THE CAUSES OF PINK-PURPLE WATER IN THE LAGOON AT GATE NO. 6 IN TAN HAI COMMUNE, TAN THANH DISTRICT, BA RIA–VUNG TAU PROVINCE

Abstract

Recently, the pink-purple water in the lagoon at gate no. 6 in Tan Hai commune, Tan Thanh district, Ba Ria–Vung Tau province has attracted large attention from local governments and public media. This study aimed to assess the water quality and find out the causes of such problem. Physicochemical parameters including BOD₅, COD, TSS, NO₃, NO₂^-, NH₄⁺ và PO₄^3-,... and several heavy metals such as mercury, lead, zinc, cadimi and xyanua were used to assess water quality. Phytoplankton composition was determined by microscopy observation, and the phytoplankton density was estimated by using an Improved Neubauer Chamber. Our results indicated that water trophic state is being eutrophic or hypereutrophic. The “pink-purple water” was caused by the domimant of the green algae Dunaliella salina. D. salina is pink becaused it accumulated very high levels of a carotenoid pigment called β-carotene. To better understand the growth and development of the D. salina, more in-depth studies on environmental conditions regulating the development of D. salina as well as mass cultured to exploit β-carotene and glycerol pigments for aquaculture, pharmaceuticals and dietary supplement are well recommended.