Using Carbon, Nitrogen, Sulfur, and Mercury Isotopes to Trace Elasmobranch Foraging Habitats in Contrasting Biogeochemical Environments.

Stable isotopes are well established as routine and reliable tracers of nutrient flux and trophic structure. However, inferring trophic ecology from isotopic data is challenging due to variability at the food web base and systematic differences in biochemical fractionation during metabolism. Analyses of isotope systems from multiple elements with contrasting fractionation drivers may resolve some sources of variance, strengthening connections between measured isotopic variations and inferred ecological processes.

Detecting environmentally dependent developmental plasticity in fossilized individuals.

The fossil record provides the most powerful evidence of large-scale biodiversity change on Earth, but it does so at coarse and often idiosyncratic temporal scales. One critical problem that arises concerns the evolutionary consequences of individual environmental experience. Individuals respond to their environment instantaneously, whereas the resolution of most fossil records aggregates multiple paleoenvironments over time scales beyond individual lifespans.

Potential metabolic records in isotope signals of chondrichthyan hard tissues.

Recent advances have demonstrated that the field metabolic rates (FMRs) of teleost fishes can be quantified from stable isotope compositions of carbonate-biomineralized otoliths. Bones and teeth, in addition to bioapatite, contain carbonate and should retain a similar isotopic expression of metabolic rate. Chondrichthyan skeletons are cartilaginous, but in most species some degree of bio-apatite mineralisation of cartilage has been determined.

Variable habitat use supports fine-scale population differentiation of a freshwater piscivore (northern pike, Esox lucius) along salinity gradients in brackish lagoons.

In mobile animals, selection pressures resulting from spatio-temporally varying ecological factors often drive adaptations in migration behavior and associated physiological phenotypes. These adaptations may manifest in ecologically and genetically distinct ecotypes within populations. We studied a meta-population of northern pike (Esox lucius) in brackish environments and examined intrapopulation divergence along environmental gradients.

Tracing the geographic origin of Atlantic cod products using stable isotope analysis.

Rationale: Increasing demand for fish and seafood means that the traceability of marine products is becoming ever more important for consumers, producers and regulators. Highly complex and globalised supply networks create challenges for verifying a stated catch region. Atlantic cod is one of the most commercially important species in the northeast Atlantic.

Incorporating otolith-isotope inferred field metabolic rate into conservation strategies.

Fluctuating ocean conditions are rearranging whole networks of marine communities-from individual-level physiological thresholds to ecosystem function. Physiological studies support predictions from individual-level responses (biochemical, cellular, tissue, respiratory potential) based on laboratory experiments. The otolith-isotope method of recovering field metabolic rate has recently filled a gap for the bony fishes, linking otolith stable isotope composition to oxygen consumption and experienced temperature estimates.

Mercury bioaccumulation and its relationship with trophic biomarkers in a Mediterranean elasmobranch mesopredator.

Human activity has led to increased concentrations of mercury (Hg) in the world's oceans. Mercury can bioaccumulate and biomagnify in animal tissues via trophic transfer, thus, becoming most pronounced in larger and older predators. Here, we measured Hg concentrations and their relationship with stable isotopes-based proxies of trophic level (δC and δN values) in multiple tissues of Mustelus spp.

Thermal sensitivity of field metabolic rate predicts differential futures for bluefin tuna juveniles across the Atlantic Ocean.

Changing environmental temperatures impact the physiological performance of fishes, and consequently their distributions. A mechanistic understanding of the linkages between experienced temperature and the physiological response expressed within complex natural environments is often lacking, hampering efforts to project impacts especially when future conditions exceed previous experience. In this study, we use natural chemical tracers to determine the individual experienced temperatures and expressed field metabolic rates of Atlantic bluefin tuna (Thunnus thynnus) during their first year of life.

Geographical, temporal, and individual-based differences in the trophic ecology of female Cape fur seals.

Information on resource use and trophic dynamics of marine predators is important for understanding their role in ecosystem functioning and predicting population-level responses to environmental change. Where separate populations experience different local environmental conditions, geographic variability in their foraging ecology is often expected. Within populations, individuals also vary in morphology, physiology, and experience, resulting in specialization in resource use.

Deuterium in marine organic biomarkers: toward a new tool for quantifying aquatic mixotrophy.

The traditional separation between primary producers (autotrophs) and consumers (heterotrophs) at the base of the marine food web is being increasingly replaced by the paradigm that mixoplankton, planktonic protists with the nutritional ability to use both phago(hetero)trophy and photo(auto)trophy to access energy are widespread globally. Thus, many 'phytoplankton' eat, while 50% of 'protozooplankton' also perform photosynthesis. Mixotrophy may enhance primary production, biomass transfer to higher trophic levels and the efficiency of the biological pump to sequester atmospheric CO into the deep ocean.

Stable isotopes demonstrate seasonally stable benthic-pelagic coupling as newly fixed nutrients are rapidly transferred through food chains in an estuarine fish community.

Seasonal differences in the availability of resources potentially result in the 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 the food web structure or nutrient flux across multiple trophic levels. We determined the temporal dynamics in stable isotope compositions (carbon, nitrogen and sulphur) of a fish community from a highly seasonal, temperate estuary sampled monthly over a full annual cycle.

Body condition of returning Atlantic salmon Salmo salar L. correlates with scale δC and δN content deposited at the last marine foraging location.

Patterns of feeding and growth of Atlantic salmon Salmo salar L. in the marine environment are critical to understanding how observed declines in recruitment may reflect warming or other oceanic drivers. The isotopic composition of scales can provide insight into differences in marine feeding location and possibly temperature regime.

A modern method of multiple working hypotheses to improve inference in ecology.

Science provides a method to learn about the relationships between observed patterns and the processes that generate them. However, inference can be confounded when an observed pattern cannot be clearly and wholly attributed to a hypothesized process. Over-reliance on traditional single-hypothesis methods (i.

Evaluation of two lipid removal methods for stable carbon and nitrogen isotope analysis in whale tissue.

Rationale: The presence of lipids in animal tissues can influence the interpretation of stable isotope data, particularly in lipid-rich tissues such as the skin and muscle of marine mammals. The traditionally employed chloroform-methanol delipidation protocol has the potential to alter δ N values in proteinaceous tissues. Our objective was to determine whether the use of cyclohexane could be an alternative extraction method, effectively removing lipids without altering δ N values.

Sympatric Atlantic puffins and razorbills show contrasting responses to adverse marine conditions during winter foraging within the North Sea.

Background: Natural environments are dynamic systems with conditions varying across years. Higher trophic level consumers may respond to changes in the distribution and quality of available prey by moving to locate new resources or by switching diets. In order to persist, sympatric species with similar ecological niches may show contrasting foraging responses to changes in environmental conditions.

Combining simulation modeling and stable isotope analyses to reconstruct the last known movements of one of Nature's giants.

The spatial ecology of rare, migratory oceanic animals is difficult to study directly. Where incremental tissues are available, their chemical composition can provide valuable indirect observations of movement and diet. Interpreting the chemical record in incremental tissues can be highly uncertain, however, as multiple mechanisms interact to produce the observed data.

Patterns of at-sea behaviour at a hybrid zone between two threatened seabirds.

Patterns of behavioural variation and migratory connectivity are important characteristics of populations, particularly at the edges of species distributions, where processes involved in influencing evolutionary trajectories, such as divergence, mutual persistence, and natural hybridization, can occur. Here, we focused on two closely related seabird species that breed in the Mediterranean: Balearic shearwaters (Puffinus mauretanicus) and Yelkouan shearwaters (Puffinus yelkouan). Genetic and phenotypic evidence of hybridization between the two species on Menorca (the eastern and westernmost island in the breeding ranges of the two shearwaters, respectively) has provided important insights into relationships between these recently diverged species.

Deep-water fisheries along the British Isles continental slopes: status, ecosystem effects and future perspectives.

In this paper, we revisit the state of deep-water fisheries to the west of the British Isles and aim to provide an overview on the key drivers behind community changes along continental margins. The deep-water fisheries to the west of the British Isles that extend from the shelf-slope break down to the lower slope and along banks and seamounts of the Rockall Basin, mainly target blue ling Molva dypterygia, roundnose grenadier Coryphaenoides rupestris, orange roughy Hoplostethus atlanticus, with by-catches of black scabbardfish Aphanopus carbo and tusk Brosme brosme. These fishing grounds experienced a long period of exhaustive exploitation until the early 2000s, but subsequently the implementation of management strategies has helped to relieve excessive fishing pressure.

Field metabolic rates of teleost fishes are recorded in otolith carbonate.

Field metabolic rate (FMR) is key to understanding individual and population-level responses to environmental changes, but is challenging to measure in field conditions, particularly in aquatic environments. Here we show that FMR can be estimated directly from the isotopic composition of carbon in fish otoliths (δC). We describe the relationship between δC values and oxygen consumption rate, and report results from laboratory experiments relating individual-level measurements of oxygen consumption rates to δC values in Atlantic cod ().

Taylor's power law captures the effects of environmental variability on community structure: An example from fishes in the North Sea.

Taylor's power law (TPL) describes the relationship between the mean and variance in abundance of populations, with the power law exponent considered a measure of aggregation. However, the usefulness of TPL exponents as an ecological metric has been questioned, largely due to its apparent ubiquity in various complex systems. The aim of this study was to test whether TPL exponents vary systematically with potential drivers of animal aggregation in time and space and therefore capture useful ecological information of the system of interest.

Teleost and elasmobranch eye lenses as a target for life-history stable isotope analyses.

Incrementally grown, metabolically inert tissues such as fish otoliths provide biochemical records that can used to infer behavior and physiology throughout the lifetime of the individual. Organic tissues are particularly useful as the stable isotope composition of the organic component can provide information about diet, trophic level and location. Unfortunately, inert, incrementally grown organic tissues are relatively uncommon.

A global perspective on the trophic geography of sharks.

Sharks are a diverse group of mobile predators that forage across varied spatial scales and have the potential to influence food web dynamics. The ecological consequences of recent declines in shark biomass may extend across broader geographic ranges if shark taxa display common behavioural traits. By tracking the original site of photosynthetic fixation of carbon atoms that were ultimately assimilated into muscle tissues of 5,394 sharks from 114 species, we identify globally consistent biogeographic traits in trophic interactions between sharks found in different habitats.

Functional, size and taxonomic diversity of fish along a depth gradient in the deep sea.

Biodiversity is well studied in ecology and the concept has been developed to include traits of species, rather than solely taxonomy, to better reflect the functional diversity of a system. The deep sea provides a natural environmental gradient within which to study changes in different diversity metrics, but traits of deep-sea fish are not widely known, hampering the application of functional diversity to this globally important system. We used morphological traits to determine the functional richness and functional divergence of demersal fish assemblages along the continental slope in the Northeast Atlantic, at depths of 300-2,000 m.

DNA barcoding identifies a cosmopolitan diet in the ocean sunfish.

The ocean sunfish (Mola mola) is the world's heaviest bony fish reaching a body mass of up to 2.3 tonnes. However, the prey M.

Ecogeochemistry potential in deep time biodiversity illustrated using a modern deep-water case study.

The fossil record provides the only direct evidence of temporal trends in biodiversity over evolutionary timescales. Studies of biodiversity using the fossil record are, however, largely limited to discussions of taxonomic and/or morphological diversity. Behavioural and physiological traits that are likely to be under strong selection are largely obscured from the body fossil record.