Long-Term Harmful Algal Blooms and Nutrients Patterns Affected by Climate Change and Anthropogenic Pressures in the Zhanjiang Bay, China

Climate change and anthropogenic pressures have significantly affected coastal environments. This study obtained historical data on harmful algal blooms (HABs) nutrient patterns over a 30-year period to explore responses long-term climate pressure indicators. Although the surrounding area has achieved great economic success past 30 years, Zhanjiang Bay (ZJB) been seriously by various pollutants is threatened increasing eutrophication HABs due pressures. In ZJB, rarely occurred before 1980s but periodically frequently since 2000s. The largest HAB covered cumulative of 310 km 2 in 2005. Most during spring. Additionally, dominant phytoplankton species were Skeletonema costatum Phaeocystis globosa , accounting for 37.50 43.75% observed, respectively. Anthropogenic caused regime increased ZJB three decades ( P < 0.05). Specifically, concentration dissolved inorganic nitrogen (DIN) threefold from beginning 1990 2019 period, while phosphorus (DIP) 21-fold. Unsynchronized variation led changes composition nutrients, ecosystem shifted P-limited oligotrophic state 2000s an N-limited eutrophic state. indicators showed significant linear correlation with nutrients 0.05), did not play direct role problem this > Therefore, integrated land-ocean environment management should be introduced reduce land-based pollution sources, mitigate eutrophication, curb algae ZJB.