Marine Ecology Progress Series
MEPS is a leading hybrid research journal on all aspects of marine, coastal and estuarine ecology. Priority is given to outstanding research that advances our ecological understanding.
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DOI: https://doi.org/10.3354/meps12548
copiedEffects of the invasive red king crab on food web structure and ecosystem properties in an Atlantic fjord
- Torstein Pedersen
- Mona M. Fuhrmann
- Ulf Lindstrøm
- Einar M. Nilssen
- Trond Ivarjord
- Virginie Ramasco
- Lis L. Jørgensen
- Jan H. Sundet
- Knut Sivertsen
- Emma Källgren
- Ann Merete Hjelset
- Christer Michaelsen
- Geir Systad
- Fredrika Norrbin
- Martin-A. Svenning
- Arne Bjørge
- Henning Steen
- Kjell T. Nilssen
ABSTRACT: Since the 1990s, the density of the invasive red king crab Paralithodes camtschaticus has increased dramatically in coastal areas in northern Norway. We investigated its direct and indirect effects on food web structure and ecosystem properties (e.g. species biomasses and production) in the Porsanger Fjord in the study period 2009-2011 using 5 subarea Ecopath food web models. The 5 baseline models with different red king crab densities were compared and the food web effects of crab removal were explored through simulations in Ecosim. King crabs were important as benthic predators and exerted strong top-down effects on long-living invertebrates such as predatory gastropods, asteroids, detritivorous echinoderms and herbivorous sea urchins. The crab experienced little predation from fish or other predators at higher trophic levels, thus food web effects of the red king crab generally stayed within the benthic compartment. Red king crab removal decreased system omnivory and resulted in higher food web biomass-low turnover systems, with relatively lower production:biomass ratios of benthic invertebrates. Other ecosystem properties (e.g. total production, consumption, ascendancy and overhead) were little affected by crab abundance and suggest stable systems. Effects of crab removal were less significant in baseline models with low initial crab biomass, and high benthic production by detritivores in the inner fjord may buffer future predation in this area. Indirect effects of crab predation included a positive cascade effect on macroalgae due to predation on herbivorous sea urchins and a negative effect on benthic-feeding birds, indicating competition for invertebrate prey.
KEYWORDS
Torstein Pedersen (Corresponding Author)
- Department of Arctic and Marine Biology, UiT -The Arctic University of Norway, 9037 Tromsø, Norway
Mona M. Fuhrmann (Co-author)
- Department of Arctic and Marine Biology, UiT -The Arctic University of Norway, 9037 Tromsø, Norway
Ulf Lindstrøm (Co-author)
- Institute of Marine Research, 9294 Tromsø, Norway
Einar M. Nilssen (Co-author)
- Department of Arctic and Marine Biology, UiT -The Arctic University of Norway, 9037 Tromsø, Norway
Trond Ivarjord (Co-author)
- Department of Arctic and Marine Biology, UiT -The Arctic University of Norway, 9037 Tromsø, Norway
Virginie Ramasco (Co-author)
- Institute of Marine Research, 9294 Tromsø, Norway
Lis L. Jørgensen (Co-author)
- Institute of Marine Research, 9294 Tromsø, Norway
Jan H. Sundet (Co-author)
- Institute of Marine Research, 9294 Tromsø, Norway
Knut Sivertsen (Co-author)
- Department of Arctic and Marine Biology, UiT -The Arctic University of Norway, 9037 Tromsø, Norway
Emma Källgren (Co-author)
- Department of Arctic and Marine Biology, UiT -The Arctic University of Norway, 9037 Tromsø, Norway
Ann Merete Hjelset (Co-author)
- Institute of Marine Research, 9294 Tromsø, Norway
Christer Michaelsen (Co-author)
- Department of Arctic and Marine Biology, UiT -The Arctic University of Norway, 9037 Tromsø, Norway
Geir Systad (Co-author)
- Bergen Department, Norwegian Institute for Nature Research, 5008 Bergen, Norway
Fredrika Norrbin (Co-author)
- Department of Arctic and Marine Biology, UiT -The Arctic University of Norway, 9037 Tromsø, Norway
Martin-A. Svenning (Co-author)
- Department of Arctic Ecology, Fram Center, Norwegian Institute for Nature Research (NINA), 9296 Tromsø, Norway
Arne Bjørge (Co-author)
- Institute of Marine Research, 9294 Tromsø, Norway
Henning Steen (Co-author)
- Institute of Marine Research, 9294 Tromsø, Norway
Kjell T. Nilssen (Co-author)
- Institute of Marine Research, 9294 Tromsø, Norway