Limited Water Exchange Research Articles

Impact of Biochar Addition on Biofloc Nitrifying Bacteria and Inorganic Nitrogen Dynamics in an Intensive Aquaculture System of Shrimp.

In this study, an eight-week culture trial of Penaeus vannamei juveniles was conducted in commercial intensive systems to compare the impacts of biochar and molasses addition on biofloc nitrifying bacteria and inorganic nitrogen dynamics under limited water exchange conditions. During the trial, the biofloc concentration (in terms of VSS and TSS), quantities of total bacteria (TB) and total Vibrio (TV), and ratio of TV/TB in the culture water were lower in the biochar group compared to the molasses group. Metagenomic sequencing analysis revealed that the bacterial community composition of bioflocs showed higher α-diversity and complexity in the biochar group compared to the molasses group. Moreover, the abundance of nitrifying bacterial genera and functional genes in bioflocs was higher in the biochar group compared to the molasses group. Inorganic nitrogen dynamics showed that NH4+-N and NO2--N were better controlled in the biochar group compared to the molasses group, as reflected by lower peaks of NH4+-N and NO2--N and higher NO3--N concentrations. Excellent production performance of shrimp was achieved, which in turn proved the reliable effect of biochar addition on the mediation of inorganic nitrogen transformation through nitrifying bacteria. These results showed that biochar addition could promote biofloc nitrifying bacteria and nitrification to more effectively control harmful nitrogen for shrimp efficient production. This study provides a practical example for the biochar application in biofloc-based systems for intensive aquaculture.

Depositional characteristics in the Lower Congo Basin during the Cenomanian-Turonian stage: Insights from fine-grained sedimentary rocks

The Cenomanian-Turonian (C-T) stage, marked by extensive black shales and Oceanic Anoxic Event 2 (OAE 2), is pivotal for deciphering paleoceanographic conditions and the main drivers of hydrocarbon formation. Despite its significant oil and gas potential, the Lower Congo Basin (LCB) in central West Africa, particularly during the C-T stage (Likouala Formation), has been severely understudied, primarily due to limited exploration and a historical preference for other basins. Therefore, understanding the depositional characteristics of the C-T stage in the LCB is essential for elucidating paleoceanographic conditions, evaluating hydrocarbon potential and interpreting environmental changes. Due to the limited availability of published data and samples, we employed a targeted and integrated geological analysis to gain comprehensive insights, encompassing logging, lithofacies identification, thin-section observations, grain size measurements, and geochemical analyses (major, trace, and rare earth elements), to provide a cohesive and confirmatory assessment. Utilizing relative sea-level curves and geochemical indicators, and by comparing with other relevant basins, this study preliminarily identified OAE 2 stratigraphic intervals and attempted to discuss the impact of OAE 2 on organic matter enrichment in the LCB. The results indicate that, during the C-T stage, the LCB featured a restricted sea bay environment with limited terrestrial input and anoxic waters. Multiple geochemical proxies suggest that relative sea-level changes significantly affected paleoproductivity, thereby influencing organic matter enrichment. During the depositional period of Lower Likouala Formation (LLF), a relative sea-level drop resulted in weakly reducing conditions in a marginal restricted sea bay environment, leading to low primary productivity. Conversely, during the depositional period of Upper Likouala Formation (ULF), enhanced aeolian input and sea-level rise increased nutrient supply from the open ocean. This led to elevated surface marine productivity and intensified reducing conditions in the water column, forming a marginal semi-restricted sea bay environment. Enhanced reducing conditions within the lower stratigraphic intervals of the ULF are likely consequences of OAE 2. However, the marginal restricted sea bay environment and limited water exchange may have constrained the enhancement of paleoproductivity by OAE 2. These insights not only significantly enhance our understanding of the organic-rich fine-grained sedimentary rocks in the LCB during the C-T stage, but also contribute to a broader comprehension of the South Atlantic's paleoceanographic conditions and the interplay between regional geological processes and global climate events during the C-T stage.

Nuʻupia Ponds’ Water Circulation Characteristics: Exploring Water Exchange and Residence Time for Marine Ecosystem Management

Nuʻupia Ponds, a traditional Hawaiian fishpond system, are located at Marine Corps Base Hawaiʻi (MCBH) and part of the Nuʻupia Ponds Wildlife Management Area, a wetland refuge for native, endangered, and protected birds and Hawaiian green sea turtles, as well as many native fish species. Currently, there is uncertainty regarding the ecological status and condition of the fishponds following prior modification of wetland habitats in and around the ponds. This study examines circulation dynamics and characterizes water exchange, pond volume, and residence time across the full tidal spectrum at the Nuʻupia fishponds. Our results indicate a general west to east gradient in current flow; with higher flushing rates and lower residence times of fishponds in the western ponds of the Nuʻupia system compared to the eastern ponds. We further found low flushing rates at several sites causing limited water exchange with Kāneʻohe Bay, as well as within the Nuʻupia Pond system. Sufficient water circulation plays a fundamental role in maintaining a healthy balance of fishpond flora and fauna and preserving ecosystem health. The results from this study provide a baseline for current physical water circulation dynamics and implications for ecosystem health, as well as informing science-based conservation and management strategies moving forward.

Development of desalination plants within the semi-enclosed Persian Gulf

Although many desalination plants have been built in the countries around the Persian Gulf (PG) over the past decade, there exist crucial water demands in this region. Considering the limited water exchange between PG and the open seas, effluents more than the natural capacity of the PG will increase the sea-water salinity continuously. This excess salinity, in addition to threatening the marine ecosystems, endangers the water supply for many population centers. This study provides a comprehensive numerical analysis of the impact of existing and new desalination plants on the PG’s salinity. In addition, the water residence time and pollutant extension have been investigated in the PG. There exist several concerns, especially in recent years about the probable threat of desalination growth in semi-enclosed seas such as PG. The effect of desalination plants on the mean salinity of PG is one the questions investigated in this research. Results demonstrate that the water residence times in the southern and northwestern regions are more than five years. This time is reduced to nearly 26 to 45 months in the eastern regions near the Strait of Hormuz. Generally, the desalination plants have a negligible effect on the salinity of PG in comparison with the climate conditions such as evaporation and water exchanges. Based on the results, a 50% increase in effluent discharge of existing desalination plants increases the average salinity of the PG by only 0.01 psu. However, the annual volume of net evaporation (that exits the clean water directly) is nearly 36 times more than the effluent discharge from the existing desalination plants. Furthermore, this value is almost 0.2% of the amount of water that enters the PG through the Strait of Hormuz. In spite of these findings, the regional effects can be significant in some parts of the PG. For example, the southern and western coasts of PG are generally more vulnerable to pollution than other areas. The main reason is the shallow water depth in these areas and the water recirculation pattern. Some sensitive local areas have been also addressed in this study. Among the studied regions, the coastlines at the northwest of PG and at the north the Qeshm Island are two susceptible areas. The findings of this study underscore the importance of considering a new integrated viewpoint in developing desalination plants within PG.

Temporal dynamics of microbial communities in the water of polyculture pond system for Chinese swimming crab Portunus trituberculatus

Microorganisms as the vital component of aquaculture ecosystems, were involved in nutrient cycling, water quality regulation, and the health of cultured species. In this study, aquatic water samples were collected monthly to reveal microbial community compositions, functions, and interactions in different habitats (pond and waterway) during the culture stages of the Chinese swimming crab Portunus trituberculatus in Shandong Province. Due to the semi-closed conditions with limited water exchange, the α diversities were lower in the polyculture pond. The relative abundances of the dominant phyla varied dramatically, and most biomarkers were identified in the polyculture pond. The β diversity of the microbial communities significantly differed among culture stages and habitats. Furthermore, the heterogeneity of prokaryotic microorganisms was greater than that of eukaryotic microorganisms. In the polyculture pond, the microbial community was sensitive to nutrient cycling, with abundant functions related to “photoautotrophy”, “nitrogen_respiration” and “nitrate_respiration”, corresponding to P. trituberculatus culture activities. The co-occurrence network of the microbial community in the polyculture pond tended to be looser than that in the waterway, with a lower number of taxa and correlations. In addition, these networks had nonrandom patterns and formed “small world” topological structures. The low-abundance genera with a higher level of betweenness centrality scores were the hubs or connectors in the networks and might play an essential role in microbial community composition. Furthermore, potential pathogens (Vibrio, Acholeplasma, Photobacterium, and Flavobacterium) deserve more attention during P. trituberculatus culture. This study will be useful for understanding microbial communities in polyculture pond systems and will provide a reference for the health aquaculture of P. trituberculatus.

Succession of phytoplankton communities from macro-scale to micro-scale in coastal waters of Qinhuangdao, China

The coastal area of Qinhuangdao, particularly the Changli Gold Coast Nature Reserve, is experiencing ecological degradation and frequent Harmful Algal Blooms (HABs). This study focuses on the changing phytoplankton communities in these coastal waters, examining them from both a macroscopic and microscopic perspective. Utilizing microscopy, molecular techniques, and pigment analysis, seasonal shifts were observed, with diatoms predominating in June and July, and dinoflagellates in August. Our morphological examination enabled the classification of 89 species into four distinct groups. The species Paralia sulcata and Pseudo-nitzschia pungens were most abundant in early summer, while Tripos furca, a dinoflagellate, dominated in August. This indicates a shift in phytoplankton communities due to environmental factors such as phosphate deficiency and high nitrogen/phosphorus ratios. Additionally, the study notes the impact of reduced river runoff and reintroduction of scallop farming contributing to nitrogen-rich eutrophication in August. Molecular analysis revealed a disparity between microscopic observations and the prevalence of Teleaulax blooms during early summer. Elevated concentrations of TN and DOC, coupled with limited water exchange, emerged as primary factors contributing to their occurrence. Sediment analysis revealed a high diversity but low abundance of dinoflagellates in August, with a significant presence of harmful species. The study highlights the shift from diatoms to harmful dinoflagellate populations, exacerbated by eutrophication and pollution, leading to HABs. These findings provide a theoretical basis for understanding toxic algal blooms and are crucial for environmental agencies in developing strategies to protect and sustainably develop offshore environments.

Variations and Interseasonal Changes in the Gut Microbial Communities of Seven Wild Fish Species in a Natural Lake with Limited Water Exchange during the Closed Fishing Season.

The gut microbiota of fish is crucial for their growth, development, nutrient uptake, physiological balance, and disease resistance. Yet our knowledge of these microbial communities in wild fish populations in their natural ecosystems is insufficient. This study systematically examined the gut microbial communities of seven wild fish species in Chaohu Lake, a fishing-restricted area with minimal water turnover, across four seasons. We found significant variations in gut microbial community structures among species. Additionally, we observed significant seasonal and regional variations in the gut microbial communities. The Chaohu Lake fish gut microbial communities were predominantly composed of the phyla Firmicutes, Proteobacteria(Gamma), Proteobacteria(Alpha), Actinobacteriota, and Cyanobacteria. At the genus level, Aeromonas, Cetobacterium, Clostridium sensu stricto 1, Romboutsia, and Pseudomonas emerged as the most prevalent. A co-occurrence network analysis revealed that C. auratus, C. carpio, and C. brachygnathus possessed more complex and robust gut microbial networks than H. molitrix, C. alburnus, C. ectenes taihuensis, and A. nobilis. Certain microbial groups, such as Clostridium sensu stricto 1, Romboutsia, and Pseudomonas, were both dominant and keystone in the fish gut microbial network. Our study offers a new approach for studying the wild fish gut microbiota in natural, controlled environments. It offers an in-depth understanding of gut microbial communities in wild fish living in stable, limited water exchange natural environments.

Circulation and Stratification Changes in a Hypersaline Estuary Due to Mean Sea Level Rise

Hypersaline Hamelin Pool, with mean salinity >65, is located in Shark Bay, Western Australia. The high salinity has reduced its biodiversity, but it is home to a diverse assemblage of modern marine stromatolites. The limited exchange of water between Hamelin Pool and the rest of Shark Bay, due to the presence of the shallow Faure Sill together with high evaporation and low rainfall-runoff have resulted in a hypersaline environment. With climate-change-induced mean sea level rise (MSLR), hydrodynamic processes that maintain the hypersaline environment may be affected and are the focus of this paper. Oceanographic observations, together with hydrodynamic model results, were used to examine the hydrodynamic processes under present and future MSLR scenarios. A large attenuation in the tidal range, changes in the tidal characteristics, and current speeds together with a strong salinity gradient were observed across the Faure Sill under present-day conditions. Under an MSLR scenario of 1 m, the tidal amplitude decreased by up to 10% to the north, whilst to the south, the tidal range increased by up to 15%. Regions of strong vertical stratification were present on both sides of the Faure Sill. The simulations indicated that, under MSLR scenarios, these regions expanded in area and exhibited higher levels of vertical stratification. The salt flux across the Faure Sill was maintained as a diffusive process under MSLR scenarios.

The Geotectonic Peculiarities of the North Caspian Permian Salt-Bearing Basins (Kazakhstan)

This article examines the geotectonic and sedimentary features of the Upper Devonian–Carboniferous–Permian deposits of the North Caspian basin, represented by deposits of marine Paleozoic-isolated carbonate platforms formed during the subsidence of the basement on the passive continental margin. The top is covered by thick salt-bearing Kungurian deposits from the end of the Early Permian epoch. The formation of carbonate platforms is associated with a major tectonic restructuring of the basin at the turn of the Caledonian and Hercynian eras, when the Paleo-Tethys Ocean was formed and isolated carbonate islands began to grow in an open marine environment. The central part of the depression experienced a long and gradual subsidence that spanned the entire Paleozoic era and the beginning of the Mesozoic era. In the south and east, from the Devonian to the Permian periods, barriers were formed in the form of island carbonate massifs that separated the North Caspian basin from the Paleo-Tethys Ocean. During the formation of the salt-bearing basin, these barriers limited water exchange and ensured a one-way influx of sea water from the open ocean. As a result, at the end of the Permian period, thicker salts accumulated; however, during the collision of the continental massifs, an invasion of many kilometers of redbeds occurred. They initially stopped salt accumulation; however, gradually, in the north of the Caspian Sea during Roadian times, the salt accumulation continued. The post-Roadian time is associated with the influx of large quantities of redbed sediments, which caused gravitational instability in the underlying salt, and salt tectonics began with the formation of domal structures.

A system of environmentally important decision-making for the sustainable use of marine estuaries in the conditions of anthropogenic and climatic changes

Sustainable use of marine water areas is one of the priorities of preserving biodiversity and the environment as a whole. The problem of a clear plan of rehabilitation measures, which would be based on complex and balanced solutions arises for their effective restoration and further functioning. These decisions should take both environmental and economic aspects into account. Estuaries, unlike marine water areas, are more sensitive to anthropogenic and climatic changes. They are characterized by shallow water level, functioning in the conditions of limited water exchange, dependence on river flow and greater anthropogenic load compared to marine water areas. These features are the cause of more intensive changes in the structure of biocenoses, rise in emergency situations, loss of productivity and sustainability of ecosystems as a whole. Thus, there is a need to introduce environmental management for these reservoirs, which should be based on a multi-component decision support system. This system will make it possible to develop clear plans for the restoration of marine ecosystems and prevent negative changes and degradation in them. The proposed scheme for developing plans for the restoration of the ecosystems of estuaries is represented by three blocks. The first “Block of data collection” involves the implementation of 3 stages: assessment of the current state of the reservoir; definition of problems and their ranking; assessment of ecosystem services. The second block “Search for a solution” is based on 4 components: Component 1. Database management system; Component 2. Geoinformational system; Component 3. Mathematical and predictive models; Component 4. Informational and management system for choosing strategic and operational decisions. The third block “Implementation of measures” involves the implementation of 4 stages: environmental assessment of decisions and projects, implementation of environmental measures, evaluation of effectiveness, search for new solutions and their improvement. The proposed scheme will enable a comprehensive approach to the restoration of estuarine ecosystems and ensure their sustainable use.

Transfer of 129I to freshwater fish species within Fukushima and Chernobyl exclusion zones

Unique data is reported on the transfer of 129I iodine from freshwaters to fish as well as the internal distribution within fish from the Fukushima and Chernobyl exclusion zones (ChEZ). Samples of water, sediments and fish were collected in the contaminated ponds Inkyozaka and Suzuuchi, and in the less contaminated Abukuma river in Fukushima, as well as in the contaminated Glubokoye lake and in the less contaminated Starukha lake in ChEZ. In water, 129I was mainly present as low molecular mass (LMM) and negatively charged species, while a minor fraction was associated with colloidal fraction, most probably organic material in water. The sediment-water 129I apparent distribution coefficients, Kd, ranged from 225 to 329 L/kg, equal that of stable iodine, but did not correlate with 129I/127I ratio or 129I/137Cs ratio as the environmental distribution of radioactive iodine was different from that of stable iodine and radioactive cesium. Concentration ratios (CR) of 129I in muscle of freshwater fish ranged from 85 to 544 across waterbodies with limited water exchange, similar in Fukushima and Chernobyl, but varied with respect to fish species. Thus, this is the first results on the transfer of 129I to freshwater fish, showing that the CR for freshwater fish is higher than CR reported for marine fish. Concentrations of 129I in fish muscle were, however, lower than in the intestinal content, indicating the influence of more contaminated dietary ingredients probably of terrestrial origin based due to δ13C signal on as well as of biodilution. The present results highlighted also that the radiation dose in fish was highly inhomogeneously distributed. Based on the present 129I/127I atomic ratio of 10−5 in the most contaminated fish in the ponds in Fukushima and Glubokoye lake in Chernobyl, however, a radiation dose of 10 μSv/y would not pose any harm to the fish population.

The Salinity of the Great Salt Lake and Its Deep Brine Layer

The Great Salt Lake is a highly saline terminal lake with considerable fluctuations in water surface elevation and salinity. The lake is divided into two arms by a railroad causeway. River inflows enter the larger south arm, while the north arm only receives minimal surface runoff. Evaporation from both arms and limited exchange of water and salt through causeway openings result in complex water and salinity processes in the lake. The north arm is typically homogeneous and close to saturation. The south arm is typically stratified with periodic occurrences of a deep brine layer. This paper analyzes the lake’s long-term historical salinity and water surface elevation data record. Its purpose is to better document the movement of salt and changes to salinity in time and space within the lake and the occurrence and extent of its deep brine layer. This work is important because of the lake’s salinity-dependent ecosystem and industries as well as the role played by the deep brine layer in the concentration of salt and contaminants. We documented that the deep brine layer in the south arm is intermittent, occurring only when causeway exchange supports flow from the north to the south arms. We found that the overall mass of salt in the lake is declining and quantified this in terms of mineral extraction records and historical density measurements.

Regulation of marine plankton respiration: A test of models

Plankton respiration is a major process removing oxygen from pelagic environments and constitutes one of the largest oxygen transformations in the sea. Where the O2 supplies due to dissolution, advection and oxygenic photosynthesis are not sufficient, hypoxic, or anoxic waters may result. Coastal waters with limited water exchange are especially prone to have low oxygen levels due to eutrophication and climate change. To support marine environmental management in a period of rapid climate change, we investigated the current knowledge of regulating plankton respiration based on field and experimental studies reported in the literature. Models for regulation of plankton respiration was tested on a three-year field data set. Temperature is the most reported predictor positively influencing plankton respiration (mean r2 = 0.50, n=15). The organic carbon supply driven by primary production has a similar coefficient of determination but fewer reported relationships (mean r2 = 0.52, n=6). Riverine discharges of dissolved organic carbon can override the influence of primary production in estuaries precluding effects of nutrient reductions. The median predictions of respiration regulation produced by current models vary by a factor of 2 from the median of observed values and extreme values varied even more. Predictions by models are therefore still too uncertain for application at regional and local scales. Models with temperature as predictor showed best performance but deviated from measured values in some seasons. The combined dependence of plankton respiration on temperature, phytoplankton production and discharge of riverine organic carbon will probably lead to increased oxygen consumption and reduced oxygen levels with projected climate change. This will be especially pronounced where increased precipitation is expected to enhance riverine discharges of carbon compounds. The biologically mediated transfer of carbon for long-term storage in deeper layers will slow down. Implementation of plankton respiration measurements in long-term ecological monitoring programs at water body and basin scales is advocated, which would enable future multivariate analyses and improvements in model precision across aquatic environments.

Are the consequences of lithium in marine clams enhanced by climate change?

Coastal areas, such as estuaries and coastal lagoons, are among the most endangered aquatic ecosystems due to the intense anthropogenic activities occurring in their vicinity. These areas are highly threatened by climate change-related factors as well as pollution, especially due to their limited water exchange. Ocean warming and extreme weather events, such as marine heatwaves and rainy periods, are some of the consequences of climate change, inducing alterations in the abiotic parameters of seawater, namely temperature and salinity, which may affect the organisms as well as the behaviour of some pollutants present in water. Lithium (Li) is an element widely used in several industries, especially in the production of batteries for electronic gadgets and electric vehicles. The demand for its exploitation has been growing drastically and is predicted a large increase in the coming years. Inefficient recycling, treatment and disposal results in the release of Li into the aquatic systems, the consequences of which are poorly understood, especially in the context of climate change. Considering that a limited number of studies exist about the impacts of Li on marine species, the present study aimed to assess the effects of temperature rise and salinity changes on the impacts of Li in clams (Venerupis corrugata) collected from the Ria de Aveiro (coastal lagoon, Portugal). Clams were exposed for 14 days to 0 μg/L of Li and 200 μg/L of Li, both conditions under different climate scenarios: 3 different salinities (20, 30 and 40) at 17 °C (control temperature); and 2 different temperatures (17 and 21 °C) at salinity 30 (control salinity). Bioconcentration capacity and biochemical alterations regarding metabolism and oxidative stress were investigated. Salinity variations had a higher impact on biochemical responses than temperature increase, even when combined with Li. The combination of Li with low salinity (20) was the most stressful treatment, provoking increased metabolism and activation of detoxification defences, suggesting possible imbalances in coastal ecosystems in response to Li pollution under extreme weather events. These findings may ultimately contribute to implement environmentally protective actions to mitigate Li contamination and preserve marine life.

The habitat differentiation, dynamics and functional potentials of bacterial and micro-eukaryotic communities in shrimp aquaculture systems with limited water exchange

The habitat differentiation, dynamics and functional potentials of bacterial and micro-eukaryotic communities in shrimp aquaculture systems with limited water exchange

Analysis of the impact of nutrients deposited from the land side on the waters of Puck Lagoon (Gdańsk Basin, Southern Baltic): A model study

The article analyzes the impact of nutrients (nitrates and phosphates) supplied from the land on the waters of the Puck Lagoon (Gdańsk Basin, southern Baltic). The study is based on the numerical modelling. The model data was verified by comparison with the in situ measurement data. The spatial and temporal variability of the concentrations of nitrate, phosphate, and chlorophyll a were analyzed. We came to the conclusion that the load of nutrients deposited from the land side to the waters of the Puck Lagoon is relatively small (but not negligible compared to the Vistula River). However, even when a little runoff enters the reservoir with a very limited water exchange, like the Puck Lagoon, there are periods when riverine nutrients load significantly affects the functioning of the ecosystem.

СОДЕРЖАНИЕ МИКРОПЛАСТИКА ВО ЛЬДУ, СНЕГЕ И ПОДЛЁДНОЙ ВОДЕ КУРШСКОГО ЗАЛИВА ЗИМОЙ 2021Г.

Contamination of the water column, bottom sediments and beaches with small plastic particles (microplastics, MPs, < 5 mm) is currently being actively investigated, but data on ice and snow contamination are still very limited. The paper presents the results of the analysis of the number of MPs particles (0.3–5 mm) in ice cores, snow samples and underice water of the Curonian Lagoon (Baltic Sea), sampled at five stations on February 19, 2021. Higher ice contamination is confirmed: expressed in the number of MPs particles (0.3–5 mm) per 1 liter of (thawed or natural) water, it averaged at 66.4 items/l for snow, 90.5 items/l for ice and 9.1 items/l for under-ice water. Significantly increased amount of MPs particles (up to 281 items/l) were observed in the surface layer of ice (1.5–3 cm). This may in the given case be the consequence of the accumulation of contamination coming from the atmosphere: in the mild Baltic climate, the alternation of thaws and frosty periods favoures the formation of the upper layers of ice from the snow on it. The synthetic nature of the particles was confirmed by Raman spectrometry, which showed the presence along with polyethylene (15 %) also, a significant number of heavy types of plastics (polyurethane, polyvinyl acetate, polyacrylonitrile, etc., in total more than 24 %). Fibers made up about 95 % of the particles, films 1% and fragments – 4 %. The under-ice waters of the Curonian Lagoon, containing from 5.9 to 15.3 MPs particles per liter, turned out to be more than two orders of magnitude more contaminated than the waters of the Baltic Sea, having an average of 0.03 MPs particles per liter in the same particle’ size range. This confirms the general tendency of accumulation of MPs in bays and estuaries of rivers with limited water exchange with the sea.

The effects of different stocking densities on nursery performance of Banana shrimp (Fenneropenaeus merguiensis) reared under biofloc condition

Abstract The effects of banana shrimp Fenneropenaeus merguiensis stocking density on water quality, growth performance, survival rate and body composition was assessed in a biofloc system with limited water exchange. The study was conducted for 32 days with an average larvae weight of 10 ± 0.85 mg in fiberglass tanks containing 120 L of water at four stocking densities. Five experimental treatments consisted of a control (density 1000 shrimps/ m3) with 50% daily water exchange and four biofloc treatments with limited water exchange (0.5% daily) at four stocking levels (1000 shrimps, T1; 2000 shrimps, T2, 3000 shrimps, T3 and 4000 shrimps, T4/ m3) were considered. According to the results, total ammonia nitrogen (0.99 mg/L) and nitrite levels showed higher amounts in the control compared with the other treatments (P<0.05). Growth performance and survival rate (95.55%) in the biofloc treatment with a density of 1000 shrimps/ m3 were higher than the other treatments (P<0.05). The proximate composition of shrimp body and biofloc produced in rearing tanks depended on the stocking density, so the shrimp body ash increased along with the enhancement of stocking density. The lowest amount of ash (31.53± 0.81%) and protein (26.38 ± 1.26) of bioflocs was observed in T1 treatment. The present study showed that stocking density affects the water quality, growth performance, survival rate and body composition of banana shrimp larvae in a biofloc system. More improved indices of water quality, growth performance and survival rate were observed with the least stocking density of 1000 shrimps/m3 in the limited water exchange system.

Biofloc as a Food Source for Banana Shrimp Fenneropenaeus merguiensis Postlarvae

AbstractThe aim of this study was to investigate the effect of different levels of wet biofloc on water quality and feeding, growth performance, survival, and body composition of banana shrimp Fenneropenaeus merguiensis. The experiment consisted of the control group (feeding 100% commercial feed and 50% water exchange per day without biofloc) and four treatments in which portions of the commercial feed were replaced by wet biofloc (T2: 25%, T3: 50%, T4: 75%, and T5: 100%) with limited water exchange. Postlarvae of banana shrimp (mean ± SD weight of 4.5 ± 0.68 mg, density of 5 postlarvae/L) were experimentally held in fiberglass tanks with 170 L of seawater with salinity of 28‰ for 30 d. An acceptable range of total ammonium nitrogen and nitrite nitrogen was maintained in rearing tanks with wet biofloc throughout the experiment despite minimal water exchanges, but total ammonium nitrogen and nitrite nitrogen were significantly higher in the control group. Postlarvae fed with 25% wet biofloc had significantly higher total biomass (222.36 g) and survival (76.27%) compared with the other treatments. A comparison of banana shrimp fed with 25% or 50% wet biofloc and those fed with 100% commercial feed did not show a significant difference in body composition. The highest levels of body ash (12.7% of dry weight) were obtained in banana shrimp fed with 100% wet biofloc. In general, it was found that up to 50% of commercial feed can be replaced with wet biofloc (developed under the conditions of this study) without compromising growth performance, survival, and carcass quality of banana shrimp postlarvae.

Integrated multitrophic aquaculture (IMTA) as an environmentally friendly system for sustainable aquaculture: functionality, species, and application of biofloc technology (BFT).

Aquaculture is one of the fastest-growing industries in the world, and its prominent role has been proven in supplying food for the growing world population. The expected growth of aquaculture requires the development of responsible and sustainable approaches, technologies, culture systems, and practices. The integrated multitrophic aquaculture (IMTA) system has been developed over the past decades. This system is based on the use of all food levels for simultaneous production of some aquaculturally species in a way that contributes to environmental sustainability (biocontrol), economic stability (product diversity and risk reduction), and social acceptance (better management operations). In IMTA, selecting suitable culture species and considering their appropriate population size is absolutely necessary to achieve an optimal biological and chemical process, improving the ecosystem health and sustainability of the industry. Biofloc technology (BFT) is closely related to the IMTA system, where the IMTA potential can be used to control suspended solids in aquaculture systems with limited water exchange. This study reviews the significance of IMTA systems, potential target species for cultivation, the relationship between BFT and IMTA, total suspended solids control, the economics of IMTA farming, and the recent findings in these fields.