Effects of nitrogen source and N/P on growth and photosynthesis in the invasive marine macroalga Chaetomorpha valida

The invasive marine macroalga Chaetomorpha valida blooms frequently in Apostichopus japonicus culture ponds in North China, resulting in negative environmental consequences. The factors driving this algal overgrowth are unclear. Previous studies observed that eutrophication strongly influences abnormal growth of nuisance macrophytes, but relatively few studies have addressed the types and abundance of nitrogen in A. japonicus culture ponds during the seasonal progression of a C. valida bloom and the effects of nitrogen source and N/P on C. valida growth and photosynthesis. In this study, we describe the structural features of nitrogen abundance and the seasonal progression of a C. valida bloom and uncover a relationship between nitrogen enrichment and C. valida growth. Common garden experiments demonstrated that C. valida can utilize different forms of nitrogen in the environment for rapid growth. Growth rate and photosynthesis capacity were related to the nitrogen source and N/P ratio. This study will provide a reference for maintenance of ecological balance and healthy aquaculture in A. japonicus culture ponds.