Method for the appraisal of anthropogenic disturbance of macrozoobenthic communities of soft substrata

A method for quantitative appraisal of disturbances of macrobenthic communities of soft substrata caused by anthropogenic pollution is proposed. This method is based on the establishment of the dependence of various parameters characterizing the abundance and structure of communities (biomass, population density, number of species, Shannon-Weaver and Pielou indices, etc.) on the level of total contamination of bottom sediments. Using the percentage of deviation of abundance parameters and ecological indices from the norm (the initial horizontal segment of model curves), as well as ERL _q and ERM _q values, which limit the area of progressive degradation of bottom communities (an almost linear drop in abundance and structure characters), is suggested as a numerical characteristic of such deformations. Mapping of aqueous areas on the basis of these characteristics enabled us to obtain a synoptic view of the extent and spatial scale of anthropogenic impacts. An example of the application of this method for assessment of the state of benthic communities in the Peter the Great Bay (Sea of Japan) is shown for the end of the 1980s. The method is verified on the basis of comparison with the results obtained by standard methods of appraisal of the ecological status of macrozoobenthic communities.     

Comparing Biomass Yields of Low-Input High-Diversity Communities with Managed Monocultures Across the Central United States

Biofuel cropping expansion is increasing pressure on food, grazing, and conservation lands. Debate over the efficacy of converting diverse native plant communities to managed monocultures prompted us to explore the extensive crop and ecological site productivity databases maintained by US Department of Agriculture-Natural Resources Conservation Service. We compared annual net primary productivity (ANPP) of diverse native plant communities to ANPP of alfalfa (Medicago sativa L.) in Nebraska, Kansas, and Oklahoma; to coastal bermudagrass (Cynodon dactylon [L.] Pers.) in northern and central Texas; and to buffelgrass (Pennisetum ciliare [L.] Link.) in extreme southern Texas. In only 21% of the 1,238 sites in Nebraska, Kansas, and Oklahoma did native communities produce more or equivalent ANPP compared with managed alfalfa or coastal bermudagrass. In contrast, southern Texas native communities had greater ANPP than did buffelgrass at 81% of the sites. Regression analyses based on these results suggested that managed switchgrass (Panicum virgatum L.) ANPP would consistently exceed native community ANPP. We identified the type of sites that could remain in diverse communities or be converted to diverse communities and have productivity as great as or greater than highly managed monocultures of alfalfa, coastal bermudagrass, or buffelgrass. However, because of the low ANPP on these sites, biomass production may not be the optimal use of such sites. These lands may be better suited to providing other ecosystem services.     

Ammonium and nitrate uptake by aquatic plants from poorly buffered and acidified waters

In the Netherlands, atmospheric deposition of ammonia compounds, particularly ammonium sulphate, is an important source for the acidification of oligotrophic soft waters. As a consequence, the acidified waters are generally nitrogen enriched, ammonium being the dominant N form. In this study, it is examined how this alteration in the nitrogen household affects the aquatic plant communities in acidifying waters.The uptake of ammonium and nitrate by leaves and roots of two groups of freshwater plants has been studied using glass incubation chambers. The forst group (Littorella uniflora (L.) Aschers.; Lobelia dortmanna L.; Luronium natans (L.) Raf.; Echinodorus ranunculoides (L.) Engelm.) is characteristic of nitrogen-poor soft waters, whereas the second group (Juncus bulbosus L.; Sphagnum flexuosum Dozy & Molk.;Agrostis canina L.; Drepanocladus fluitans (Hedw.) Warnst.) often occurs in dense stands in nitrogen-enriched, acid waters. Both groups have typical adaptations to the nitrogen condition of their aquatic environment. The soft-water species show a nitrate-dominated (63–73%) nitrogen utilization, with the roots as the major (83%) uptake site. Moreover, they are able to survive at very low nitrogen concentrations. The acid-tolerant species have an ammonium-dominated (85–90%) nitrogen utilization, with the leaves as the major (71–82%) uptake site. This group profits from the increased ammonium levels in acid waters. It is concluded that in the case of acidification increased ammonium concentrations additionally account for the suppression of typical soft-water communities by communities dominated by Juncus bulbosus and Sphagnum spp.     

Long-Term Changes in Shallow-Water Fouling Communities of the White Sea

The replacement of an ascidian (Styela rustica L.) fouling community by a blue mussel (Mytilus edulis L.) community was described for the White Sea. The alternation of populations of these two species takes place in fouling communities developing in the upper 3- to 5-m layer of water. The life span of each type of fouling probably depends on interannual climate fluctuations.     

Permanent residents or temporary lodgers: characterizing intracellular bacterial communities in the siphonous green alga Bryopsis

The ecological success of giant celled, siphonous green algae in coastal habitats has repeatedly been linked to endophytic bacteria living within the cytoplasm of the hosts. Yet, very little is known about the relative importance of evolutionary and ecological factors controlling the intracellular bacterial flora of these seaweeds. Using the marine alga Bryopsis (Bryopsidales, Chlorophyta) as a model, we explore the diversity of the intracellular bacterial communities and investigate whether their composition is controlled by ecological and biogeographic factors rather than the evolutionary history of the host. Using a combination of 16S rDNA clone libraries and denaturing gradient gel electrophoresis analyses, we show that Bryopsis harbours a mixture of relatively few but phylogenetically diverse bacterial species. Variation partitioning analyses show a strong impact of local environmental factors on the presence of Rickettsia and Mycoplasma in their association with Bryopsis. The presence of Flavobacteriaceae and Bacteroidetes, on the other hand, reflects a predominant imprint of host evolutionary history, suggesting that these bacteria are more specialized in their association. The results highlight the importance of interpreting the presence of individual bacterial phylotypes in the light of ecological and evolutionary principles such as phylogenetic niche conservatism to understand complex endobiotic communities and the parameters shaping them.     

Predicting the potential habitat of the harmful cyanobacteria Lyngbya majuscula in the Canary Islands (Spain)

This study presents the ecological niche and the potential distribution of Lyngbya majuscula in the Canary Islands (Spain) based on a bloom of this species on the eastern side of the Canarian Archipelago, in the Marine Reserve of La Graciosa (MRG). This finding represents the first L. majuscula bloom recorded in waters around the Canary Islands and this side of the Atlantic Ocean. The modeled suitability map revealed a potential distribution of L. majuscula in rocky and sandy habitats within shallow and sheltered areas exposed to sedimentation; where L. majuscula blooms had not previously been reported. The L. majuscula bloom detected in MRG is affecting rocky and sandy communities in this area. The possible expansion of these blooms may have harmful effects on important communities in the Canary Islands, including some of high ecological importance such as the Cymodocea nodosa meadows. Results of the L. majuscula distribution model presented here can be used to develop management strategies that avoid or minimize the risk of future bloom occurrences or expansions and their negative effects on the environment. The causes of L. majuscula blooms in MRG are being investigated.     

Ecological ranges and types of rarity in the Kuznetsk Alatau of some <Emphasis Type="Italic">Saussurea</Emphasis> DC. species

An analysis of indicator values of four Saussurea DC. species, S. baicalensis (Adams) B. L. Rob., S. frolowii Ledeb., S. salicifolia (L.) DC., and S. schanginiana (Wydl.) Fisch. ex Serg., have been carried out by the method of indicator scales of soil moisture and nutrient availability and salinity in more than 1600 relevés. The size of their ecological ranges and the values of their competitiveness in phytocenoses are determined. As a result of a comparison of the locality of local populations within the ecological range and their occurrence, the vulnerability of S. baicalensis, S. frolowii, S. salicifolia, and S. schanginiana in the Kuznetsk Alatau is evaluated. The types of rarity for these species in the Kuznetsk Alatau are determined.     

Diversity and dynamics of fungal endophytes in leaves, stems and roots of Stellera chamaejasme L. in northwestern China

This study was conducted to explore fungal endophyte communities inhabiting a toxic weed (Stellera chamaejasme L.) from meadows of northwestern China. The effects of plant tissue and growth stage on endophyte assemblages were characterized. Endophytes were recovered from 50 % of the samples, with a total of 714 isolates. 41 operational taxonomical units (OTUs) were identified, consisting of 40 OTUs belonging primarily to Ascomycota and 1 OTU belonging to Basidiomycota. Pleosporales and Hypocreales were the orders contributing the most species to the endophytic assemblages. The total colonization frequency and species richness of endophytic fungi were higher in roots than in leaves and stems. In addition, for the plant tissues, the structure of fungal communities differed significantly by growth stages of leaf emergence and dormancy; for the plant growth stages, the structure of fungal communities differed significantly by plant tissues. This study demonstrates that S. chamaejasme serves as a reservoir for a wide variety of fungal endophytes that can be isolated from various plant tissues.     

Mollusc communities along upstream–downstream gradients in small coastal basins of the south-western Iberian Peninsula

Freshwater mollusc communities readily respond to various human-induced stressors, and thus are appropriate models for studying the effects of such stressors on the structure and dynamics of stream macroinvertebrate communities. This paper examined the distribution of freshwater molluscs in 35 stream reaches of 18 small coastal basins in the south-western Iberian Peninsula. Using several multivariate techniques, I showed that mollusc distribution mainly responded to gradients in drainage area, water availability, pollution and salinity. Upstream and downstream communities were clearly differentiated, with the former dominated by freshwater species (Bithynia tentaculata, Galba truncatula, Radix balthica, Ancylus fluviatilis and Planorbarius metidjensis) and the latter by species typical of brackish waters (Peringia ulvae and Myosotella myosotis). There was a clear decrease in species richness from upper to lower reaches. The conservation of mollusc communities of these small basins requires a deeper understanding of their ecological requirements, effective control of urban discharges and an analysis of their interaction with invasive species.     

A comparative study of chitinase activity in digestive tract of Serranus cabrilla and Serranus scriba

Chitinolytic activity was searched for in oesophagus, stomach, intestine, pyloric caeca and liver of two sympatric closely related species of Serranidae (Teleostei, Perciformes): Serranus cabrilla (L.) and Serranus scriba (L.) living near the rocky shore of Calvi (Corsica, Mediterranean Sea). The chitinase activity was much higher in stomach than in other parts of the digestive tract and liver in both species. In extracts of gastric mucosa, the chitinase activity was more important in S. cabrilla than in S. scriba; an appointed situation was found in the extracts of intestine and pyloric caeca. These findings are discussed as aspects of the ability of these species to share very near ecological niches.     

Relative Importance of Deterministic and Stochastic Processes in Driving Arbuscular Mycorrhizal Fungal Assemblage during the Spreading of a Toxic Plant

Both deterministic and stochastic processes are expected to drive the assemblages of arbuscular mycorrhizal (AM) fungi, but little is known about the relative importance of these processes during the spreading of toxic plants. Here, the species composition and phylogenetic structure of AM fungal communities colonizing the roots of a toxic plant, Ligularia virgaurea, and its neighborhood plants, were analyzed in patches with different individual densities of L. virgaurea (represents the spreading degree). Community compositions of AM fungi in both root systems were changed significantly by the L. virgaurea spreading, and also these communities fitted the neutral model very well. AM fungal communities in patches with absence and presence of L. virgaurea were phylogenetically random and clustered, respectively, suggesting that the principal ecological process determining AM fungal assemblage shifted from stochastic process to environmental filtering when this toxic plant was present. Our results indicate that deterministic and stochastic processes together determine the assemblage of AM fungi, but the dominant process would be changed by the spreading of toxic plants, and suggest that the spreading of toxic plants in alpine meadow ecosystems might be involving the mycorrhizal symbionts.     

New RT-qPCR assay for viral nervous necrosis virus detection in sea bass,Dicentrarchus labrax (L.): application and limits for hatcheries sanitary control

A sensitive and quantitative one step RT-qPCR method was developed to study Viral Nervous Necrosis (VNN) virus loads in sea bass Dicentrarchus labrax (L.) in hatcheries. After determining the limits of this new method, fin tissues were identified as an interesting new simple non-invasive sample source, which might be useful for screening D. labrax (L.) in hatcheries. We observed VNN virus strain V26 associated to D. labrax (L.) eggs and it’s release in tank water during spawning suggesting both vertical transmission to the eggs and the possibility of horizontal transmission by contamination of tank water. VNN is widespread in water bodies and has the ability to infect a large number of fish species, with this in mind, this PCR technique may be used for the surveillance of various fish farms.     

Impact of acidification and eutrophication on macrophyte communities in soft waters in The Netherlands I. Field observations

During the last decades a strong decline has been noticed in the number of waters dominated by “Littorellion” species, mostly isoetids such as Lobelia dortmanna L., Isoetes lacustris L. and Littorella uniflora (L.) Aschers. Sixty-eight waters, which were known to be dominated by L. uniflora after 1950 were investigated. In 1980, L. uniflora appeared to be absent or to have strongly decreased in 53 (78%) of the waters. In 41 of them, Littorella had been replaced by submerged Juncus bulbosus L. and/or Sphagnum spp. These changes seem to have been caused by changed inorganic carbon budgets as a consequence of acidification.In the remaining 12 waters, eutrophication of the water and/or sediment seems to be responsible for the changes in the plant communities. Enrichment with phosphate of the mineral sediment alone, leads to luxurious growth of submerged, rooted macrophyte species such as Myriophyllum alterniflorum DC and Ranunculus peltatus Schrank, whereas phosphate-enrichment of both sediment and water leads to luxurious growth of pleustophytes such as Riccia fluitans L. and Lemna minor L. in small, shallow waters, and to plankton bloom and luxurious growth of epiphytes in larger, deeper waters.In these cases light limitation seems to be responsible for the disappearance or decline of the “Littorellion” species.     

Life after establishment: factors structuring the success of a mountain invader away from disturbed roadsides

Climate change and increased anthropogenic activity may both alter the current ranges of non-native plant species in mountainous areas, and could result in increased success of such species at higher elevations in the future. However, the course that management should take is often unclear due to a lack of information about the dynamics of how successful mountain invaders spread away from roadsides. The goals of this study were to determine if patterns of growth of a successful mountain invader, Linaria dalmatica (L.) Mill., (as measured by species cover) were: (1) similar to those of establishment (as measured by probability of occurrence), and (2) structured by the extant plant community. Study sites were established throughout the current elevation range of L. dalmatica in the Greater Yellowstone Ecosystem, and cover of the species was measured along with several vegetative community characteristics. Elevation influenced probability of occurrence (i.e., chance of establishment) for L. dalmatica, but not cover (which represents growth after establishment). L. dalmatica cover was negatively associated with several vegetative community characteristics which did not appear to be influenced by the presence of L. dalmatica. These results suggest that L. dalmatica establishment may be limited by climate, but that spread of established populations away from roadsides is most influenced by properties of the vegetative community. They further suggest that the resident vegetative communities structure the abundance of this invader, and that to limit spread of this species in mountainous areas, disturbance to the existing vegetative communities should be minimized.     

Leishmania (L.) mexicana Infected Bats in Mexico: Novel Potential Reservoirs

Leishmania (Leishmania) mexicana causes cutaneous leishmaniasis, an endemic zoonosis affecting a growing number of patients in the southeastern states of Mexico. Some foci are found in shade-grown cocoa and coffee plantations, or near perennial forests that provide rich breeding grounds for the sand fly vectors, but also harbor a variety of bat species that live off the abundant fruits provided by these shade-giving trees. The close proximity between sand flies and bats makes their interaction feasible, yet bats infected with Leishmania (L.) mexicana have not been reported. Here we analyzed 420 bats from six states of Mexico that had reported patients with leishmaniasis. Tissues of bats, including skin, heart, liver and/or spleen were screened by PCR for Leishmania (L.) mexicana DNA. We found that 41 bats (9.77%), belonging to 13 species, showed positive PCR results in various tissues. The infected tissues showed no evidence of macroscopic lesions. Of the infected bats, 12 species were frugivorous, insectivorous or nectarivorous, and only one species was sanguivorous (Desmodus rotundus), and most of them belonged to the family Phyllostomidae. The eco-region where most of the infected bats were caught is the Gulf Coastal Plain of Chiapas and Tabasco. Through experimental infections of two Tadarida brasiliensis bats in captivity, we show that this species can harbor viable, infective Leishmania (L.) mexicana parasites that are capable of infecting BALB/c mice. We conclude that various species of bats belonging to the family Phyllostomidae are possible reservoir hosts for Leishmania (L.) mexicana, if it can be shown that such bats are infective for the sand fly vector. Further studies are needed to determine how these bats become infected, how long the parasite remains viable inside these potential hosts and whether they are infective to sand flies to fully evaluate their impact on disease epidemiology.     

Measuring succession: methods for establishing long-term vegetation monitoring sites

Successional stages are often characterized by dominant plant species (species with the highest cover) and their effect on the structure and function of an area through time. However, the plant species determining the ecosystem properties and plant community dynamics may not be the dominant, especially when it is exotic. Understanding plant community dynamics in ecosystems that are uncharacterized and/or affected by invasive plant species requires a data-driven approach and proper placement of monitoring plots. To generate robust datasets on vegetation change through time, monitoring plot placement must consider the scale of ecological variation for both vegetation and soils and plots would ideally be replicated within similar ecological site types to quantify the consistency of successional transitions. We characterized soil and vegetation across and within seven floodplains affected by Russian olive (Elaeagnus angustifolia L.) along the Yellowstone River in southeastern Montana, USA. Using modern Classification and Regression Trees (CART) and multivariate net differentiation, we identified five distinct plant community types, or classes, characterized by their tertiary woody plant cover, not the primary species, Russian olive. Our findings indicate that Russian olive communities differ across space, and these riparian areas can be classified into distinct plant community types. Characterizing plant community types via this analytical approach should allow practitioners to modify management decisions and forecast succession within relevant plant communities.     

The potential of genotypically diverse cultivar mixtures to moderate aphid populations in wheat (Triticum aestivum L.)

Plant species diversity has long been considered a primary driver of arthropod community structure; however, recent ecological research has demonstrated that plant genotypic diversity can also play a major role in influencing the composition of arthropod communities. Genotypic diversity has already been exploited in some agricultural systems to improve disease control and appears to hold promise for managing some insect species as well. To explore the potential for using genotypic diversity within a crop species to help manage insect pests, we used laboratory-based studies to investigate the influence of wheat (Triticum aestivum L.) genotypic diversity on aphid (Rhopalosiphum padi L.) population growth. Increasingly diverse mixtures of wheat genotypes supported lower aphid populations compared with monocultures and were equally productive as single variety plantings. In the absence of aphids, genotypic mixtures were more productive than monocultures. We also analyzed the volatile organic compounds emitted by non-infested genotypic mixtures to provide insight on a possible mechanism influencing aphid populations. Mixtures and monocultures of wheat emitted the same compounds, but mixtures emitted greater amounts of volatile compounds than monocultures. Our results suggest that genotypic mixtures can strongly influence the growth rate and size of aphid populations; therefore, cultivar mixtures appear to hold good potential to be an effective tool for managing insect pests in crop fields.     

Post-fire spread of alien plant species in a mixed broad-leaved forest of the Insubric region

How do tree species regenerate and which ecological conditions are required after forest fire in the Insubric region of the Alps? Are indigenous stand-forming tree species resistant over the invasion of alien plant species after such a disturbance? We addressed these questions in a case study in the Swiss canton of Ticino. In April 2006, a surface fire with severe intensity burnt a forest area of 55 ha on a south-facing slope (400-800 m.a.s.l.). The dominant trees in the investigated area were chestnut (Castanea sativa Mill.), beech (Fagus sylvatica L.) and deciduous oaks (Quercus spp.) mixed with tree species of intermediate height. Vegetation data were collected in May and August 2009 by systematic sampling. Resprouting of the survived trees and generative regeneration were analysed by counting vegetative shoots from sprouting stools, of seedling age, height and damage rate, respectively. Different vegetation structures related to low or high fire intensity were clearly visible three years after the forest fire, creating various habitats for both new invaders and seedlings of the stand-forming trees. The dominant chestnut was the only tree species that regenerated effectively by sprouting from stools. Seedlings of the stand-forming trees grew in high abundance under shadow conditions close to their mother trees which provided the seed source. In contrast, pioneer trees invaded patches where full light was available. Under such conditions the two main woody alien plant species, Ailanthus altissima and Robinia pseudoacacia, grew in high abundance. Due to the different ecological requirements of indigenous and alien tree seedlings, not any interaction between the two groups was detected.     

Effects of experimental climate warming and associated soil drought on the competition between three highly invasive West European alien plant species and native counterparts

It is widely suggested that climate warming will increase the impact of biological invasions, yet, to date studies on the combined effect of these two global changes are scarce. Here, we study how climate warming and associated soil drought affect the competition between native and invasive alien plant species. Three highly invasive alien plant species in West Europe, each with a native competitor, were grown either together or in isolation at ambient and at elevated air temperature (+3 °C) in climate-controlled chambers. Equal amounts of water were added to all communities. Soil drought observed in the heated chambers did not induce severe stress in the plants. In two species pairs, Fallopia japonica (Houtt.)–Cirsium arvense (L.) Scop. and Solidago gigantea Ait.–Epilobium hirsutum L. (alien invasive–native), the native species dominated in mixture, while the alien invasive species dominated in the third pair Senecio inaequidens DC.–Plantago lanceolata L. Warming did not modify the competitive balance in any of these pairs, in spite of enhancing the aboveground biomass of S. inaequidens and P. lanceolata and the greater photosynthetic rates in S. inaequidens. The results of this study cannot be extrapolated to all invasive or exotic species but may represent the possible future of three principle invaders and some of their key native counterparts. Future experiments are needed to identify response patterns of alien plants to climate warming more in general.     

Understory vegetation as an indicator of soil characteristics in the Hyrcanian area,N. Iran

The mesic Caspian (Hyrcanian) forest and ecotone communities provide a marked contrast to the arid and semiarid landscapes associated with most of the territory of Iran. To date, the ecological characteristics of these habitats, threatened and of conservation importance, have been little studied. Accordingly, ecological profiles of some important plant species of these communities have been assessed along two altitudinal gradients (300–2300 m a.s.l.). Vegetation and soils were sampled every 100 m in elevation, with the data subsequently analyzed using TWINSPAN and corrected frequency (CF) analyses. Relationships between soil variables (subdivided into three classes, the lowest, the middle and the upper third of all values) and herbaceous and shrub species (presence/absence data) were analyzed by the polythetic divisive classification method. 379 plant species and eleven soil variables – N, P, K, CaCO₃, EC, pH, organic matter, C/N ratio and percentage of sand, clay and silt – were considered. The ecological profile method was used to evaluate the affinity and significance of associations between the probability of species’ occurrence and topsoil characteristics found by the polythetic method. Five vegetation groups were identified: two groups, with Acer campestre and Quercus macranthera in the tree layer and Veronica mazanderanae and Phuopsis stylosa as herbs, were restricted to forest-steppe ecotones and the upper mountain areas. Three groups, with Acer velutinum, Ruscus hyrcanus, Carpinus betulus, Danae racemosa, Fagus orientalis and Aruncus vulgaris as indicator species, occurred in the forest itself. Of the 42 plant species assessed as being of particular importance, 13 had significant relationships with eight soil factors. Thus, certain species, including endemic plant species of restricted distribution and conservation importance, can be used as indicators of particular soil conditions in the Hyrcanian forest area.