Effect of ammonia stress on immune variables of Pacific white shrimp Penaeus vannamei under varying levels of pH and susceptibility to white spot syndrome virus.

Of late, Pacific white shrimp Penaeus vannamei culture has intensified globally and is a major contributor to the cultured shrimp produced worldwide. Intensification of its culture has led to elevated ammonia concentration during grow-out. Ammonia toxicity is a function of water pH, temperature, salinity and beyond the optimum range, creates stress to cultured aquatic species which can reduce growth, increase susceptibility to diseases and eventually mortality. The present study was aimed at quantifying the toxic effect of total ammonia nitrogen (TAN) (1, 3, 6 & 9 mg/l) and pH levels (6, 8 & 10) individually and in combination on median survival (50% lethal time) of shrimp (8 g) after exposure for 14 days followed by post-stress challenge with white spot syndrome virus (WSSV) for 9 days. Mortality risk factor and the toxicity effect on the immune variables were evaluated. Individual stressors showed a risk factor of 1-13 times, whereas combined treatments considerably increased the risk of dying compared to control. Low survival (15%) was observed in pH6TAN9 and pH10TAN3 treatments and was substantiated by prominent histological obliteration in gills of shrimp. The cumulative mortality in post-stress WSSV challenged trials was 1-5 times and 1-35 times in individual and combination treatments, respectively compared to control. The study revealed that variations in ammonia and pH beyond the optimal range significantly influence the non-specific immune mechanisms in P.vannamei and increases the susceptibility to WSSV especially in combination treatments.

Methodological approach for the collection and simultaneous estimation of greenhouse gases emission from aquaculture ponds.

Global warming/climate change is the greatest environmental threat of our time. Rapidly developing aquaculture sector is an anthropogenic activity, the contribution of which to global warming is little understood, and estimation of greenhouse gases (GHGs) emission from the aquaculture ponds is a key practice in predicting the impact of aquaculture on global warming. A comprehensive methodology was developed for sampling and simultaneous analysis of GHGs, carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) from the aquaculture ponds. The GHG fluxes were collected using cylindrical acrylic chamber, air pump, and tedlar bags. A cylindrical acrylic floating chamber was fabricated to collect the GHGs emanating from the surface of aquaculture ponds. The sampling methodology was standardized and in-house method validation was established by achieving linearity, accuracy, precision, and specificity. GHGs flux was found to be stable at 10 ± 2 °C of storage for 3 days. The developed methodology was used to quantify GHGs in the Pacific white shrimp Penaeus vannamei and black tiger shrimp Penaeus monodon culture ponds for a period of 4 months. The rate of emission of carbon dioxide was found to be much greater when compared to other two GHGs. Average GHGs emission in gha-1 day-1 during the culture was comparatively high in P.vannamei culture ponds.