Micael Jonsson - Academia.edu (original) (raw)

Papers by Micael Jonsson

Philosophical transactions of the Royal Society of London. Series B, Biological sciences, Jan 19, 2014

The study of animal behaviour is important for both ecology and ecotoxicology, yet research in th... more The study of animal behaviour is important for both ecology and ecotoxicology, yet research in these two fields is currently developing independently. Here, we synthesize the available knowledge on drug-induced behavioural alterations in fish, discuss potential ecological consequences and report results from an experiment in which we quantify both uptake and behavioural impact of a psychiatric drug on a predatory fish (Perca fluviatilis) and its invertebrate prey (Coenagrion hastulatum). We show that perch became more active while damselfly behaviour was unaffected, illustrating that behavioural effects of pharmaceuticals can differ between species. Furthermore, we demonstrate that prey consumption can be an important exposure route as on average 46% of the pharmaceutical in ingested prey accumulated in the predator. This suggests that investigations of exposure through bioconcentration, where trophic interactions and subsequent bioaccumulation of exposed individuals are ignored, un...

Studies investigating effects of aquatic-derived resource subsidies have often found large effect... more Studies investigating effects of aquatic-derived resource subsidies have often found large effects on terrestrial systems. Those studies have mostly been performed on effects of subsidies derived from oceanic and riverine systems, and very few have considered effects of subsidies from freshwater lakes. However, since lakes can produce large quantities of emergent aquatic insects that end up on nearby land, it is likely that also freshwater-lake subsidies influence terrestrial systems. We performed sweepnet collections of aquatic and terrestrial invertebrates at varying distances from the shore on vegetation of islands of varying size, in two freshwater lakes in northern Sweden, as well as on the surrounding mainland. We found that the amounts of aquatic insects on terrestrial vegetation decreased with distance from the shore, and that they were the most abundant on small islands, presumably because small islands have a higher perimeter-to-area ratio. Web-building spiders responded positively to the aquatic subsidy by being the most abundant on small islands and by showing a positive relationship with aquatic insect biomass. However, distance from the shore showed no effects on the spiders. Our results strongly support the view that terrestrial systems are subsidized by lakes, and indicate that freshwaterlake subsidies are important for terrestrial invertebrate community structure on adjacent land. Further, our study shows that ecosystems should be treated as interdependent, not as self-contained units, and may as such be important for an increased understanding of the nature and importance of resource flows across ecosystem boundaries.

The strength of linkages between riparian plants and stream communities can be expected to be inf... more The strength of linkages between riparian plants and stream communities can be expected to be influenced by invading plants. While most studies so far have been focussed on the effects of the leaf litter quality of the invader, this study addresses the impact of detritivores on the pool of detritus. In a natural setting, we found that species richness of shredding macroinvertebrates significantly influenced the breakdown rate of an invasive weed species, the Japanese knotweed (Fallopia japonica), which has become a major plant invader along streams and rivers in Europe and North America. Our findings imply that a reduction of the diversity of shredder species, which may be the result of disturbances, could negatively influence stream ecosystems' capacity of processing knotweed leaves. Although the knotweed showed breakdown rates similar to those of common native tree and shrub species, other exotic leaf species might show considerably slower rates and hence have greater consequences for the ecosystems. We have, in this study, indicated a technique by which the effects of other non-indigenous plants on ecosystem functioning might be considered.

ABSTRACT Over the past half century, ecologists have tried to unravel the factors that drive spec... more ABSTRACT Over the past half century, ecologists have tried to unravel the factors that drive species richness patterns in ecological communities. One influential theory is island biogeography theory (IBT), which predicts that island or habitat area and isolation are drivers of species richness. However, relatively few studies testing IBT have considered invertebrate or belowground communities, and it is unclear as to whether the predictions made by IBT hold for these communities. Other theories predict that habitat characteristics such as vegetation diversity may be important drivers of invertebrate species richness. To investigate patterns of invertebrate density and species richness across gradients of area, isolation, and vegetation diversity, we used a system of 30 lake islands in the boreal zone of northern Sweden. We assessed density and taxonomic richness of ground-dwelling spiders, web-building spiders, beetles, collembolans, mites, and nematodes, for all islands during two consecutive summers. For all invertebrate groups, both density and taxonomic richness were either neutrally or negatively related to island size, and either neutrally or positively related to island isolation. Meanwhile the density and taxonomic richness for several groups was positively related to vegetation diversity (i.e. habitat heterogeneity). In multiple regression analyses, island size was often the single best predictor for both invertebrate density and taxonomic richness, but in some cases island size and isolation in combination explained more variation than each factor considered singly. Contrary to IBT predictions, invertebrate density and richness was never positively related to island size or negatively related to island isolation. Instead, our results suggest that plant diversity (and thus habitat heterogeneity) was the main driver of the patterns that we found, although other factors could have some influence. We conclude that several factors, but not necessarily those predicted as important by IBT, are important in determining invertebrate abundance and species richness in island systems.

1. Climate change is expected to not only raise water temperatures, but also to cause brownificat... more 1. Climate change is expected to not only raise water temperatures, but also to cause brownification of aquatic ecosystems via increased inputs of terrestrial dissolved organic matter. While efforts have been made to understand how increased temperature and brownification separately influence aquatic food webs, their interactive effects have been less investigated. Further, although climate change effects on aquatic ecosystems likely will propagate to terrestrial consumers via changes in aquatic insect emergence, this has rarely been studied. 2. We investigated the effect of climate change on aquatic insect emergence, in a large-scale outdoor pond facility where 16 sectionseach containing natural food webs including a fish top-consumer populationwere subjected to warming (3°C above ambient temperatures) and/or brownification (by adding naturally humic stream water). Aquatic insect emergence was measured biweekly over 18 weeks. 3. We found no effect of warming or brownification on total emergent insect dry mass. However, warming significantly reduced the number of emergent Chironomidae, while numbers of larger taxa, Trichoptera and Ephemeroptera, remained unchanged. On average, 57% and 58% fewer Chironomidae emerged from the warmed clear and humic pond sections, respectively. This substantial decrease in emergent Chironomidae resulted in a changed community structure and on average larger individuals emerging from warm sections as well as from humic sections under ambient conditions. There was also a weak influence of fish biomass on the size structure of emergent aquatic insects, with a positive relationship between individual insect size and total fish biomass, but effects of fish were clearly subordinate to those of warming. 4. Climate change impacts on aquatic systems can have widespread consequences also for terrestrial systems, as aquatic insects are ubiquitous and their emergence represents an important resource flow from aquatic to terrestrial environments. While we found that neither warming nor brownification quantitatively changed total aquatic insect emergence biomass, the warming-induced decrease in number of emergent Chironomidae and the subsequent increase in average body size will likely impact terrestrial consumers relying on emergent aquatic insect as prey.

Standardized ecotoxicological tests still constitute the fundamental tools when doing riskassessm... more Standardized ecotoxicological tests still constitute the fundamental tools when doing riskassessment of aquatic contaminants. These protocols are managed towards minimal mortality in the controls, which is not representative for natural systems where mortality is often high. This methodological bias, generated from assays where mortality in the control group is systematically disregarded, makes it difficult to measure therapeutic effects of pharmaceutical contaminants leading to lower mortality. This is of concern considering that such effects on exposed organisms still may have substantial ecological consequences. In this paper, we illustrate this conceptual problem by presenting empirical data for how the therapeutic effect of Oxazepam-a common contaminant of surface waters-lower mortality rates among exposed Eurasian perch (Perca fluviatilis) from wild populations, at two different life stages. We found that fry hatched from roe that had been exposed to dilute concentrations (1.1 ± 0.3 μg l −1 ) of Oxazepam for 24 h 3-6 days prior to hatching showed lower mortality rates and increased activity 30 days after hatching. Similar effects, i.e. increased activity and lower mortality rates were also observed for 2-year old perch exposed to dilute Oxazepam concentrations (1.2 ± 0.4 μg l −1 ). We conclude that therapeutic effects from pharmaceutical contaminants need to be considered in risk assessment assays to avoid that important ecological effects from aquatic contaminants are systematically missed.

Most large rivers in northern Sweden are regulated to produce hydropower, with subsequent effects... more Most large rivers in northern Sweden are regulated to produce hydropower, with subsequent effects on flow dynamics and aquatic insect communities. Several studies have shown that aquatic and terrestrial systems are intimately connected via the export of emergent aquatic insects, but few have assessed how human modifications of aquatic habitats may influence this connection. We compared breeding success of the insectivorous Pied Flycatcher Ficedula hypoleuca in near-riparian upland forests along two regulated and two free-flowing large rivers in northern Sweden over 3 years. The regulated rivers showed lower aquatic insect export to the surroundings, as a consequence of regulation-induced loss of suitable aquatic insect habitats. Survival of Pied Flycatcher nestlings was 10-15% greater along the free-flowing rivers. Females breeding near the free-flowing rivers also started egg-laying earlier and with greater synchrony than those at the regulated rivers, and showed a smaller decrease in weight during breeding than did females along the regulated rivers. However, there were no differences in occupation rate, clutch size or number of successfully hatched juveniles between regulated and freeflowing rivers. As regulated rivers showed lower abundance of flying aquatic insects, which may also reduce the abundance of terrestrial invertebrate prey, regulation-induced changes in the export of emergent aquatic insects may explain both directly and indirectly the observed reduction in Pied Flycatcher breeding success along regulated rivers. Large-scale river regulation may therefore impair the breeding success of insectivorous birds through impacts on prey availability.

Ecosystems, 2014

to understand how moss communities, associated food webs, and the ecosystem processes they influe... more to understand how moss communities, associated food webs, and the ecosystem processes they influence will respond to environmental change.

Science, 2013

Environmental pollution by pharmaceuticals is increasingly recognized as a major threat to aquati... more Environmental pollution by pharmaceuticals is increasingly recognized as a major threat to aquatic ecosystems worldwide. A variety of pharmaceuticals enter waterways by way of treated wastewater effluents and remain biochemically active in aquatic systems. Several ecotoxicological studies have been done, but generally, little is known about the ecological effects of pharmaceuticals. Here we show that a benzodiazepine anxiolytic drug (oxazepam) alters behavior and feeding rate of wild European perch (Perca fluviatilis) at concentrations encountered in effluent-influenced surface waters. Individuals exposed to water with dilute drug concentrations (1.8 micrograms liter(-1)) exhibited increased activity, reduced sociality, and higher feeding rate. As such, our results show that anxiolytic drugs in surface waters alter animal behaviors that are known to have ecological and evolutionary consequences.

River Research and Applications, 2013

Dam removal to restore ecologically impaired rivers is becoming increasingly common. Although the... more Dam removal to restore ecologically impaired rivers is becoming increasingly common. Although the target often is to facilitate fish migration, dam removal has also been assumed to benefit other types of organisms. Because few studies thus far deal with effects of dam removal on stream macroinvertebrates and because results have been equivocal, we investigated both short-and longer-term dam-removal effects on downstream macroinvertebrate communities. We did this in a before-and-after study of the removal of a dam located in a south Swedish stream. We sampled the benthic fauna 6 months before dam removal and both 6 months and 3.5 years after the dam was removed. We compared species composition, taxonomic richness, total densities and densities of macroinvertebrate groups before and after dam removal and between downstream and reference sites. We found that dam removal reduced some macroinvertebrate taxa at the downstream site, but we found no effect on community composition. Although this corroborates results from previous short-term studies, we also found a reduction of taxonomic richness and that some dam-removal effects persisted or even increased over time. The most likely explanation for the suppression of benthic macroinvertebrate richness following dam removal is a significantly increased sediment transport from the former reservoir and a subsequent loss of preferred substrates. Our results indicate that adverse dam-removal effects may be long lasting but taxon specific. We therefore call for longer-term studies on a variety of organisms to better understand how dam removal may influence downstream macroinvertebrate communities.

Proceedings of the Royal Society B: Biological Sciences, 2002

We removed stream-living macroinvertebrate shredder species in the sequences in which they are pr... more We removed stream-living macroinvertebrate shredder species in the sequences in which they are predicted to disappear, in response to two common types of anthropogenic disturbances: acidification and organic pollution, and analysed the effects on leaf breakdown rates. The experiment was performed in field microcosms using three shredder species. Species identity significantly affected leaf breakdown rates, while species richness per se was non-significant. The simulated sequential species loss showed large effects on leaf breakdown rates, with observed rates being significantly higher than expected from single-species treatments in two, out of four, two-species, and in all four three-species treatments. The invertebrates used in this study were taxonomically distinct (Insecta: Plecoptera and Trichoptera; Crustacea: Amphipoda), and of different sizes, hence a high degree of complementarity was probably present. A method to study the effects of species loss, characteristic of perturbation type, could be more useful than a random approach when investigating the impact of perturbation. Our results may have general applicability for investigations on the effects of diversity loss on ecosystem functioning in any ecosystem exposed to human perturbations, given that the order of extinction is known or can easily be assessed.

Oikos, 2008

ABSTRACT Litter decomposition is an important driver of terrestrial systems, and factors that det... more ABSTRACT Litter decomposition is an important driver of terrestrial systems, and factors that determine decomposition rate for individual litter species have been widely studied. Fewer studies have explored the factors that regulate how mixing litters of multiple species affects litter decomposition and nutrient dynamics, and only a handful of studies have investigated how litter-mixing effects may differ among different habitats or ecosystems, or how they respond to environmental gradients. We used a well-established retrogressive chronosequence involving thirty lake islands in northern Sweden in which time since fire disturbance increases with decreasing island size; smaller islands therefore have reduced rates of aboveground and belowground ecosystem processes. On each of these islands we utilized plots with and without the long-term experimental removal of shrubs. Litters from the six most common plant species on the islands were prepared in single-, three- and six-species litterbags, and placed on both the shrub-removal and non-removal plots on each island to decompose for one year. We found significant non-additive effects of litter mixing on litter decomposition rates, on final litter N and P concentrations, and on litter N loss, but these non-additive effects varied both in direction and magnitude with changed number of species, and even among litter mixtures with the same number of species. Further, the magnitude of non-additive effects of litter mixing on both litter decomposition and nutrient dynamics was significantly influenced by both island size and the interaction between island size and shrub-removal treatment. When shrubs were present, there was a U-shaped relationship between these non-additive effects and island size, while the relationship was positive when shrubs were removed. Hence, our results support previous findings that litter mixing may produce non-additive effects on litter decomposition and nutrient dynamics, and that these effects tend to be idiosyncratic due to the importance of effects of individual species in the mixture. Most importantly, our results show that non-additive litter-mixing effects change greatly across environmental gradients, meaning that the biotic and abiotic characteristics of an ecosystem can be a powerful driver of the magnitude and even the direction of litter-mixing effects on ecosystem processes.

Journal of Ecology, 2012

1. Despite recent interest in linkages between above-and below-ground communities and their conse... more 1. Despite recent interest in linkages between above-and below-ground communities and their consequences for ecosystem processes, much remains unknown about their responses to long-term ecosystem change. We synthesize multiple lines of evidence from a long-term 'natural experiment' to illustrate how ecosystem retrogression (the decline in ecosystem process rates due to long-term absence of major disturbance) drives vegetation change, and thus above-ground and below-ground carbon (C) sequestration, and communities of consumer biota. 2. Our study system involves 30 islands in Swedish boreal forest that form a 5000-year, fire-driven retrogressive chronosequence. Here, retrogression leads to lower plant productivity and slower decomposition and a community shift from plants with traits associated with resource acquisition to those linked with resource conservation. 3. We present consistent evidence that above-ground ecosystem C sequestration declines, while below-ground and total C storage increases linearly for at least 5000 years following fire absence. This increase is driven primarily by changes in vegetation characteristics, impairment of decomposer organisms and absence of humus combustion. 4. Data from contrasting trophic groups show that during retrogression, biomass or abundance of plants and decomposer biota decreases, while that of above-ground invertebrates and birds increases, due to different organisms accessing resources via distinct energy channels. Meanwhile, diversity measures of vascular plants and above-ground (but not below-ground) consumers respond positively to retrogression. 5. We show that taxonomic richness of plants and above-ground consumers are positively correlated with total ecosystem C storage, suggesting that conserving old-growth forests simultaneously maximizes biodiversity and C sequestration. However, we find little observational or experimental evidence that plant diversity is a major driver of ecosystem C storage on the islands relative to other biotic and abiotic factors. 6. Synthesis. Our study reveals that across contrasting islands differing in exposure to a key extrinsic driver (historical disturbance regime and resulting retrogression), there are coordinated responses of soil fertility, vegetation, consumer communities and ecosystem C sequestration, which all feed back to one another. It also highlights the value of well-replicated natural experiments for tackling questions about above-ground-below-ground linkages over temporal and spatial scales that are otherwise unachievable.

Journal of Biogeography, 2011

Frontiers in Ecology and the Environment, 2010

Freshwater Biology, 2001

1. Leaf litter breakdown rates were assessed in 23 boreal streams of varying size (firstseventh ... more 1. Leaf litter breakdown rates were assessed in 23 boreal streams of varying size (firstseventh order) in central and northern Sweden. 2. Shredders were most abundant in small streams, while shredder species richness showed a hump-shaped relationship with ...

Ecology, 2012

Despite the likely importance of inter-year dynamics of plant production and consumer biota for d... more Despite the likely importance of inter-year dynamics of plant production and consumer biota for driving community- and ecosystem-level processes, very few studies have explored how and why these dynamics vary across contrasting ecosystems. We utilized a well-characterized system of 30 lake islands in the boreal forest zone of northern Sweden across which soil fertility and productivity vary considerably, with larger islands being more fertile and productive than smaller ones. In this system we assessed the inter-year dynamics of several measures of plant production and the soil microbial community (primary consumers in the decomposer food web) for each of nine years, and soil microfaunal groups (secondary and tertiary consumers) for each of six of those years. We found that, for measures of plant production and each of the three consumer trophic levels, inter-year dynamics were strongly affected by island size. Further, many variables were strongly affected by island size (and thus bottom-up regulation by soil fertility and resources) in some years, but not in other years, most likely due to inter-year variation in climatic conditions. For each of the plant and microbial variables for which we had nine years of data, we also determined the inter-year coefficient of variation (CV), an inverse measure of stability. We found that CVs of some measures of plant productivity were greater on large islands, whereas those of other measures were greater on smaller islands; CVs of microbial variables were unresponsive to island size. We also found that the effects of island size on the temporal dynamics of some variables were related to inter-year variability of macroclimatic variables. As such, our results show that the inter-year dynamics of both plant productivity and decomposer biota across each of three trophic levels, as well as the inter-year stability of plant productivity, differ greatly across contrasting ecosystems, with potentially important but largely overlooked implications for community and ecosystem processes.

Ecology, 2013

While several studies have explored how short-term ecological responses to disturbance vary among... more While several studies have explored how short-term ecological responses to disturbance vary among ecosystems, experimental studies of how contrasting ecosystems recover from disturbance in the longer term are few. We performed a simple long-term experiment on each of 30 contrasting forested islands in northern Sweden that vary in size; as size decreases, time since fire increases, soil fertility and ecosystem productivity declines, and plant species diversity increases. We predicted that resilience of understory plant community properties would be greatest on the larger, more productive islands, and that this would be paralleled by greater resilience of soil biotic and abiotic properties. For each island, we applied three disturbance treatments of increasing intensity to the forest understory once in 1998, i.e., light trimming, heavy trimming, and burning; a fourth treatment was an undisturbed control. We measured recovery of the understory vascular plant community annually over the following 14 years, and at that time also assessed recovery of mosses and several belowground variables. Consistent with our predictions, vascular plant whole-community variables (total cover, species richness, diversity [Shannon&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s H&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;], and community composition) recovered significantly more slowly on the smaller (least fertile) than the larger islands, but this difference was not substantial, and only noticeable in the most severely disturbed treatment. When an index of resilience was used, we were unable to detect effects of island size on the recovery of any property. We found that mosses and one shrub species (Empetrum hermaphroditum) recovered particularly slowly, and the higher abundance of this shrub on small islands was sufficient to explain any slower recovery of whole-ecosystem variables on those islands. Further, several belowground variables had not fully recovered from the most intense disturbance after 14 yr, and counter to our predictions, the degree of their recovery was never influenced by island size. While several studies have shown large variation among plant communities in their short-term response (notably resistance) to environmental perturbations, our results reveal that when perturbations are applied equally to highly contrasting ecosystems, differences in resilience among them in the longer term can be relatively minor, regardless of the severity of disturbance.

Ecological Research, 2012

ABSTRACT Most large rivers in Sweden are regulated to produce hydropower. This transformation fro... more ABSTRACT Most large rivers in Sweden are regulated to produce hydropower. This transformation from free-flowing rivers to chains of elongate run-of-river impoundments has been shown to have consequences for aquatic, riparian and adjacent upland environments, and for the emergence patterns of aquatic insects that are important for terrestrial consumers. In this study, we investigated bird assemblages in upland-forest environments along seven large rivers (three heavily impounded and four free flowing) in northern Sweden. Bird densities were assessed by point counts in the breeding and post-breeding seasons. While we observed no significant differences in bird species richness between regulated and free-flowing rivers, cumulative densities of two feeding groups of birds (those feeding on seeds and/or large insects and those feeding on small insects) were higher along free-flowing rivers than along regulated rivers in the breeding season, consistent with known differences in aquatic-insect emergence. Further, ordination analyses showed seasonal shifts in bird assemblage structure, and that these shifts differed between regulated and free-flowing rivers and between the two feeding groups. However, the variables explaining the most variance (11–28 %) in bird assemblage structure were related to a gradient of agricultural-to-forest land use. River regulation contributed to the model in the post-breeding season, but was of relatively low importance. Nevertheless, the observed contrasting seasonal shifts in upland-forest bird assemblage structure between regulated and free-flowing rivers suggest that regulation-induced modifications of aquatic-insect emergence and subsequent changes in prey availability to the birds are also important considerations.

Ecography, 2000