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  • 151.
    Eklöv, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    VanKooten, Tobias
    Facilitation among piscivorous predators: effects of prey habitat use2001In: Ecology, ISSN 0012-9658, Vol. 82, no 9, p. 2486-2494Article in journal (Refereed)
    Abstract [en]

    The combined effects of predators on prey may substantially differ from thatof each predator species alone because of alterations in prey behavior. Using enclosures within a pond, we examined experimentally the effects of two piscivorous predators on prey mortality and prey resource levels in two habitats. The two predators use two different foraging modes, which also allowed us to examine the behaviorally induced indirect effects of prey on predator growth and prey food resources. Both perch (Perca fluviatilis) and pike (Esox lucius) caused significant mortality of roach (Rutilus rutilus), and the combined predator mortality was higher than predicted from a multiplicative prey consumption model. Growth rates of perch were similar when enclosures contained only perch and when they contained perch combined with pike. The growth rate of pike was higher when they were together with perch compared to when alone. Growth of roach was similar among treatments. The invertebrate food resources of roach increased by a factor 10 in the open water but remained at similar levels throughout the experiment in the vegetation. Biomass of Daphnia longispina, the dominant zooplankton species in the open water, was strongly correlated with mortality of roach, indicating a density-mediated indirect effect of predators on prey resources. There was no indirect effect on D. longispina in the vegetation caused by habitat restriction of roach and only a weak relationship in the open water. There was a strong indirect effect of pike predation on macroinvertebrates induced by a habitat shift of roach. Our results suggest that there was facilitation between predators caused by conflicting antipredator behavior of roach, which resulted in density-mediated indirect effects on prey resources. The behavioral response of roach to the two predators also induced indirect effects on invertebrate prey.

     

     

  • 152.
    Eklöv, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Werner, Earl
    Multiple predator effects on size-dependent behavior and mortality of twospecies of anuran larvae2000In: OIKOS, Vol. 88, no 2, p. 250-258Article in journal (Refereed)
    Abstract [en]

    This study examined the effects of multiple predators on size-specific behavior and mortality of two species of anuran larvae. Particularly. we focused on how trail changes in predators and prey may be transmitted to other species in the food web. In labo

  • 153. Elliott, J.A.
    et al.
    Persson, Irina
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Thackeray, S.J.
    Blenckner, Thorsten
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Phytoplankton modelling of Lake Erken, Sweden by linking the models PROBE and PROTECH2007In: Ecological Modelling, ISSN 0304-3800, E-ISSN 1872-7026, Vol. 202, no 3-4, p. 421-426Article in journal (Refereed)
    Abstract [en]

    A phytoplankton community model (PROTECH) and a lake physical model (PROBE) were linked, for the first time, to simulate the phytoplankton community of Lake Erken (Sweden). This allowed the physical effects of ice formation to be incorporated into the calculations of PROTECH. This is the highest latitude lake simulated by PROTECH thus far and was a further test of its biological application to lake ecosystems in general. A new cyanobacteria species was added to the PROTECH model: Gloeotrichia echinulata (Smith) Richter which had functional characteristics never before simulated in PROTECH and was an order of magnitude larger than species previously simulated. The biological outputs of total chlorophyll a were successfully validated against quantitative observations from the lake (EF = 0.76). The addition of G. echinulata to the model notably improved this fit, particularly in the period from July to October. Key taxa biomass were also simulated, with good fits for diatoms (EF = 0.70) and cyanobacteria (EF = 0.83). Furthermore, the characteristic periodic blooms of Gloeotrichia were captured, thus supporting its assigned model parameters and suggesting that PROTECH's growth equations can be applied to this significantly larger species. Furthermore, it appears that Gloeotrichia's simulated seasonal pattern of growth was greatly dependent upon the water temperature.

  • 154. Engström-Öst, Jonna
    et al.
    Candolin, Ulrika
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Human induced water turbidity alters selection on sexual displays in sticklebacks2007In: Behavioral Ecology, ISSN 1045-2249, E-ISSN 1465-7279, Vol. 18, no 2, p. 393-398Article in journal (Refereed)
    Abstract [en]

    Changes in the environment due to human activities are becoming increasingly common. A serious problem in aquatic environments is increased water turbidity due to phytoplankton algal growth. This may affect the breeding system of fishes, especially those with a visually based mating system. Here we show that increased turbidity affects sexual selection in the threespine stickleback (Gasterosteus aculeatus) through impaired possibility for visually based mate choice. In a laboratory mate preference and mate choice experiment on sticklebacks from the Baltic Sea, which is an area suffering from increased turbidity due to human activities, we found that females spent more time with and visited more often males in clear water than males in turbid water. For males in turbid water to receive the same amount of interest from females as males in clear water, they needed to court significantly more. Thus, turbid water induced selection for higher courtship activity. However, the final spawning decision of the females did not depend on water turbidity, which suggests that nonvisual cues determined the final spawning decision. Because visual cues are important in mate attraction, increased turbidity affects an important evolutionary force, sexual selection, which may have further consequences for the evolution of the sexual displays and preferences. Differences in visual conditions could hence be one factor that has lead to differences among stickleback population in the use of sexual signals.

  • 155. Engström-Öst, Jonna
    et al.
    Immonen, Emmi
    Candolin, Ulrika
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Mattila, Johanna
    The indirect effects of eutrophication on habitat choice and survival of fish larvae in the Baltic Sea2007In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 151, no 1, p. 393-400Article in journal (Refereed)
    Abstract [en]

    The structure of the habitat is usually crucial for growth and survival of young life stages. Presently, some nursery areas of fish larvae are changing due to eutrophication, e.g. due to enhanced growth of ephemeral filamentous algae at the expense of perennial species. We studied the influence of two habitats, one with filamentous algae (Cladophora glomerata) and the other with bladder wrack (Fucus vesiculosus), on habitat choice of pike larvae (Esox lucius) in the absence/presence of a predator or a competitor. We further tested whether the habitat choice is adaptive in increasing survival under predation threat. In contrast to expectations, pike larvae preferred the habitat with ephemeral filamentous algae to the bladder wrack, thriving in clean waters, independent of the presence/absence of both predator/competitor. In addition, the survival of the larvae was higher in the filamentous algae in the presence of predators, which suggested that the habitat preference of the larvae was adaptive. The structure of the bladderwrack habitat was probably too open for newly hatched larvae, which implies that F. vesiculosus and other large brown algae are not as important refuges for young larvae as previously thought.

  • 156. Enwall, Karin
    et al.
    Nyberg, Karin
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Stenström, John
    Hallin, Sara
    Long-Term impact of fertilization on activity and composition of bacterial communities and metabolic guilds in agricultural soil2007In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 39, no 1, p. 106-115Article in journal (Refereed)
    Abstract [en]

    To explore long-term impact of organic and inorganic fertilizers on microbial communities, we targeted both the total bacterial community and the autotrophic ammonia oxidizing bacteria (AOB) in soil from six treatments at an experimental field site established in 1956: cattle manure, sewage sludge, Ca(NO3)2, (NH4)2SO4, unfertilized and unfertilized without crops. All plots, except the bare fallows, were cropped with maize. Effects on activity were assessed by measuring the basal respiration and substrate induced respiration (SIR) rates, and the potential activity of the AOB. To determine the bacterial community composition, 16S rRNA genes were used to fingerprint total soil communities by terminal restriction fragment length polymorphism analysis and AOB communities by denaturing gradient gel electrophoresis. The fertilization regimes had clear effects on both activity and composition of the soil communities. Basal respiration and r, which was kinetically derived as the exponentially growing fraction of the SIR-response, correlated well with the soil organic C content (r=0.93 and 0.66, respectively). Soil pH ranged from 3.97 to 6.26 in the treatments and was found to be an important factor influencing all microbial activities. pH correlated negatively with the ratio between basal respiration and SIR (r=0.90), indicating a decreased efficiency of heterotrophic microorganisms to convert organic carbon into microbial biomass in the most acid soils with pH 3.97 and 4.68 ((NH4)2SO4 and sewage sludge fertilized plots, respectively). The lowest SIR and ammonia oxidation rates were also found in these treatments. In addition, these treatments exhibited individually different community fingerprints, showing that pH affected the composition of AOB and total bacterial communities. The manure fertilized plots harbored the most diverse AOB community and the pattern was linked to a high potential ammonia oxidation activity. Thus, the AOB community composition appeared to be more strongly linked to the activity than the total bacterial communities were, likely explained by physiological differences in the populations present.

  • 157.
    Fischer, H.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Limnology.
    The role of biofilms in the uptake and transformation of dissolved organic matter2003In: Aquatic ecosystems: interactivity of dissolved organic matter, 2003, p. 285-313Chapter in book (Refereed)
  • 158.
    Fischer H, Sukhodolov A. , Wilczek S., Engelhardt C.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Limnology.
    Effects of flow dynamics and sediment movement on microbial activity in a lowland river2003In: River Research and Applications, Vol. 19, p. 473-482Article in journal (Refereed)
  • 159.
    Fischer, Helmut
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Bergfur, Jenny
    Goedkoop, Willem
    Tranvik, Lars J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Microbial leaf degraders in boreal streams: bringing together stochastic and deterministic regulators of community composition2009In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 54, no 11, p. 2276-2289Article in journal (Refereed)
    Abstract [en]

    Leaves that fall into the water represent a new habitat for microorganisms to colonise in streams, providing an opportunity to study colonisation and the subsequent regulation of community structure. We explored community composition of bacteria and fungi on decomposing alder leaves in nine streams in central Sweden, and describe their relationship with environmental variables. Succession of the microbial community was studied in one of the streams for 118 days. Microbial community composition was examined by denaturing gradient gel electrophoresis on replicate samples of leaves from each stream. 2. During succession in one stream, maximum taxon richness was reached after 34 days for bacteria and 20 days for fungi respectively. Replicate samples within this stream differed between each other earlier in colonisation, while subsequently such variation among replicate communities was low and remained stable for several weeks. Replicate samples taken from all the nine streams after 34 days of succession showed striking similarities in microbial communities within-streams, although communities differed more strongly between streams. 3. Canonical analysis of microbial communities and environmental variables revealed that water chemistry had a significant influence on community composition. This influence was superimposed on a statistical relationship between the properties of stream catchments and microbial community composition. 4. The catchment regulates microbial communities in two different ways. It harbours the species pool from which the in-stream microbial community is drawn and it governs stream chemistry and the composition of organic substrates that further shape the communities. We suggest that there is a random element to colonisation early in succession, whereas other factors such as species interactions, stream chemistry and organic substrate properties, result in a more deterministic regulation of communities during later stages.

  • 160.
    Fischer, Helmut
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Federal Institute of Hydrology, Am Mainzer Tor 1, 56068 Koblenz, Germany.
    Mille-Lindblom, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Zwirnmann, Elke
    Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 301, 12587 Berlin, Germany.
    Tranvik, Lars J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Contribution of fungi and bacteria to the formation of dissolved organic carbon from decaying common reed (Phragmites australis)2006In: Archiv für Hydrobiologie, ISSN 0003-9136, Vol. 166, no 1, p. 79-97Article in journal (Refereed)
    Abstract [en]

    We examined release and subsequent utilization of DOC from leaves of common reed (Phragmites australis), a macrophyte which often dominates in shallow lakes and constitutes an important source of dissolved organic carbon (DOC). Leaves were incubated submersed in organic-free water for up to 63 days with natural and manipulated microbial communities. By this, we aimed to demonstrate differential effects of bacteria and fungi on the composition and amount of DOC originating from the leaves. DOC was analyzed by its total amount, spectral properties at wavelengths of 250-500 nm and its composition determined by size exclusion chromatography followed by organic carbon detection. Leaching of DOC was fast and the maximum DOC concentration was reached after 48 h. Mean molecule size increased during the first 14 days of incubation. Later on, humic-like substances accumulated, whereas low- and high-molecular-weight DOC were depleted. The formation of DOC from leaf detritus was strongly influenced by the composition of the microbial community present. Bacteria effectively removed low-molecular-weight DOC and accumulated high-molecular-weight DOC during a 7 day incubation. Leaf-degrading fungi promoted the accumulation of high amounts of intermediate-molecular-weight DOC, but were suppressed by the presence of bacteria. The presence of bacteria and/or fungi thus resulted in contrasting patterns of DOC composition, suggesting functional differences and strong interactions between those two major microbial groups during natural decomposition of leaves. The activity and interactions of both groups may therefore be significant for DOC composition in aquatic systems.

  • 161.
    Forsberg C., Savchuck O.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Limnology.
    A new regime for nutrient turnover – Eutrophication2003In: ), Environmental Sciences. Understanding, protecting, and managing the environment in the Baltic Sea region, 2003, p. 256-293Chapter in book (Refereed)
  • 162. Frost,, P.C.,
    et al.
    Hillebrand,, H.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Limnologi.
    Kahlert, M.
    Low algal carbon content and its effect on the C : P stoichiometry of periphyton.2005In: Freshwater Bioliology, no 50:, p. 1800 1807-Article in journal (Refereed)
  • 163. Fölster, Jens
    et al.
    Andrén, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Bishop, Kevin
    Buffam, Ishi
    Cory, Neil
    Goedkoop, Willem
    Holmgren, Kerstin
    Johnson, Richard
    Laudon, Hjalmar
    Wilander, Anders
    A Novel Environmental Quality Criterion for Acidification in Swedish Lakes – An Application of Studies on the Relationship Between Biota and Water Chemistry2007In: Water, Air, & Soil Pollution: Focus, ISSN 1567-7230, Vol. 7, no 1-3, p. 331-338Article in journal (Refereed)
    Abstract [en]

    The recovery from acidification has led to the demand for more precise criteria for classification of acidification. The Swedish Environmental Protection Agency has revised Sweden’s Ecological Quality Criteria for acidification to improve the correlation between the chemical acidification criteria and biological effects. This paper summarises the most relevant findings from several of the studies commissioned for this revision. The studies included data on water chemistry in 74 reference lakes in southern Sweden with data on fish in 61 of the lakes, as well as data on littoral fauna in 48 lakes. We found that the acidity variable most strongly correlated to the biota was the median pH from the current year. Our results probably do not reflect the mechanisms behind the negative effects of acidity on the biota, but are fully relevant for evaluation of monitoring data. The biogeochemical models used for predicting acidification reference conditions generate a pre-industrial buffering capacity. In order to get an ecologically more relevant criteria for acidification based on pH, we transferred the estimated change in buffering capacity into a corresponding change in pH. A change of 0.4 units was defined as the threshold for acidification. With this criterion a considerably lower number of Swedish lakes were classified as acidified when compared with the present Ecological Quality Criteria.

  • 164. Gasol, Josep M.
    et al.
    Pinhassi, Jarone
    Alonso-Sáez, Laura
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Ducklow, Hugh
    Herndl, Gerhard J.
    Koblizek, Michal
    Labrenz, Matthias
    Luo, Yawei
    Morán, Xosé Anxelu G.
    Reinthaler, Thomas
    Simon, Meinhard
    Towards a better understanding of microbial carbon flux in the sea2008In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 53, no 1, p. 21-38Article in journal (Refereed)
    Abstract [en]

    We now have a relatively good idea of how bulk microbial processes shape the cycling of organic matter and nutrients in the sea. The advent of the molecular biology era in microbial ecology has resulted in advanced knowledge about the diversity of marine microorganisms, suggesting that we might have reached a high level of understanding of carbon fluxes in the oceans. However, it is becoming increasingly clear that there are large gaps in the understanding of the role of bacteria in regulating carbon fluxes. These gaps may result from methodological as well as conceptual limitations. For example, should bacterial production be measured in the light? Can bacterial production conversion factors be predicted, and how are they affected by loss of tracers through respiration? Is it true that respiration is relatively constant compared to production? How can accurate measures of bacterial growth efficiency be obtained? In this paper, we discuss whether such questions could (or should) be addressed. Ongoing genome analyses are rapidly widening our understanding of possible metabolic pathways and cellular adaptations used by marine bacteria in their quest for resources and struggle for survival (e.g. utilization of light, acquisition of nutrients, predator avoidance, etc.). Further, analyses of the identity of bacteria using molecular markers (e.g. subgroups of Bacteria and Archaea) combined with activity tracers might bring knowledge to a higher level. Since bacterial growth (and thereby consumption of DOC and inorganic nutrients) is likely regulated differently in different bacteria, it will be critical to learn about the life strategies of the key bacterial species to achieve a comprehensive understanding of bacterial regulation of C fluxes. Finally, some processes known to occur in the microbial food web are hardly ever characterized and are not represented in current food web models. We discuss these issues and offer specific comments and advice for future research agendas.

  • 165.
    Gebre-Mariam, Zinabu
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Limnologi.
    Pearce, NJG
    Ahlgren, Ingemar
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Limnologi.
    Toxic metals and related trace elements in some Ethiopian hot springs.2004In: Ethiop. J. Biol. Sci., p. 69-80Article in journal (Refereed)
  • 166. Giardino, Claudia
    et al.
    Brando, Vittorio E.
    Dekker, Amold G.
    Strömbeck, Niklas
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Candiani, Gabriele
    Assessment of water quality in Lake Garda (Italy) using Hyperion2007In: Remote Sensing of Environment, ISSN 0034-4257, E-ISSN 1879-0704, Vol. 109, no 2, p. 183-195Article in journal (Refereed)
    Abstract [en]

    For testing the integration of the remote sensing related technologies into the water quality monitoring programs of Lake Garda (the largest Italian lake), the spatial and spectral resolutions of Hyperion and the capability of physics-based approaches were considered highly suitable. Hyperion data were acquired on 22nd July 2003 and water quality was assessed (i) defining a bio-optical model, (ii) converting the Hyperion atsensor radiances into subsurface irradiance reflectances, and (iii) adopting a bio-optical model inversion technique. The bio-optical model was parameterised using specific inherent optical properties of the lake and light field variables derived from a radiative transfer numerical model. A MODTRAN-based atmospheric correction code, complemented with an air/water interface correction was used to convert Hyperion at-sensor radiances into subsurface irradiance reflectance values. These reflectance values were comparable to in situ reflectance spectra measured during the Hyperion overpass, except at longer wavelengths (beyond 700 nm), where reflectance values were contaminated by severe atmospheric adjacency effects. Chlorophyll-a and tripton concentrations were retrieved by inverting two Hyperion bands selected using a sensitivity analysis applied to the bio-optical model. The sensitivity analysis indicated that the assessment of coloured dissolved organic matter was not achievable in this study due to the limited coloured dissolved organic matter concentration range of the lake, resulting in reflectance differences below the environmental measurement noise of Hyperion. The chlorophyll-a and tripton image-products were compared to in situ data collected during the Hyperion overpass, both by traditional sampling techniques (8 points) and by continuous flow-through systems (32 km). For chlorophyll-a the correlation coefficient between in situ point stations and Hyperion-inferred concentrations was 0.77 (data range from 1.30 to 2.16 mg m(-3)). The Hyperion-derived chlorophyll-a concentrations also match most of the flow-through transect data. For tripton, the validation was constrained by variable re-suspension phenomena. The correlation coefficient between in situ point stations and Hyperion-derived concentrations increased from 0.48 to 0.75 (data range from 0.95 to 2.13 g m(-3)) if the sampling data from the re-suspension zone was avoided. The comparison of Hyperionderived tripton concentrations and flow-through transect data exhibited a similar mismatch. The results of this research suggest further studies to address compatibilities of validation methods for water body features with a high rate of change, and to reduce the contamination by atmospheric adjacency effects on Hyperion data at longer wavelengths in Alpine environment. The transferability of the presented method to other sensors and the ability to assess water quality independent from in situ water quality data, suggest that management relevant applications for Lake Garda (and other subalpine lakes) could be supported by remote sensing.

  • 167. Goedkoop, W.
    et al.
    Demandt, Marnie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
    Ahlgren, Gunnel
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Interactions between food quantity and quality (long-chain polyunsaturated fatty acid concentrations) effects on growth and development of Chironomus riparius2007In: Canadian Journal of Fisheries and Aquatic Sciences, ISSN 0706-652X, E-ISSN 1205-7533, Vol. 64, no 3, p. 425-436Article in journal (Refereed)
    Abstract [en]

    We quantified somatic growth, development, and emergence of the midge Chironomus riparius on experimental diets (oats, Spirulina, and Tetraphyll (R)) covering gradients in food quality (differing polyunsaturated fatty acids) and quantity (0.1-5.4 mg C center dot day(-1)). Additionally, similar incubations without food additions were made using a food-poor sediment containing peat and the green alga Scenedesmus obliquus. Larval and adult size was affected by both food quantity and quality and increased some three to four times across the food concentration gradients. Adult emergence, however, was affected only by food quantity. A type 3 response model showed that a saturation level was reached for the oats treatment at 2.7 mg C center dot day(-1) (or 3.9 mu g omega 3 and 120 mu g omega 6 polyunsaturated fatty acids center dot day(-1)), indicating that the quality of oats constrained further stimulation of larval growth. In the peat treatment, larval growth was very low, no adults emerged, and no larvae even made it to the pupa stage. Fatty acid analyses showed that larvae were capable of synthesizing arachidonic acid via gamma-linolenic acid by Delta 6- and Delta 5-desaturase activity using linoleic acid available in food sources. This strongly suggests that C. riparius is not dependent on dietary sources of eicosapentaenoic acid and arachidonic acid and can sustain viable populations even under a low-quality food regimen.

  • 168. Goedkoop,, W.
    et al.
    Widenfalk,, A.
    Haglund,, A-L.,
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Limnologi.
    Bertilsson, Stefan
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Limnologi.
    Microbial characterization of artificial sediment and comparisons with natural sediment-Implications for toxicity testing.2005In: Environmental Toxicology and Chemistry., no 24:, p. 2725-2733.Article in journal (Refereed)
  • 169.
    Goedkoop, Willem
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Limnology.
    Sonesten, Lars
    Ahlgren, Gunnel
    Department of Ecology and Evolution, Limnology. Limnologi.
    Boberg, M
    Department of Ecology and Evolution, Limnology.
    Fatty acids in profundal benthic invertebrates and their major food resources in Lake Erken, Sweden: seasonal variation and trophic indications2000In: Canadian Journal of Aquatic Fisheries and Sciences, Vol. 57, no 11, p. 2267-2279Article in journal (Refereed)
    Abstract [en]

    Fatty acid (FA) concentrations and their seasonal variations were quantified for profundal benthic invertebrates, surficial sediment, and sedimenting matter from Lake Erken, Sweden. Food quality for profundal zoobenthos, as indicated by the concentrations

  • 170.
    Goedkoop, Willem
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Limnology. Limnologi.
    Sonesten, Lars
    Markensten, Hampus
    Department of Ecology and Evolution, Limnology. Limnnologi.
    Ahlgren, Gunnel
    Department of Ecology and Evolution, Limnology. Limnologi.
    Fatty acid biomarkers show dietary differences between dominant chironomid taxa in Lake Erken1998In: FRESHWATER BIOLOGY, ISSN 0046-5070, Vol. 40, no 1, p. 135-143Article in journal (Refereed)
    Abstract [en]

    1. In this field study, diatom-specific and bacteria-specific fatty acids were used as biomarkers to evaluate the differences in diet between Chironomus plumosus (a spring-emerging cohort) and C. anthracinus (an autumn-emerging cohort), and Procladius spp

  • 171. Goldstone, J V
    et al.
    Pullin, M J
    Bertilsson, Stefan
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Limnologi.
    Voelker, B M
    Reactions of hydroxyl radical with humic substances: bleaching, mineralization, and production of bioavailable carbon substrates.2002In: Environ Sci Technol, ISSN 0013-936X, Vol. 36, no 3, p. 364-72Article in journal (Refereed)
  • 172.
    Granéli, Wilhelm
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Bertilsson, Stefan
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Limnologi.
    Philibert, A
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Phosphorus limitation of bacterial growth in high Arctic lakes and ponds2004In: Aquatic Sciences, Vol. 66, p. 430-439Article in journal (Refereed)
  • 173.
    Granéli, Wilhelm
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Carlsson, Per
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Bertilsson, Stefan
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Bacterial abundance, production and organic carbon limitation in the Southern Ocean (39-62°S, 4-14°E) during the austral summer 1997/19982004In: Deep-Sea Research II: Topical Studies in Oceanography, Vol. 51, p. 2569-2582Article in journal (Refereed)
  • 174. Grzybowski, W.
    et al.
    Tranvik, L.J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Phototransformations of dissolved organic nitrogen.2008In: Nitrogen in the Marine Environment., 2008, 2, p. 511-528Chapter in book (Other (popular science, discussion, etc.))
  • 175.
    Gudasz, Cristian
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Bastviken, David
    Steger, Kristin
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Premke, Katrin
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Sobek, Sebastian
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Tranvik, Lars J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Temperature-controlled organic carbon mineralization in lake sediments2010In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 466, no 7305, p. 478-481Article in journal (Refereed)
    Abstract [en]

    Peatlands, soils and the ocean floor are well-recognized as sites of organic carbonaccumulation andrepresentimportant global carbon sinks(1,2). Although the annual burial of organic carbon in lakes and reservoirs exceeds that of ocean sediments(3), these inland waters are components of the global carbon cycle that receive only limited attention(4-6). Of the organic carbon that is being deposited onto the sediments, a certain proportion will be mineralized and the remainder will be buried over geological timescales. Here we assess the relationship between sediment organic carbon mineralization and temperature in a cross-system survey of boreal lakes in Sweden, and with input froma compilation of published data from awide range of lakes that differ with respect to climate, productivity and organic carbon source. We find that the mineralization of organic carbon in lake sediments exhibits a strongly positive relationship with temperature, which suggests that warmer water temperatures lead to more mineralization and less organic carbon burial. Assuming that future organic carbon delivery to the lake sediments will be similar to that under present-day conditions, we estimate that temperature increases following the latest scenarios presented by the Intergovernmental Panel on Climate Change(7) could result in a 4-27 per cent (0.9-6.4 Tg Cyr(-1)) decrease in annual organic carbon burial in boreal lakes.

  • 176. Guimarães, Jean R.D.
    et al.
    Mauro, Jane B.N.
    Meili, Markus
    Sundbom, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Haglund, Anne-Louise
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Coelho-Souza, S.A.
    Hylander, Lars D.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Simultaneous radioassays of bacterial production and mercury methylation in the periphyton of a tropical and a temperate wetland2006In: Journal of Environmental Management, ISSN 0301-4797, E-ISSN 1095-8630, Vol. 81, no 2, p. 95-100Article in journal (Refereed)
    Abstract [en]

    Laboratory radioassays were made to study mercury (Hg) methylation together with bacterial production in the periphyton of two aquatic macrophytes, the submerged Myriophyllum spicatum, from a constructed wetland in Sweden and the floating Eichhornia crassipes, from a eutrophied tropical lake in Brazil. Time course incubations were made by addition of 203HgCl2 and the methylmercury formed was extracted at pre-defined time intervals. Bacterial production (14C-leucine incorporation) was measured at the same time intervals, with plants removed from parallel incubations made with and without addition of cold HgCl2. For E. crassipes, higher methylmercury production was observed at elevated bacterial production, whereas for M. spicatum, the bacterial production was significantly lower, and Hg methylation was below the detection limit. The combined results confirm the importance of microbial processes for Hg methylation, although other factors are known to influence this process in complex ways. The addition of Hg did not significantly influence bacterial production, while the incubation temperatures used (25 and 35 1C) resulted in different methylation rates.

    Radiotracer techniques for measurements of bacterial production such as 14C-leucine uptake can provide useful insights into the Hg cycle in aquatic environments, and our data suggest that they may be used as a proxy of mercury methylation potentials.

  • 177. Gustafsson, Kerstin
    et al.
    Blidberg, Eva
    Karlsson Elfgren, Irene
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Hellström, Anna
    Kylin, Henrik
    Gorokhova, Elena
    Direct and indirect effects of the fungicide azoxystrobin in outdoor brackish water microcosms2010In: Ecotoxicology, ISSN 0963-9292, E-ISSN 1573-3017, Vol. 19, no 2, p. 431-444Article in journal (Refereed)
    Abstract [en]

    The effects of the strobilurin fungicide azoxystrobin were studied in brackish water microcosms, with natural plankton communities and sediment. Two experiments were conducted: Experiment 1 (nominal conc. 0, 15 and 60 mu g/L, 24-L outdoor microcosms for 21 days) and a second, follow-up, Experiment 2 (nominal conc. 0, 3, 7.5, 15 mu g/L, 4-L indoor microcosms for 12 days). The microcosms represent a simplified brackish water community found in shallow semi-enclosed coastal areas in agricultural districts in the Baltic Sea region. Measured water concentrations of the fungicide (Experiment 1) were, on average, 83 and 62% of nominal concentrations directly after application, and 25 and 30% after 21 days, for the low and high dose treatments, respectively, corresponding to mean DT50-values of 15.1 and 25.8 days, for low and high dose treatments, respectively. In Experiment 1, direct toxic effects on calanoid copepods at both test concentrations were observed. Similarly, in Experiment 2, the copepod abundance was significantly reduced at all tested concentrations. There were also significant secondary effects on zooplankton and phytoplankton community structure, standing stocks and primary production. Very few ecotoxicological studies have investigated effects of plant protection products on Baltic organisms in general and effects on community structure and function specifically. Our results show that azoxystrobin is toxic to brackish water copepods at considerably lower concentrations than previously reported from single species tests on freshwater crustaceans, and that direct toxic effects on this ecologically important group may lead to cascade effects altering lower food webs and ecosystem functioning.

  • 178.
    Gücker B, Fischer H.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Limnology.
    Flagellates and ciliates in sediments of a lowland river: Taxonomy, spatial distribution, and potential role in the microbial food web2003In: Microbial Ecology, Vol. 31, p. 67-76Article in journal (Refereed)
  • 179.
    Haglund, A.-L.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Lantz, P.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Törnblom, E.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Tranvik, L. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Depth distibution of active bacteria and bacterial activity in lake sediment2003In: FEMS Microbiology Ecology, Vol. 46, p. 31-38Article in journal (Refereed)
  • 180.
    Haglund, A-L.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Törnblom, E
    Boström, B
    Tranvik, L J
    Large differences in the active fraction of bacteria in plankton, sediments, and epiphytic biofilms.2002In: Microbial Ecology, Vol. 43, p. 232-241.Article in journal (Refereed)
  • 181.
    Haglund, Ann-Louise
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Attached Bacterial Communities in Lakes – Habitat-Specific Differences2004Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    For many years, the importance of microorganisms attached to surfaces in littoral zones and wetlands has been disregarded when describing aquatic ecosystem dynamics. Supporting evidence is scarce but convincing that these microbial communities are not only very productive but can often serve as major regulators of nutrient and carbon dynamics in many freshwaters. In order to determine the quantitative importance of epiphytic bacteria for the overall carbon turnover, I compared the relative contribution of epiphytic bacteria on the submerged macrophyte Ranunculus circinatus, sediment and free-living bacteria to the total bacterial production. Sediment bacteria generally dominated total bacterial biomass in the littoral zone. Although the epiphytic biomass on R. circinatus was ten times lower than the biomass of sediment bacteria, it often contributed at least equally to the total bacterial production. Thus, the results presented in this thesis confirm that most bacterial biomass and production in shallow lakes is associated with surfaces, and that in littoral zones with dense macrophyte stands, epiphytic bacteria can contribute significantly to the overall carbon turnover.

    There is increasing evidence that not all cells in natural bacterial communities are metabolically active. In Lake Erken, there were large differences in the fraction of active bacteria between different habitats, while the within-habitat differences were small. The sediments had the largest bacterial fraction, followed by epiphytic bacteria, while in the water column only a few percent of the bacteria were active. In this thesis the fraction of active bacteria is connected to environmental fluctuations. I hypothesize that smaller fluctuations in chemical, biological or physical factors result in large active bacterial fractions. Thus, small environmental fluctuations within a habitat allow large active bacterial fractions, while the active fraction is constrained when the environmental fluctuations are large.

    List of papers
    1. Quantitative importance of epiphytic versus sediment and planktonic bacteria for the overall carbon turnover in littoral zones
    Open this publication in new window or tab >>Quantitative importance of epiphytic versus sediment and planktonic bacteria for the overall carbon turnover in littoral zones
    (English)Article in journal (Refereed) Submitted
    Identifiers
    urn:nbn:se:uu:diva-92273 (URN)
    Available from: 2004-10-28 Created: 2004-10-28 Last updated: 2009-03-30Bibliographically approved
    2. Large differences in the fraction of active bacteria in plankton, sediments, and biofilm
    Open this publication in new window or tab >>Large differences in the fraction of active bacteria in plankton, sediments, and biofilm
    2002 (English)In: Microbial Ecology, ISSN 0095-3628, Vol. 43, p. 232-241Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-92274 (URN)
    Available from: 2004-10-28 Created: 2004-10-28 Last updated: 2017-11-30Bibliographically approved
    3. Depth distribution of active bacteria and bacterial activity in lake sediment
    Open this publication in new window or tab >>Depth distribution of active bacteria and bacterial activity in lake sediment
    2003 (English)In: FEMS Microbiology Ecology, ISSN 0168-6496, Vol. 46, p. 31-38Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-92275 (URN)
    Available from: 2004-10-28 Created: 2004-10-28 Last updated: 2017-11-30Bibliographically approved
    4. The effect of grazing and nutrient supply on periphyton associated bacteria
    Open this publication in new window or tab >>The effect of grazing and nutrient supply on periphyton associated bacteria
    2006 (English)In: FEMS Microbiology Ecology, ISSN 0168-6496, E-ISSN 1574-6941, Vol. 52, no 1, p. 31-41Article in journal (Refereed) Published
    Abstract [en]

    The effects of nutrient additions and grazing by macro-invertebrates on periphyton-associated algae and bacteria were studied by performing an enclosure experiment on three occasions from early spring to summer at mesotrophic Lake Erken and Väddö, at the Swedish Baltic coast. There were significant interactions between nutrient additions and grazing on bacterial biomass and specific activity in Lake Erken. Thus, the importance of either bottom-up or top-down effects could not be singled out. Bacterial biomass increased with enrichment only in the absence of grazers. Grazer presence tended to increase bacterial biomass in ambient nutrient conditions, but to decrease bacterial biomass under enrichment. For specific activity the positive response to enrichment was restricted to grazer presence. Hence, grazing by macro-invertebrates may have an indirect positive effect on bacterial activity by enhancing nutrient conditions through their feeding activities and/or fecal pellets production. In addition, we found a significant relationship between bacterial production and chlorophyll a at both sites. This relationship weakened in the presence of macro-invertebrates. Thus, the importance of internal nutrient regeneration by bacteria and algae decreased, possibly due to increased nutrient availability, in the presence of macro-invertebrate grazers.

    Keywords
    Periphyton, Bacterium, Nutrient regeneration, Grazing, Metabolically active bacterium, Cell-specific activity
    National Category
    Biological Sciences
    Identifiers
    urn:nbn:se:uu:diva-92276 (URN)10.1016/j.femsec.2004.10.003 (DOI)16329890 (PubMedID)
    Available from: 2004-10-28 Created: 2004-10-28 Last updated: 2017-12-14Bibliographically approved
  • 182.
    Haglund, Ann-Louise
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Hillebrand, Helmut
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    The effect of grazing and nutrient supply on periphyton associated bacteria2006In: FEMS Microbiology Ecology, ISSN 0168-6496, E-ISSN 1574-6941, Vol. 52, no 1, p. 31-41Article in journal (Refereed)
    Abstract [en]

    The effects of nutrient additions and grazing by macro-invertebrates on periphyton-associated algae and bacteria were studied by performing an enclosure experiment on three occasions from early spring to summer at mesotrophic Lake Erken and Väddö, at the Swedish Baltic coast. There were significant interactions between nutrient additions and grazing on bacterial biomass and specific activity in Lake Erken. Thus, the importance of either bottom-up or top-down effects could not be singled out. Bacterial biomass increased with enrichment only in the absence of grazers. Grazer presence tended to increase bacterial biomass in ambient nutrient conditions, but to decrease bacterial biomass under enrichment. For specific activity the positive response to enrichment was restricted to grazer presence. Hence, grazing by macro-invertebrates may have an indirect positive effect on bacterial activity by enhancing nutrient conditions through their feeding activities and/or fecal pellets production. In addition, we found a significant relationship between bacterial production and chlorophyll a at both sites. This relationship weakened in the presence of macro-invertebrates. Thus, the importance of internal nutrient regeneration by bacteria and algae decreased, possibly due to increased nutrient availability, in the presence of macro-invertebrate grazers.

  • 183.
    Haglund, Ann-Louise
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Lantz, Peter
    Törnblom, Erik
    Tranvik, Lars
    Depth distribution of active bacteria and bacterial activity in lake sediment2003In: FEMS Microbiology Ecology, ISSN 0168-6496, Vol. 46, p. 31-38Article in journal (Refereed)
  • 184.
    Haglund, Ann-Louise
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Törnblom, Erik
    Boström, Bengt
    Quantitative importance of epiphytic versus sediment and planktonic bacteria for the overall carbon turnover in littoral zonesArticle in journal (Refereed)
  • 185.
    Haglund, Ann-Louise
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Törnblom, Erik
    Boström, Bengt
    Tranvik, Lars
    Large differences in the fraction of active bacteria in plankton, sediments, and biofilm2002In: Microbial Ecology, ISSN 0095-3628, Vol. 43, p. 232-241Article in journal (Refereed)
  • 186.
    Hansson, L.-A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Tranvik, L. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Food webs in sub-Antarctic lakes: a stable isotope approach2003In: Polar Biology, Vol. 26, p. 783-788Article in journal (Refereed)
  • 187. Hessen, Dag O.
    et al.
    Blomqvist, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Dahl-Hansen, Geir
    Drakare, Stina
    Limnologi. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Lindström, Eva S.
    Limnologi. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Production and food web interactions of Arctic freshwater plankton and responses to increased DOC2004In: Archiv für Hydrobiologie, ISSN 0003-9136, Vol. 159, no 3, p. 289-307Article in journal (Refereed)
    Abstract [en]

    A gradient of dissolved organic carbon (DOC) was added to enclosures in a high Arctic lake (Svalbard, 79 N). The aim was to simulate the effect of increased concentrations of DOC that will be a predicted effect of increased temperature and precipitation. The study aimed to provide information on the overall effects of such increased levels of DOC on the pelagic food-web, as well as the increased attenuation of UV-radiation (UV-R) caused by increased DOC. The biomass development of phytoplankton, heterotrophic bacteria and ciliates from 15. July (shortly after ice-off) to 8. August revealed a consistent pattern across all enclosures. Initial phytoplankton biomass decreased from maxima around 600g Cl-1 towards 50g Cl-1 by the end of July. Similarly, ciliate biomass decreased from ~100 to 5g Cl-1, while heterotrophic bacteria decreased from initially 280 g Cl-1 to biomasses near 100 g Cl-1. Over the same period, zooplankton biomass (almost a monoculture of Daphnia tenebrosa) increased from <40 to some 170g Cl-1. These patterns were reflected also in decreasing absolute production of bacteria and phytoplankton, while production:biomass ratio remained fairly constant. In general, the study demonstrated a very dynamic system over the brief ice-free season, where Daphnia grazing had a strong impact on the unicellular biota. Additions of DOC initially stimulated planktonic production, yet this effect was soon overruled by Daphnia grazing. This stimulating effect could be a result both of increased UV-R attenuation and some growth stimulating effect. Since no corresponding stimulating effect was observed in the bag shielded with Mylar filter to screen off UV-B, the latter cause seems most likely.

  • 188.
    Heuschele, Jan
    et al.
    Department of Biological and Environmental Sciences, University of Helsinki.
    Candolin, Ulrika
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    An increase in pH boosts olfactory communication in sticklebacks2007In: Biology Letters, ISSN 1744-9561, E-ISSN 1744-957X, Vol. 3, no 4, p. 411-413Article in journal (Refereed)
    Abstract [en]

    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 male olfactory cues in mate choice in three-spined sticklebacks, Gasterosteus aculeatus. In a laboratory choice experiment, gravid females were more attracted to male olfactory cues when pH was raised. This could compensate for impaired visual communication in eutrophied waters and facilitate adaptive mate choice.

  • 189.
    Hillebrand, H. and Blenckner, T.,
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Regional and local impact on species diversity – from pattern to process.2002In: Oecologia, 132: 479-491.Article in journal (Refereed)
  • 190.
    Hillebrand, Helmut
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Diversity of unicellular aquatic organisms scaled to body size2002In: Verh. Internat. Ver. Limnol., Vol. 28, p. 352-354Article in journal (Refereed)
  • 191.
    Hillebrand, Helmut
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Top-down versus bottom-up control of autotrophic biomass -a meta analysis on experiments with perifyton2002In: J.N.Am.Bentol.Soc., Vol. 21, no 3, p. 349-369Article in journal (Refereed)
  • 192.
    Hillebrand, Helmut
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Azovsky, Andrey I.
    Body size determines the strength of the latitudinal diversity gradient2001In: Ecography, ISSN 0906-7590, Vol. 24, no 3, p. 251-256Article in journal (Refereed)
    Abstract [en]

    In most groups of organisms, the species richness decreases from the tropics to the poles. The mechanisms causing this latitudinal diversity gradient are still controversial. We present data from a comprehensive weighted meta-analysis on the strength of t

  • 193.
    Hillebrand, Helmut
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    DeMontpellier, Geraldine
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Liess, Antonia
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Effects of macrograzers and light on periphyton stoichiometry2004In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 106, no 1, p. 93-104Article in journal (Refereed)
    Abstract [en]

    Ecological stoichiometry describes the biochemical constraints of trophic interactions emerging from the different nutrient content and nutrient demand of producers and consumers, respectively. Most research on this topic originates from well-mixed pelagic food webs, whereas the idea has received far less attention in spatially structured habitats. Here, we test how light as well as grazing and nutrient regeneration by consumers affects growth and biomass of benthic primary producers. In the first laboratory experiment, we manipulated grazer presence (two different snail species plus ungrazed control), in the second experiment we factorially combined manipulation of grazer presence and light intensity. We monitored snail and periphyton biomass as well as dissolved and particulate nutrients (nitrogen and phosphorus) over time. Grazers significantly reduced algal biomass in both experiments. Grazers affected periphyton nutrient content depending on the prevailing nutrient limitation and their own body stoichiometry. In the nitrogen (N-) limited first experiment, grazers increased N both in the periphyton and in the water column. The effect was stronger for grazers with lower N-content. In the phosphorus (P-) limited second experiment, grazers increased the P-content of the periphyton, but the grazer with lower N-content had additionally positive effects on algal N. Light reduction did not affect periphyton biomass, but increased chlorophyll-, N- and P-content of the periphyton. These experiments revealed that the indirect effects of grazers on periphyton were bound by stoichiometric constraints of nutrient incorporation and excretion.

  • 194. Hillebrand, Helmut
    et al.
    Frost, Paul
    Liess, Antonia
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Ecological stoichiometry of indirect grazer effects on periphyton nutrient content2008In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 155, no 3, p. 619-630Article in journal (Refereed)
    Abstract [en]

    Ecological stoichiometry has been successful in enhancing our understanding of trophic interactions between consumer and prey species. Consumer and prey dynamics have been shown to depend on the nutrient composition of the prey relative to the nutrient demand of the consumer. Since most experiments on this topic used a single consumer species, little is known about the validity of stoichiometric constraints on trophic interactions across consumers and ecosystems. We conducted a quantitative meta-analysis on grazer-periphyton experiments to test (1) if benthic grazers have consistent effects on the nutrient composition of their prey, and (2) whether these effects can be aligned to the nutrient stoichiometry of grazer and periphyton, other environmental factors, or experimental constraints. Grazers significantly lowered periphyton C:N and C:P ratios, indicating higher N- and P-content of grazed periphyton across studies. Grazer presence on average increased periphyton N:P ratios, but across studies the effect size did not differ significantly from zero. The sign and strength of grazer effects on periphyton nutrient ratios was strongly dependent on the nutrient content of grazers and their food, but also on grazer biomass, the amount of biomass removal and water column nutrients. Grazer with low P-content tended to reduce periphyton P-content, whereas grazers with high P-content increased periphyton P-content. This result suggests that low grazer P-content can be an indication of physiological P-limitation rather than a result of having relatively low and fixed P-requirements. At the across-system scale of this meta-analysis, predictions from stoichiometric theory are corroborated, but the plasticity of the consumer nutrient composition has to be acknowledged.

  • 195.
    Hillebrand, Helmut
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Kahlert, Maria
    Effect of grazing and nutrient supply on periphyton biomass and nutrient stoichiometry in habitats of different productivity2001In: Limnology & Oceanography, Vol. 46, no 8, p. 1881-1898Article in journal (Refereed)
  • 196.
    Hillebrand, Helmut
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Kahlert, Maria
    Haglund, Ann-Louise
    Berninger, Ulrike
    Nagel, Simone
    Wickham, Stephen
    Control of microbenthic communities by grazing and nutrient supply2002In: Ecology, Vol. 83, no 8, p. 2205-2219Article in journal (Refereed)
  • 197.
    Hillebrand, Helmut
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Watermann, Frank
    Karez, Rolf
    Berninger, Ulrike-G.Watermann, FrankKarez, RolfBerninger, Ulrike-G.
    Differences in species richness patterns between unicellular and multicellular organisms2001In: Oecologia, Vol. 126, no 1, p. 114-124Article in journal (Refereed)
    Abstract [en]

    For unicellular organisms, a lack of effects of local species richness on ecosystem function has been proposed due to their locally high species

  • 198.
    Hirsch, Philipp Emanuel
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Freshwater crayfish invasions: former crayfish invader Galician crayfish hands title "invasive" over to new invader spiny-cheek crayfish2009In: Biological Invasions, ISSN 1387-3547, E-ISSN 1573-1464, Vol. 11, no 3, p. 515-521Article in journal (Refereed)
    Abstract [en]

    Biological invasions are a major threat to global biodiversity. Invasive freshwater crayfish in that context are especially prominent for their negative effects on both ecosystem integrity and native crayfish. However, some systems may have supported a crayfish species not originally native to the system without perceivable negative consequences for the ecosystem while other invasive crayfish species may constitute a major threat to ecosystem stability. Here I present an example how two crayfish, the spiny-cheek and the Galician crayfish both by researchers and governmental agencies considered non-native differ in their threats to the native ecosystem. Whereas the spiny-cheek crayfish is a recent potentially disease-transmitting and still spreading invader with high local densities the Galician crayfish might be part of the lake's fauna since several hundred years, appears in lower densities and is unlikely to be a vector of disease. Therefore, regardless of the Galician crayfish's actual date of introduction it is thus a rather "old and integrated" invader, which is now being faced and itself potentially threatened by the emergence of a "new and dangerous" invader: the spiny-cheek crayfish. This also exemplifies that in the face of often insufficient scientific information about dates of species introductions care should be taken in postulating species as invasive and dangerous without any form of risk assessment for their impact on the ecosystem.

  • 199.
    Hirsch, Philipp Emanuel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Fischer, Philipp
    Interactions between native juvenile burbot (Loto loto L.) and the invasive spiny-cheek crayfish (Oronectes limosus, Rafinesque) in a large European lake2008In: Canadian Journal of Fisheries and Aquatic Sciences, ISSN 0706-652X, E-ISSN 1205-7533, Vol. 65, no 12, p. 2636-2643Article in journal (Refereed)
    Abstract [en]

    Freshwater crayfish are successful invaders in many ecosystems and as cryptic nocturnal species display a potential niche overlap with benthic nocturnal fish. In this study, we tested the effects of the invasive spinycheek crayfish (Orconectes limosus) on native young-of-the-year (YOY) and adult burbot (Lota lota) in Lake Constance. Using mesocosm experiments, we tested if shelter preferences of YOY and adult burbot and crayfish changed between single and mixed species treatments. To further study the role of crayfish as a stressor for   burbot, we monitored the nocturnal behaviour of the species in mesocosms using passive integrated transponder ( PIT) tag technology and subsequently determined the plasma cortisol levels in burbot after single and mixed species treatments. Spinycheek crayfish successfully repelled YOY burbot from their preferred daytime shelters into alternative, previously unselected shelters. Crayfish also affected the nocturnal behaviour of YOY burbot by eliciting avoidance behaviour and caused an increase in the plasma cortisol levels. While adult burbot did not display any changes between single and mixed species treatments, our results indicate negative effects of spinycheek crayfish on YOY burbot. We conclude that the frequently dense, invasive crayfish populations in lakes may negatively influence local benthic fish populations via their YOY cohorts.

  • 200.
    Hirsch, Philipp Emanuel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Nechwatal, Jan
    Fischer, Philipp
    A previously undescribed set of Saprolegnia spp. In the invasive spiny-cheek crayfish (Oronectes limosus, Rafinesque)2008In: Fundamental and Applied Limnology, ISSN 1863-9135, Vol. 172, no 2, p. 1-5Article in journal (Refereed)
    Abstract [en]

    Coinciding with a population decline in the invasive spiny-cheek crayfish Orconectes limosus in Lake Constance. SW Germany, we found crayfish specimens with a fungus-like Aufwuchs which after DNA-isolation and sequencing was identified as consisting of a set of previously undescribed Saprolegnia species. This finding may have implications for the farming and conservation of native crayfish as well as for the lake's ecosystem. We propose that spiny-cheek crayfish might function as a disease vector for these potential pathogens.