A Study on Phytochemical and Nutrient Profile of Six Inedible Seaweed Species Found on the Coasts of Tanzania

Abstract

Coastal accumulation of inedible seaweeds generates substantial biomass that remains largely underutilized despite its agronomic potential. This study characterized six inedible seaweed species (Sargassum spp., Ulva spp., Enteromorpha spp., Hypnea spp., Padina spp., and Laurencia spp.) collected from the Tanzanian coastline to evaluate their suitability as inputs for organic fertilizer production. Samples were analyzed for pH, electrical conductivity, organic carbon, ash content, macro- and micronutrients, and phytohormones. Ulva spp. exhibited the highest organic carbon (24.1%), indole-3-acetic acid (6.29 ± 0.53 mg/kg), and naphthaleneacetic acid (7 ± 0.50 mg/kg). Sargassum spp. exhibited the highest potassium (78,667 mg/kg), gibberellic acid (14.78 ± 0.70 mg/kg), and kinetin (20.82 ± 6.12 mg/kg) levels, indicating its potential value in promoting shoot growth. Padina spp. were richest in calcium (218,567 mg/kg) and magnesium (17,350 mg/kg). Enteromorpha spp. showed substantial organic carbon (22.53%) and high calcium (190,967 mg/kg). Hypnea spp. had the highest phosphorus content (1697 mg/kg) and exceptionally high sodium contents (52,933 mg/kg), while Laurencia spp. had higher iron contents (5373 mg/kg) and alkaline pH (7.88). These findings confirm that underutilized coastal seaweeds are valuable sources of nutrients and plant hormones and can be converted into organic fertilizers to restore soil fertility and support sustainable agriculture.