Saving coral reefs: significance and biotechnological approaches for coral conservation

Abstract

Coral reefs are highly productive ecosystems that provide valuable services to coastal communities worldwide. However, both local and global anthropogenic stressors, threaten the coral-algal symbiosis that enables reef formation. This breakdown of the symbiotic relationship, known as bleaching, is often triggered by cumulative cell damage. UV and heat stress are commonly implicated in bleaching, but other anthropogenic factors may also play a role. To address coral loss, active restoration is already underway in many critical regions. Additionally, coral researchers are exploring assisted evolution methods for greater coral resilience to projected climate change. This review provides an overview of the symbiotic relationship, the mechanisms underlying coral bleaching in response to stressors, and the strategies being pursued to address coral loss. Despite the necessity of ongoing research in all aspects of this field, action on global climate change remains crucial for the long-term survival of coral reefs.

Keywords: Climate change; Conservation; Coral; Coral bleaching; Resilience; Symbiosis; Zooxanthellae.

Fig. 1

(A) Coastal reefs, such as the one shown in the aerial view from Makapu'u, O'ahu, Hawai'i, provide many benefits including tourism, fishery, and coastal protection. (B) Serious coral bleaching was observed in photos from coral reefs at the Makapu'u Beach Park, O'ahu. Partially bleached and threatened coral reefs at (C) Molokini, Māui and (D) Captain Cook Monument, the Island of Hawaiʻi. Photos taken by Z.D. in 2022

Fig. 2

(A) Diagram of a coral polyp showing where the algal symbionts reside. (B) Simplified schematic of the metabolic relationship of Symbiodiniaceae. They reside in the gastrodermal cells of coral polyps. (C) Free-living symbionts of species Breviolum minutum. Each cell is roughly 10 μm in diameter

Fig. 3

Summary of the commonly known causes of coral bleaching. More details on the mechanisms of each cause are provided in Table 1

Fig. 4

The web of strategies to address coral loss and the synergistic interactions between them. Strategies are characterized as either primarily restoration or assisted evolution. Benefits conferred from one strategy to another are indicated by an arrow in the direction of the benefit. Wide-scale benefits not depicted in the figure include the genetic characterization to inform restoration efforts from assisted evolution research and the availability of coral for experimentation supplied by restoration practices