Diet rather than temperature determines the biochemical composition of the ragworm Hediste diversicolor (OF Muller, 1776) (Annelida: Nereidae)

ABS T R A C T The polychaete Hediste diversicolor is known to recycle side streams from aquaculture and biogas production. We conducted a feeding experiment to evaluate whether rearing temperature or mixtures of these two side streams enhances biomass production and fatty acid composition. We reared H. diversicolor along a 5-temperature gradient ranging from 5.8 degrees C to 17.1 degrees C and a 4-step gradient form 100% aquaculture sludge to 100% solid biogas digestate. Formulated fish feed served as a control diet. Polychaetes increased growth rate with increasing temperature, ranging from 0.01 at 5.8 degrees C to 0.14 at 17.1 degrees C, while survival was inversely affected by temperature with 100% survival at 5.8 degrees C and 70% survival at 17.1 degrees C. Diet had a less pronounced effect on polychaete survival, and no significant effect on growth rates. Contrasting to growth, the fatty acid composition of the polychaetes was not affected by temperature but was highly influenced by diet, as polychaetes did not cluster by rearing temperature but by the diets they received. In conclusion, H. diversicolor can be utilized as a recycler of aquaculture and biogas side streams, and production temperature can be optimized for growth without compromising fatty acid composition and quality of the polychaetes.

Automated summary

This study evaluated the effects of rearing temperature and mixtures of aquaculture and biogas side streams on the biomass production and fatty acid composition of the polychaete Hediste diversicolor. The results showed that temperature significantly affected the biomass production, with higher temperatures promoting higher growth rates but lower survival rates. The diet had a significant effect on the fatty acid composition of the polychaetes. Therefore, optimizing the production temperature can enhance the growth of H. diversicolor without compromising the fatty acid composition and quality.