Colorimetric analysis is not sufficient to estimate bioavailable phosphorus in a hypersaline aquatic environment
Colorimetric analysis is commonly used to quantify P availability in aquatic environments. However, it may not be adequate to quantify the bioavailability of dissolved organic P compounds. This study aimed to investigate to what extent the colorimetrically measurable P fractions can be utilized by algae, with a particular emphasis on organic P compounds in a hypersaline aquatic environment. In this study, the growth of the marine alga Dunaliella tertiolecta Butcher was observed in axenic hypersaline cultures prepared with different organic P forms and related to the corresponding levels of colorimetrically measured P and total P. The malachite green method was used to colorimetrically analyze the different P forms and inductively coupled plasma-optical emission spectroscopy was used to quantify the total P. The results showed that only creatine P was colorimetrically detectable, of which 87% of its total concentration was measured. The growth of algae in the culture media with organic P compounds did not reflect the colorimetrically measurable organic P compounds. The results from this study imply that colorimetric analysis may not be sufficient to assess P availability to algae in hypersaline conditions where organic P components are the main source of P.
KeywordsAlgal growth Colorimetrically measurable P P bioavailability
This study was conducted within the Framework of Bilateral Collaboration funded by the Research Foundation-Flanders (FWO-Belgium) and the National Foundation for Science and Technology (NAFOSTED-Vietnam). We thank Anita Dehaese and Geert Vandewiele of the Laboratory of Aquaculture and Artemia Reference Center of Ghent University for technical assistance with algal inoculation and counting, and Kristin Coorevits of the Laboratory of Soil and Water Management, KU Leuven for assistance with ICP analysis.
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