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- Baden, Susanne P., 1952, et al.
(författare)
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Gödning och överfiske förstör fiskens barnkammare
- 2005
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Ingår i: Miljöforskning för ett uthålligt samhälle: I havets dunkla djup. - 1650-4925. ; 4
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Nya resultat visar att övergödning och överfiske gynnar vissa faunagrupper så att alger kväver det viktiga ålgräset, som utgör barnkammare för torsk och abborre. Ålgräset har minskat med 60 procent på 20 år skriver Susanne P Baden och Per O Moksnes i artikeln Gödning och överfiske förstör fiskens barnkammare.
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- Dunca, Elena, et al.
(författare)
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Using ocean quahog (Arctica islandica) shells to reconstruct palaeoenvironment in A-resund, Kattegat and Skagerrak, Sweden
- 2009
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Ingår i: International Journal of Earth Sciences. - : Springer Science and Business Media LLC. - 1437-3254 .- 1437-3262. ; 98:1, s. 3-17
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Shells of Arctica islandica collected between 1884 and 2004 from A-resund, Kattegat and Skagerrak (Swedish West Coast) were used to monitor local climate variations and the influence of human activities on the local environment. For this purpose, we analysed the growth, structure and chemical composition of these shells and compared them with shells collected from Kiel Bay, Norway and Iceland. The growth rate of the studied shells registers an NAO periodicity of ca 8 years. However, the observed signal is weak because of other environmental interferences that are either of natural or anthropogenic origin. For example, the oxygen isotope ratios show temperature fluctuation, but also the influx of low salinity water. Higher contents of S, N, Cu, Zn, As, Cd and P in shell portions formed during the last century are related to human activities such as mining and industrial development. Our study indicates that in order to use Arctica shells as archives of climate change it is necessary to study the full range of environmental data that is recorded in the shells by using a multi element and isotope approach in combination with different analytical techniques including investigation of growth rates and shell structure.
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- Eklöf, Johan, 1978, et al.
(författare)
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Sjögräsängar - hotade av både övergödning och överfiske?
- 2009
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Ingår i: HavsUtsikt: Om svensk havsforskning och havets resurser. - 1104-0513. ; 1
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Sjögräsängar är viktiga som barnkammare för många fiskarter, men är hotade av människan genom bland annat övergödning. Nu visar resultat från forskning utförd av svenska forskare i Sverige och i Östafrika på att även överfiske av stora rovfiskar skulle kunna ge negativa effekter på sjögräset. Detta visar hur viktigt det är att man inom förvaltningen använder sig av en kombination av åtgärder när sjögräsängarna ska räddas.
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- Jephson, Therese, et al.
(författare)
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Trophic interactions in Zostera marina beds along the Swedish coast
- 2008
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Ingår i: Marine Ecology - Progress Series. - : Inter-Research Science Center. - 1616-1599 .- 0171-8630. ; 369, s. 63-76
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Tidskriftsartikel (refereegranskat)abstract
- We compared eelgrass Zostera marina communities in 3 regions in Sweden believed to be affected by eutrophication and overfishing, to determine whether bottom-up or top-down processes control the biomass of epiphytic macroalgae and grazers. Nitrogen and carbon isotope signatures were analyzed to explore the food webs and to identify the grazing species feeding on filamentous algae and/or eelgrass. Mixing model (IsoSource version 1.3.1) analysis of the isotope signatures indicated that the amphipods Gammarus locusta and Microdeutopus gryllotalpa fed primarily on filamentous algae and that only 2 small gastropod species consumed eelgrass. Moreover, the grass shrimp Palaemon elegans and F adspersus were ca. 1 trophic level above amphipods and algae, but according to the mixing model played different trophic roles in the different areas. The highest biomass of filamentous algae was found in the west coast beds housing grazers with the lowest biomass and mean size (predominantly G. locusta and M. gryllotalpa, 0.5 to 3 mm). In contrast, the Baltic Sea beds had low algal biomass, but the grazers (mostly G. locusta and Idotea baltica) had higher biomass and were significantly larger (mean size ca. 10 mm). An overall negative correlation was found between grazer biomass and biomass of filamentous algae. The significantly smaller grazers and absence of isopod grazers on the west coast may be due to substantial consumption by small predatory fish. This supports the suggestions that, in Swedish eelgrass beds, grazers are top-down controlled, and overexploitation. of large predators and eutrophication play an important role in the recent increases in algal biomass.
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- Moksnes, Per-Olav, 1965, et al.
(författare)
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Trophic cascades in a temperate seagrass community
- 2008
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 117:5, s. 763-777
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Tidskriftsartikel (refereegranskat)abstract
- We assessed the relative importance of bottom-up and top-down processes in structuring an eelgrass community in Sweden, a system impacted both by eutrophication and overfishing. Using artificial seagrass as substrate, we manipulated nutrient levels and predator abundance in a full-factorial cage-experiment. The results revealed a seagrass community dominated by strong top-down processes controlling the aggregate biomass of mesograzers and macroalgae. In the absence of predators the large amphipod Gammarus locusta became very abundant resulting in a leaf community with low biomass of algae and smaller mobile fauna. One enclosed gobid fish predator reduced the abundance of adult G. locusta by > 90%, causing a three to six times increase in the biomass of algae, smaller mesograzers and meiofauna. Numerous small predators in uncaged habitats reduced the biomass of G. locusta and other mesograzers by > 95% in comparison to the fish treatment, further increasing the biomass of epiphytic algae and meiofauna. Although water column nutrient enrichment caused a temporal bloom of the filamentous macroalgae Ulva spp., no significant nutrient-effects were found on the algal community at the end of the experiment. The only lasting nutrient-effect was a significant increase in the biomass of G. locusta, but only in the absence of ambient predators. These results demonstrate that mesograzers can respond to enhanced food supply, increase their biomass and control the algal growth when predation rates are low. However, in the assessed system, high predation rates appear to make mesograzers functionally extinct, causing a community-wide trophic cascade that promotes the growth of ephemeral algae. This top-down effect could penetrate down, despite a complex food-web because the interaction strength in the community was strongly skewed towards two functionally dominant algal and grazer species that were vulnerable to consumption. These results indicate that overexploitation of gadoid fish may be linked to increased macroalgal blooms and loss of eelgrass in the area through a trophic cascade affecting the abundance of mesograzers.
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