Bioavailability of Organic Phosphorus Compounds to the Harmful Dinoflagellate Karenia mikimotoi.

Kaixuan Huang,Yanqing Zhuang,Yuzao Qi,Zhou Wang,Songhui Lu,Jingyi Cen,Linjian Ou

doi:10.3390/microorganisms9091961

Abstract

Karenia mikimotoi is one of the most well-known harmful bloom species in temperate coastal waters. The present study investigated the characteristics of alkaline phosphatase (APase) and phosphodiesterase (PDEase) activities in hydrolysis of two phosphomonoesters (adenosine triphosphate (ATP) and ribulose 5-phosphate (R5P)) and a phosphodiester (cyclic adenosine monophosphate (cAMP)) in K. mikimotoi and compared its growth and physiological responses to the different forms of phosphorus substrates. K. mikimotoi produced comparable quantities of APase and PDEase to hydrolyze the organic phosphorus substrates, although hydrolysis of the phosphomonoesters was much faster than that of the phosphodiester. The growth of K. mikimotoi on organic phosphorus substrates was comparable to or better than that on inorganic phosphate. The difference in particulate organic nutrients (carbon, nitrogen, and phosphorus) and hemolytic activity supported different rates of hydrolysis-assimilation of the various organic phosphorus substrates by K. mikimotoi. The hemolytic activities of K. mikimotoi in the presence of organic phosphorus substrates were several times those in the presence of inorganic phosphate during the exponential phase. This suggested the potential important role of organic phosphorus in K. mikimotoi blooms.

Highlights

dissolved inorganic P (DIP) increased to 0.51–0.65 μmol L−1 in the first few days and decreased to lower than 0.10–0.20 μmol L−1 after day 12 in the adenosine triphosphate (ATP), ribulose 5-phosphate (R5P), and cyclic adenosine monophosphate (cAMP) treatments
DIP increased to 0.51–0.65 μmol L−1 in the first few days and th to lower than 0.10–0.20 μmol L−1 after day 12 in the ATP, R5P, and cAMP tr
The nutrient structure in coastal waters has changed from N deficiency to P deficiency, especially during the periods of spring and summer when K. mikimotoi blooms occur [18,21,23]

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Karenia mikimotoi is one of the most well-known harmful bloom-causing species in temperate coastal waters around the world [1,2,3]. K. mikimotoi can produce various toxic substances, such as hemolytic compounds [1,4], cytotoxins [3,5], and reactive oxygen species [3,6], and can cause massive mortality of both wild and cultured fish and shellfish. In East Asia, especially in China and Japan, the frequency of K. mikimotoi blooms has increased greatly in recent years [7,8]. Blooms caused by K. mikimotoi accounted for

Objectives

Methods

Results

Discussion

Conclusion