NaCl胁迫对滨梅扦插苗生物量和水分积累的影响

以1年生滨梅(Prunus maritima Marshall)扦插苗为实验材料,在盆栽条件下用质量浓度为0.15%、0.29%、0.58%、0.88%、1.17%、1.46%的NaCl溶液进行盐胁迫处理,测定胁迫后根、茎、叶Na+、K+含量以及全叶、一年生茎、二年生茎和根系生物量、含水率、根系活力变化,探讨滨梅的抗盐胁迫机制。结果显示:(1)盐胁迫80d后,随着盐胁迫强度提高,滨梅植株根、茎、叶Na+含量显著提高,而其根、茎K+含量显著降低,根、茎、叶K+/Na+值显著降低;根Na+含量在低于0.58%NaCl胁迫下显著高于茎、叶,而在高于0.58%NaCl胁迫下却表现为叶Na+含量显著高于根、茎。(2)滨梅根、茎、叶生物量均随盐胁迫强度的提高呈先增加后减少的趋势;随着盐胁迫时间的延长,茎、叶生物量在低于0.58%NaCl胁迫下均呈积累趋势,且茎生物量在0.58%NaCl胁迫下显著提高,而根、一年生茎、叶生物量在高于0.58%NaCl胁迫下均显著下降。(3)滨梅茎、叶含水率均随盐胁迫强度的增加呈先增加后减少的趋势,而随着胁迫时间的延长呈逐渐减少趋势;根系活力及根含水率均随盐胁迫强度的提高而增加,但根含水率随着胁迫时间的延长变化不明显。由此可见,滨梅能通过根系稀释并蓄积Na+,保护地上部分正常生长,当进入根系的Na+量超过吸收阈值时,Na+迅速在叶中积累储存,且叶中较高含量的K+对Na+形成了有效的缓冲。     

Phytosociological survey of Northern California dunes

ABSTRACT

The vegetation of sandy coasts of California between Point Arena and Morro Bay, was investigated. Near the tide line, was annual vegetation of the Cakile maritima community. Dunal vegetation included the new Abronio latifoliae-Ambrosietea chamissonis class with the new Ambrosietalia chamissonis order and the new Ambrosion chamissonis alliance (proposed). Foredune vegetation included the two new Abronio latifoliae-Elymetum mollis and Atriplici leucophyllae-Abronietum maritimae associations, with the new Polygono paronychiae-Artemisietum pycnocephalae and Erigero glauci-Abronietum latifoliae associations on more stabilised surfaces. In some localities, Ammophila arenaria var. australis occurs within a Lupino variicoloris-Ammophiletum australis association, which colonises the whole dune ecosystem. In the flat areas characterised by grit and affected by frequent sea ingression is an association characterised by Juncus lesueurii and Distichlis spicata (Junco lesueurii-Distichletum spicatae). In the hollows among inland dunes, affected by stagnation, thick meadows develop which contain two new associations: Stachydo rigidae-Iridetum douglasianae developing on flat areas with a stronger stagnation and Achilleo millefoliae-Elymetum pacifici.     

Application of PFGE to source tracking of faecal pollution in coastal recreation area: a case study in Aoshima Beach, Japan

Aims: The development of a microbial source tracking (MST) method is strongly desired to ensure public health and bacteriological safety in coastal recreation areas. We try to specify the source of faecal pollution by applying pulsed‐field gel electrophoresis (PFGE) to the study of the aquatic environment on Aoshima Beach, Japan. Methods and Results: Enterococcus faecium, an enterococcus, was used as a faecal indicator bacterium in this study. Enterococcus faecium strains were isolated and identified from each water sample collected from Aoshima Beach and five rivers (Oyodo, Kiyotake, Kaeda, Chifuku and Tsukunami Rivers) that might be potential sources of faecal pollution. Enterococcus faecium strains collected from water samples were analysed using PFGE. The similarities of all the PFGE types of the Ent. faecium strains were compared using dendrogram analysis. The PFGE types of the strains isolated from Aoshima Beach showed a high similarity to those of the strains isolated from the Oyodo River at a 0·9 similarity level. It was suggested that the Oyodo River is the source of faecal pollution on Aoshima Beach. Conclusions: The PFGE analysis using enterococci is a potential tool for the MST of faecal indicator bacteria that can be applied to the study of the coastal environment. Significance and Impact of the Study: This is one of the studies that PFGE was applied to the coastal environment. The approach using PFGE could estimate the river that is source of faecal pollution in Aoshima Beach. By applying PFGE as a tool of MST method, detailed information of faecal pollution in coastal area can be provided.     

杭州湾滩涂Na元素含量对植物多样性和优势度的影响

钠元素是滩涂湿地土壤盐分的最主要成分。利用样方法调查了杭州湾滩涂湿地的植物多样性及其分布,以及土壤钠含量对植物多样性和优势度的影响,用相关回归方法对数据进行分析处理。结果表明：（1）海塘内的物种多样性要高于海塘外,有11种植物,优势植物是芦苇（Phragmites australis）和互花米草（Spartina alterniflora）,且互花米草的优势度要高于芦苇;但是在海塘外的自然滩涂,则只出现3种植物,主要优势植物是互花米草和海三棱藤草（Scirpus xmariqueter）,芦苇则较为少见。在海塘外的海三棱藤草-互花米草混合群落中,海三棱藤草的优势度要高于互花米草。（2）物种丰富度指数（Margalef指数）和物种多样性（Simpson指数）指数均与土壤钠含量呈极显著负相关关系,通过回归分析得回归方程分别为y（Margalef指数）=-0．05x＋1．608（R^2=0．732,P〈0．01,n=10）,y（Simpson指数）=-0．038x＋1．214（R^2=0．926,P〈0．01,n=10）。（3）海塘内互花米草的重要值与土壤钠含量呈极显著正相关,y=0．033x-0．007（R^2=0．802,P〈0．01,n=10）;而芦苇重要值则与其呈极显著负相关,y=-0．013x＋0．419（R^2=0．607,P〈0．01,n=10）。在海塘外的混合群落中,互花米草和海三棱藤草的重要值与土壤钠含量之间没有明显的相关关系。（4）随着（海塘）围垦时间的延长,其物种多样性呈现增大的趋势,中生植物更为丰富,而盐生植物逐渐萎缩。     

Reproductive strategy of the ghost shrimp Callichirus major (Crustacea: Axiidea: Callianassidae) from the southwestern Atlantic: sexual maturity of females,fecundity, egg features,and reproductive output

Reproduction and reproductive investment of females is an intriguing feature in axiidean shrimps. They have a cryptic behavior and great ecological importance in sediment turnover, and recycling of organic material and nutrient. Herein, we describe different aspects of the reproductive biology (size at sexual maturity of females, fecundity, egg characteristics, and reproductive output [RO]) of the ghost shrimp Callichirus major from the southeastern coast of Brazil. Females reached sexual maturity at sizes ≥11.85?mm dorsal oval length. Fecundity increased significantly with female size and varied between 1455 and 9931 eggs (average 4564 eggs). Individual egg volume almost doubled during embryogenesis, and average egg water content increased during the incubation period from 75.0 to 93.3%. The egg mass comprised on average 13.2% of the dry body weight of females. This relatively high RO value is probably compensatory to the relatively low number of ovigerous females in axiidean populations. The few published data on RO values suggest that female investment in reproduction of axiidean shrimps is somewhat higher than in other decapods. The high investment in egg production reflects most likely an effort to maximize the viability of the progeny. Studies with additional congeneric species will clarify whether there is a tendency of axiidean shrimps to have RO values at the upper end of the range reported for decapods.     

Seed germination responses to varying environmental conditions and provenances in Crucianella maritima L., a threatened coastal species

Seed germination (effects of light, temperature, NaCl and KNO₃) of the coastal endangered species Crucianella maritima was investigated by testing seeds from three different populations. Data were analyzed by means of Generalized Linear Mixed Model (GLMM). The principal results showed that germination of C. maritima seeds was characterized by photoinhibition, absence of primary dormancy and salt-induced secondary dormancy, with no need for high nutrient availability (KNO₃). Intraspecific differences in germination pattern emerged, apparently due to a different seed mass. These results show important germination traits of C. maritima which should be taken into account in possible reintroduction attempts aimed at restoring threatened populations of this species.     

A life in the surf zone: Age and feeding habits of the pompano (Trachinotus ovatus,Linnaeus, 1758) on the beaches of the Gulf of Cádiz (south-west Iberian Peninsula)

Surf zones are crucial habitats for many fish species, where they spend the initial stages of their lives, finding food and shelter. One such species is the pompano (Trachinotus ovatus). The aim of this study was to examine the age and diet of the pompano within the surf zone, along with any potential variations in the environment. The average size of the specimens was 10.61 ± 4.91 cm. The length–weight relationship was total weight (TW) = 0.0136*total length (TL)^2.8512 (parameter a: 95% C.I. : 0.0130–0.0142 and parameter b: 95% C.I. : 2.8318–2.8705). The most abundant age classes were 0+ and 1+, making up 97% of the captured specimens, with significant differences in the abundance of age classes depending on the time of the day and season. The pompano primarily fed on clupeiforms, copepods, and mysids, with significant variations in diet based on the time of the day, season, and size of the specimens. This study contributes new information about the use of the surf zone by T. ovatus in its early years of life, underscoring the importance of these areas and their role as an additional ecosystem service.     

Effects of sandblasting and salt spray on inland plants transplanted to coastal sand dunes

A transplant experiment was conducted on a sandy beach to elucidate whether salt spray and sandblasting are the major factors inhibiting inland plants from becoming established on coastal sand dunes. Potted inland plants of Miscanthus sinensis and Imperata cylindrica var. koenigii were transplanted in two zones on the beach and in one area far inland from the beach. One zone on the beach (sea side) was located on a front dune that was occupied by native sand-dune plants; the other zone (land side) was located behind the sand dunes, where grassland comprised both sand-dune and inland species. To assess the condition of transplants, we measured changes in the canopy leaf area periodically at all sites. The final dry weight at each site was determined at the end of the experiment. Seasonal changes in sandblasting and salt spray intensities were evaluated periodically at the sites by measurement of the opaqueness of exposed transparent plastic sheets and the amount of sodium trapped in exposed filter papers, respectively. All transplants died in the sea-side zone, where both salt spray and sandblasting were most frequent and intense. The final dry weight was greatest at the inland site, which lacked salt spray and sandblasting. Although salt spray was intense in the land-side zone, the canopy leaf area decreased considerably only in seasons during which salt spray was accompanied by intense sandblasting. We concluded that sandblasting accompanied by salt spray is one of the main factors inhibiting the survival and growth of inland plants on coastal sand dunes.     

Phylogeographic patterns of a lower intertidal isopod in the Gulf of California and the Caribbean and comparison with other intertidal isopods

A growing body of knowledge on the diversity and evolution of intertidal isopods across different regions worldwide has enhanced our understanding on biological diversification at the poorly studied, yet vast, sea–land interface. High genetic divergences among numerous allopatric lineages have been identified within presumed single broadly distributed species. Excirolana mayana is an intertidal isopod that is commonly found in sandy beaches throughout the Gulf of California. Its distribution in the Pacific extends from this basin to Colombia and in the Atlantic from Florida to Venezuela. Despite its broad distribution and ecological importance, its evolutionary history has been largely neglected. Herein, we examined phylogeographic patterns of E. mayana in the Gulf of California and the Caribbean, based on maximum‐likelihood and Bayesian phylogenetic analyses of DNA sequences from four mitochondrial genes (16S rDNA, 12S rDNA, cytochrome oxidase I gene, and cytochrome b gene). We compared the phylogeographic patterns of E. mayana with those of the coastal isopods Ligia and Excirolana braziliensis (Gulf of California and Caribbean) and Tylos (Gulf of California). We found highly divergent lineages in both, the Gulf of California and Caribbean, suggesting the presence of multiple species. We identified two instances of Atlantic–Pacific divergences. Some geographical structuring among the major clades found in the Caribbean is observed. Haplotypes from the Gulf of California form a monophyletic group sister to a lineage found in Venezuela. Phylogeographic patterns of E. mayana in the Gulf of California differ from those observed in Ligia and Tylos in this region. Nonetheless, several clades of E. mayana have similar distributions to clades of these two other isopod taxa. The high levels of cryptic diversity detected in E. mayana also pose challenges for the conservation of this isopod and its fragile environment, the sandy shores.     

Swimming ability and burrowing time of two cirolanid isopods from different levels of exposed sandy beaches

Most of the macroinfauna from sandy beaches is highly mobile, emerging out of the sediment when the tide rises, and using the swash to migrate up and down the beach face or feed (searching for prey or carrion). After swash excursions, they usually burrow back into the sediment, maintaining zonation at low tide. Therefore, the different species abilities to emerge, move around and burrow under different swash climates and sediment conditions are expected to influence observed distribution patterns. Nonetheless, few attempts have been made to understand behavioral mechanisms of these organisms in moving fluids.In this study, we used a flume tunnel to investigate the orientation, swimming ability and burrowing time of two similar species of cirolanid isopods, Excirolana armata Dana and Excirolana braziliensis Richardson, under current velocities ranging from 5 to 30 cm·s⁻¹. E. armata inhabits middle levels of dissipative to intermediate beaches, while E. braziliensis is found towards the upper level of a wider range of beach states. Both species oriented countercurrent above a threshold velocity, which turned out to be significantly lower for E. armata than for E. braziliensis. E. armata proved to be a stronger swimmer as shown by the higher velocities surmounted, and the less drags experienced at the highest current velocity. E. armata also burrowed faster than E. braziliensis. Burrowing time was affected by sediment grain size and water content, but not by water flow. Once organisms managed to begin burrowing under different flow conditions, they were not affected by current velocity. Nonsaturated sand precluded burial, while coarse sand retarded it. Differences in the observed patterns of across-beach distribution may thus be the result of species-specific behavioral responses to swash climate, manifested in swimming ability, burying and orientation in directional flows.