Modelling the influence of thermal discharge under wind on algae

Wind-driven processes exert an important impact on aquatic ecosystems, especially on shallow reservoirs. Flow and heat transport under wind in the Douhe reservoir in China were simulated by a two-dimensional mathematical model. Areas corresponding to different temperature rises were calculated for different wind speed conditions with high frequency. It is shown that high temperature rise areas increase for maximum wind speed conditions while low temperature rise areas keep constant for various wind speed conditions. The concentration of Chl.a decreases with the increase of wind speed, indicating that low wind speed is suitable for algae blooming in the Douhe reservoir. The effects of wind on Bacillariophyta biomass growth become more obvious with the increase of temperature rise areas. The influenced areas of lower temperature rise (0.2–1.49 °C) and higher temperature rise (1.5–2 °C) zone are 8.57 × 10⁶ m² and 5.18 × 10⁶ m², respectively, and corresponding total variation amounts of Bacillariophyta biomass are 2.24 × 10⁵/m² and 0.42 × 10⁵/m², respectively. Results show that wind has a significant impact on ecological effects due to thermal discharge from thermal power plant into shallow reservoirs.     

Reconnaissance studies of the tufa deposits of the Napier Range,N.W. Australia

Tufas are widespread in the Napier Range of north Western Australia, an area of tropical seasonal climate and savanna vegetation. The major tufa deposits have been mapped and the different forms described. These include drapes on cliffs, cones at cave entrances or the mouths of ephemeral streams, rimstone pools, and tufa dams. There are at least two generations of tufa cone, with the older being heavily calcreted and eroded. Simple geochemical and petrographical data allow comparison between the different types of deposit here and with deposits from other parts of the world. Thin section observations and scanning electron microscopy enable an initial assessment of the role of organic processes in tufa formation. Obvious organic remains are sparse, although many of the active tufas are composed of filamentous microsparite fabrics, suggesting that algae have influenced the geometry of the deposits. However, the identification of various endolithic algae indicates that they may also be actively involved in the degradation of the deposits.     

Trace metal dynamics in the water column and pore waters in a temperate tidal system: response to the fate of algae-derived organic matter

Tidal and seasonal behaviour of the redox-sensitive trace metals Mn, Fe, Mo, U, and V have been investigated in the open-water column and shallow pore waters of the backbarrier tidal flats of the island of Spiekeroog (Southern North Sea) in 2002 and 2007. The purpose was to study the response of trace metal cycles on algae blooms, which are assumed to cause significant changes in the redox state of the entire ecosystem. Trace metal data were complemented by measurements of nutrients and enumeration of algae cells in 2007. Generally, Mn and V show a tidal cyclicity in the water column with maximum values during low tide which is most pronounced in summer due to elevated microbial activity in the sediments. Mo and U behave almost conservatively throughout the year with slightly increasing levels towards high tide. Exceptions are observed for both metals after summer algae blooms. Thus, the seasonal behaviour of the trace metals appear to be significantly influenced by productivity in the water column as the occurrence of algae blooms is associated with an intense release of organic matter (e.g. transparent exopolymer particles, TEP) thereby forming larger organic-rich aggregates. Along with elevated temperatures in summer, the deposition of such aggregates favours microbial activity within the surface sediments and release of DOC, nutrients and trace metals (Mn, Mo and V) during the degradation of the aggregates. Additionally, pronounced reducing conditions lead to the reduction of Mn(IV)-oxides and Fe(III)-(oxihydr)oxides, thereby releasing formerly scavenged compounds as V and phosphate. Therefore, pore-water profiles show significant enrichments in trace metals especially from July to September. Finally, the trace metals are released to the open water column via draining pore waters (esp. Mo, Mn, and V) and/or fixed in the sediment as sulphides (Fe, Mo) and bound to organic matter (U). Non-conservative behaviour of Mo in oxygenated seawater, first observed in the investigation area by Dellwig et al. (Geochim Cosmochim Acta 71:2745–2761, 2007a), was shown to be a recurrent phenomenon which is closely coupled to bacterial activity after the breakdown of algae blooms. In addition to the postulated fixation of Mo in oxygen-depleted micro-zones of the aggregates or by freshly formed organic matter, a direct removal of Mo from the water column by reduced sediment surfaces may also play an important role.     

太湖冬季底泥中活体藻类的检测

2002年冬从太湖梅梁湾采集柱状底泥,取三段进行直接镜检和用MA培养基进行光照培养．镜检发现表层(0-3cm)底泥中有多种藻类细胞,中层(10-13cm)底泥的藻类细胞种类明显减少,下层(20-23cm)底泥中没有发现藻类细胞．底泥培养的结果与之有相似的趋势,但得到的活体藻类细胞的种类相应减少．培养3个月后得到在外观和群落结构上与夏季水华相似的群落．结果表明底泥中的微囊藻和小环藻在太湖底泥中具有良好的适应性,占有明显的优势地位,底泥可以作为水华蓝藻的越冬场所和来年水华的种源．     

黑龙江呼兰河湿地藻类植物群落结构及分布特点

2009年5-10月期间对呼兰河湿地8个样点进行了5次藻类植物采样调查,经显微镜观察,共鉴定藻类植物158个分类单位,包括148种10变种,隶属于7门8纲14目23科50属.呼兰河湿地藻类群落组成以硅藻、绿藻为主,藻类植物的细胞密度变化范围在469.55×105-847.35×105 cells/L之间,不同采样点藻类...     

天然胶体对微藻生长的效应

利用错流超滤技术提取天然胶体,研究了胶体的有机碳浓度、粒径和来源对海水小球藻(Chlorellaspp.)、亚心形扁藻(Platymonassubcordiformis)和球等鞭金藻(Isochrysisgalbana)生长的影响。结果表明,当粒径为10kDa—0.2μm、胶体有机碳浓度为4.8—238.4μmol/L时,胶体使小球藻、扁藻和金藻的生长率分别提高了4.0%—7.0%、19.1%—28.9%和2.9%—8.7%。海水小球藻生长率的相对增长百分数(Y)值与胶体有机碳浓度(CCOC)呈线性正相关;亚心形扁藻和球等鞭金藻的Y与CCOC呈多项式相关;胶体对扁藻生长的刺激作用大于球等鞭金藻和海水小球藻。粒径为10kDa—0.2μm的胶体对3种藻的促进作用大于1—10kDa的胶体。河口、河流和生源胶体使小球藻的生长率提高1.5%—14.1%,不同来源的3种胶体对海水小球藻的促进作用依序是河流胶体>生源胶体>河口胶体。以上结果表明,天然胶体含有微藻生长所必需的营养元素,对微藻的生长有显著的刺激作用。     

Fragmentation as a Strategy for Caulerpa Species: Fates of Fragments and Implications for Management of an Invasive Weed

Abstract. The successful growth of fragments to full size macroalgal clones is well known for many taxa in mariculture. From an ecological context, however, few studies relate success by invasive species to the ability to fragment readily, disperse widely or re-attach rapidly - obvious hallmarks of weedy species. This study compares morphologically and ecologically distinct species of the green alga Caulerpa : in the Mediterranean, Caulerpa taxifolia is well known as an invasive weed; Caulerpa prolifera grows around or inside seagrass beds and is not apparently invasive; Caulerpa verticillata is among the most diminutive species, with potentially the most restricted reef distribution. We tested three hypotheses: (i) fragment success is independent of size, (ii) fragment success is independent of position within the plant and (iii) fragments from all species will be equally successful in establishing rhizoids, the first step to re-attachment. The success of small fragments (5–40 mm lengths) cut from distinct locations within replicate plants was scored for survival and establishment of rhizoids in bioassays. Additionally, for C. taxifolia , estimates were made of the force needed to puncture upright and prostrate axes, thereby estimating forces required to generate fragments from these two sources. Among the three species, only upright axes of C. taxifolia readily recovered from fragmentation stress for fragment sizes > 10 mm. The forces required to fragment upright axes were substantially less than for comparable rhizome portions. Fragments of C. prolifera were viable only for rhizome portions; fragments of C. verticillata were not viable at any size examined in this study. Estimates of viable fragment size, origin and force required to fragment axes for C. taxifolia support existing field data suggesting that fragmentation is the effective propagation mechanism underlying the spread of this invasive weed.     

藻华聚集的环境效应:对漂浮植物水葫芦(Eichharnia crassipes)抗氧化酶活性的影响

利用以水葫芦为代表的水生植物进行水体生态治理,具有环保、生态和可持续发展的优点.然而,在外源和内源污染尚未完全控制的情况下,夏季蓝藻水华仍然会频繁暴发.系统研究水生植物对藻华聚集后形成的逆境环境下的生理适应机制可为减轻藻华聚集的不良影响、充分发挥水生植物的水体净化功能发挥重要作用.以水葫芦为代表,采用模拟实验,研究在高温阶段(水温25℃)、水华聚集下对水葫芦关键酶活性的影响及其环境效应,以揭示蓝藻水华聚集后引起的浅水生态系统中水生植物消亡的深层机理.结果表明,藻华聚集会很快消耗掉水生植物根区内的溶解氧,水体呈现缺氧状态(溶解氧0.2 mg/L);植物根区内氧化还原电位值出现明显下降,实验进行1 d后低于-100 m V,实验结束时达-199.9 m V,水体呈现强还原环境.植物叶片中丙二醛(MDA)、超氧化物歧化酶(SOD)、过氧化物酶(POD)含量呈现快速增加的变化趋势,至实验结束时添加120 g/L的处理组中其含量分别为2.17μmol/g(FW)、266.497 U/g、1988.60 U/(g·min),而叶片中过氧化氢酶(CAT)呈现快速下降的趋势,至实验结束时其含量为6.09 U/(g·min);根系中MDA、POD至实验结束时其含量分别为0.57μmol/g(FW)、525.161 U/(g·min),呈现快速下降的趋势;SOD、CAT含量在实验结束时高达221.71 U/g、35.10 U/(g·min),表现为快速增加的趋势.水葫芦关键抗氧化酶活性的变化,表明藻华长期聚集、腐解带来的水体缺氧等不良条件对植物产生了环境胁迫作用,较长时间影响(5 d)下对植物产生了严重的伤害作用;同时也表明藻华严重聚集及藻细胞腐解产生的环境胁迫是漂浮植物水葫芦无法生长乃至死亡的主要影响因素.因此,在利用水生植物进行水体净化的工程实践中,要避免蓝藻的严重堆积,以减轻藻华暴发对植物的不利影响和充分发挥植物的水体净化功能.     

Relationship between valve activity, microalgae concentration in the water and toxin accumulation in the digestive gland of the Pacific oyster Crassostrea gigas exposed to Alexandrium minutum

The complexity of the relationships between Alexandrium minutum (A.m.) concentration in the water ([A.m.]_w), Paralytic Shellfish Poisoning contamination in the digestive gland ([PSP]_dg) and valve behavior was explored in oysters Crassostrea gigas. Two experiments were conducted, during which oysters’ valve behaviour were analyzed. Oysters, first acclimated for 10-days with the non harmful microalgae Heterocapsa triquetra (H.t.), were exposed to four microalgae mixtures at constant total concentrations of 10 × 10³ cells ml⁻¹ (experiment-1) and 5 × 10³ cells ml⁻¹ (experiment-2): 100% A.m.; 50% A.m.-50% H.t.; 25% A.m.-75% H.t.; 100% H.t. At the end of experiment-2, [PSP]_dg were measured.At 10 × 10³ cells ml⁻¹, the microalgal ingestion decreased (p < 0.05) with increasing [A.m.]_w but not at 5 × 10³ cells ml⁻¹ (p > 0.05). The frequency of microclosures specifically increased with [A.m.]_w (p < 0.05) and the opening duration with [PSP]_dg (p < 0.0001). Oysters exhibiting the maximum increase in opening duration also exhibited the highest [PSP]_dg. The results are discussed in terms of oyster physiology and origin of the behavioral response.     

磁化水对亚心形扁藻繁殖的作用

以亚心形扁藻(Platymonas subcordiformis)为材料,研究了磁化水对其繁殖的影响,实验结果表明,磁化水不仅能提高藻细胞每天的分裂频率,而且延长了藻细胞的指数繁殖期和存活时间。