New Strategies Aim to Boost Survival of Young Corals

Researchers are tackling a critical bottleneck in coral reef restoration: the high mortality of corals during their vulnerable early life stage. Two new studies explore innovative methods—one chemical, one architectural—to improve the survival and settlement of coral larvae.

Study 1: Chemically Enhanced Cement Tiles

A team from the University of Miami published research in Communications Earth & Environment examining the effect of cement tiles formulated with sodium carbonate on baby coral survival.

Methods and Findings

The five-month laboratory study involved growing larvae of mountainous star coral (Orbicella faveolata) on custom cement tiles. Researchers tested tiles with no sodium carbonate, 1% sodium carbonate, and 2% sodium carbonate. The chemical is intended to leach into the water, raising alkalinity and pH in the immediate microenvironment of the coral.

Tiles containing 2% sodium carbonate showed the highest performance. Coral survivorship on these tiles increased to 52%, compared to an approximate average survival rate of 12% for this species in previous work. Researchers described this as a roughly fourfold improvement in early-stage survival.

Within the test, flat tiles performed better than tiles with textures or divots.

Research Context and Next Steps

The work originated from a project funded by the Defense Advanced Research Projects Agency (DARPA). Researchers stated that raising ocean water alkalinity has previously been shown to improve coral growth, and they aimed to address high mortality in coral restoration at the juvenile stage.

• A senior author, Vivek Prakash, assistant professor of physics, described the study as a pilot demonstration of a new approach urgently needed for coral restoration.
• Lead author Melissa Ruszczyk, a former postdoctoral researcher, noted the team initially hypothesized the chemical would affect growth, not survivorship.
• The team plans to scale up the work, test the approach with other coral species, and investigate tile performance in field conditions.

Study 2: Architecturally Designed Settlement Structures

Separate research led by Despina Linaraki, an architecture lecturer, investigated how the physical design of settlement structures can influence coral larvae attachment. This research was published in the journal Architecture.

Methods and Findings

Inspired by coral polyps, the researcher created 75 prototype structures using various designs, colors, and materials. The objective was to identify designs that optimize coral larvae attachment and growth.

The prototypes were tested in partnership with Monsoon Aquatics, a land-based coral farm in Australia.

Initial outcomes from settlement trials indicated that settlement rates on the prototype tiles were, on average, four times higher than on standard flat ceramic tiles.

Expert Perspectives

• Jonathan Moorhead, head scientist at Monsoon Aquatics, stated the research reinforces that coral larvae are selective when choosing settlement locations.
• Daniel Kimberley, Monsoon Aquatics director, said understanding structures suited for different corals could improve the efficiency of cultured coral development.
• Jennifer Matthews from the University of Technology Sydney highlighted the value of interdisciplinary approaches, such as integrating architecture with marine science, for coral management strategies.

Summary of Approaches

Both research initiatives aim to overcome a key challenge in reef restoration: the high mortality of coral between the larval settlement phase and becoming established juveniles.

One study focuses on chemically modifying the substrate's microenvironment to improve survivorship, while the other explores how physical shape and design can enhance initial larval attachment.

Researchers involved in both projects indicate these approaches could become tools for improving coral restoration outcomes in both laboratory and natural reef settings.