Multi-species Approach Research Articles

Finite Mixture of Regression Modeling for High-Dimensional Count and Biomass Data in Ecology

Understanding how species distributions respond as a function of environmental gradients is a key question in ecology, and will benefit from a multi-species approach. Multi-species data are often high dimensional, in that the number of species sampled is often large relative to the number of sites, and are commonly quantified as either presence–absence, counts of individuals, or biomass of each species. In this paper, we propose a novel approach to the analysis of multi-species data when the goal is to understand how each species responds to their environment. We use a finite mixture of regression models, grouping species into “Archetypes” according to their environmental response, thereby significantly reducing the dimension of the regression model. Previous research introduced such Species Archetype Models (SAMs), but only for binary assemblage data. Here, we extend this basic framework with three key innovations: (1) the method is expanded to handle count and biomass data, (2) we propose grouping on the slope coefficients only, whilst the intercept terms and nuisance parameters remain species-specific, and (3) we develop model diagnostic tools for SAMs. By grouping on environmental responses only, the model allows for inter-species variation in terms of overall prevalence and abundance. The application of our expanded SAM framework data is illustrated on marine survey data and through simulation.

Molecular characterization of serotype O foot-andmouth disease virus from pigs: Implications for multispecies approach to disease control in Uganda

In Uganda, where foot-and-mouth disease (FMD) control is mainly done through vaccination, constant monitoring of outbreaks and phylogenetic studies are important in designing effective disease control strategies. These efforts however, have mainly concentrated on cattle since they are the main visible disease hosts. In this study, the molecular characteristics of the VP1 coding sequences of the pigderived FMD virus and its phylogenetic relationship with other historical Ugandan FMD virus sequences are determined. Sixty seven samples were collected from three districts of south western Uganda and subjected to RT-PCR. Partial VP1 capsid protein coding sequences of 12 positive samples were amplified and sequenced using serotype specific primers. Eight sequences were successfully obtained, all of which were from domestic pigs. All samples were confirmed as belonging to serotype O using BLAST search. Phylogenetic analysis of the test sequences with selected sequences, showed a close relatedness (average of 3.77% pair-wise distance) to viruses isolated from central and western Uganda in the years 2005 and 2006 from cattle. These results show that domestic pigs in the western region of Uganda have been infected with the same circulating strain of FMDV and play a potentially important role in FMD maintenance and spread. Keywords : Foot-and-mouth disease (FMD), pig-derived FMDV sequence, persistence, domestic pigs African Journal of Biotechnology Vol. 12(19), pp. 2547-2552

Fine-scale biogeography: tidal elevation strongly affects population genetic structure and demographic history in intertidal fishes

Numerous studies have demonstrated population genetic structuring in marine species, yet few have investigated the effect of vertical zonation on gene flow and population structure. Here we use three sympatric, closely related clinid species, Clinus cottoides, C. superciliosus and Muraenoclinus dor- salis, to test whether zonation on South African intertidal rocky sho res affects phylogeographic patterns. We show that the high-shore restricted species has reduced gene flow and considerably higher FST val- ues (FST = 0.9) than the mid- and low-shore species (FST < 0.14). Additionally, we provide evidence for remarkably different demographic and evolutionary histories, ranging from extreme population bottle- necks to population persistence, which are probably linked to effective population size and habitat spe- cialisation. This study further highlights the need for a multispecies approach to unravel the biological and evolutionary processes that drive extant population geneti c patterns in marine species, as even closely related species with similar life histories show highly variable results.

English

The evaluation of road-kill spatial patterns is an important tool to identify priority locations for mitigation measures aiming to reduce wildlife mortality on roads. Single target or multi-species approaches are usually adopted to implement such measures, although their success must be evaluated. We aim to test if road-kill hotspots are coincident among different vertebrate groups. If this is true, data on accidents from one group could be used to plan measures applicable to other groups. We identified hotspots using five different grouping criteria: vertebrate classes (reptiles, mammals or birds), body size (large or small), species commonness (common or rare), type of locomotion (flying or non-flying), and time of activity (preferably nocturnal/crepuscular or diurnal). We analyzed data from road-kill surveys on four roads in southern Brazil, each one with at least one year of monitoring. Using SIRIEMA software, we performed a modified Ripley's K statistic to recognize scales of road-kill aggregation and we carried out Hotspot analyses to identify the location of road-kill aggregations for each group described above in each road. To test for similarity in hotspot location among different groups we performed an association test using correlation as resemblance measure. Hotspot analyses and association tests were done using different scales to evaluate scale effect on similarities. Correlation results between groups presented low values in small scales although had a tendency to increase with increasing scales. Our results show that road-kill hotspots are different among groups, especially when analyzed in small scales. We suggest that, for a successful biodiversity approach in mitigation, one should first select general hotspots in large scales and then identify specific hotspots in small scales to implement specific measures. These findings are relevant in a context of road networks already implemented, where mitigation measures are being planned to reduce their impact on wildlife.

Assessing Regional and Interspecific Variation in Threshold Responses of Forest Breeding Birds through Broad Scale Analyses

BackgroundIdentifying persistence and extinction thresholds in species-habitat relationships is a major focal point of ecological research and conservation. However, one major concern regarding the incorporation of threshold analyses in conservation is the lack of knowledge on the generality and transferability of results across species and regions. We present a multi-region, multi-species approach of modeling threshold responses, which we use to investigate whether threshold effects are similar across species and regions.Methodology/Principal FindingsWe modeled local persistence and extinction dynamics of 25 forest-associated breeding birds based on detection/non-detection data, which were derived from repeated breeding bird atlases for the state of Vermont. We did not find threshold responses to be particularly well-supported, with 9 species supporting extinction thresholds and 5 supporting persistence thresholds. This contrasts with a previous study based on breeding bird atlas data from adjacent New York State, which showed that most species support persistence and extinction threshold models (15 and 22 of 25 study species respectively). In addition, species that supported a threshold model in both states had associated average threshold estimates of 61.41% (SE = 6.11, persistence) and 66.45% (SE = 9.15, extinction) in New York, compared to 51.08% (SE = 10.60, persistence) and 73.67% (SE = 5.70, extinction) in Vermont. Across species, thresholds were found at 19.45–87.96% forest cover for persistence and 50.82–91.02% for extinction dynamics.Conclusions/SignificanceThrough an approach that allows for broad-scale comparisons of threshold responses, we show that species vary in their threshold responses with regard to habitat amount, and that differences between even nearby regions can be pronounced. We present both ecological and methodological factors that may contribute to the different model results, but propose that regardless of the reasons behind these differences, our results merit a warning that threshold values cannot simply be transferred across regions or interpreted as clear-cut targets for ecosystem management and conservation.

Bird flu biopower: Strategies for multispecies coexistence in Việt Nam

ABSTRACTOutbreaks of SARS, swine flu, and avian influenza have prompted a “One Health” effort to control diseases transmitted between species. Using ethnographic observations from Việt Nam, I reveal how avian flu transforms strategies for living in light of human vulnerability to animals. Positing a multispecies approach to biopower, I argue that techniques for safeguarding human–animal collectivities confront heterogeneous moral codes surrounding animals’ role in knowledge hierarchies, village economies, and notions of individual worth. This analysis provides a framework for reconceptualizing biopower in relation to emerging diseases and reenvisions the role of animals in the politics of life itself.

Managing California’s Water: Insights from Interviews with Water Policy Experts

This paper presents insights from interviews with over 100 California water policy experts, who answered open-ended questions regarding California’s long-term water policy challenges and potential solutions. Interviews were conducted in the spring and summer of 2010, and interviewees were selected from a range of sectors and regions within California. Top long-term policy problems cited include management of the Sacramento–San Joaquin Delta, dysfunctional institutions and water governance, unsustainable water supplies and flood management, poor environmental protection, and problems with water rights and valuing water. In addition to a range of specific management solutions, respondents emphasized the importance of public education, incentivized cooperation, more holistic water management, local innovation, and removal of regulatory obstacles as primary solutions to California’s long-term water challenges. There was little emphasis on new surface storage projects, except from politicians. Other respondents preferred local and regional approaches to improve water supply, such as conservation, groundwater banking, recycling, or stormwater management. Despite differences in opinion on the problems with implementation of the Endangered Species Act, there was broad agreement that environmental management approaches need to shift away from single-species, piecemeal approaches toward ecosystem-based, multi-species approaches.

Bioinformatics approach for data management about bone cells grown on substitute materials

Motivation and Objectives Tissue engineering, the research field aimed at finding high technological biomaterials able to restore, maintain, or improve tissue function, concentrates many efforts in the contest of bone and cartilage, due to their possible wide-spread clinical applications. The main target is the design of well performing scaffolds suitable to promote the development of natural tissue in implant conditions, without generating rejection and, hopefully, degrading in vivo at the same rate of tissue formation. Concerning both bone and cartilage, one of the most important research aspects is determining the biochemical and topological factors that induce cell differentiation and tissue ingrowth. The scaffold material composition is crucial and many of them have been already tested, including alginate (Duggal et al., 2009), collagen/chitosan (Ravindran et al., 2012), polycaprolactone (PCL) and hydroxyapatite (HA) (Scaglione et al., 2010), Poly-L-Lactide Acid (PLLA) (Ciapetti et al., 2012), polymethylmethacrylate (BombonatoPrado et al., 2007), bioactive glasses (Leven et al., 2004), carbon nanotubes (Van der Zande et al., 2004), etc. To better evaluate material performance, the biomolecular characterization of the cellular response is becoming a common practice among researchers. Nonetheless, experimental data usually remain sparse in literature: the collection of high-throughput gene expression profiles from samples on different materials could allow data comparisons and formulation of new hypotheses about the effectiveness of bone/cartilage substitute. In this context authors extended the existing OsteoChondroDB database (Viti et al., 2012), which collects data and metadata from microarray gene expression of cells cultured in different conditions onto diverse materials, and allows analyzing differentially expressed genes (DEG) from the available knowledge base. Methods The OsteoChondroDB relies on MySQL database, while the web interface has been developed using php and javascript technologies, and this improved version of the systems is based on the same infrastructure. Manual research has been performed on papers containing biomolecular data about osteochondral tissue developed on different scaffolds. Data have been retrieved from known public repositories such as Gene Expression Omnibus (http://www.ncbi.nlm.nih.gov/geo/) and ArrayExpress (http://www.ebi.ac.uk/arrayexpress/), whenever experiments were available, or directly contacting papers authors. The amount of data produced in this field is new, scarce, and variegated, although the importance of biomolecular aspects related to the tissue growth on materials can be of great importance to design improved scaffolds. To exploit the available data in an integrated fashion, the strategy described by Kodama et al. (Kodama et al., 2012) appears useful, because it proposes a multi-species and multi-platform approach for gene expression microarray data meta-analysis. In this way, it is possible to increase the number of evidences, by considering mouse and rat data together with human experiments and by mixing different versions, brands and designs of microarray chips. The information mapping between species can be performed through AILUN system (Chen R et al., 2007), which converts ids of different platforms.

Increase in Carbohydrate Utilization in High-Altitude Andean Mice

The low oxygen levels at high altitude are a potent and unavoidable physiological stressor to which highland mammals must adapt. One hypothesized adaptation to high altitude is an increased reliance on carbohydrates to support aerobic activities. Based on stoichiometries of combustion, ATP yield per mole of oxygen from carbohydrates is approximately 15% higher than from lipids (observed difference closer to 30%), and increased carbohydrate use represents an important oxygen-saving strategy that may be under high selective pressure. Although this hypothesis was first proposed nearly 30 years ago, the in vivo patterns of whole-body fuel use during exercise remain undefined for any highland mammal (including humans). Here we use a powerful multispecies approach to show that wild-caught high-altitude (4,000-4,500 m) native species of mice (Phyllotis andium and Phyllotis xanthopygus) from the Peruvian Andes use proportionately more carbohydrates and have higher oxidative capacities of cardiac muscles compared to closely related low-altitude (100-300 m) native counterparts (Phyllotis amicus and Phyllotis limatus). These results strongly infer that highland Phyllotis have evolved a metabolic strategy to economize oxygen when performing energy-demanding tasks at altitude. This study provides compelling evidence of adjustments in fuel use as an adaptation to high-altitude hypoxia in mammals.

Genetic diversity in widespread species is not congruent with species richness in alpine plant communities

The Convention on Biological Diversity (CBD) aims at the conservation of all three levels of biodiversity, that is, ecosystems, species and genes. Genetic diversity represents evolutionary potential and is important for ecosystem functioning. Unfortunately, genetic diversity in natural populations is hardly considered in conservation strategies because it is difficult to measure and has been hypothesised to co-vary with species richness. This means that species richness is taken as a surrogate of genetic diversity in conservation planning, though their relationship has not been properly evaluated. We tested whether the genetic and species levels of biodiversity co-vary, using a large-scale and multi-species approach. We chose the high-mountain flora of the Alps and the Carpathians as study systems and demonstrate that species richness and genetic diversity are not correlated. Species richness thus cannot act as a surrogate for genetic diversity. Our results have important consequences for implementing the CBD when designing conservation strategies.

What Controls Connectivity? An Empirical, Multi-Species Approach

The exchange of individuals among habitat patches (connectivity) has broad relevance for the conservation and management of marine metapopulations. Elemental fingerprinting-based research conducted over the past 12 years along the open coastline and bays of San Diego County in southern California evaluated connectivity patterns for seven species: one native and two invasive mussels, an oyster, a brachyuran crab, and two fishes. The studies spanned different years and seasons but overlapped considerably in space, allowing comparisons of dispersal patterns across species, and assessment of the relative importance of location, circulation, and intra-annual and inter-annual variability. We asked whether the species exhibited commonalities in directional transport, transport distances, sources and sinks, self-recruitment, and bay-ocean exchange. Linked connectivity-demographic analyses conducted for two species of mytilid mussels and two fishes allowed evaluation of the contributions of realized connectivity to metapopulation dynamics relative to other life-history attributes. Common trends across species include average along-shore dispersal distances of 15-35 km and seasonal changes in direction of dispersal that mirrored patterns of along-shore circulation. We observed greater isolation of back-bay populations, significant exchange from front bay to ocean, and high self-recruitment in locations on the northern, open coast, and in the southern bays. Connectivity was rarely the most influential driver of growth and persistence of metapopulations, but influenced the importance of other vital rates. Several locations served consistently as sources of larvae or as nurseries for multiple species, but there were few sites in common that were sinks. For the mussels, reproductive timing guided directional transport. These results imply that local management (e.g., habitat protection, opening of the mouths of lagoons, location of aquaculture farms) may be effective along this coastline. Regional, multi-species assessments of exchange of larvae should move us closer to ecosystem-based management.

Hierarchical multi-species modeling of carnivore responses to hunting, habitat and prey in a West African protected area.

Protected areas (PAs) are a cornerstone of global efforts to shield wildlife from anthropogenic impacts, yet their effectiveness at protecting wide-ranging species prone to human conflict – notably mammalian carnivores – is increasingly in question. An understanding of carnivore responses to human-induced and natural changes in and around PAs is critical not only to the conservation of threatened carnivore populations, but also to the effective protection of ecosystems in which they play key functional roles. However, an important challenge to assessing carnivore communities is the often infrequent and imperfect nature of survey detections. We applied a novel hierarchical multi-species occupancy model that accounted for detectability and spatial autocorrelation to data from 224 camera trap stations (sampled between October 2006 and January 2009) in order to test hypotheses about extrinsic influences on carnivore community dynamics in a West African protected area (Mole National Park, Ghana). We developed spatially explicit indices of illegal hunting activity, law enforcement patrol effort, prey biomass, and habitat productivity across the park, and used a Bayesian model selection framework to identify predictors of site occurrence for individual species and the entire carnivore community. Contrary to our expectation, hunting pressure and edge proximity did not have consistent, negative effects on occurrence across the nine carnivore species detected. Occurrence patterns for most species were positively associated with small prey biomass, and several species had either positive or negative associations with riverine forest (but not with other habitat descriptors). Influences of sampling design on carnivore detectability were also identified and addressed within our modeling framework (e.g., road and observer effects), and the multi-species approach facilitated inference on even the rarest carnivore species in the park. Our study provides insight for the conservation of these regionally significant carnivore populations, and our approach is broadly applicable to the robust assessment of communities of rare and elusive species subject to environmental change.

Predicting Landscape-Genetic Consequences of Habitat Loss, Fragmentation and Mobility for Multiple Species of Woodland Birds

Inference concerning the impact of habitat fragmentation on dispersal and gene flow is a key theme in landscape genetics. Recently, the ability of established approaches to identify reliably the differential effects of landscape structure (e.g. land-cover composition, remnant vegetation configuration and extent) on the mobility of organisms has been questioned. More explicit methods of predicting and testing for such effects must move beyond post hoc explanations for single landscapes and species. Here, we document a process for making a priori predictions, using existing spatial and ecological data and expert opinion, of the effects of landscape structure on genetic structure of multiple species across replicated landscape blocks. We compare the results of two common methods for estimating the influence of landscape structure on effective distance: least-cost path analysis and isolation-by-resistance. We present a series of alternative models of genetic connectivity in the study area, represented by different landscape resistance surfaces for calculating effective distance, and identify appropriate null models. The process is applied to ten species of sympatric woodland-dependant birds. For each species, we rank a priori the expectation of fit of genetic response to the models according to the expected response of birds to loss of structural connectivity and landscape-scale tree-cover. These rankings (our hypotheses) are presented for testing with empirical genetic data in a subsequent contribution. We propose that this replicated landscape, multi-species approach offers a robust method for identifying the likely effects of landscape fragmentation on dispersal.

Binding Affinity Prediction for Ligands and Receptors Forming Tautomers and Ionization Species: Inhibition of Mitogen-Activated Protein Kinase-Activated Protein Kinase 2 (MK2)

Treatment of ionization and tautomerism of ligands and receptors is one of the unresolved issues in structure-based prediction of binding affinities. Our solution utilizes the thermodynamic master equation, expressing the experimentally observed association constant as the sum of products, each valid for a specific ligand–receptor species pair, consisting of the association microconstant and the fractions of the involved ligand and receptor species. The microconstants are characterized by structure-based simulations, which are run for individual species pairs. Here we incorporated the multispecies approach into the QM/MM linear response method and used it for structural correlation of published inhibition data on mitogen-activated protein kinase (MAPK)-activated protein kinase (MK2) by 66 benzothiophene and pyrrolopyridine analogues, forming up to five tautomers and seven ionization species under experimental conditions. Extensive cross-validation showed that the resulting models were stable and predictive. Inclusion of all tautomers and ionization ligand species was essential: the explained variance increased to 90% from 66% for the single-species model.

Climate/Growth Correlations of tree Species in the Indus Basin of the Karakorum Range, North Pakistan

The climate/growth relationships of four gymnosperm tree species growing in seven catchments in the Indus Basin of the Karakorum range, North Pakistan, were evaluated for using two versions of tree-ring chronologies: “standard” and “residual” chronology. The growth of the trees was compared to instrumental climate records registered in Gilgit and to a climate data set of a 0.5° latitude-longitude grid. The effect of the previous year’s tree-ring widths on growth resulted in a higher correlation in the case of “standard” chronologies. A consistently significant response to climate was observed for all species at all sites. Such results highlight the potential for a multi-species approach for climate reconstructions. Of all the four species assessed, the strongest climate signal was seen in Pinus gerardiana. Winter and spring precipitation showed a pronounced positive correlation with tree growth while an inverse response to spring temperature was seen. Of the two climate parameters (temperature and precipitation) the strongest response was seen to rainfall. The gridded and the instrumental climatic data produced similar correlation patterns but the highest values were obtained with the “local” Gilgit data although some tree-ring sites are about 90 km apart from this meteorological station. Overall, the results demonstrate a high potential of the trees of the study region for reconstructing of past climate and past river flow.

α- and β-diversity in moth communities in salt marshes is driven by grazing management

This study evaluates the effects of long-term sheep grazing in salt marshes on the diversity of moths and derives conclusive management suggestions for the conservation of invertebrate diversity in salt marshes. Study sites were located on the Hamburger Hallig, on the Western coast of Schleswig–Holstein, Germany. Between 2006 and 2009, salt marshes that have been under four levels of livestock density (0, 1–2 sheep/ha, 3–4 sheep/ha, 10 sheep/ha) for over 20years were sampled using light traps and photoeclectors. Plant and moth species richness were highest under low stocking densities, moth species richness, however, showed no difference between low stocking densities and abandonment. Species richness of moths was only weakly correlated with vegetation parameters (species richness, vegetation height, cover and litter). Using additive diversity partitioning we show that no single grazing treatment harbored all recorded moth species and that grazing increases habitat heterogeneity within each treatment. Additionally, we show that moths react more sensitively to grazing than plants, and that therefore assessments of plant species richness in salt marshes do not allow conclusions on invertebrate diversity. For the evaluation of salt-marsh diversity, a multi-species approach should be favored combining plant and invertebrate assessments. A mosaic of abandoned sites and sites with low and intermediate stocking densities would benefit moth diversity in salt-marsh conservation.

Comparison of field- and GIS-based assessments of barriers to Atlantic salmon migration: a case study in the Nore Catchment, Republic of Ireland

In Ireland, the Water Framework Directive (WFD) Freshwater Morphology Programme of Measures and Standards (POMS) identified barriers to fish migration as one of the principal issues placing channels ‘at risk’ in terms of failing to achieve hydromorphology status. To quantify the degree of risk posed, and to develop methods to appraise and quantify risk associated with barriers, the POMS undertook a pilot study on the River Nore catchment. This provided an opportunity to compare the outcomes of an intensive field-based qualitative assessment of barriers to fish migration with a rules-based appraisal of risk, based on layers of geo-referenced data, in a Geographical Information System (GIS) analysis. The underlying aim of this risk-based assessment was the restoration of the fisheries resource, in the context of WFD, grounded on knowledge-based assessment. The comparison focused on the Atlantic salmon (Salmo salar L.). A rapid-assessment field survey compiled a geo-referenced inventory of 508 structures (497 artificial and 11 natural) and classified each with regard to presumed risk of preventing the upstream migration of adult Atlantic salmon. This inventory was then subjected to a rigorous GIS-based analysis, using field-generated datasets on Atlantic salmon ecology in the Nore catchment. The rules-based analysis provided a very substantial re-classification of artificial barriers with a major reduction in the numbers classified as impassable or high-risk. It confirmed that no ‘high risk’ barriers to adult salmon occurred on the R. Nore main stem but identified clusters of high risk barriers in the Dinin subcatchment and a series of moderate risk obstructions in the King’s River system. The GIS-based approach enabled an examination of the costs and benefits of stepwise removal of barriers, in terms of additional wetted habitat and salmon spawning area made accessible upstream of each barrier. A multi-species approach was then explored, examining the risk to upstream passage for eel (Anguilla Anguilla L.), sea lamprey (Petromyzon marinus L.) and Twaite shad (Alosa fallax Lacépede). Substantial clustering of sea lamprey spawning effort was reported downstream of the lowermost weirs on the R. Nore. A combination of barriers identified from a salmon perspective and via the multi-species approach provided a listing of priority barriers for attention. The strategy of step-wise removal or modification of artificial barriers in an upstream direction would provide optimal conservation value for the relevant species. The study identified the primacy of the field survey in geo-referencing site locations. However, it also identified the shortcomings of the qualitative, ‘expert-judgement’ approach to risk category allocation of the barriers and, hence, the need for more rigorous criteria in implementing a field-based rapid assessment.

A heat wave and dispersal cause dominance shift and decrease biomass in experimental metacommunities

In experimental metacommunities with marine benthic microalgae, we tested whether heat stress changes effects of connectivity and habitat heterogeneity on metacommunity structure and functioning, by manipulating a simulated heat wave, dispersal frequency and a light intensity gradient. We found that all measures of mean local and regional diversity and community biomass significantly declined after the heat wave and showed no sign of recovery. Additionally, dispersal decreased diversity and increased dominance in both the heat stressed and control communities. Together the heat wave and high dispersal frequency induced a dominance shift by spreading a temperature tolerant but low yielding species from its source patches with low light intensity across the metacommunity, an effect that increased with time. Although different species became dominant at high dispersal frequency with and without the heat wave, the shift towards a temperature tolerant species was not sufficient to maintain total community biomass. Thus, short‐term disturbance may cause longer‐term loss of ecosystem function due to dominance shifts in the composition of communities. This study illustrates the importance of employing multispecies approaches when attempting to predict responses of communities to environmental changes.

Aqueous suspension methods of carbon‐based nanomaterials and biological effects on model aquatic organisms

The preparation of aqueous suspensions of carbon-based nanomaterials (NMs) requires the use of dispersing agents to overcome their hydrophobic character. Although studies on the toxicity of NMs have focused primarily on linking the characteristics of particles to biological responses, the role of dispersing agents has been overlooked. This study assessed the biological effects of a number of commonly used dispersing agents on Pseudokirchneriella subcapitata and Ceriodaphnia dubia as model test organisms. The results show that for a given organism, NM toxicity can be mitigated by use of nontoxic surfactants, and that a multispecies approach is necessary to account for the sensitivity of different organisms. In addition to the intrinsic physicochemical properties of NMs, exposure studies should take into account the effects of used dispersing fluids.

Lower trophic levels and detrital biomass control the Bay of Biscay continental shelf food web: Implications for ecosystem management

The Bay of Biscay (North-East Atlantic) has long been subjected to intense direct and indirect human activities that lead to the excessive degradation and sometimes overexploitation of natural resources. Fisheries management is gradually moving away from single-species assessments to more holistic, multi-species approaches that better respond to the reality of ecosystem processes. Quantitative modelling methods such as Ecopath with Ecosim can be useful tools for planning, implementing and evaluating ecosystem-based fisheries management strategies. The aim of this study was therefore to model the energy fluxes within the food web of this highly pressured ecosystem and to extract practical information required in the diagnosis of ecosystem state/health. A well-described model comprising 30 living and two non-living compartments was successfully constructed with data of local origin, for the Bay of Biscay continental shelf. The same level of aggregation was applied to primary producers, mid-trophic-levels and top-predators boxes. The model was even more general as it encompassed the entire continuum of marine habitats, from benthic to pelagic domains. Output values for most ecosystem attributes indicated a relatively mature and stable ecosystem, with a large proportion of its energy flow originating from detritus. Ecological network analysis also provided evidence that bottom-up processes play a significant role in the population dynamics of upper-trophic-levels and in the global structuring of this marine ecosystem. Finally, a novel metric based on ecosystem production depicted an ecosystem not far from being overexploited. This finding being not entirely consistent over indicators, further analyses based on dynamic simulations are required.