Applications of Nanotechnology in Aquaculture
Abstract
The rapidly growing industry of aquaculture plays a vital role in satisfying global seafood demand and alleviating pressure on wild fisheries. Despite its expansion in recent decades, aquaculture continues to face various bottlenecks and challenges. Nanotechnology offers solutions to a number of these challenges. This paper discusses how nanotechnology development is expected to contribute to the advancement of aquaculture by improving fish farm technology. The specific topics focused on include nanotechnology applications to fish feed formulation, disease control, water filtration, and seafood packaging. These are areas in which published research highlights the potential of nanotechnology to improve aquaculture production and sustainability. To provide a complete perspective of nanotechnology’s role in aquaculture, the obstacles and prospects of nanotechnology development within aquaculture are discussed as well.
Introduction
The world population is projected to grow to nearly 10 billion people by 2050 (United Nations 2017). This means a vast increase in the global demand for food. In order for the global food system to keep pace with escalating demand, the agricultural sector will have to become increasingly efficient and productive. One aspect of the agricultural sector that has grown profoundly over the last several decades is aquaculture, the farming of aquatic organisms. Considering the rate at which human consumption of seafood continues to rise, aquaculture production will likely play a significant role in food production around the world. Since 1961, the annual increase in global seafood consumption has consistently doubled the rate of global population growth (FAO 2018). Unfortunately, many fisheries are facing decline due to overfishing, pollution, and climate change. Aquaculture addresses both the need for increased global seafood production and the need to reduce human dependence on wild fisheries. In order to effectively achieve these goals, the aquaculture industry will need to expand production in a sustainable manner. This will require aquaculture operations to overcome various obstacles, including the use of feed sourced from wild-caught organisms and the release of environmentally harmful wastewater. Fish farms often hold fish and shellfish in high densities which can allow diseases to proliferate and cause mortality or declines in food quality. The use of nanotechnology, defined as the manipulation of materials less than 100 nanometers in size, offers solutions to these obstacles. This paper highlights the applications of nanotechnology in the field of aquaculture, with a focus on ways in which it efficiently improves production. Research has shown that nanotechnology can improve nutrition uptake in aquatic organisms, reducing the amount of feed necessary to attain sufficient fish growth. Additionally, nanotechnology has been incorporated into filters to improve wastewater treatment and is also being used to administer vaccines and control fish disease (Luis et al. 2019). Like the field of aquaculture, nanotechnology is rapidly growing. As nanotechnology continues to advance, its prevalence and function within aquaculture will likely enhance production capabilities beyond contemporary limits.
Nanotechnology in Fish Feeds
As fish consume food and assimilate nutrition in the form of lipids, proteins, carbohydrates, minerals, and vitamins, some components of the feed pass through their digestive systems unabsorbed and are released as waste. Considering that feed is a major cost to commercial aquaculture operations, more efficient nutrient assimilation can potentially save money, as well as reduce waste production. Many fish farms use feeds that are produced from wild-caught organisms, inhibiting the sustainability of aquaculture operations. This reliance on fisheries can be mitigated by improving feed-use efficiency. Incorporating nanotechnology into fish feed formulation has been shown to boost nutritional assimilation and lead to increased fish growth and reduced feed demand. Diets formulated with nanoscale material have a higher surface area to volume ratio than conventional feed, allowing the digestive systems of fish and shellfish to absorb a higher proportion of nutrients. Incorporating iron nanoparticles into the feed regimen of sturgeon and carp was shown to increase growth of these species by 30 and 24 percent, respectively (Bhattacharyya et al. 2015). As shown in table 1, Onuegbu et al (2018) tested the effects of zinc oxide nanoparticles within the diet of African catfish and found that it led to significantly higher growth than a control bulk zinc oxide diet. This result was obtained despite higher protein and fat content within the control diet. Similarly, supplementing nano-selenium into the diet of crucian carp led to increases in weight, relative weight gain rate, and antioxidant levels (Ashraf et al. 2011).
Aside from contributing to growth, use of nanoparticle-based fish feeds may also improve aquatic organism health. By boosting rates of nutrient absorption, these nano-feeds cause fish to excrete less waste per unit of feed, leading to enhanced water quality and reduced potential for microorganisms like bacteria, viruses, and algae to grow within fish tanks. This reduces the volume of wastewater effluent produced by fish farms. If nanoparticle-based diets become widely available in the commercial fish feed market, they could offer farmers an economical approach to augmenting their production while reducing the environmental footprint of their facilities.
Nanotechnology in Disease Control
Disease outbreak is a major hindrance to aquaculture production. Proliferation of bacteria, viruses, fungi, algae, and parasites can lead to the loss of an entire crop of fish or shellfish. In some cases, diseases have hampered production across an entire country or region, as was the case with white spot disease outbreaks in Southeast Asia throughout the 1990s and into the early 2000s (Karunasagar and Ababouch 2012). Because aquaculture operations look to maximize output and profit, they often rear organisms at the maximum density that their facility’s biological filtration allows. This high-density production allows diseases to spread rapidly, making quick and efficient response to disease outbreak crucial to maintaining an aquaculture operation. A number of recent nanotechnological developments appear to serve as effective means of aquatic disease control.
In some cases, vaccination has served as a sufficient approach to combatting disease, but contemporary methods of administering vaccine have been shown to cause adverse side effects. Nanoparticle carriers, such as chitosan and polylactide-coglycolide acid, can deliver vaccine antigens to fight bacterial and viral diseases while minimizing side effects (Rather et al. 2011). These nanoparticle-based vaccines can be delivered widely by using nanocapsules that are absorbed by fish cells but resistant to digestion or degradation. These capsules contain short strand DNA that is programmed to elicit immune responses from fish upon absorption (Rather et al. 2011). Nano-particle based vaccines offer an economical and efficient way to manage disease in aquaculture.
Highly effective bacterial sterilization has been achieved using nanoparticles as well. Under UV lights, TiO2 was shown to sterilize E. coli and Vibrio anguillarum bacteria at a rate of over 95% after 2 hours (Huang et al. 2015). Controlling these bacterial species is a major focus in the aquaculture industry as they lead to significant losses of production and human health concerns.
Nanotechnology in Water Filtration
Nanotechnology offers tools for removing water contaminants across a variety of scales. From household filters to industrial water treatment systems, these nano-enabled technologies are already being heavily studied and applied.
A form of water filtration commonly referred to as biofiltration is a necessary component of any aquarium or aquaculture system. It involves passing water though a high surface area material that houses beneficial bacterial films. The bacteria convert ammonia, the principle toxic waste product released by fish, to nitrite and then nitrate, which is significantly less toxic. Nanomaterials such as carbon, alumina, zeolite additives, and iron-containing compounds can effectively house the beneficial bacteria to provide biofiltration (Ashraf et al. 2011). Due to their nanoscale size, these materials can provide significantly more surface area for biofilm colonization than conventional materials used in the aquarium and aquaculture industry. Use of a nanoparticle-based filter media known as nano-ecobase was shown to remove ammonia and nitrite from aquaculture wastewater at high rates (Huang et al. 2015).
Control of biofouling organisms is another concern within the aquaculture industry. Biofouling occurs when organisms like bacteria, algae, or invertebrates colonize surfaces where they are unwanted. It can be costly to remove or cope with these organisms. They tend to reduce the efficiency of water flow through pipes or across filtration surfaces, thus inhibiting the production of the system. Nanoparticle-based coatings made of metal oxides such as copper, zinc, or silicone, have been shown to serve as an effective antifouling surface (Rather et al. 2011). These nanomaterials have the potential to improve the longevity of aquaculture equipment and reduce maintenance costs.
The global supply of freshwater is under increasing strain due to industrial contamination, high rates of consumption, and climate change. Nanoparticles have been employed in water filtration across various industries to purify contaminated wastewater effluent and reclaim water for reuse. This technology serves to remove toxic ions, microbes, and other contaminants. Within the aquaculture industry, nanoparticle-based filtration has been used to reclaim polluted water for safe use or to remediate aquaculture wastewater after usage. This can reduce the consumption of clean freshwater by aquaculture operations as it allows farms to utilize water that would otherwise not be safe aquaculture production. Effective nanoparticle filtration methods include aerogels, nano dispersants, nanomembranes, and nano titanium dioxide among others (Bhattacharyya et al. 2015). These materials principally remediate water through high absorption capacity, catalytic activity, entrapment, and other reactive processes. Nano-particle based filtration offers innovative technology across a wide range of applications. Its potential functions in aquaculture could help mitigate wastewater release and clean freshwater consumption, both of which are major environmental drawbacks to aquaculture production.
Nanotechnology in Seafood Processing
The final area in which nanotechnology shows promising potential within the aquaculture industry is seafood processing. Because seafood is a sensitive form of food that spoils relatively quickly under unfavorable conditions, proper storage, packaging, and handling is essential to marketing quality aquaculture products. Nano-polymers and coatings have been applied within seafood packaging to protect delicate products via anti-microbial properties and oxygen impermeability (Ranjan et al. 2014). Ranjan et al. (2014) also note that “smart packaging” has valuable applications within the seafood industry. This term refers to nano-sensors that are placed within packaging to detect contamination or spoilage. Additionally, nanoclays have been extensively studied as a food packaging material due to their ability to serve as an economical and effective mechanical and thermal barrier (He et al. 2019). The nanotechnological innovations in food safety are not limited to seafood processing and are expected to play an increasingly prominent role in the food industry over the coming years. Helmuth Kaiser Consultancy (2004) reported that the nanofood market was expected to expand over seven-fold between 2004 and 2010. As nanotechnology advances facilitate efficient food packaging and processing, aquaculture products can be more widely distributed with reduced concern for spoilage and food safety hazards.
Challenges and Prospects
While research studies highlight the extensive benefits that nanotechnology offers within the field of aquaculture, obstacles to its widespread usage remain. The scale and speed at which aquaculture operations adopt nanotechnology will depend on the safety of using nanomaterials and their potential effects on aquatic organisms, humans, and the environment. Unfortunately, these effects remain largely unknown. Application of nanotechnology within aquaculture is still in its early stages so there is a drastic need for research and safety evaluations (Rather et al. 2011) (He et al. 2019). Because nanomaterials behave differently than bulk materials composed of the same substance, distinct regulatory frameworks and safety evaluation procedures will play a pivotal role in nanotechnology prevalence in general. He et al. (2019) assert that nanofood regulations are currently very broad and general. Investment in studying the environmental and health impacts of nanomaterials is thus crucial to the safe application and public acceptance of this technology. In order for the applications highlighted in this paper to achieve their potential, proactive assessment, legislation, and regulation of nanomaterial usage is key. As nanotechnology develops, its implementation within aquaculture could revolutionize seafood production (Luis et al. 2019).
Summary
In conclusion, nanotechnology offers a wide array of beneficial applications to the expanding industry of aquaculture. Throughout its development, aquaculture has faced major obstacles such as unsustainable feed sources, disease outbreak, wastewater production, high water usage, and seafood product deterioration. Nanotechnological innovations have been shown to address these challenges and will likely become increasingly important as both nanotechnology and aquaculture advance. With population growth and resource depletion demanding rapid and efficient expansion of food production over the coming century, improvements in the production and sustainability of food production is vital. This paper highlighted various research that evidences the functions of nanotechnology within aquaculture, a rapidly growing food industry that is expected to account for an increasing proportion of global seafood production in the future.
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