Abstract
Introduction
Massive seasonal accumulations of holopelagic
Sargassum
have affected Caribbean coastal ecosystems and communities, therefore the need for sustainable valorization strategies are paramount to transform this biomass into value-added products. This study evaluated stranded holopelagic
Sargassum
as a co-feedstock for vermicomposting.
Methods
Beach wrecked
Sargassum
was used in the vermicomposting system using
Eisenia fetida
(red wrigglers) and mixed in a ratio of 1:1 with
Sargassum
: cow manure (fresh weight), with three independent vermicomposting containers per treatment. After a 90-day period, measurements of final abundance and reproductive performance, vermicast composition and sanitary quality, culturable putative plant growth-promoting microorganisms colony forming units, and bacterial and fungal community profiles were assessed. The vermicast was subsequently evaluated in tomato and sweet pepper greenhouse experiments using 25 plants per treatment.
Results and discussion
After the 90-day experimental period, the total worm population reached 310 worms in the cow manure-only system (SVC1) and 575 worms in the cow manure +
Sargassum
system (SVC2), corresponding to net increases of 210% and 475%, respectively, relative to the initial stocking density of 100 worms, with significantly higher adult biomass, cocoon production, and juvenile abundance in SVC2 (
p
Escherichia coli
and
Salmonella
spp. were not detected, and total coliforms were recorded at 1.0 × 10
2
CFU g
−1
. SVC2 showed higher culturable counts of putative
Azotobacter
and phosphate-solubilizing microorganisms, while SVC1 had higher putative
Pseudomonas
counts. SVC1 had higher observed relative abundances of genera such as
Lacunisphaera
and
Haliscomenobacter
, while SVC2 had higher relative abundances of
Luteolibacter, Simiduia, Cellvibrio,
and
Ilumatobacter
, and had a shared core microbiome comprising
Luteolibacter, Cellvibrio, Algoriphagus, Verrucosispora,
and
Hydrogenophaga.
Although the bacterial and fungal communities showed visual separation in the ordination analyses, PERMANOVA did not detect statistically significant differences between treatments (
p
= 0.10). Vermicast application significantly enhanced fruit yield, with SVC2-100 increasing mean cumulative tomato yield from 2.6 to 7.5 kg plant
−1
and SVC2-200 increasing sweet pepper yield from 1.3 to 4.0 kg plant
−1
over the production period, corresponding to increases of 185.5% and 203.0%, respectively, in comparison to the Control. The study demonstrated the potential of pelagic
Sargassum
biomass as a co-feedstock for vermicomposting and as a circular bioeconomy approach for producing agricultural amendments. However, field validation, long-term soil and crop safety assessments, and extension and farmer training are required before wider agricultural adoption.