Less Invasive New Coral Polyps Sampling To Help With Reef Restoration and Management

Coral reefs are among Earth's most diverse and productive ecosystems, providing habitat for many marine species and protection for coastal communities.

However, coral reefs are also facing multiple threats, such as climate change, ocean acidification, pollution, and overfishing, that can affect their health and resilience.

To better understand how corals cope with these stressors, researchers need to study their biochemical composition, reflecting their physiological state and ecological interactions.

However, traditional methods of sampling corals are often invasive and destructive, requiring large pieces of coral tissue to be removed and processed in the laboratory.

These methods also limit the spatial resolution and accuracy of the biochemical analyses, as they do not account for the heterogeneity and variability of corals within and among colonies.

A new approach to sampling corals

(Photo : YURI CORTEZ/AFP via Getty Images)

A team of researchers from the University of Hawai'i (UH) at Mānoa has developed an innovative new approach to sampling corals that overcomes these limitations.

Their study was published in Communications Biology.

The researchers used a technique called microsampling, which involves collecting individual coral polyps using a small metal punch.

A coral polyp is the basic unit of a coral colony, consisting of a cylindrical body with a mouth surrounded by tentacles.

Each polyp is about 1 millimeter in diameter and hosts symbiotic algae that provide most of the coral's energy through photosynthesis.

By microsampling corals, the researchers were able to obtain high-resolution maps of coral biochemistry that reveal the distribution of compounds that are integral to the healthy functioning of reefs.

These compounds include amino acids, which are the building blocks of proteins; metabolites, which are involved in various biochemical reactions; and secondary metabolites, which have diverse functions such as defense, communication, and growth regulation.

The researchers used sophisticated chemical analyses, such as liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR) spectroscopy, to identify and quantify the biochemicals in each polyp.

They then mapped them back to their respective coral colony locations using digital image analysis software.

With this, they created maps of biochemicals in corals across multiple spatial scales-from individual polyps to 100-meter-long reefs.

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Insights into coral biochemistry and ecology

The researchers applied their microsampling technique to two common coral species in Hawai'i: Montipora capitata and Porites compressa.

They sampled corals from different locations in Kāneʻohe Bay, Oʻahu, Hawai'i, which is a highly variable and dynamic reef environment.

They found that the biochemical composition of corals varied significantly among polyps, branches, colonies, and sites.

They also discovered that the biochemical variation was mainly driven by molecules that came from the coral animal rather than the symbiotic algae.

The researchers were able to identify several biochemical patterns that reflect the ecological characteristics of corals.

For example, they found that M. capitata had higher levels of amino acids than P. compressa, which could be related to their different growth rates and nutrient uptake strategies.

They also found that corals had higher levels of secondary metabolites at sites with higher wave exposure and sedimentation, which could indicate a higher need for defense and stress response.

Furthermore, they found that corals had higher levels of metabolites involved in energy production and storage at sites with lower light availability, which could reflect a higher reliance on heterotrophy (feeding on organic matter) rather than photosynthesis.

The researchers also compared their microsampling technique with conventional methods of sampling corals.

They found that microsampling was much less invasive and damaging than other methods, meaning that they could take more samples and repeat sampling efforts more often with less impact on the coral.

They also found that microsampling provided much higher resolution and accuracy than other methods, allowing them to detect subtle biochemical differences among polyps that would otherwise be missed or averaged out.

Implications for coral reef research and management

The researchers believe that their microsampling technique is a powerful tool for studying coral biochemistry and ecology at unprecedented scales.

They hope that their technique will enable more comprehensive and detailed investigations of how corals respond to environmental changes and stressors, such as warming, acidification, bleaching, disease, and pollution.

They also hope that their technique will facilitate more effective coral reef management and conservation strategies, such as identifying resilient or vulnerable corals, monitoring coral health and recovery, and selecting suitable corals for restoration or transplantation.

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