Enhancing soil and plant biodiversity via marine waste-derived organic amendments

In Mediterranean climates, soils are degraded by anthropogenic activities that deplete organic matter, reduce biodiversity and impair ecosystem functioning. Ecological restoration through organic amendments may counteract these trends and recover degraded soils, preventing the loss of ecosystem services. Indeed, organic amendments improve soil chemico-physical properties and microbial biodiversity, promote natural revegetation and accelerate community successions. In this context, and aligned with circular economy principles, the preliminary results on the effects of a novel lumbricompost (derived from Posidonia oceanica litter + fish market residues) compared to traditional sewage sludge, applied with or without zeolites from limestone quarry waste, are reported. The study, part of the EMBRACE project (PRIN PNRR 2022), aims to assess the potential of these organic and inorganic matrices in improving industrial soil functioning. To this end, a field experiment was conducted on a quarry substrate with 5 treatments, each replicated in three plots: lumbricompost, sewage sludge, their respective zeolite-enriched variants, and an untreated control. After three months from the amendments, soils were characterized for several chemico-physical (water content, organic matter, pH, electrical conductivity and water-holding capacity) and biological properties (seed germination, natural revegetation, community-level physiological profiling as well as enzymatic activities targeting major nutrient cycles, such as hydrolase, β-glucosidase, β-1,4-N-acetylglucosaminidase, phosphatase and arylsulfatase). Results obtained so far (spring sampling) showed functional shifts in soil microbial community across treatments, with compost-enriched soils generally exhibiting enhanced biodiversity and metabolic activity. In particular, hydrolase and β-glucosidase activities significantly increased, indicating improved soil biochemical functioning because of the amendments. Organic matter addition promoted revegetation in treated as compared to untreated soils, leading to structural and functional changes in plant diversity depending on the amendment applied. In addition, treatments did not elicit phytotoxic effects. Seasonal monitoring will further clarify the effectiveness of these sustainable strategies for restoring soils under climatic and anthropogenic pressures.