Beneath the surface of the ocean, marine creatures constantly release invisible molecules. The chemical composition of these molecules reveals which organisms are nearby, while others have the potential as medicines.

The Complexity of Seawater

A drop of seawater can be compared to a spoonful of dilute soup, which resembles an intricate blend of dissolved molecules from different ocean-dwelling creatures. Peter J. Wangersky from the University of Victoria describes seawater as a medium complex enough to dismay analytical chemists.

For many years, scientists have found it challenging to analyze the chemical composition of seawater due to the complexity and dynamic nature of marine environments. Because of this, they struggle to understand the influence of seawater's chemical composition on the functions of marine ecosystems.

To identify the nature of these molecules, experts need to capture and concentrate the compounds. However, many underwater environments, particularly those with unique and potentially bioactive compounds, are threatened.

Ocean scientists have tried to unveil the complex nature of seawater by measuring how it has changed and interacted with the biosphere since the first form of life appeared on our planet. Still, it remains a challenge to identify molecules that get diluted in seawater because of the uncertainties of their origins and their possible biotransformations. The task is even made more daunting by the low abundance of these unknown molecules and the scarcity of related spectral data.

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Water-Sniffing Device

To respond to this challenge, a team of researchers developed a proof-of-concept device that can 'smell' underwater and trap dissolved compounds for analyses. The team, led by Thierry Pérez and Charlotte Simmler, tried to detect molecules present in underwater caves and investigate their potential for drug discovery.

The team developed an underwater instrument that captures and enriches dissolved compounds made by sponges and other marine creatures without harming their source and their habitats. It was made to be waterproof so it can be easily handled by an underwater diver and pump seawater through disks. Its mechanism has a similar feel and thickness as make-up remover pads, as the disks adsorb dissolved molecules for subsequent analysis.

The instrument, In Situ Marine moleculE Logger (I-SMEL), was tested in 65-foot-deep Mediterranean Sea caves containing different species of massive sponges. The researchers obtained water samples and assessed the captured compounds with mass spectrometry.

It was discovered that the compounds had diverse elemental compositions and unknown molecular structures, which show potential for learning new natural products. The scientists examined three species of sponges in detail, and they were found to contain several metabolites, such as furanoterpenoids and brominated alkaloids.

From their study, the experts reported that the I-SMEL represents a non-invasive approach to capturing molecules of interest. It also helps provide insights into an ecosystem's overall health and detect new molecules for drug discovery, marking a significant step forward in marine biology and pharmacology. The team plans to adapt the device for autonomous long-term seawater filtration and remote operations in deeper ocean regions.

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