Study of the saltwater pond at Capoterra,southern Sardinia: General characteristics

Capoterra Pond in southern Sardinia is described and analyzed with respect to its morphological, meteorological, physical and chemical characteristics, and its zoobenthic, zooplankton, and phytoplankton biocenoses. The birdlife, flora, and riparian associations of vegetation are studied in order to draw international attention to the importance of this lagoon, the precariousness of its ecosystem, the seriousness of current attempts to destabilize it, and the need to encourage the Sardinian authorities to initiate conservation measures, especially as rare birds have found their niches there.     

滦河流域浮游生物与底栖动物分布特征调查研究

基于2010年7月、10月两次对滦河流域的上游高原、中游山区以及下游平原河段21个典型断面水生生物调查,并采用Shannon-Wiener多样性指数、Pielou群落均匀度指数和Simpon指数对各区域的浮游生物与底栖动物的群落组成、生物多样性以及空间异质性进行生物多样性评价。结果表明:滦河流域浮游植物的优势种整体上以绿藻门和硅藻门为主,浮游动物以轮虫和桡足类为主要类群,底栖动物的主要类群为水生昆虫和软体动物;滦河流域浮游植物生态群落结构较稳定;浮游动物生态群落结构较不稳定;底栖动物种类以摇蚊科居多,生态结构较单一;滦河流域的水生生物类群组成及分布与水流、泥沙、水质等河流水文特征及河床底质类型密切相关,并可在一定程度上反映河流水环境状况。     

Comparison of zooplankton community of different areas in Changjiang River estuary北大核心CSCD

To compare the zooplankton communities in the South Branch, North Branch, North Channel and offshore of the Changjiang (Yangtze River) estuary, two cruises were carried out in the autumn of 2009 and the spring of 2010. A total of 27 species of zooplankton were identified in the spring, including 17 in the offshore, 11 in the south branch, 9 in the north branch, and only 5 in the North Channel. In autumn, altogether 71 species were collected, including 6 in the south branch, 11 in the north branch, 8 species in the North Channel area and 63 in the offshore. Either in the spring or autumn, the average species numbers of the offshore were the highest. Additionally, species numbers of the offshore were significantly higher than that in other areas (P < 0.05) for both seasons. There were no significant differences between the species number of the South Branch and the North Branch (P > 0.05). The species number and diversity index of the inner area were lower than that of the offshore. The average diversity index of offshore area was still the highest in both spring (1.69) and autumn (3.73). In spring, the diversity index of the North Channel was the lowest among four areas, while in autumn, that of the South Branch was the lowest (0.49). In spring, Sinocalanus sinensis was the dominant species of the South Branch, North'Branch and North Channel (> 50% of the total collection by number). The dominant species of offshore area were Tortanus vermiculus and Labidocera euchaeta. While in autumn, the dominant species were different for each area. In the South Branch, the most important species was S. dorrii (93.55% of the total collection by number). The main species was S. dorrii in the South Branch area, S. stenellus and T. vermiculusin in the North Branch and Subeucalanus subcrassus in the offshore (< 30% of the total collection by number). Numbers of species and diversity index seemed to vary among different areas of Changjiang estuary. The underline mechanisms of the regional variation in species number were mainly the salinity and suspended sediment concentrations. Generally speaking, zooplankton was more abundant in the polyhaline water. Diversity index was largely affected by both species number and abundance percentage. The zooplankton community was mainly influenced by the Changjiang diluted water and offshore water mass through affecting the salinity. In autumn, the Kuroshio flowed northward carrying polyhaline water, and brought subtropical species to the offshore of the Changjiang estuary. Since the North Channel is located in the estuarine turbidity zone, suspended sediment concentration of that area is higher than the other areas, which might limit the distribution of some species. To sum up, salinity is the most important factor causing the difference of zooplankton community among different areas in the Changjiang estuary. Besides, water masses and estuarine turbidity also influence the zooplankton community.     

Changes in life histories of cladocerans (Cladocera) from the rotifer-mediated allelochemicals

ABSTRACT

We hypothesised that at higher densities herbivorous rotifers through their allelochemicals affect the survival and reproduction of cladocerans. To test this, we separately cultured three rotifers (Brachionus calyciflorus, Brachionus havanaensis, and Plationus patulus) and three cladocerans (Ceriodaphnia dubia, Daphnia pulex, and Moina macrocopa). Chlorella vulgaris was used as food and reconstituted moderately hard water was used as medium. The conditioned-medium (CM) obtained from each of rotifer species was used to conduct cohort life table tests of cladocerans. SDS PAGE electrophoresis revealed the molecular weights of proteins present in the rotifer conditioned medium were 55–63?kDa. Compared to C. dubia and D. pulex, Moina was more resistant to rotifer-mediated chemicals. Gross reproductive rate of C. dubia was significantly stimulated by the rotifer-CM. However, gross and net reproductive rates of D. pulex were strongly reduced (72–85%) due to P. patulus-CM but not from the other two rotifer species. The rate of population increase of M. macrocopa was significantly reduced by the rotifer CM. Overall, about 46% (adverse effect: 24%; stimulatory impact: 22%) of the life history variables in controls significantly differed from rotifer-CM treatments, thus proving our hypothesis that rotifer-mediated allelochemicals had some effect on the cladoceran life history variables.     

The influence of hydrodynamic processes on zooplankton transport and distributions in the North Western Mediterranean: Estimates from a Lagrangian model

A Lagrangian module has been developed and coupled with the 3D circulation model Symphonie to study the influence of hydrodynamic processes on zooplankton transport and distributions in the North Western Mediterranean (NWM). Individuals are released every 3 days from March to August 2001 in two initial areas: around the DYFAMED sampling station in the central Ligurian Sea and in the Rhône river plume. Then the individuals are tracked for 40 days either as passive particles or with a simple diel vertical migration (DVM) pattern. The simulations suggest strong seasonal patterns in the distributions of the individuals released around the DYFAMED sampling station. Individuals spread all over the NWM basin after 40 days but different patterns occur depending on the season, the initial depths of release and the capacity of DVM. Offshore-shelf transport only occurs in April and May with particles ending up in the Gulf of Lions (GoL) in low concentrations. In other months, the Northern Current (NC) can be considered as a barrier for particles entering the GoL from the offshore sea. A quarter to a half of passive individuals released in the Rhône river plume remain in the GoL. The rest is transported by the NC towards the Catalan Sea. Applying a simple DVM scheme does not increase the retention of particles on the shelf.     

Effects of buoyancy, transparency and zooplankton feeding on surface maxima and deep maxima: Comprehensive mathematical model for vertical distribution in cyanobacterial biomass

Inhomogeneous vertical distributions of the cyanobacterial biomass are widely observed during the summer season in stratified lake ecosystems. Among these are surface maxima characterized by surface scum formation and deep or subsurface maxima also known as deep chlorophyll maxima (DCM). The former occurs at the epilimnion in eutrophic lakes, and are usually caused by colonial cyanobacteria such as Microcystis. On the other hand, the latter occurs at the metalimnion and the upper part of the hypolimnion near the thermocline in oligotrophic lakes, and are referred to filamentous cyanobacteria such as Oscillatoria. The aim of this paper is to present a simple mathematical model that can simultaneously describe these phenomena including the annual and diurnal variations, emphasizing the roles of buoyancy regulation, transparency of the lake and zooplankton feeding on cyanobacteria. According to our computer analyses, the increased buoyancy, the low clarity of the lake and the low rate of zooplankton feeding take significant roles in formation of surface maxima, while the reversal of these factors makes deep maxima predominant. Our two-component model with nutrients and cyanobacteria can distinguish between two phenomena by changing the parameters for these factors, without altering the model itself.     

疏浚后杭州西湖富营养化评价

以综合营养状态指数(TLIc)法评价疏浚前后杭州西湖(Ⅰ~Ⅳ站)的富营养化水平,并与水体浮游动物生物量指标做相关分析。结果表明,Ⅰ站和Ⅳ站综合营养状态指数年平均值下降幅度较大,Ⅱ站和Ⅲ站TLIc年平均值下降幅度较小。疏浚促进了西湖中有机物的氧化分解,降低水体中高锰酸盐指数,抑制底泥中磷的释放。湖水TLIc值随浮游动物生物量升高而显著增大,并以轮虫生物量与TLIc值之间的正相关性最稳定。     

卧龙湖浮游动物丰度的季节变化及其与水环境因子的关系

为给卧龙湖(国家良好湖泊生态环境保护试点)生态保护工作提供依据,文章于2014年5~10月对卧龙湖的浮游动物群落结构和不同水环境因子开展了监测,以期明确两者之间的关系。结果表明:研究区浮游动物丰度高,均值达到128.2×10~3 ind/L,浮游动物丰度季节差异显著(P<0.05),夏季(196.2×10~3 ind/L)>春季(154.0×10~3 ind/L)>秋季(25.1×10~3 ind/L);通过克里格插值分析,发现研究区浮游动物季节分布的空间异质性高,春季浮游动物丰度呈现从湖岸带到湖心递减趋势,南部是浮游动物的主要聚集区,而在夏秋季节,浮游动物丰度的高值区域逐渐向东北湖区偏移;通过典范对应分析,研究区内浮游动物分布主要受浊度、温度、营养物质和污染物等因素的影响,同时夏秋季节浮游动物丰度的高值区域逐渐向东北湖区偏移可能与城北明渠在湖区东北部汇入有关。     

大港发电厂温排水对附近海域浮游动物影响研究

分别于2010年夏、冬季对大港发电厂温排水口附近海域浮游动物进行调查。结果表明:调查区浮游动物以桡足类和幼虫类占优势,群落结构相对稳定,但丰度明显低于渤海湾其他海区,种类组成、丰度和多样性指数具有夏季高于冬季、近岸低于远岸的时空变化特征。临近温排水口的TJHS1117站位的浮游动物群落物种数、丰度及多样性等在6个调查站位中都处于最低,可见温排水对浮游动物群落结构及平面分布有一定的影响。