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Benthic-pelagic coupling is manifested as the exchange of energy, mass, or nutrients between benthic and pelagic habitats. It plays a prominent role in aquatic ecosystems, and it is crucial to functions from nutrient cycling to energy transfer in food webs. Coastal and estuarine ecosystem structure and function are strongly affected by anthropogenic pressures; however, there are large gaps in our understanding of the responses of inorganic nutrient and organic matter fluxes between benthic habitats and the water column. We illustrate the varied nature of physical and biological benthic-pelagic coupling processes and their potential sensitivity to three anthropogenic pressures - climate change, nutrient loading, and fishing - using the Baltic Sea as a case study and summarize current knowledge on the exchange of inorganic nutrients and organic material between habitats. Traditionally measured benthic-pelagic coupling processes (e.g., nutrient exchange and sedimentation of organic material) are to some extent quantifiable, but the magnitude and variability of biological processes are rarely assessed, preventing quantitative comparisons. Changing oxygen conditions will continue to have widespread effects on the processes that govern inorganic and organic matter exchange among habitats while climate change and nutrient load reductions may have large effects on organic matter sedimentation. Many biological processes (predation, bioturbation) are expected to be sensitive to anthropogenic drivers, but the outcomes for ecosystem function are largely unknown. We emphasize how improved empirical and experimental understanding of benthic-pelagic coupling processes and their variability are necessary to inform models that can quantify the feedbacks among processes and ecosystem responses to a changing world.

Source at https://doi.org/10.1002/ecs2.1753 . Trophic transfer and retention of dietary compounds are vital for somatic development, reproduction, and survival of aquatic consumers. In this field study, stable carbon and nitrogen isotopes, and fatty acids (FA) contents in invertebrates and fishes of pre-alpine Lake Lunz, Austria, were used to (1) identify the resource use and trophic level of Arctic charr (Salvelinus alpinus), pike (Esox lucius), perch (Perca fluviatilis), brown trout (Salmo trutta), roach (Rutilus rutilus), and minnow (Phoxinus phoxinus) and (2) examine how polyunsaturated fatty acids (PUFA; i.e., omega-3 and -6 PUFA) are related to total lipid status, littoral–pelagic reliance, and trophic position. Stable isotope data suggest that pike, perch, and minnow derived most of their energy from littoral resources, but minnows differed from pike and perch in their trophic position and PUFA composition. The co-occurrence of cyprinids, percids, and pike segregated these fishes into more lipid-rich (roach, minnow) and lipid-poor (pike, percids) species. Although the relatively lipid-poor pike and percids occupied a higher trophic position than cyprinids, there was a concurrent, total lipid-dependent decline in omega-3 and -6 PUFA in these predatory fishes. Results of this lake food-web study demonstrated that total lipids in fish community, littoral–pelagic reliance, and trophic position explained omega-3 and -6 PUFA in dorsal muscle tissues. Omega-3 and -6 PUFA in these fishes decreased with increasing trophic position, demonstrating that these essential FAs did not biomagnify with increasing trophic level. Finally, this lake food-web study provides evidence of fish community-level relationship between total lipid status and PUFA or stable isotope ratios, whereas the strength of such relationships was less strong at the species level.

The biological carbon pump (BCP) is a complex suite of processes responsible for transporting organic matter produced in the surface ocean to depth. As such, it is an important mechanism in controlling the sequestration of atmospheric carbon dioxide (CO2) and its storage on time scales of decades to centuries. This receives special attention in light of the rising anthropogenic CO2 emissions, which are unprecedented in the recent geological history of this planet. Despite its importance, we are still lacking a mechanistic understanding of the processes controlling the efficiency of the BCP. Over the past decade, the focus has increasingly shifted towards illuminating the effect of differences in ecosystem structure on organic matter export. This doctoral dissertation thus aimed and succeeded to reveal patterns in the relation between food-web structure changes and the efficiency of the BCP and circumstantiated recent concepts in this field of research. Furthermore, this work exemplifies that the methodological approach of utilizing in situ mesocosms can make a significant contribution to BCP research, for it allows answering questions that conventional methods have not been able to address. Die biologische Kohlenstoffpumpe (BKP) ist ein komplexes Zusammenspiel aus Prozessen, welche in ihrer Gesamtheit für den Transport von organischer Materie aus dem Oberflächenozean in die Tiefe verantwortlich ist. Als solches spielt sie gleichzeitig eine wichtige Rolle in der Sequestrierung von atmosphärischem Kohlenstoffdioxid (CO2) und seiner Speicherung in der Tiefe über Zeiträume von Jahrzehnten bis Jahrtausenden. Dies hat besondere Bewandtnis im Anbetracht der steigenden anthropogenen CO2 Emissionen, welche beispiellos sind in der jüngsten geologischen Geschichte dieses Planeten. Trotz ihrer zweifelslosen Bedeutung sind wir noch immer in Ermangelung eines mechanistischen Verständnisses der Prozesse, welche die Effizienz der BKP kontrollieren. Im Laufe der letzten zehn Jahre hat sich der Fokus zunehmend auf das Verständnis des Zusammenhangs zwischen Ökosystem-Strukturen und Export von organischer Materie verlagert. Zusammenfassend hat die vorliegende Doktorarbeit Muster in dem Verhältnis zwischen Nahrungsnetz-Struktur und der Effizienz der BKP aufgezeigt, jüngste Konzepte bestätigt und erweitert. Außerdem verdeutlicht diese Arbeit, dass der methodische Ansatz von in situ Mesokosmenexperimenten einen wichtigen Beitrag in der Erforschung der BKP leisten kann und die Beantwortung von Fragen ermöglicht, welche mit herkömmlichen Methoden bisher nicht ohne weitere Annahmen möglich war.

Besides microbes a wide variety of cave animals inhabit various caves of Malaysia, ranging from tiny invertebrates through to small mammals, reptiles, amphibians and bats. Evidence even supports the visitation of elephants to some caves. In the present report the food web complexity and the species diversity that exist in Malaysian caves is described on the basis of direct sightings. Furthermore, the major threats to the present status of such caves are also discussed.

1.There has been an intense focus on the response of species to environmental changes and more recently the interactions of species have been examined in a similar way in order to understand the stability of entire communities and networks of interacting species. As a consequence, ecological networks have been placed in spatial and temporal contexts in order to reveal what may drive network variability. Understanding the spatial and temporal variability of ecological networks, and in particular the underlying forces facilitating changes, seems pertinent in our attempts to understand and anticipate how ecological networks may vary and respond to future environmental scenarios. 2.Network variability has been studied at widely differing temporal and spatial scales. For example, studies exploring temporal variability ranges from within-season comparisons to comparisons over vast geological timespans, and the spatial extent ranges from the scale of a single pond to global analyses. Here we highlight the outcomes from such studies and emphasize the identified mechanisms driving spatio-temporal variability in ecological networks. Specifically, we describe how ecological networks vary over different temporal (years, centuries and millennia) and spatial (local, regional and global) scales, discuss how this variability is monitored, and identify potential future directions. 3.Present knowledge allows some tentative generalizations. First, ecological networks tend to exhibit considerable spatial and temporal stability in several macroscopic features (e.g. connectance, nestedness), but studies also show that macroscopic features may changes e.g. in relation to mass extinction or steep environmental gradients. Second, microscopic features (e.g. individual specialization levels, species roles, and partner affiliations), albeit less studied, seem to show strong variability, and in several cases microscopic instability co-occur with macroscopic stability. We therefore recommend a stronger focus on this macro-micro interplay, and list ideas (e.g. temporal species centrality measures, and interaction phenologies), towards expanding the microscopic toolbox of network ecologists. This article is protected by copyright. All rights reserved.

Long-term declines in abundance of wild Atlantic salmon Salmo salar, L. have been linked to reductions in marine survivorship, and recent reductions in growth condition (a measure of fish quality) have been correlated to increased mid-winter sea-surface temperature anomalies in the eastern North Atlantic. Establishing a causal link between marine climate and salmon somatic condition is difficult without at-sea measurements of environmental and biological parameters, but electronically tagging these animals to obtain this information is also difficult and costly. The stable isotope composition of oxygen and carbon in the sequential layers of salmon otoliths can provide a basis for retrospective studies of the thermal, metabolic and dietary histories of individual fish. We used high resolution delta O-18 and delta C-13 profiles obtained using secondary ion mass spectrometry to compare the marine thermal and metabolic behaviour of 1 sea-winter return-migrant adult salmon. Seasonal and ontogenetic patterns in delta O-18 and delta C-13 values dominated isotope variation, although there were marked differences between individual profiles, indicating the potential for large differences in individual migration routes. There was no significant relationship between isotope variation and adult condition. Constructed thermal profiles provided plausible data, but the present uncertainty in otolith thermometry parameters for an open-ocean fish such as Atlantic salmon preclude firm conclusions based on these estimates. Marine life-history variation in otolith delta C-13 is likely driven by ontogenetic changes, both in diet and metabolism with size. A marked and rapid decrease in the delta C-13 values of some fish in the last month(s) of the marine migration could be an indicator of physiological changes occurring during the homing migration.

Environmental authorities require the protection of biodiversity and other ecosystem properties such as biomass production. However, the endpoints listed in available ecotoxicological datasets generally do not contain these two ecosystem descriptors. Inferring the effects of chemicals on such descriptors from micro- or mesocosm experiments is often hampered by inherent differences in the initial biodiversity levels between experimental units or by delayed community responses. Here we introduce additive modelling to establish the effects of a chronic application of the herbicide linuron on 10 biodiversity indices and phytoplankton biomass in microcosms. We found that communities with a low (high) initial biodiversity subsequently became more (less) diverse, indicating an equilibrium biodiversity status in the communities considered here. Linuron adversely affected richness and evenness while dominance increased but no biodiversity indices were different from the control treatment at linuron concentrations below 2.4 μg/L. Richness-related indices changed at lower linuron concentrations (effects noticeable from 2.4 μg/L) than other biodiversity indices (effects noticeable from 14.4 μg/L) and, in contrast to the other indices, showed no signs of recovery following chronic exposure. Phytoplankton biomass was unaffected by linuron due to functional redundancy within the phytoplankton community. Comparing thresholds for biodiversity with conventional toxicity test results showed that standard ecological risk assessments also protect biodiversity in the case of linuron.

The question whether animal populations are top-down and/or bottom-up controlled has motivated a thriving body of research over the past five decades. In this review I address two questions: 1) how do top-down and bottom-up controls influence large herbivore populations? 2) How do human activities and control systems influence the top-down and bottom-up processes that affect large herbivore population dynamics? Previous studies suggest that the relative influence of top-down vs. bottom-up control varies among ecosystems at the global level, with abrupt shifts in control possible in arid and semi-arid regions during years with large differences in rainfall. Humans as super-predators exert top-down control on large wild herbivore abundances through hunting. However, through fires and livestock grazing, humans also exert bottom-up controls on large wild herbivore abundances through altering resource availability, which influences secondary productivity. This review suggests a need for further research, especially on the human-induced top-down and bottom-up control of animal populations in different terrestrial ecosystems.

Indexación: Web of Science; Scopus. In high altitude environments, extreme levels of solar radiation and important differences of ionic concentrations over narrow spatial scales may modulate microbial activity. In Salar de Huasco, a high-altitude wetland in the Andean mountains, the high diversity of microbial communities has been characterized and associated with strong environmental variability. Communities that differed in light history and environmental conditions, such as nutrient concentrations and salinity from different spatial locations, were assessed for bacterial secondary production (BSP, H-3-leucine incorporation) response from short-term exposures to solar radiation. We sampled during austral spring seven stations categorized as: (a) source stations, with recently emerged groundwater (no-previous solar exposure); (b) stream running water stations; (c) stations connected to source waters but far downstream from source points; and (d) isolated ponds disconnected from ground sources or streams with a longer isolation and solar exposure history. Very high values of 0.25 mu E m(-2) s(-1), 72 W m(-2) and 12 W m(-2) were measured for PAR, UVA, and UVB incident solar radiation, respectively. The environmental factors measured formed two groups of stations reflected by principal component analyses (near to groundwater sources and isolated systems) where isolated ponds had the highest BSP and microbial abundance (35 microalgae taxa, picoeukaryotes, nanoflagellates, and bacteria) plus higher salinities and PO43- concentrations. BSP short-term response (4 h) to solar radiation was measured by H-3-leucine incorporation under four different solar conditions: full sun, no UVB, PAR, and dark. Microbial communities established in waters with the longest surface exposure (e.g., isolated ponds) had the lowest BSP response to solar radiation treatments, and thus were likely best adapted to solar radiation exposure contrary to ground source waters. These results support our light history (solar exposure) hypothesis where the more isolated the community is from ground water sources, the better adapted it is to solar radiation. We suggest that factors other than solar radiation (e.g., salinity, PO43-, NO3-) are also important in determining microbial productivity in heterogeneous environments such as the Salar de Huasco. http://journal.frontiersin.org/article/10.3389/fmicb.2016.01857/full

In this study, we measured depth-dependent benthic microalgal primary production in a Bothnian Bay estuary to estimate the benthic contribution to total primary production. In addition, we compiled data on benthic microalgal primary production in the entire Baltic Sea. In the estuary, the benthic habitat contributed 17 % to the total annual primary production, and when upscaling our data to the entire Bothnian Bay, the corresponding value was 31 %. This estimated benthic share (31 %) is three times higher compared to past estimates of 10 %. The main reason for this discrepancy is the lack of data regarding benthic primary production in the northern Baltic Sea, but also that past studies overestimated the importance of pelagic primary production by not correcting for system-specific bathymetric variation. Our study thus highlights the importance of benthic communities for the northern Baltic Sea ecosystem in general and for future management strategies and ecosystem studies in particular.

We foresee a new global-scale, ecological approach to biomonitoring emerging within the next decade that can detect ecosystem change accurately, cheaply, and generically. Next-generation sequencing of DNA sampled from the Earth's environments would provide data for the relative abundance of operational taxonomic units or ecological functions. Machine-learning methods would then be used to reconstruct the ecological networks of interactions implicit in the raw NGS data. Ultimately, we envision the development of autonomous samplers that would sample nucleic acids and upload NGS sequence data to the cloud for network reconstruction. Large numbers of these samplers, in a global array, would allow sensitive automated biomonitoring of the Earth's major ecosystems at high spatial and temporal resolution, revolutionising our understanding of ecosystem change.

Deep living for centuries We tend to think of vertebrates as living about as long as we do, give or take 50 to 100 years. Marine species are likely to be very long-lived, but determining their age is particularly difficult. Nielsen et al. used the pulse of carbon-14 produced by nuclear tests in the 1950s—specifically, its incorporation into the eye during development—to determine the age of Greenland sharks. This species is large yet slow-growing. The oldest of the animals that they sampled had lived for nearly 400 years, and they conclude that the species reaches maturity at about 150 years of age. Science , this issue p. 702

International audience; This study examined the trophic ecology of three sympatric tropical tuna species (bigeye BET, skipjack SKJ, and yellowfin YFT) sampled in the Western Indian Ocean throughout 2013. Specifically we explored inter-specific resource partitioning and ontogenetic variability using neutral fatty acids and stable isotope analysis of liver and muscle from small (100 cm FL) tuna collected in mixed schools at the surface by purse-seine. Both biochemical tracers were used to calculate trophic niche indices that collectively revealed high potential for resource overlap, especially among small tuna. Resource overlap appeared strongest between BET and YFT, with SKJ tissues having high carbon isotope (delta C-13) values (-17 +/- 0.3 parts per thousand), lower nitrogen isotope (delta N-15) values (11.4 +/- 0.6 parts per thousand), and higher relative proportion of poly-unsaturated fatty acids (PUFA) than the two other species, indicating a different diet. Size was found to be a strong predictor for most biochemical tracers in the three species with delta C-13, delta N-15 and total lipid content in the liver. In the larger species (YFT and BET), proportions of mono-unsaturated fatty acids typically increased with size, while quantities of PUFA decreased. In addition to ontogenetic variability, trophic markers were shown to vary between sampling area and season: higher lipid reserves and delta N-15 values, and lower delta C-13 values occurred during monsoon periods around Seychelles than in the Mozambique Channel (parted from about 1500 km). Our multi-tracer approach reveals the magnitude of potential competitive interactions in mixed tropical tuna schools at both small and large sizes and demonstrates that ontogenetic niche differentiation acts as a major factor of coexistence in tropical tuna

WOS:000372014200055; International audience; Mixotrophic plankton, which combine the uptake of inorganic resources and the ingestion of living prey, are ubiquitous in marine ecosystems, but their integrated biogeochemical impacts remain unclear. We address this issue by removing the strict distinction between phytoplankton and zooplankton from a global model of the marine plankton food web. This simplification allows the emergence of a realistic trophic network with increased fidelity to empirical estimates of plankton community structure and elemental stoichiometry, relative to a system in which autotrophy and heterotrophy are mutually exclusive. Mixotrophy enhances the transfer of bio-mass to larger sizes classes further up the food chain, leading to an approximately threefold increase in global mean organism size and an similar to 35% increase in sinking carbon flux.

The overexploitation of high trophic level predators (HTLP) may trigger trophic cascades, often leading to a simplification of marine food-webs and reducing their resilience to human impacts. Marine protected areas (MPAs) can foster increases of HTLP abundance and biomass, but long time frames are needed to observe a recovery, when possible, of lost trophic interactions. This PhD aimed to propose integrated management-tools to monitor HTLP recovery and the restoration of trophic interactions in Mediterranean MPAs, and to evaluate the effectiveness of these tools at assessing fishing impacts upon HTLP and the associated food-web. Two often distant approaches were combined: field monitoring and food-web modelling. First, to survey the fish assemblage, we proposed to improve the traditional underwater visual census technique of one size-transects with variable size transects adapted to fish mobility. This improvement increased the accuracy of density and biomass estimates of HTLP at three Mediterranean MPAs. We then evaluated the potential of food-web modelling with the Ecopath with Ecosim and Ecotroph approach as a tool to inform ecosystem-based management in Mediterranean MPAs. We proposed a standard model structure as the best compromise between model complexity, feasibility of model construction in terms of data collection, and reliability of model outputs. Key functional groups for which local accurate biomass data should be collected in priority in order to get reliable model outputs were identified.; La surexploitation des prédateurs de haut niveau trophique (HTLP) peut déclencher des cascades trophiques qui souvent conduisent à une simplification des réseaux trophiques marins en réduisant leur résistance aux impacts humains. Les aires marines protégées (AMP) peuvent favoriser des augmentations d’abondance et biomasse des HTLP, mais la complète restauration des interactions trophiques, lorsque cela est possible, nécessite des délais importants. Cette thèse vise à proposer des outils intégrés de gestion pour évaluer le retour des HTLP et la restauration des interactions trophiques dans les AMP méditerranéennes, et à évaluer l’efficacité de ces outils pour estimer les impacts de la pêche sur les HTLP et le réseau trophique associé. Deux approches souvent éloignées ont été combinées : les suivis de terrain et la modélisation des réseaux trophiques. Pour échantillonner la communauté de poissons, nous avons proposé d'améliorer la technique traditionnelle de recensement visuel sous-marin en recourant à des transects de taille variable, adaptée à la mobilité des poissons. Cette méthode a alors permis d'augmenter la précision des estimations de densité et de biomasse des HTLP dans les trois AMP méditerranéennes suivies. Ensuite, nous avons évalué l'apport de la modélisation trophique avec les approches EwE et EcoTroph comme outil de gestion écosystémique pour les AMP méditerranéennes. Une structure standard de modèle a été proposée comme étant le meilleur compromis entre la complexité du modèle, la faisabilité de sa construction et la fiabilité de ses sorties.

Little is known about the levels of organochlorines (OCs) in predatory bird species from Asia or the factors governing their concentrations. This study is the first report on concentrations of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in predatory birds of Pakistan. The concentrations of PCBs and OCPs were investigated using tail feathers of ten different species of predatory birds. In addition, concentration differences among body, tail, primary and secondary feathers were investigated for six individuals of black kite (Milvus migrans). Ranges of concentrations were highest for dichlorodiphenyldichloroethylene (p,p'-DDE: 0.11-2163 ng g(-1) dry wt,) followed by dichlorodiphenyltrichloroethane (p,p'-DDT: 0.36-345 ng g(-1) dry wt.), hexachlorobenzene (HCB: 0.02-34 ng g(-1) dry wt.), Sigma PCBs (0.03-16 ng g(-1) dry wt.) and trans-nonachlor (TN; 0.01-0.13 ng g(-1) dry wt.). CB 118, 153,138, and 180 along with p,p'-DDE were found as the most prevalent compounds. Sigma PCBs and Sigma DDTs were significantly different among species (both p < 0.01) and omnivorous, scavengers, carnivorous and piscivorous trophic guilds (all p < 0.03). Only Sigma PCBs were significantly clifferentamong different families of birds (p

PhD (Zoology), North-West University, Potchefstroom Campus, 2016 The primary aim of practising conservation agriculture (CA) is to optimise crop production. This is done by using practices and principles that promote soil quality by increasing population levels and/or diversity of beneficial soil organisms, including non-parasitic nematodes. Conservation agriculture is also considered as an alternative means to control plant-parasitic nematode population levels. The main aim of this study was to determine the effect of CA compared to conventional agriculture (CTA) on plant- and non-parasitic nematode communities under maize-based cropping systems in South Africa. Furthermore, the identity of two types of eggs („large‟ and „small‟), present in 50-g root samples of maize (survey study) and maize and other crops (CA study), were clarified and the genera representing them determined. Associations between plant- parasitic nematodes and maize yield were also determined. Additionally, correlations between the different soil chemical parameters and soil nematode assemblages (plant- and non-parasitic nematodes) were investigated. For determining the effect(s) of CA vs. CTA on nematodes, a survey was conducted in the two the main maize-producing areas of South Africa (Free State and North-West provinces). Furthermore, nematode samples (root and soil) from two CA-trials were also obtained. For the survey, root and rhizosphere soil samples (including maize fields under CA and CTA as well as natural veld (NV)) were obtained from 24 ecosystems during the 2012/2013 growing season. For determining the effects of CA vs. CTA on soil nematode population assemblages over a four-year period, two rain-fed field trial sites, were monitored under different maize-based cropping sequences (CRS). These sites were Buffelsvallei (sandy loam soil) and Erfdeel (sandy soil), which is part of a CA programme of the Agricultural Research Council‟s Grain Crops Institute. At these sites, CA and CTA maize monoculture were practised, while maize was also rotated with cowpea, pearl millet and sunflower in different crop-sequence combinations. Rhizosphere soil samples for nematode analyses were obtained before/during planting during each growing season from all plots as well as 60 and 100 days after planting. Additional soil samples were also obtained for soil chemical and physical analyses. Root samples were obtained during the 60- and 100-day sampling intervals. Standard techniques were used to extract nematodes from root and soil samples. Morphological and molecular (only for Meloidogyne spp.) techniques were used to identify nematodes to genus/species (plant-parasitic nematodes) and/or genus/family (non-parasitic nematodes) levels. During both the survey and CA study, 50-g root samples contained two different types of eggs („large‟ and „small‟) when using the NaOCl method. The two egg types were measured (length and width) and were subjected to deoxyribonucleic (DNA) sequencing to identify the nematode genera these two types of eggs belonged to. This activity was conducted first and formed the basis of this study. The two types of eggs were successfully identified with the „large‟ eggs belonging to the genus Meloidogyne and the „small‟ eggs to Rotylenchulus. The measurements furthermore showed that the Meloidogyne eggs were significantly longer than the Rotylenchulus eggs. The same applied for the width of the eggs, with those belonging to Meloidogyne being wider than those of Rotylenchulus. This research is a novel and significant contribution to the Nematology discipline since it will assist in more accurate research related to the presence and effects of Meloidogyne and Rotylenchulus on maize and other food crops. During the survey a total of 13 plant-parasitic genera, 21 species and one subspecies were identified. Of these, 10 genera and 11 species as well as one subspecies were associated with CA maize. Data showed that fields under CA had higher prominence values (PV) for most of the plant-parasitic nematode general/species identified compared to those present in CTA maize as well as NV. This was evident for Rotylenchulus parvus and Pratylenchus spp. populations. However, maize under CTA had higher PV values for Meloidogyne spp. The opposite scenario was observed for non-parasitic nematodes that were present in soil samples. The NV in general had higher PV values and diversity of non-parasitic nematodes, followed by the CA maize for most of the non-parasitic nematode genera/families. Nematode-food web structures showed that most of the soils (including those from NV) sampled represented resource-depleted nematode communities. The non-parasitic nematode genera, Acrobeles and Acrobeloides was the predominant bacterivores present within the soils collected from maize (both CA and CTA) as well as NV. The predominant fungivores present were Aphelenchus and Aphelenchoides while the family Discolaimidae and genera Discolaimoides were identified as the dominant predators. For the CA study, nine plant-parasitic nematode genera and 11 species were identified at Buffelsvallei while at Erfdeel a total of six genera and nine species were observed. Rotylenchulus parvus was the predominant nematode pest present in the 50-g root samples at Buffelsvallei, while Meloidogyne incognita was dominant at Erfdeel. Results also showed that when either cowpea or sunflower were included in the CA cropping sequences (CRSs) a significant decline in R. parvus population densities occurred over the four-year duration of the study. Pratylenchus spp. was the dominant plant-parasitic nematode genus present in the 5-g root samples at both localities. As for R. parvus (50 g roots) when either cowpea or sunflower was included, a decline in the population density of this nematode species was observed. This study ultimately showed that the CA CRSs, in general, had lower plant-parasitic nematode densities than the monoculture CTA. However, both Scutellonema brachyurus (Buffelsvallei) and Tylenchorhynchus goffarti (Erfdeel) had higher population densities in soils under CA than CTA. With regard to non-parasitic nematodes present in soils from the CA study, 31 nematode genera and two families were identified at Buffelsvallei. For Erfdeel a total of 21 non-parasitic nematode genera and four families were observed. Related to the CRSs under CA, higher nematode densities and diversity of non-parasitic nematodes were recorded than from those in CTA maize. This was also demonstrated by the nematode food-web analyses. Bacterivores dominated in soils from both CTA and CA cropping sequences followed by the fungivores. This scenario was evident at both localities. Food-web structures showed that non-parasitic nematode diversity was higher when either cowpea or sunflower was included in the CRSs under CA. However, the majority of the CRSs (both CA and CTA) had soil qualities characterised as stressed and depleted in terms of their inhabiting non-parasitic nematode communities. Identification of non-parasitic nematodes to genera/family level seemed to provide a more accurate reflection of the community structure than when using trophic levels alone. This was further substantiated by the noticeable differences observed between the nematode assemblages and the different CRSs used. Negative correlations existed between maize yield and R. parvus at Erfdeel but not at Buffelsvallei. Correlations between nematodes and soil chemical parameters showed that organic matter (%C) in general had positive, but weak associations with most of the plant- and non-parasitic nematodes. However, %C did had strong, positive correlations with Nanidorus minor and Scutellonema brachyurus at Buffelsvallei. Also, strong, positive correlations between %C and non-parasitic nematode families Panagrolaimidae, Cephalobidae, Dorylaimidae and Tylenchidae existed. Furthermore, at Buffelsvallei sodium (Na) had a positive, strong association with the non-parasitic nematode family Rhabditidae. For this latter locality, phosphate (P) also had strong, positive associations with Cephalobidae and Aphelenchidae (both non-parasitic). Ultimately, results of this study demonstrated that differences in plant- and non-parasitic assemblages existed between maize fields under CA and CTA. Further investigation is, however, needed with regard to nematodes vs. crop yields and soil chemical and physical parameters under local maize-based cropping systems. This study also warrants further investigation with regard to R. parvus and its potential as a pathogenic plant-parasitic nematode in the local maize industry. No information on its reproductive potential and pathogenicity on maize are available worldwide. Further research should also focus on longer term studies related to nematode-CA investigations to obtain an extensive body of information. This will also result in the generation of data on associations between nematode pests and crop yields, as well as chemical soil parameters which are limited and fragmented at present Doctoral

Harbour porpoises are the most common small cetaceans in the North Sea and Dutch coastal waters. To study their trophic level and feeding location, stable carbon and nitrogen isotope ratios (d 13 C and d 15 N) were analysed in muscle and bone samples collected from 157 porpoises stranded along the Dutch coast (2006! 2008). In addition, samples from 30 prey species were analysed. Prey samples showed high d 15 N values in species of higher trophic level. In addition, geographic differences in isotopic composition were found, with higher d 15 N and d 13 C values in prey from more southern, coastal and estuarine areas. Based on muscle d 15 N values, we found neonatal enrichment and that larger porpoises, in particular males, seem to feed on lower trophic level species, compared to smaller individuals. Also bone d 15 N values show that larger animals had fed on lower trophic levels in distant times. Porpoises from the Eastern Scheldt reveal distinct d 13 C values in muscle, but not in bone. This shows that these animals had foraged in the Eastern Scheldt for a longer time period but were not born there. Seasonal variation in bone d 15 N and d 13 C values revealed two distinct groups of porpoises along the Dutch coast, a winter group (mainly males) that migrated from neighbouring regions and a Dutch subpopulation in summer. These results furthered our insight about shifts in trophic level and feeding location of harbour porpoises from the southern North Sea over time.

Plant-mediated effects of aboveground herbivory on the belowground ecosystem are well documented, but less attention has been paid to agro-ecosystems and in particular how crop cultivars with different traits (i.e. resistance to pests) shape such interactions. A fully factorial experiment was conducted using four rice cultivars with different insect-resistance, with and without the aboveground herbivore Nilaparvata lugens (brown planthopper), and to test two hypotheses (1) aboveground herbivory affects the soil microbial biomass and nematode community by altering plant performance and soil resource availability and (2) herbivory effects will depend on cultivar resistance traits. Our results suggested that cultivar resistance mediated both herbivory intensity and herbivore effects on plant performance. N. lugens decreased the availability of soil resources (soluble sugars, amino acids, organic acids, dissolved organic carbon and nitrogen), microbial biomass and percentages of bacterivores when feeding on a susceptible cultivar but increased them in a resistant cultivar. However, total nematode abundance and the percentage of plant-parasitic nematodes responded in the opposite way, increasing under a susceptible cultivar and decreasing under a resistant cultivar. The development of plant-parasites under resistant cultivars before aboveground herbivory might contribute to their resistance traits. Our findings provide evidence that N. lugens significantly reversed the pattern of soil resource availability, microbial biomass and nematode community structure (abundance and trophic composition) across cultivars with distinct resistance. In the presence of aboveground pests, the agronomic use of resistant rice cultivars could also control populations of plant-parasites and promote soil resource availability, further extended to higher trophic level of soil food web.

The ecological traits of piscivorous marine birds have been acknowledged to reflect ecosystem changes. We used the great cormorant as our indicator species in the Minho estuary (NW-Iberian Peninsula, Europe) to assess the temporal variation of their diet and the factors that could influence that variation. Pellets were collected in a night roost, located centrally in the estuary, during two consecutive wintering periods (2005–2006 and 2006–2007). The great cormorant population showed a high degree of feeding plasticity and most of the variation in cormorants' diet was attributed to river discharge fluctuations. Overall, during periods of increased river discharge, marine and marine opportunistic species disappeared from diet, whereas freshwater species increased. The cormorants in this study were using a roost in the middle of the estuary, so they were facing a changing food base over time, in accordance to variation in river discharges. The birds did not keep their diet constant but rather took what became locally available, notwithstanding their broad foraging range. Therefore, we suggest that great cormorants may be considered good samplers of local ichthyofauna and thus, temporal variation in the local prey can be followed by analyzing cormorants' diet.

In this study, the impact of species-specific spatial habitat use, diet preferences, and soil concentrations and properties on the accumulation of cadmium in small mammals was investigated. The results show that for the wood mouse (Apodemus sylvaticus), a mobile species with a large range in diet composition, accumulation of cadmium was not related to local soil concentrations or soil properties, but to diet preferences. For the common vole (Microtus arvalis), a nonmobile, specific feeding species, accumulation of cadmium was related to local soil concentrations or properties. For the bank vole (Myodes glareolus), a species with a smaller home range than the wood mouse but a broader diet spectrum than the common vole, both local soil properties and diet appeared to affect the cadmium accumulation in the kidneys. The results of this field study show that species-specific traits of small mammals are important determinants of accumulation of cadmium on a local scale. For site-specific assessment of risks of contaminants, such information is essential in order to understand exposure dynamics.

Abstract The use of organic soil amendments, such as green manures, animal manures, composts or slurries, certainly has many advantageous aspects for soil quality and is suggested as a promising tool for the management of plant-parasitic nematodes. However, during a recent literature survey we also found numerous studies reporting an increase of plant-parasitic nematodes after the use of organic amendments. Therefore, we critically re-evaluated the usefulness of organic amendments for nematode management and suggest possible mechanisms for a stimulation of plant-parasitic nematodes, as well as mechanisms that might be causing a reduction of plant-parasitic nematodes. In addition, we also elucidate a possible mechanism that might be responsible for the observed overall positive effects of organic amendments on crop yields. It is likely that a significant part of this is, inter alia, due to the proliferation of non-pathogenic, free-living nematodes and their overall positive effects on soil microbial populations, organic matter decomposition, nutrient availability, plant morphology and ecosystem stability.

International audience; The productivity and diversity of plant communities are affected by soil organisms such as arbuscular mycorrhizal fungi (AMF), root herbivores and decomposers. However, it is unknown how interactions between such functionally dissimilar soil organisms affect plant communities and whether the combined effects are additive or interactive. In a greenhouse experiment we investigated the individual and combined effects of AMF (five Glomus species), root herbivores (wireworms and nematodes) and decomposers (collembolans and enchytraeids) on the productivity and nutrient content of a model grassland plant community as well as on soil microbial biomass and community structure. The effects of the soil organisms on productivity (total plant biomass), total root biomass, grass and forb biomass, and nutrient uptake of the plant community were additive. AMF decreased, decomposers increased and root herbivores had no effect on productivity, but in combination the additive effects canceled each other out. AMF reduced total root biomass by 18%, but decomposers increased it by 25%, leading to no net effect on total root biomass in the combined treatments. Total shoot biomass was reduced by 14% by root herbivores and affected by an interaction between AMF and decomposers where decomposers had a positive impact on shoot growth only in presence of AMF. AMF increased the shoot biomass of forbs, but reduced the shoot biomass of grasses, while root herbivores only reduced the shoot biomass of grasses. Interactive effects of the soil organisms were detected on the shoot biomasses of Lotus corniculatus, Plantago lanceolata, and Agrostis capillaris. The C/N ratio of the plant community was affected by AMF. In soil, AMF promoted abundances of bacterial, actinomycete, saprophytic and AMF fatty acid markers. Decomposers alone decreased bacterial and actinomycete fatty acids abundances but when decomposers were interacting with herbivores those abundances were increased. Our results suggests that at higher resolutions, i.e. on the levels of individual plant species and the microbial community, interactive effects are common but do not affect the overall productivity and nutrient uptake of a grassland plant community, which is mainly affected by additive effects of functionally dissimilar soil organisms. (c) 2010 Elsevier Ltd. All rights reserved.

This study aimed at examining whether plant species of varying resource quality give rise to a fungal- or bacterial-based energy channel in the plants' rhizosphere, when planted in soil, in which the plant species naturally occur. In an 18-month large-scale laboratory mesocosm experiment, two plant species (Holcus lanatus and Lotus corniculatus) producing labile litter and two plant species (Picea abies and Calluna vulgaris) producing recalcitrant litter were placed in the same mesocosm. This allowed the decomposer biota (microbes, protozoa, nematodes, collembolans, and enchytraeid worms) to freely choose their preferred plant rhizosphere. Because a fungal-based energy channel is in theory regarded to retain nutrients better in the soil than a bacterial-based energy channel, water was collected underneath the plant species and analyzed for its nutrient (N and P) content. In general, the number of soil biota groups responding significantly to the plant treatment increased with time. Soil microbes were the first group to react, but the ability of the plants to boost a clearly fungal- or bacterial-based energy channel was generally weak. However, at the end of the study, a higher fungal-to-bacterial biomass ratio was found beneath Calluna than beneath the other plant treatments. Of the secondary consumers, nematodes were the most responsive group, with total number and especially plant parasites being more abundant beneath Lotus than beneath Picea and Calluna indicating a root-based energy channel to persist under the legume. Protozoa, enchytraeid worms and collembolans responded weakly and inconsistently to plant treatment. Liberation of plant-available nutrients was plant-dependent. Towards the end of the study, less nitrate and phosphate leached through the Picea soils than through the control, which indicates a more effective nutrient retention to take place under this plant species. We found that plant species can, in a relatively short time, modify the composition of the soil decomposer community. However, no consistent evidence for the plant-soil systems developing to separated detritus energy channels emerged, we found a clearly separated root energy channel under the legume L. corniculatus.

Herbivores are regulated by predation under certain environmental conditions, whereas under others they are limited by forage abundance and nutritional quality. Whether top-down or bottom-up regulation prevails depends both on abiotic constraints on forage availability and body size, because size simultaneously affects the risk of predation of herbivores and their nutritional demands. Consequently, ecosystems composed of similar species can have different dynamics if they differ in resource supply. Here, we use large herbivore assemblages in African savanna ecosystems to develop a framework that connects environmental gradients and disturbance patterns with body size and trophic structure. This framework provides a model for understanding the functioning and diversity of ecosystems in general, and unifies how top-down and bottom-up mechanisms depend on common underlying environmental gradients.

Herbivores are regulated by predation under certain environmental conditions, whereas under others they are limited by forage abundance and nutritional quality. Whether top-down or bottom-up regulation prevails depends both on abiotic constraints on forage availability and body size, because size simultaneously affects the risk of predation of herbivores and their nutritional demands. Consequently, ecosystems composed of similar species can have different dynamics if they differ in resource supply. Here, we use large herbivore assemblages in African savanna ecosystems to develop a framework that connects environmental gradients and disturbance patterns with body size and trophic structure. This framework provides a model for understanding the functioning and diversity of ecosystems in general, and unifies how top-down and bottom-up mechanisms depend on common underlying environmental gradients.

One of the key issues in compost research is to assess when the compost has reached a mature stage. The maturity status of the compost determines the quality of the final soil amendment product. The nematode community occurring in a Controlled Microbial Composting (CMC) process was analyzed with the objective of assessing whether the species composition could be used as a bio-indicator of the compost maturity status. The results obtained here describe the major shifts in species composition that occur during the composting process. Compared to terrestrial ecosystems, nematode succession in compost differs mainly in the absence of K-strategists and numerical importance of diplogastrids. At the beginning of the composting process (thermophilic phase), immediately after the heat peak, the nematode population is primarily built by bacterial feeding enrichment opportunists (cp-1) (Rhabditidae, Panagrolaimidae, Diplogastridae) followed by the bacterial-feeding general opportunists (cp-2) (Cephalobidae) and the fungal-feeding general opportunists (Aphelenchoididae). Thereafter, during the cooling and maturation stage, the bacterial-feeding-predator opportunistic nematodes (Mononchoides sp.) became dominant. Finally, at the most mature stage, the fungal-feeding Anguinidae (mainly Ditylenchus filimus) were most present. Both, the Maturity Index (MI) and the fungivorous/bacterivorous ratio (f/b ratio), increase as the compost becomes more mature (ranging, respectively, from 1 to 1.86 and from 0 to 11.90). Based on these results, both indices are suggested as potential suitable tools to assess compost maturity.

Abiotic soil properties, plant community composition, and herbivory all have been reported as important factors influencing the composition of soil communities. However, most studies thus far have considered these factors in isolation, whereas they strongly interact in the field. Here, we study how grazing by vertebrate herbivores influences the soil nematode community composition of a floodplain grassland while we account for effects of grazing on plant community composition and abiotic soil properties. Nematodes are the most ubiquitous invertebrates in the soil. They include a variety of feeding types, ranging from microbial feeders to herbivores and carnivores, and they perform key functions in soil food webs.Our hypothesis was that grazing affects nematode community structure and composition through altering plant community structure and composition. Alternatively, we tested whether the effects of grazing may, directly or indirectly, run via changes in soil abiotic properties. We used a long-term field experiment containing plots with and without vertebrate grazers (cattle and rabbits). We compared plant and nematode community structure and composition, as well as a number of key soil abiotic properties, and we applied structural equation modeling to investigate four possible pathways by which grazing may change nematode community composition.Aboveground grazing increased plant species richness and reduced both plant and nematode community heterogeneity. There was a positive relationship between plant and nematode diversity indices. Grazing decreased the number of bacterial-feeding nematodes, indicating that in these grasslands, top-down control of plant production by grazing leads to bottom-up control in the basal part of the bacterial channel of the soil food web.According to the structural equation model, grazing had a strong effect on soil abiotic properties and plant community composition, whereas plant community composition was the main determinant of nematode community composition. Other pathways, which assumed that grazing influenced nematode community composition by inducing changes in soil abiotic properties, did not significantly explain variation in nematode community composition.We conclude that grazing-induced changes in nematode community composition mainly operated via changes in plant community composition. Influences of vertebrate grazers on soil nematodes through modification of abiotic soil properties were of less importance.

In the Netherlands soil biological measurements are undertaken in a nationwide monitoring programme. The measurements are combined in the Biological Indicator of Soil Quality (BISQ). About 300 locations were selected in a random stratified design comprising stringent combinations of land use and soil type. All locations were sampled in a six-year cycle. In this contribution we describe the monitoring network and the BISQ and present average values for biomass, abundances and taxonomic diversity of various soil dwelling organisms derived from 10 years of measurements. We further highlight some results and discuss the possibilities in soil and land management policy frameworks for improving sustainable land management

Summary 1Plant species employ several direct and indirect defence strategies to protect themselves against insect herbivores. Most studies, however, have focused on shoot-induced responses. Much less is known about interactions between below- and above-ground herbivores and how these may affect their respective parasitoids. 2Here, we quantify the impact of below-ground induced responses vs. that of above-ground induced responses in a feral Brassica on the performance of Pieris brassicae and its endoparasitoid Cotesia glomerata. Jasmonic acid (JA) was applied to induce the plants above- or below-ground. The glucosinolate, sugar and amino acid levels of the leaves were analysed. 3Pieris brassicae larvae grew significantly slower on shoot JA-induced (SJA) plants than on root JA-induced (RJA) and control plants, which were treated with acidic water. On RJA and control plants they showed similar developmental trajectories. Pupal masses, survival till eclosion and egg load, however, were similar on all plants. 4The development of C. glomerata larvae on SJA plants was significantly longer than that on RJA and control plants. In contrast, the parasitoid's pupal stage lasted longer in hosts feeding on control plants. The total developmental times eventually were similar in all groups. However, the masses of male and female C. glomerata adults that developed hosts on control and RJA plants were significantly larger than those from hosts on SJA plants. JA application increased total glucosinolate contents and decreased the sugars and total amino acids levels independent of whether JA was applied. However, the trajectories of herbivore-induced glucosinolate levels differed between RJA and SJA plants. 5These results show that the differential effects of above- and below-ground-induced responses on herbivores also affect higher trophic levels in a nonlinear fashion via differential changes in host plant quality. In particular, the indirect effects that below-ground herbivores have on the performance of above-ground parasitoids may exceed the direct effects of plant chemistry on herbivore performance. Consequently, above-ground and below-ground interactions mediated by induced plant responses have the potential to mediate insect community structure and function in complex ways.

International audience; Organic farming may contribute substantially to future agricultural production worldwide by improving soil quality and pest control, thereby reducing environmental impacts of conventional farming. We investigated in a comprehensive way soil chemical, as well as below and aboveground biological parameters of two organic and two conventional wheat farming systems that primarily differed in fertilization and weed management strategies. Contrast analyses identified management related differences between “herbicide-free” bioorganic (BIOORG) and biodynamic (BIODYN) systems and conventional systems with (CONFYM) or without manure (CONMIN) and herbicide application within a long-term agricultural experiment (DOK trial, Switzerland). Soil carbon content was significantly higher in systems receiving farmyard manure and concomitantly microbial biomass (fungi and bacteria) was increased. Microbial activity parameters, such as microbial basal respiration and nitrogen mineralization, showed an opposite pattern, suggesting that soil carbon in the conventional system (CONFYM) was more easily accessible to microorganisms than in organic systems. Bacterivorous nematodes and earthworms were most abundant in systems that received farmyard manure, which is in line with the responses of their potential food sources (microbes and organic matter). Mineral fertilizer application detrimentally affected enchytraeids and Diptera larvae, whereas aphids benefited. Spider abundance was favoured by organic management, most likely a response to increased prey availability from the belowground subsystem or increased weed coverage. In contrast to most soil-based, bottom-up controlled interactions, the twofold higher abundance of this generalist predator group in organic systems likely contributed to the significantly lower abundance of aboveground herbivore pests (aphids) in these systems. Long-term organic farming and the application of farmyard manure promoted soil quality, microbial biomass and fostered natural enemies and ecosystem engineers, suggesting enhanced nutrient cycling and pest control. Mineral fertilizers and herbicide application, in contrast, affected the potential for top-down control of aboveground pests negatively and reduced the organic carbon levels. Our study indicates that the use of synthetic fertilizers and herbicide application changes interactions within and between below and aboveground components, ultimately promoting negative environmental impacts of agriculture by reducing internal biological cycles and pest control. On the contrary, organic farming fosters microbial and faunal decomposers and this propagates into the aboveground system via generalist predators thereby increasing conservation biological control. However, grain and straw yields were 23% higher in systems receiving mineral fertilizers and herbicides reflecting the trade-off between productivity and environmental responsibility.

This paper presents an overview of the possibilities for further development of tools and. approaches for the ecological assessment and management of diffusively contaminated ecosystems. It is based on the results of the "Netherlands Stimulation Programme on Ecosystem-oriented Ecotoxicological Research", the SSEO programme, which ran from 1998 to 2006, and on opinions of international experts on ecological and ecotoxicological risk-assessment methods and their legal applications. The paper also discusses the pros and cons of the set-up of the SSEO programme. Proper management of diffusively polluted areas has to be based on an integral risk-based and system approach. The approach has to be founded on the relationships between pollution, natural stresses, management measures and the presence and activities of specific species. Furthermore, the relationships between biodiversity in ecosystems and its stability and functioning have to be known. The assessment of aquatic ecosystem quality is now based on the comparisons of the composition of actual species with that of reference species. This type of system does not yet exist for the assessment of soil quality, but it is being developed. It is shown that ecological quality criteria based on a Species Sensitivity Distributions approach are sufficiently conservative to avoid or prevent major ecological impacts of diffuse pollution at concentrations below legal standards. However, a proper quality relationship of biodiversity and ecosystem functioning is lacking in the ecological assessment methods. Future research should focus on the relationship of ecosystem structure (species composition) and ecosystem functioning and on the impact of disturbing the environment and appropriate management measures. © 2008 Elsevier B.V. All rights reserved.

Interactions between above- and belowground invertebrate herbivores alter plant diversity, however, little is known on how these effects may influence higher trophic level organisms belowground. Here we explore whether above- and belowground invertebrate herbivores which alter plant community diversity and biomass, in turn affect soil nematode communities. We test the hypotheses that insect herbivores 1) alter soil nematode diversity, 2) stimulate bacterial-feeding and 3) reduce plant-feeding nematode abundances. In a full factorial outdoor mesocosm experiment we introduced grasshoppers (aboveground herbivores), wireworms (belowground herbivores) and a diverse soil nematode community to species-rich model plant communities. After two years, insect herbivore effects on nematode diversity and on abundance of herbivorous, bacterivorous, fungivorous and omni-carnivorous nematodes were evaluated in relation to plant community composition. Wireworms did not affect nematode diversity despite enhanced plant diversity, while grasshoppers, which did not affect plant diversity, reduced nematode diversity. Although grasshoppers and wireworms caused contrasting shifts in plant species dominance, they did not affect abundances of decomposer nematodes at any trophic level. Primary consumer nematodes were, however, strongly promoted by wireworms, while community root biomass was not altered by the insect herbivores. Overall, interaction effects of wireworms and grasshoppers on the soil nematodes were not observed, and we found no support for bottom-up control of the nematodes. However, our results show that above- and belowground insect herbivores may facilitate root-feeding rather than decomposer nematodes and that this facilitation appears to be driven by shifts in plant species composition. Moreover, the addition of nematodes strongly suppressed shoot biomass of several forb species and reduced grasshopper abundance. Thus, our results suggest that nematode feedback effects on plant community composition, due to plant and herbivore parasitism, may strongly depend on the presence of insect herbivores

14 pages, 5 figures, 3 tables, supplementary material http://dx.doi.org/10.3354/meps11188, Understanding how marine predators interact is a scientific challenge. In marine ecosystems, segregation in feeding habits has been largely described as a common mechanism to allow the coexistence of several competing marine predators. However, little is known about the feeding ecology of most species of chondrichthyans, which play a pivotal role in the structure of marine food webs worldwide. In this study, we examined the trophic ecology of 3 relatively abundant chondrichthyans coexisting in the Mediterranean Sea: the blackmouth catshark Galeus melastomus, the velvet belly lanternshark Etmopterus spinax and the rabbit fish Chimaera monstrosa. To examine their trophic ecology and interspecific differences in food habits, we combined the analysis of stomach content and stable isotopes. Our results highlighted a trophic segregation between C. monstrosa and the other 2 species. G. melastomus showed a diet composed mainly of cephalopods, while E. spinax preyed mainly on shrimps and C. monstrosa on crabs. Interspecific differences in the trophic niche were likely due to different feeding capabilities and body size. Each species showed different isotopic niche space and trophic level. Specifically, C. monstrosa showed a higher trophic level than E. spinax and G. melastomus. The high trophic levels of the 3 species highlighted their important role as predators in the marine food web. Our results illustrate the utility of using complementary approaches that provide information about the feeding behaviour at short (stomach content) and long-term scales (stable isotopes), which could allow more efficient monitoring of marine food-web changes in the study area, M.A.-P. was supported by a predoctoral fellowship of the FPI program (Spanish Ministry of Economy and Competitiveness). J.N. was supported by a research contract of the Marie Curie GIC project BioWeb. M.C. and J.A. are supported by a post-doctoral contract of the Ramon y Cajal Program (Spanish Ministry of Economy and Competiveness), and M.C. was also supported by BioWeb project. This study is a contribution to the project ECOTRANS (CTM2011-26333, Ministerio de Economía y Competitividad, Spain)

International audience; Seagrass patches interspersed in a sediment matrix may vary environmental conditions and affect feeding habits of consumers and food-web structure. This paper investigates diet shifts between bare sediments and a Zostera noltei (Hornemann, 1832) meadow for three facultative deposit-feeding macrofaunal consumers, notably the bivalve Scrobicularia piano (da Costa, 1778), the polychaete Hediste diversicolor (O.T. Muller, 1776), and the gastropod Hydrobia ulvae (Pennant, 1778). In July 2008, one eelgrass meadow and two bare sediment locations were chosen in the Mondego estuary (40 degrees 08" N, 8 degrees 50'W, Portugal) and sampled for stable isotope signatures (delta C-13 and delta N-15) of macrofauna consumers and some of their potential basal food sources, such as sedimentary organic matter (SOM), microphytobenthos (MPB), seagrass shoots, leaves and seaweeds laying on the surface sediment. The delta N-15 of H. diversicolor was 3% higher in the eelgrass meadow than in bare sediment, indicating a change of trophic position, whereas the Bayesian stable-isotope mixing model showed that S. piano assimilated more macroalgal detritus than microphytobenthos in the eelgrass bed. Such habitat-related diet shifts have the potential to change structure and spatial dynamics of benthic food webs.

Non-native species introductions are widespread and can affect ecosystem functioning by altering the structure of food webs. Invading plants often modify habitat structure, which may affect the suitability of vegetation as refuge and could thus impact predator-prey dynamics. Yet little is known about how the replacement of native by non-native vegetation affects predator-prey dynamics. We hypothesize that plant refuge provisioning depends on (1) the plant’s native status, (2) plant structural complexity and morphology, (3) predator identity, and (4) prey identity, as well as that (5) structurally similar living and artificial plants provide similar refuge. We used aquatic communities as a model system and compared the refuge provided by plants to macroinvertebrates (Daphnia pulex, Gammarus pulex and damselfly larvae) in three short-term laboratory predation experiments. Plant refuge provisioning differed between plant species, but was generally similar for native (Myriophyllum spicatum, Ceratophyllum demersum, Potamogeton perfoliatus) and non-native plants (Vallisneria spiralis, Myriophyllum heterophyllum, Cabomba caroliniana). However, plant refuge provisioning to macroinvertebrate prey depended primarily on predator (mirror carp: Cyprinus carpio carpio and dragonfly larvae: Anax imperator) and prey identity, while the effects of plant structural complexity were only minor. Contrary to living plants, artificial plant analogues did improve prey survival, particularly with increasing structural complexity and shoot density. As such, plant rigidity, which was high for artificial plants and one of the living plant species evaluated in this study (Ceratophyllum demersum), may interact with structural complexity to play a key role in refuge provisioning to specific prey (Gammarus pulex). Our results demonstrate that replacement of native by structurally similar non-native vegetation is unlikely to greatly affect predator-prey dynamics. We propose that modification of predator-prey interactions through plant invasions only occurs when invading plants radically differ in growth form, density and rigidity compared to native plants.

Made available in DSpace on 2019-09-12T16:53:28Z (GMT). No. of bitstreams: 0 Previous issue date: 2015 Ministério do Meio Ambiente (MMA) Ministério da Ciência, Tecnologia e Inovação (MCTI) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Secretariat of the Interministerial Commission for the Resources of the Sea (SeCIRM) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) The well-being, feeding habits and energetic and plasmatic parameters of the notothenioids Notothenia rossii and Notothenia coriiceps were assessed in specimens collected at a depth of up to 25 m in the Admiralty Bay region, King George Island, Antarctic Peninsula. The population structure of N. rossii (n = 221) was composed of juveniles, and that of N. coriiceps (n = 151) was composed of adults. The greatest mean length and weight measurements of N. coriiceps may be related to warming waters in the Antarctic Peninsula region. Salps were the dominant item in the diet of both species responsible for high protein quantity item found in muscle tissues and liver. The krill and amphipods were an important food item and related to lipid reserves. Among the indices evaluated, greater variation was observed in the hepatosomatic index of N. coriiceps and was related to the greater sizes and ages attained by this species. The liver and muscle energetic components showed great variability between different months may be related by the variability in diet. The plasma components did not exhibit seasonal patterns but displayed large monthly variation. Long-term analysis of the biological parameters evaluated in this study should be continued to monitor the species present in Admiralty Bay, a region with great biological diversity. [Raga, Gabriela; Pichler, Helen Audrey; Zaleski, Tania; Vaz da Silva, Flavia Baduy; Machado, Cintia; Rios, Flavia Sant'Anna; Donatti, Lucelia] Univ Fed Parana, Dept Cell Biol, Adapt Biol Lab, BR-80060000 Curitiba, Parana, Brazil [Rodrigues, Edson] Universidade de Taubaté (Unitau), Basic Biosci Inst, Sao Paulo, Brazil [Kawall, Helena Goncalves] Univ Sao Paulo, Oceanog Inst, Sao Paulo, Brazil

Bioaccumulative and biomagnifying contaminants, such as persistent organic pollutants (POPs) and mercury (Hg), have for decades been recognized as a health concern in arctic marine biota. In recent years, global climate change (GCC) and related loss of arctic sea ice have been observed to be driving substantial change in arctic ecosystems. This review summarizes findings documenting empirical links between GCC-induced ecological changes and alterations in POP and Hg exposures and pathways in arctic marine ecosystems. Most of the studies have reported changes in POP or Hg concentrations in tissue in relation to GCC-induced changes in species trophic interactions. These studies have typically focused on the role of changes in abundance, habitat range or accessibility of prey species, particularly in relation to sea ice changes. Yet, the ecological change that resulted in contaminant trend changes has often been unclear or assumed. Other studies have successfully used chemical tracers, such as stable nitrogen and carbon isotope ratios and fatty acid signatures to link such ecological changes to contaminant level variations or trends. Lower sea ice linked-diet changes/variation were associated with higher contaminant levels in some populations of polar bears, ringed seals, and thick-billed murres, but the influence of changing trophic interactions on POP levels and trends varied widely in both magnitude and direction. We suggest that future research in this new area of GCC-linked ecotoxicology should focus on routine analysis of ancillary ecological metrics with POP and Hg studies, simultaneous consideration of the multiple mechanisms by which GCC and contaminant interactions can occur, and targeted research on changing exposures and toxicological effects in species known to be sensitive to both GCC and contaminants.

The western Antarctic Peninsula is experiencing strong environmental changes as a consequence of ongoing regional warming. Glaciers in the area are retreating rapidly and increased sediment-laden meltwater runoff threatens the benthic biodiversity at shallow depths. We identified three sites with a distinct glacier-retreat related history and different levels of glacial influence in the inner part of Potter Cove (King George Island, South Shetland Islands), a fjord-like embayment impacted since the 1950s by a tidewater glacier retreat. We compared the soft sediment meio- and macrofauna isotopic niche widths (d13C and d15N stable isotope analysis) at the three sites to investigate possible glacier retreat-related influences on benthic trophic interactions. The isotopic niches were locally shaped by the different degrees of glacier retreat-related disturbance within the Cove. Wider isotopic niche widths were found at the site that has become ice-free most recently, and narrower niches at the older ice-free sites. At an intermediate state of glacier retreat-related disturbance (e.g. via ice-growler scouring) species with different strategies could settle. The site at the earliest stage of post-retreat development was characterized by an assemblage with lower trophic redundancy. Generally, the isotopic niche widths increased with increasing size spectra of organisms within the community, excepting the youngest assemblage, where the pioneer colonizer meiofauna size class displayed the highest isotopic niche width. Meiofauna at all sites generally occupied positions in the isotopic space that suggested a detrital-pool food source and/or the presence of predatory taxa. In general ice scour and glacial impact appeared to play a two-fold role within the Cove: i) either stimulating trophic diversity by allowing continuous re-colonization of meiofaunal species or, ii) over time driving the benthic assemblages into a more compact trophic structure with increased connectedness and resource recycling.

The colony-forming microalgae Phaeocystis produces two major pools of carbohydrates: in mucopolysaccharides in the colony matrix and intracellular storage glucan. Both have different functions and separate degradation pathways in the ecosystem, so a partial precipitation method was developed to distinguish the dynamics of the two pools. Changes in concentration in response to variation in nutrients and irradiance were followed during a spring bloom of Phaeocystis pouchetii colonies in mesocosms near Bergen, Norway. Upon nutrient limitation, the carbohydrate to carbon ratio of the colonies increased from 15% during the growth phase, to more than 50% during the decline phase. During the growth phase of the bloom, the carbohydrate concentration and composition were influenced by irradiance: glucan concentrations showed strong diel dynamics and increased with higher light levels, whereas mucopolysaccharide concentrations were unaffected. During the exponential growth phase, glucan contributed 6-11% to P. pouchetii carbon, depending on the time of the day. During the decline of the bloom, the glucan contribution increased up to 60%. We provide further evidence for the concept that the Phaeocystis colony matrix is built with a relatively small but constant amount of carbohydrates, compared to the large quantities of glucan produced during Phacocystis spring blooms. Since a major part of Phaeocystis primary production is recycled in the water column by bacteria, this vast glucan injection is a potential determinant of the magnitude and composition of the microbial community following a bloom. (c) 2005 Elsevier B.V. All rights reserved.

Recent studies have suggested that root-feeding nematodes influence plant community dynamics, but few studies have investigated the population dynamics of the nematodes. In coastal foredunes, feeding-specialist cyst nematodes (Heterodera spp.) are dominant in the soil nematode community and greenhouse studies pointed at bottom-up control by their host plant. Here we examine the population dynamics of H. arenaria in the field in relation to resource quantity in the root zone of Ammophila arenaria (marram grass). Ammophila arenaria is a pioneer grass in mobile coastal foredunes of northwestern and Mediterranean Europe. Every year, the plant expands clonally into freshly deposited layers of wind-blown sand, followed by dispersal and build-up of the nematode population into the new root zone. In a newly developing root zone the first H. arenaria cysts were observed one month after the first new roots were detected, indicating that nematode dispersal is not limiting the initial establishment of new populations. Throughout the growth season, the numbers of cysts, as well as the numbers of eggs and juveniles within cysts, were related to the quantity of roots. However, cyst density varied between years. Therefore, we conclude that in new root layers of A. arenaria cyst nematodes are bottom-up controlled by resource quantity, but that other factors, for example resource quality, influence the relation between nematode abundance and resource quantity. In deeper root zones the nematode abundance declines over time. Here, numbers of cysts were not related to root biomass, while numbers of eggs and juveniles inside the cysts were weakly related. This points at other factors than resource quantity, for example the quality of the roots or unsuitable abiotic environmental conditions that have a stronger influence on cyst numbers than resource quantity. We discuss how bottom-up control of cyst nematodes may indirectly protect the plant against harmful root knot nematodes.

The organisms of the soil food web, dependent on resources from plants or on amendment from other sources, respond characteristically to enrichment of their environment by organic matter. Primary consumers of the incoming substrate, including bacteria, fungi, plant-feeding nematodes, annelids, and some microarthropods, are entry-level indicators of enrichment. However, the quantification of abundance and biomass of this diverse group, as an indicator of resource status, requires a plethora of extraction and assessment techniques. Soluble organic compounds are absorbed by bacteria and fungi, while fungi also degrade more recalcitrant sources. These organisms are potential indicators of the nature of incoming substrate, but current methods of biomass determination do not reliably indicate their community composition. Guilds of nematodes that feed on bacteria (e.g., Rhabditidae, Panagrolaimidae) and fungi (e.g., Aphelenchidae, Aphelenchoididae) are responsive to changes in abundance of their food. Through direct herbivory, plant-feeding nematodes (e.g., many species of Tylenchina) also contribute to food web resources. Thus, analysis of the nematode community of a single sample provides indication of carbon flow through an important herbivore channel and through channels mediated by bacteria and fungi. Some nematode guilds are more responsive than others to resource enrichment. Generally, those bacterivores with short life-cycles and high reproductive potential (e.g., Rhabditidae) most closely mirror the bloom of bacteria or respond most rapidly to active plant growth. The feeding habits of some groups remain unclear. For example, nematodes of the Tylenchidae may constitute 30% or more of the individuals in a soil sample; further study is necessary to determine which resource channels they portray and the appropriate level of taxonomic resolution for this group. A graphic representation of the relative biomass of bacterivorous, fungivorous, and herbivorous nematodes provides a useful tool for assessing the importance of the bacterial, fungal, and plant resource channels in an extant food web

Conversion of arable land into semi-natural grassland or heath land is a common practice for restoring and conserving plant diversity. However, little is known about the effectiveness of land conversion for restoring and conserving taxonomic and functional diversity in the soil. We studied soil nematode community development in a chronosequence of abandoned fields and related this to plant community development. The taxonomic and functional composition of the soil nematode community was analyzed to detect changes in soil food web structure, using semi-natural sites and theoretical plant and soil communities as references. While plant communities clearly developed towards the semi-natural references, there was less direction in succession of nematode taxa. The number of fungal feeding nematodes increased after land abandonment. Numbers of omni-carnivorous nematodes expanded only during the first years, after which there were no substantial changes for the next three decades. Plant communities on the ex-arable fields developed towards the theoretical reference plant associations Galio hercynici-Festucetum ovinae and Genisto anglicae-Callunetum . Nematode communities developed away from a theoretical community indicative of arable land, but there was no clear development towards a theoretical (semi-)natural reference. Our results show that restoration and conservation of plant communities is of limited indicative value for developments belowground: successful restoration of plant diversity does not necessarily imply successful restoration of belowground diversity. Assessing the impact of conservation measures on restoring soil biodiversity requires information on belowground community composition of (semi-)natural areas in order to establish proper references for restoration sites.