Microbial Communities in Peruvian Seabird Guano and Their Potential for Sustainable Agriculture Revealed by Metabarcoding

Seabird guano from the Peruvian coast constitutes a concentrated reservoir of nutrients and microbial biomass, with historically recognized importance in global agricultural fertilization (Cushman, 2023). However, its microbial diversity and functional potential have been poorly characterized. This study presents the first comprehensive analysis of bacterial and fungal communities in the guano of Phalacrocorax bougainvillii (guanay cormorant) and Sula variegata (Peruvian booby) using 16S rRNA and ITS metabarcoding. A total of 260 georeferenced samples were collected from eight islands and two guano points along the Peruvian coast, grouped into 13 composite samples. DNA was extracted using the E.Z.N.A.® Soil DNA kit, and sequencing was performed on an Illumina MiSeq platform (V3–V4 for bacteria and ITS for fungi). Bacterial communities were dominated by Bacillota, particularly Bacillales, with genera such as Paeniclostridium and Lentibacillus, associated with saline environments and possessing potential for biological nitrogen fixation, as well as plant growth-promoting functions. Alpha and beta diversity were similar across species and islands. Fungal communities were more diverse in booby guano, dominated by Ascomycota (Eurotiales, Aspergillaceae), with greater phylogenetic differentiation and unique ASVs, reflecting sensitivity to local microconditions. Redundancy analysis indicated that pH and electrical conductivity structure the bacterial
community. Predicted functional profiles revealed metabolic stability, consistent with functional resilience. Overall, guano acts as a chemically filtered microecosystem that promotes nutrient mineralization and biogeochemical dynamics, highlighting its potential as a natural fertilizer and strategic resource for sustainable soil management.