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Three Schizochytrium species isolated from three mangrove sites in Taiwan, Erjen River in Kaohsiung (isolate EJ56), Yantian Ecological Park in Tainan (isolate YT90), and Chunan mangrove in Miaoli (isolate CN75), were screened for their tolerance to heavy metals. Two common heavy metal pollutants present in Taiwan rivers were used in this study: copper [Cu(II)] and zinc [Zn(II)]. Growth at varying concentrations of these heavy metals was assessed, as well as their effects on cell morphology. There was a significant reduction in growth of isolate YT90 exposed to minimal concentrations (0.5-8 ppm) of Cu(II) and Zn(II), and isolate CN75 exposed to Cu(II). Isolate EJ56 had growth comparable to the control at 0.5-8 ppm of Cu(II) and Zn(II). Tolerance of the test isolates varied between each of the heavy metals tested. YT90 was most tolerant to Cu(II), and CN75 to Zn(II). Light and scanning electron micrographs of Schizochytrium cells exposed to high levels of heavy metals (>32 ppm) showed formation of holes in the cell wall, as well as shrinkage and general deformation of the cell structure. At the highest heavy metal concentrations tested (256- 384 ppm), cell lysis occurred, resulting in leakage of cellular content. Hence, high concentrations of heavy metal pollutants in mangrove habitats will result in growth retardation of thraustochytrids and, eventually, cell death. [ABSTRACT FROM AUTHOR]

This study evaluated the effect of lead (Pb(II)), zinc (Zn(II)) and copper (Cu(II)) on growth and sporulation of four Halophytophthora species ( Halophytophthora vesicula, Halophytophthora elongata, Halophytophthora spinosa var. lobata, and an oogonia-producing Halophytophthora sp.) isolated from different mangrove sites in Taiwan. Results show that all isolates grew well or even better at 1 ppm concentration of the heavy metals tested. Growth of all test isolates was totally inhibited at 500 ppm, except for H. spinosa var. lobata exposed to Zn(II). For sporulation, all isolates produced moderate to abundant zoosporangia or oogonia at 1 ppm Pb(II) and Zn(II). Production of zoosporangia by H. vesicula, H. elongata and H. spinosa var. lobata was significantly affected or totally inhibited at 1 ppm Pb(II) and Zn(II) and all concentrations of Cu(II). Abnormal oogonia were produced by Halophytophthora sp. at 10 ppm Cu(II) and 100 ppm of the three heavy metals. In general, Cu(II) and Zn(II) were found to be the most toxic, and the least toxic was Pb(II). H. spinosa var. lobata was the most tolerant to all the heavy metals, while H. vesicula and H. elongata were the most sensitive. Results of this study shows that increased concentrations of Pb(II), Cu(II), and Zn(II) in the mangrove environment can significantly affect growth and impair normal reproduction of Halophytophthora species. [ABSTRACT FROM AUTHOR]