Objective 6: Revealing Biodiversity and Connectivity in Seagrass Meadows

a) eDNA: Biodiversity Baseline and Restoration Signatures

 

What we do
Environmental DNA (eDNA) allows us to detect a wide array of organisms from trace DNA in water and sediment samples, without needing to physically catch or observe them. By sampling seagrass meadows and adjacent habitats, we can build a comprehensive picture of the species present – from small invertebrates to fish and macrofauna.

 

What we have found (baseline results) 

• Our eDNA surveys across natural seagrass meadows confirmed a high diversity of taxa, including species often missed in traditional surveys.

• We observed distinct species assemblages in seagrass sites compared to bare sandy bottoms, supporting the role of meadows as biodiversity hotspots (consistent with findings from other regions).  

• Some taxa appear uniquely or preferentially in seagrass habitats, including species known to use seagrasses as nurseries or shelters (e.g. juvenile fish, crustaceans).  

• In restoration plots (e.g. in Roches Noires), the aim is to detect “signature” taxa – species that colonize or return as the meadow recovers. This would suggest that restoration is reactivating ecological functions even at early stages.

 

Why this matters

• Biodiversity underpins ecosystem function – more species mean more stability, resilience, and capacity to respond to stress.

• eDNA gives us a sensitive, cost-effective means to monitor recovery trajectories in restored sites, detecting early signs of ecosystem rebuilding.

• It helps identify which species (or groups) may be missing, guiding targeted interventions (e.g. habitat features or connectivity corridors) to support full community recovery.

 

 

b) Microsatellite genetics: Connectivity of Key Fish Species

 

What we plan to do
To understand how fish move among meadows – and thus how restored sites integrate into the seascape – we will apply microsatellite markers to target economically important fish species that utilize seagrass habitats (e.g. juveniles or nursery-dependent species).

 

Our goals include: 

• Assess genetic structure – determining whether fish in different lagoons or meadows are part of the same population or genetically distinct.

• Estimate connectivity and gene flow – how much exchange of individuals occurs among sites (especially between restored and natural meadows).

• Link connectivity to restoration outcomes – knowing whether seagrass meadows serve as stepping stones or traps for fish movement.

• Inform management – results will help in designing seagrass networks, corridors, and marine spatial planning that maintain genetic diversity and resilience.

 

What the literature shows 

• Microsatellite studies in seagrass ecosystems have successfully revealed patterns of connectivity and population structure in seagrass-forming species (e.g. Thalassia hemprichii in the Western Indian Ocean) using a dozen or more loci.  

• The approach is widely used in “seascape genetics,” combining genetic data with oceanographic models to understand dispersal pathways and barriers.  

• Dispersal in fish is often shaped by currents, habitat continuity, larval duration, and behavioral preferences, so genetic structure may reflect both ecological and physical seascape features. 

 

Because the connectivity study in Mauritius has not yet started, we will be cautious in our predictions, but the framework is ready. Early sampling will focus on priority fish species, ideally ones with some known dependence on seagrass as nursery habitat or juvenile refuge. Over time, we will integrate connectivity data with the restoration and biodiversity data to see how well restored meadows are functioning as parts of the broader coastal ecosystem.

 

Why Objective 6 is Crucial 

• Ecosystem services depend on biodiversity – not just plants, but the full community of animals and microbes that cycle nutrients, support fisheries, and stabilise sediments.

• Connectivity ensures resilience – if restored meadows are isolated, they may not support broad community dynamics; connected systems allow recolonisation, genetic exchange, and better recovery after disturbances.

• Linking science and restoration – by combining eDNA, genetics, and spatial analysis, we close the loop: we know what lives there, how populations relate across space, and how restoration can meaningfully reconnect the seascape.