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Abstract

Seagrass meadows provide essential coastal ecosystem functions by stabilizing sediments, enhancing water quality, and shaping nutrient and microbial dynamics. With global seagrass losses accelerating due to climate change and anthropogenic pressures, artificial seagrass (ASG) has been proposed as a nature-based alternative to mimic these functions. However, its ability to replicate biological interactions, particularly microbial regulation and pathogen suppression, remains unclear. In this study, we conducted a six-week mesocosm experiment comparing natural Thalassia hemprichii and ASG within coral reef-associated habitats in southern Taiwan. Physicochemical parameters, sedimentation rates, nutrient concentrations, and planktonic and benthic bacterial communities were analyzed. Sedimentation rates and nutrient levels did not show statistically detectable differences between natural and artificial seagrass treatments, suggesting comparable physical conditions under the experimental scale and replication. Community-level analyses showed that within the planktonic communities, ASG and natural seagrass systems differed significantly, whereas benthic communities did not exhibit statistically detectable treatment effects. Nonetheless, taxon-specific patterns revealed important functional divergences. Natural seagrass mesocosms were associated with higher relative abundance of bacterial taxa commonly link to nutrient cycling and nitrogen transformation, including members of the Alphaproteobacteria. In contrast, ASG mesocosms showed higher relative abundances of potentially pathogenic or opportunistic taxa such as Vibrio spp. and filamentous cyanobacteria (Phormidium). Overall, while ASG reproduced key aspects of the physical habitat structure, the microbial community patterns observed here suggest that artificial substrates may not fully capture the biologically mediated interactions characteristic of living seagrass systems. Within the limits of experimental duration and replication, our results indicate that ASG can approximate structural habitat functions but do not provide evidence of full functional equivalence to natural seagrass meadows. ASG may therefore contribute short-term structural habitat complexity, whereas the broader ecological functions associated with intact seagrass ecosystems likely depend on plant-driven biological interactions that were only partially represented under the present experimental conditions

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