International Journal of Aquaculture, 2025, Vol.15, No.2, 57-66 http://www.aquapublisher.com/index.php/ija 63 7.2 Water pollution and eutrophication issues Water pollution is a big problem, especially when nutrients flow into water from farmland or cities, which can cause eutrophication. When there is too much nitrogen and phosphorus in the water, algae and cyanobacteria will reproduce in large quantities. They grow too fast and consume oxygen in the water, which eventually leads to the inability of fish and other organisms in the water, forming the so-called “dead zone” (Briland et al., 2020; Zhang et al., 2024). Too much harmful algae can also damage the original food web. For example, they will prevent fish from finding enough or suitable food, affect their nutritional intake, and also change the relationship between different organisms. 7.3 Disruption of aquatic food webs by climate change Climate change is also a major problem for aquatic ecosystems. Rising temperatures, changing rainfall distribution, and even increasing extreme weather will affect the lives of organisms in the water. These changes may reduce some species and others increase, causing food webs to become less balanced. For example, rising water temperatures will make phytoplankton grow faster, thereby amplifying the original “nutritional cascade effect” and may also make the eutrophication problem worse (Bouraï et al., 2020). Climate change may also make pollution worse and may also make alien species more prone to invasion. Once these pressures are added together, ecosystems are more prone to losing stability (Gallardo et al., 2016; González-Olalla et al., 2023). 8 Conservation and Management Strategies 8.1 Ecosystem restoration measures To keep the aquatic ecosystems in balance, we need to take some restoration measures. This is especially important today when global environmental changes are becoming increasingly obvious. Most recovery efforts start by reducing nutrient pollution in the water. Because too much nitrogen and phosphorus in the water will cause eutrophication and disrupt the original nutritional relationship. Some research has specifically analyzed some ecological restoration projects in China and found that long-term monitoring is very important. This can help us judge whether animals, plants and environments return to normal (Fu et al., 2022). However, the study also found a problem: Although water quality (such as nitrogen and phosphorus) improves quite quickly, biodiversity (such as fish and aquatic plants) recovers slowly. Another point is very important, different methods should be used in different places. Measures such as intercepting sewage and building artificial wetlands will have more obvious results if the location is selected well, especially in river systems (Wang, 2024). 8.2 Policies for sustainable fisheries development In order to prevent fish from being caught and ensure that fishermen can get a harvest, we must implement sustainable fishery management. It's not just about limiting the number of fishing. We also need to understand the relationships of the entire food web, such as the effects of phytoplankton and zooplankton on fish populations (Stock et al., 2017; Lomartire et al., 2021). In some places, such as the Celtic Sea and the Bay of Biscay, scientists use nutritional models to simulate ecosystems. They found that focusing on only one species may ignore the chain reaction of the entire ecosystem. For example, overfishing of large fish can affect the number and relationship of lower organisms (Moullec et al., 2017). Therefore, relevant policies should find a balance between “protecting the ecology” and “ensuring fishery development”. We must not only allow people to live fishing, but also not let the ecosystem hurt.. 8.3 Public engagement and awareness in ecosystem protection It is not enough to rely solely on experts and governments, and the participation and environmental awareness of ordinary people are also important. For example, if you know how important zooplankton is to replenish fish, you will be more willing to protect the water environment. Similarly, letting more people understand that phytoplankton regulates climate and purifies water quality can also help promote better management policies (Tweddle et al., 2018). If the public participates, such as participating in environmental protection activities and supporting ecological policies, the effect will be better. Only by working together can we maintain a good water environment and promote sustainable development (Funge‐Smith and Bennett, 2019).
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