Continuous soil CO<Superscript>2</Superscript> and discrete plume SO<Subscript>2</Subscript> measurements at Mt. Etna (Italy) during 1997–2000: a contribution to volcano monitoring

Continuous monitoring of soil CO₂ dynamic concentration (which is proportional to the CO₂ flux through the soil) was carried out at a peripheral site of Mt. Etna during the period November 1997–September 2000 using an automated station. The acquired data were compared with SO₂ flux from the summit craters measured two to three times a week during the same period. The high frequency of data acquisition with both methods allowed us to analyze in detail the time variations of both parameters. Anomalous high values of soil CO₂ dynamic concentration always preceded periods of increased flux of plume SO₂, and these in turn were followed by periods of summit eruptions. The variations were modeled in terms of gas efflux increase due to magma ascent to shallow depth and its consequent depressurization and degassing. This model is supported by data from other geophysical and volcanological parameters. The rates of increase both of soil CO₂ dynamic concentration and of plume SO₂ flux are interpreted to be positively correlated both to the velocity of magma ascent within the volcano and to lava effusion rate once magma is erupted at the surface. Low rates of the increase were recorded before the nine-month-long 1999 subterminal eruption. Higher rates of increase were observed before the violent summit eruption of September-November 1999, and the highest rates were observed during shorter and very frequent spike-like anomalies that preceded the sequence of short-lived but very violent summit eruptions that started in late January 2000 and continued until late June of the same year. Furthermore, the time interval between the peaks of CO₂ and SO₂ in a single sequence of gas anomalies is likely to be controlled by magma ascent velocity.Editorial responsibility: H. Shinohara     

Differential host use affects fecundity of the gastropod Crepidula onyx

For epibiotic or symbiotic marine invertebrates, alternative host species may differ substantially in quality, and under some circumstances such differences in host quality may lead to the evolution of increased host specificity. However, the fitness consequences of alternative hosts for epibiotic or symbiotic marine invertebrates have rarely been quantified. In Southern California, the gastropod Crepidula onyx is often found as an epibiont on either bay mussels (Mytilus galloprovincialis) or cone snails (Conus californicus). These hosts differ greatly in maximum size, with possible effects on size at sex change and final size in Cr. onyx, and thus on fecundity. Further, Cr. onyx on the two hosts differ in shell shape, possibly affecting the size of the ctenidium, which Cr. onyx uses for suspension feeding. We examined these potential effects of host use on fitness components in Cr. onyx. Epibionts on mussels reached much larger average sizes than did those on cone snails; further, epibionts on mussels often completed sex change at much larger sizes than did those on cone snails. On average, mussel epibionts had threefold higher average fecundities than did cone snail epibionts. Although there was a slight difference in shell shape between epibionts on the two host species, there was no difference in the scaling of ctenidium area with body size for Cr. onyx from the two hosts. The large average differences in fecundity in epibionts associated with the two alternative hosts suggests that there may be strong selection on host choice at larval settlement.     

A standardised sampling protocol for robust assessment of reach-scale fish community diversity in wadeable New Zealand streams

The New Zealand fish fauna contains species that are affected not only by river system connectivity, but also by catchment and local-scale changes in landcover, water quality and habitat quality. Consequently, native fish have potential as multi-scale bioindicators of human pressure on stream ecosystems, yet no standardised, repeatable and scientifically defensible methods currently exist for effectively quantifying their abundance or diversity in New Zealand stream reaches. Here we report on the testing of a back-pack electrofishing method, modified from that used by the United States Environmental Protection Agency, on a wide variety of wadeable stream reaches throughout New Zealand. Seventy-three first- to third-order stream reaches were fished with a single pass over 150–345 m length. Time taken to sample a reach using single-pass electrofishing ranged from 1–8 h. Species accumulation curves indicated that, irrespective of location, continuous sampling of 150 stream metres is required to accurately describe reach-scale fish species richness using this approach. Additional species detection beyond 150 m was rare (<10%) with a single additional species detected at only two out of the 17 reaches sampled beyond this distance. A positive relationship was also evident between species detection and area fished, although stream length rather than area appeared to be the better predictor. The method tested provides a standardised and repeatable approach for regional and/or national reporting on the state of New Zealand's freshwater fish communities and trends in richness and abundance over time.     

黄金岸线海滩能否抵挡极端事件的冲击

砂质海滩是最变化莫测和脆弱的海岸带类型之一。众所周知,海滩在高能环境中会被侵蚀,但海滩上不同位置点对于极端事件的抵御能力则大不相同。而且,侵蚀速率通常受控于海滩状况、机械结构和前期补给。     

Chemical defenses against generalist fish predators and fouling organisms in two invasive ahermatypic corals in the genus Tubastraea

The introduction of exotic marine species has caused considerable economic and ecological damage around the world. Some of these species possess adaptations such as secondary metabolites which facilitate their successful invasion into new areas. In this study we tested two hypotheses: (i) crude extracts produced by two invasive hard corals Tubastraea coccinea and Tubastraea tagusensis, introduced to the southwest Atlantic, inhibit predation by generalist fish; (ii) substances found in the crude extracts of both species reduce or enhance the settlement of other organisms. In an in situ palatability bioassay the extract of T. tagusensis reduced predation by generalist fish. The extracts of both species of coral showed species‐specific effects on fouling organisms in in situ gel plate bioassays. Control and extract plates had similar total cover, although plates with extracts had significantly fewer Cladophora sp., and Lithophyllum sp. was only detected on control gels. In contrast, a hydrozoan was only found on plates with extracts and overall community ordination demonstrated clear differences in the fouling communities between treatments. These results demonstrate that both coral species have chemical substances which can bring about a negative interaction with potential fish predators and competitors such as algal and invertebrate foulers and the advantage gained could explain their success in invading new regions to the detriment of local fauna and flora.     

Benthic geochemistry of manganese in the Bay of Biscay,and sediment mass accumulation rate

Manganese is a major redox reactive element of benthic metabolism. We have built a database of existing knowledge on the benthic geochemistry of Mn in the Bay of Biscay, in order to comprehensively assess the behaviour of Mn in a variety of environments during early diagenesis. The database contains vertical profiles of particulate and dissolved Mn species of 59 cores collected during 17 cruises between 1997 and 2006 at nine stations positioned between 140 and 4,800 m water depths. At all studied stations, Mn species follow the conventional distribution, where Mn(III,IV) species are enriched in the oxic layer, and dissolved Mn is present in the anoxic sediments. A minor part of Mn-oxides originates from sedimenting particles. The major part is of diagenetic origin, and derives from the oxidation of upward-diffusing dissolved Mn(II). Mn-oxide inventories are higher at the deeper stations than at the shallower ones. This difference cannot be attributed to different sources of sedimenting particles, but it must depend on sedimentation rate and diagenetic processes. At depth, dissolved Mn(II) concentrations are constant. This probably reflects equilibrium with an authigenic Mn(II) phase, which is the ultimate phase into which Mn is fossilized. The Mn content of deeper anoxic sediments is similarly low in all the cores studied, associated with corresponding trends of Mn content in sedimenting particles of the Bay of Biscay. Bioturbation, rather than redox oscillations, can convey Mn(III,IV) species downwards into the anoxic sediments where they are reduced, associated with a peak of dissolved Mn. Because dissolved Mn(II) is re-oxidized when it diffuses towards the oxic layer, the inventory of the diagenetic Mn(III,IV) phase remains at steady state, especially at stations where the oxic layer is thick. It then becomes possible to calculate the residence time of diagenetic Mn(III,IV) particles within the oxic layer, using the upward-directed flux of pore water Mn(II). By applying this residence time to the accumulation of sediments within the oxic layer, we obtain the sediment mass accumulation rate. The values calculated for the sediments of the Bay of Biscay fit well with accumulation rates obtained from radionuclides or sediment traps. The method has also been validated with data collected in other marine sedimentary environments. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Distribution of fish in tributaries of the lower Taieri/Waipori rivers,South Island,New Zealand

The distribution of fish within eight small streams feeding into the lower Taieri and Waipori Rivers on the east coast of New Zealand's South Island was examined. A total of eight native and two introduced species were recorded. Eels (Anguilla spp.) and giant kokopu (Galaxias argenteus Gmelin) were the most widely distributed species being located in all streams surveyed. Common bullies (Gobiomorphus cotidianus McDowall) and brown trout (Salmo trutta Linnaeus) were also widely distributed being detected in seven and six of the streams respectively. Three streams of potential conservation significance were identified. These were Picnic Gully Creek which contained a significant population of banded kokopu (Galaxias fasciatus Gray), a Category C threatened species, and Cullens and Alex Creeks which contained significant populations of giant kokopu, a Category B threatened species. The population of giant kokopu in Cullens and Alex Creeks currently represents the largest known population of this species on the east coast of New Zealand (excluding Southland). It has been suggested that brown trout may influence the distribution of native galaxiids. The longitudinal distribution of giant kokopu and brown trout in streams was examined at night using a continuous spotlight sampling approach. Distributions of these two species rarely overlapped at a local scale. Coarse habitat use data indicated that brown trout regularly occupied a variety of habitat types including modified agricultural channels. In contrast, giant kokopu rarely used agricultural channels being predominantly located in pool habitats.     

Defects and hydrolytic weakening in α-berlinite AlPO4 a structural analog of quartz

Berlinite, AlPO₄, is a structural analog of quartz and a number of physical properties are very similar in both materials. It is thus interesting to compare their mechanical properties and investigate the possible role of water. Constant strain rate tests on wet synthetic crystals have been performed at room temperature and at 600 MPa confining pressure. They indicate that \((000){1 \mathord{\left/ {\vphantom {1 3}} \right. \kern-0em} 3}\langle 11\bar 20\rangle \) is the easy glide system. Detailled investigation of the crystal structure shows that the corresponding a dislocations can glide in such a way that only the weaker Al—O bonds are broken. This explains why this glide system is much more easily activated in berlinite than in quartz. Deformation experiments at higher temperature and at atmospheric pressure clearly show a thermally activated regime. However the actually available crystals are so rich in water that above 300° C the dislocation structure resulting from deformation is completely hidden by water precipitation and coarsening of the as-grown fluid inclusions. Like for wet quartz this later phenomenon generates numerous bubbles and sessile dislocation loops.     

Weka‐STPM: a Software Architecture and Prototype for Semantic Trajectory Data Mining and Visualization

Enormous quantities of trajectory data are collected from many sources, such as GPS devices and mobile phones, as sequences of spatio‐temporal points. These data can be used in many application domains such as traffic management, urban planning, tourism, bird migration, and so on. Raw trajectory data, as generated by mobile devices have very little or no semantics, and in most applications a higher level of abstraction is needed to exploit these data for decision making. Although several different methods have been proposed so far for trajectory querying and mining, there are no software tools to help the end user with semantic trajectory data analysis. In this article we present a software architecture for semantic trajectory data mining as well as the first software prototype to enrich trajectory data with both semantic information and data mining. As a prototype we extend the Weka data mining toolkit with the module Weka‐STPM, which is interoperable with databases constructed under OGC specifications. We tested Weka‐STPM with real geographic databases, and trajectory data stored under the Postgresql/PostGIS DBMS.