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Understanding the consequences of species loss in complex ecological communities is one of the great challenges in current biodiversity research. For a long time, this topic has been addressed by traditional biodiversity experiments. Most of these approaches treat species as trait-free, taxonomic units characterizing communities only by species number without accounting for species traits. However, extinctions do not occur at random as there is a clear correlation between extinction risk and species traits. In this review, we assume that large species will be most threatened by extinction and use novel allometric and size-spectrum concepts that include body mass as a primary species trait at the levels of populations and individuals, respectively, to re-assess three classic debates on the relationships between biodiversity and (i) food-web structural complexity, (ii) community dynamic stability, and (iii) ecosystem functioning. Contrasting current expectations, size-structured approaches suggest that the loss of large species, that typically exploit most resource species, may lead to future food webs that are less interwoven and more structured by chains of interactions and compartments. The disruption of natural body-mass distributions maintaining food-web stability may trigger avalanches of secondary extinctions and strong trophic cascades with expected knock-on effects on the functionality of the ecosystems. Therefore, we argue that it is crucial to take into account body size as a species trait when analysing the consequences of biodiversity loss for natural ecosystems. Applying size-structured approaches provides an integrative ecological concept that enables a better understanding of each species' unique role across communities and the causes and consequences of biodiversity loss.

Introduction Trophic interactions are one of the most important aspects shaping ecological communities, and the food-web paradigm has played a major role in the development of ecology as a science. Early food-web models attempted to simulate the flow of energy and biomass within local communities (Odum, 1956) or describe the structure of feeding relationships (Pimm, 1982). Species or “trophospecies” (i.e., groups of species that supposedly share the same sets of predators and prey; see Yodzis and Winemiller, 1999) have served as the building blocks of both types of trophic networks (usually referred to as flow webs and topological webs, respectively). Topological food webs are static “snapshots” lacking magnitudes (i.e., estimates of the rate of energy flow or the strength of trophic links) and therefore have limited utility for examination of ecological dynamics. The strength of trophic interactions can be estimated in different ways (e.g., observing magnitudes of biomass/energy transfers, modeling of consumer feeding preferences, functional responses or metabolic constraints, varying interaction coefficients in Lotka–Volterra multispecies competition models, and quantifying responses from manipulative field experiments; see Berlow et al., 2004, 2009). Food-web models have been used to predict risks of secondary extinction (Allesina and Bodini, 2004), examine consequences of biodiversity loss for ecosystem stability (McCann, 2000), and study direct and indirect effects of predators on prey populations (Bondavalli and Ulanowicz, 1999). Food-web models that lump individuals into species and trophospecies lose much valuable information concerning influential attributes associated with age, body size, foraging history, location, and reproductive tactics. Such lumping may inflate the number of trophic interactions associated with species or trophospecies and thus fails to take into account how variation in feeding preferences between individuals affects food-web structure and dynamics (Bolnick et al., 2007). Trait-based approaches have gained momentum in community and evolutionary ecology, and most ecologists now recognize the relevance of variation at intraspecific as well as interspecific levels (Bolnick et al., 2011). This recognition calls for exploration of new approaches to food-web ecology. Intraspecific trait variation can alter the number and strength of interspecific interactions, especially when food-web interactions are a function of body size (Otto et al., 2007; Berlow et al., 2009).

Brander, K., Neuheimer, A., Andersen, K. H., and Hartvig, M. 2013. Overconfidence in model projections. – ICES Journal of Marine Science, 70: 1065–1068. There is considerable public and political interest in the state of marine ecosystems and fisheries, but the reliability of some recent projections has been called into question. New information about declining fish stocks, loss of biodiversity, climate impacts, and management failure is frequently reported in the major news media, based on publications in prominent scientific journals. Public and political awareness of the generally negative changes taking place in marine ecosystems is welcome, especially if it results in effective remedial action, but the scientific basis for such action must be reliable and uncertainties arising from models and data shortcomings must be presented fully and transparently. Scientific journals play an important role and should require more detailed analysis and presentation of uncertainties.

We employ size-based theoretical arguments to derive simple analytic predictions of ecological patterns and properties of natural communities: size-spectrum exponent, maximum trophic level, and susceptibility to invasive species. The predictions are brought about by assuming that an infinite number of species are continuously distributed on a size–trait axis. It is, however, an open question whether such predictions are valid for a food web with a finite number of species embedded in a network structure. We address this question by comparing the size-based predictions to results from dynamic food web simulations with varying species richness. To this end, we develop a new size- and trait-based food web model that can be simplified into an analytically solvable size-based model. We confirm existing solutions for the size distribution and derive novel predictions for maximum trophic level and invasion resistance. Our results show that the predicted size-spectrum exponent is borne out in the simulated food webs even with few species, albeit with a systematic bias. The predicted maximum trophic level turns out to be an upper limit since simulated food webs may have a lower number of trophic levels, especially for low species richness, due to structural constraints. The size-based model possesses an evolutionary stable state and is therefore un-invadable. In contrast, the food web simulations show that all communities, irrespective of number of species, are equally open to invasions. We use these results to discuss the validity of size-based predictions in the light of the structural constraints imposed by food webs.

Knowledge of feeding rates is the basis to understand interaction strength and subsequently the stability of ecosystems and biodiversity. Feeding rates, as all biological rates, depend on consumer and resource body masses and environmental temperature. Despite five decades of research on functional responses as quantitative models of feeding rates, a unifying framework of how they scale with body masses and temperature is still lacking. This is perplexing, considering that the strength of functional responses (i.e. interaction strengths) is crucially important for the stability of simple consumer–resource systems and the persistence, sustainability and biodiversity of complex communities. Here, we present the largest currently available database on functional response parameters and their scaling with body mass and temperature. Moreover, these data are integrated across ecosystems and metabolic types of species. Surprisingly, we found general temperature dependencies that differed from the Arrhenius terms predicted by metabolic models. Additionally, the body-mass-scaling relationships were more complex than expected and differed across ecosystems and metabolic types. At local scales (taxonomically narrow groups of consumer–resource pairs), we found hump-shaped deviations from the temperature and body-mass-scaling relationships. Despite the complexity of our results, these body-mass- and temperature-scaling models remain useful as a mechanistic basis for predicting the consequences of warming for interaction strengths, population dynamics and network stability across communities differing in their size structure.

Several ecologically and commercially important fish species spend the winter in a state of minimum feeding activity and at lower risk of predation. To enable this overwintering behaviour, energetic reserves are generated prior to winter to support winter metabolism. Maintenance metabolism in fish scales with body size and increases with temperature, and the two factors together determine a critical threshold size for passive overwintering below which the organism is unlikely to survive without feeding. This is because the energetic cost of metabolism exceeds maximum energy reserves. In the present study, we estimated the energetic cost of overwintering from a bioenergetic model. The model was parameterised using respirometry-based measurements of standard metabolic rate in buried A. tobianus (a close relative to A. marinus) at temperatures from 5.3 to 18.3°C and validated with two independent long-term overwintering experiments. Maximum attainable energy reserves were estimated from published data on A. marinus in the North Sea. The critical threshold size in terms of length (L th) for A. marinus in the North Sea was estimated to be 9.5 cm. We then investigated two general predictions: (1) Fish smaller than L th display winter feeding activity, and (2) size at maturation of iteroparous species is larger than L th to ensure sufficient energy reserves to accommodate both the metabolic cost of passive overwintering and reproductive investments. Both predictions were found to be consistent with data on size at maturation and total body energy in December and February.

We synthesise traditional unstructured food webs, allometric body size scaling, trait-based modelling, and physiologically structured modelling to provide a novel and ecologically relevant tool for size-structured food webs. The framework allows food web models to include ontogenetic growth and life-history omnivory at the individual level by resolving the population structure of each species as a size-spectrum. Each species is characterised by the trait 'size at maturation', and all model parameters are made species independent through scaling with individual body size and size at maturation. Parameter values are determined from cross-species analysis of fish communities as life-history omnivory is widespread in aquatic systems, but may be reparameterised for other systems. An ensemble of food webs is generated and the resulting communities are analysed at four levels of organisation: community level, species level, trait level, and individual level. The model may be solved analytically by assuming that the community spectrum follows a power law. The analytical solution provides a baseline expectation of the results of complex food web simulations, and agrees well with the predictions of the full model on 1) biomass distribution as a function of individual size, 2) biomass distribution as a function of size at maturation, and 3) relation between predator-prey mass ratio of preferred and eaten food. The full model additionally predicts the diversity distribution as a function of size at maturation.

Explaining variability in offspring vs. adult size among groups is a necessary step to determine the evolutionary and environmental constraints shaping variability in life history strategies. This is of particular interest for life in the ocean where a diversity of offspring development strategies is observed along with variability in physical and biological forcing factors in space and time. We compiled adult and offspring size for 407 pelagic marine species covering more than 17 orders of magnitude in body mass including Cephalopoda, Cnidaria, Crustaceans, Ctenophora, Elasmobranchii, Mammalia, Sagittoidea, and Teleost. We find marine life following one of two distinct strategies, with offspring size being either proportional to adult size (e.g., Crustaceans, Elasmobranchii, and Mammalia) or invariant with adult size (e.g., Cephalopoda, Cnidaria, Sagittoidea, Teleosts, and possibly Ctenophora). We discuss where these two strategies occur and how these patterns (along with the relative size of the offspring) may be shaped by physical and biological constraints in the organism's environment. This adaptive environment along with the evolutionary history of the different groups shape observed life history strategies and possible group-specific responses to changing environmental conditions (e.g., production and distribution).

The size of an individual organism is a key trait to characterize its physiology and feeding ecology. Size-based scaling laws may have a limited size range of validity or undergo a transition from one scaling exponent to another at some characteristic size. We collate and review data on size-based scaling laws for resource acquisition, mobility, sensory range, and progeny size for all pelagic marine life, from bacteria to whales. Further, we review and develop simple theoretical arguments for observed scaling laws and the characteristic sizes of a change or breakdown of power laws. We divide life in the ocean into seven major realms based on trophic strategy, physiology, and life history strategy. Such a categorization represents a move away from a taxonomically oriented description toward a trait-based description of life in the oceans. Finally, we discuss life forms that transgress the simple size-based rules and identify unanswered questions. Fil: Andersen, K. H.. Centre for Ocean Life; Dinamarca. Technical University of Denmark; Dinamarca Fil: Berger, Tobías Miguel. Centre for Ocean Life; Dinamarca. Universidad de Copenhagen; Dinamarca Fil: Gonçalves, Rodrigo Javier. Centre for Ocean Life; Dinamarca. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Technical University of Denmark; Dinamarca. Fundación Playa Unión. Estación de Fotobiología Playa Unión; Argentina Fil: Hartvig, M.. Technical University of Denmark; Dinamarca. Universidad de Copenhagen; Dinamarca. Universität Göttingen; Alemania Fil: Heuschele, J.. Technical University of Denmark; Dinamarca. Centre for Ocean Life; Dinamarca Fil: Hylander, S.. Technical University of Denmark; Dinamarca. Linnaeus University; Suiza Fil: Jacobsen, N. S.. Centre for Ocean Life; Dinamarca. Technical University of Denmark; Dinamarca Fil: Lindemann, C.. Technical University of Denmark; Dinamarca Fil: Martens, E. A.. Centre for Ocean Life; Dinamarca. Technical University of Denmark; Dinamarca. Universidad de Copenhagen; Dinamarca Fil: Neuheimer, A. B.. Technical University of Denmark; Dinamarca. Universidad de Copenhagen; Dinamarca. University of Hawaii at Manoa; Estados Unidos Fil: Olsson, K.. Technical University of Denmark; Dinamarca. Universidad de Copenhagen; Dinamarca Fil: Palacz, A.. Technical University of Denmark; Dinamarca Fil: Prowe, A. E. F.. Centre for Ocean Life; Dinamarca. Technical University of Denmark; Dinamarca. Geomar-Helmholtz Centre for Ocean Research Kiel; Alemania Fil: Sainmont, J.. Technical University of Denmark; Dinamarca. Centre for Ocean Life; Dinamarca Fil: Traving, S. J.. Centre for Ocean Life; Dinamarca. Universidad de Copenhagen; Dinamarca Fil: Visser, A. W.. Centre for Ocean Life; Dinamarca. Technical University of Denmark; Dinamarca Fil: Wadhwa, N.. Centre for Ocean Life; Dinamarca. Technical University of Denmark; Dinamarca Fil: Kiørboe, T.. Centre for Ocean Life; Dinamarca. Technical University of Denmark; Dinamarca

The purpose of this dataset was to compile adult and offspring size estimates for marine organisms. Adult and offspring size estimates of 408 species were compiled from the literature covering17 orders of magnitude in body mass and including Cephalopoda (ink fish), Cnidaria ("jelly" fish), Crustaceans, Ctenophora (comb jellies), Elasmobranchii (cartilaginous fish), Mammalia (mammals), Sagittoidea (arrow worms) and Teleost (i.e., Actinopterygii, bony fish). Individual size estimates were converted to standardized size estimates (carbon weight, g) to allow for among-group comparisons. This required a number of size estimates to be converted and a compilation of conversion factors obtained from the literature are also presented.

Climate change affects ecological communities through its impact on the physiological performance of individuals. However, the population dynamic of species well inside their thermal niche is also determined by competitors, prey and predators, in addition to being influenced by temperature changes. We use a trait-based food-web model to examine how the interplay between the direct physiological effects from temperature and the indirect effects due to changing interactions between populations shapes the ecological consequences of climate change for populations and for entire communities. Our simulations illustrate how isolated communities deteriorate as populations go extinct when the environment moves outside the species' thermal niches. High-trophic-level species are most vulnerable, while the ecosystem function of lower trophic levels is less impacted. Open communities can compensate for the loss of ecosystem function by invasions of new species. Individual populations show complex responses largely uncorrelated with the direct impact of temperature change on physiology. Such complex responses are particularly evident during extinction and invasion events of other species, where climatically well-adapted species may be brought to extinction by the changed food-web topology. Our results highlight that the impact of climate change on specific populations is largely unpredictable, and apparently well-adapted species may be severely impacted.

Integrated assessment of the status of marine biodiversity is and has been problematic compared to, for example, assessments of eutrophication and contamination status, mostly as a consequence of the fact that monitoring of marine habitats, communities and species is expensive, often collected at an incorrect spatial scale and/or poorly integrated with existing marine environmental monitoring efforts. The objective of this Method Paper is to introduce and describe a simple tool for integrated assessment of biodiversity status based on the HELCOM Biodiversity Assessment Tool (BEAT), where interim biodiversity indicators are grouped by themes: broad-scale habitats, communities, and species as well as supporting non-biodiversity indicators. Further, we report the application of an initial indicator-based assessment of biodiversity status of Danish marine waters where we have tentatively classified the biodiversity status of Danish marine waters. The biodiversity status was in no areas classified as “unaffected by human activities.” In all the 22 assessment areas, the status was classified as either “moderately affected by human activities” or “significantly affected by human activities.” Spatial variations in the biodiversity status were in general related to the eutrophication status as well as fishing pressure. &nbsp

Species with a large adult-offspring size ratio and a preferred predator-prey mass ratio undergo ontogenetic trophic niche shift(s) throughout life. Trophic interactions between such species vary throughout life, resulting in different species-level interaction motifs depending on the maximum adult sizes and population size distributions. We explore the assembly and potential for coexistence of small communities where all species experience ontogenetic trophic niche shifts. The life-history of each species is described by a physiologically structured model and species identity is characterised by the trait: size at maturation. We show that a single species can exist in two different states: a 'resource driven state' and a 'cannibalistic state' with a large scope for emergent Allee effects and bistable states. Two species can coexist in two different configurations: in a 'competitive coexistence' state when the ratio between sizes at maturation of the two species is less than a predator-prey mass ratio and the resource level is low to intermediate, or in a 'trophic ladder' state if the ratio of sizes at maturation is larger than the predator-prey mass ratio at all resource levels. While there is a large scope for coexistence of two species, the scope for coexistence of three species is limited and we conclude that further trait differentiation is required for coexistence of more species-rich size-structured communities.

The main topic of this paper is the linear two-axis Micro Opto Electro Mechanical System (MOEMS) sun sensor developed for the pico satellite DTUsat; the size of the sensor chip is ∼ 7 × 8mm. The sensor has a Field of View (FOV) of ±70◦ and a resolution better than 1◦ is obtainable for −40◦ to 40◦; beyond these angles resolution below 1◦ is difficult. One complete sensor chip along with needed measurement and interface electronics has been implemented on a 3.9×5cm2 PCB with a mass of 7.1g. In the paper an overview is first given of DTUsat followed by descriptions of functionality, design, realisation, integration, and performance of the sun sensor. Furthermore the paper includes a discussion on the topic Micro Electro Mechanical Systems (MEMS) in space since it is the authors’ opinion that the space society is missing out on many of the advantages MEMS can bring. MEMS can improve many traditional systems and enable construction of devices not possible with traditional techniques. On DTUsat MEMS had to be employed to contain the desired complexity in the CubeSat frame. ∗M.Sc. student at Mikroelektronik Centret (MIC). Copyright Statement Stamp Figure 1: DTUsat in the assembly phase. 1 THE DTUsat PROJECT In the summer of 2001 a group of students at the Technical University of Denmark (DTU) teamed up with the idea of building and launching a satellite in just one year! This very ambitious goal – none of the students had experience with satellite construction – was made to keep the motivation going during the entire project phase. It was thought that the students would be less interested if their project would not be launched while they were still students. However, after the initial design phase the suggested satellite was too complex to be realised in just one year. Instead of making a simple and “boring” satellite it was decided to extend the project to two years – the DTUsat project was born.† This also proved wise since finding a launch provider for a CubeSat ended up being a very difficult task which was only †More info on DTUsat can be found on its web page at http://www.dtusat.dtu.dk/. M. Pedersen, J.H. Hales, and R.W. Fleron 1 54th International Astronautical Congress accomplished due the great assistance provided by the Danish Space Research Institute (DSRI). A group of ∼ 70 students have been involved with the project and ∼ 15 students have been fully involved during the entire project. The CubeSat concept was chosen since it allows launch costs of only 35,000-70,000USD per satellite. The CubeSat gives all the basic mechanical constraints; e.g. it must be 10 × 10 × 10cm and have a mass of max 1kg. DTUsat, which can be seen in figure 1, is divided into six different sub systems. These are briefly described in the following. Power utilises solar panels on four sides and is capable of delivering ∼ 1.5W. The battery provides additional power during radio transmission where the power consumption exceeds the available solar energy. Latch-up protection is also included in this sub system. On-Board Computer (OBC) contains of course CPU, ROM, RAM, Flash-RAM etc. Furthermore OBC serves as a motherboard on DTUsat since all PCBs (except sun sensors and camera) are mounted on the OBC. Radio communicates in agreement with AMSAT with the ground station at 437.475MHz. The antenna is circular polarised and sufficiently omnidirectional to operate without attitude control. ACDS contains a 4-axis magnetometer, two-axis sun sensors on five of DTUsat’s sides, and three 1μNm PWM magnetotorquers mounted on the inside of three side panels. A close-up of the sun sensor is shown in figure 2. Tether Payload is the scientific mission. After 1-2 months a 500m electrodynamic tether will be deployed to demonstrate lowering of the orbit due to interaction with the geomagnetic field. It was intended to increase the speed of the altitude change by emitting electrons with a MEMS emitter. However this is not possible since the emitter was not finished in time. Camera Payload is the public relations payload. Its original purpose was to produce pictures of Denmark, but since the camera electronics was not finished in time only a one pixel infrared camera is present. This can be used to investigate the temperatures the CCD will be exposed to with the developed lens. Figure 2: Close-up on a sun sensor. DTUsat was launched on June 30 at 14:15:12GMT from Plesetsk, Russia. However this far contact has not been established. DTUsat was in the same P-POD as the other Danish student satellite AUC CubeSat and the Canadian Can-X with whom only AUC CubeSat has been able to establish radio contact. Investigation of why contact has not been established is currently being conducted. However, it can to some extent be caused by its complexity which only left very short time for testing while AUC CubeSat is more simple and had more time for testing. Naturally it is disappointing that contact has not been established, but seen in the light of the fact that it is build by students on a low budget just finalising the satellite was a huge milestone in itself. It is the current intention to launch a DTUsatX ∣∣ X=1,2,3... every second year since the project produces real engineers; that is the students must combine many professions with practical applications. Hopefully the next DTUsat will be a success since it will not be build from scratch.