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3. Oxygen Depletion in Arctic Lakes:Circumpolar Trends, Biogeochemical Processes, and Implications of Climate Change

Author

Klanten, Y., Couture, R. M., Christoffersen, K. S., Vincent, W. F., Antoniades, D., Klanten, Y., Couture, R. M., Christoffersen, K. S., Vincent, W. F., and Antoniades, D.

Abstract

Polar amplification of climate change has the potential to cause large-scale shifts in the dissolved oxygen (DO) dynamics of Arctic lakes, with implications for fish survival, greenhouse gas production, and drinking water quality. While DO is also a sentinel of environmental changes of physical, chemical, and biological nature (e.g., ice cover, temperature, dissolved organic carbon, photosynthesis, and respiration), no synthesis exists of current knowledge of DO dynamics across the diverse freshwater systems of the Arctic. We thus conducted a systematic review of the literature that yielded DO data from 167 sites north of the Subarctic limit (based on vegetation zones), spanning 76 years and including 40 sites with time series. The compilation revealed insufficient observations for adequate representativeness of oxygen dynamics over Arctic ecosystem gradients. We described the main processes controlling DO budgets of Arctic lakes and tested relationships of summer oxygen depletion with maximum depth and latitude. The meta-analysis showed that most sites with low O2 concentrations were shallow (<10 m) and situated toward the southern end of the latitudinal gradient. Permanently stratified lakes with deep, perennially anoxic basins were located toward the northern end of the gradient. By way of a conceptual model, we identified the direct and indirect drivers and mechanisms that lead to changes in oxygen budgets in the context of the warming Arctic. This comprehensive update on available data allowed us to suggest future research directions and recommend the use of moored instruments for continuous all-season observations, combined with modeling, remote sensing, and paleo-reconstructions., Polar amplification of climate change has the potential to cause large-scale shifts in the dissolved oxygen (DO) dynamics of Arctic lakes, with implications for fish survival, greenhouse gas production, and drinking water quality. While DO is also a sentinel of environmental changes of physical, chemical, and biological nature (e.g., ice cover, temperature, dissolved organic carbon, photosynthesis, and respiration), no synthesis exists of current knowledge of DO dynamics across the diverse freshwater systems of the Arctic. We thus conducted a systematic review of the literature that yielded DO data from 167 sites north of the Subarctic limit (based on vegetation zones), spanning 76 years and including 40 sites with time series. The compilation revealed insufficient observations for adequate representativeness of oxygen dynamics over Arctic ecosystem gradients. We described the main processes controlling DO budgets of Arctic lakes and tested relationships of summer oxygen depletion with maximum depth and latitude. The meta-analysis showed that most sites with low O2 concentrations were shallow (<10 m) and situated toward the southern end of the latitudinal gradient. Permanently stratified lakes with deep, perennially anoxic basins were located toward the northern end of the gradient. By way of a conceptual model, we identified the direct and indirect drivers and mechanisms that lead to changes in oxygen budgets in the context of the warming Arctic. This comprehensive update on available data allowed us to suggest future research directions and recommend the use of moored instruments for continuous all-season observations, combined with modeling, remote sensing, and paleo-reconstructions.

Published
2023

4. The terrestrial and freshwater invertebrate biodiversity of the archipelagoes of the Barents Sea; Svalbard, Franz Josef Land and Novaya Zemlya

Author

Coulson, S.J., Convey, P., Aakra, K., Aarvik, L., Ávila-Jiménez, M.L., Babenko, A., Biersma, E.M., Boström, S., Brittain, J.E., Carlsson, A.M., Christoffersen, K., De Smet, W.H., Ekrem, T., Fjellberg, A., Füreder, L., Gustafsson, D., Gwiazdowicz, D.J., Hansen, L.O., Holmstrup, M., Hullé, M., Kaczmarek, Ł., Kolicka, M., Kuklin, V., Lakka, H.-K., Lebedeva, N., Makarova, O., Maraldo, K., Melekhina, E., Ødegaard, F., Pilskog, H.E., Simon, J.C., Sohlenius, B., Solhøy, T., Søli, G., Stur, E., Tanasevitch, A., Taskaeva, A., Velle, G., Zawierucha, K., and Zmudczyńska-Skarbek, K.

Published
2014
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6. Plastic debris in freshwater systems worldwide

Author

Nava, V, Aherne, J, Alfonso, M, Antão-Geraldes, A, Attermeyer, K, Bao, R, Bartrons, M, Berger, S, Biernaczyk, M, Bissen, R, Brookes, J, Brown, D, Candian, G, Cañedo-Argüelles, M, Canle, M, Capelli, C, Carballeira, R, Cereijo, J, Chawchai, S, Chen, G, Christensen, S, Christoffersen, K, de Eyto, E, Delgado, J, Dornan, T, Doubek, J, Dusaucy, J, Erina, O, Ersoy, Z, Feuchtmayr, H, Lepori, F, Frezzotti, M, Galafassi, S, Gateuille, D, Gonçalves, V, Grossart, H, Hamilton, D, Harris, T, Kangur, K, Kankılıç, G, Kessler, R, Kiel, C, Krynak, E, Leiva-Presa, A, Matias, M, Matsuzaki, S, Mcelarney, Y, Mitchell, M, Messyasz, B, Mlambo, M, Motitsoe, S, Owens, C, Özkundakci, D, Pinnow, S, Pociecha, A, Raposeiro, P, Rõõm, E, Rotta, F, Salmaso, N, Scordo, F, Sibomana, C, Siewert, D, Stepanowska, K, Sudeep, C, Tavşanoğlu, U, Tereshina, M, Thompson, J, Tolotti, M, Valois, A, Verburg, P, Wesolek, B, Weyhenmeyer, G, Wu, N, Zawisza, E, Zink, L, Leoni, B, Alfonso, MB, Antão-Geraldes, AM, Berger, SA, Cereijo, JL, Christensen, ST, Christoffersen, KS, Doubek, JP, Frezzotti, ML, Grossart, HP, Hamilton, DP, Kankılıç, GB, Krynak, EM, Matsuzaki, SS, McElarney, Y, Motitsoe, SN, Rõõm, EI, Tavşanoğlu, UN, Nava, V, Aherne, J, Alfonso, M, Antão-Geraldes, A, Attermeyer, K, Bao, R, Bartrons, M, Berger, S, Biernaczyk, M, Bissen, R, Brookes, J, Brown, D, Candian, G, Cañedo-Argüelles, M, Canle, M, Capelli, C, Carballeira, R, Cereijo, J, Chawchai, S, Chen, G, Christensen, S, Christoffersen, K, de Eyto, E, Delgado, J, Dornan, T, Doubek, J, Dusaucy, J, Erina, O, Ersoy, Z, Feuchtmayr, H, Lepori, F, Frezzotti, M, Galafassi, S, Gateuille, D, Gonçalves, V, Grossart, H, Hamilton, D, Harris, T, Kangur, K, Kankılıç, G, Kessler, R, Kiel, C, Krynak, E, Leiva-Presa, A, Matias, M, Matsuzaki, S, Mcelarney, Y, Mitchell, M, Messyasz, B, Mlambo, M, Motitsoe, S, Owens, C, Özkundakci, D, Pinnow, S, Pociecha, A, Raposeiro, P, Rõõm, E, Rotta, F, Salmaso, N, Scordo, F, Sibomana, C, Siewert, D, Stepanowska, K, Sudeep, C, Tavşanoğlu, U, Tereshina, M, Thompson, J, Tolotti, M, Valois, A, Verburg, P, Wesolek, B, Weyhenmeyer, G, Wu, N, Zawisza, E, Zink, L, Leoni, B, Alfonso, MB, Antão-Geraldes, AM, Berger, SA, Cereijo, JL, Christensen, ST, Christoffersen, KS, Doubek, JP, Frezzotti, ML, Grossart, HP, Hamilton, DP, Kankılıç, GB, Krynak, EM, Matsuzaki, SS, McElarney, Y, Motitsoe, SN, Rõõm, EI, and Tavşanoğlu, UN

Published
2022

7. Fish manipulation as a lake restoration tool in shallow, eutrophic temperate lakes 1: cross-analysis of three Danish case-studies

Author

Jeppesen, E., Søndergaard, M., Mortensen, E., Kristensen, P., Riemann, B., Jensen, H. J., Müller, J. P., Sortkjær, O., Jensen, J. P., Christoffersen, K., Bosselmann, S., Dall, E., Dumont, H. J., editor, Gulati, Ramesh D., editor, Lammens, Eddy H. R. R., editor, Meijer, Marie-Louise, editor, and van Donk, Ellen, editor

Published
1990
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8. The Effects of Hypoxia on Zooplankton Population Estimates and Migration in Lakes

Author

Goldfarb, S, Doubek, J, Antão-Geraldes, A, Bartrons, M, Berger, S, Brentrup, J, Brucet, S, Burnet, S, Caputo Galarce, L, Carey, C, Christoffersen, K, de Eyto, E, Dur, G, Erdoğan, S, Erina, O, Grossart, H, Kainz, M, Kankılıç, G, Khan, S, Leoni, B, Lepori, F, Mccarthy, V, Nava, V, Nejstgaard, J, Obertegger, U, Ogorelec, Z, Ozen, A, Pascual, M, Paterson, M, Patelli, M, Qiu, Q, Richardson, D, Sepulveda-Jauregui, A, Silva, L, Straile, D, Tartarotti, B, Tavşanoğlu, U, Tereshina, M, Umaña-Villalobos, G, Walles, T, Wander, H, Wurtsbaugh, W, Stockwell, S, Goldfarb, SK, Bartrons, M., Berger, S., Brentrup, JA, Carey, CC, Christoffersen, K., Grossart, HP, Kainz, M., Kankılıç, GB, McCarthy, V, Tavşanoğlu, UN, Wander, HL, Goldfarb, S, Doubek, J, Antão-Geraldes, A, Bartrons, M, Berger, S, Brentrup, J, Brucet, S, Burnet, S, Caputo Galarce, L, Carey, C, Christoffersen, K, de Eyto, E, Dur, G, Erdoğan, S, Erina, O, Grossart, H, Kainz, M, Kankılıç, G, Khan, S, Leoni, B, Lepori, F, Mccarthy, V, Nava, V, Nejstgaard, J, Obertegger, U, Ogorelec, Z, Ozen, A, Pascual, M, Paterson, M, Patelli, M, Qiu, Q, Richardson, D, Sepulveda-Jauregui, A, Silva, L, Straile, D, Tartarotti, B, Tavşanoğlu, U, Tereshina, M, Umaña-Villalobos, G, Walles, T, Wander, H, Wurtsbaugh, W, Stockwell, S, Goldfarb, SK, Bartrons, M., Berger, S., Brentrup, JA, Carey, CC, Christoffersen, K., Grossart, HP, Kainz, M., Kankılıç, GB, McCarthy, V, Tavşanoğlu, UN, and Wander, HL

Published
2019

12. Integrated Reservoir Modeling with Deep Directional Resistivity Data and Its Application for Geosteering on Ivar Aasen

Author

J. Jøssund, T., primary, E. Elfenbein, C., additional, J. Johansen, Y., additional, D. Drange, I., additional, O. Olsborg, L., additional, S. Skorve, T., additional, K. Kvilaas, G., additional, C. Christoffersen, K., additional, M. Mastad, S., additional, S. Stubsjøen, M., additional, W. Wang, H., additional, and M. Denichou, J., additional

Published
2018
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14. A European Multi Lake Survey dataset of environmental variables, phytoplankton pigments and cyanotoxins

Author

European Cooperation in Science and Technology, Hernández, Armand [0000-0001-7245-9863], Mantzouki, E., Campbell, James, van Loon, E., Visser, P., Konstantinou, I., Antoniou, M., Giuliani, G., Machado-Vieira, D., Gurjão de Oliveira, Alinne, Maronić, D.Š., Stević, F., Hiskia, A., Gkelis, S., Walusiak, E., Panou, M., McCarthy, V., Budzyńska, A., Perello, V.C., Kostrzewska-Szlakowska, I., Gonçalves, V., Skjelbred, B., Palomino, Roberto L., Obertegger, U., Boscaini, A., Flaim, G., Salmaso, N., Gagala, I., Cerasino, L., Mankiewicz-Boczek, J., Hansson, L. A., Grabowska, M., Karpowicz, M., Rodríguez-Pérez, E., Chmura, D., Nawrocka, L., Kozak, A., Kobos, J., Rosińska, J., Seelen, L., Toporowska, M., Pawlik-Skowronska, B., Urrutia-Cordero, Pablo, Niedźwiecki, M., Maliaka, V., Pęczuła, W., Wasilewicz, M., Napiórkowska-Krzebietke, A., Ochocka, A., Beklioğlu, M., Szeląg-Wasielewska, E., Domek, P., Teurlincx, S., Jakubowska-Krepska, N., Tavşanoğlu, ÜN., Carballeira, R., Kwasizur, K., Drastichova, I., Messyasz, B., Chomova, L., Soylu, E.N., Pasztaleniec, A., Jasser, I., Filiz, N., Antão-Geraldes, A. M., Bilgin, F., Camacho, A., Özen, A., Leira, M., Hernández, Armand, Vasconcelos, V., Remec-Rekar, S., Pfeiffer, T.Ž., Eleršek, Tina, Delgado-Martín, Jordi, Yağcı, M.A., García, D., Bezirci, G., Bláha, L., Bravo, Andrea G., Verstijnen, Y., Cereijo, J. L., Gomà, Joan, Trapote, M.C., Vegas-Vilarrúbia, Teresa, Obrador, B., García-Murcia, A., Real, M., Picazo, Antoni, Vucelić, I.B., Romans, E., Cesur, M., Çınar, Ş., Lürling, M., Levi, E., Noguero-Ribes, J., Duque, D.P., Fernández-Morán, E., Úbeda, B., Yağcı, A., Gálvez, J.Á., Marcé, Rafael, Catalán, N., Buck, Moritz, Pérez-Martínez, Carmen, Ramos-Rodríguez, E., Tsiarta, N., Žutinić, P., Iskin, U., Çapkın, K., Udovič, M.G., Cillero-Castro, C., Moreno-Ostos, Enrique, Blanco, J. M., Rodríguez, V., Plenković-Moraj, Anđelka, Montes-Pérez, J.J., Colom-Montero, W., Koreivienė, J., Rochera, C., Santamans, A. C., Ferriol, C., Romo, S., Faassen, E.J., Soria, J. M., Latour, D., Mazur-Marzec, Hanna, Mustonen, K., Pierson, D., Kasperovičienė, J., Yang, Y., Verspagen, Jolanda M. H., Çelik, K., de Senerpont Domis, L.N., Özhan, K., Dunalska, J., Carey, C.C., Paerl, Hans, Alcaraz-Párraga, P., Torokne, A., Goldyn, R., Karan, T., Bulut, C., Demir, N., Uysal, R., Pełechata, A., Karakaya, N., Koçer, M.A.T., Sieńska, J., Yilmaz, M., Bańkowska-Sobczak, A., Savadova, K., Maraşlıoğlu, F., Geriš, R., Fakioglu, Ö., Fránková, M., Morais, J., Köker, L., Bergkemper, V., Pełechaty, M., O'Leary, S., Nemova, H., Vitonytė, I., Wilk-Woźniak, E., Beirne, E., Cromie, H., Ibelings, Bas W., Christoffersen, K. S., Warming, T.P., Feldmann, T., Laas, A., Vale, M., Panksep, K., Frąk, M., Kokocinski, M., Krztoń, W., Szymański, D., Tuvikene, L., Kangro, K., Häggqvist, K., Salmi, P., Arvola, L., Fastner, J., Straile, D., Haande, S., Rothhaupt, K. O., Fonvielle, J., Krstić, S., Raposeiro, P. M., Kruk, M., Madrecka, B., Grossart, Hans-Peter, Avagianos, C., Kaloudis, T., Triantis, T., Aleksovski, B., Zervou, S. K., European Cooperation in Science and Technology, Hernández, Armand [0000-0001-7245-9863], Mantzouki, E., Campbell, James, van Loon, E., Visser, P., Konstantinou, I., Antoniou, M., Giuliani, G., Machado-Vieira, D., Gurjão de Oliveira, Alinne, Maronić, D.Š., Stević, F., Hiskia, A., Gkelis, S., Walusiak, E., Panou, M., McCarthy, V., Budzyńska, A., Perello, V.C., Kostrzewska-Szlakowska, I., Gonçalves, V., Skjelbred, B., Palomino, Roberto L., Obertegger, U., Boscaini, A., Flaim, G., Salmaso, N., Gagala, I., Cerasino, L., Mankiewicz-Boczek, J., Hansson, L. A., Grabowska, M., Karpowicz, M., Rodríguez-Pérez, E., Chmura, D., Nawrocka, L., Kozak, A., Kobos, J., Rosińska, J., Seelen, L., Toporowska, M., Pawlik-Skowronska, B., Urrutia-Cordero, Pablo, Niedźwiecki, M., Maliaka, V., Pęczuła, W., Wasilewicz, M., Napiórkowska-Krzebietke, A., Ochocka, A., Beklioğlu, M., Szeląg-Wasielewska, E., Domek, P., Teurlincx, S., Jakubowska-Krepska, N., Tavşanoğlu, ÜN., Carballeira, R., Kwasizur, K., Drastichova, I., Messyasz, B., Chomova, L., Soylu, E.N., Pasztaleniec, A., Jasser, I., Filiz, N., Antão-Geraldes, A. M., Bilgin, F., Camacho, A., Özen, A., Leira, M., Hernández, Armand, Vasconcelos, V., Remec-Rekar, S., Pfeiffer, T.Ž., Eleršek, Tina, Delgado-Martín, Jordi, Yağcı, M.A., García, D., Bezirci, G., Bláha, L., Bravo, Andrea G., Verstijnen, Y., Cereijo, J. L., Gomà, Joan, Trapote, M.C., Vegas-Vilarrúbia, Teresa, Obrador, B., García-Murcia, A., Real, M., Picazo, Antoni, Vucelić, I.B., Romans, E., Cesur, M., Çınar, Ş., Lürling, M., Levi, E., Noguero-Ribes, J., Duque, D.P., Fernández-Morán, E., Úbeda, B., Yağcı, A., Gálvez, J.Á., Marcé, Rafael, Catalán, N., Buck, Moritz, Pérez-Martínez, Carmen, Ramos-Rodríguez, E., Tsiarta, N., Žutinić, P., Iskin, U., Çapkın, K., Udovič, M.G., Cillero-Castro, C., Moreno-Ostos, Enrique, Blanco, J. M., Rodríguez, V., Plenković-Moraj, Anđelka, Montes-Pérez, J.J., Colom-Montero, W., Koreivienė, J., Rochera, C., Santamans, A. C., Ferriol, C., Romo, S., Faassen, E.J., Soria, J. M., Latour, D., Mazur-Marzec, Hanna, Mustonen, K., Pierson, D., Kasperovičienė, J., Yang, Y., Verspagen, Jolanda M. H., Çelik, K., de Senerpont Domis, L.N., Özhan, K., Dunalska, J., Carey, C.C., Paerl, Hans, Alcaraz-Párraga, P., Torokne, A., Goldyn, R., Karan, T., Bulut, C., Demir, N., Uysal, R., Pełechata, A., Karakaya, N., Koçer, M.A.T., Sieńska, J., Yilmaz, M., Bańkowska-Sobczak, A., Savadova, K., Maraşlıoğlu, F., Geriš, R., Fakioglu, Ö., Fránková, M., Morais, J., Köker, L., Bergkemper, V., Pełechaty, M., O'Leary, S., Nemova, H., Vitonytė, I., Wilk-Woźniak, E., Beirne, E., Cromie, H., Ibelings, Bas W., Christoffersen, K. S., Warming, T.P., Feldmann, T., Laas, A., Vale, M., Panksep, K., Frąk, M., Kokocinski, M., Krztoń, W., Szymański, D., Tuvikene, L., Kangro, K., Häggqvist, K., Salmi, P., Arvola, L., Fastner, J., Straile, D., Haande, S., Rothhaupt, K. O., Fonvielle, J., Krstić, S., Raposeiro, P. M., Kruk, M., Madrecka, B., Grossart, Hans-Peter, Avagianos, C., Kaloudis, T., Triantis, T., Aleksovski, B., and Zervou, S. K.

Abstract

Under ongoing climate change and increasing anthropogenic activity, which continuously challenge ecosystem resilience, an in-depth understanding of ecological processes is urgently needed. Lakes, as providers of numerous ecosystem services, face multiple stressors that threaten their functioning. Harmful cyanobacterial blooms are a persistent problem resulting from nutrient pollution and climate-change induced stressors, like poor transparency, increased water temperature and enhanced stratification. Consistency in data collection and analysis methods is necessary to achieve fully comparable datasets and for statistical validity, avoiding issues linked to disparate data sources. The European Multi Lake Survey (EMLS) in summer 2015 was an initiative among scientists from 27 countries to collect and analyse lake physical, chemical and biological variables in a fully standardized manner. This database includes in-situ lake variables along with nutrient, pigment and cyanotoxin data of 369 lakes in Europe, which were centrally analysed in dedicated laboratories. Publishing the EMLS methods and dataset might inspire similar initiatives to study across large geographic areas that will contribute to better understanding lake responses in a changing environment.

Published
2018

16. Water Chemistry of Five Faroese Lakes

Author

Jensen, J. P., Christoffersen, K., Landkildehus, F., Søndergaard, M., Jeppesen, E., Bagger, J., Christoffersen, K., Jeppesen, E., Enckell, P. H., and Bloch, D.

Published
2002

19. Klimaforandringers betydning for søer

Author

Jeppesen, E., Christoffersen, K., Kamp-Nielsen, L., Landkildehus, F., Lauridsen, T. L., Kristensen, T. B., Liboriussen, L., Meerhoff, M., Pedersen, Asger Roer, Søndergaard, M., Søndergaard, M., Kronvang., B., Pejrup, M. og Sand-Jensen, K. (red.), Kronvang. B., Pejrup, and M. og Sand-Jensen, K.

Published
2006

21. Lakes

Author

Christoffersen, K., Jeppesen, E., Klitgaard, A. B., Rasch, M., and Caning, K. .

Published
2006

31. Lake Monitoring

Author

Christoffersen, K., Jeppesen, E., Caning, K., and Rasch, M.

Published
2000

32. Freshwater Studies

Author

Schierup, H., Christoffersen, K., Vadeboncoeur, Y., Landkildehus, F., Lauridsen, T. L., Jensen, J. P., Amsinck, S., Jeppesen, E., Caning, K., and Rasch, M.

Published
2000

34. Lake Investigations at Zackenberg

Author

Jeppesen, E., Christoffersen, K., Landkildehus, F., Arboe, N. H., Riget, F., Søndergaard, M., and Rasch, M.

Published
1999

35. Studies of Lepidurus arcticus

Author

Christoffersen, K., Arboe, N. H., Landkildehus, F., Jeppesen, E., Søndergaard, M., and Rasch, M.

Published
1999

36. Aquatic Organisms

Author

Christoffersen, K. S. and Christoffersen, K. S.

Abstract

The length of food chains and the complexity of food webs in aquatic systems are regulated by the productivity of the photosynthesizing organisms and the number of species within the ecosystem. Analyses of aquatic ecosystem structure and behavior have traditionally included most elements of the planktonic community such as bacteria, phytoplankton, zooplankton and fish populations, as well as the benthos. All these populations vary considerably in time and space. To understand the variability in population dynamics, it is necessary to understand the role of limiting biotic and abiotic factors as well as the potential interactions within populations inhabiting the aquatic ecosystem. The top-predator control can be very strong in certain systems and may induce cascading effects down the food chain. Fish are often the most conspicuous top predators in aquatic ecosystems. Methodological developments have greatly improved the ability to measure changes in population densities under more or less undisturbed conditions and thus provide scientists with valuable information for addressing important environmental questions such as the effect of climatic changes or the consequences of human resource exploitation.

Published
2008

37. Lake Studies

Author

Jeppesen, E., Christoffersen, K., Landkildehus, F., Meltofte, H., and Rasch, M.

Published
1998

41. Lakes

Author

Klitgaard, Anne B., Rasch, Morten, Caning, Kirsten, Christoffersen, K., Jeppesen, E., Klitgaard, Anne B., Rasch, Morten, Caning, Kirsten, Christoffersen, K., and Jeppesen, E.

Published
2006

42. Klimaforandringers betydning for søer

Author

Søndergaard, Morten, Kronvang, Brian, Pejrup, Morten, Sand-Jensen, Kai, Jeppesen, E., Boll, T., Christoffersen, K. S., Nielsen, L. K., Landkildehus, F., Liberiussen, L., Meerhoff, M., Pedersen, A. R., Søndergaard, M., Søndergaard, Morten, Kronvang, Brian, Pejrup, Morten, Sand-Jensen, Kai, Jeppesen, E., Boll, T., Christoffersen, K. S., Nielsen, L. K., Landkildehus, F., Liberiussen, L., Meerhoff, M., Pedersen, A. R., and Søndergaard, M.

Published
2006

43. Influence of filtration and glucose amendment on bacterial growth rate at different tidal conditions in the Minho Estuary River (NW Portugal)

Author

Anne, I., Fidalgo, M. L., Thosthrup, L., Christoffersen, K., Anne, I., Fidalgo, M. L., Thosthrup, L., and Christoffersen, K.

Abstract

Bacterioplankton abundance, biomass and growth rates were studied in the Minho Estuary River (NW Portugal). The influence of tidal conditions, glucose amendment, and the filtration process on total bacterial abundance, total and faecal coliforms, as well as faecal streptococci, were evaluated in laboratory incubation experiments. Physical and chemical conditions, as well as bacterial abundance in this estuary were found to be typical for oligo-mesotrophic coastal ecosystems. Bacterial abundance was higher at high tide, probably due to hydrodynamics and resuspension of bacteria from sediments. In contrast, a significant decrease of bacterial indicators of faecal pollution at high tide was probably the result of various causes, such as the decrease of continental and agriculturalland mn-off effect by dilution, aml/or increase in the abundance of potential specific predators. Thus, drastic changes were induced at high tide that led to a lack of bacterial growth and the net disappearance of most of the bacterial populations. Glucose amendment, at used concentration, was not found to stimulate bacterial growth, which instead could be limited by inorganic nutrients.

Published
2006

44. Lake depth rather than fish planktivory determines cladoceran community structure in Faroese lakes - evidence from contemporary data and sediments

Author

Amsinck, S.L., Strzelczak, A., Bjerring, R., Landkildehus, F., Lauridsen, T. L., Christoffersen, K., Jeppesen, E., Amsinck, S.L., Strzelczak, A., Bjerring, R., Landkildehus, F., Lauridsen, T. L., Christoffersen, K., and Jeppesen, E.

Abstract

Udgivelsesdato: November 2006, 1. This study describes the environmental conditions and cladoceran community structure of 29 Faroese lakes with special focus on elucidating the impact of fish planktivory. In addition, long-term changes in biological structure of the Faroese Lake Heygsvatn are investigated.2. Present-day species richness and community structure of cladocerans were identified from pelagial snapshot samples and from samples of surface sediment (0-1 cm). Multivariate statistical methods were applied to explore cladoceran species distribution relative to measured environmental variables. For Lake Heygsvatn, lake development was inferred by cladoceran-based paleolimnological investigations of a 14C-dated sediment core covering the last ca 5700 years.3. The 29 study lakes were overall shallow, small-sized, oligotrophic and dominated by brown trout (Salmo trutta). Cladoceran species richness was overall higher in the surface sediment samples than in the snapshot samples.4. Fish abundance was found to be of only minor importance in shaping cladoceran community and body size structure, presumably because of predominance of the less efficient zooplanktivore brown trout.5. Canonical correspondence analysis showed maximum lake depth (Zmax) to be the only significant variable in explaining the sedimentary cladoceran species (18 cladoceran taxa, two pelagic, 16 benthic) distribution. Multivariate regression trees revealed benthic taxa to dominate in lakes with Zmax < 4.8 m and pelagic taxa to dominate when Zmax was > 4.8 m.6. Predictive models to infer Zmax were developed using variance weighted-averaging procedures. These were subsequently applied to subfossil cladoceran assemblages identified from a 14C-dated sediment core from Lake Heygsvatn and showed inferred Zmax to correspond well to the present-day lake depth. A recent increase in inferred Zmax may, however

Published
2006

48. Lakes

Author

Christoffersen, K., Jeppesen, E., Christoffersen, K., and Jeppesen, E.

Published
2005

49. Frequency of inhibitors of daphnid trypsin in the widely distributed cyanobacterial genus Planktothrix

Author

Rohrlack, T., Christoffersen, K., Friberg-Jensen, U., Rohrlack, T., Christoffersen, K., and Friberg-Jensen, U.

Abstract

Udgivelsesdato: October 2005, Recent findings showed that inhibition of the digestive enzyme trypsin by cyanobacterial metabolites can result in the death of the microcrustacean Daphnia. Compounds that are active against daphnid trypsin can therefore be considered as potentially toxic to Daphnia. Here we reported on the frequency of such compounds in the widely distributed cyanobacterial genus Planktothrix. Of the 89 Planktothrix strains analysed, about 70% produced inhibitors of daphnid trypsin. The strains tested positive represented three common Planktothrix species and were isolated from diverse localities and geographical regions. Our findings suggest therefore that inhibitors of daphnid trypsin are common in Planktothrix and maybe other cyanobacterial genera. These compounds should therefore be considered in future studies on the chemical ecology of cyanobacteria.

Published
2005

50. Ingestion of microcystins by Daphnia: Intestinal uptake and toxic effects

Author

Rohrlack, T., Christoffersen, K., Dittmann, E., Nogueira, I., Vasconcelos, V., Börner, T., Rohrlack, T., Christoffersen, K., Dittmann, E., Nogueira, I., Vasconcelos, V., and Börner, T.

Abstract

Udgivelsesdato: March 2005, We investigated the intestinal uptake and adverse effects of microcystins ingested with Microcystis on Daphnia galeata. The gut structure, blood microcystin concentration, appearance, and movements of Daphnia fed Microcystis PCC 7806 or a microcystin-deficient PCC 7806 mutant were monitored over time. Microcystins were rapidly taken up from the digestive cavity into the blood. This process apparently required a preceding disruption of the gut epithelium by an as-yet-unknown Microcystis factor. Once microcystins entered the blood, they affected the neuromuscular communication or another life function that influences major muscle systems. Consequently, the beat rates of the thoracic legs, mandibles, and second antennae as well as the activity of the foregut decreased, whereas the midgut muscles were stimulated. Finally, the animals exhibited symptoms of exhaustion and died. The present results suggest that an ingestion of between 10.2 ng and 18.3 ng of microcystin per 1 mg of Daphnia body fresh weight is sufficient to kill D. galeata within 2 d.

Published
2005

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