Hvammstangi, Iceland
Hvammstangi, Iceland

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Granquist S.M.,Institute of Freshwater Fisheries | Thorhallsdottir A.G.,Agricultural University of Iceland | Sigurjonsdottir H.,University of Iceland
Applied Animal Behaviour Science | Year: 2012

Earlier research indicates that stallions may supress interactions of their harem members, leading to less stable hierarchies and friendship bonds in harems compared to non-stallion groups. In this paper, the effect of the presense of a stallion on the social behaviour of mares was studied by comparing six harems containing stallions to four mixed sex groups not containing stallions. Both temporary and permanent harems were studied, giving the possibility to investigate the effect of group stability on social interactions.A significant linear hierarchy was found in all non-stallion groups that were used for comparison, while the hierarchies were only found to be linear in three of the six harems containing stallions (Landaus h', p<0.05). Aggression rate was lower (t-test, p<0.05) and fewer friendship bonds (G-test, p<0.0001) were found within the harems, compared to the groups without stallions. Stallions seldom intervene directly in interactions between harem members. Thus, our results give support to the hypothesis that stallions may suppress interactions of harem members, but in a more indirect way than with direct interference. In addition, our results give support for earlier findings that aggression rate may be affected by group stability. We found a higher aggression rate in the temporary harems compared to the permanent harems (Kruskal-Wallis, p<0.05) and in the temporary non-stallion group compared to the permanent non-stallion group. The results have significance for further research on social structure of mammals, and may be applied in management of domestic animals. © 2012 Elsevier B.V.

Demars B.O.L.,Macaulay Institute | Russell Manson J.,Pomona College | Olafsson J.S.,Institute of Freshwater Fisheries | Gislason G.M.,University of Iceland | And 7 more authors.
Freshwater Biology | Year: 2011

1. It is becoming increasingly clear that fresh waters play a major role in the global C cycle. Stream ecosystem respiration (ER) and gross primary productivity (GPP) exert a significant control on organic carbon fluxes in fluvial networks. However, little is known about how climate change will influence these fluxes. 2. Here, we used a 'natural experiment' to demonstrate the role of temperature and nutrient cycling in whole-system metabolism (ER, GPP and net ecosystem production - NEP), in naturally heated geothermal (5-25°C) Icelandic streams. 3. We calculated ER and GPP with a new, more accurate method, which enabled us to take into account the additional uncertainties owing to stream spatial heterogeneity in oxygen concentrations within a reach. ER ranged 1-25gCm-2day-1 and GPP 1-10gCm-2day-1. The median uncertainties (based on 1 SD) in ER and GPP were 50% and 20%, respectively. 4. Despite extremely low water nutrient concentrations, high metabolic rates in the warm streams were supported by fast cycling rates of nutrients, as revealed from inorganic nutrient (N, P) addition experiments. 5. ER exceeded GPP in all streams (with average GPP/ER=0.6) and was more strongly related to temperature than GPP, resulting in elevated negative NEP with warming. We show that, as a first approximation based on summer investigations, global stream carbon emission to the atmosphere would nearly double from 0.12PgCyear-1 at 13°C to 0.21 (0.15-0.33) PgCyear-1 with a 5°C warming. 6. Compared to previous studies from natural systems (including terrestrial ecosystems), the temperature dependence of stream metabolism was not confounded by latitude or altitude, seasonality, light and nutrient availability, water chemistry, space availability (water transient storage), and water availability. 7. Consequently, stream nutrient processing is likely to increase with warming, protecting downstream ecosystems (rivers, estuaries, coastal marine systems) during the summer low flows from nutrient enrichment, but at the cost of increased CO2 flux back to the atmosphere. © 2011 Blackwell Publishing Ltd.

Kristjansson B.K.,Holar University College | Malmquist H.J.,Natural History Museum of Kopavogur | Ingimarsson F.,Natural History Museum of Kopavogur | Antonsson T.,Institute of Freshwater Fisheries | And 2 more authors.
Biological Journal of the Linnean Society | Year: 2011

The common occurrence of parallel phenotypic patterns suggests that a strong relationship exists between ecological dynamics and micro-evolution. Comparative studies from a large number of populations under varying sets of ecological drivers could contribute to a better understanding of this relationship. We used data on morphology of arctic charr (Salvelinus alpinus) and ecological factors from 35 Icelandic lakes to test the hypothesis that morphological patterns among monomorphic charr populations from different lakes are related to interlake variation in ecological characteristics. There is extensive phenotypic diversity among populations of Icelandic charr, and populations are easily distinguished based on overall body morphology. The results obtained in the present study showed that the morphological diversity of charr was related to large-scale diversity in lake ecology. Variation in charr morphology was related to water origin (e.g. spring fed versus run-off), bedrock age, and fish community structure. The present study shows how various ecological factors can shape the biological diversity that we observe. © 2011 The Linnean Society of London.

Hannesdottir E.R.,University of Iceland | Gislason G.M.,University of Iceland | Olafsson J.S.,Institute of Freshwater Fisheries | Olafsson T.P.,University of Iceland | And 2 more authors.
Advances in Ecological Research | Year: 2013

Metabolic theory predicts that warming will increase the energetic demands of organisms, with especially strong effects on larger individuals. Mean individual body size should therefore decline, which also implies a loss of biomass at higher trophic levels. If resources are plentiful and easily assimilated, however, the required to persist in warmer environments may be attained, leading to faster growth rates and an overall increase in the biomass of apex predators. Here, we investigated the response of different trophic groups to increasing temperature in a system of geothermal streams in Iceland, exposed to a temperature gradient of 5-21. °C. These streams provide an ideal natural experiment for isolating the effects of warming in multispecies systems, as they have broadly similar geographical and physicochemical features. The macrophyte cover increased significantly with increasing stream temperature, suggesting a greater resource pool for macroinvertebrates (either through direct grazing or feeding on epiphytes). This was reflected by a greater number of generations in 1 year among macroinvertebrates: species in the coldest streams were either uni- or bivoltine, while those in the warmer streams were mostly bivoltine or multivoltine. Differences in phenology were also seen among streams, with emergence of adults limited mostly to the summer months in the colder streams, but occurring year-round in the warmer streams. Macroinvertebrates also grew faster with increasing temperature, contributing to greater population biomass and secondary production in the warmer streams. This increase in prey availability likely produced more favourable conditions for top predators in the warmer streams, leading to an increasing biomass of brown trout with increasing temperature. These findings suggest that warming does not necessarily favour the small in aquatic ecosystems, with high-resource availability, faster reproductive and growth rates and greater production all contributing to meet the high-metabolic demands of apex predators in warmer environments. © 2013 Elsevier Ltd.

Kristmundsson A.,University of Iceland | Antonsson T.,Institute of Freshwater Fisheries | Arnason F.,Institute of Freshwater Fisheries
Bulletin of the European Association of Fish Pathologists | Year: 2010

Proliferative kidney disease caused by the myxozoan parasite Tetracapsuloides bryosalmonae is reported for the first time in Iceland. Infections were confirmed in both arctic charr and brown trout but only arctic charr showed clinical signs. The last two decades, populations of arctic charr in several lakes in Iceland have greatly declined. Possible relation of this decline with increasing water temperature has been speculated. It is hypothesized that PKD may play a significant role in this decline. Studies on the distribution of PKD and its effect on wild populations of arctic charr and brown trout in Iceland are presently in progress.

Gudmundsdottir R.,University of Iceland | Gudmundsdottir R.,Norwegian University of Science and Technology | Olafsson J.S.,Institute of Freshwater Fisheries | Palsson S.,University of Iceland | And 2 more authors.
Freshwater Biology | Year: 2011

1.Spring-fed streams, with temperatures ranging from 7.1 to 21.6°C, in an alpine geothermal area in SW Iceland were chosen to test hypotheses on the effects of nutrients and temperature on stream primary producers. Ammonium nitrate was dripped into the lower reaches of eight streams, with higher reaches being used as controls, during the summers of 2006 and 2007. Dry mass of larger primary producers, epilithic chlorophyll a and biovolumes of epilithic algae were measured. 2.Bryophyte communities were dominated by Fontinalis antipyretica, and biomass was greatest in the warmest streams. Jungermannia exsertifolia, a liverwort, was found in low densities in few samples from cold streams but this species was absent from the warmest streams. 3.Nutrient enrichment increased the biomass of bryophytes significantly in warm streams. No effects of the nutrient addition were detected on vascular plants. The biomass of larger filamentous algae (mainly Cladophora spp.) was significantly increased by nutrient enrichment in cold streams but reduced by nutrients in warm streams. Thalloid cyanobacteria (Nostoc spp.) were not affected by nutrients in cold streams but decreased with nutrient addition in warm streams. Epilithic algal chlorophyll a was increased by nutrients in all streams and to a greater extent in 2007 than in 2006. Nutrient addition did not affect the epilithic chlorophyll a differently in streams of different temperatures. 4.There were small differential effects of nutrients, influenced by pH and conductivity, on different epilithic algal groups. 5.As global temperatures increase, animal husbandry and perhaps crop agriculture are likely to increase in Iceland. Temperature will directly influence the stream communities, but its secondary effects, manifested through agricultural eutrophication, are likely to be much greater. © 2011 Blackwell Publishing Ltd.

Woodward G.,Queen Mary, University of London | Dybkjaer J.B.,University of Aarhus | Olafsson J.S.,Institute of Freshwater Fisheries | Gislason G.M.,University of Iceland | And 3 more authors.
Global Change Biology | Year: 2010

The Earth is experiencing historically unprecedented rates of warming, with surface temperatures projected to increase by 3-5 °C globally, and up to 7.5 °C in high latitudes, within the next century. Knowledge of how this will affect biological systems is still largely restricted to the lower levels of organization (e.g. species range shifts), rather than at the community, food web or ecosystem level, where responses cannot be predicted from studying single species in isolation. Further, many correlational studies are confounded with time and/or space, whereas experiments have been mostly confined to laboratory microcosms that cannot capture the true complexity of natural ecosystems. We used a 'natural experiment' in an attempt to circumvent these shortcomings, by characterizing community structure and trophic interactions in 15 geothermal Icelandic streams ranging in temperature from 5 °C to 45 °C. Even modest temperature increases had dramatic effects across multiple levels of organization, from changes in the mean body size of the top predators, to unimodal responses of species populations, turnover in community composition, and lengthening of food chains. Our results reveal that the rates of warming predicted for the next century have serious implications for the structure and functioning of these fragile 'sentinel' ecosystems across multiple levels of organization. © 2009 Blackwell Publishing Ltd.

Antonsson T.,Institute of Freshwater Fisheries | Heidarsson T.,Husdyragardurinn in Reykjavik | Snorrason S.S.,University of Iceland
Transactions of the American Fisheries Society | Year: 2010

Atlantic salmon Salmo salar smolts were sampled at weirs from two Icelandic rivers (Ellidaár and Vesturdalsá) for a 15-year period to test four hypotheses: (1) longer smolts (i.e., at the high end of the length-frequency distribution) will have higher survival to adulthood than shorter smolts (i.e., in the middle and lower parts of the distribution); (2) plumper (i.e., higher condition factor) smolts will have higher survival to adulthood than leaner (slim or average) smolts; (3) middle-age smolts (i.e., in the middle part of the freshwater age distribution) will have higher survival rates than fish at the extremes of the age distribution; and (4) fish in the middle portion of the smolt run will have higher smolt-to-adult survival than smolts emigrating early and late. Among the three length-groups, significant differences were found in smolt-to-adult survival in each river. In pairwise comparisons, long smolts had significantly higher survival rates than middle-sized and short smolts for both rivers. Among the three condition groups, significant differences were found in smolt-to-adult survival for the Ellidaár but not for the Vesturdalsá. Ages of smolts in the Ellidaár ranged from 1 to 5 years, and more than 98% of smolts were age 2-4. Smolts in the Vesturdalsá ranged in age from 2 to 7 years, and more than 99% of smolts were age 3-5. Among the dominant three age-groups for each river, significant differences were found in smolt-to-adult survival. Among the three migration timing groups, significant differences were found in smolt-to-adult survival in both rivers. In pairwise comparisons for the Ellidaár, late-migrating smolts had significantly higher survival rates than middle and early smolts. In the Vesturdalsá, late-migrating smolts had significantly higher survival than early and middle smolts, which did not differ from each other. These results are placed in the context of optimization of life history strategies and ideas about the process of smoltification in Atlantic salmon life history. © by the American Fisheries Society 2010.

Granquist S.M.,Institute of Freshwater Fisheries | Granquist S.M.,Icelandic Seal Center | Granquist S.M.,University of Stockholm | Sigurjonsdottir H.,University of Iceland
Applied Animal Behaviour Science | Year: 2014

The effect of land-based seal watching on the haul-out pattern of harbour seals (Phoca vitulina) was investigated between June and August of 2008-2010 on Vatnsnes, NW Iceland. The results showed that the behaviour and spatial haul-out pattern of seals was affected by the tourists. In 2009 the seals were more likely to be vigilant during periods when tourists had access to the area, compared to a period when tourists were not allowed in the area. Also, in 2010 the likeliness of the seals being vigilant increased as the number of tourists in the area increased. In addition, seals were more likely to be vigilant when tourists behaved in an active way. During the post weaning period, which coincided with the peak of the tourist season, a significantly higher proportion of seals hauled out on the skerry located farthest away from land, compared to a skerry closer to land. Seals also preferred to haul out further away from land when the number of tourists in the area increased. Single tourists and couples behaved more passively compared to families and tourist groups of more than two adults. All tourist group types were significantly more active in an approaching zone than in the seal watching zone. Education of tourists, for example through a code of conduct built on these results, is advisable to minimise disturbance of seals in the area. © 2014 Elsevier B.V.

Agency: GTR | Branch: NERC | Program: | Phase: Research Grant | Award Amount: 1.82M | Year: 2015

The impacts of climate change, and warming in particular, on natural ecosystems remain poorly understood, and research to date has focused on individual species (e.g. range shifts of polar bears). Multispecies systems (food webs, ecosystems), however, can possess emergent properties that can only be understood using a system-level perspective. Within a given food web, the microbial world is the engine that drives key ecosystem processes, biogeochemical cycles (e.g. the carbon-cycle) and network properties, but has been hidden from view due to difficulties with identifying which microbes are present and what they are doing. The recent revolution in Next Generation Sequencing has removed this bottleneck and we can now open the microbial black box to characterise the metagenome (who is there?) and metatranscriptome (what are they doing?) of the community for the first time. These advances will allow us to address a key overarching question: should we expect a global response to global warming? There are bodies of theory that suggest this might be the case, including the Metabolic Theory of Ecology and the Everything is Everywhere hypothesis of global microbial biogeography, yet these ideas have yet to be tested rigorously at appropriate scales and in appropriate experimental contexts that allow us to identify patterns and causal relationships in real multispecies systems. We will assess the impacts of warming across multiple levels of biological organisation, from genes to food webs and whole ecosystems, using geothermally warmed freshwaters in 5 high-latitude regions (Svalbard, Iceland, Greenland, Alaska, Kamchatka), where warming is predicted to be especially rapid,. Our study will be the first to characterise the impacts of climate change on multispecies systems at such an unprecedented scale. Surveys of these sentinel systems will be complemented with modelling and experiments conducted in these field sites, as well as in 100s of large-scale mesocosms (artificial streams and ponds) in the field and 1,000s of microcosms of robotically-assembled microbial communities in the laboratory. Our novel genes-to-ecosystems approach will allow us to integrate measures of biodiversity and ecosystem functioning. For instance, we will quantify key functional genes as well as quantifying which genes are switched on (the metatranscriptome) in addition to measuring ecosystem functioning (e.g. processes related to the carbon cycle). We will also measure the impacts of climate change on the complex networks of interacting species we find in nature - what Darwin called the entangled bank - because food webs and other types of networks can produce counterintuitive responses that cannot be predicted from studying species in isolation. One general objective is to assess the scope for biodiversity insurance and resilience of natural systems in the face of climate change. We will combine our intercontinental surveys with natural experiments, bioassays, manipulations and mathematical models to do this. For instance, we will characterise how temperature-mediated losses to biodiversity can compromise key functional attributes of the gene pool and of the ecosystem as a whole. There is an assumption in the academic literature and in policy that freshwater ecosystems are relatively resilient because the apparently huge scope for functional redundancy could allow for compensation for species loss in the face of climate change. However, this has not been quantified empirically in natural systems, and errors in estimating the magnitude of functional redundancy could have substantial environmental and economic repercussions. The research will address a set of key specific questions and hypotheses within our 5 themed Workpackages, of broad significance to both pure and applied ecology, and which also combine to provide a more holistic perspective than has ever been attempted previously.

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