Estuaries and Coasts

, Volume 35, Issue 3, pp 701–713 | Cite as

From Fish to Jellyfish in the Eutrophicated Limfjorden (Denmark)

  • Hans Ulrik RiisgårdEmail author
  • Per Andersen
  • Erik Hoffmann


The heavily eutrophicated Limfjorden (Denmark) provides a good illustration of the value of long-term monitoring, especially if this is combined with an experimental, interdisciplinary research approach. Here, we first give a short overview of the environmental status of Limfjorden, including the historical development of nutrient overloading and subsequent oxygen depletion in near-bottom water, and how the annual landings of edible bottom-dwelling fish species (plaice, flounder, eel and others) caught in Limfjorden have decreased from about 2,500 t in the early 1920s to only about 20 t in recent years where the fish have been replaced by an increasing number of especially the moon jellyfish, Aurelia aurita, which mainly preys on zooplankton. Next, we evaluate the ecological consequences of the present high number of jellyfish, based on data from recent years’ research on the abundance of jellyfish, their population dynamics and predation impact. In Limfjorden, the benthic polyp stage of A. aurita ensures a large number of small ephyrae in the early spring and subsequently a large population of adult medusae that control the zooplankton during summer and autumn. The holopelagic invasive ctenophore Mnemiopsis leidyi, which was observed in Limfjorden for the first time in 2007, is a second carnivore adding additional predation pressure of the indigenous A. aurita so that copepods and other mesozooplankton organisms may be virtually absent, as observed in 2008 and 2009 where ciliates made up a substantial part of the zooplankton biomass. Marine environmental management programmes should be aware of the increasing importance of both indigenous and new invasive jellyfish species that may show mass occurrence in especially eutrophicated and over-fished areas.


Jellyfish Eutrophication Case story Oxygen depletion Limfjorden Fish Shellfish 



Thanks are due to the Environment Centre Ringkøbing, Danish Ministry of the Environment, for excellent co-operation, and to an anonymous reviewer for constructive comments on the manuscript. The study was supported by a grant from FNU, the Danish Agency for Science Technology and Innovation (H. U. Riisgård, grant no. 09–073291).


  1. Andersen, J.H., and D.J. Conley. 2009. Eutrophication in coastal marine ecosystems: towards better understanding and management strategies. Hydrogiologia 629: 1–4.CrossRefGoogle Scholar
  2. Arai, M.N. 2001. Pelagic coelenterates and eutrophication: a review. Hydrobiologia 451: 69–87.CrossRefGoogle Scholar
  3. Asmus, R., and H. Asmus. 1991. Mussel beds: limiting or promoting phytoplankton? Journal of Experimental Marine Biology and Ecology 148: 215–232.CrossRefGoogle Scholar
  4. Baker, L.D., and M.R. Reeve. 1974. Laboratory culture of the lobate ctenophore Mnemiopsis mccradyi with notes on feeding and fecundity. Marine Biology 26: 57–62.CrossRefGoogle Scholar
  5. Behrends, G., and G. Schneider. 1995. Impact of Aurelia aurita medusae (Cnidaria, Schyphozoa) on the standing stock and community composition of mezozooplankton in the Kiel Bight (western Baltic Sea). Marine Ecology Progress Series 127: 39–45.CrossRefGoogle Scholar
  6. Bioconsult. 2001. Fiskelarver og gopler i Limfjorden, foråret 1996–1999. (Report in Danish produced for Limfjordssamarbejdet, v/Nordjyllandsamt, Aalborg, Denmark).Google Scholar
  7. Boero, F., J. Bouillon, C. Gravili, M.P. Miglietta, T. Parsons, and S. Piraino. 2008. Gelatinous plankton: irregularities rule the world (sometimes). Marine Ecology Progress Series 356: 299–310.CrossRefGoogle Scholar
  8. Carstensen, J., D.J. Conley, J.H. Andersen, and G. Ærtebjerg. 2006. Coastal eutrophication and trend reversal: a Danish case study. Limnology and Oceanography 51: 398–408.CrossRefGoogle Scholar
  9. Christiansen, T., T. J. Christensen, S. Markager, J. K. Petersen, and L. T. Mouritsen. 2006. Limfjorden i 100 år. Klima, hydrografi, næringsstoftilførsel, bundfauna og fisk i Limfjorden fra 1897 til 2003. Danmarks Miljøundersøgelser. Faglig rapport fra DMU, nr. 578. (Report in Danish with English summary;
  10. Conley, D.J., H. Kaas, F. Møhlenberg, B. Rasmussen, and J. Windolf. 2000. Characteristics of Danish estuaries. Estuaries and Coasts 23: 820–837.CrossRefGoogle Scholar
  11. Conley, D.J., S. Markager, J. Andersen, et al. 2002. Coastal eutrophication and the Danish national aquatic monitoring and assessment program. Estuaries and Coasts 25: 848–861.CrossRefGoogle Scholar
  12. Diaz, R.J. 2001. Overview of hypoxia around the world. Journal of Environmental Quality 30: 275–281.CrossRefGoogle Scholar
  13. Dolmer, P., and R.P. Frandsen. 2002. Evaluation of the Danish mussel fishery: suggestions for an ecosystem management approach. Helgoland Marine Research 56: 13–20.CrossRefGoogle Scholar
  14. Dolmer, P., P.S. Kristensen, and E. Hoffmann. 1999. Dredging of blue mussels (Mytilus edulis L.) in a Danish sound: stock sizes and fishery-effects on mussel population dynamic. Fisheries Research 40: 73–80.CrossRefGoogle Scholar
  15. Frandsen, K.T., and H.U. Riisgård. 1997. Size dependent respiration and growth of jellyfish, Aurelia aurita. Sarsia 82: 307–312.Google Scholar
  16. Hansson, L.J., O. Moeslund, T. Kiørboe, and H.U. Riisgård. 2005. Clearance rates of jellyfish and their potential predation impact on zooplankton and fish larvae in a neritic ecosystem (Limfjorden, Denmark). Marine Ecology Progress Series 304: 117–131.CrossRefGoogle Scholar
  17. Hoffmann, E. 2005. Fisk, fiskeri og epifauna. Limfjorden 1984–2004. Danish Institute for Fisheries Research, no. 147–05, pp. 49 (Report in Danish).Google Scholar
  18. Hoffmann, E. 2008. Forsøgsfiskeri i Limfjorden 2008. Rapport til Limfjordsovervågningen. DTU-Aqua, December 2008, pp. 19 (Report in Danish).Google Scholar
  19. Hofmeister, R., H. Buchard, and K. Bolding. 2009. A three-dimensional model study on processes of stratification and de-stratification in the Limfjord. Continental Shelf Research 29: 1515–1524.CrossRefGoogle Scholar
  20. Jørgensen, B.B. 1980. Seasonal oxygen depletion in the bottom waters of a Danish fjord and its effect on the benthic community. Oikos 34: 68–76.CrossRefGoogle Scholar
  21. Jørgensen, B. B., and K. Richardson (eds.). 1996. Eutrophication in coastal marine ecosystems. Coastal and Estuarine Studies 52. Washington, D.C.: American Geophysical Union. pp. 173Google Scholar
  22. Limfjordsrådet. 2007. Bemærkninger og forslag til vandplan for Limfjorden (“comments and suggestions to water plan for Limfjorden”). Denmark: Nykøbing Mors Kommune.Google Scholar
  23. Markager, S., L. M. Storm, and C. A. Stedmon. 2006. Limfjordens miljøtilstand 1985 til 2003. Sammenhæng mellem næringsstoftilførsler, klima og hydrografi belyst ved hjælp af empiriske modeller. Danmarks Miljøundersøgelser. Faglig rapport fra DMU, nr. 577. (Report in Danish)
  24. Matsakis, S., and R.J. Conover. 1991. Abundance and feeding of medusae and their potential impact as predators on other zooplankton in Bedford Basin (Nova Scotia, Canada) during spring. Canadian Journal of Fisheries and Aquatic Sciences 48: 1419–1430.CrossRefGoogle Scholar
  25. Mills, C.E. 2001. Jellyfish blooms: are populations increasing globally in response to changing ocean conditions? Hydrobiologia 451: 55–68.CrossRefGoogle Scholar
  26. Møhlenberg, F. 1999. Effect of meteorology and nutrient load on oxygen depletion in a Danish micro-tidal estuary. Aquatic Ecology 33: 55–64.CrossRefGoogle Scholar
  27. Møhlenberg, F., S. Petersen, A.H. Petersen, and C. Gameiro. 2007. Long-term and short-term variability of water quality in Skive Fjord, Denmark—nutrient load and mussels are the primary pressures and drivers that influence water quality. Environmental Monitoring and Assessment 127: 503–521.CrossRefGoogle Scholar
  28. Möller, H. 1979. Significance of coelenterates in relation to other plankton organisms. Meeresforschung 27: 1–18.Google Scholar
  29. Møller, L.F., and H.U. Riisgård. 2007a. Population dynamics, growth and predation impact of the common jellyfish, Aurelia aurita and two hydromedusae (Sarsia tubulosa and Aequorea vitrina) in Limfjorden (Denmark). Marine Ecology Progress Series 346: 167–177.CrossRefGoogle Scholar
  30. Møller, L.F., and H.U. Riisgård. 2007b. Population dynamics, growth and predation impact of the common jellyfish, Aurelia aurita, and selected hydromedusae in Limfjorden (Denmark). Marine Ecology Progress Series 346: 145–165.Google Scholar
  31. Møller, L.F., and H.U. Riisgård. 2007c. Impact of jellyfish and mussels on algal blooms caused by seasonal oxygen depletion and nutrient release from the sediment in a Danish fjord. Journal of Experimental Marine Biology and Ecology 351: 92–105.CrossRefGoogle Scholar
  32. NOVANA. 2005. Vandmiljø i Limfjorden 2004. Limfjordsovervågningen, Ringkøbing Amt, Viborg Amt, Nordjyllands Amt, maj 2005 (Report in Danish)
  33. Olesen, N.J. 1995. Clearance potential of jellyfish Aurelia aurita and predation impact on zooplankton in a shallow cove. Marine Ecology Progress Series 124: 63–72.CrossRefGoogle Scholar
  34. Olesen, N.J., K. Frandsen, and H.U. Riisgård. 1994. Population dynamics, growth and energetics of jellyfish Aurelia aurita in a shallow fjord. Marine Ecology Progress Series 105: 9–18.CrossRefGoogle Scholar
  35. Purcell, J.E., D.L. Breitburg, M.B. Decker, W.M. Graham, M.J. Youngbluth, and K.A. Raskoff. 2001a. Pelagic cnidarians and ctenophores in low dissolved oxygen environments: a review. In Coastal hypoxia: consequences for living resources and ecosystems. In Coastal and Estuarine Studies 58, ed. N.N. Rabalais and R.E. Turner, 77–100. Washington: American Geophysical Union.Google Scholar
  36. Purcell, J.E., T.A. Shiganova, M.B. Decker, and E.D. Houde. 2001b. The ctenophore Mnemiopsis in native and exotic habitats: U.S. estuaries versus the Black Sea basin. Hydrobiologia 451: 145–176.CrossRefGoogle Scholar
  37. Purcell, J.E., S. Uye, and W.-T. Lo. 2007. Antropogenic causes of jellyfish blooms and their direct consequences for humans: a review. Marine Ecology Progress Series 350: 153–174.CrossRefGoogle Scholar
  38. Rask, N., S.E. Pedersen, and M.H. Jensen. 1999. Response to lowered nutrient discharges in the coastal waters around the island of Funen, Denmark. Hydrobiologia 393: 69–81.CrossRefGoogle Scholar
  39. Richardson, K. 1996. Conclusion, research and eutrophication control. In Eutrophication in coastal marine ecosystems. In Coastal and Estuarine Studies 52, ed. B.B. Jørgensen and K. Richardson, 243–267. Washington: American Geophysical Union.Google Scholar
  40. Richardson, A.J., A. Bakun, G.C. Hays, and M.J. Gibbons. 2009. The jellyfish joyride: causes, consequences and management responses to a more gelatinous future. Trends in Ecology & Evolution 24: 312–322.CrossRefGoogle Scholar
  41. Riisgård, H.U. 1998. Filter feeding and plankton dynamics in a Danish fjord: A review of the importance of flow, mixing, and density-driven circulation. Journal of Environmental Management 53: 195–207.CrossRefGoogle Scholar
  42. Riisgård, H.U. 2007. Feeding behaviour of the hydromedusa Aequorea vitrina. Scientia Marina 71: 395–404.Google Scholar
  43. Riisgård, H.U., and E. Poulsen. 1981. Growth of Mytilus edulis in net bags transferred to different localities in an eutrophicated Danish fjord. Marine Pollution Bulletin 12: 272–276.CrossRefGoogle Scholar
  44. Riisgård, H.U., D.F. Seerup, M.H. Hjort, E. Glob, and P.S. Larsen. 2004. Grazing impact of filter-feeding zoobenthos in a Danish fjord. Journal of Experimental Marine Biology and Ecology 307: 261–271.CrossRefGoogle Scholar
  45. Riisgård, H.U., L. Bøttiger, C.V. Madsen, and J.E. Purcell. 2007. Invasive ctenophore Mnemiopsis leidyi in Limfjorden (Denmark) in late summer 2007—assessment of abundance and predation impact. Aquatic Invasions 2: 395–401.CrossRefGoogle Scholar
  46. Riisgård, H.U., C. Barth-Jensen, and C.V. Madsen. 2010. High abundance of the jellyfish Aurelia aurita excludes the invasive ctenophore Mnemiopsis leidyi to establish in a shallow cove (Kertinge Nor, Denmark). Aquatic Invasions 5: 347–356.CrossRefGoogle Scholar
  47. Riisgård, H.U., C.V. Madsen, C. Barth, and J. Purcell. 2012. Population dynamics and zooplankton-predation impact of the indigenous scyphozoan Aurelia aurita and the invasive ctenophore Mnemiopsis leidyi in Limfjorden (Denmark). Aquatic Invasions 7(2): in press. doi: 10.3391/ai.2011.accepted.
  48. Rosenberg, R., L.-O. Loo, and P. Möller. 1992. Hypoxia, salinity and temperature as structuring factors for marine benthic communities in a eutrophic area. Netherlands Journal of Sea Research 30: 121–129.CrossRefGoogle Scholar
  49. Rutherford, L.D., and E.V. Thuesen. 2005. Metabolic performance and survival of medusae in estuarine hypoxia. Marine Ecology Progress Series 294: 189–200.CrossRefGoogle Scholar
  50. Sand-Jensen, K., S. L. Nielsen, J. Borum, and O. Geertz-Hansen. 1994. Fytoplankton—og makrofytudviklingen i danske kystområder (“Phytoplankton and macrophyte development in Danish coastal waters”). Havforskning fra Miljøstyrelsen nr. 30, Miljøministeriet, Copenhagen (in Danish with English summary).Google Scholar
  51. Vahtera, E., D.J. Conley, B.G. Gustafson, H. Kuosa, H. Pitkänen, O.P. Savchuck, T. Tamminen, M. Viitasalo, M. Voss, N. Wasmund, and F. Wulff. 2007. Internal ecosystem feedbacks enhance nitrogen-fixing cyanobacteria blooms and complicate management in the Baltic Sea. Ambio 36: 186–194.CrossRefGoogle Scholar
  52. Wiles, P., L.A. van Duren, C. Häse, J. Larsen, and J.H. Simpson. 2006. Stratification and mixing in the Limfjorden in relation to mussel culture. Journal of Marine Systems 60: 129–143.CrossRefGoogle Scholar
  53. Zervoudaki, S., T.G. Nielsen, and J. Carstensen. 2009. Seasonal succession and composition of the zooplankton community along an eutrophication and salinity gradient exemplified by Danish waters. Journal of Plankton Research 31: 1475–1492.Google Scholar

Copyright information

© Coastal and Estuarine Research Federation 2012

Authors and Affiliations

  • Hans Ulrik Riisgård
    • 1
    Email author
  • Per Andersen
    • 2
  • Erik Hoffmann
    • 3
  1. 1.Marine Biological Research CentreUniversity of Southern DenmarkKertemindeDenmark
  2. 2.Orbicon A/SViby JDenmark
  3. 3.DTU-Aqua, National Institute of Aquatic ResourcesTechnical University of DenmarkCharlottenlundDenmark

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