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    ABSTRACT: Large scale surveys for cetaceans: Line transect assumptions, reliability of abundance esti-mates and improving survey efficiency – A response to MacLeod MacLeod (2014) criticises the design of the 2005 SCANS-II sur-vey of cetaceans in European Atlantic waters (Hammond et al., 2013) for failing to assess some underlying assumptions of line transect (distance) sampling. The basis of his argument can be summarised as: white-beaked dolphins are patchily distributed over the SCANS-II survey area; the survey design does not reflect this distribution; therefore this violates distance sampling assumptions. He concludes that the estimates for white-beaked dolphin ''should not be used for any conservation purpose, includ-ing assessments of the conservation status of this species. Similar issues may also exist with the abundance estimates of other spe-cies generated from the SCANS-II surveys''. The conclusions are strong but the basic argument presented to support these state-ments is flawed. MacLeod (2014) states that the SCANS-II surveys ''were de-signed based on the spatial distribution of a single species''. This is incorrect. As stated in Hammond et al. (2013), our survey blocks were chosen primarily for logistical reasons and transect lines within them were generated using a systematic design with ran-dom starting points designed to give equal coverage probability within blocks. The random component of transect placement is fundamental to any line transect survey. Equal coverage probabil-ity survey designs, as implemented in the SCANS-II survey, are used specifically to avoid making any assumptions about the dis-tribution of animals, which is typically unknown, and to ensure that estimates of abundance are design-unbiased. MacLeod (2014) also draws attention to the known presence of white-beaked dolphins in survey block B in which no animals were detected on the SCANS-II survey, leading to abundance being esti-mated (not assumed, as he states) to be zero. He interprets this as evidence of ''the inappropriateness of the SCANS II survey design for estimating the abundance of a species with a patchy and dis-continuous distribution''. If ''inappropriateness'' is replaced by ''inefficiency'', and ''at small spatial scales'' is added as a qualifier, we agree. Large scale surveys like SCANS-II have low coverage probability and are not designed to capture small-scale features in distribution and abun-dance, especially in areas of low abundance and/or patchy distri-bution. Uncertainty in the abundance estimates given in Hammond et al. (2013) is reflected in the estimated coefficients of variation, which are high for individual survey blocks; fine scale inferences should not be made from the results, as stated in the pa-per. Local populations of cetaceans can be monitored at such smal-ler scales using appropriate techniques (e.g. Cheney et al., 2013). These points neither invalidate the design-based estimates of abundance in Hammond et al. (2013), nor preclude reliable infer-ence at a large spatial scale, the purpose of our surveys. If, as MacLeod (2014) describes for the white-beaked dolphin, there is prior knowledge of distribution of a particular species then survey efficiency and precision of abundance estimates for this spe-cies would be improved if survey blocks could be created to mini-mise variation in density within blocks. Such focused stratification can be good practice and can potentially provide more precise esti-mates of abundance. However, in multispecies survey such as SCANS-II this is difficult to achieve for all species because the most efficient selection of survey blocks for one species is unlikely to be the most efficient for others. Nonetheless, as knowledge of cetacean distribution improves through small scale surveys, such as those al-luded to by Macleod (2014), it will be important to take this informa-tion into account in designing future large scale surveys; this will be done in planning for a potential SCANS-III survey in 2016. Macleod (2014) states that, for the white-beaked dolphin, ''the discrepancies between the SCANS-II abundance estimates and other, more extensive, survey data for individual survey blocks are readily identifiable'' but presents no information to support this. To our knowledge, there are no other recent estimates of white-beaked dolphin abundance in the SCANS-II area. If the more extensive survey data alluded to by MacLeod (2014) were analysed to estimate abundance, this information could also be considered by EU Member States when reporting to the European Commission under Article 17 of the Habitats Directive. Macleod (2014) suggests that the SCANS-II data should be reanalysed using post-survey re-stratification. Post-stratification of data from a survey that implemented equal coverage probability sampling within blocks would likely violate the assumptions of the design and is inadvisable. However, model-based abundance esti-mation methods that relate sample density to spatially explicit envi-ronmental covariates (so-called density surface modelling) do not make the same assumptions about survey design and can poten-tially provide more precise estimates of abundance. Model-based methods come with their own assumptions, but such a re-analysis of SCANS-II data together with ''other, more extensive, survey data'' alluded to by Macleod (2014) could be an informative exercise. We refute that the estimates of abundance in our paper are unreliable and should not be used for any conservation purpose. On the contrary, by using the necessary sampling design for unbi-ased estimation, large scale SCANS-type surveys and the estimates of abundance that they generate contribute important information that helps Member States meet their responsibilities with respect to cetaceans under the EU Habitats Directive and Marine Strategy Framework Directive.
    Biological Conservation 02/2014; 170. DOI:10.1016/j.biocon.2014.01.016
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    ABSTRACT: In laboratory-based biofouling assays, the influence of physico-chemical surface characteristics on barnacle settlement has been tested most frequently using the model organism Balanus amphitrite (= Amphibalanus amphitrite). Very few studies have addressed the settlement preferences of other barnacle species, such as Balanus improvisus (= Amphibalanus improvisus). This study aimed to unravel the effects of surface physico-chemical cues, in particular surface-free energy (SFE) and surface charge, on the settlement of cyprids of B. improvisus. The use of well-defined surfaces under controlled conditions further facilitates comparison of the results with recent similar data for B. amphitrite. Zero-day-old cyprids of B. improvisus were exposed to a series of model surfaces, namely self-assembled monolayers (SAMs) of alkanethiols with varying end-groups, homogenously applied to gold-coated polystyrene (PS) Petri dishes. As with B. amphitrite, settlement of cyprids of B. improvisus was influenced by both SFE and charge, with higher settlement on low-energy (hydrophobic) surfaces and negatively charged SAMs. Positively charged SAMs resulted in low settlement, with intermediate settlement on neutral SAMs of similar SFE. In conclusion, it is demonstrated that despite previous suggestions to the contrary, these two species of barnacle show similar preferences in response to SFE; they also respond similarly to charge. These findings have positive implications for the development of novel antifouling (AF) coatings and support the importance of consistency in substratum choice for assays designed to compare surface preferences of fouling organisms.
    Biofouling 12/2013; DOI:10.1080/08927014.2013.852541
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    Marine Pollution Bulletin 11/2013; 76(1-2):1-2. DOI:10.1016/j.marpolbul.2013.10.015
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    ABSTRACT: This study presents detailed and rigorous numerical analysis for a parametric series of unstiffened aluminium plates typical of those used in lightweight ships and equivalent thin walled stiffened structures. The study is undertaken with a nonlinear finite element analysis procedure using ABAQUS. The strength behaviour of the plates under a progressively increasing longitudinal in-plane load are shown to be affected by a number of parameters including the alloy, geometric imperfection shape, heat affected zone distribution, level of heat softening and residual stress distribution. The comparative influences of these various factors, some of which are specific to welded aluminium structure, are explored to determine which must be accounted for in the development of a parametric series of design curves.
    Thin-Walled Structures 09/2013; 70:19–32. DOI:10.1016/j.tws.2013.04.006
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    ABSTRACT: We examined the impacts of ocean acidification and copper as co-stressors on the reproduction and population level responses of the benthic copepod Tisbe battagliai across two generations. Naupliar production, growth, and cuticle elemental composition were determined for four pH values: 8.06 (control); 7.95; 7.82; 7.67, with copper addition to concentrations equivalent to those in benthic pore waters. An additive synergistic effect was observed; the decline in naupliar production was greater with added copper at decreasing pH than for decreasing pH alone. Naupliar production modelled for the two generations revealed a negative synergistic impact between ocean acidification and environmentally relevant copper concentrations. Conversely, copper addition enhanced copepod growth, with larger copepods produced at each pH compared to the impact of pH alone. Copepod digests revealed significantly reduced cuticle concentrations of sulphur, phosphorus and calcium under decreasing pH; further, copper uptake increased to toxic levels that lead to reduced naupliar production. These data suggest that ocean acidification will enhance copper bioavailability, resulting in larger, but less fecund individuals that may have an overall detrimental outcome for copepod populations.
    PLoS ONE 08/2013; 8(8):e71257. DOI:10.1371/journal.pone.0071257
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    ABSTRACT: Ficopomatus enigmaticus, a euryhaline tube-building polychaete worm with a subtropical to temperate distribution, is an increasingly problematic fouling organism. In this study, laboratory protocols for maintaining adult broodstock, destructive spawning, larval culture and a settlement bioassay were developed. The method routinely yielded approximately 200 larvae per spawning adult. The mean number of eggs released by females was 1517 and the mean number of spermatozoids per male was 4.425 × 106. Fertilisation success, using an initial concentration of 2.5 × 106 spermatozoids and 45 eggs ml−1, was 76% after a contact time of 60 min. The first cleavage occurred after 20 min and the trocophore larval stage was attained by 18 h. Metatrochophores were observed 4 d post-fertilisation and were competent to settle 1 day later. The proportion of larvae that settled after 48 h was surface-dependent: 10.24% on glass, 1.39% on polystyrene and 11.07% on a poly(dimethylsiloxane) elastomer. The presence of a biofilm on glass increased the rate of settlement 7-fold compared to clean glass.
    Biofouling 07/2013; 29(7):869-878. DOI:10.1080/08927014.2013.810214
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    ABSTRACT: When exploring immersed surfaces the cypris larvae of barnacles employ a tenacious and rapidly reversible adhesion mechanism to facilitate their characteristic 'walking' behaviour. Although of direct relevance to the fields of marine biofouling and bio-inspired adhesive development, the mechanism of temporary adhesion in cyprids remains poorly understood. Cyprids secrete deposits of a proteinaceous substance during surface attachment and these are often visible as 'footprints' on previously explored surfaces. The attachment structures, the antennular discs, of cyprids also present a complex morphology reminiscent of both the hairy appendages used by some terrestrial invertebrates for temporary adhesion and a classic 'suction cup'. Despite the numerous analytical approaches so-far employed, it has not been possible to resolve conclusively the respective contributions of viscoelastic adhesion via the proteinaceous 'temporary adhesive', 'dry' adhesion via the cuticular villi present on the disc and the behavioural contribution by the organism. In this study, high-speed photography was used for the first time to capture the behaviour of cyprids at the instant of temporary attachment and detachment. Attachment is facilitated by a constantly sticky disc surface - presumably due to the presence of the proteinaceous temporary adhesive. The tenacity of the resulting bond, however, is mediated behaviourally. For weak attachment the disc is constantly moved on the surface, whereas for a strong attachment the disc is spread out on the surface. Voluntary detachment is by force, requiring twisting or peeling of the bond - seemingly without any more subtle detachment behaviours. Micro-bubbles were observed at the adhesive interface as the cyprid detached, possibly an adaptation for energy dissipation. These observations will allow future work to focus more specifically on the cyprid temporary adhesive proteins, which appear to be fundamental to adhesion, inherently sticky and exquisitely adapted for reversible adhesion underwater.
    PLoS ONE 07/2013; 8(7):e68085. DOI:10.1371/journal.pone.0068085
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    ABSTRACT: The hydrothermal vents on the East Scotia Ridge are the first to be explored in the Antarctic and are dominated by large peltospiroid gastropods, stalked barnacles (Vulcanolepas sp.) and anomuran crabs (Kiwa sp.) but their food webs are unknown. Vent fluid and macroconsumer samples were collected at three vent sites (E2, E9N and E9S) at distances of tens of metres to hundreds of kilometres apart with contrasting vent fluid chemistries to describe trophic interactions and identify potential carbon fixation pathways using stable isotopes. δ(13)C of dissolved inorganic carbon from vent fluids ranged from -4.6‰ to 0.8‰ at E2 and from -4.4‰ to 1.5‰ at E9. The lowest macroconsumer δ(13)C was observed in peltospiroid gastropods (-30.0‰ to -31.1‰) and indicated carbon fixation via the Calvin-Benson-Bassham (CBB) cycle by endosymbiotic gamma-Proteobacteria. Highest δ(13)C occurred in Kiwa sp. (-19.0‰ to -10.5‰), similar to that of the epibionts sampled from their ventral setae. Kiwa sp. δ(13)C differed among sites, which were attributed to spatial differences in the epibiont community and the relative contribution of carbon fixed via the reductive tricarboxylic acid (rTCA) and CBB cycles assimilated by Kiwa sp. Site differences in carbon fixation pathways were traced into higher trophic levels e.g. a stichasterid asteroid that predates on Kiwa sp. Sponges and anemones at the periphery of E2 assimilated a proportion of epipelagic photosynthetic primary production but this was not observed at E9N. Differences in the δ(13)C and δ(34)S values of vent macroconsumers between E2 and E9 sites suggest the relative contributions of photosynthetic and chemoautotrophic carbon fixation (rTCA v CBB) entering the hydrothermal vent food webs vary between the sites.
    PLoS ONE 06/2013; 8(6):e65553. DOI:10.1371/journal.pone.0065553
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    ABSTRACT: Methane production by anaerobic digestion (AD) of macroalgae (seaweed) is a promising algal bioenergy option. Work presented here is primarily based on the AD of Laminaria hyperborea using batch and continuously stirred tank reactors. Extrapolation of data from batch studies to long term continuous reactors was unreliable. A conservative organic loading rate (OLR) of 1gL(-1)d(-1) was used due to difficulties experienced in achieving steady state performance at an OLR of 1.5gL(-1)d(-1). Biogas composition and methane yields (60-70%) were near to values expected from terrestrial feedstocks. Biomass washout, as imposed by the dilution rate (i.e., hydraulic residence), had considerable bearing on the biogas generation profile, particularly at >3 hydraulic residences. Inhibition of methanogen growth was linked to nutrient deficiency and potentially antimicrobial compounds associated with the feedstock. Anaerobic digestion of L. hyperborea proved feasible over extended operational periods.
    Bioresource Technology 06/2013; 143C:221-230. DOI:10.1016/j.biortech.2013.05.124
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    ABSTRACT: The progressive collapse of a box beam under longitudinal bending can be predicted using various computational approaches, including finite element methodologies and the simplified progressive collapse method. These methodologies are employed to complete a series of analyses on three small box girders. The models are first analysed in the intact condition and then several damage scenarios are investigated. The results from the different computational approaches are compared to determine their relative performance. The study demonstrates the significance of residual stresses that are created during the damage simulation and are represented using differing assumptions in each of the compared methodologies.
    Engineering Structures 03/2013; 48:266–280. DOI:10.1016/j.engstruct.2012.09.031
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