Carolyn Barnes

Bio: Carolyn Barnes is an academic researcher from Centre for Environment, Fisheries and Aquaculture Science. The author has contributed to research in topics: Food chain & Trophic level. The author has an hindex of 9, co-authored 9 publications receiving 723 citations. Previous affiliations of Carolyn Barnes include Newcastle University.

Global patterns in predator–prey size relationships reveal size dependency of trophic transfer efficiency

Abstract: Predator-prey body size relationships influence food chain length, trophic structure, transfer efficiency, interaction strength, and the bioaccumulation of contaminants. Improved quantification of these relationships and their response to the environment is needed to parameterize food web models and describe food web structure and function. A compiled data set comprising 29582 records of individual prey eaten at 21 locations by individual predators that spanned 10 orders of magnitude in mass and lived in marine environments ranging from the poles to the tropics was used to investigate the influence of predator size and environment on predator and prey size relationships. Linear mixed effects models demonstrated that predator-prey mass ratios (PPMR) increased with predator mass. The amount of the increase varied among locations and predator species and individuals but was not significantly influenced by temperature, latitude, depth, or primary production. Increases in PPMR with predator mass implied nonlinear relationships between log body mass and trophic level and reductions in transfer efficiency with increasing body size. The results suggest that very general rules determine dominant trends in PPMR in diverse marine ecosystems, leading to the ubiquity of size-based trophic structuring and the consistency of observed relationships between the relative abundance of individuals and their body size.

Effect of temperature and ration size on carbon and nitrogen stable isotope trophic fractionation

Abstract: Summary 1Stable isotope data are widely used to track the origins and transformations of materials in food webs. Reliable interpretation of these data requires knowledge of the factors influencing isotopic fractionation between diet and consumer. For practical reasons, isotopic fractionation is often assumed to be constant but, in reality, a range of factors may affect fractionation. 2To investigate effects of temperature and feeding rate on fractionation of carbon and nitrogen stable isotopes in a marine predator, we reared European sea bass Dicentrarchus labrax on identical diets at 11 and 16 °C on three ration levels for 600 days. 3Nitrogen trophic fractionation (Δδ15N) was affected by temperature. Bass Δδ15N was 4·41‰ at 11 °C and 3·78‰ at 16 °C. 4Carbon fractionation (Δδ13C) was also affected by temperature. Bass Δδ13C was 1·18‰ at 11 °C and 1·64‰ at 16 °C. The higher lipid content in the tissues of bass reared at cooler temperatures accounted for the temperature effect on Δδ13C. When Δδ13C was determined using mathematically defatted values, there was a direct effect of ration size and Δδ13C was 2·51, 2·39 and 2·31‰ for high, medium and low rations, respectively. 5Reported Δδ15N for all treatments exceeded the mean of 3·4‰ widely used in ecological studies of fish populations and communities. This would confound the interpretation of δ15N as an indicator of trophic level when comparing populations that are exposed to different temperatures. 6The Δδ13C of 0–1‰ commonly applied in food web studies did not hold under any of the temperature or feeding regimes considered and a value of 2‰ would be more appropriate.

The importance of quantifying inherent variability when interpreting stable isotope field data

Abstract: Stable isotope data are often used to assess diet, trophic level, trophic niche width and the extent of omnivory Notwithstanding ongoing discussions about the value of these approaches, variations in isotopic signatures among individuals depend on inherent variability as well as differences in feeding habitats Remarkably, the relative contributions of diet variation and inherent variability to differences in δ15N and δ13C among individuals have not been quantified for the same species at the same life history stages, and inherent variability has been ignored or assumed We quantified inherent variability in δ13C and δ15N among individuals of a marine fish (the European sea bass, Dicentrarchus labrax) reared in a controlled environment on a diet of constant isotopic composition and compared it with variability in δ13C and δ15N among individuals from wild bass populations The analysis showed that inherent variability among reared individuals on a controlled diet was equivalent to a large proportion of the observed variability among wild individuals and, therefore, that inherent variability should be measured to establish baseline variability in wild populations before any assumptions are made about the influence of diet Given that inherent variability is known to be dependent on species, life history stage and the environment, our results show that it should be quantified on a case-by-case basis if diet studies are intended to provide absolute assessments of dietary habits

Predator and prey body sizes in marine food webs

Abstract: Knowledge of relationships between predator size and prey size are needed to describe interactions of species and size classes in food webs. Most estimates of predator and prey sizes have been based on dietary studies and apply to small numbers of species in a relatively narrow size range. These estimates may or may not be representative of values for other groups of species and body sizes or for other locations. Marine predator and prey size data associated with published literature were identified and collated to produce a single data set. If predator or prey length of mass were not measured in the original study, the length or mass was calculated using length–mass relationships. The data set consists of 34 931 records from 27 locations covering a wide range of environmental conditions from the tropics to the poles and for 93 types of predator with sizes ranging from 0.1 mg to over 415 kg and 174 prey types with sizes from 75 pg to over 4.5 kg. Each record includes: predator and prey scientific names, c...

Predicting marine phytoplankton community size structure from empirical relationships with remotely sensed variables

Abstract: The size composition of primary producers has a potential influence on the length of marine food chains and carbon sinking rates, thus on the proportion of primary production (PP) that is removed from the upper layers and available to higher trophic levels. While total rates of PP are widely reported, it is also necessary to account for the size composition of primary producers when developing food web models that predict consumer biomass and production. Empirical measurement of size composition over large space and time scales is not feasible, so one approach is to predict size composition from environmental variables that are measured and reported on relevant scales. Here, we describe relationships between the environment and the size composition of phytoplankton communities, using a collation of empirical measurements of size composition from sites that include polar, tropical and upwelling environments. The size composition of the phytoplankton communities can be predicted using two remotely sensed variables, chlorophyll-a concentration and sea surface temperature. Applying such relationships in combination allows prediction of the slope and location of phytoplankton size spectra and estimation of the percentage of different sized phytoplankton groups in communities.

The Theory of Island Biogeography

Abstract: Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

Influence of Diet On the Distribtion of Nitrogen Isotopes in Animals

Abstract: The influence of diet on the distribution of nitrogen isotopes in animals was investigated by analyzing animals grown in the laboratory on diets of constant nitrogen isotopic composition. The isotopic composition of the nitrogen in an animal reflects the nitrogen isotopic composition of its diet. The δ^(15)N values of the whole bodies of animals are usually more positive than those of their diets. Different individuals of a species raised on the same diet can have significantly different δ^(15)N values. The variability of the relationship between the δ^(15)N values of animals and their diets is greater for different species raised on the same diet than for the same species raised on different diets. Different tissues of mice are also enriched in ^(15)N relative to the diet, with the difference between the δ^(15)N values of a tissue and the diet depending on both the kind of tissue and the diet involved. The δ^(15)N values of collagen and chitin, biochemical components that are often preserved in fossil animal remains, are also related to the δ^(15)N value of the diet. The dependence of the δ^(15)N values of whole animals and their tissues and biochemical components on the δ^(15)N value of diet indicates that the isotopic composition of animal nitrogen can be used to obtain information about an animal's diet if its potential food sources had different δ^(15)N values. The nitrogen isotopic method of dietary analysis probably can be used to estimate the relative use of legumes vs non-legumes or of aquatic vs terrestrial organisms as food sources for extant and fossil animals. However, the method probably will not be applicable in those modern ecosystems in which the use of chemical fertilizers has influenced the distribution of nitrogen isotopes in food sources. The isotopic method of dietary analysis was used to reconstruct changes in the diet of the human population that occupied the Tehuacan Valley of Mexico over a 7000 yr span. Variations in the δ^(15)C and δ^(15)N values of bone collagen suggest that C_4 and/or CAM plants (presumably mostly corn) and legumes (presumably mostly beans) were introduced into the diet much earlier than suggested by conventional archaeological analysis.

Ecological networks--beyond food webs.

Abstract: Summary 1. A fundamental goal of ecological network research is to understand how the complexity observed in nature can persist and how this affects ecosystem functioning. This is essential for us to be able to predict, and eventually mitigate, the consequences of increasing environmental perturbations such as habitat loss, climate change, and invasions of exotic species. 2. Ecological networks can be subdivided into three broad types: ‘traditional’ food webs, mutualistic networks and host‐parasitoid networks. There is a recent trend towards cross-comparisons among network types and also to take a more mechanistic, as opposed to phenomenological, perspective. For example, analysis of network configurations, such as compartments, allows us to explore the role of co-evolution in structuring mutualistic networks and host‐parasitoid networks, and of body size in food webs. 3. Research into ecological networks has recently undergone a renaissance, leading to the production of a new catalogue of evermore complete, taxonomically resolved, and quantitative data. Novel topological patterns have been unearthed and it is increasingly evident that it is the distribution of interaction strengths and the configuration of complexity, rather than just its magnitude, that governs network stability and structure. 4. Another significant advance is the growing recognition of the importance of individual traits and behaviour: interactions, after all, occur between individuals. The new generation of high-quality networks is now enabling us to move away from describing networks based on species-averaged data and to start exploring patterns based on individuals. Such refinements will enable us to address more general ecological questions relating to foraging theory and the recent metabolic theory of ecology. 5. We conclude by suggesting a number of ‘dead ends’ and ‘fruitful avenues’ for future research into ecological networks.

On the Use of Stable Isotopes in Trophic Ecology

Abstract: Stable isotope analysis (SIA) has proven to be a useful tool in reconstructing diets, characterizing trophic relationships, elucidating patterns of resource allocation, and constructing food webs. Consequently, the number of studies using SIA in trophic ecology has increased exponentially over the past decade. Several subdisciplines have developed, including isotope mixing models, incorporation dynamics models, lipid-extraction and correction methods, isotopic routing models, and compound-specific isotopic analysis. As with all tools, there are limitations to SIA. Chief among these are multiple sources of variation in isotopic signatures, unequal taxonomic and ecosystem coverage, over-reliance on literature values for key parameters, lack of canonical models, untested or unrealistic assumptions, low predictive power, and a paucity of experimental studies. We anticipate progress in SIA resulting from standardization of methods and models, calibration of model parameters through experimentation, and continu...

Shrinking of fishes exacerbates impacts of global ocean changes on marine ecosystems

Abstract: In the ocean, biological responses to climate change include altered distribution, phenology and productivity. A modelling study into the integrated effects of these various changes on fish body size suggests that averaged maximum body weight could fall by 14–24% globally by 2050. About half of the decline is accounted for by changes in distribution and abundance, with the remainder being physiological.