Reduced calcification of marine plankton in response to increased atmospheric CO2

The formation of calcareous skeletons by marine planktonic organisms and their subsequent sinking to depth generates a continuous rain of calcium carbonate to the deep ocean and underlying sediments. This is important in regulating marine carbon cycling and ocean-atmosphere CO2 exchange. The present rise in atmospheric CO2 levels causes significant changes in surface ocean pH and carbonate chemistry. Such changes have been shown to slow down calcification in corals and coralline macroalgae, but the majority of marine calcification occurs in planktonic organisms. Here we report reduced calcite production at increased CO2 concentrations in monospecific cultures of two dominant marine calcifying phytoplankton species, the coccolithophorids Emiliania huxleyi and Gephyrocapsa oceanica. This was accompanied by an increased proportion of malformed coccoliths and incomplete coccospheres. Diminished calcification led to a reduction in the ratio of calcite precipitation to organic matter production. Similar results were obtained in incubations of natural plankton assemblages from the north Pacific ocean when exposed to experimentally elevated CO2 levels. We suggest that the progressive increase in atmospheric CO2 concentrations may therefore slow down the production of calcium carbonate in the surface ocean. As the process of calcification releases CO2 to the atmosphere, the response observed here could potentially act as a negative feedback on atmospheric CO2 levels.     

非航海类轮机工程专业实践教学改革的探讨

轮机模拟器训练是轮机工程专业实践教学的重要环节,在详细分析非航海类轮机工程专业教学特点和现状的基础上,提出了整合教学内容、改进教学方法与手段的措施,以提高非航海类轮机工程专业学生理论知识应用及工程实践的能力和培养他们的创新精神.     

Novel pathway for assimilation of dimethylsulphoniopropionate widespread in marine bacteria

Dimethylsulphoniopropionate (DMSP) accounts for up to 10% of carbon fixed by marine phytoplankton in ocean surface waters, producing an estimated 11.7-103?Tmol S per year, most of which is processed by marine bacteria through the demethylation/demethiolation pathway. This pathway releases methanethiol (MeSH) instead of the climatically active gas dimethylsulphide (DMS) and enables marine microorganisms to assimilate the reduced sulphur. Despite recognition of this critical microbial transformation for over two decades, the biochemical pathway and enzymes responsible have remained unidentified. Here we show that three new enzymes related to fatty acid β-oxidation constitute the pathway that assimilates methylmercaptopropionate (MMPA), the first product of DMSP demethylation/demethiolation, and that two previously unknown coenzyme A (CoA) derivatives, 3-methylmercaptopropionyl-CoA (MMPA-CoA) and methylthioacryloyl-CoA (MTA-CoA), are formed as novel intermediates. A member of the marine roseobacters, Ruegeria pomeroyi DSS-3, requires the MMPA-CoA pathway for MMPA assimilation and MeSH production. This pathway and the ability to produce MeSH from MMPA are present in diverse bacteria, and the ubiquitous SAR11 clade bacterium Pelagibacter ubique possesses enzymes for at least the first two steps. Analysis of marine metagenomic data indicates that the pathway is widespread among bacterioplankton in the ocean surface waters, making it one of the most important known routes for acquisition of reduced carbon and sulphur by surface ocean heterotrophs.     

红树林内生真菌2524号中分离的新神经酰胺

红树林内生真菌2524号，采自香港红树Auicennia marina的种子中。从该菌的培养液提取物中分离得到两个新的神经酰胺：[2′，3′-dihydroxytetracosanolyamino]-1,3-dihydroxy-octadecane和[2′，3′-dihydroxydocosanoylami-no]-1,3-dihydroxy-octadecane，化合物的结构通过IR，1D和2DNMR，FAB-MS，ESI-MS^n等实验确定。这两个化合物对肿瘤细胞系Bel-7402，NCI-4460和人体正常细胞系L-02不显示有意义的细胞毒性。     

南海海洋真菌2492号中的甾体成分

对南海海洋真菌2492分离自香港红树林植物Phramites australi，从其菌丝体的乙醇粗提物分离出3个甾体化合物：(22E，24R)—麦角甾—5，7，22—三烯—3β醇；5a，8a—表二氧—(22E，24R)—麦角甾—6，22—二烯—3β醇和(22E，24R)—24—甲基麦角甾—7，22—三烯—3β，5a，6a—三醇。它们的结构通过IR，FABMS和NMR谱图得到确定。     

Novel materials from protein-polymer grafts

Proteins are the most underrated and under-used polymers: their impressive properties include infusibility, great mechanical strength and inherent adhesive capability due to a highly flexible backbone and many functional side chains. The notion of moisture sensitivity of proteins is not universally true. Barnacle cement (which can adhere to Teflon) and mussel and clam byssus, all of which are 99% protein, set in the presence of water and resist enzymatic as well as chemical degradation at ambient temperature. This observation suggests that proteins that are capable of tight three-dimensional cross-linking can overcome sensitivity to moisture and enzymatic attack. It should then be possible to achieve similar resistance by appropriate chemical manipulation of proteins, leading to cross-linking. We have achieved such a result with an ordinary protein, commercially available gelatin, which was chemically modified and then epoxidized. When cured such a material binds to metals and plastics. Any protein that has modifiable amino acids can be used for this purpose.     

海洋真菌Aspergillus flavipes中新神经胺成分

从黄海葵Anthopleura xanthogtammica(Berkly)中分离出海洋附生真菌Aspergillus flavipes,经实验室培养和化学分离纯化,分离得到四种新颖结构的神经酰胺同系物(1-4),它们的化学结构经波谱解析(1R、UV、2D NMR、MS等)和化学降解得以确定.     

海洋烟曲霉菌产壳聚糖酶的酶学性质初探

对海洋烟曲霉菌产壳聚糖酶的酶学性质进行初步研究,在不同温度、不同pH值的反应系统中,考察酶活随温度、pH值的变化情况.在适宜的温度和pH值条件下,向反应体系中添加一定浓度的金属离子,了解金属离子对酶的作用效果.实验结果表明:该酶适宜的催化反应温度为30～35℃、pH值为6.0,当温度为30～35℃时,保持30 min具有一定的热稳定性;金属离子Mn2+对壳聚糖酶具有较大的激活作用.     

海洋微生物生物活性代谢物研究进展及技术问题

近年来,海洋微生物代谢物研究进展迅速。海洋微生物的代谢物种类主要有五大类,即:胺及酰胺类、吲哚生物碱类、乙酰配基类、环肽类及聚丙酸酯类。其生物活性包括:抗菌、抗肿瘤、抗微生物、抗病毒、酶及酶的抑制活性等,其中以抗肿瘤活性最为重要。在培养及鉴定海洋微生物等方面还面临许多问题。     

试论"乡土小说"向"农村小说"的转换

20世纪前期的“乡土小说”与新中国成立后的“农村小说”是有很大区别的。从经济形态之别和基本主题与题材转换，社会关系之别和基本场景与情节转换，价值体系之别和主要人物与主导风格转换这三方面论述“乡土小说”向“农村小说”转换的历程。     

Biochemistry: a cadmium enzyme from a marine diatom

The ocean biota contains a vast reservoir of genomic diversity. Here we present the sequence and preliminary characterization of a protein that is a cadmium-containing carbonic anhydrase from the marine diatom Thalassiosira weissflogii. The existence of a cadmium enzyme in marine phytoplankton may indicate that there is a unique selection pressure for metalloenzymes in the marine environment, and our discovery provides a long-awaited explanation for the nutrient-like behaviour of cadmium in the oceans.     

中国海上船舶垃圾管理策略

介绍海上垃圾污染情况,阐述中国关于船舶垃圾污染防治的管理程序及采取的应对措施.提出减少及根除污染物排放的建议.