Variability in timing and magnitude of spring bloom in the Oyashio region, the western subarctic Pacific off Hokkaido, Japan

The spring bloom of phytoplankton is a well-established, regular, seasonal event in the western subarctic Pacific and is considered one of the most important conditions of massive production of pelagic fishes. A series of 12 cruises was conducted from 1990 to 1992 to examine the timing and magnitude of the spring phytoplankton bloom in the Oyashio region, the western subarctic Pacific off Hokkaido, Japan. An interannual variability in the bloom events was also analysed. On the basis of hydrographical characteristics, the study area was divided into three water masses: the Oyashio Water Mass, the Mixed Water Mass, and the Coastal Water Mass. Spring blooms were observed first in April in the Oyashio and the Coastal Water Masses, and continued to May in 1991 and 1992. However, no bloom was recorded in the Mixed Water Mass. High nutrient supply into the surface mixed layer during winter is likely to be one of the factors supporting an intense spring bloom in the Oyashio Water Mass. A significant positive relationship between log-transformed surface chlorophyll a concentration and maximum density gradient (MDG) within the euphotic layer was obtained in April, indicating the importance of vertical stability of the water column in the initiation of spring blooms in the Oyashio and the Coastal Water Masses. The spring blooms in 1991 were much more extensive and lasted longer than in 1990. It is suggested that meteorological conditions and abundance of grazers were responsible for this interannual difference.     

棉花盛花期不同类型叶对产量的影响

通过对棉花盛花期不同类型叶和产量关系的研究，结果表明：主茎叶对棉铃的空间分布有较大的影响；主茎叶和果枝叶对棉花植株下部棉铃的铃重也有影响；果枝叶和叶枝叶则在棉花成熟期方面有贡献作用；在影响产量的其他因素上，不同类型叶的作用相当。     

New trophic biomarkers for Collembola reared on algal diets

We used fatty acid (FA) analysis to investigate green algae and cyanobacteria as food sources for Collembola. We studied the effects of food quality on body mass and on neutral lipid (NLFA) and phospholipid (PLFA) fatty acid patterns of Collembola. Folsomia candida, Heteromurus nitidus and Protaphorura fimata were fed with common green algae (Chlorella vulgaris), filamentous soil algae (Klebsormidium flaccidum), cyanobacteria (Nostoc commune) and baker's yeast (Saccharomyces cerevisiae). Body mass of F. candida and H. nitidus was highest when reared on C. vulgaris and S. cerevisiae. P. fimata gained the most weight when fed baker's yeast. K. flaccidum and N. commune as resources resulted to low biomass in all Collembola. The four diets caused significant differences in the NLFA and PLFA composition of Collembola after six weeks of feeding. Two new trophic biomarker FAs indicating algal diets were assigned with 16:3ω3,6,9 and 16:2ω6,9, which were only present in NLFAs of Collembola consuming C. vulgaris and K. flaccidum. The amount of FAs from the ω7 family was high in Collembola lipids with cyanobacteria and yeast as food sources, whereas only trace amounts occurred in the NLFA fraction with algae as the resource. In summary, common soil algae and cyanobacteria differed in food quality for Collembola, depending on their growth form (unicellular versus filamentous) and/or secondary metabolites (e.g. cyanobacteria). The new FA biomarkers detected will allow further investigation of these trophic interactions under field conditions; for example, assessing the role of collembolan grazers in the formation of biological soil crusts.     

胶州湾浮动弯角藻赤潮生消动态过程及其成因分析

分析了1999年6月8日-15日胶州湾东北养殖消耗域浮动弯角藻赤潮生消动态过程中各环境因子的变化及赤潮成因，结果表明，该海域无机营养盐含量较高，为赤潮的发生提供了必需的营养物质；赤潮发生前天气闷热无雨，有利于浮动弯角藻的快速生长繁殖；赤潮形成至发展期该海域盛行南风，浮动弯角藻的物理性聚集对赤潮迅速形成有重要影响；赤潮维持阶段天气稳定，赤潮持续时间较长；最终无机磷、活性硅酸盐的耗尽使赤潮逐步走向消亡。     

基于ASAR和MODIS遥感数据的蓝藻水华提取

将同期的ENVISAT ASAR图像和MODIS图像进行配准,利用经过大气校正后的MODIS光学图像,根据分类决策树对图像EVI进行分类,借此对太湖的藻华和非藻华区域进行划分,并以此为据在ASAR图像上研究两者的V/V后向散射特性,使用阈值法对藻华范围进行提取,并将结果与MODIS图像上得到的藻华范围进行对比。结果表明,通过ASAR图像与MODIS图像得到的藻华范围较好地吻合,由此说明,在一定条件下,ASAR图像可以显示出藻华。最后从机理上探讨了风速对藻华成像的影响,分析了光学和微波图像提取藻华范围不完全一致的原因以及利用微波数据监测藻华的局限性。     

三峡库区香溪河支流放流滤食性鱼类后理化特征的比较研究

从2010年4月至2012年12月对香溪河支流7批次放流滤食性鱼类苗种1 468万尾,对放流前与放流后的水域理化因子特征进行常规监测.结果显示,放流滤食性鱼种后总氮(TN)、氨氮(NH4-N)、亚硝酸盐氮(NO2-N)、硝酸盐氮(NO3-N)、总磷(TP)、正磷酸盐磷(PO4-P)、化学耗氧量(COD)、叶绿素a要明显低于放流前,投放苗种前平均值分别为3.10 mg/L、0.421 mg/L、0.048 mg/L、2.869 mg/L、0.549 mg/L、0.299 mg/L、16.563 mg/L、26.447 mg/m3;放流鱼种后平均值分别为2.20 mg/L、0.065 mg/L、0.022 mg/L、1.643 mg/L、0.495 mg/L、0.155 mg/L、10.465 mg/L、6.608 mg/m3.放流前支流营养化TLI为67.0、放流后为56.4,香溪河支流水域呈轻度富营养化(TLI＞53).为生态修复调控水华发生建议香溪河支流水域每年放流滤食性鱼类苗种.     

Phosphorus Forms in Overland Flow from Agricultural Soils Representative of Mediterranean Areas

Abstract

Phosphorus (P) losses through overland flow (surface runoff) may contribute to eutrophication of water bodies. The main purpose of this work was to study P forms in overland flow (dissolved and particulate) to identify which can be potentially used by algae. To this end, rainfall on 17 representative soils from Mediterranean areas was simulated, and P forms in overland flow studied by chemical and sink (resin, iron oxide–impregnated paper strip) extraction; sequential chemical fractionation of the suspended sediments was also used to establish “operational pools” with a differential capacity of P release. Total P (TP) in runoff ranged from 0.089 to 0.765 mg L^?1 and was mainly related to suspended sediment (particulate P, 86% of TP on average). Iron oxide strip P, which is taken to be an estimate of algal‐available P, accounted for 34% of TP on average in runoff samples; most of the P extracted by this sink was particulate P (68%). In most cases, FeO strip P was equivalent to dissolved reactive P (DRP) plus P extracted by NaOH and citrate‐bicarbonate in suspended sediment (the more labile P fractions) (Y=X, R²=0.82; P<0.001; n=15). One can thus assume that Fe oxide extracts DRP, adsorbed P on sediments, and P related to highly soluble precipitated Ca phosphates, but it does not extract releasable P through reduction of sorbent surfaces or the organic P that can be mineralized in the bottom of water reservoirs, which must be taken in account to estimate the long‐term algal‐available P in runoff.     

Release of nutrient from fish food and effects on Microcystis aeruginosa growth

This study aimed to explore the relationship between Microcystis aeruginosa growth and nutrients released from fish food, which mainly simulates the effect of uneaten food on algae growth and water quality variables during aquaculture activities. Fish food (0, 0.1, 0.2, 0.5 and 1 g dosages tested) of different grain sizes (original; 0.147 ≤ d ≤ 0.85 mm; d ≤ 0.147 mm) was added each into M‐II culturing medium (nitrogen and phosphorus absent). During the experimental running period, the concentrations of total phosphorus (TP), orthophosphate phosphorus (PO₄^3?‐P), total nitrogen and ammonia‐nitrogen (NH₄⁺‐N) increased significantly with increasing fish food dosages regardless of their grain sizes. Furthermore, grain size had a negligible effect on nutrient release from fish food with the same dosage. Based on the above experiment, M. aeruginosa was introduced into the culturing media at different dosages (nitrogen and phosphorus absent) with 0, 0.05, 0.1, 0.2 and 0.5 g fish food to assess algae growth characteristics. Algae cell density significantly increased with the dosage ranging from 0 to 0.2 g. NH₄⁺‐N and PO₄^3?‐P were the main fractions of available nutrients used by M. aeruginosa in the fish food. In comparison to the growth dynamics of algae in M‐II culturing medium, the lag phase for M. aeruginosa in the presence of fish food extended significantly when calculating the time from the addition of fish food and insignificantly when the time for nutrient release from fish food was excluded.     

巢湖蓝藻水华时空分布特征遥感监测研究

利用HJ1A/1B-CCD数据,采用比值植被指数蓝藻水华识别方法分别提取巢湖2009、2010年各个月份的蓝藻水华,着重分析巢湖蓝藻水华时空分布特征。结果表明：巢湖蓝藻暴发一般从5、6月开始,到9月达到最大,10月下旬开始减少,11月基本消亡;蓝藻富集形成水华具有短周期的特点;由于受风力、环湖径流的影响,蓝藻暴发区域为西半湖西北部和正北部以及东半湖西北部和正西部;蓝藻核心暴发区域为巢湖西北部。     

蓝藻水华暴发与水体细菌关系的研究进展

近年来随着高密度集约化养殖的迅猛发展,营养物质的高投入导致了养殖水体自身污染严重,使得蓝藻频繁爆发,不仅严重破坏水体生态系统结构而且产生毒素威胁人类健康。蓝藻又称蓝细菌(Cyanobacteria),是一类能进行产氧性光合作用的大型原核微生物,其细胞结构和代谢机理与真核藻类截然不同。了解富营养化水体的细菌群落结构及其演替规律是研究蓝藻水华形成机理的核心。