绿藻浓度荧光检测系统的研究

绿藻的过度繁殖是造成水华现象的主要原因,如何做好绿藻浓度的检测是目前的重要工作。基于绿藻中叶绿素-a分子的荧光光谱特性,设计了一种检测绿藻浓度的装置,分析了该检测方法的基本原理,阐述了该装置的结构和测试过程。通过实验与数据分析,结果表明:系统设计合理实用,测量精度为0.02μg/L。绿藻浓度与荧光比值成明显线性关系,线性相关系数为0.998 7;应用对数式除法电路后的激发光强与荧光比值的线性效果良好。

Effects of CO_2 Enrichment on Microstructure and Ultrastructure of Two Species of Freshwater Green Algae

order to investigate the morphological response of freshwater green algae to elevated CO2 concentration, Chlamydomonas reinhardtii Dang and Scenedesmus obliquus Kutz were cultured with enriched CO2, and their microstructure and ultrastructure were examined by microscopy and electron microscopy. The effect of CO2 enrichment to 186 mumol/L, was insignificant on the shape and size of C. reinhardtii, but significant in reducing the volume of S. obliquus. High-CO2 increased the amount of chloroplast. The pyrenoids occurred in low-CO2-grown cells but not in high-CO2-grown ones and more starch granules were observed in the former.

Oxidative stress responses of submerged macrophyte Vallisneria asiatica to different concentrations of cyanobacteria

In a 10-day aquarium experiment, this investigation examines macrophyte restoration in eutrophic Lake Taihu, the physiological effects of different plant biomass levels and of increasing natural cyanobacterial concentrations on a submerged macrophyte, Vallisneria asiatica. Cyanobacterial stress suppressed the superoxide dismutase （SOD） activity of the plant＇s leaves and induced the catalase （CAT） and peroxidase （POD） activities of its roots. The soluble protein content in V. asiatica decreased with an increase in natural cyanobacterial concentrations, whereas the malonaldehyde （MDA） increased significantly at chlorophyll a （Chl a） concentrations of 222 and 262 μg/L in water. V. asiatica adapted to the stress caused by cyanobacterial concentrations by adjusting its antioxidant defense system to remove the excessive reactive oxygen species when the algal Chl a concentration was 〉109 μg/L. Additionally, high biomass of V. asiatica （2 222 g FW/m^2） can inhibit the reproduction of cyanobacteria more significantly than low biomass （1 111 g FW/m^2）. High biomass of V. asiatica increased the oxidative stress in an individual plant when the initial Chl a concentration in the water reached 222 and 262 μg/L, as expressed by the increased MDA in leaves, compared with low biomass of K asiatica. This provides a basis for controlling cyanobacterial concentrations and V. asiatica biomass for the recovery of V. asiatica in eutrophic Lake Taihu.

Seasonal Changes in Phytoplankton Biomass and Dominant Species in the Changjiang River Estuary and Adjacent Seas:General Trends Based on Field Survey Data 1959-2009

The characteristics of seasonal variation in phytoplankton biomass and dominant species in the Changjiang River Estuary and adjacent seas were discussed based on field investigation data from 1959 to 2009. The field data from 1981 to 2004 showed that the Chlorophyll-a concentration in surface seawater was between 0.4 and 8.5 ktg dm-3. The seasonal changes generally presented a bimodal trend, with the biomass peaks occurring in May and August, and Chlorophyll-a concentration was the lowest in winter. Seasonal biomass changes were mainly controlled by temperature and nutrient levels. From the end of autumn to the next early spring, phytoplankton biomass was mainly influenced by temperature, and in other seasons, nutrient level （including the nutrient supply from the terrestrial runoffs） was the major influence factor. Field investigation data from 1959 to 2009 demonstrated that dia- toms were the main phytoplankton in this area, and Skeletonerna costatum, Pseudo-nitzschia pungens, Coscinodiscus oculus-iridis, Thalassinoema nitzschioides, Paralia sulcata, Chaetoceros lorenzianus, Chaetoceros curvisetus, and Prorocentrum donghaiense Lu were common dominant species. The seasonal variations in major dominant phytoplankton species presented the following trends： 1） Skeletonema （mainly S. costatum） was dominant throughout the year; and 2） seasonal succession trends were Coscinodiscus （spring） →Chaetoceros （summer and autumn） → Coscinodiscus （winter）. The annual dominance of S. costatum was attributed to its environmental eurytopicity and long standing time in surface waters. The seasonal succession of Coscinodiscus and Chaetoceros was associated with the seasonal variation in water stability and nutrient level in this area. On the other hand, long-term field data also indicated obvious interannual variation of phytoplankton biomass and community structure in the Changjiang River Estuary and adjacent seas： average annual phytoplankton biomass and dinoflagellate proportion both presented increased trends during the 1950s - 2000s.

Periphyton response to nitrogen and phosphorus enrichment in a eutrophic shallow aquatic ecosystem

We examined changes in biomass and species dominance of periphyton in response to nitrogen (N) and phosphorus (P) enrichment in 12 mesocosms representing eutrophic aquatic ecosystems. The 100-L mesocosms consisted of lake water and pond sediment, and N and P were applied weekly. Periphyton samples were taken to assess the biomass (as estimated by the concentration of chlorophyll a (chl a)) and to determine which species were dominant. The mean periphyton biomass (chl a) in the P-enriched treatment did not differ from that in the control group, but increased with N enrichment. Compared with that in the control group, the chl a concentration increased with N+P enrichment in the early stages of the experiment, but decreased in the later stages. The decline in periphyton biomass at the later stages of the experiment was due to limited light availability, which resulted from the increased phytoplankton density in the experiment. The nutrient enrichment treatments resulted in changes in the dominant algal species in the periphyton, suggesting that various algal species showed different responses to different nutrients. The results of this study have implications for nutrient management in aquatic ecosystems.

Photosynthetic responses of thalli and isolated protoplasts of Bryopsis hypnoides(Bryopsidales,Chlorophyta)during dehydration

Bryopsis kypnoides Lamouroux is a unique intertidal siphonous green alga whose extruded protoplasm can aggregate spontaneously in seawater to form numerous new cells that can develop into mature algal thalli. In this study, the photosynthetic responses during dehydration of both the thalli and protoplasts isolated from B. kypnoides were measured using a Dual-PAM （pulse amplitude modulation）-100 fluorometer. The results show that the photosynthetic rates of B. kypnoides thalli were maintained for an initial period, beyond which continued desiccation resulted in reduced rates of PSI and PSII. However, the photosynthetic performances of the isolated protoplasts dehydrated in air （CO2 concentration 600-700 mg/L） showed a slight increase of Y（II） at 20% water loss, but the rates decreased thereafter with declining water content. When protoplasts were dehydrated in CO2 deficient conditions （CO2 concentration 40-80 mg/L）, the values of Y（II） declined steadily with increased dehydration without an initial rise. These results indicated that the thalli and isolated protoplasts of this alga can utilize CO2 in ambient air effectively, and the photosynthetic performances of the isolated protoplasts were significantly different from that of the thalli during dehydration. Thus the protoplasts may be an excellent system for the study of stress tolerance.

Optical Fiber Fluorometer for Algae Detection and Mapping

A simple instrument for the real-time measurement of algae concentration and mapping is described. The instrument uses a pulsed short arc xenon flashlamp as the excited light sources. Both the exciting light and the fluorescence from algae chlorophyll are transmitted along a fiber bundle. The measurement sensitivity is analyzed and the experiment result is given. The instrument is practical to in-situ measurement at sea.

The Inhibition Effects of Alkoxyl Thiourea Derivatives toward the Growth of Isolated Oscillatoria sp. from Kenyir Lake, Terengganu

In controlling eutrophication phenomenon, there were conventional methods which lead to negative effects to aquatic environment. This study was aimed to investigate the usage of synthesized thiourea compounds to inhibit the growth of Oscillatoria sp. in Kenyir lake, Terengganu, Malaysia. The inhibition effects of four eco-friendly alkoxyl thiourea derivatives compounds named as N-（（4-（decyloxy）phenyl）carbamothioyl）-4-methyl benzamide, N-（（4-（decyloxy）phenyl）carbamothioyl）-4-nitro benzamide, 4-chloro-N-（（4-（decyloxy）phenyl）carbamothioyl） benzamide and N-（（4-（decyloxy）phenyl）carbamothioyl） benzamide were examined onto the growth culture of Oscillatoria sp. These compounds were tested in 30 mL of Oscillatoria sp. cultures with different concentration of 16 μg·mL-1, 18 μg·mL-1, 20 μg·mL-1, 24 μg·mL-1 and 28 μg·mL-1respectively. The treatment flasks were supplied with an aerator for 24 hours under continuous illumination at 25 ℃. Chlorophyll-a concentration were extracted to calculate the inhibition percentage of each treatment. Overall, all these compounds showed inhibition effects towards the growth of Oscillatoria sp., with the highest inhibition of 37% by N-（（4-（decyloxy）phenyl）carbamothioyl）-4-methyl benzamide at the concentration of 18μg·mL-1. The methyl group that attach to the synthesized compound may contribute to the effectiveness of the compound which act as an algae inhibitor. However, extensive studies still need to be conducted in order to investigate the mechanism on how this compound reacts with Oscillatoria sp..