Beyond the microscope: Beneficial microbes to save and sustain corals

July 24, 2023

As you dive beneath the azure waves into the mesmerising underwater world, you are likely to be spellbound by the breathtaking beauty of coral reefs. Vast cities of nature, teeming with vibrant life, these reefs are not just scenic wonders but are also crucial lifelines for our planet. They offer sanctuary to countless marine species, stand as protectors against coastline erosion, and crucially, help maintain the intricate balance of our oceanic ecosystems. Yet, these awe-inspiring structures are under siege. Climate change, pollution, and a slew of other human-induced challenges are threatening their existence.

In the race against time to preserve these fragile ecosystems, scientists across the globe are continuously probing for effective solutions. Among their innovative approaches, one of the most promising strategies has emerged from an unexpected realm: the microscopic world. Beneath the surface, in a domain invisible to the naked eye, lie potential heroes in the form of beneficial microbes or BMCs (Beneficial Microorganisms for Corals).

Join us as we take this fascinating journey into the microscopic world of BMCs, unraveling the extraordinary ways in which these tiny organisms can help restore and enhance the resilience of our precious coral reefs, akin to how their cousins help rejuvenate our soils on land. This cross-kingdom comparison provides a powerful lens through which we can appreciate the universality of life’s interconnectedness and our role in its preservation.

Coral reefs: Majestic ecosystems under threat

Coral reefs are some of the most diverse and valuable ecosystems on Earth, often hailed as the “rainforests of the sea.” Occupying less than 1% of the ocean floor, they are home to an astonishing 25% of all marine species. These underwater cities offer a habitat for a vast array of organisms including fishes, mollusks, crustaceans, and more.

Beyond their biodiversity, coral reefs also provide immense ecological services. They serve as crucial barriers protecting coastlines from the damaging effects of wave action and tropical storms, preventing erosion, property damage, and loss of life. Economically, they contribute billions each year, supporting commercial and subsistence fisheries as well as tourism and recreation. Additionally, they are potential treasure troves of medicinal compounds, some of which are being used to develop treatments for various illnesses, including cancer.

However, these magnificent ecosystems are facing an unprecedented crisis. Rising sea temperatures due to global warming are causing coral bleaching, a phenomenon in which corals expel the symbiotic algae living within their tissues, leading to a decline in coral health and potentially death. Overfishing and destructive fishing practices are damaging reefs and depleting fish populations. Land-based pollution, including agricultural runoff and plastic waste, is smothering corals and encouraging the overgrowth of harmful algae.

Furthermore, ocean acidification – a result of increased carbon dioxide (CO2) emissions – is making it more difficult for corals to build their calcium carbonate skeletons. Disease outbreaks are becoming more frequent and severe, likely due to a combination of stressors, including warmer waters and pollution. All these factors combined have led to a dramatic loss of coral reef ecosystems around the world, threatening not only the species that directly rely on them, but also the human communities that benefit from the services they provide.

In the face of these mounting threats, the scientific and conservation communities are fervently exploring innovative solutions to protect and restore these vital ecosystems, which brings us to the promising world of beneficial microorganisms for corals, or BMCs.

The coral holobiont: A symbiotic symphony of life

The coral ecosystem thrives as a result of an intricate collaboration known as “The Coral Holobiont.” At its core lies the humble coral polyp, a tiny, soft-bodied organism related to sea anemones and jellyfish. These unassuming creatures secrete a hard, protective limestone skeleton, which over generations, forms the magnificent, sprawling structures we know as coral reefs.

Within the tissues of the coral polyp, resides a microscopic, single-celled algae known as zooxanthellae. This iconic partnership represents one of the most well-known symbiotic relationships in the ocean. The coral provides the algae with a safe and nutrient-rich habitat, while the algae reciprocate by harnessing sunlight for photosynthesis. In doing so, they produce essential compounds like glucose, glycerol, and amino acids, which significantly contribute to the coral’s nutrition and overall health.

The coral holobiont extends beyond this dynamic duo, encompassing a diverse range of microorganisms. Known as the coral microbiome, these bacteria, archaea, fungi, and viruses play an indispensable role in coral health. They facilitate nutrient cycling, defend against pathogens, and bolster stress tolerance, harmoniously working together to support the coral polyp and its algae partners.

This captivating synergy, spanning from microscopic organisms to crustaceans, fish, and worms, creates a vibrant and interdependent community, much like a living orchestra, harmonising together in the coral reef symphony. Appreciating the profound intricacy of these relationships is fundamental to understanding coral biology and their responses to environmental changes. As we dive deeper into the realm of Beneficial Microorganisms for Corals (BMCs), we unveil the potential of this knowledge in pioneering innovative strategies for coral conservation. Embracing the power of these microscopic allies, we set our sights on safeguarding these fragile ecosystems for generations to come.

Coral probiotics using beneficial microbes

There is a diverse array of microorganisms that contribute to coral health. Among them, a subset of particularly beneficial microbes known as Beneficial Microorganisms for Corals, or BMCs, have been identified. BMCs are defined as consortia of microorganisms that promote coral health through various mechanisms. Some enhance coral nutrition and growth, others aid in stress mitigation, deter pathogens, and support early life-stage development.

Identifying potential BMCs is a complex process involving both laboratory-based and in-situ research. Scientists first survey the microbial communities associated with healthy and stressed corals, employing advanced techniques like metagenomic sequencing to identify different types and functions of microbes. By comparing these communities, potential BMCs that are more prevalent in healthy corals are identified. Once potential BMCs are pinpointed, they undergo further scrutiny in the lab. Researchers study their roles and interactions with corals and other microorganisms, evaluating their impact on growth, disease resistance, and response to environmental stressors. Promising BMCs are then tested on corals in controlled environments before conducting real-world trials to confirm their efficacy and safety.

Through this rigorous process, scientists aim to select only the most effective and safe BMCs for use in coral conservation strategies. The potential of BMCs as a tool to safeguard and restore coral reefs presents a beacon of hope in the race to protect these invaluable marine ecosystems.

The multifaceted roles of BMCs in coral health and resilience

We will take a closer look at the specific ways in which BMCs support the health of their coral hosts. Much like beneficial soil bacteria that aid plant growth by aiding nutrient uptake, fighting off plant pathogens, and helping plants tolerate environmental stresses, BMCs offer similar benefits to corals.

  1. Promoting nutrition and growth: The first significant role of BMCs lies in their ability to bolster coral nutrition and growth. BMCs can enhance the efficiency of nutrient cycling within the coral holobiont, improving the coral’s access to essential nutrients. Certain BMCs are capable of nitrogen fixation, converting atmospheric nitrogen into a form that can be utilised by corals, akin to how Rhizobium bacteria assist leguminous plants.

  2. Stress mitigation: BMCs can also help corals mitigate stress, much like how soil microbes aid plants under drought conditions. When corals are under environmental stress due to factors like increased sea temperature or pollution, the role of BMCs becomes pivotal. They help in mitigating the stress responses, boosting the corals’ resilience and improving their survival chances.

  3. Deterring pathogens: BMCs play a crucial role in pathogen deterrence. Certain BMCs can outcompete or produce antimicrobial compounds against harmful bacteria, reducing the risk of disease in corals. This can be likened to how certain soil microbes protect plants from pathogens by occupying root surfaces and outcompeting harmful microbes.

  4. Benefiting early life-stage development: Just as soil microbes aid in seed germination and early plant growth, BMCs assist in the early life-stage development of corals. They aid the metamorphosis of coral larvae into their adult form and facilitate the establishment of symbiotic algae within the tissues of young corals.

In essence, these microscopic symbionts are integral to the survival, health, and resilience of coral reefs. Their multi-faceted roles hold significant implications for coral conservation efforts, offering new, innovative ways to bolster the health of these vital marine ecosystems.

Challenges and bottlenecks in coral probiotics

While the application of BMCs holds immense promise, it is not without its hurdles. Implementing any form of biological intervention in complex ecosystems always comes with significant challenges and uncertainties.

Identifying beneficial strains: The first hurdle lies in identifying beneficial microbial strains. While we have made significant strides in this area, the sheer diversity of microbes within the coral microbiome presents a daunting challenge. Determining which of these microbes confer benefits to corals, and under what conditions, requires complex, time-consuming, and costly research.

Ensuring long-term efficacy: Another key challenge is ensuring that the introduced BMCs persist in the coral microbiome over time and continue to confer their benefits. Just like in soil probiotics, environmental factors, competitive interactions with other microbes, and the health status of the coral host can all influence the persistence of BMCs.

Assessing impacts on ecosystem: We also need to thoroughly assess any potential impacts on the broader coral reef ecosystem. While a particular microbe may benefit corals, it could have unintended negative effects on other components of the ecosystem.

Delivery mechanism: Another challenge is the delivery of these BMCs to the corals. Methods must be devised to effectively introduce the BMCs to the coral host without causing stress or harm. Delivery methods could potentially include bath treatments for corals in nurseries or direct application to reef corals, but more research is needed to optimise these methods.

Scalability: Lastly, the scalability of the BMC approach is a critical concern. While it might be possible to treat individual corals or small areas of a reef, it becomes a lot more challenging when we consider the vast scales at which coral reefs exist. We need to develop methods that can treat large areas efficiently and cost-effectively.

Despite these challenges, the potential of BMCs as a tool for improving coral health and resilience in the face of environmental stressors is enormous. With ongoing research and innovative thinking, we can continue to improve our understanding and develop strategies for overcoming these bottlenecks, paving the way for the large-scale application of this promising approach in coral conservation.

Conclusion

In conclusion, the field of Beneficial Microorganisms for Corals (BMCs) presents exciting prospects for the future of coral conservation. As we have explored, BMCs offer multifaceted roles in bolstering coral health, from promoting nutrition and growth to mitigating stress and deterring pathogens. These microscopic allies, together with the coral holobiont’s rich diversity, form a symphony of life critical to the survival of coral reefs.

Moving forward, the key priorities lie in addressing the challenges and bottlenecks associated with BMC implementation. Identifying beneficial strains, ensuring long-term efficacy, assessing ecological impacts, and devising effective delivery methods are paramount to harnessing the full potential of BMCs. Furthermore, scalability becomes crucial in deploying BMCs on larger scales to protect vast reef ecosystems.

Our understanding of the coral microbiome and BMCs is rapidly advancing, fueled by ongoing research and innovative strategies. As we gain deeper insights into these complex relationships, we must also continue our efforts in broader coral conservation to combat the root causes of reef decline, including climate change, overfishing, and pollution.

With a collaborative approach, bolstered by the power of science and innovation, we can pave the way for the large-scale application of BMCs as an invaluable tool in safeguarding and restoring the wonder that is the coral reef ecosystem. By embracing the potential of these microscopic allies, we can inspire hope for the future of coral reefs and ensure their resilience for generations to come.

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