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.

In Vitro screening of ammonia and nitrite-degrading bacteria isolated from broiler chicken (Gallus gallus domesticus) intestines and pond sediment of nile tilapia (Oreochromis niloticus): A preliminary study

The high level of ammonia and nitrite is a toxic factor for both poultry and aquaculture animals that directly lead to lower economic benefits. Thus, reducing ammonia and nitrite levels is an essential key for successful culture and is also important to reduce the amount of ammonia and nitrite released into the environment. This study aimed to screen bacteria having a capacity to degrade either ammonia or nitrite in vitro. Five bacterial strains previously isolated from broiler chicken (Gallus gallus domesticus) intestine and pond sediment of Nile Nilapia (Oreochromis niloticus) were used in this study, namely IBP-1, IBP-2, IBP-3, IBP-4, and IBP-5 strains. The screenings were performed using either NH4Cl containing medium or NaNO2 containing medium to determine the ability of bacteria to reduce ammonia or nitrite respectively. The ammonia and nitrite levels were afterwards measured at the beginning (day 0: before bacterial inoculation), 24h (day 1), 48h (day 2), and 72h (day 3) after the addition of 1 ml of the bacterial suspension. The results showed that the five bacterial isolates were able to degrade the ammonia and nitrite content. The greatest reduction of ammonia was achieved by IBP-4 strain (0.00 mg/l), followed by IBP-5 strain (0.04 mg/l), IBP-1 strain (0.05 mg/l), IBP-3 strain (0.14 mg/l) and IBP-2 strain (0.19 mg/l). IBP-1 and IBP-2 strains showed the highest reduction of nitrite levels with values of 0.01 mg/l and 0.02 mg/l after 72h of bacterial inoculation. These results suggest that the five bacterial strains are potentially used for degrading toxic ammonia and nitrite.

ANTIBIOTIC-RE¬¬SISTANT MOTILE AEROMONADS ASSOCIATED WITH CULTURED INDIAN MAJOR CARPS, POND WATER AND POND SEDIMENT

The uproar in antimicrobial resistance (AMR) among the aquacultured environment has led to the isolation of multiple antibiotic-resistant (MAR) Aeromonas strains. The current study aimed at the enumeration of antibiotic-resistant Aeromonas in carps of aquacultured environment and market samples. Isolation of Aeromonas was also done in Rimler-Shotts agar supplemented with novobiocin followed by antibiotic-sensitivity assay against 12 broad-spectrum antibiotics. Five oxytetracycline-resistant strains were examined for the presence of three tetracycline-resistant genes (tetA, tetC and tetE). The presumptive Aeromonas counts on starch-ampicillin agar were determined as log 3.00-log 6.45/g in carps, log 3.00l-log 5.06/ml in pond water and log 3.30–log 5.14/g in pond sediment. Higher proportions of motile aeromonads from market carps were resistant to chloramphenicol, cefalexin, gentamycin, oxytetracycline and trimethoprim than the farmed carps. Aeromonas strains depicted 57 resistant profiles. About 88.43% of the Aeromonas strains were of the MAR group among which 12.15% and 4.67% were resistant to ≥6 and ≥7 antibiotic groups, respectively. Selected oxytetracycline-resistant strains were negative for targeted genes. The current study implied the high prevalence of AMR bacteria in cultured carps in West Bengal, India. Furthermore, the study indicated that motile aeromonads comprise an effective marker for monitoring AMR in freshwater aquatic environments.