Jan Heuschele

University of Oslo · Department of Biosciences

The ongoing global climate crisis increases temperatures in polar regions faster and with greater magnitude than elsewhere. The decline of Arctic sea ice opens up new passages, eventually leading to higher anthropogenic activities such as shipping, fishing, and mining. Climate change and anthropogenic activities will increase contaminant transport...

The Arctic polar nights bring extreme environmental conditions characterised by cold and darkness, which challenge the survival of organisms in the Arctic. Additionally, multiple anthropogenic stressors can amplify the pressure on the fragile Arctic ecosystems during this period. Determining how multiple anthropogenic stressors may affect the survi...

The macroecological drivers of freshwater diversity are accredited geographical, spatial and climatic variables, but also to productivity, ecosystem age and landscape history. Locally diversity is also influenced by the dispersal ability of species. Here we evaluated how spatial and climatic variables influence species richness and macroecological...

Repeated size measurements of individual animals are valuable data for many research questions, but it is often hard to obtain without causing stress or damage to the animal. We developed a video-based approach called Zoobooth to size individual zooplankton, which involves a low risk of handling accidents and stress. Here we describe the process of...

Boreal lakes are the most abundant lakes on Earth. Changes in acid rain deposition, climate, and catchment land use have increased lateral fluxes of terrestrial dissolved organic matter (DOM), resulting in a widespread browning of boreal freshwaters. This browning affects the aqueous communities and ecosystem processes, and boost emissions of the g...

Copper is both an essential trace element and a potent pesticide. The use of copper as an antifoulant has increased in the last decades in line with the expanding aquaculture and shipping industries. In aquatic environments, it also affects non-target taxa. One of which are copepods, which constitute the central link in the marine food web. Despite...

Harmful algae bloom (HAB) forecasting has developed rapidly over recent decades, but predicting harmful levels of marine biotoxins in shellfish is still a challenge. New discoveries suggest that predator‐prey interactions may be an important driver in the formation of HABs. Key species of harmful algae respond to copepod infochemicals with increase...

Previous experimental studies suggest that the production of sound associated with expelling gas from an open swimbladder may play a role in communication. This would suggest non-random gas release. We used deployed echosounders to study patterns of gas release among a fjord population of sprat ( Sprattus sprattus ). The echosounder records concurr...

Understanding growth and development over ontogeny, and the effects of stressors on life history, requires bioenergetic analysis, for example using models based on dynamic energy budget theory. Such analyses require precise and accurate determination of the animal's biomass or biovolume over time. Automated imaging offers great advantages by allowi...

Traditional ecotoxicology methods involving copepods have focused on exposure of pooled individuals and averaged responses, but there is increasing awareness of the importance of individual variation. Many biological traits are density‐dependent, and decisions to use single‐individual or pooled exposure may affect responses to anthropogenic stresso...

Natural biotic and anthropogenic stressors can interact to alter contaminant toxicity. Energetic restrictions are potential mechanisms causing this pattern. To identify processes underlying observed effects of predation risk and copper (Cu) on delayed copepod age at maturity, we examined how these two stressors affect respiration rates. We tested t...

In ecotoxicology and aquatic ecology, we often ignore responses of individuals and focus on average responses. Yet, both terrestrial and aquatic animals display consistent behavioural differences between individuals. The distribution of behavioural differences within a population contains vital information for predicting population responses to nov...

Copper (Cu) is an essential trace metal, but may also be toxic to aquatic organisms. While many studies have investigated the cytotoxicity of Cu, little is known about the in vivo genotoxic potential of Cu in marine invertebrates. We investigated the genotoxicity of Cu in two pelagic calanoid copepods Acartia tonsa and Temora longicornis and the in...

Individual trait variation is essential for populations to cope with multiple stressors and continuously changing environments. The immense number of possible stressor combinations and the influence of phenotypic variation makes experimental testing for effects on organisms challenging. The acquisition of such data requires many replicates and is n...

To examine whether natural stressors like predation risk affect responses to anthropogenic contaminants, we exposed nauplii of the copepod Tigriopus brevicornis to chemical cues from fish (kairomones) and copper (Cu). We tested effects of these treatments, singly and combined, on copepod age and size at maturity, and development stage sensitivity,...

In the last decades, limnic water bodies in the Northern hemisphere have experienced a noticeable browning, i.e., increasing levels of dissolved organic matter (DOM). While the effects on primary producers is usually considered negative (light attenuation), zooplankton is thought to benefit from increased DOM, which absorbs harmful ultraviolet radi...

The flow regime around a chemically baited trap is crucial for the trapping process and distribution of bait downstream of traps. We measured the flow field downstream of a trap prototype in flume experiments and mapped the distribution of bait using laser induced fluorescence. The trap produced a downstream wake, where flow recirculated towards th...

Collaboration between modellers and experimentalists is essential in ecological research, however, different obstacles linking both camps often hinder scientific progress. In this commentary, we discuss several issues of the current state of affairs in this research loop. Backed by an online survey amongst fellow ecologists, modellers and experimen...

The understanding of consistent individual differences in behavior, often termed “personality,” for adapting and coping with threats and novel environmental conditions has advanced considerably during the last decade. However, advancements are almost exclusively associated with higher-order animals, whereas studies focusing on smaller aquatic organ...

Poster for the "A New Age of Discovery for Aquatic Microeukaryotes" Symposium held at EMBL Heidelberg (26-29 Jan 2016)

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 covering >17 orders of magnitude in body mass and including Cephalopoda (ink fish), Cnidaria (“jelly” fish), Crustaceans, Ctenophora (comb jellies), Elasmobranchii (c...

Diatoms are highly abundant unicellular algae that often dominate pelagic as well as benthic primary production in the oceans and inland waters. Being strictly dependent on silica to build their biomineralized cell walls, marine diatoms precipitate 240 × 10e12 mol Si per year, which makes them the major sink in the global Si cycle. Dissolved silici...

Diatoms are highly abundant unicellular algae that often dominate pelagic as well as benthic primary production in the oceans and inland waters. Being strictly dependent on silica to build their biomineralized cell walls, marine diatoms precipitate 240 × 10e12 mol Si per year, which makes them the major sink in the global Si cycle. Dissolved silici...

The movie shows the characteristic back and forth movement of Seminavis robusta (strain F2-31B) synonymous to the run-reverse movement of marine bacteria. Movie was accelerated 10x. Time labels denote min:s.

Supplementary Figures 1-4 and Supplementary Tables 1-7.

The movie shows the response of S. robusta (strain F2-31B) to a control bead (no dSi). dSi-starved cells move randomly around the area and show no response towards the bead. The video speed was accelerated 50 times and the scale bar indicates 50 μm. Time labels denote min:s.

The movie shows the attraction and accumulation of Navicula sp. to a dSi-loaded bead for 20 min. Like S. robusta, this pennate diatom also has a back and forth movement. dSi-starved cells also accumulated towards the bead in less than 300s. The video speed was accelerated 50 times and the scale bar indicates 100 μm. Time labels denote min:s

The movie shows the attraction and accumulation of S. robusta (strain F2-31B) to a dSi-loaded bead. dSi-starved cells began to move towards the bead in less than 300s, indicating that they perceived a gradient of dSi diffusing from the bead. The video speed was accelerated 50 times and the scale bar indicates 50 μm. Time labels denote min:s.

The movie shows S. robusta (strain P36 MT+) starved and exposed to a control bead for 1h. No response towards the bead was observed for the whole observation area. The video speed was accelerated 50 times and the scale bar indicates 100 μm. Time labels denote min:s.

The movie shows S. robusta (strain P36 MT+) starved and exposed to a dSi-loaded bead for 1h. Attraction towards the bead for the whole observation time was evident indicating that the created diffusion gradient was stable for 1h. Furthermore, cells were observed to stop moving around ~25 min which was also observed for dSi-starved cells after bulk...

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 covering >17 orders of magnitude in body mass and including Cephalopoda (ink fish), Cnidaria (“jelly” fish), Crustaceans, Ctenophora (comb jellies), Elasmobranchii (c...

Copepods are ubiquitous in aquatic habitats. They exude bioactive compounds that mediate mate finding or induce defensive traits in prey organisms. However, little is known about the chemical nature of the copepod exometabolome that contributes to the chemical landscape in pelagic habitats. Here we describe the development of a closed loop solid ph...

Alligned peak list showing intensities (peak area) of all measured compounds Alligned peak list from mass spec data. Peak ID in column A, Compound specific mass@retentiontime in column B, and intensities of each compound for each sample in the following columns. below threshold entries denoted as “1”.

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 particularly interest for life in the ocean where a diversity of offspring development strategies is observed along with variability in physical an...

Most animals, including aquatic crustacean zooplankton, perform strong avoidance movements when exposed to a threat, such as ultraviolet radiation (UVR). We here show that the genera Daphnia and Bosmina instantly adjust their vertical position in the water in accordance with the present UVR threat, i.e., seek refuge in deeper waters, whereas other...

Copepods are ubiquitous in aquatic habitats. They exude bioactive compounds that mediate mate finding and induce defensive traits in prey organisms. Little is, however, known about the chemical nature of the copepod exometabolome that contributes to the chemical landscape in pelagic habitats. Here we describe the development of a closed loop solid...

Copepods are ubiquitous in aquatic habitats. They exude bioactive compounds that mediate mate finding and induce defensive traits in prey organisms. Little is, however, known about the chemical nature of the copepod exometabolome that contributes to the chemical landscape in pelagic habitats. Here we describe the development of a closed loop solid...

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, se...

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, se...

Diel vertical migration (DVM) is a common behavior adopted by zooplankton species. DVM is a prominent adaptation for avoiding visual predation during daylight hours and still being able to feed on surface phytoplankton blooms during night. Here, we report on a DVM study using a Video Plankton Recorder (VPR), a tool that allows mapping of vertical z...

An increasing number of studies show the importance of chemical interactions in the aquatic environment. Our understanding of the role of chemical cues and signals in larger crustaceans has advanced in the last decades. However, for copepods, the most abundant metazoan zooplankton and essential for the functioning of the marine food web, much is st...

Phytoplankton composition in the beginning and the end of the experiment with each taxonomic group presented in μg C L−1. Note the different scale of the y axis between sampling dates

The physical environment in the mesocosms during the experiment, if not otherwise indicate lines indicate the average value over the water column and grey areas indicate confidence limits. O2 concentration measured in µM, PAR in µmol s−1W−1

We studied female fertilization status in North Sea summer populations and labora-tory cultures of the marine copepod Temora longicornis and found fractions of fertilized females in both field and laboratory populations that were much smaller (,50%) than predicted by a theoretical model that assumes random mating. Such low fertil-ization rates are...

Reproduction in planktonic animals depends on numerous biotic and abiotic factors. One of them is predation pressure, which can have both direct consumptive effects on population density and sex ratio, and non-consumptive effects, for example on mating and migration behaviour. In copepods, predator vulnerability depends on their sex, motility patte...

The importance of sexual selection for the evolution, dynamics and adaptation of organisms is well known for many species. However, the topic is rarely studied in marine plankton, the basis of the marine food web. Copepods show behaviors that suggest the existence of sexually selected traits, and recent laboratory experiments identified some select...

Many copepod species rely on pheromone cues to find partners. Some parasitic and benthic copepod males are able to distinguish between females of different reproductive states. Here, we demonstrate that the swimming activity and velocity of males of a pelagic copepod, Oithona davisae, increases in the presence of virgin when compared with mated fem...

Mate choice is one of the main mechanisms of sexual selection, with profound implications for individual fitness. Changes in environmental conditions can cause individuals to alter their mate search behaviour, with consequences for mate choice. Human-induced eutrophication of water bodies is a global problem that alters habitat structure and visibi...

Sexual selection is often assumed to increase the viability of populations by increasing the quality of offspring produced. Presently, human-induced environmental changes are altering the process of sexual selection by influencing male–male interactions and female mate choice. Here, we show that increased density of filamentous algae due to eutroph...

Sexual selection can explain major micro- and macro-evolutionary patterns. Much of current theory predicts that the strength of sexual selection (i) is driven by the relative abundance of males and females prepared to mate (i.e. the operational sex ratio, OSR) and (ii) can be generally estimated by calculating intra-sexual variation in mating succe...

Human-induced environmental changes alter terrestrial and aquatic ecosystems worldwide. This influences also evolutionary processes, such as sexual selection, by constraining mate choice and mate competition. Organisms often use multiple cues in mate choice, with different cues indicating the same or different benefits. Because the assessment and i...

Jordens ekologiska system undergår för tillfället stora förändringar pga. människans aktiviteter. Ett växande antal studier visar att dessa förändringar påverkar naturliga och sexuella urvalet och därmed evolutiva processer. Målet med detta arbete var att undersöka effekterna av omgivningsförändringar på sexuella urvalet genom att använda den ökade...

The role of sexual selection in adaptation is disputed. A balance between sexual and viability selection can be achieved in stable environments, but environmental perturbations could change the costs and benefits arising from sexual selection and influence the rate of adaptation. Here we synthesise theoretical and empirical work on the role of sexu...

Human-induced eutrophication is a serious environmental problem that constrains visual communication and influences the mate choice process in fishes. Eutrophication also changes the chemical environment and the pH of the water, which could influence the use of olfactory cues in mate choice. Here, we show that an increase in pH enhances the use of...