Algal growth and alkaline phosphatase activity of 'green tide' Chaetomorpha linum in response to phosphorus stress

Chaetomorpha linum is a bloom-forming macroalgae found all over the world. In the past 10 years, green tides dominated by Chaetomorpha spp. have broken out frequently in the phosphate-deficient Swan Lagoon, China. Here, we evaluated the changes in P concentration and alkaline phosphatase activity (APA) in water and sedi-ments during the growth of C. linum in the laboratory experiment. The objective of this study was to clarify the phosphorus (P) sources supporting the C. linum blooms throughout the year in this phosphate-deficient lagoon. Our results show that C. linum is able to store a large amount of P when phosphate is abundant in the water, and the P in algal tissue can be utilized for algal growth at a short time. This species can also produce alkaline phosphatase (APase) and facilitate the release of mobile P (BD-P and NaOH-P) from sediments when phosphate is deficient in order to sustain growth. The field investigation shows the seasonal differences in the P sources supporting C. linum blooms in Swan Lagoon. In addition to sediment released P, the tissue P in living algae and the dissolved organic P in water are the main utilized P sources in spring and winter, respectively. This possibly explains why C. linum can persist and proliferate in such a lagoon system throughout the year.

Automated summary

Chaetomorpha linum can store a large amount of phosphorus and utilize it for growth when phosphate is abundant, and it can produce alkaline phosphatase and release mobile phosphorus from sediments when phosphate is deficient. The sources of phosphorus supporting the blooms of C. linum vary seasonally in Swan Lagoon.