TY - JOUR

T1 - From fish to jellyfish in the eutrophicated Limfjorden (Denmark)

A1 - Riisgård,Hans Ulrik

A1 - Andersen,Per

A1 - Hoffmann,Erik

AU - Riisgård,Hans Ulrik

AU - Andersen,Per

AU - Hoffmann,Erik

PB - Springer New York LLC

PY - 2012

Y1 - 2012

N2 - The heavily eutrophicated Limfjorden (Denmark) <br/>provides a good illustration of the value of long-term monitoring, <br/>especially if this is combined with an experimental, <br/>interdisciplinary research approach. Here, we first give a short <br/>overview of the environmental status of Limfjorden, including <br/>the historical development of nutrient overloading and subsequent <br/>oxygen depletion in near-bottom water, and how the <br/>annual landings of edible bottom-dwelling fish species <br/>(plaice, flounder, eel and others) caught in Limfjorden have <br/>decreased from about 2,500 t in the early 1920s to only about <br/>20 t in recent years where the fish have been replaced by an <br/>increasing number of especially the moon jellyfish, Aurelia <br/>aurita, which mainly preys on zooplankton. Next, we evaluate <br/>the ecological consequences of the present high number of <br/>jellyfish, based on data from recent years’ research on the <br/>abundance of jellyfish, their population dynamics and predation <br/>impact. In Limfjorden, the benthic polyp stage of A. <br/>aurita ensures a large number of small ephyrae in the early <br/>spring and subsequently a large population of adult medusae <br/>that control the zooplankton during summer and autumn. The <br/>holopelagic invasive ctenophore Mnemiopsis leidyi, which <br/>was observed in Limfjorden for the first time in 2007, is a <br/>second carnivore adding additional predation pressure of the <br/>indigenous A. aurita so that copepods and other mesozooplankton <br/>organisms may be virtually absent, as observed in <br/>2008 and 2009 where ciliates made up a substantial part of the <br/>zooplankton biomass. Marine environmental management <br/>programmes should be aware of the increasing importance <br/>of both indigenous and new invasive jellyfish species that may <br/>show mass occurrence in especially eutrophicated and overfished <br/>areas

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

U2 - 10.1007/s12237-012-9480-4

DO - 10.1007/s12237-012-9480-4

JO - Estuaries and Coasts

JF - Estuaries and Coasts

SN - 1559-2723

IS - 3

VL - 35

SP - 701

EP - 713

ER -