Revealing the Role of Silicon in Seagrasses: A New Horizon for Understanding Biogeochemical Cycles in Coastal Ecosystems

02/02/2025

A recent study, led by an international team involving researchers from the Institut Mediterrani d'Estudis Avançats (IMEDEA, CSIC-UIB), has shed new light on the role of silicon in seagrasses, particularly in the species Zostera marina. The findings highlight the ability of these plants to accumulate two operational types of biogenic silica (bSi): a labile form, easily recyclable, and a resistant form, which contributes to silica storage in sediments.

The recently published work used for the first time two chemical digestion methods-alkali and hydrofluoric acid (HF)-to quantify silica content in Zostera marina leaves. The results showed that 0.26% of the dry weight of the leaves corresponds to silicon, an amount comparable to other silicified organisms in the ecosystem.

 

Implications for Biogeochemical Cycles

This discovery underscores the key role of seagrasses in the silicon cycle. The labile silica, released as leaves degrade, benefits silicified organisms such as diatoms and sponges, while the resistant fraction is integrated into silica deposits buried in sediments, potentially contributing to carbon sequestration.

In Brest Bay (France), where the study took place, the silicon content of seagrasses was estimated at 0.18 ± 0.07 g Si m-², a value similar to that of benthic diatoms, which reinforces the importance of Zostera marina as a silicon reservoir in the land-ocean continuum.

Image: One of the researchers collects samples in the Bay of Brest, France. Author: MariaLopez Acosta (IIM-CSIC)

 

A Call for Further Research

Despite these advances, the study highlights the need to investigate the specific mechanisms of silica deposition in Zostera marina and the impact of environmental factors such as leaf age or the concentration of dSi (dissolved silicon) in the water. In addition, it is suggested that seagrasses could act as buffers in the transport of silica into the oceans, in a global context of dSi depletion due to human activities.

Image: One of the researchers collects samples in the Bay of Brest, France. Author: MariaLopez Acosta (IIM-CSIC)

 

Conservation and Restoration

Seagrasses are disappearing at a rate of 7% per year, an alarming trend that requires urgent conservation and restoration actions. This study highlights the importance of including the silicon cycle as an integral part of management strategies for these vital ecosystems for climate change mitigation and marine biodiversity.

 

Link to the full study: 

https://link.springer.com/article/10.1007/s10533-024-01189-1