The application of elemental fingerprinting techniques to identify population connectivity using austrovenus stutchburyi recruits

The density, distribution and dynamics of benthic bivalve populations are believed to be largely determined by the planktonic larval phase of the life history. As the hard parts of larvae, such as the prodissoconch (larval shell), develop and grow, ambient environmental conditions are recorded as chemical signatures (elemental fingerprints). If the chemical signals of reference sites are known, the larval signatures can be matched to reference sites, hereby reconstructing the origin of the larvae. The collection and identification of larval bivalves is extremely difficult, however, previous studies have shown that the prodissoconch is retained into the juvenile phase, thus enabling juveniles to maintain a record of the larval movement. Before elemental fingerprinting can be used as a larval tracking tool, site specific signatures must be evident in the shells. As a precursor study to test the application of elemental fingerprinting to track bivalve larvae, the presence of spatial variability in shell signatures as well as the scale at which these variations occurred, were established for New Zealand conditions. Furthermore, temporal stability of the shell signatures was explored, as temporal stability is crucial if the signals of shells collected at one time are to be used as predictors of unknown samples collected at a different time. The venerid bivalve Austrovenus stutchburyi is a common and widespread constituent of New Zealand estuarine communities and were therefore selected as the study species. The chemical signatures of entire Austrovenus stutchburyi shells were examined to determine the inter-site spatial differences in elemental fingerprints of shells and also to characterise the temporal stability of the signatures. Furthermore, shells were ablated at two reference points (the prodissoconch and most recently formed shell material) to determine the intra-shell variation in the chemical signatures. Juvenile individuals were collected from 19 sites in the North Island of New Zealand as part of the whole shell spatial study. One site (in Tauranga Harbour) was examined for the temporal study, whilst four sites were used to compare intra-shell chemical variation. Whole shells were digested and analysed as solution based samples using inductively coupled ii ABSTRACT iii plasma-mass spectrometry (ICP-MS) for the spatial and temporal studies, and by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) for the point ablation intra-shell variation study. Results showed that shell concentrations were sufficiently different to yield a classification success of 68% over 19 sites, however the classification success markedly increased as the number of sites included in the analysis decreased (e.g. 12 sites = 75%, 10 sites = 84%, 5 sites = 90%, 3 sites = 95%). Shells were successfully classified across all of the spatial scales that were tested (approximately 10 km to 1150 km). Temporal stability in chemical signatures was observed over a 44 day period. The chemical signatures were not correlated with ambient temperature or salinity, however more vigorous sampling is needed to accurately assess the relationship between shell elemental incorporation and environmental conditions. Intra-shell variation was also observed for some of the shells analysed from two of the four sites. These results were promising and indicated that there may be chemical variations between the larval shells and the more recently formed shell material, thus suggesting the possibility of external recruitment. The results from this study emphasised the potential for the application of elemental fingerprinting techniques to track and better understand the larval transport and population connectivity for New Zealand invertebrate species, however more research is required before elemental fingerprinting can effectively be applied to New Zealand invertebrate species. With a fundamental understanding of the origin of bivalve recruits, restoration efforts following estuarine disturbance events can be effectively employed

Research into RCM using the case of Hidrovía: Practical use in the Aid to Navigation sector

Additional thesis - This thesis looks into the use of the Reliability Centred Maintenance in practice, by applying the methodology in a real life case, analysing the maintenance department of the organisation Hidrovía S.A.. Nowadays Hidrovía S.A. is maintaining the aid to navigation of the main river in Argentina, a concession given by the national government of maintaining and dredging more than 1500 km of waterway. The aid to navigation can be divided in roughly three types: buoy, beacon and spar, which they mainly hold up by using corrective maintenance. This could positively be changed by adapting some maintenance strategies. Using a Fault Tree Analysis and Failure Mode Effect Analysis during the RCM process, a few things were noticed; the three types of Aid to Navigation (AtoN) have a lot different sub components in common, the buoy has the highest failure rate and within the buoy there are six critical sub components: the top mark, lantern, battery (case), solar panel, floating system and chain. These six critical sub components could gain more reliability by adapting the maintenance policy: scheduled maintenance of the lantern, battery case and solar panel, redesign of the floating system and a combined strategy (preventive and scheduled maintenance) for the chain. In order to give a real maintenance policy adaptation, unfortunately more information is needed. More research should be done in the possibility of combining the scheduled replacement with the preventive maintenance and the redesigned buoys replacement. Also, the feasibility of the redesignitself should be looked into.Civil Engineering and GeosciencesHydraulic EngineeringConstruction Management and Engineerin

Double trouble in the South Pacific subtropical gyre: increased plastic ingestion by fish in the oceanic accumulation zone

International audienceFish are an important food source for South Pacific (SP) island countries, yet there is little information on contamination of commercial marine fish species by plastic. The aim of our study was to perform a broad-scale assessment of plastic ingestion by fish common in the diet of SP inhabitants. We examined 932 specimens from 34 commercial fish species across four SP locations, and some of the prey they ingested, for the presence of marine plastics. Plastic was found in 33 species, with an average ingestion rate (IR) of 24.3 +/- 1.4% and plastic load of 2.4 +/- 0.2 particles per fish. Rapa Nui fish exhibited the greatest IR (50.0%), significantly greater than in other three locations. Rapa Nui is located within the SP subtropical gyre, where the concentration of marine plastics is high and food is limited. Plastic was also found in prey, which confirms the trophic transfer of microplastics

Macrofaunal metadata.

<p>Differences between the <i>Austrovenus</i> and <i>Macomona</i> sites in terms of infaunal species richness, functional group richness (FG), Shannon diversity index forspecies (H’SP) and functional groups (H’FG), total density of individuals and the density of the key FG, (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0158785#pone.0158785.t001" target="_blank">Table 1</a> for explanations to abbreviations). Values are mean ± 1 SD. Headings in bold are predictors for statistical analyses.</p

Per capita uptake (δ¹⁵N enrichment in individual species) in relation to species and functional group (FG) density and diversity indices.

<p>Species are represented by different symbols. All species are from the <i>Austrovenus</i> site except for <i>M</i>. <i>liliana</i> and <i>S</i>. <i>cylindrifer</i> in the bottom panels. Both uptake and densities are square-root transformed. Only significant relationships (p<0.05) according to marginal tests in DistLM are shown. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0158785#pone.0158785.t006" target="_blank">Table 6</a> for details on the statistical models and Tables <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0158785#pone.0158785.t001" target="_blank">1</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0158785#pone.0158785.t002" target="_blank">2</a> for definitions of abbreviations.</p

Infaunal community biomass and uptake of <i>Ulva</i>-derived nitrogen.

<p>Community biomass (shell-free dry weight) (A) and community uptake of macroalgal nitrogen (B) with the species contributing most at each site shown. Values are mean ± 1 SD.</p

Species and functional group assignment.

<p>Each species was assigned to a functional group (FG) based on Greenfield et al.[<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0158785#pone.0158785.ref047" target="_blank">47</a>]. Densities of FGs in bold (1–6) were included as explanatory variables in statistical analyses. Only adult specimens of <i>S</i>. <i>cylindrifer</i>, <i>M</i>. <i>liliana</i> and <i>A</i>. <i>stuchburyi</i> were included in the FG, as juveniles were expected to confound possible density effects. For <i>Naineris</i> sp. only juveniles were found. Species in bold were selected for isotope analyses and used as response variables in separate statistical tests. Underlined species were screened for isotope enrichment (per capita uptake) but not included in statistical analyses because of insufficient enrichment (e.g. <i>A</i>. <i>stutchburyi</i>) or low abundance.</p

‘Best’ model of total community uptake of <i>Ulva</i>-derived nitrogen.

<p>Results from the ‘best’ model selection procedure for different numbers of predictor variables at the <i>Austrovenus</i> site, <i>Macomona</i> site and both sites pooled (biomass normalized). AICc denote corrected Akaike information criterion and R² is the total cumulative variance explained by the model. See Tables <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0158785#pone.0158785.t001" target="_blank">1</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0158785#pone.0158785.t002" target="_blank">2</a> for definitions of other abbreviations.</p

Predictors of total community uptake of <i>Ulva</i>-derived nitrogen.

<p>DistLM marginal test results reporting the proportion of total community N uptake at the <i>Austrovenus</i> (n = 41) and <i>Macomona</i> (n = 29) sites and both sites combined (biomass normalized) explained by diversity indices and FG densities (see Tables <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0158785#pone.0158785.t001" target="_blank">1</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0158785#pone.0158785.t002" target="_blank">2</a> for abbreviation definitions). Marginal tests results describe how much variation each variable explains when considered alone, ignoring other variables. The (+) or (-) sign denote direction of the relationship, na = non-applicable predictor. Significant relationships are shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0158785#pone.0158785.g004" target="_blank">Fig 4</a>.</p