Differences of photosynthesis and nutrient utilization in Sargassum fusiforme and its main epiphyte, Ulva lactuca

Sargassum fusiforme is often adversely affected by epiphytic algae during its cultivation. However, the biological differences between S. fusiforme and the epiphytic algae have not yet been elucidated detrimental to the management of S. fusiforme culture. In this study, we sampled S. fusiforme and main epiphytic algae Ulva lactuca in a marine culture cycle and compared their biological characteristics. It indicated that, except during low-temperature months (January and March), the photosynthetic electron activity of U. lactuca were generally higher than S. fusiforme. The nitrogen uptake rates of S. fusiforme and U. lactuca were all significantly higher in the earlier growth stage than other stages. In most cases, the nitrogen uptake and utilization of U. lactuca was higher than those of S. fusiforme. Although S. fusiforme absorbed more trace elements, U. lactuca had relatively strong photosynthesis and nutrient absorption performance; thus, the latter accumulated more soluble carbohydrate and protein and may have stress effect on S. fusiforme. This study will be helpful for understanding the differences in the biological characteristics of economic seaweed and its epiphytic macroalgae and provides a reference for the friendly management and healthy development of seaweed cultivation.