No abstract

In recent years, antibiotics pollution has caused serious harm to the aquatic environment, and microalgae mediated degradation of antibiotics has attracted increasing attention. However, the potential toxicity of antibiotics to keystone microalgae species or their microalgae consortia, and the impact of microalgal diversity on antibiotic removal need to be further studied. In this study, we investigated the removal efficiency and tolerance of five freshwater microalgae (Chlorella pyrenoidosa, Scenedesmus quadricauda, Dictyosphaerium sp., Haematoccocus pluvialis, and Botryococcus braunii) and their microalgae consortia to sulfamethoxazole (SMX). We found that the removal efficiency of SMX by C. pyrenoidosa reached 49%, while the other four microalgae ranged between 9% and 16%. In addition, C. pyrenoidosa, S. quadricauda, and Dictyosphaerium sp. had better tolerance to SMX than H. pluvialis, and their growth and photosynthesis were less affected. At 10 and 50 mg/L SMX, the removal capacity of SMX by mixed microalgae consortia was lower than that of C. pyrenoidos except for the consortium with C. pyrenoidos and S. quadricauda. The consortia generally showed higher sensitivity towards SMX than the individual species, and the biochemical characteristics (photosynthetic pigment, chlorophyll fluorescence parameters, superoxide anion (O2-), superoxide dismutase activity (SOD), malondialdehyde (MDA) and extracellular enzymes) were significantly influenced by SMX stress. Therefore, the removal of antibiotics by microalgae consortia did not increase with the number of microalgae species. Our study provides a new perspective for the selection of microalgal consortia to degrade antibiotics.

During a survey of freshwater diatoms from Mojiang River, Chebaling Nature Preserve in Shaoguan City, Shixing County, Guangdong Province, China, a new Encyonema species, Encyonema chebalingense sp. nov., was discovered. Based on observations with light and scanning electron microscopy, a detailed morphological description of E. chebalingense is here presented. The main features of E. chebalingense include: conspicuously asymmetrical and dorsiventral, semielliptical to semielliptical–lanceolate valves, with a filiform raphe; dorsal margin clearly arched and ventral margin nearly straight or slightly concave; central area on the ventral side formed by 1–2 shorter central striae; and short tectullae projecting within the striae. The new species was compared with some similar species, all of which show similarities to E. chebalingense but differ in features such as dimensions, internal valve structure, stria density and valve shape. This genus is common and abundant in relatively clean waters, and other new species most likely will be recorded in the future from China.