The range expansion patterns of Spartina alterniflora on salt marshes in the Yangtze Estuary,China

The range expansion patterns of Spartina alterniflora and the roles which sexual reproduction and asexual propagation play in range expansion were investigated at the Chongming Dongtan nature reserve in the Yangtze Estuary, China. Two range expansion patterns of S. alterniflora at its advancing fronts could be found (1) S. alterniflora–mudflat front (S–M) and (2) S. alterniflora–Scirpus mariqueter–mudflat front (S–S–M). One feature revealed by this study was that a flush of seedling recruitment and establishment in spring was a crucial way for S. alterniflora to colonize new habitats and achieve a fast rate of range expansion. The mean number of seedlings recruited at the S–M front was much higher than that at the S–S–M front. Once established, the survivorship of seedlings was high, both at the S–M and S–S–M fronts. The established seedlings formed new tussocks quickly by vegetative tillering and growth of rhizomes and these finally merged into dense meadows. The mean distance of range expansion of S. alterniflora, after one growing season at the S–M front, was 25.4 ± 3.1 m yr⁻¹ and 2.7 ± 0.5 m yr⁻¹ at the S–S–M front. Sexual reproduction by seedlings and asexual propagation by tillering and growth of rhizomes were the two main means by which S. alterniflora could maintain a fast rate of range expansion on the salt marshes of the Yangtze Estuary. The colonization behaviors of S. alterniflora on advancing fronts differed as a reaction to various external and internal factors. The impact of abiotic and biotic factors governing the range expansion of S. alterniflora and its implications for the spatial structure of tidal wetlands are discussed.     

Variability in growth,development and reproduction of the non-native seaweed Sargassum muticum (Phaeophyceae) on the Irish west coast

This study compared seasonal growth, development and reproduction of the invasive brown macroalga Sargassum muticum in habitats with different wave exposure on the Irish west coast. Three field sites with different degrees of wave exposure were chosen for monthly observations to reflect different habitats that were characteristic of the Irish west coast. Growth and receptacle development differed considerably between sites. Growth and receptacle development was lower at the most sheltered site. Here, S. muticum showed signs of early fragmentation in April/May during the two years of investigation (2007 and 2008), whilst the population at an exposed site developed normally and plants grew to a maximum average length of 163 cm by July, with the onset of fragmentation in August. Sargassum muticum in a tide pool exhibited a similar seasonal growth cycle as plants at the exposed open shore site. Overall growth however was stunted, with plants reaching a maximum length of only 30–40 cm in July. Receptacle development was also inhibited at the sheltered site, with a maximum of only 10% of plants found to be fertile during spring and summer 2008, while plants at the exposed site and the tide pool exhibited 100% plant fertility by August. An extensive occurrence of the native epiphyte Pylaiella littoralis on S. muticum was noticed during field sampling at the sheltered study site which may have contributed to inhibited development of S. muticum observed in this area.     

坛紫菜生活史的研究现状及存在的问题

坛紫菜（Porphyra haitanensis）属暖温性海藻,是中国东南沿海的重要栽培物种,2011年度栽培面积达30余万亩。其生活史过程比较复杂,既有雌雄异体,也有雌雄同体;既存在无性生殖,也存在有性生殖;其能否产生单孢子也常常引起争议。为此,本文总结了坛紫菜的生殖及生活史的研究现状和存在的问题,旨在为坛紫菜的遗传育种提供一定的理论参考。     

Feeding preferences of estuarine mysids Neomysis integer and Rhopalophthalmus tartessicus in a temperate estuary (Guadalquivir Estuary,SW Spain)

Mysid shrimps are an important component of estuarine food webs because they play a key role in energy transfer as intermediate prey. We investigated the seasonal, tidal and depth specific variation in the diet of the estuarine mysids Neomysis integer and Rhopalophthalmus tartessicus and explored its implications for the planktonic community structure of a temperate estuary (Guadalquivir Estuary, SW Spain). Neomysis integer is an opportunistic omnivore feeding mainly on mesozooplankton and on members of the detrital–microbial loop, shifting prey seasonally according to availability. In contrast, R. tartessicus showed a more carnivorous diet and shifted its target prey during seasons of low resource availability. Despite statistically significant differences in diet composition, both species shared prey of similar size, particularly juvenile Mesopodopsis slabberi, the most abundant mysid species in this estuary, and copepods. Although these similarities imply inter-specific resource competition, their co-existence is achieved by niche partitioning and spatial segregation: the higher osmoregulatory capacity and foraging plasticity of N. integer confers a broader niche breadth for this species allowing N. integer to inhabit the more stressful oligohaline region of the estuary where R. tartessicus cannot survive. We propose that this mechanism relaxes the potential for competition between N. integer and R. tartessicus.     

Deep-water stands of Cystoseira zosteroides C. Agardh (Fucales,Ochrophyta) in the Northwestern Mediterranean: Insights into assemblage structure and population dynamics

Populations dominated by Cystoseira zosteroides, an endemic and threatened Mediterranean seaweed, colonize deep-water rocky habitats down to more than 50 m depth. Assemblages dominated by this species display high algal and invertebrate species richness. Algal biomass averages 1134 g dw m⁻². Erect and turf algae account for only 25% of total algal dry weight, while encrusting corallines are responsible for the remaining 75%. Sponges, bryozoans and ascidians constitute the dominant sessile macrofauna. Cystoseira zosteroides is the dominant erect algae, with a mean biomass of 60.6 g dw m⁻², and densities ranging from 4 to 7 plants m⁻². The alien turf alga Womersleyella setacea has a biomass of 104.2 g dw m⁻² and covers most of the understory substrate. The size-frequency distribution of C. zosteroides populations shows differences over time. Mean annual growth of the main axis is around 0.5 cm and mean annual mortality rate is lower than 2%. Recruitment was almost nil during the studied period of time (10 years). Processes structuring these deep-water Cystoseira stands must be driven by episodic disturbances, after-disturbance recruitment pulses, and long periods of steady growth that last at least 10 years. However, it is also possible that recruitment is irreversibly inhibited by the alien alga W. setacea in which case these old-growth stands are faced with extinction. The highly diversified assemblages and the low growth and low mortality rates of C. zosteroides indicate high vulnerability to natural and anthropogenic disturbances, and call for effective measures to ensure their conservation.     

A cellular automata model for population expansion of Spartina alterniflora at Jiuduansha Shoals,Shanghai, China

Biological invasion has received considerable attention recently because of increasing impacts on local ecosystems. Expansion of Spartina alterniflora, a non-native species, on the intertidal mudflats of Jiuduansha Shoals at the Yangtze River Estuary is a prime example of a spatially-structured invasion in a relatively simple habitat, for which strategic control efforts can be modeled and applied. Here, we developed a Cellular Automata (CA) model, in conjunction with Remote Sensing and Geographical Information Systems, to simulate the expanding process of S. alterniflora for a period of 8 years after being introduced to the new shoals, and to study the interactions between spatial pattern and ecosystem processes for the saltmarsh vegetation. The results showed that the CA model could simulate the population dynamics of S. alterniflora and Phragmites australis on the Jiuduansha Shoals successfully. The results strongly support the hypothesis of space pre-emption as well as range expansion with simple advancing wave fronts for these two species. In the Yangtze River Estuary, the native species P. australis shares the same niche with the exotic species S. alterniflora. However, the range expansion rate of P. australis was much slower than that of S. alterniflora. With the accretion of the Jiuduansha Shoals due to the large quantity of sediments deposited by the Yangtze River, a rapid range expansion of S. alterniflora is predicted to last for a long period into future. This study indicated the potential for this approach to provide valuable insights into population and community ecology of invasive species, which could be very important for wetland biodiversity conservation and resource management in the Yangtze River Estuary and other such impacted areas.     

渤海湾海丰盐场卤虫种群动态及盐度对卤虫种群密度的影响

卤虫是鱼、虾、蟹幼苗极为理想的天然饵料.随着水产育苗发展,卤虫及卤虫卵的需求量在不断增加[1].为了更好地开发、利用和保护卤虫资源,其生态学研究近20a以来受到了明显的重视,但具体研究偏重于实验种群方面,如环境因子(如温度、盐度、饵料等)对卤虫生长、存活、生殖特征(如性成熟速度、生殖方式、生殖力)的影响[2~10],而关于卤虫的自然种群研究较少,原因是进行卤虫的野外生态学研究有诸多困难,如卤虫繁殖速度快且次数多,世代之间有重叠:盐湖或盐池的水文特征经常发生剧烈变化[11,12],故迄今只有Petra[13]和Petra等[14]对Mono湖的Artemiamonica,Gene等[17]对法国Giraud的孤雌生殖卤虫的自然种群进行了系统研究.     

Seasonal variability in somatic and reproductive investment of the bivalve Scrobicularia plana (da Costa, 1778) along a latitudinal gradient

Monthly investment in soma and gonads in the bivalve Scrobicularia plana is described for three populations along its distributional range: Minho estuary, Portugal; Westerschelde estuary, The Netherlands and Buvika estuary, Norway. Seasonal cycles in body mass (BMI), somatic mass (SMI) and gonadal mass (GMI) indices were observed for all populations. In Portugal, BMI and SMI peaked in mid-autumn, while in The Netherlands both indices were at their highest in mid-spring. Norway showed a different pattern with two distinct peaks: one in mid-autumn and a second peak in spring. GMI reached maximum values in July in Portugal and Netherlands and in June in Norway. Overall, mean BMI and SMI were lower in Portugal while mean GMI was lower in Norway. The spawning period lasted the whole summer in Portugal, but was shorter (only two months) in The Netherlands and Norway. The reproductive investment in The Netherlands was significantly higher than in Portugal and Norway, with the lowest values being observed in Norway. Differences in annual cycles between populations were attributed to environmental factors, namely temperature and food availability. Temperature seems important in shaping the reproductive pattern with more northern populations showing shorter reproductive periods starting later in the year, and a lower reproductive output. In addition, winter water temperatures can explain the lower mean body and somatic mass values observed in Portugal. Food availability influenced the physiological performance of the species with peaks in somatic mass coinciding with phytoplankton blooms. This relation between physiological performance and environmental factors influences S. plana distribution, densities and even survival, with natural consequences on its commercial importance.     

Tidal and annual variability of the population structure of Eurytemora affinis in the middle part of the Seine Estuary during 2005

Annual variability in abundance and population structure of the copepod Eurytemora affinis was studied in the maximum turbidity zone of the Seine Estuary in 2005. An Eulerian sampling strategy was applied monthly from March to July and from September to December. Chlorophyll a and suspended particulate matter (SPM) concentration, copepod abundance and stage distribution, and phytoplankton abundance were measured in sub-surface and near-bottom water during the ebb phase. Total E. affinis abundance was at a maximum in March and April (>200 × 10³ ind. m⁻³), and decreased from May to September (<25 × 10³ ind. m⁻³). This decrease corresponds to annual increases in temperature, salinity, chlorophyll a concentration and phytoplankton abundance, which was dominated by large diatoms, and decreases in SPM and river discharge. The phenology observed in 2005 was almost two months earlier compared to previous studies in the 1990s, when E. affinis reached maximum abundance in May and June. The low proportion of nauplii (<50%) in the population and high abundance of ovigerous females suggests that low recruitment is probably related to anomalously low temperatures in late winter (<5 °C). Whatever the horizontal position of the population in the estuary, adult and late copepodid stages are distributed in higher salinity than naupliar stages. Overall E. affinis population abundance was driven by parameters that characterize water masses at the tidal scale and by river discharge and chlorophyll a at the annual scale. By integrating the tidal effect, the high-frequency sampling protocol used appears to be optimal for investigating annual variability of planktonic communities in megatidal estuaries.     

Habitat preferences and life history of the red scorpion fish, Scorpaena notata, in the Mediterranean

Scorpaena notata is a small, sedentary scorpaenid species widely distributed in the Mediterranean and adjacent waters of the Atlantic. In the western Mediterranean it inhabits coastal continental shelf bottoms. In the Balearic Islands, these bottoms are characterised by the presence of the facies with red algae, including both Peyssonnelia and mäerl beds. These beds enhance the structural complexity, biodiversity and secondary production of the soft bottoms. Due to the oceanographic conditions of the Islands, the facies with red algae are especially rich in terms of biomass and algal coverage, and are widespread distributed between 40 and 90 m depth, where trawlers exploiting the continental shelf operate. The present work studies the biology of S. notata and its relationship with habitat characteristics. Special attention is focused on the aspects related to fish condition and growth as a tool to assess the importance of the facies with red algae for fish.     

The application of cutting plus waterlogging to control Spartina alterniflora on saltmarshes in the Yangtze Estuary,China

Control and eradication of the exotic and invasive plant Spartina alterniflora within the Chongming Dongtan nature reserve, Shanghai, China, is vital for the management and conservation of the saltmarshes. A demonstration project was established using waterlogging and cutting to control this invasive species. Results from 2007 to 2008 showed that, although the managed waterlogging significantly reduced biomass and seed production of S. alterniflora at an early stage, the species subsequently showed rapid adaptation to the long-term waterlogging stress. Thus, managed waterlogging alone was insufficient for the effective eradication of S. alterniflora. However, managed waterlogging for around 3 months, combined with cutting the above-ground part of S. alterniflora at a key stage (flowering period in July), controlled and eradicated the plant successfully. Both the above-ground and below-ground parts of S. alterniflora were killed and the plants began to decompose after 3 months. Furthermore, there was no re-growth of the emergent part of S. alterniflora in the following years. However, once the impounded water was released restoring the natural hydrodynamic regime of the saltmarshes, the seeds and seedlings of S. alterniflora reinvaded the controlled site from the neighboring areas and the S. alterniflora community was re-established. Thus, after eradication of S. alterniflora, control measures should be maintained to prevent the re-establishment of S. alterniflora. The results of this demonstration project indicate a potentially useful and effective approach for the control and management of large-scale invasion by S. alterniflora on saltmarshes in the Yangtze Estuary, China.     

Population dynamics of the seagrass Cymodocea nodosa in Ria Formosa lagoon following inlet artificial relocation

The population dynamics of the seagrass Cymodocea nodosa was investigated in three meadows differently affected by the artificial relocation of an inlet in the western sector of the Ria Formosa lagoon, southern Portugal. One meadow was subjected to increasing currents that caused erosion, another one was subjected to an initial episode of burial and a third meadow was undisturbed by the inlet opening. The hydrodynamic/sedimentary condition of meadows was assessed through comparative sediment analysis between the meadow and the adjacent unvegetated area.     

Polycyclic aromatic hydrocarbons in water,mussels (Brachidontes sp., Tagelus sp.) and fish (Odontesthes sp.) from Bahía Blanca Estuary,Argentina

Polycyclic aromatic hydrocarbons (PAHs), one of the major groups of anthropogenic environmental pollutants, were firstly identified and measured in coastal waters, native mussels and fish of an industrialized South American estuary.     

石斑鱼肠道原籍嗜冷杆菌( PsychrobacterSP.)SE6作为益生菌的体内外评价

研究了石斑鱼肠道原籍嗜冷杆菌SE6在体外的抑菌特性及对人工胃肠液的耐受特性,在此基础上研究了饲料中添加SE6(108CFU/g)对斜带石斑鱼生长性能和免疫功能的影响。体外试验结果表明:SE6对副溶血弧菌、哈维氏弧菌、梅氏弧菌和金黄色葡萄球菌等常见水产致病菌均有一定的抑制作用。pH为4.0的人工胃液能促进SE6的生长,处理2和4 h存活率分别为110.7%和173.0%;pH为3.0的人工胃液处理2 h后活菌数为1.59×105 CFU/cm3,存活率为1.36%,但SE6不能耐受pH为2.0的人工胃液。经浓度分别为0.1%,0.3%,0.5%和0.7%的胆盐处理3 h后,SE6的存活率分别为89.17%,88.33%,77.17%和12.33%。动物试验结果显示:投喂SE6 60 d后试验组饵料系数(0.95±0.01)显著低于对照组(1.03±0.02)。试验组血清补体C3在试验全期均高于对照组,补体C4含量在投喂SE6 60 d时显著上升。血清IgM含量在投喂30 d时显著上升。总之,嗜冷杆菌SE6能抑制多种常见病原菌的生长,而且对模拟胃肠道环境具有一定的耐受能力,添加到饲料中能显著提高石斑鱼饵料利用率,增强动物的免疫功能。     

Genetic and morphological description of Eucalanus spinifer T. Scott, 1894 (Calanoida: Eucalanidae), a circumglobal sister species of the copepod E. hyalinus s.s. (Claus, 1866)

A distinct genetic form of the eucalanid calanoid copepod Eucalanus hyalinus s.l. was identified in subtropical and temperate waters of the Pacific, Atlantic, and Indian Oceans. Results from mitochondrial (16S rRNA, COI) and nuclear (ITS2) genetic markers suggest that the two E. hyalinus forms are reproductively isolated. Eucalanus spinifer T. Scott is taken out of synonymy with E. hyalinus and is applied to the smaller of the two genetic forms, increasing the number of species in the genus Eucalanus to a total of six. Adult females of the sister species E. hyalinus s.s. and E. spinifer can be distinguished morphologically by the shape of the anterior portion of the head in lateral and ventral views, asymmetry in the length of antennule segments 22 and 23, length ratios of 22/5 and 23/5 of the longer of the antennules, the length of the caudal rami, and total body size, as measured by total length or prosome length. We illustrate and describe both adult females and males of E. spinifer, and discuss aspects of sexual dimorphism. The sister species are sympatric throughout much of their circumglobal biogeographic distributions, but appear to have centers of abundance in slightly different water mass types.     

Sedimentary iron inputs stimulate seagrass (Posidonia oceanica) population growth in carbonate sediments

The relationship between sedimentary Fe inputs and net seagrass population growth across a range of Posidonia oceanica meadows growing in carbonate Mediterranean sediments (Balearic Islands, Spain; SE Iberian Peninsula, Spain; Limassol, Cyprus; Sounion, Greece) was examined using comparative analysis. Sedimentary Fe inputs were measured using benthic sediment traps and the net population growth of P. oceanica meadows was assessed using direct census of tagged plants. The meadows examined ranged from meadows undergoing a severe decline to expanding meadows (specific net population growth, from −0.14 yr⁻¹ to 0.05 yr⁻¹). Similarly, Fe inputs to the meadows ranged almost an order of magnitude across meadows (8.6–69.1 mg Fe m⁻² d⁻¹). There was a significant, positive relationship between sedimentary iron inputs and seagrass net population growth, accounting for 36% of the variability in population growth across meadows. The relationship obtained suggested that seagrass meadows receiving Fe inputs below 43 mg Fe m⁻² d⁻¹ are vulnerable and in risk of decline, confirming the pivotal role of Fe in the control of growth and the stability of seagrass meadows in carbonate sediments.     

Factors regulating population dynamics of the amphipod Ampithoe valida in a eutrophic subtropical coastal lagoon

Year-round investigations were carried out to address the population dynamics of amphipod Ampithoe valida and its potential regulating factors in the Yundang Lagoon (a eutrophic subtropical coastal lagoon in Xiamen City, China) from October 2007 to October 2008. The results show that A. valida population was largely composed of juveniles and reached a peak abundance (12.02 × 10 3 ind./m2 ) in March, but sharply shrunk in July. The monthly variation pattern of A. valida seemed to follow that of Ulva lactuca which is the main food resource for A. valida, indicating a strong influence of food availability on A. valida population dynamics. Life cycle studies in laboratory indicate that A. valida adopted an r-selected life strategy, e.g., rapid growth rate (0.216-0.302 mm/d), consecutive breeding (4-10 times), short reproductive rhythm (9-17 d) and huge fecundity (24-192 eggs or 6-94 juveniles per brood), which contributed to the fast population growth of A. valida from January to March. Although temperature may also be a significant cause, A. valida could grow quickly and show normal reproductive traits (i.e., the timing of sexual differentiation or maturity, the reproductive rhythm, the number of broods all through its lifespan and offspring production) in temperature between 15-30 C. Therefore, the temperature variation in the lagoon water should not account for the sharp variation of A. valida population by affecting the survival, growth and reproduction of the amphipod. However, negative correlation between water temperature and U. lactuca biomass in the lagoon suggested that temperature could have indirectly affected the population dynamics of A. valida by affecting its food availability. The authors conclude that, in the Yundang Lagoon, the population dynamics of A. valida was mainly controlled by the food availability rather than water temperature.     

Selective uptake of prokaryotic picoplankton by a marine sponge (Callyspongia sp.) within an oligotrophic coastal system

Marine sponges are key players in the transfer of carbon from the pelagic microbial food web into the benthos. Selective uptake of prokaryotic picoplankton (<2 μm) by a demosponge (Callyspongia sp.), and carbon flux through this process, were examined for the first time in the oligotrophic coastal waters of southwestern Australia, where sponge abundance and biodiversity ranks among the highest in the world. Water sampling and flow rate measurements were conducted over five sampling occasions following the InEx method of Yahel et al. (2005), with heterotrophic bacteria and autotrophic Synechococcus cyanobacteria identified and enumerated by flow cytometry. Callyspongia sp. demonstrated high filtration efficiencies, particularly for high DNA (HDNA) bacteria (up to 85.3% in summer 2008) and Synechococcus (up to 91.1% in autumn 2007), however efficiency varied non-uniformly with time and food type (p < 0.01). Overall filtration efficiency for Synechococcus (86.6 ± 6.3%; mean ± s.d.) was always significantly higher (p < 0.05) than for low DNA (LDNA) bacteria (40 ± 17.2%), except during winter 2007 (p = 0.14) when ambient Synechococcus concentrations were lowest. When compared to ambient abundances of the different food types, Callyspongia sp. exhibited consistently negative selectivity for LDNA bacteria and positive selectivity for Synechococcus, while HDNA bacteria was generally a neutral or positive selection. The total carbon removal rate (sum of all prokaryotic picoplankton cells), calculated on a per unit area basis, varied significantly with time (p < 0.01), with lowest rates recorded during the winter (0.5 ± 0.4–0.6 ± 0.8 mg C m⁻² d⁻¹) and highest values recorded in summer (3.5 ± 1.9 mg C m⁻² d⁻¹). These flux estimates quantify the role of a demosponge species in the ultimate fate of prokaryotic picoplankton within the nearshore food webs of southwestern Australia, and support the conclusion that sponges actively select food particles that optimise their nutritional intake.     

九龙江口伪镖水蚤科一新种——沈氏伪镖水蚤

记述了采自九龙江口桡足类1个新种——沈氏伪镖水蚤（Pseudodiaptomus sheni Guo&Wang,sp.nov.）,对其形态特征进行了拍照、绘图和描述。形态上,新种头部钝尖,雌性胸部后侧角内缘乳状突起明显、生殖厣末端突起呈长倒刺状、尾叉外侧第2和第3尾刚毛基部膨大、第5胸足外肢第1节内末角突起尖细,雄性第5胸足左足第2基节后缘中部三角形突起狭尖,与火腿伪镖水蚤[P.poplesia（Shen,1955）]存在显著的形态差异;两者基于线粒体细胞色素氧化酶亚基Ⅰ（mtCOI）基因片段的遗传差异为17.4%~19.5%。沈氏伪镖水蚤的命名旨在纪念中国科学院动物研究所甲壳动物分类学家沈嘉瑞（1902-1975）研究员,模式标本保存于厦门大学海洋科技博物馆。