Nutrient assimilation from puffer and tilapia aquaculture sludge by marine polychaete Neanthes acuminata (Ehlers, 1868): a way forward to solid waste management

Despite its contribution to food security, managing solid waste from land-based aquaculture has been a major problem worldwide. Various bioremediation approaches have long been used to manage solid waste. Hence, a holistic and self-driven system is lacking. As a practical alternative, aquaculture sludge can provide habitats and nutrition, thereby increasing biomass production for deposit-feeding polychaetes. As nutrient uptake abilities and reproductive strategies can vary among species, we examined the survival, growth, and nutrient uptake efficiency of Neanthes acuminata from sludge types collected separately from two recirculating aquaculture systems: puffer (i.e., Takifugu rubripes) and tilapia (i.e., Oreochromis niloticus). A higher survival rate (i.e., 80-90%) was achieved in the sludge treatments compared with the negative control over an eight-week period. The growth rate increased in both sludge treatments across the experimental weeks, suggesting their ability to utilize nutrients in metabolic processes. Carbon and nitrogen uptake were evident, with a higher nitrogen percentage. The enrichment of nitrogen stable isotope ratios within polychaete body tissue in puffer sludge exposure further supports the upcycling rate. The carbon-to-nitrogen ratio of fecal materials of N. acuminata after 10-day exposure was significantly higher than the initial sludge, indicating the supply of carbon-enriched materials within the sludge substrate. This study confirms the survival, growth, and nutrient-upcycling efficiency of a newly introduced polychaete species that utilizes solid waste materials and recommends it as an efficient species for aquaculture solid waste management.