by Penelope Nozithelo Moyo

Approximately 70% of the earth is covered by oceans, making them one of the most precious resources. Oceans play an important role in controlling weather patterns, regulating climate, providing oxygen, capturing carbon, providing food security, providing job security, fostering economic growth and most importantly, oceans are the largest habitat on the planet, (Costanza, 1999; Bigg et al., 2003; Schmitt, 2018). 

The world's oceans are home to an extraordinary diversity of life, filled with life from microscopic organisms to the largest mammal on Earth. From the beautiful coral reefs, we find in the Indian and Pacific Oceans to the lush mangrove forests of the tropics, marine ecosystems support countless species, including those dwelling in the deepest darkest depths of the ocean. While all marine life is important, some species garner more attention than others. Today, we celebrate one of the ocean's unsung heroes: seagrass. 

Seagrass plays a crucial role in shaping and maintaining marine environments

Seagrass is an often-forgotten aquatic plant, yet it is one of our oceans' most essential species. As the only flowering marine plant that inhabits coastal zones across all continents except Antarctica, seagrass has successfully colonised all bioregions. It is classified as a foundation species due to its crucial role in shaping and maintaining marine environments (Reynolds, 2018). There are approximately 72 species of seagrass, ranging from temperate species such as Zostera marina (North Atlantic and North Pacific Oceans) and Cymodocea nodosa (Mediterranean Sea) to tropical species like Enhalus acoroides (Indo-Pacific region) and Thalassia testudinum (Caribbean and Gulf of Mexico region).

Seagrass ecosystems are among the largest producers of oxygen in the oceans 

Seagrass meadows provide a range of ecological benefits, including sustaining fisheries by serving as a habitat for commercially valuable juvenile fish, clams and shrimp. Furthermore, seagrass ecosystems are among the largest producers of oxygen in the oceans, playing a crucial role in maintaining oxygen levels and supporting marine life. Seagrass meadows play a vital role in climate change mitigation by capturing carbon dioxide (Cullen Unsworth et al., 2018) and protecting coastlines by reducing soil erosion caused by storm surges, tidal forces and wave action (Hoffle et al., 2011). Additionally, the leaves and stems of seagrass function as a source of food for marine species such as manatees, sea turtles and dugongs. Seagrass further enhances water quality by trapping sediment, thereby improving water clarity, facilitating nutrient cycling, and stabilising sediment (Neto et al., 2013). However, despite their ecological importance, seagrass meadows are declining at an alarming rate and are considered one of the most threatened ecosystems (Mckenzie et al 2020; Santos et al., 2019; Moyo, 2023).

The leaves and stems of seagrass function as a source of food for marine species such as manatees, sea turtles and dugongs.

Research has shown that seagrass meadows are diminishing due to human activities that physically damage the plants and alter water quality, sediment composition and hydrodynamic conditions (Duarte, 2002; Unsworth et al., 2014; Floor et al., 2018; Govers et al., 2022). The destruction of seagrass habitats threatens the invaluable services they provide to marine ecosystems and human communities.

While some loss may be attributed to natural factors such as diseases and pathogens (Labyrinthula zosterae) (Orth et al., 2006, Brakel et al., 2019; Floor, 2018) or extreme weather events like storms and strong waves that uproot seagrass beds (Cote-Laurin et al., 2017, James et al., 2021, Moyo, 2023), human-induced factors remain the primary drivers of seagrass decline. Coastal pollution and eutrophication promote algal blooms that hinder growth, while coastal development and habitat modification contribute to sediment instability and increased turbidity (Duarte, 2004). Activities such as dredging and sand extraction uproot seagrass and elevate turbidity levels, further compromising its survival (Erftemeijet & Lewis, 2007). Since seagrass thrives in clear, unpolluted waters, these disruptions pose significant threats to its continued existence.

The importance of seagrass is undeniable, and the threats to this ecosystem necessitate urgent action. Protecting seagrass meadows is essential for conserving species that depend on them, including sea turtles, manatees, and numerous fish species. Conversation efforts should focus on habitat protection, and restoration projects that involve replanting seagrass and reducing pollution sources that degrade coastal environments. Additionally, public education and awareness campaigns are crucial in fostering a broader understanding of the ecological significance of seagrass and encouraging collective conservation efforts.

As we celebrate World Seagrass Day this March, let us take meaningful action to protect and restore seagrass meadows. Through advocacy, conservation initiatives, and public engagement, we can safeguard this vital marine ecosystem for future generations. 

References  

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