Comparative Assessment of the Bioremediation Potential of Polychaetes (Lug worm-Arenicola marina sp and Syllidae Worm-Syllis prolifera sp) in Aquaculture Pond Sediment

Polychaetes play an important role in nutrient cycling and remediation of coastal ecosystems. Large quantities of organic matter that could lead to pollution of pond and coastal waters are generated by aquaculture waste. To assess the remediation prospects of Arenicola marina and Syllis prolifera species, laboratory sediment microcosm experiments were conducted where large size Arenicola marina and Syllis prolifera were introduced to sediment in microcosm A, large size Arenicola marina to sediment in microcosm B, large sized Syllis prolifera to sediment in microcosm C and no polychaetes to sediment in microcosm D. Microcosm A′, B′ and C′ as replicates for small size polychaetes were also set up, respectively. After 30 days, microcosm A, B and C had significant decrease in organic carbon levels with microcosm B being the highest (Total organic carbon (TOC); 27.87%; p< 0.05). Both large and small polychaetes promoted significant decrease in sulphur (S) content (mean=62.76±0.21; 62.81±0.21%) and iron(Fe) (mean=49.43±1.47; 36.28±5.90%) respectively. Increase in pH by 31.15±0.13% was found in the presence of large size polychaetes, most likely associated with the burrowing process involving oxidation of Fe to Fe2O3. Large size polychaetes had better survival (mean=92±0.82%) than their small size counterpart (mean=55±4.08%). The extent of biodegradation B>A>C>D observed revealed that large size Arenicola marina was a better bioremediator of organic matter (OM), Fe and S enriched aquaculture pond sediment, probably due to its biological characteristics, well suited for the aquaculture than other species of sea worms that produce free swimming larvae. Therefore, large size Arenicola marina significantly improved sediment quality as well as increased its pH without compromising their survival. As the search for a better bioremediator of organically enriched sediment continues, our result revealed large size Arenicola marina as a more promising candidate compared to other species documented elsewhere in the world. Hence, rearing of large size Arenicola marina sp is recommended as their feeding habits are well suited for aquaculture.