Consequential study on different levels of C/N ratios used in biofloc-based aquaculture system

Biofloc technology is much highlighted these days because of its tremendous effects on aquaculture. Microbes were enriched on cheapest organic carbon source i. e., powdered banana peels and were incorporated in different aquaria rearing grass carp fingerlings under different C/N treatments (10:1, 15:1 and 20:1) and 10% water daily water exchange. The initial growth of fingerlings was recorded. The experiment was settled in triplicates for 60 days and run parallel to control group provided with commercial feed and daily water exchange. Its effect was evaluated by measuring the growth of fingerlings and water parameters of each aquarium. The average % gain in weight and length of fingerlings was obtained significantly highest (28.12 ± 0.30g and 17.29 ± 0.46cm respectively) in aquaria containing pure powdered banana peels with 10% water exchange and C/N ratio was adjusted at 20: 1 (T3) than other treatments and control. Ammonia and other water parameters were also under control in T3 than other experimental and control groups. By all counts, it was concluded that the highest C/N ratio in biofloc system had the potential to increment C. idella growth rate by reducing toxicity and could be used as fish meal substitute.

A Solution for Sustainable Utilization of Aquaculture Waste: A Comprehensive Review of Biofloc Technology and Aquamimicry

Biofloc technology (BFT) is gaining traction as a strategic aquaculture tool for boosting feed conversions, biosecurity, and wastewater recycling. The significant aspect of BFT is aquaculture with highest stocking density and minimal water exchange. It not only improves the water quality of a system by removing inorganic nitrogen from wastewater but also serves as a suitable feed supplement and probiotic source for cultured species. This technology is commonly used for shrimp and tilapia culture and can be used for both semi-intensive and intensive culture systems. Biofloc, when combined with formulated diets, forms a balanced food chain that improves growth performance. Nutrients in this system are continuously recycled and reused and form an efficient alternative system in aquaculture. In addition to the reduction in water exchange, it is also considered as a bio-security measure, since it prevents entry of disease from outside sources. Aquamimicry is an innovative concept that simulates natural estuarine conditions by developing copepods that act as supplementary nutrition especially for shrimp culture. The review highlights the process, significance, and development of BFT, its microbial interactions, nutritional value, transition from biofloc to copefloc, and concept of aquamimicry to sustainably improve aquaculture production.

Damming Weakens the Groundwater and Surface Water Exchange and Its Nitrate Removal in Semi-arid Prairie Rivers

Surface water (SW)-Groundwater (GW) exchange plays a vital role in a prairie aquatic system and the biogeochemical cycling in such a system. Considering the inadequate understanding of damming on SW-GW exchange, a damming prairie river in Southeast Eurasian steppe was chosen to investigate variations of the SW-GW exchange and its influences on the fate of nitrate (NO3-). Both hydraulic and hydrochemical methods were applied to precisely depict the daily and seasonal exchange processes. The upstream and downstream reaches of the dam were observed to be upwelling and downwelling conditions respectively within a hydrologic year. Results obtained from multiple tracer methods and hydraulic method indicate that damming contributed to transfer the stream from the upwelling to the downwelling condition and weaken the SW-GW exchange in the downstream. The patterns of SW-GW exchange modulated the NO3- uptake or production between the SW and the GW. NO3- was mainly removed in the SW-GW exchange zone (SW-GW EZ) of the upwelling segment, while produced in the downwelling segment. Both the removal and production of NO3- were enhanced during snowmelt period, which might be an active period for the SW-GW exchange and NO3- fate. This study underscores the negative effect of damming on the SW-GW exchange and accompanied NO3- removal in prairie river systems.

The First Line of Defense: Receptor-like Protein Kinase-Mediated Stomatal Immunity

Stomata regulate gas and water exchange between the plant and external atmosphere, which are vital for photosynthesis and transpiration. Stomata are also the natural entrance for pathogens invading into the apoplast. Therefore, stomata play an important role in plants against pathogens. The pattern recognition receptors (PRRs) locate in guard cells to perceive pathogen/microbe-associated molecular patterns (PAMPs) and trigger a series of plant innate immune responses, including rapid closure of stomata to limit bacterial invasion, which is termed stomatal immunity. Many PRRs involved in stomatal immunity are plasma membrane-located receptor-like protein kinases (RLKs). This review focuses on the current research progress of RLK-mediated signaling pathways involved in stomatal immunity, and discusses questions that need to be addressed in future research.

Response of Water Environment to Land Reclamation in Jiaozhou Bay, China Over the Last 150 Years

Jiaozhou Bay (JZB), located at Qingdao City, north China, is a semi-enclosed shallow bay that has undergone large-scale land reclamation and is suffering from a deteriorated water environment. Long-term evolution of JZB with respect of coastline, tidal prism, tidal dynamics, water-exchange capacity, and pollutant transport from 1863 to 2020 was investigated in this paper, using remote sensing images, historical charts, and a numerical model. The JZB was predominated by natural evolution from 1863 to 1935, during which the coastline barely changed. Thereafter, human intervention became intense and more and more natural tidal flats were replaced by salt ponds, aquaculture area, and reclamation very quickly. As a result, tidal prism, area of tidal flats, and area of JZB decreased sharply by 0.290 km3, 182 km2, and 223 km2, respectively, from 1935 to 2020, corresponding to annual decreasing rates being of 123 times, 10 times, 12 times, respectively, as that of before 1935. A numerical model showed that the residual current in JZB tended to be weaker due to the change of coastline and bathymetry, which is not favoring the water-exchange and pollutant transport, especially in the northeast of JZB. The basin residence time increased from 15.5 days in 1935 to 17.6 days in 2020, because of weaker residual tidal current and smaller tidal prism. Local residence time increased significantly near the area with large land reclamation, especially in the northeast and west of JZB. Distribution of dissolved inorganic nitrogen (DIN), in each year, which is the dominant pollutant in JZB, indicated higher DIN concentration and weaker transport along with reclamation. The research on JZB evolution over the last 150 years can provide useful suggestions for the decision-makers of the local government to improve the marine ecosystem. The systematic method to investigate long-term water environment evolution of JZB can be used to study other semi-closed bays.

Chemical composition of groundwater in the zone of slow water exchange of the Upper Pontian aquifer, Northwestern Bulgaria

The Upper Pontian aquifer occupies the central part of the Lom Depression. The geological position determines its gradual dipping from the periphery to the central parts. It is one of the most water-abundant aquifers in Northwestern Bulgaria and is associated with the sands of the Archar Formation. The chemical composition of the waters is of interest and is important for the water supply in the area. The analysis of the data shows that there are regularities in the change of the water quality with aquifer depth. Significant differences in some of the hydrochemical parameters are found in the zone of slow water exchange and geological and hydrogeological explanations have been sought.

Water Exchange Between the Gulf of Ob and the Kara Sea During Ice-Free Seasons: The Roles of River Discharge and Wind Forcing

The Gulf of Ob is among the largest estuaries in the World Ocean in terms of area, watershed basin, and freshwater discharge. In this work, we describe the roles of river discharge and wind forcing on the water exchange between the Gulf of Ob and the Kara Sea during ice-free seasons. This work is based on the extensive in situ measurements performed during 10 oceanographic surveys in 2007–2019. Due to large river runoff (∼530 km3 annually) and low tidal forcing (<0.5 m/s), the estuarine processes in the Gulf of Ob during the ice-free season are generally governed by gravitational circulation. Local wind forcing significantly affects general estuarine circulation and mixing only in rare cases of strong winds (∼10 m/s). On the other hand, remote wind forcing over the central part of the Kara Sea regularly intensifies estuarine—sea water exchange. Eastern winds in the central part of the Kara Sea induce upwelling in the area adjacent to the Gulf of Ob, which increases the barotropic pressure gradient between the gulf and the open sea. As a result, intense and distant (120–170 km) inflows of saline water to the gulf occur as compared to the average conditions (50–70 km). Remote wind forcing has a far stronger impact on saltwater intrusion into the Gulf of Ob than the highly variable river discharge rate. In particular, saltwater reaches the shallow central part of the gulf only during upwelling-induced intense inflows. In the other periods (even under low discharge conditions), fresh river water occupies this area from surface to bottom. The upwelling-induced intense inflows occur on average during a quarter of days (July to October) when the gulf is free of ice. They substantially increase the productivity of phytoplankton communities in the gulf and modify the taxa ratio toward the increase of brackish water species and the decrease of freshwater species.