How a Deep Sea Sensor Detected Reactive Oxygen Species Produced by Corals?

Until recently, whether healthy deep-sea corals generate a specific type of reactive oxygen species (ROS) known as superoxide (O₂^•-) remained a mystery. Superoxide is a highly reactive ROS recognized for its impact on ocean ecology, organism physiology, and its role in driving chemical processes in the ocean, such as carbon breakdown and the availability of metals and nutrients.

A recent study, featured in PNAS Nexus, sheds light on this question, revealing that deep-sea corals and sponges indeed produce the ROS superoxide. This newfound knowledge implies a series of previously undisclosed effects on ocean life and chemistry in the deep sea. The study establishes that ROS production is not solely a stress response in these organisms but an integral aspect of their normal functioning.

To directly measure superoxide in the immediate vicinity of corals, the researchers utilized a unique deep-sea chemiluminescent sensor named SOLARIS. This innovative sensor was deployed over 2,000 meters deep in the ocean aboard the Alvin submersible, providing unprecedented insights into the production of superoxide by deep-sea corals and sponges.

Colleen Hansel, the senior scientist specializing in Marine Chemistry and Geochemistry at the Woods Hole Oceanographic Institution (WHOI) and the senior author of the study, emphasizes the significance of their findings. The team’s use of the SOLARIS sensor during the study represents the inaugural measurements of superoxide, a key chemical, in the deep sea. This achievement marks a groundbreaking contribution to our understanding of the chemical dynamics in deep-sea environments.

The detection of superoxide in the ocean posed a unique and formidable challenge that demanded collaborative expertise spanning disciplines from chemistry and physics to engineering. Superoxide, being a highly reactive compound, has a fleeting presence in water, lasting only seconds. To overcome this challenge, WHOI Engineers Jason Kapit and William Pardis, in collaboration with Colleen Hansel and Associate Scientist Scott Wankel, engineered the SOLARIS system. This robotically controlled instrument is adept at drawing water directly from the surface of coral.

The water is then channeled into a detection wand and mixed within a chamber, where a chemical reaction with superoxide generates measurable light in real time. During the expedition, the mechanical arms of the Alvin submersible were employed to control the movements of the wand. Jason Kapit and Colleen Hansel, integral members of the three-person team aboard the Alvin, played key roles in orchestrating this innovative approach to capture real-time measurements of superoxide in the deep-sea environment.

Jason Kapit highlights a notable facet of this project, underscoring the distinctive synergy between science and engineering that characterizes WHOI’s approach. The collaboration between scientific inquiry and engineering innovation, as seen in this study, reflects the institution’s unique capacity to integrate these disciplines seamlessly for groundbreaking research initiatives.

In October 2019, the initial dives employing SOLARIS took place in the Monterey Bay National Marine Sanctuary off the California coast. The exploration revealed the presence of large, thriving corals within a protected ocean environment, dispelling the notion that superoxide production was solely a stress response.

Colleen Hansel explains that the measured corals were generating superoxide through an enzyme called NOX. This enzyme operates outside the cells, suggesting that superoxide is likely a fundamental aspect of their routine life functions. Whether it involves growth or potentially stunning prey, these deep-sea corals, unlike their shallow counterparts with algal symbionts, rely on NOX for superoxide production. These findings challenge the previously assumed origin of extracellular ROS in shallow corals, thought to be attributed to symbiotic algae. The study excludes algae as the source of superoxide, pointing instead to the coral animal itself or its bacterial symbionts. While the role of bacteria in ROS production isn’t entirely ruled out, the presence of NOX within these corals suggests it is unlikely.

Lina Taenzer, a Joint Program Student specializing in Marine Chemistry & Geochemistry and the lead author of the study, discusses the evolving understanding of extracellular reactive oxygen species (ROS) production. Over the last decade, research efforts have increasingly identified potential beneficial aspects of ROS, such as superoxide, within organisms. Taenzer, who joined Colleen Hansel’s lab at WHOI in 2019 and participated in Alvin dives to measure superoxide using SOLARIS, emphasizes the growing body of studies shedding light on the positive roles played by these compounds in various organisms.

Lina Taenzer underscores the intriguing ability of corals to regulate reactive oxygen species (ROS), emphasizing that corals can employ ROS signaling to communicate with other cells and modulate their functionality in response to the environment. This intricate regulatory mechanism also serves as a cellular defense mechanism. For instance, when facing a pathogenic invasion, organisms may generate a robust oxidative burst, essentially engaging in chemical warfare to safeguard themselves.

Taenzer further delves into the dual nature of superoxide production. While it can serve as a vital defense mechanism, an excess of superoxide can have adverse effects on an animal. This surplus can lead to the degradation of essential proteins within the body and the breakdown of DNA, highlighting the delicate balance that organisms must maintain in managing ROS for optimal cellular function and defense.

While diving in Alvin, Lina Taenzer took advantage of serendipitous opportunities to measure a diverse array of species. This included sponges and sea stars, highlighting the significance of species diversity in their exploration and study of superoxide production in the deep sea.

Lina Taenzer expresses the excitement and satisfaction derived from the exploration aspect and the use of a novel instrument during their study. The thrill of employing a previously unused tool, combined with the spirit of exploration, added an extra layer of excitement and fulfillment to their scientific endeavors.

Despite the remaining uncertainties about the functioning and responses of deep-sea corals to their environment, this study contributes valuable insights into the foundational factors influencing coral health and activity. The continual sharing and understanding of such scientific knowledge play a pivotal role in enhancing scientists’ ability to predict how coral ecosystems will react to the challenges posed by warming seas and climate change.

Colleen Hansel underscores the challenge of accurately modeling coral responses to changing ocean conditions without a comprehensive understanding of their current functioning under baseline conditions. To improve predictive models, it is crucial to establish a foundational understanding of the characteristics of a healthy coral versus a sick coral. Additionally, identifying the factors that exert control over the health and physiology of these organisms is essential. This knowledge serves as a critical foundation for developing effective strategies to safeguard coral ecosystems in the face of environmental changes.

The overarching objective is to employ SOLARIS for measuring reactive oxygen species (ROS) in corals, deep-sea sponges, and other ROS-producing organisms across various global regions. By doing so, researchers aim to obtain a comprehensive understanding of the ways in which marine life contributes to and influences ocean chemistry. This ambitious goal underscores the broader applications of SOLARIS in advancing our knowledge of diverse marine ecosystems and their impact on the intricate chemistry of the world’s oceans.

The ultimate objective is to leverage SOLARIS for the assessment of ROS production in corals, deep-sea sponges, and other organisms across various global regions. This ambitious goal aims to compile a comprehensive understanding of how marine life, through its influence on ocean chemistry, contributes to ecosystem dynamics on a broader scale.

Colleen Hansel highlights the potential ramifications of discovering highly reactive compounds in the deep ocean, emphasizing their potential impact on critical processes such as carbon cycling, metal cycling, and microbial ecology. While the specifics remain uncertain at this point, the prospect of these findings influencing various aspects on a larger scale is both intriguing and exciting for researchers in the field.

Resources

1. ^{ONLINE NEWS} Woods Hole Oceanographic Institution. (2023, December 4). Deep sea sensor reveals that corals produce reactive oxygen species. Phys.org. [Phys.org]
2. ^JOURNAL Taenzer, L., Wankel, S. D., Kapit, J., Pardis, W., Herrera, S., Auscavitch, S., Grabb, K. C., Cordes, E. E., & Hansel, C. M. (2023). Corals and Sponges are Hotspots of Reactive Oxygen Species in the Deep Sea. PNAS Nexus, 2(11). [PNAS Nexus]

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