47 research outputs found
Individual trophic specialization in juvenile European seabass: implications for the management of a commercially important species
No full textIndividual differences in diet can play an important role defining a population's ecological niche and its role within food webs and habitats, but individual trophic specialization is rarely considered in a fisheries context. Stocks of European seabass, Dicentrarchus labrax, have declined in recent years, and policy has focused on managing fishing effort. Inshore nursery grounds represent a critical habitat in terms of recruitment to standing stocks, and improved understanding of the ecology of juvenile seabass at the level of the individual may assist the development of management strategies aimed at maximizing their survival and growth. We quantified levels of individual trophic specialization in juvenile seabass using stomach contents and stable isotope analyses at a monthly resolution over an annual cycle. We found significant, seasonally varying levels of individual specialization in stomach contents, with reduced specialization observed in the spring. This was corroborated by stable isotope analyses, where isotopic variance among seabass individuals was significantly higher compared to that in two other concurrently sampled, sympatric bentho-pelagic predators. Our findings suggest that juvenile seabass form trophic-generalist populations composed of specialized individuals. Considering variation in individual behaviours may improve management strategies aimed at protecting the vulnerable life stages of this commercially important species
Stable isotopes demonstrate seasonally stable benthic-pelagic coupling as newly-fixed nutrients are rapidly transferred through food chains in an estuarine fish community
No full textSeasonal differences in the availability of resources potentially result in food web architecture also varying through time. Stable isotope analyses are a logistically simple but powerful tool for inferring trophic interactions and food web structure, but relatively few studies quantify seasonal variations in food web structure or nutrient flux across multiple trophic levels. We determined the temporal dynamics in stable isotope compositions (carbon, nitrogen and sulfur) of a fish community from a highly seasonal, temperate estuary sampled monthly over a full annual cycle. Sulfur isotope values in fish tissues discriminated among consumers exploiting pelagic and benthic resources but showed no seasonal variation. This implied limited change in the relative consumption of pelagic and benthic resources by the fish community over the study period despite major seasonal changes in phytoplankton biomass. Conversely carbon and nitrogen isotope values exhibited seasonality marked by the commencement of the spring phytoplankton bloom and peak chlorophyll concentration, with δ13C values following expected trends in phytoplankton growth physiology and variation in δ15N values coinciding with changes in major nitrogen sources to plankton between nitrate and ammonium. Isotope shifts in fish muscle were detected within two weeks of the peak spring phytoplankton bloom, suggesting a rapid trophic transfer of carbon and nitrogen along food chains within the estuarine food web during periods of high production. We therefore caution against the assumption that temporal averaging effectively dampens isotopic variability in tissues of higher trophic level animals in highly dynamic ecosystems such as temperate estuaries. This work highlights how stable isotope analyses can be combined with environmental data to gain broader understanding of ecosystem functioning, while emphasising the need for temporally appropriate sampling in stable isotope-based studies
Tracing basal resource use across sea-ice, pelagic, and benthic habitats in the early Arctic spring food web with essential amino acid carbon isotopes
No full textA rapidly warming Arctic Ocean and associated sea-ice decline is resulting in changing sea-ice protist communities, affecting productivity of under-ice, pelagic, and benthic fauna. Quantifying such effects is hampered by a lack of biomarkers suitable for tracing specific basal resources (primary producers and microorganisms) through food webs. We investigate the potential of ẟ13C values of essential amino acids (ẟ13CEAA values) to estimate the proportional use of diverse basal resources by organisms from the under-ice (Apherusa glacialis), pelagic (Calanus hyperboreus) and benthic habitats (sponges, sea cucumber), and the cryo-pelagic fish Boreogadus saida. Two approaches were used: baseline ẟ13CEAA values, i.e. the basal resource specific ẟ13CEAA values, and ẟ13CEAA fingerprints, or mean-centred baseline ẟ13CEAA values. Substantial use of sub-ice algae Melosira arctica by all studied organisms suggests that its role within Arctic food webs is greater than previously recognised. In addition, ẟ13CEAA fingerprints from algae-associated bacteria were clearly traced to the sponges, with an individually variable kelp use by sea cucumbers. Although mean-centred ẟ13CEAA values in A. glacialis, C. hyperboreus, and B. saida tissues were aligned with microalgae resources, they were not fully represented by the filtered pelagic- and sea-ice particulate organic matter constituting the spring diatom-dominated algal community. Under-ice and pelagic microalgae use could only be differentiated with baseline ẟ13CEAA values as similar microalgae clades occur in both habitats. We suggest that ẟ13CEAA fingerprints combined with microalgae baseline ẟ13CEAA values are an insightful tool to assess the effect of ongoing changes in Arctic basal resources on their use by organisms
Matthew’s Emmanuel Messiah: a paradigm of presence for god's people
No full textThe motif of divine presence is a clear phenomenon within the Gospel of Matthew. The modern critical means for assessing the ancient biblical text have multiplied to the point, some claim, of disparity. This study employs both narrative and redaction criticism in an attempt to respond authentically to the structural, historical and theological dimensions of Matthew's Gospel. This study begins with the presumption of the wholeness and integrity of Matthew's narrative, and assumes the gospel story to have an inherently dramatic structure which invites readers to inhabit imaginatively its narrative world and respond to its call. But since we are concerned with the role of both reader and author, this study also assumes a text with an historical author and context. The introduction focuses on the meta-critical dilemma facing New Testament students - what is the text and how do we read it? - and seeks some balance in terms of Krieger's analogy of the text as both window and mirror. Proposed is a narrative reading of Matthew's presence motif alongside a redaction critical assessment of it. In Chapter 2 the elements of narrative theory are introduced and relevant terms defined: the structure of narrative, the function of the narrator, points of view. Chapter 3 becomes an exercise in narrative reading, with Matthew's presence motif providing the focus, and the implied reader’s interaction with the story being predominant in interpretation. Characters, rhetorical devices, and points of view are discussed, to understand the motif's development throughout the story's progress. The thrust of Chapter 4 is thereafter to examine divine presence as a dominant motif within Matthew's most important literary context: the Jewish scriptures. Here the primary paradigms of divine presence provided by the Patriarchs, the Sinai experience, and the Davidic-Zion traditions are assessed. Chapter 5 follows with a more detailed examination of the OT "I am with you/God is with us" formula and its µeo' vµwv/ηuwv language, so strongly connected to Matthew's presence motif. Chapters 6-8 build on these investigations with a closer analysis of the three critical "presence passages" of Mt 1:23. 18:20 and 28:20. The passages and their contexts are probed from a redaction critical perspective, guided by the narrative investigation of Chapter 3, and the background from Chapters 4 and 5.The three major "presence passages" examined in Chapters 6-8 are also complimented by a number of secondary issues: worship, wisdom, the Spirit and the poor in Matthew, and their relation to Jesus' divine presence. These are discussed in Chapter 9. Chapter 10 summarizes and looks briefly at some implications. Matthew' presence motif proves to be an important element of the Gospel’s rhetorical design, redactional strategy and Christology. The presence of Jesus, the Emmanuel Messiah, exhibited in his risen authority, becomes the focus of his people's hopes and experiences in the post-Easter world. What the presence of Yahweh was to his people. Jesus now provides in a new paradigm for his people - his followers, the little ones, the poor and the marginalized, from all nations
Two Functional Epithelial Sodium Channel Isoforms Are Present in Rodents despite Pronounced Evolutionary Pseudogenization and Exon Fusion
No full textThe epithelial sodium channel (ENaC) plays a key role in salt and water homeostasis in tetrapod vertebrates. There are four ENaC subunits (α, β, γ, δ), forming heterotrimeric αβγ- or δβγ-ENaCs. While the physiology of αβγ-ENaC is well understood, for decades the field has stalled with respect to δβγ-ENaC due to the lack of mammalian model organisms. The SCNN1D gene coding for δ-ENaC was previously believed to be absent in rodents, hindering studies using standard laboratory animals. We analysed all currently available rodent genomes and discovered that SCNN1D is present in rodents but was independently lost in five rodent lineages, including the Muridae (mice and rats). The independent loss of SCNN1D in rodent lineages may be constrained by phylogeny and taxon-specific adaptation to dry habitats, however habitat aridity does not provide a selection pressure for maintenance of SCNN1D across Rodentia. A fusion of two exons coding for a structurally flexible region in the extracellular domain of δ-ENaC appeared in the Hystricognathi (a group that includes guinea pigs). This conserved pattern evolved at least 41 Ma ago and represents a new autapomorphic feature for this clade. Exon fusion does not impair functionality of guinea pig (Cavia porcellus) δβγ-ENaC expressed in Xenopus oocytes. Electrophysiological characterisation at the whole-cell and single-channel level revealed conserved biophysical features and mechanisms controlling guinea pig αβγ- and δβγ-ENaC function as compared to human orthologues. Guinea pigs therefore represent commercially available mammalian model animals that will help shed light on the physiological function of δ-ENaC
Southern Ocean humpback whale trophic ecology. I : Combining multiple stable isotope methods elucidates diet, trophic position and foraging areas
No full textSouthern Ocean humpback whales Megaptera novaeangliae are capital breeders, breeding in the warm tropics/subtropics in the winter and migrating to nutrient-rich Antarctic feeding grounds in the summer. The classic feeding model is for the species to fast while migrating and breeding, surviving on blubber energy stores. Whilst northern hemisphere humpback whales are generalists, southern hemisphere counterparts are perceived as krill specialists, but for many populations, uncertainties remain regarding their diet and preferred feeding locations. This study used bulk and compound-specific stable isotope analyses and isoscape-based feeding location assignments to assess the diet, trophic ecology and likely feeding areas of humpback whales sampled in the Ross Sea region and around the Balleny Islands. Sampled whales had a mixed diet of plankton, krill and fish, similar to the diet of northern hemisphere humpback whales. Proportions of fish consumed varied but were often high (2–60%), thus challenging the widely held paradigm of Southern Ocean humpback whales being exclusive krill feeders. These whales had lower δ15N values and trophic position estimates than their northern hemisphere counterparts, likely due to lower Southern Ocean baseline δ15N surface water values and a lower percentage consumption of fish, respectively. Most whales fed in the Ross Sea shelf/slope and Balleny Islands high-productivity regions, but some isotopically distinct whales (mostly males) fed at higher trophic levels either around the Balleny Islands and frontal upwelling areas to the north, or en route to Antarctica in temperate waters off southern Australia and New Zealand. These results support other observations of humpback whales feeding during migration, highlighting the species’ dietary plasticity, which may increase their foraging and breeding success and provide them with greater resilience to anthropogenically mediated ecological change. This study highlights the importance of combining in situ field data with regional-scale isoscapes to reliably assess trophic structure and animal feeding locations, and to better inform ecosystem conservation and management of marine protected areas.peerReviewe
The 'true use of reading' : Sarah Fielding and mid eighteenth-century literary strategies.
No full textPhDThe aim of this thesis is to explore, by examining her life and
works, how Sarah Fielding (1710-68) established her identity as an author.
The definition of her role involves her notions of the functions of
writing and reading.
Sarah Fielding attempts to invite readers to form a sense of ties
by tacit understanding of her messages. As she believes that a work
of literature is produced through collaboration between the writer and
the reader, it is an important task in her view to show her attentiveness
toward reading practice. In her consideration of reading, she has two
distinct, even opposite views of her audience: on the one hand a familiar
and limited circle of readers with shared moral and cultural values and
on the other potential readers among the unknown mass of people. The
dual targets direct her to devise various strategies. She tries to
appeal to those who can endorse and appreciate her moral values as well
as her learning. Her writings and letters testify that she is sensitive
to the demands of the literary market, trying to lead the taste of readers
by inventing new forms.
The thesis opens with an overview of Sarah Fielding's career,
followed by a consideration of her critical attention to the roles of
reading. I go on to examine the narrative structures and strategies
she deploys, with a particular emphasis on her use of the epistolary
method. The following chapter deals with her attention to the reading
of the moral message tangibly embodied in her educational writing. It
is followed by an analysis of the activity which earned her a reputation
as a learned woman. Various as the forms of her works are, they invariably
reflect her attempt to balance herself between the two demands of
inventiveness and familiarity
Canon Barnett and the first thirty years of Toynbee Hall
No full textPhDThis thesis is a study of the changing role which Toynbee
Hall, the first university settlement, played in East London between
1884 and 1914. The first chapter presents a brief biography of
Sainiel Augustus Barnett, the founder and first warden of the
settlement, and analyzes his social thought in relation to the
beliefs which were current in Britain during the period. The
second chapter discusses the founding of the settlement, its organization, structure and the aims which underlay its early work. The
third chapter, concentrating on three residents, C.R. Ashbee, .H.
Beveridge and T. Edmund Harvey, shows the way in which subsequent
settlement workers reformulated these aims In accordance with their
own social and economic views. The subsequent chapters discuss the
accomplishments of the settlement in various fields. The fourth
shows that Toynbee Hall's educational program, which was largely an
attempt to work out Matthew Arnold's theory of culture, left little
impact on the life of East London. The fifth chapter discusses the
settlement residents' ineffectual attempts to establish contact with
working men's organizations. The final chapter seeks to demonstrate
that In the field of philanthropy the residents were far more successful than in any other sphere in adapting the settlement to changing
social thought
Novel tri‐isotope ellipsoid approach reveals dietary variation in sympatric predators
No full textSympatric species may partition resources to reduce competition and facilitate co‐existence. While spatial variation and specialization in feeding strategies may be prevalent among large marine predators, studies have focussed on sharks, birds, and marine mammals. We consider for the first time the isotopic niche partitioning of co‐occurring, teleost reef predators spanning multiple families. Using a novel tri‐isotope ellipsoid approach, we investigate the feeding strategies of seven of these species across an atoll seascape in the Maldives. We demonstrate substantial spatial variation in resource use of all predator populations. Furthermore, within each area, there was evidence of intraspecific variation in feeding behaviors that could not wholly be attributed to individual body size. Assessing species at the population level will mask these intraspecific differences in resource use. Knowledge of resource use is important for predicting how species will respond to environmental change and spatial variation should be considered when investigating trophic diversity
Quantifying spatio-temporal consistency in the trophic ecology of two sympatric flatfishes
No full textSympatric flatfish predators may partition their resources in coastal environments to reduce competition and maximise foraging efficiency. However, the degree of spatial and temporal consistency in their trophic ecology is not well understood because dietary studies tend to overlook the heterogeneity of consumed prey. Increasing the spatial and temporal scale of dietary analyses can thus help to resolve predator resource use. We applied a stomach content and multi-tissue (liver and muscle) stable isotope (δ13C, δ15N and δ34S) approach to investigate the feeding habits of two co-occurring flatfish predators, common dab (Limanda limanda) and European plaice (Pleuronectes platessa), across four bays on the Northumberland coast (UK) over short (hours), medium (days) and long (months) temporal scales. Stomach content analyses showed spatial consistencies in predator resource use, whereas stable isotope mixing models revealed considerable inter-bay diet variability. Stomach contents also indicated high dietary overlap between L. limanda and P. platessa, while the stable isotope data yielded low to moderate levels of overlap, with cases of complete niche separation. Furthermore, individual specialisation metrics indicated consistently low levels of specialisation among conspecifics over time. We document changes in resource partitioning in space and time, reflecting diet switching in response to local and temporal fluctuations of patchily distributed prey. This study highlights how trophic tracers integrated at multiple temporal and spatial scales (within tens of kilometres) provide a more integrative approach for assessing the trophic ecology of sympatric predators in dynamic environments
