Marennine is the blue-green pigment produced by the temperate ubiquiste marine diatom Haslea ostrearia. This pigment is water-soluble and excreted in seawater during H. ostrearia growth and ageing. Previous studies demonstrated the adverse effects of H. ostrearia culture supernatant that contains marennine (Blue Water, BW) against marine organisms. In tropical waters in the Southern hemisphere, a new diatom species has recently been discovered, Haslea nusantara, which shares a peculiarity with H. ostrearia in producing a blue-green, marennine-like pigment. However, little is known about the characteristics of the marennine-like pigment from H. nusantara and its bioactivity. The present study aimed to determine spectral characteristics of BW from H. nusantara in comparison to BW containing marennine of H. ostrearia, using UV–vis spectrophotometry, and to investigate the effects of BWs from these two species on several marine organisms from different trophic levels including autotrophs (Isochrysis galbana) and heterotrophs (Artemia salina). Additionally, the antibacterial activities of these BWs were also evaluated on two bacterial pathogens that are relevant to aquaculture, Vibrio harveyi and Staphylococcus aureus. The results show that both BWs from H. ostrearia and H. nusantara at 0.5 μg mL⁻¹ significantly reduce the growth of I. galbana. At similar range of concentration, toxicity tests reveal that the both BWs from blue Haslea species significantly increase mortality rate of A. salina to a different extent. Additionally, both BWs from H. nusantara and H. ostrearia can inhibit the growth of tested bacterial pathogens. This study provides new insight into the different toxicity in the bioactivity of pigments obtained from the two species of blue diatoms from the same genus. Our results also demonstrate the need to determine concentrations that optimize beneficial effects and critical concentrations not to be exceeded before considering the use of marennine as natural antibacterial agents in the field of aquaculture.

Marennine是由温带无处不在的海洋硅藻Haslea ostrearia生产的蓝绿色颜料。这种色素是水溶性的，并会在ostrearia生长和衰老期间在海水中排泄。先前的研究表明，含有马来宁（蓝水，BW）的ostrearia培养物上清液对海洋生物有不利影响。在南半球的热带水域中，最近发现了一种新的硅藻物种，Haslea nusantara，它与H. ostrearia具有独特之处，可生产蓝绿色，类似于人发氨酸的色素。然而，关于H. nusantara的类麻黄素颜料的特性知之甚少及其生物活性。旨在本研究以确定从BW的光谱特性H. NUSANTARA相比于含有marennine BW H. ostrearia，采用UV-Vis分光光度法，并调查来自这两个物种的BW的几个海洋生物从不同营养水平的影响包括自养生物（Isochrysis galbana）和异养生物（Artemia salina）。此外，还对与水产养殖有关的两种细菌性病原体哈维弧菌和金黄色葡萄球菌进行了评估，评估了这些BW的抗菌活性。结果表明，来自H. ostrearia和H. nusantara的BW在0.5μgmL ^-1下可显着降低银杏的生长。在相似的浓度范围内，毒性测试表明，来自蓝色Haslea物种的两种BW均在不同程度上显着提高了盐沼曲霉的死亡率。此外，来自H. nusantara和H. ostrearia的BW可以抑制被测细菌病原体的生长。这项研究为从同一属的两种蓝色硅藻中获得的色素的生物活性的不同毒性提供了新的见解。我们的结果还表明，在考虑将水杨酸用作水产养殖领域的天然抗菌剂之前，有必要确定最佳有益效果的浓度和不应超过的临界浓度。