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Ahlgren, Gunnel
Alternative names
Publications (10 of 14) Show all publications
Galloway, A. W. E., Brett, M. T., Holtgrieve, G. W., Ward, E. J., Ballantyne, A. P., Burns, C. W., . . . Alhgren, G. (2015). A Fatty Acid Based Bayesian Approach for Inferring Diet in Aquatic Consumers. PLoS ONE, 10(6), Article ID e0129723.
Open this publication in new window or tab >>A Fatty Acid Based Bayesian Approach for Inferring Diet in Aquatic Consumers
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2015 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 10, no 6, article id e0129723Article in journal (Refereed) Published
Abstract [en]

We modified the stable isotope mixing model MixSIR to infer primary producer contributions to consumer diets based on their fatty acid composition. To parameterize the algorithm, we generated a 'consumer-resource library' of FA signatures of Daphnia fed different algal diets, using 34 feeding trials representing diverse phytoplankton lineages. This library corresponds to the resource or producer file in classic Bayesian mixing models such as MixSIR or SIAR. Because this library is based on the FA profiles of zooplankton consuming known diets, and not the FA profiles of algae directly, trophic modification of consumer lipids is directly accounted for. To test the model, we simulated hypothetical Daphnia comprised of 80% diatoms, 10% green algae, and 10% cryptophytes and compared the FA signatures of these known pseudo-mixtures to outputs generated by the mixing model. The algorithm inferred these simulated consumers were comprised of 82% (63-92%) [median (2.5th to 97.5th percentile credible interval)] diatoms, 11% (4-22%) green algae, and 6% (0-25%) cryptophytes. We used the same model with published phytoplankton stable isotope (SI) data for delta C-13 and delta N-15 to examine how a SI based approach resolved a similar scenario. With SI, the algorithm inferred that the simulated consumer assimilated 52% (4-91%) diatoms, 23% (1-78%) green algae, and 18% (1-73%) cyanobacteria. The accuracy and precision of SI based estimates was extremely sensitive to both resource and consumer uncertainty, as well as the trophic fractionation assumption. These results indicate that when using only two tracers with substantial uncertainty for the putative resources, as is often the case in this class of analyses, the underdetermined constraint in consumer-resource SI analyses may be intractable. The FA based approach alleviated the underdetermined constraint because many more FA biomarkers were utilized (n < 20), different primary producers (e.g., diatoms, green algae, and cryptophytes) have very characteristic FA compositions, and the FA profiles of many aquatic primary consumers are strongly influenced by their diets.

National Category
Ecology
Identifiers
urn:nbn:se:uu:diva-260731 (URN)10.1371/journal.pone.0129723 (DOI)000358147500037 ()26114945 (PubMedID)
Available from: 2015-08-25 Created: 2015-08-24 Last updated: 2017-12-04Bibliographically approved
Larson, D., Ahlgren, G. & Willén, E. (2014). Bioaccumulation of microcystins in the food web: a field study of four Swedish lakes. INLAND WATERS, 4(1), 91-104
Open this publication in new window or tab >>Bioaccumulation of microcystins in the food web: a field study of four Swedish lakes
2014 (English)In: INLAND WATERS, ISSN 2044-2041, E-ISSN 2044-205X, Vol. 4, no 1, p. 91-104Article in journal (Refereed) Published
Abstract [en]

The transfer of microcystins (MC) up the food chain was measured in 4 lakes in central Sweden; Ekoln, Lilla Ullfjärden, Valloxen, and Storsjön. In lakes Ekoln and Valloxen, Microcystis aeruginosa was the dominant cyanobacterium, while the oscillatorian species Planktothrix prolifica form dense blooms in Lake Lilla Ullfjärden. The cyanobacterial composition in Lake Storsjön was more diverse with several Microcystis andDolichospermum species. All dominant taxa are well-known producers of hepatotoxic MC. The highest recorded MC in the water samples from Lake Lilla Ullfjärden was measured in the bloom of Pprolifica (35 µg L−1). The highest MC content was measured in invertebrates; however, the MC concentration was usually low in fish. Maximum levels were 9 µg g−1 dry weight (dw) in zooplankton, 10 µg g−1 dw in benthos, and 2.7 µg g−1 dw in fish (smelt) liver. In fish muscle the highest recorded levels were 0.10–0.18 µg g−1 dw in bleak and smelt from Lake Lilla Ullfjärden and in pike-perch and roach from Lake Storsjön. Based on the World Health Organization’s tolerable daily intake value of 0.04 µg kg−1 body weight, we conclude that any risk related to MC from human consumption of fish from these lakes is minimal.

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-238729 (URN)
Available from: 2014-12-16 Created: 2014-12-16 Last updated: 2017-12-05Bibliographically approved
Willen, E., Ahlgren, G., Tilahun, G., Spoof, L., Neffling, M.-R. & Meriluoto, J. (2011). Cyanotoxin production in seven Ethiopian Rift Valley lakes. INLAND WATERS, 1(2), 81-91
Open this publication in new window or tab >>Cyanotoxin production in seven Ethiopian Rift Valley lakes
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2011 (English)In: INLAND WATERS, ISSN 2044-2041, E-ISSN 2044-205X, Vol. 1, no 2, p. 81-91Article in journal (Refereed) Published
Abstract [en]

We hypothesized that unusual deaths and illnesses in wild and domestic animals in lake areas of the Rift Valley south of Addis Ababa were caused by toxic cyanobacteria. In the first cyanotoxic analyses conducted in samples from Ethiopia, we found lakes Chamo, Abaya, Awassa, Chitu, Langano, Ziway, and Koka all had concentrations of microcystins (MC) ranging from trace to hazardous, whereas only traces less than limits of detection (LOD) of cylindrospermopsin (CYN) were found. In the December 2006 dry season we sampled the lakes for analyses of MC, CYN, species structures, and calculations of cyanobacteria biomass. We used the Utermol technique to analyse cyanobacterial biomass and monitored MC toxins using HPLC-DAD, LC-ESI-MS-MRM, and ELISA-test and CYN with HPLC-DAD and ELISA. The various toxicity tests coincided well. In 4 of the lakes (Chamo, Langano, Ziway, and Koka), the inter-lake range of total MC concentration was 1.3-48 mu g L-1; in 3 (Abaya, Awassa, and Chitu), we found only traces of MC. Microcystis aeruginosa was the dominant species, with Microcystis panniformis, Anabaena spiroides, and Cylindrospermopsis spp. as subdominants. The MC concentration, especially in Lake Koka, exceeded levels for serious health hazards for humans, cattle, and wildlife.

Keywords
CyanoHAB, cylindrospermosin, ELISA, Ethiopian Rift Valley lakes, HPLC, mass spectrometry, microcystins, Microcystis
National Category
Ecology
Identifiers
urn:nbn:se:uu:diva-260015 (URN)10.5268/IW-1.2.391 (DOI)000307720900002 ()
Available from: 2015-08-13 Created: 2015-08-13 Last updated: 2017-12-04Bibliographically approved
Goedkoop, W., Demandt, M. & Ahlgren, G. (2007). Interactions between food quantity and quality (long-chain polyunsaturated fatty acid concentrations) effects on growth and development of Chironomus riparius. Canadian Journal of Fisheries and Aquatic Sciences, 64(3), 425-436
Open this publication in new window or tab >>Interactions between food quantity and quality (long-chain polyunsaturated fatty acid concentrations) effects on growth and development of Chironomus riparius
2007 (English)In: Canadian Journal of Fisheries and Aquatic Sciences, ISSN 0706-652X, E-ISSN 1205-7533, Vol. 64, no 3, p. 425-436Article in journal (Refereed) Published
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.

National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-13327 (URN)10.1139/F07-016 (DOI)000246188700005 ()
Available from: 2008-01-28 Created: 2008-01-28 Last updated: 2017-12-11Bibliographically approved
Dadebo, E., Ahlgren, I. & Ahlgren, G. (2005). Maturation, sex ratio and fecundity of the Nile perch, Lates niloticus (L.) (Pisces: Centropomidae) in Lake Chamo, Ethiopia. SINET: Ethiop. J. Sci., 28(2), 151-160
Open this publication in new window or tab >>Maturation, sex ratio and fecundity of the Nile perch, Lates niloticus (L.) (Pisces: Centropomidae) in Lake Chamo, Ethiopia
2005 (English)In: SINET: Ethiop. J. Sci., ISSN 0379-2897, Vol. 28, no 2, p. 151-160Article in journal (Refereed) Published
Keywords
Fecundity, Lake Chamo, Lates niloticus, maturity, sex ratio
National Category
Ecology
Identifiers
urn:nbn:se:uu:diva-79405 (URN)
Available from: 2006-04-19 Created: 2006-04-19 Last updated: 2011-01-11
Dadebo, E., Ahlgren, G. & Ahlgren, I. (2003). Aspects of reproductive biology of Labeo horie Heckel (Pisces: Cyprinidae) in Lake Chamo, Ethiopia. African Journal of Ecology, 41, 31-38
Open this publication in new window or tab >>Aspects of reproductive biology of Labeo horie Heckel (Pisces: Cyprinidae) in Lake Chamo, Ethiopia
2003 (English)In: African Journal of Ecology, Vol. 41, p. 31-38Article in journal (Refereed) Published
National Category
Ecology
Identifiers
urn:nbn:se:uu:diva-47537 (URN)
Available from: 2006-04-07 Created: 2006-04-07 Last updated: 2011-01-13
Tadesse, Z., Boberg, M., Sonesten, L. & Ahlgren, G. (2003). Effects of algal diets and temperature on the growth and fatty acid contents of the cichlid fish Oreochromis niloticus L. - A laboratory study.. Aquatic Ecology, 37, 169-182
Open this publication in new window or tab >>Effects of algal diets and temperature on the growth and fatty acid contents of the cichlid fish Oreochromis niloticus L. - A laboratory study.
2003 (English)In: Aquatic Ecology, Vol. 37, p. 169-182Article in journal (Refereed) Published
National Category
Ecology
Identifiers
urn:nbn:se:uu:diva-79411 (URN)
Available from: 2006-04-07 Created: 2006-04-07 Last updated: 2011-01-13
Ahlgren, G. & Hyenstrand, P. (2003). Nitrogen limitation effects of different nitrogen sources on nutritional quality of two freshwater organisms, Scenedesmus Quadricauda (Clorophyceae) and Synechococcus sp. (Cyanophyceae). J. Phycol., 39, 906-917
Open this publication in new window or tab >>Nitrogen limitation effects of different nitrogen sources on nutritional quality of two freshwater organisms, Scenedesmus Quadricauda (Clorophyceae) and Synechococcus sp. (Cyanophyceae)
2003 (English)In: J. Phycol., Vol. 39, p. 906-917Article in journal (Refereed) Published
National Category
Ecology
Identifiers
urn:nbn:se:uu:diva-47520 (URN)
Available from: 2006-04-07 Created: 2006-04-07 Last updated: 2011-01-13
Ahlgren, G., Ahlgren, I., Hernández, S. & Mejia, M. (2002). Fatty acid quality of seston and its effects on small fish in the lakes Xolotlán and Cocibolca, Nicaragua.. Verh. Internat. Verein. Limnol., 28, 786-791
Open this publication in new window or tab >>Fatty acid quality of seston and its effects on small fish in the lakes Xolotlán and Cocibolca, Nicaragua.
2002 (English)In: Verh. Internat. Verein. Limnol., Vol. 28, p. 786-791Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-44726 (URN)
Available from: 2006-04-03 Created: 2006-04-03 Last updated: 2011-01-13
Ahlgren, G., Hyenstrand, P., Vrede, T., Karlsson, E. & Zetterberg, S. (2001). Nutritional quality of Scenedesmus quadricauda (Chlorophyceae) grown in different nitrogen regimes and tested on Daphnia. International Association of Theoretical and Applied Limnology, 27(3), 1234-1238
Open this publication in new window or tab >>Nutritional quality of Scenedesmus quadricauda (Chlorophyceae) grown in different nitrogen regimes and tested on Daphnia
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2001 (English)In: International Association of Theoretical and Applied Limnology, Vol. 27, no 3, p. 1234-1238Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-36181 (URN)
Available from: 2007-01-25 Created: 2007-01-25 Last updated: 2011-01-13
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