International Journal of Marine Science, 2024, Vol.14, No.4, 285-294 http://www.aquapublisher.com/index.php/ijms 291 Figure 2 Global distribution of eutrophic coastal marine ecosystems (Adapted from Breitburg et al., 2018) Image caption: Recent coastal surveys by the United States and the European Union found that 78% of U.S. coastal waters and 65% of Europe’s Atlantic coastal waters exhibit symptoms of eutrophication (Adapted from Breitburg et al., 2018) 7.2 Examples from developing countries In developing countries, rapid economic development and urbanization have exacerbated eutrophication issues. Shenzhen Bay in China, for example, has been heavily influenced by anthropogenic activities, leading to severe eutrophication. However, intensive management actions implemented since 2000 have shown improvements in water quality and a reduction in nutrient loads (Zhou et al., 2019). The East China Sea is another example where increased nutrient loading has led to significant eutrophication, exacerbated by synergies with other pressures such as overfishing and coastal development (Malone and Newton, 2020). These cases highlight the challenges faced by developing countries in managing eutrophication, often due to limited resources and infrastructure for effective nutrient management. 7.3 Lessons learned and best practices Several lessons can be drawn from these case studies. First, the importance of integrated and sustained management of both point and diffuse sources of nutrients is evident. In developed countries, reductions in point source inputs from sewage treatment plants have been successful, but controlling diffuse sources remains challenging (Malone and Newton, 2020). Second, the need for long-term monitoring and adaptive management is crucial, as recovery from eutrophication can take decades and may not always reach baseline conditions (McCrackin et al., 2017). Third, the role of top-down control measures, such as managing predator populations to control algal blooms, should not be underestimated (Östman et al., 2016). Finally, the inclusion of terrestrial organic matter (ter-OM) in monitoring programs can provide a more comprehensive understanding of eutrophication processes and help in developing more effective management strategies (Deininger and Frigstad, 2019). 8 Concluding Remarks Eutrophication in coastal marine ecosystems is primarily driven by anthropogenic nutrient inputs, particularly nitrogen and phosphorus from agricultural, urban, and industrial activities. Excessive nutrient levels lead to the overgrowth of primary producers, triggering a series of ecological problems such as hypoxic "dead zones," harmful algal blooms, and the loss of biodiversity. Additionally, factors like overfishing, coastal development, and climate change further exacerbate the effects of eutrophication, placing even greater stress on marine ecosystems. Despite various efforts to reduce nutrient loading, eutrophication and hypoxia remain persistent issues, with significant regional differences in the severity of impacts and the potential for ecosystem recovery.
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