community in maintaining coral reef health, we suggest that coral restoration through their microbiome could be a self-sustaining tool in fighting worldwide coral decline and urge scientist to draw more attention toward this new approach.

Microbial community shift on artificial biological reef structures (ABRs) deployed in the South China Sea

“…In aquatic networks, microbial biofilms are the initial manufacturers that provide the biochemical needs and support the settlement and recruitment of eukaryotic larvae and algal spores 6 , 15 . Physical, biological and chemical factors govern the formation, development and succession of microbial biofilm 16 .…”

The bacterial signature offers vision into the machinery of coral fitness across high‐latitude coral reef in the South China Sea

“…As corals have an active relationship with these various associates, (Brener-Raffalli et al, 2018), corals acclimatize to broad environmental pressures by rearrangement of their microbiome (specifically the assembly of the bacteria and Symbiodiniaceae) (Ziegler et al, 2019). Understanding the community composition of symbiotic bacteria and its fluctuations is exclusively significant to understand the acclimatization of corals to diverse ecological conditions and their tolerance to climate change, which in consequence, support the hypothesis of using coral microbiome for coral restoration (Mohamed et al, 2022). Biotic and abiotic features have shown to influence the assembly of bacterial communities in corals (Garren & Azam, 2012;Mouchka et al, 2010;Sharp & Ritchie, 2012).…”

“…Apart from climatic disturbances, human impact also has a dramatic effect on the general coral health and its associated microbiome worldwide such as ocean acidification, elevation of inorganic nutrition level, introduction of organic compounds through sewage, and sedimentation. Land use and fishing are also associated with rearrangements of the microbial multiplicity (Lamb et al, 2015 ; Mohamed et al, 2022 ). Also some studies reported that pH decline from 8.2 to 7.3 stimulated the growth of the pathogenic bacteria Vibrionaceae and Alteromonadaceae in Acropora eurystoma coral but not Gammaproteobacteria nor Cyanobacteria (Muscatine et al, 1989 ).…”

Anthropogenic nitrogen pollution threats and challenges to the health of South Asian coral reefs

“…As each organism has its own physiological traits, the overall health of the holobiont can be disrupted by changes in the local environment impacting one or more of the individual component species. The significance of the holobiont model for understanding coral nitrogen demand lies in the emerging, yet poorly understood, relationship between the community of microorganisms contributing to the holobiont and how nitrogen is cycled and regulated within corals (Glaze et al, 2022;Mohamed et al, 2022). Recent studies indicate that the holobiont microbial community may be key to regulating fluctuations in environmental nitrogen availability and in maintaining the critical relationship between the coral host and its endosymbionts (Tilstra et al, 2021).…”