Environmental drivers and ecological responses of seaweed litter production and decomposition: A comprehensive review

Seaweed beds are essential components of coastal ecosystems, playing a pivotal role in global carbon cycling and marine nutrient dynamics. The production and decomposition of seaweed litter directly influence sediment nutrient supply, benthic community structure, and ecosystem stability. This review synthesizes current research on seaweed litter production, deposition, and decomposition, with a focus on natural drivers (e.g., temperature, light, seasonal variations, hydrodynamics, and biotic interactions) and anthropogenic factors (e.g., seaweed aquaculture, marine pollution, overfishing, and coastal development) affecting litter accumulation and breakdown rates. Climate change is expected to accelerate seaweed growth and litterfall but may also alter microbial and benthic communities, thereby influencing decomposition processes. Additionally, the chemical composition of different seaweed species (e.g., C/N ratio, lignin content, and secondary metabolites) significantly affects decomposition rates. Future studies should prioritize the interactions of multiple environmental factors, long-term spatiotemporal monitoring, the impacts of extreme climatic events, and the prolonged effects of human activities, while integrating ecosystem modeling to predict future trends. The role of microbial communities and their enzymatic activities in seaweed decomposition also warrants further investigation. To enhance the sustainable management of macroalgal ecosystems, an ecosystem-based management approach should be adopted, alongside efforts to explore the resource utilization of seaweed litter, including applications in biofuel production, organic fertilizers, and bioactive compound extraction. This review provides a scientific foundation for understanding the ecological function of seaweed litter and offers insights into marine carbon sequestration, fisheries management, and coastal ecosystem conservation in the context of global change.