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01-28-2024

Seagrasses are the unsung heroes of oceans and marine life

A new study has revealed significant insights into the evolutionary adaptability of marine flowering plants, commonly known as seagrasses. 

The pioneering research was focused on the genomic analysis of three major seagrass species: Neptune grass (Posidonia oceanica), Little Neptune grass (Cymodocea nodosa), and Turtlegrass (Thalassia testudinum).

Crucial ecosystems 

Seagrasses play a crucial and often overlooked role in coastal ecosystems. They provide stability against erosion, serve as vital habitats for diverse marine life, and mitigate climate change through carbon storage

The alarming rate at which these vital ecosystems are disappearing, comparable to the loss of coral reefs, has spurred intense research into their conservation and restoration.

The study was conducted by an international consortium of 38 researchers led by Dr. Yves Van de Peer (Ghent University), Dr. Jeanine Olsen (University of Groningen), Dr. Thorsten Reusch (GEOMAR Helmholtz Centre for Ocean Research Kiel), and Dr. Gabriele Procaccini (Stazione Zoologica Anton Dohrn of Napoli).

Evolutionary journey of seagrasses 

The research involved a comprehensive examination of the genome structure of seagrasses, followed by a comparison of gene families and pathways linked to their unique structural and physiological adaptations to marine environments. 

This approach contrasted the seagrasses with their freshwater counterparts, shedding light on the evolutionary journey of these marine plants.

“Seagrasses underwent an extremely rare set of adaptations. Whereas re-adaptation to freshwater environments has occurred more than 200 times in flowering plant evolutionary history — involving hundreds of lineages and thousands of species — seagrasses evolved from their freshwater ancestors only three times — involving 84 species,” said Dr. Olsen.

“To do this required specialized ecological tolerance to, for example, high salinity, lower light, a wide range of temperature tolerances, underwater carbon capture for photosynthesis, different pathogen defense, structural flexibility and an underwater pollination.”

Seagrasses rapidly adapt

A key finding of the study is the role of genome duplication in facilitating rapid adaptation to new environments. 

“Comparison of the three independent seagrass lineages, including freshwater sister lineages, revealed a shared ancient whole genome triplication at about 86 million years,” said Professor Dr. Van De Peer.

“This was quite exciting because large parts of the ocean were oxygen-free at that time and it’s also a uniting event involving the three lineages.”

Jumping genes

The research also uncovered how seagrasses have adapted through the retention and expansion of certain gene families.

These adaptations include the development of flavonoids for UV and fungal protection, cysteine oxidases for coping with low oxygen environments, and genes associated with circadian rhythms. 

Furthermore, the study found that “jumping genes” – transposable elements – have played a significant role in generating genetic diversity for natural selection.

“It’s clear that fine-tuning of supportive pathways has played the dominant role, rather than genes taking on major new functions,” said Dr. Procaccini.

“Salt-tolerance is a good example in which a higher efficiency of multiple processes has occurred to regulate sodium, chlorine and potassium. Evolutionary changes have also provided different species with the ability to withstand different environments.”

Significance of conserving seagrasses

The research team identified several adaptations resulting from convergent evolution.

This includes the loss of genes for traits that became redundant or detrimental in the marine environment, such as stomata for gas exchange and certain pathogen defense mechanisms.

These findings exemplify the principle of “use it or lose it” in evolutionary biology.

“Most ecologically important functions are complex traits, involving the interaction of many genes through flexible pathways. With genomic tools now developed for key seagrasses, we can begin to experimentally test and manipulate them,” explained Dr. Reusch.

“This is especially important for restoration under climate change scenarios involving many of the conditions discussed here.”

More on the importance of seagrasses

As discussed above, seagrasses, often unnoticed and undervalued, play a crucial role in the health of marine ecosystems.

These underwater plants, thriving in shallow, sheltered marine environments, are biodiversity hotspots and vital to environmental health.

Unsung heroes of carbon sequestration

Seagrasses are powerful carbon sinks. They capture carbon dioxide from the atmosphere at a rate much faster than tropical rainforests.

This process, known as carbon sequestration, is pivotal in mitigating climate change. The carbon absorbed by seagrasses gets stored in the sediments below them, often remaining trapped for centuries.

Thus, protecting and restoring seagrass meadows is not just beneficial; it’s imperative for our fight against global warming.

Biodiversity and habitat provision

Seagrass meadows provide a home and breeding ground for a myriad of marine species. They serve as nurseries for numerous fish species, many of which are important for commercial fishing industries.

This rich biodiversity includes not just fish, but also crustaceans, mollusks, and even endangered species like manatees, seahorses and turtles.

The dense root and leaf systems of seagrass beds offer shelter and food, creating a vibrant, diverse ecosystem.

Water quality and sediment stabilization

Seagrasses play a key role in maintaining water quality. Their leaves filter suspended particles from the water, enhancing its clarity and quality.

This filtration process benefits both the marine organisms that live there and the humans who rely on these waters for recreation and livelihoods.

Furthermore, the complex root systems of seagrasses stabilize the seabed. They prevent erosion by anchoring the sediment, which is especially crucial in coastal areas where erosion can be a significant problem.

This stabilization also helps to maintain clear water conditions, which is necessary for the growth of underwater life, including the seagrasses themselves.

Conservation challenges and a call to action

Despite their importance, seagrasses face numerous threats. Pollution, coastal development, and destructive fishing practices, like trawling, have led to a dramatic decline in seagrass meadows globally.

Climate change, causing rising sea temperatures and ocean acidification, further exacerbates the problem.

The conservation of seagrasses is a vital step in preserving marine biodiversity, fighting climate change, and protecting our coasts. It requires concerted efforts from governments, environmental organizations, and communities.

Public awareness plays a key role in this endeavor. Understanding the importance of seagrasses can lead to more mindful practices regarding pollution and coastal development.

Scientific research and monitoring are essential for the effective management and restoration of these vital ecosystems.

Restoration projects have shown promising results in several parts of the world, demonstrating that with proper care and attention, these vital ecosystems can recover.

In summary, seagrasses are absolutely fundamental to the health of our planet. They support marine life, protect coastlines, improve water quality, and fight against climate change.

The protection and restoration of seagrass meadows should be a priority in global environmental conservation efforts.

By understanding and valuing these vital ecosystems, we can take significant steps towards a healthier, more sustainable planet.

The study is published in the journal Nature Plants

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