1,720,982 research outputs found
Spatial variation in growth rate of early juvenile European plaice Pleuronectes platessa
No full textPatterns and causes of spatial variation in RNA-predicted growth rates in mid-August were examined in young-of-the-year European plaice Pleuronectes platessa (‘YOY plaice’) at 22 beaches along a 300 km stretch of coastline in west Scotland in 3 consecutive years. According to restricted maximum likelihood models, growth rates varied among beaches (25 km scale), but these spatial patterns were not consistent across years. We found no evidence for spatial variation in growth at the scale of subregions (50 km) or regions (100 km). Growth rate was positively correlated with total length, both within and among beaches and years. In general, YOY plaice in mid-August grew more slowly than estimated ad libitum laboratory rates. Average growth rates by beach and year were inversely related to intraspecific competitor densities, but not interspecific competitor densities (brown shrimp Crangon crangon) or 2 environmental productivity metrics (nearshore chlorophyll a concentration and lugworm Arenicola marina cast density). Physical beach characteristics also explained a significant source of spatial growth variation, with fish growing faster at beaches with larger tidal range and wave fetch. Therefore, the hypothesis of sub-maximum growth due to intraspecific competition (density-dependent growth) was supported, but additional, previously unexplored processes related to physical beach characteristics appear to have important influences on the spatial growth dynamics of YOY plaice
Decline in growth rate of juvenile European plaice (Pleuronectes platessa) during summer at nursery beaches along the west coast of Scotland
No full textThis study concludes that declines in growth rates of young-of-the-year European plaice (Pleuronectes platessa) (YOY plaice) during summer vary spatially and between years and that these dynamics are not driven by temperature, body size, or competition. RNA-predicted growth rates of YOY plaice on the west coast of Scotland declined linearly between mid-July and mid-September, with faster declines at beaches and in years where growth rates were initially high. Absolute growth estimates rarely approached ad libitum laboratory rates, and relative declines in growth rates were unrelated to temperature or body size allometry, indicating that maximum growth was rare. However, the absence of inverse relationships between spatial or temporal growth variation and YOY plaice or brown shrimp (Crangon crangon) densities suggests that competition did not limit growth. There were no consistent trends in morphometric condition factor, biochemical composition, or energy content during summer, indicating that apparent growth declines did not result from energy storage and did not result in depletion of energy stores. Influences of extrinsic factors (such as prey conditions, physical disturbance, and predator densities) on the diet, mediated by behavioral decisions to optimize growth with other ecological constraints, require further investigation as causes of growth variation in YOY plaice
Spatial variation in the gastrointestinal microbiome, diet, and nutritional condition of a juvenile flatfish among coastal habitats
Full text linkGut microbiota are important for the health, fitness and development of animal hosts, but little is known about these assemblages in wild populations of fish. Such knowledge is particularly important for juvenile life stages where nutritional intake critically determines early development, growth, and ultimately recruitment. We characterise the microbiome inhabiting the gut of young-of-the-year European plaice (‘YOY plaice’) on sandy beaches, their key juvenile habitat, and examine how these microbial communities vary spatially in relation to diet and nutritional condition of their plaice hosts. Body size, diet (stomach fullness and eukaryotic 18S ribosomal sequencing), nutritional condition (RNA:DNA) and gut microbiota (16S prokaryotic ribosomal sequencing) were compared in fish at two spatial scales: between beaches separated by 10s of kilometres and between sites at different depths on the same beach, separated by 10s of metres. The main microbial phyla in YOY plaice guts were Proteobacteria, Spirochaetes, Tenericutes and Verrucomicrobiae. Within the Proteobacteria there was an unusual dominance of Alphaproteobacteria. Differences in body size, diet and nutritional condition of YOY plaice between beaches were accompanied by differences in gut microbial assemblage structure. Notably, substantially reduced nutritional condition and size at one of the beaches was associated with lower stomach fullness, reduced consumption of annelids and differences in the abundance and presence of specific microbial taxa. Differences were also detected in microbial assemblages, body size, and diet between depths within the same nursery beach, although stomach fullness and nutritional condition did not vary significantly. The functional links between the environment, gut microbiota, and their hosts are potentially important mediators of the development of young fish through critical life stages. Our study indicates that these links need to be addressed at 10 km and even 10 m scales to capture the variability observed in wild populations of juvenile fish.</p
Sensitivity to near-future CO<sub>2</sub> conditions in marine crabs depends on their compensatory capacities for salinity change
Full text linkMarine crabs inhabit shallow coastal/estuarine habitats particularly sensitive to climate change, and yet we know very little about the diversity of their responses to change. We report the effects of a rarely studied, but increasingly prevalent, combination of environmental factors, that of near-future pCO2 (~1000 µatm) and a physiologically relevant 20% reduction in salinity. We focused on two crab species with differing abilities to cope with natural salinity change, and revealed via physiological and molecular studies that salinity had an overriding effect on ion exchange in the osmoregulating shore crab, Carcinus maenas. This species was unaffected by elevated CO2, and was able to hyper-osmoregulate and maintain haemolymph pH homeostasis for at least one year. By contrast, the commercially important edible crab, Cancer pagurus, an osmoconformer, had limited ion-transporting capacities, which were unresponsive to dilute seawater. Elevated CO2 disrupted haemolymph pH homeostasis, but there was some respite in dilute seawater due to a salinity-induced metabolic alkalosis (increase in HCO3- at constant pCO2). Ultimately, Cancer pagurus was poorly equipped to compensate for change, and exposures were limited to 9 months. Failure to understand the full spectrum of species-related vulnerabilities could lead to erroneous predictions of the impacts of a changing marine climate
No evidence for impacts to the molecular ecophysiology of ion or CO2 regulation in tissues of selected surface-dwelling bivalves in the vicinity of a sub-seabed CO2 release
Full text linkWhilst sub-seabed Carbon Capture and Storage (CCS) has the potential to remove a significant proportion of anthropogenic CO2 emissions at source, research is necessary to constrain the environmental impacts of potential future gas leaks from storage reservoirs. The QICS project (Quantifying and Monitoring Potential Ecosystem Impacts of Geological Carbons Storage) was established to improve our understanding of these potential impacts and to develop tools and best practice for monitoring sub-seabed CCS reservoirs. Exposure to increased environmental CO2 has been shown to raise the tissue pCO2 of many marine invertebrate species, leading to tissue acidosis and perturbations in both ion transport and bicarbonate buffering. These disturbances can cause downstream effects, seen as metabolic depression in susceptible organisms, compromising the role of particular species within an ecosystem and even causing the local extinction of species groups. To monitor the potential impact to surficial benthic megafauna, cages of bivalves (the common mussel Mytilus edulis Linnaeus, 1758 and the king scallop Pecten maximus (Linnaeus, 1758)) were deployed at the gas release site and at a reference site—both within Ardmucknish Bay, Oban, Scotland. Replicate individuals were sampled at six time points over a 125-day period, which spanned both the 37-day injection and recovery phases of the experiment, in order to establish impacts to molecular physiology. Samples of bivalves were also simultaneously sampled from a reference site within the bay in order to contrast changes in physiology induced by the gas release with naturally variability in the physiological performance of both species. We present data on changes in the transcription of genes coding for key ionic and carbon dioxide regulatory proteins. There was no evidence of gene regulation of either selected carbonic anhydrases (CAx genes) or the alpha subunit of sodium potassium ATPAses (ATP1A genes) in individual bivalves collected from the CO2 gas release site, in either species. In the common mussel M. edulis there was only evidence for changes with time in the expression of genes coding for different classes of carbonic anhydrase. It was therefore concluded that the effects of the plume of elevated pCO2 on ion-regulatory gene transcription were negligible in both species. Whilst the analysed data from this current study do not constitute an impediment to the continued development of sub-seabed CCS as a climate mitigation strategy, further modelling is necessary to predict the consequences of larger or longer term leaks. Further analysis is also required in order to constrain the potential physiological impacts of gas leaks to benthic infaunal species and understand the mechanism of possible avoidance behaviour recorded in burrowing heart urchins Echinocardium cordatum (Pennant, 1777)
Small-scale spatial and temporal heterogeneity in growth and condition of juvenile fish on sandy beaches
No full textTo characterize fine-grained heterogeneity in the functional role of sandy beaches as fish nurseries, we measured RNA concentration, DNA concentration and RNA-predicted growth rate in young-of-the-year European plaice Pleuronectes platessa L. (‘YOY plaice’) at beaches on the western side of the British Isles at small alongshore (100–500 m), temporal (days to weeks), depth (0.5–2 m below waterline) and inter-individual scales. We compared variations in these nucleic-acid-based metrics of condition and growth with a null metric (total length) considered to be less responsive to short-term changes in environmental conditions. All four metrics varied at small spatial and temporal scales, particularly RNA-based metrics of short-term condition and growth. A decline in condition and growth during summer was the most important source of temporal variation. Condition and growth also increased with depth below waterline. Alongshore variations within a beach were relatively small, but variance among stations on the same beach (500 m scale) was similar in magnitude to variance among beaches separated by 100 km. High variance in nucleic acid concentrations among samples resulted not only from technical error but also from inter-individual variation. Our application of high-resolution biochemical indices therefore demonstrates that functional roles of sandy beaches can be structured at remarkably small spatial (500 m) and temporal (days) scales, within a single beach
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Growth dynamics of European plaice Pleuronectes platessa L. in nursery areas: a review
No full textYoung-of-the-year European plaice Pleuronectes platessa L. (hereafter: ‘YOY plaice’) in shallow, sandy areas is a long- and intensively-studied species and an ideal model for understanding growth dynamics in fish nurseries. In order to provide an overview of and access point to this rich literature and to guide future research on juvenile fish growth dynamics, we review patterns of growth variation in YOY plaice following settlement and evaluate evidence for underlying causes, including maximum growth, temperature, prey conditions and competition. A decline in growth rate during late summer and autumn was the clearest and most widespread pattern, but was not clearly related to any of the potential causes previously considered. Interannual growth variation was substantial and despite evidence that intraspecific competition was responsible, other possible causes were also supported and others were only rarely assessed. Growth also varied considerably at a range of spatial scales (100s of m–100s of km). Causes of small-scale (< 10 km) and regional (> 200 km) growth variation remain poorly understood and while intermediate-scale growth variation has been related to prey conditions and intraspecific competition, the role of interspecific competition requires further investigation. Therefore, despite clear evidence for growth heterogeneity at numerous spatiotemporal scales, underlying causes remain elusive. We highlight some principal challenges to measuring and understanding the complex and scale-dependent causes of growth variation. To overcome these challenges, and therefore resolve important nursery processes for juvenile fish, we recommend more detailed and spatiotemporally explicit investigations of growth, metabolic processes and physiological energetics in situ; a focus on possible proximate and ultimate factors driving these dynamics; and development of new hypotheses to explain growth variation starting with general physical features that define nursery environments
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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