Pattern of distribution of selected trace elements in the marine brown alga,Sargassum filipendula Ag. from Sri Lanka

Baseline concentrations together with biological variations of 29 trace elements (Ag, As, Au, Ba, Br, Cd, Ce, Co, Cr, Cs, Eu, Fe, Hf, I, Mn, Mo, Ni, Pb, Rb, Sb, Sc, Se, Sm, Sr, Tb, Th, Yb, Zn and Zr) were investigated in the brown alga, Sargassum filipendula collected from the western coast of Sri Lanka. Several elements (Co, Cr, Fe, Hf, Ni, Sc, Se, Th, Zr and the rare earth elements) were found to be enriched in S. filipendula compared to NIES No. 9 Sargasso reference material. Concentration of strontium in S. filipendula was highest at all sites. Chemical abundance of the rare earth elements decreased approximately linearly with increasing atomic numbers. The pattern of elemental distribution appears to be due to the fact that S. filipendula seems capable of concentrating high levels of trace elements under conditions of their very low availability in sea water. Concentration factors for elements in S. filipendula lie in a higher range compared with those reported in the literaure for brown algae.     

Macro- and mesoherbivores prefer native seaweeds over the invasive brown seaweed <Emphasis Type="Italic">Sargassum muticum</Emphasis>: a potential regulating role on invasions

Herbivory has a strong impact on algal distribution, abundance and community structure and may influence the establishment and spread of introduced seaweed species. In this study, we assess the potential regulating role of herbivory on one of the most invasive brown seaweeds: Sargassum muticum. Multiple choice feeding experiments were conducted with 13 native seaweeds, S. muticum and 5 herbivore species from the Northwest, Southwest and South of Portugal. S. muticum was always the least or among the least preferred seaweeds and attained one of the highest growth rates of the tested seaweeds, with and without herbivores. The addition of herbivores increased the number of cases by 40% in which the invader had higher growth rates. Our results suggest that low grazing pressure on S. muticum by the recipient herbivore community may give the invader a competitive advantage over at least part of the native seaweed community, thereby contributing to the invasiveness of S. muticum along the Portuguese coast.     

Effects of emersion and temperature upon growth of the tropical brown alga Padina japonica,using a tide-simulation apparatus

A simple tide-simulation apparatus was used to investigate the influence of emersion and temperature on the intertidal growth of Padina japonica Yamada in both the juvenile and adult growth phases. The upper zonation limits are not determined by the sensitivity of any particular growth phase, since all phases show the same emersion tolerance limits. The species grows best when continuously submerged, and growth rates decrease with increasing emersion up to a clear upper zonation boundary. High temperature reduces the emersion tolerance and is therefore an important factor in tropical intertidal zonation.     

Numerical modeling of simultaneous tracer release and piscicide treatment for invasive species control in the Chicago Sanitary and Ship Canal,Chicago, Illinois

In December 2009, during a piscicide treatment targeting the invasive Asian carp in the Chicago Sanitary and Ship Canal, Rhodamine WT dye was released to track and document the transport and dispersion of the piscicide. In this study, two modeling approaches are presented to reproduce the advection and dispersion of the dye tracer (and piscicide), a one-dimensional analytical solution and a three-dimensional numerical model. The two approaches were compared with field measurements of concentration and their applicability is discussed. Acoustic Doppler current profiler measurements were used to estimate the longitudinal dispersion coefficients at ten cross sections, which were taken as reference for calibrating the longitudinal dispersion coefficient in the one-dimensional analytical solution. While the analytical solution is fast, relatively simple, and can fairly accurately predict the core of the observed concentration time series at points downstream, it does not capture the tail of the breakthrough curves. These tails are well reproduced by the three-dimensional model, because it accounts for the effects of dead zones and a power plant which withdraws nearly 80 % of the water from the canal for cooling purposes before returning it back to the canal.     

Mechanisms of habitat segregation between an invasive and an indigenous mussel: settlement,post-settlement mortality and recruitment

The mussel Mytilus galloprovincialis is highly invasive worldwide, but displays varying degrees of local and regional coexistence with indigenous mussels through spatial habitat segregation. We investigated the roles of settlement, post-settlement mortality, juvenile growth and recruitment in partial habitat segregation between the invasive M. galloprovincialis and the indigenous mussel Perna perna on the south coast of South Africa. We used two study locations, Plettenberg Bay and Tsitsikamma, 70 km apart, with two sites (separated by 300–400 m) per location, each divided into three vertical zones. There were no significant effects in Tsitsikamma, where daily settlement and monthly recruitment were significantly lower than in Plettenberg Bay. In Plettenberg Bay, settlement (primary and secondary) and recruitment of both species decreased upshore. Post-settlement mortality was measured over two consecutive 6-day periods during a spring tide and a neap tide. For both species mortality was low on the low-shore. High-shore mortality was consistently low for M. galloprovincialis, but increased dramatically for P. perna during spring tide. No data were obtained for growth of P. perna, but juvenile M. galloprovincialis grew more slowly farther upshore. P. perna recruited mainly in spring and summer, with a peak in summer far greater than for M. galloprovincialis. Recruitment of M. galloprovincialis was more protracted, continuing through autumn and winter. Thus local coexistence is due to a combination of pre- and post-recruitment factors differing in importance for each species. P. perna is excluded from the high-shore by recruitment failure (low settlement, high mortality). High survival and slow growth in juveniles may allow large densities of M. galloprovincialis to accumulate there, despite low settlement rates. With no differences between species in settlement or mortality on the low-shore, exclusion of M. galloprovincialis from that zone is likely to be by post-recruitment processes, possibly strengthened by periodic heavy recruitments of P. perna. At larger scales, larval retention and protracted recruitment contribute to the success of M. galloprovincialis at Plettenberg Bay, while recruitment limitation may explain why M. galloprovincialis is less successful at other sites.     

Micropollutants in three tributaries of Lake Constance, Argen, Schussen and Seefelder Aach: a literature review

A literature review made evident that in three tributaries of Lake Constance, Argen, Schussen and Seefelder Aach 82 micropollutants (including 3 metabolites of pesticides) were detected in at least one of the streams. Quality standards according to the EU Water Frame Directive (which however comprises only 16 of the detected chemicals) are not exceeded in any of the streams. The comparison of maximal values with existing threshold values and effect concentrations obtained in ecotoxicological analyses and biomarker studies revealed 35 substances to be of relevance in at least one of the three waters. These were 5 chemicals in the Argen, 31 chemicals in the Schussen, and 17 chemicals in the Seefelder Aach, for which effects on mortality, development, health or reproduction in aquatic organisms cannot be excluded.     

Supply-side ecology of the brown mussel,<Emphasis Type="Italic"> Perna perna</Emphasis>: an investigation of spatial and temporal variation in,and coupling between,gamete release and larval supply

Sampling of recruitment-associated variables of Perna perna was done approximately monthly for 14 months at intertidal locations 500 m apart, nested within sites 25 km apart. Paired with intertidal locations were nearshore locations, 600 m to sea. Sampling assessed spawning, densities of larvae in the water column and densities of late plantigrades and juveniles on the shore. Major events in each variable were synchronous over larger scales (10s of kilometres) while subsidiary events were synchronised at smaller scales, varying within sites (100s of metres) or even within locations (metres). This suggests that the processes driving major events operated over large scales while processes operating at much more local scales drove less intense, more localised events. A major spawning event occurred at all locations in May–June 1998. Weaker spawning events occurred at different times in different locations. Larvae were found on 80% of sampling occasions, densities peaking in January–March 1998 and 1999 at all locations. Plantigrades and juveniles showed less clear patterns, with considerable residual variation. There was no sign of strong coupling among variables with few significant direct or cross correlations. The major sources of variability shifted from time to space as one progressed from spawning, to plantigrade density to juvenile density. For spawning, time was the most important source (58%) of heterogeneity and space accounted for little (8%) of the total variance. For larvae and late plantigrades, time was still the most important source of variability (41% and 33%, respectively), but space was a much more substantial component. For juveniles, small-scale (residual) spatial variability dominated total variability (75%). This strongly suggests the importance of hydrography and its effects on variation in delivery of larvae to the intertidal from offshore. These findings also indicate greater spatial heterogeneity as recruits age, reflecting small-scale variations in larval delivery and the increasing importance of post-settlement mortality.Communicated by G.F. Humphrey, Sydney     

Seed terminal velocity, wind turbulence, and demography drive the spread of an invasive tree in an analytical model

Little is known about the relative importance of mechanistic drivers of plant spread, particularly when long-distance dispersal (LDD) events occur. Most methods to date approach LDD phenomenologically, and all mechanistic models, with one exception, have been implemented through simulation. Furthermore, the few recent mechanistically derived spread models have examined the relative role of different dispersal parameters using simulations, and a formal analytical approach has not yet been implemented. Here we incorporate an analytical mechanistic wind dispersal model (WALD) into a demographic matrix model within an analytical integrodifference equation spread model. We carry out analytical perturbation analysis on the combined model to determine the relative effects of dispersal and demographic traits and wind statistics on the spread of an invasive tree. Models are parameterized using data collected in situ and tested using independent data on historical spread. Predicted spread rates and direction match well the two historical phases of observed spread. Seed terminal velocity has the greatest potential influence on spread rate, and three wind properties (turbulence coefficient, mean horizontal wind speed, and standard deviation of vertical wind speed) are also important. Fecundity has marginal importance for spread rate, but juvenile survival and establishment are consistently important. This coupled empirical/theoretical framework enables prediction of plant spread rate and direction using fundamental dispersal and demographic parameters and identifies the traits and environmental conditions that facilitate spread. The development of an analytical perturbation analysis for a mechanistic spread model will enable multispecies comparative studies to be easily implemented in the future.     

Distribution pattern, reproductive traits, and molecular analysis of two coexisting vermetid gastropods of the genus Petaloconchus: a Caribbean endemic and a potential invasive species

Vermetid gastropods are characterized by complex taxonomy and unusual ecology. A survey of the fouling community in the intake channel at the Planta Centro Power Plan in Puerto Cabello, Venezuela, found massive colonies of vermetid gastropods of the genus Petaloconchus. We arbitrarily named two prevalent varieties as black and brown-orange morphs, distinguishing based on the color of their soft bodies. Spatial distribution was different for the morphs. The black morph was present along the jetty, with higher average densities in the shallower intertidal area (410 vs. 143 ind m⁻²), while the brown-orange morph was only present at the initial part of the channel (μ = 83 ind m⁻²). Both produced small eggs (142 vs. 180 μm diameter on average), with the orange-brown eggs being slightly larger, but the morphs differed in other reproductive aspects. The brown-orange morph produced significantly fewer capsules (up to nine simultaneously per female) with fewer embryos (average of 27 viable embryos/capsule) that hatched at a larger size (577 μm on average), allocating about 17.64% of the initial egg production to nurse eggs. In contrast, the black morph produced up to 14 capsules simultaneously, hatched an average of 178 veligers of 212 μm, and produced no nurse eggs. The intra-capsular development reached a more advanced stage in the brown-orange morph than in the black one. Several cytochrome subunit I (COI) and 16S rRNA (16S) haplotypes were found for the black morph, when compared to only one haplotype for both genes present for the brown-orange morph. Preliminary phylogenetic analyses separated the morphs into different clades, supported by robust bootstrap values and posterior probabilities (>98). Our results indicate that the morphs are two different species: the black morph was identified as Petaloconchus cf. varians and the brown-orange morph as a non-described species, Petaloconchus sp. (orange). The first is endemic to the Caribbean, while the second is potentially an introduced species.     

Fauna of the green alga Cladophora glomerata in the Baltic Sea: density, diversity, and algal decomposition stage

The green alga Cladophora glomerata (L.) is a common macrophyte in the northern Baltic Sea, where it forms drifting mats during summer. We studied the effect of its stage of decomposition on the density, diversity, and resource usage of associated meio- and macrofauna. We hypothesised that mobile species would show small variation in food preferences among decomposition stages, while high variation was expected in stationary species, as reflected in their stable isotope signatures. The assemblage structure of the fauna differed between the 3 studied algal degradation stages, Green (attached, healthy), Degraded (attached, but starting to decay), and Drift (detached, decaying). C/N ratios were highest in green algae and decreased in decaying algal stages. Variation in stable isotope ratios of stationary and mobile species supported our resource use hypothesis. The decomposition stage of C. glomerata significantly affected the carbon and nitrogen stable isotope ratios of both the alga and its main grazer species. Higher invertebrate diversity in the more decaying stages was probably facilitated by decomposer microbes adding resource types and by the proximity of the detached algal mats to the sediment.     

Predation risk and the territory value of cover: an experimental study

In an experiment on territorial brown trout (Salmo trutta), we addressed the novel hypothesis that protective cover increases the value of a territory in relation to the perceived level of predation risk. We predicted that territory holders should invest more resources defending territories with cover than territories without cover, and that defence should increase as predation risk increases. First, trout were allowed to establish ownership in territories with or without overhead cover. Second, predation risk was manipulated by simulating aerial predator attacks in half of the territories of each type, whereupon the preference for cover was estimated. Third, owners of the four types of territories were staged in dyadic contests against size-matched intruders. Territory owners showed a preference for cover, which increased further after simulated predator attacks. In subsequent contests, conflicts over territories with cover were settled faster than conflicts over territories without cover, which may suggest that the value of cover increases the motivational asymmetry between owner and intruder. Consistent with our hypothesis, owners of territories with cover were much more aggressive if they had been subjected to predator attacks the day before the conflict. These results suggest that territory owners are able to estimate the value of protective cover in response to variation in the level of predation risk in the habitat.Communicated by J. Krause     

Chromium in intertidal sediments of the Clyde,UK: potential for remobilisation and bioaccumulation

Detailed surveys of intertidal sediments have been performed along the north and south shores of the Inner Clyde estuary, UK. Surface sediment data reveal significant spatial variation in Cr content and an association with major sediment characteristics and location within the estuary. Depth variation for Cr and other heavy metals cannot be explained by variation in major geochemical controls such as grain size and organic matter and highlights the impact of historical contamination on sediment quality. These elevated levels at depth may still have environmental impact through redox-reactivity, in association with iron and manganese. Sequential extraction of sediments and pore water analysis of Cr(VI) and Cr(III) provide detailed information on release potential from the sediments. The implication of Cr mobility for biota in the estuary has been assessed by the analysis of a common marine bivalve, Mytilus edulis (Blue Mussel) and a burrowing polychaete, Nereis diversicolor (rag worm) from a number of survey sites. Bioconcentration factors for Mytilus indicate that the weakly held portion of sediment Cr is available for uptake and in the case of Nereis, bioaccumulation appears to be inhibited by sediment organic matter.     

Municipal solid waste,an overlooked route of transmission for the severe acute respiratory syndrome coronavirus 2: a review

Environmental Chemistry Letters - Municipal solid waste could potentially transmit human pathogens during the collection, transport, handling, and disposal of waste. Workers and residents living in...     

Native ecotypic variation and the role of host identity in the spread of an invasive herbivore, Cactoblastis cactorum

Environmental niche models (ENMs) have gained enormous popularity as tools to investigate potential changes in species distributions resulting from climate change and species introductions. Despite recognition that species interactions can influence the dynamics of invasion spread, most implementations of ENMs focus on abiotic factors as the sole predictors of potential range limits. Implicit in this approach is the assumption that biotic interactions are relatively unimportant, either because of scaling issues, or because fundamental and realized niches are equivalent in a species' native range. When species are introduced into exotic landscapes, changes in biotic interactions relative to the native range can lead to occupation of different regions of niche space and apparent shifts in physiological tolerances. We use an escaped biological control organism, Cactoblastis cactorum (Berg.), to assess the role of the environmental envelope as compared with patterns of host-herbivore associations based on collections made in the native range. Because all nonnative populations are derived from a single C. cactorum ecotype, we hypothesize that biotic interactions associated with this ecotype are driving the species' invasion dynamics. Environmental niche models constructed from known native populations perform poorly in predicting nonnative distributions of this species, except where there is an overlap in niche space. In contrast, genetic isolation in the native range is concordant with the observed pattern of host use, and strong host association has been noted in nonnative landscapes. Our results support the hypothesis that the apparent shift in niche space from the native to the exotic ranges results from a shift in biotic interactions, and demonstrate the importance of considering biotic interactions in assessing the risk of future spread for species whose native range is highly constrained by biotic interactions.     

Short- and long-term consequences of prenatal testosterone for immune function: an experimental study in the zebra finch

Hormone-mediated maternal effects play an important role in the formation of a differentiated phenotype. They have been shown to influence a wide array of offspring traits, both early in life and in adulthood. One important offspring trait that is under the influence of maternal androgens is the immune system. In birds, a growing number of studies show that yolk androgens modulate immune function during the chick stage. However, there is a lack of knowledge regarding long-term effects of prenatal androgens on offspring immunity. In this study, we therefore investigated the influence of prenatal testosterone (T) on several measures of immunity in fledgling and adult zebra finches (Taeniopygia guttata). Cell-mediated immune response (towards phytohaemagglutinin, PHA) of fledglings hatching from control eggs was negatively related to brood size, whereas there was no such association for fledglings hatching from eggs with experimentally elevated T levels (T fledglings). Male control fledglings showed reduced mass gain compared to female control fledglings within 24 h after the PHA injection. This pattern was reversed in T fledglings. Total antibody levels in fledglings were not affected by egg treatment. Neither cell-mediated immunity nor total antibody levels in sexually mature zebra finches were influenced by egg treatment. However, there was an immuno-enhancing effect of elevated egg T on both primary and secondary humoral immune responses toward diphtheria and tetanus antigens in ca 5 and 7 month old zebra finches. In addition, the covariation between different immune components differed between T and control offspring, suggesting that egg treatment may have altered the potential trade-offs between different parts of the immune system. Our results suggest that prenatal androgens could be an important factor contributing to individual variation in immune function even in adulthood.     

Three-phase partitioning for the separation of proteins,enzymes, biopolymers,oils and pigments: a review

Environmental Chemistry Letters - Modern biomass and organic waste are becoming major, carbon-neutral sources of fine chemicals, biomolecules and fuels to replace fossil fuel products. As a...