Optimum growth temperature declines with body size within fish species

According to the temperature-size rule, warming of aquatic ecosystems is generally predicted to increase individual growth rates but reduce asymptotic body sizes of ectotherms. However, we lack a comprehensive understanding of how growth and key processes affecting it, such as consumption and metabolism, depend on both temperature and body mass within species. This limits our ability to inform growth models, link experimental data to observed growth patterns, and advance mechanistic food web models. To examine the combined effects of body size and temperature on individual growth, as well as the link between maximum consumption, metabolism, and body growth, we conducted a systematic review and compiled experimental data on fishes from 52 studies that combined body mass and temperature treatments. By fitting hierarchical models accounting for variation between species, we estimated how maximum consumption and metabolic rate scale jointly with temperature and body mass within species. We found that whole-organism maximum consumption increases more slowly with body mass than metabolism, and is unimodal over the full temperature range, which leads to the prediction that optimum growth temperatures decline with body size. Using an independent dataset, we confirmed this negative relationship between optimum growth temperature and body size. Small individuals of a given population may, therefore, exhibit increased growth with initial warming, whereas larger conspecifics could be the first to experience negative impacts of warming on growth. These findings help advance mechanistic models of individual growth and food web dynamics and improve our understanding of how climate warming affects the growth and size structure of aquatic ectotherms

Effects of Warming on Intraguild Predator Communities with Ontogenetic Diet Shifts

Species interactions mediate how warming affects community composition via individual growth and population size structure. While predictions on how warming affects composition of size- or stage-structured communities have so far focused on linear (food chain) communities, mixed competition-predation interactions, such as intraguild predation, are common. Intraguild predation often results from changes in diet over ontogeny ("ontogenetic diet shifts") and strongly affects community composition and dynamics. Here, we study how warming affects a community of intraguild predators with ontogenetic diet shifts, consumers, and shared prey by analyzing a stage-structured bioenergetics multispecies model with temperature- and body size-dependent individual-level rates. We find that warming can strengthen competition and decrease predation, leading to a loss of a cultivation mechanism (the feedback between predation on and competition with consumers exerted by predators) and ultimately predator collapse. Furthermore, we show that the effect of warming on community composition depends on the extent of the ontogenetic diet shift and that warming can cause a sequence of community reconfigurations in species with partial diet shifts. Our findings contrast previous predictions concerning individual growth of predators and the mechanisms behind predator loss in warmer environments and highlight how feedbacks between temperature and intraspecific size structure are important for understanding such effects on community composition

Temperature impacts on fish physiology and resource abundance lead to faster growth but smaller fish sizes and yields under warming

Resolving the combined effect of climate warming and exploitation in a food web context is key for predicting future biomass production, size-structure and potential yields of marine fishes. Previous studies based on mechanistic size-based food web models have found that bottom-up processes are important drivers of size-structure and fisheries yield in changing climates. However, we know less about the joint effects of 'bottom-up' and physiological effects of temperature; how do temperature effects propagate from individual-level physiology through food webs and alter the size-structure of exploited species in a community? Here, we assess how a species-resolved size-based food web is affected by warming through both these pathways and by exploitation. We parameterize a dynamic size spectrum food web model inspired by the offshore Baltic Sea food web, and investigate how individual growth rates, size-structure, and relative abundances of species and yields are affected by warming. The magnitude of warming is based on projections by the regional coupled model system RCA4-NEMO and the RCP 8.5 emission scenario, and we evaluate different scenarios of temperature dependence on fish physiology and resource productivity. When accounting for temperature-effects on physiology in addition to on basal productivity, projected size-at-age in 2050 increases on average for all fish species, mainly for young fish, compared to scenarios without warming. In contrast, size-at-age decreases when temperature affects resource dynamics only, and the decline is largest for young fish. Faster growth rates due to warming, however, do not always translate to larger yields, as lower resource carrying capacities with increasing temperature tend to result in decline in the abundance of larger fish and hence spawning stock biomass. These results suggest that to understand how global warming affects the size structure of fish communities, both direct metabolic effects and indirect effects of temperature via basal resources must be accounted for

Size-based ecological interactions drive food web responses to climate warming

Predicting climate change impacts on animal communities requires knowledge of how physiological effects are mediated by ecological interactions. Food-dependent growth and within-species size variation depend on temperature and affect community dynamics through feedbacks between individual performance and population size structure. Still, we know little about how warming affects these feedbacks. Using a dynamic stage-structured biomass model with food-, size- and temperature-dependent life history processes, we analyse how temperature affects coexistence, stability and size structure in a tri-trophic food chain, and find that warming effects on community stability depend on ecological interactions. Predator biomass densities generally decline with warming – gradually or through collapses – depending on which consumer life stage predators feed on. Collapses occur when warming induces alternative stable states via Allee effects. This suggests that predator persistence in warmer climates may be lower than previously acknowledged and that effects of warming on food web stability largely depend on species interactions

Temperature- and body size scaling

Climate warming impacts organisms directly through changes in their physiology. Empirical evidence suggest warming has already led to changes in growth, body size, population and community size-structure of natural populations. However, it is difficult to understand the underlying mechanisms from observational data alone. Therefore, it is important to develop mechanistic population- and food web models grounded in a physiological description of individual life history. This requires knowledge on how physiological processes scale with body size and temperature within species and how those are mediated by ecological interactions, which hitherto is largely unexplored. In this thesis, I collated data sets through standardized literature searches to understand how body growth, metabolism and consumption rate scale with body mass within species of fish using hierarchical modelling approaches. I also expanded population and food web models to include temperature dependence of physiological rates. I characterize the intraspecific scaling of abovementioned rates and find that the optimum growth temperature of an individual fish declines as it grows in body mass. Using dynamical models, I show that even simple stage-structure within species together with food dependent ontogenetic development can lead to very different responses to warming compared to similar, but unstructured, population and community models. These include sudden shifts in stage-structure, collapses of top predators and bistability. Analysis of a size-structured model reveals that initial warming can lead to faster growth rates, but this does not lead to larger-sized populations if also basal resources decline with warming. These findings contribute to a broader understanding of the role of intraspecific sizevariation for understanding how climate change impacts population and community structure and dynamics. They also highlight the importance of evaluating physiological responses to warming in an ecological context, as optimum temperatures for growth decline with both body size and reduced food availability

Larger but younger fish when growth outpaces mortality in heated ecosystem

Ectotherms are predicted to ‘shrink’ with global warming, in line with general growth models and the temperature-size rule (TSR), both predicting smaller adult sizes with warming. However, they also predict faster juvenile growth rates and thus larger size-at-age of young organisms. Hence, the result of warming on the size-structure of a population depends on the interplay between how mortality rate, juvenile- and adult growth rates are affected by warming. Here, we use two-decade long time series of biological samples from a unique enclosed bay heated by cooling water from a nearby nuclear power plant to become 5–10 °C warmer than its reference area. We used growth-increment biochronologies (12,658 reconstructed length-at-age estimates from 2426 individuals) to quantify how >20 years of warming has affected body growth, size-at-age, and catch to quantify mortality rates and population size- and age structure of Eurasian perch (Perca fluviatilis). In the heated area, growth rates were faster for all sizes, and hence size-at-age was larger for all ages, compared to the reference area. While mortality rates were also higher (lowering mean age by 0.4 years), the faster growth rates lead to a 2 cm larger mean size in the heated area. Differences in the size-spectrum exponent (describing how the abundance declines with size) were less clear statistically. Our analyses reveal that mortality, in addition to plastic growth and size-responses, is a key factor determining the size structure of populations exposed to warming. Understanding the mechanisms by which warming affects the size- and the age structure of populations is critical for predicting the impacts of climate change on ecological functions, interactions, and dynamics

Beaconlogin - an Efficient Way to Register Presence on Construction Sites

As of January the first, 2016, all companies working in the Swedish construction industry must follow a new law. The law makes it mandatory for anyone carrying out construction activities to have electronic staff registers on their sites. Failing to present a correct registration of all personnel present at the construction site will result in a fine ranging from 15,000 SEK to 25,000 SEK. Our solution for a simple way of registration builds on Bluetooth technology combined with a smartphone application. Together with Bluetooth devices, the registration can be done automatically which eliminates the need for construction workers to actively search for the e-staff register.Den första januari 2016 infördes en ny lag för företag inom den Svenska byggarbetsbranchen som gör det obligatoriskt för alla som utför byggverksamhet att ha elektroniska personalliggare på sina byggarbetsplatser. Om man inte kan visa upp en korrekt närvaroregistrering av den personal som befinner sig på byggarbetsplatsen riskerar man som företag böter på mellan 15 000 SEK till 25 000 SEK. Vår lösning för att sköta närvaroregistrering bygger på bluetoothteknologi i kombination med en mobilapplikation. Med hjälp av bluetoothenheter kan registreringen ske automatiskt vilket tar bort behovet för arbetare att aktivt själva behöva sköta sin registrering

Larger but younger fish when growth outpaces mortality in heated ecosystem

Ectotherms are predicted to ‘shrink’ with global warming, in line with general growth models and the temperature-size rule (TSR), both predicting smaller adult sizes with warming. However, they also predict faster juvenile growth rates and thus larger size-at-age of young organisms. Hence, the result of warming on the size-structure of a population depends on the interplay between how mortality rate, juvenile- and adult growth rates are affected by warming. Here, we use two-decade long time series of biological samples from a unique enclosed bay heated by cooling water from a nearby nuclear power plant to become 5–10 °C warmer than its reference area. We used growth-increment biochronologies (12,658 reconstructed length-at-age estimates from 2426 individuals) to quantify how >20 years of warming has affected body growth, size-at-age, and catch to quantify mortality rates and population size- and age structure of Eurasian perch (Perca fluviatilis). In the heated area, growth rates were faster for all sizes, and hence size-at-age was larger for all ages, compared to the reference area. While mortality rates were also higher (lowering mean age by 0.4 years), the faster growth rates lead to a 2 cm larger mean size in the heated area. Differences in the size-spectrum exponent (describing how the abundance declines with size) were less clear statistically. Our analyses reveal that mortality, in addition to plastic growth and size-responses, is a key factor determining the size structure of populations exposed to warming. Understanding the mechanisms by which warming affects the size- and the age structure of populations is critical for predicting the impacts of climate change on ecological functions, interactions, and dynamics

Beaconlogin - an Efficient Way to Register Presence on Construction Sites

As of January the first, 2016, all companies working in the Swedish construction industry must follow a new law. The law makes it mandatory for anyone carrying out construction activities to have electronic staff registers on their sites. Failing to present a correct registration of all personnel present at the construction site will result in a fine ranging from 15,000 SEK to 25,000 SEK. Our solution for a simple way of registration builds on Bluetooth technology combined with a smartphone application. Together with Bluetooth devices, the registration can be done automatically which eliminates the need for construction workers to actively search for the e-staff register.Den första januari 2016 infördes en ny lag för företag inom den Svenska byggarbetsbranchen som gör det obligatoriskt för alla som utför byggverksamhet att ha elektroniska personalliggare på sina byggarbetsplatser. Om man inte kan visa upp en korrekt närvaroregistrering av den personal som befinner sig på byggarbetsplatsen riskerar man som företag böter på mellan 15 000 SEK till 25 000 SEK. Vår lösning för att sköta närvaroregistrering bygger på bluetoothteknologi i kombination med en mobilapplikation. Med hjälp av bluetoothenheter kan registreringen ske automatiskt vilket tar bort behovet för arbetare att aktivt själva behöva sköta sin registrering