Key environmental predictors of Noctiluca scintillans distribution in the China Sea and its climate change response

Abstract

Noctiluca scintillans is one of the most common harmful algal species worldwide. In this study, a MaxEnt model was constructed to calculate the present and future habitat suitability of N. scintillans in the China Sea. A comprehensive evaluation index of variable importance was defined to measure the importance of key predictors in the model, and offshore distance, long-term average minimum primary productivity, water depth, long-term average minimum temperature, and minimum salinity were determined as the dominant drivers. The HAB index that was constructed by integrating the carrying capacity and habitat suitability characteristics was used to measure the risk of harmful algal blooms (HABs). The index indicated that high-risk areas of HABs caused by N. scintillans occurred around Hainan Island, Taiwan Island, the coastal areas of Guangdong, Fujian, and Zhejiang provinces, and the eastern nearshore area of Weihai in Shandong. Regardless of the greenhouse gas emission scenario, the occurrence of N. scintillans red tides was predicted to persist until 2100. Moreover, the total area of the HABs high zone was predicted to increase under RCP2.6 and decrease under RCP8.5, and the center of the integrated HABs high zone was predicted to be concentrated in the central area of the entire China Sea spanning 15°N to 33°N.