Life cycles of Eukiefferiella claripennis (Lundbeck 1898) and Eukiefferiella minor (Edwards 1929) (Diptera: Chironomidae) in spring-fed streams of different temperatures with reference to climate change

The effect of temperature on the life cycles of two chironomid species, Eukiefferiella claripennis and Eukiefferiella minor, was studied by comparing populations from seven spring-fed streams, ranging in annual average temperatures between 5.4°C and 21.3°C. Dependent on stream, both species showed differences in their life cycles: E. claripennis was regarded univoltine in the two coldest streams, IS7 (annual average 5.4°C) and IS11 (5.3°C), and bivoltine or multivoltine in the warmer streams (ranging from 9.7°C to 21.3°C). E. claripennis developed and grew slower in the colder streams compared to the warmer ones. The winter generation in the warmer streams took longer time to complete compared to the summer generation. E. minor was bivoltine in all the streams, with no emergence during the winter in the colder streams, but in one of the warmer streams (IS6, 13.3°C) emergence was continuous throughout the year. In four streams (IS7, cold; IS6, IS5 and IS1, warm) E. minor may even have been multivoltine. There was no trend between the number of generations completed in one year and stream temperature for E. minor. The summer generation of E. minor in the cold stream IS7 produced smaller larvae compared to the winter generation. Following global warming the life cycle of E. claripennis is expected to change from univoltine to bivoltine, and could show changes in emergence pattern. E. minor on the other hand, will likely show less change in its life cycle. Changes in emergence pattern of E. minor could though be possible. doi: 10.5324/fn.v31i0.1367. Published online: 17 October 2012

Chironomidae fauna of springs in Iceland: Assessing the ecological relevance behind Tuxen’s spring classification

In 1937, S.L. Tuxen studied the animal community of hot springs in Iceland, and classified springs according to their relative temperature into cold, tepid, and hot. Eighty years after Tuxen’s study, we revisited some of the hot springs in Skagafjörður, Northern Iceland. Our aim was to compare the invertebrate community of 1937 and today, and to assess the stability of hot spring habitats over the years. To test Tuxen’s spring classification on an ecological basis, we furthermore collected chironomid larvae from 24 springs of a broad range of temperature, with samples taken both at the surface area of the spring and at the groundwater level. The chironomid species composition of hot springs differed from that of cold and tepid springs. Whereas Cricotopus sylvestris, Arctopelopia sp., and Procladius sp. characterised the chironomid community in Icelandic hot springs, cold and tepid springs were dominated by Eukiefferiella minor, Orthocladius frigidus and Diamesa spp. Community composition analyses and the exclusive occurrence of taxa in one of the temperature classes validated the ecological relevance of Tuxen’s spring classification for the chironomid species community. Both environmental parameters and invertebrate community of Icelandic hot springs seem to be the same as 80 years ago. Although springs have the potential to provide stable habitats, they are currently under high anthropogenic pressure, and should be increasingly considered in nature conservation.

Effects of geothermal effluents on macrobenthic communities in a pristine sub-arctic lake

We studied the effects of warm effluents from the Nesjavellir geothermal power plant on benthic invertebrate communities along a depth gradient of 4 m in lake Þingvallavatn, Iceland. Four study sites were selected: 2 heataffected sites and 2 cold reference sites. Thermal pollution was detected down to 0.4 m at both heat-affected sites, which were 7-12 °C higher than at the same depth at the reference sites. Sustained temperatures ≥27 °C, which is 10-17 °C above ambient water temperatures, seems to be detrimental to the gastropod Radix peregra and several of the littoral chironomid species. Such effects were, however, confined to a small area inside a sheltered rift pool at one of the heat-affected sites. Moderate warming up to ~10 °C above ambient lake temperature in summer, seems to benefit R. peregra, potentially through both a higher survival rate and a shorter life cycle. At the heat-affected sites, sustained high temperatures transformed a relatively diverse chironomid community to a species-poor community, dominated by Paratanytarsus sp. and Cricotopus sylvestris. In contrast, the chironomid Eukiefferiella minor was much more prominent at one of the reference sites. To separate thermal from biological effects, more studies are needed on speciesspecific attributes, including time-series data on growth, survival, and reproduction of the main littoral zoobenthic species. Although our research examined short-term responses of aquatic invertebrates to local thermal stress, our results may also be relevant to long-term responses of freshwater ecosystems at high latitudes to climate change and warming

Stream hydraulics and temperature determine the metabolism of geothermal Icelandic streams

Stream ecosystem metabolism plays a critical role in planetary biogeochemical cycling. Stream benthic habitat complexity and the available surface area for microbes relative to the free-flowing water volume are thought to be important determinants of ecosystem metabolism. Unfortunately, the engineered deepening and straightening of streams for drainage purposes could compromise stream natural services. Stream channel complexity may be quantitatively expressed with hydraulic parameters such as water transient storage, storage residence time, and water spiralling length. The temperature dependence of whole stream ecosystem respiration (ER), gross primary productivity (GPP) and net ecosystem production (NEP = GPP−ER) has recently been evaluated with a “natural experiment” in Icelandic geothermal streams along a 5−25 ◦C temperature gradient. There remained, however, a substantial amount of unexplained variability in the statistical models, which may be explained by hydraulic parameters found to be unrelated to temperature. We also specifically tested the additional and predicted synergistic effects of water transient storage and temperature on ER, using novel, more accurate, methods. Both ER and GPP were highly related to water transient storage (or water spiralling length) but not to the storage residence time. While there was an additional effect of water transient storage and temperature on ER (r2 = 0.57; P = 0.015), GPP was more related to water transient storage than temperature. The predicted synergistic effect could not be confirmed, most likely due to data limitation. Our interpretation, based on causal statistical modelling, is that the metabolic balance of streams (NEP) was primarily determined by the temperature dependence of respiration. Further field and experimental work is required to test the predicted synergistic effect on ER. Meanwhile, since higher metabolic activities allow for higher pollutant degradation or uptake, river restoration and management should promote habitat diversity and complexity (hyporheic zone, macrophyte patches, substrate heterogeneity), especially for microbial activity.Le métabolisme des écosystèmes aquatiques fluviaux joue un rôle critique dans les cycles biogéochimiques planétaires. La complexité des habitats benthiques et l’aire disponible pour les microbes par rapport au volume d’eau qui s’écoule sont considérées comme des facteurs importants pour le métabolisme de l’écosystème. Malheureusement, le creusement et l’alignement des cours d’eau pour le drainage des terres pourraient compromettre les services naturels fournis par les cours d’eau. Cette complexité peut être exprimée quantitativement avec des paramètres hydrauliques tels que le stokage transitoire de l’eau dans le lit de la rivière, la durée de résidence du stockage transitoire, et la longueur du flux en hélice (ou spirale) de l’eau (distance moyenne parcourue par une molécule d’eau dans la zone d’eau courante libre avant d’entrer dans la zone calme). L’effet de la température sur la respiration globale des ruisseaux (ER), productivité primaire brute (GPP) et production nette de l’écosystème (NEP) a récemment été évalué au travers d’une « expérience naturelle » dans des ruisseaux géothermiques islandais le long d’un gradient de température de 5−25 ◦C. Il resta, cependant, une quantité substantielle de variabilité non expliquée par les modèles statistiques, qui pourrait être expliquée par les paramètres hydrauliques non reliés à la température. Nous avons aussi tout particulièrement testé les effets additionnels et en synergie du stokage transitoire de l’eau et de la température sur la respiration, en utilisant de nouvelles méthodes. ER and GPP furent hautement corrélées au stockage transitoire de l’eau (ou flux en hélice de l’eau), mais pas à la durée de résidence du stockage. Le stokage transitoire de l’eau et de la température eurent un effect additionnel sur ER (r2 = 0,57 ; P = 0,015), en revanche GPP était plus liée au stockage transitoire de l’eau qu’à la température. L’effet en synergie ne put être confirmé, probablement dû aux limitations des données. Notre interpretation, basée sur un modèle statistique causal, est que l’équilibre métabolique des cours d’eau (NEP) était principalement contrainte par la réponse de la respiration à la température. D’autres travaux de terrain et expérimentaux sont nécessaires pour tester notre nouvelle hypothèse d’un effet en synergie sur ER. Dans l’attente, puisqu’une plus haute activité métabolique permet une rétention ou dégradation plus importante des polluants, la restoration et la gestion des cours d’eau devraient promouvoir la diversité et la complexité des habitats (hyporhéos, touffes de macrophytes, hété- rogénéité du substrat) particulièrement pour l’activité microbienne.This study was funded by the Scottish Government Rural and Environment Research and Analysis Directorate (RERAD), now Rural and Environment Science and Analytical Services (RESAS). J.R.M. acknowledges the support of the Richard Stockton College of New Jersey. We would like to thank Tryggvi Thordarson, director of the Research Station at Hveragerdi for lodging and his warm hospitality, Marc Stutter and two anonymous referees for their insightful comments on the manuscript.Peer ReviewedRitrýnt tímari

Seasonal variation in the invertebrate community and diet of a top fish predator in a thermally stable spring

Many life-history events in aquatic invertebrates are triggered by seasonal changes in water temperature, but other ecological factors may be important as well. To rule out the confounding effects of changing water temperature, we studied the seasonal dynamics of an aquatic invertebrate community and their effect on a top fish predator in a thermally stable freshwater spring in South Iceland. We sampled benthic invertebrates five times over a year and conducted a mark-recapture study on the top predator in the system, small benthic Arctic charr, Salvelinus alpinus (L.). We assessed variation in diet composition and feeding preferences by calculating the electivity and individual specialisation of each fish at each sampling time. There was a clear separation of winter and summer communities for the benthic invertebrates. The variation in prey availability was also reflected in the fish diet, with higher feeding selectivity in summer than in winter for the highly abundant Chironomidae larvae. In contrast, individual specialisation as a measure of intrapopulation niche variation was higher in winter when prey availability was lower. We furthermore found that groundwater amphipods might play an important role in the winter diet of spring-dwelling Arctic charr. In conclusion, seasonal variation in the invertebrate community is an important factor to consider and has the potential to alter the phenotype (e.g. growth rates) and behaviour (e.g. feeding preferences) of higher trophic levels

Temperature effects on fish production across a natural thermal gradient

Global warming is widely predicted to reduce the biomass production of top predators, or even result in species loss. Several exceptions to this expectation have been identified, however, and it is vital that we understand the underlying mechanisms if we are to improve our ability to predict future trends. Here, we used a natural warming experiment in Iceland and quantitative theoretical predictions to investigate the success of brown trout as top predators across a stream temperature gradient (4–25 °C). Brown trout are at the northern limit of their geographic distribution in this system, with ambient stream temperatures below their optimum for maximal growth, and above it in the warmest streams. A five‐month mark‐recapture study revealed that population abundance, biomass, growth rate, and production of trout all increased with stream temperature. We identified two mechanisms that contributed to these responses: (1) trout became more selective in their diet as stream temperature increased, feeding higher in the food web and increasing in trophic position; and (2) trophic transfer through the food web was more efficient in the warmer streams. We found little evidence to support a third potential mechanism: that external subsidies would play a more important role in the diet of trout with increasing stream temperature. Resource availability was also amplified through the trophic levels with warming, as predicted by metabolic theory in nutrient‐replete systems. These results highlight circumstances in which top predators can thrive in warmer environments and contribute to our knowledge of warming impacts on natural communities and ecosystem functioning

Temperature and spatial connectivity drive patterns in freshwater macroinvertebrate diversity across the Arctic

Warming in the Arctic is predicted to change freshwater biodiversity through loss of unique taxa and northward range expansion of lower latitude taxa. Detecting such changes requires establishing circumpolar baselines for diversity, and understanding the primary drivers of diversity. We examined benthic macroinvertebrate diversity using a circumpolar dataset of &gt;1,500 Arctic lake and river sites. Rarefied α diversity within catchments was assessed along latitude and temperature gradients. Community composition was assessed through region-scale analysis of β diversity and its components (nestedness and turnover), and analysis of biotic–abiotic relationships. Rarefied α diversity of lakes and rivers declined with increasing latitude, although more strongly across mainland regions than islands. Diversity was strongly related to air temperature, with the lowest diversity in the coldest catchments. Regional dissimilarity was highest when mainland regions were compared with islands, suggesting that connectivity limitations led to the strongest dissimilarity. High contributions of nestedness indicated that island regions contained a subset of the taxa found in mainland regions. High Arctic rivers and lakes were predominately occupied by Chironomidae and Oligochaeta, whereas Ephemeroptera, Plecoptera, and Trichoptera taxa were more abundant at lower latitudes. Community composition was strongly associated with temperature, although geology and precipitation were also important correlates. The strong association with temperature supports the prediction that warming will increase Arctic macroinvertebrate diversity, although low diversity on islands suggests that this increase will be limited by biogeographical constraints. Long-term harmonised monitoring across the circumpolar region is necessary to detect such changes to diversity and inform science-based management.</p

Regional impacts of warming on biodiversity and biomass in high latitude stream ecosystems across the Northern Hemisphere

Warming can have profound impacts on ecological communities. However, explorations of how differences in biogeography and productivity might reshape the effect of warming have been limited to theoretical or proxy-based approaches: for instance, studies of latitudinal temperature gradients are often conflated with other drivers (e.g., species richness). Here, we overcome these limitations by using local geothermal temperature gradients across multiple high-latitude stream ecosystems. Each suite of streams (6-11 warmed by 1-15°C above ambient) is set within one of five regions (37 streams total); because the heating comes from the bedrock and is not confounded by changes in chemistry, we can isolate the effect of temperature. We found a negative overall relationship between diatom and invertebrate species richness and temperature, but the strength of the relationship varied regionally, declining more strongly in regions with low terrestrial productivity. Total invertebrate biomass increased with temperature in all regions. The latter pattern combined with the former suggests that the increased biomass of tolerant species might compensate for the loss of sensitive species. Our results show that the impact of warming can be dependent on regional conditions, demonstrating that local variation should be included in future climate projections rather than simply assuming universal relationships

Iceland screens, treats, or prevents multiple myeloma (iStopMM): a population-based screening study for monoclonal gammopathy of undetermined significance and randomized controlled trial of follow-up strategies.

To access publisher's full text version of this article, please click on the hyperlink in Additional Links field or click on the hyperlink at the top of the page marked DownloadMonoclonal gammopathy of undetermined significance (MGUS) precedes multiple myeloma (MM). Population-based screening for MGUS could identify candidates for early treatment in MM. Here we describe the Iceland Screens, Treats, or Prevents Multiple Myeloma study (iStopMM), the first population-based screening study for MGUS including a randomized trial of follow-up strategies. Icelandic residents born before 1976 were offered participation. Blood samples are collected alongside blood sampling in the Icelandic healthcare system. Participants with MGUS are randomized to three study arms. Arm 1 is not contacted, arm 2 follows current guidelines, and arm 3 follows a more intensive strategy. Participants who progress are offered early treatment. Samples are collected longitudinally from arms 2 and 3 for the study biobank. All participants repeatedly answer questionnaires on various exposures and outcomes including quality of life and psychiatric health. National registries on health are cross-linked to all participants. Of the 148,704 individuals in the target population, 80 759 (54.3%) provided informed consent for participation. With a very high participation rate, the data from the iStopMM study will answer important questions on MGUS, including potentials harms and benefits of screening. The study can lead to a paradigm shift in MM therapy towards screening and early therapy.Black Swan Research Initiative by the International Myeloma Foundation Icelandic Centre for Research European Research Council (ERC) University of Iceland Landspitali University Hospita

Physical and cognitive impact following SARS-CoV-2 infection in a large population-based case-control study

© 2023. The Author(s).BACKGROUND: Persistent symptoms are common after SARS-CoV-2 infection but correlation with objective measures is unclear. METHODS: We invited all 3098 adults who tested SARS-CoV-2 positive in Iceland before October 2020 to the deCODE Health Study. We compared multiple symptoms and physical measures between 1706 Icelanders with confirmed prior infection (cases) who participated, and 619 contemporary and 13,779 historical controls. Cases participated in the study 5-18 months after infection. RESULTS: Here we report that 41 of 88 symptoms are associated with prior infection, most significantly disturbed smell and taste, memory disturbance, and dyspnea. Measured objectively, cases had poorer smell and taste results, less grip strength, and poorer memory recall. Differences in grip strength and memory recall were small. No other objective measure associated with prior infection including heart rate, blood pressure, postural orthostatic tachycardia, oxygen saturation, exercise tolerance, hearing, and traditional inflammatory, cardiac, liver, and kidney blood biomarkers. There was no evidence of more anxiety or depression among cases. We estimate the prevalence of long Covid to be 7% at a median of 8 months after infection. CONCLUSIONS: We confirm that diverse symptoms are common months after SARS-CoV-2 infection but find few differences between cases and controls in objective parameters measured. These discrepancies between symptoms and physical measures suggest a more complicated contribution to symptoms related to prior infection than is captured with conventional tests. Traditional clinical assessment is not expected to be particularly informative in relating symptoms to a past SARS-CoV-2 infection.Peer reviewe