Analysis on scientific knowledge graph of global algal bloom studies

Worldwide, proliferating harmful algal blooms (HAB) have been an ecological catastrophe with negative impacts on ecosystem health, safe water use and sustainable socioeconomic growth. HABs impact nutrient-overenriched eutrophic freshwater and marine water bodies. Here, we searched the HAB literature database for English and Chinese journal articles. Then, we utilized CiteSpace and other software to analyze its scientific knowledge graphs. The results showed: (1) Growing attention and concern about the proliferation and intensification of HABs since the 1940s. Currently, more than 44000 publications (including 172 highly cited papers) have been published in English and Chinese journals. (2) Based on annual publication volume, global HAB research can be roughly divided into three periods:. (1942-1990, <200 articles per year),. (1991-2014, 200 to 2000 articles per year),. (from 2015 to the present, >2000 articles per year). (3) Prof. Paerl (153 papers) and Prof. Songhui Lu (77 papers) were the scholars with the most publications in English and Chinese articles, respectively. The most prevalent journals for HAB research publications are Harmful Algae and Journal of Lake Sciences in English and Chinese journals, respectively. The findings published in Limnology and Oceanography are crucial to an in-depth understanding of HAB dynamics. (4) The largest source of English literature is the United States and the second is China. There is a growing amount of international interaction and collaboration in HAB research. In Chinese publications, the Chinese Academy of Sciences is at the core of collaborative networks conducting HAB research in China, and its major standing on algal bloom research is on par with the international levels. (5) In terms of worldwide HAB research, Chinese HAB research has a significant place. However, Chinese journal articles' research output appears to lag behind that of English journal articles in terms of new directions and perspectives. (6) The co-occurrence of the keywords reveals the popular topics in HAB research. Emergent words reveal new research directions and emerging perspectives. The primary themes of global HAB study are reflected in keyword clustering, which also signals future directions and developments. Multi-disciplinary and multi-scale research approaches have served as a catalyst for an improved understanding of the complex and interactive factors controlling HAB establishment, proliferation and ultimately control. On a geographical scale, the focus on HAB dynamics now includes spatio-temporal studies of global, national, regional, and local water bodies. On the temporal scale, the focus is on HAB dynamics in extensive time series such as yearly, monthly, daily or even shorter term. On a disciplinary level, researchers are examining bloom-forming mechanisms and environmental drivers from biogeochemical, ecological, and geographic perspectives along the freshwater to marine continuum. Research techniques such as HAB monitoring and early warning models, remote sensing, on-line video observation, and image analysis will also be crucial. Big data and artificial intelligence analysis may be crucial methods for next study, since they are based on field observations, experimental studies, and numerical simulations. Future research will continue to focus on the mechanisms that govern how blooms are formed, proliferate and dissipate, as well as how environmental factors (both biological and abiotic) mediating these processes. Future research topics that may be significant include the quantitative analysis of the ecological and environmental effects of the entire life cycle process of algal blooms (including the impact on aquatic ecosystems, climate change, and human health, among other things), as well as the reciprocal feedback mechanism between human activities (including treatment and sewage discharge), climate change and extremes (floods, droughts, atmospheric changes and perturbations) and algal blooms.