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Göteborgs universitets publikationer

Shift in seagrass food web structure over decades is linked to overfishing

Författare och institution:
Susanne P. Baden (Institutionen för biologi och miljövetenskap); Andreas Emanuelsson (Institutionen för biologi och miljövetenskap); Leif Pihl (Institutionen för biologi och miljövetenskap); Carl Johan Svensson (Institutionen för biologi och miljövetenskap); Per Åberg (Institutionen för biologi och miljövetenskap)
Publicerad i:
Marine Ecology-Progress Series, 451 s. 61-73
Artikel, refereegranskad vetenskaplig
Sammanfattning (abstract):
Empirical field studies in seagrass have revealed that overgrowth by filamentous algae which reduces seagrass growth can be explained by a top-down cascading effect caused by declines in top predators, which is enforced by eutrophication. On the Swedish west coast, 60% of the seagrass has disappeared since the 1980s. We hypothesised that overfishing, responsible for a >90% decline in the cod stock, and the 4 to 8 times increase in nutrient load since the 1930s have altered the seagrass structure and function during recent decades. We used quantitative samples from the 1980s and 2000s and analysed the trends in abundance of the 4 feeding guilds: top predatory fish, intermediate predatory fish, crustacean omnivores and mesoherbivores. Since the 1980s, the commercial catch of gadoids on the Swedish west coast has decreased by >90 %, and here we found that the biomass of top predators (gadoids and trout) that forage in seagrass has decreased by approximately 80%. In contrast, the biomass of intermediate predatory fish (gobids and sticklebacks) has increased 8 times during summer and 11 times during autumn, while mesoherbivores (idoteids and gammarids >7 mm) have more or less disappeared from the seagrass bed. We thus found clear evidence that a shift in seagrass food web structure has taken place over the last 3 decades. Combining these findings with our recent empirical results from field cage experiments in the Skagerrak seagrass, where we manipulate top-down and bottom-up regulation, we conclude that lack of grazers in concert with eutrophication most likely contributed to the overgrowth by filamentous algae and disappearance of the seagrass on the Swedish west coast.
Ämne (baseras på Högskoleverkets indelning av forskningsämnen):
Geovetenskap och miljövetenskap ->
Oceanografi, hydrologi, vattenresurser ->
Biologiska vetenskaper
Biologiska vetenskaper ->
Biologiska vetenskaper ->
Ekologi ->
Marin ekologi
Food web structure, Overfishing, Eutrophication, Seagrass, zostera-marina l, trophic cascades, assemblage structure, nutrient, enrichment, coastal ecosystems, eastern skagerrak, epibenthic fauna, western sweden, baltic sea, low-oxygen
Postens nummer:
Posten skapad:
2012-06-19 11:43
Posten ändrad:
2014-04-12 16:24

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