Phosphorus forms and enzyme activities in surface sediment in a polyculture system consisting of Apostichopus japonicus and Styela clava

Abstract

A polyculture system consisting of <em>Apostichopus japonicus</em> and <em>Styela clava</em> was utilized in this study. Phosphorus content and forms in the surface sediment were analyzed together with the activity levels of several enzymes. Various forms of phosphorus in the polyculture system were higher than that in the traditional aquaculture systems. The total phosphorus content ranged from 421.3 mg•kg^-1 to 486.7 mg•kg^-1 in the polyculture system, while only 349.3 mg•kg^-1 to 432.7 mg•kg^-1 in the traditional aquaculture systems. However, Fe/Al-bound phosphorus accounted for only 30 % of the inorganic phosphorus in the polyculture system. The activities of urease, alkaline phosphatase, polyphenol oxidase, and catalase in the polyculture system were enhanced in comparison with their activities in the traditional system, which may explain why the integrated system was not eutrophic. These results reveal that the<em> A. japonicus</em> - <em>S. clava</em> polyculture system should be explored as a method of overcoming the current limitations of <em>Apostichopus japonicus</em> aquaculture industry.