Integrative biomarker approach to decode seasonal variation in biomarker responses of Scylla serrata and Penaeus monodon from Sundarbans estuarine system

Sundarbans Estuarine System is a highly productive estuary and is considered the most important spawning and nursery ground for various commercial fish and shellfish species. Estuarine organisms are frequently exposed to a wide variety of pollutants due to their vicinity to human habitation. Marine organisms residing in this area are also exposed to extensive fluctuations of environmental factors which vary with season. In the present study, effects of seasonal variation on oxidative stress biomarkers such as superoxide dismutase, catalase, glutathione-S-transferase, and lipid peroxidation in the hepatopancreas of mud crab Scylla serrata and shrimp Penaeus monodon, were studied during monsoon, winter, spring and summer seasons. The integrated biomarker response (IBR) was assessed with the biomarker scores for all four seasons in both species. Our results suggested seasonal discrepancies as the governing factor behind biomarkers’ variability. The breeding period of the animals also seems to play a significant role in their oxidative stress physiology. The IBR results indicated that moderately high temperatures and low salinity in the monsoon season are the most stressful for crabs. This stress might also be ascribed to the breeding period of these crabs which exacerbates the stress level during this season. However, in the case of shrimps, the highest IBR value was observed in the winter season due to impaired ROS elimination at low temperatures. This study also offers baseline values in various seasons that would be beneficial to be considered in environmental monitoring programs to avoid the misinterpretation of environmental factors, which change seasonally.