| 1. |
- Bergström, Ulf, et al.
(författare)
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Skydda och vårda våra viktiga vikar
- 2015
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Annan publikation (populärvet., debatt m.m.)abstract
- Grunda kustnära havsvikar har ett högt ekologiskt värde. De har ofta en rik bottenvegetation och är viktiga uppväxtmiljöer för flera fiskarter i Östersjön. Samtidigt är exploateringstrycket på dessa miljöer stort. Vi människor vistas gärna nära havet och det är många som vill nyttja kusten. Genom strandexploatering och hög näringsbelastning påverkas dessa miljöer negativt, vilket kan få långtgående effekter på kustens ekosystem och ekosystemtjänster. Naturvärden nära kusten behöver därför inkluderas i planering och förvaltning, i större utsträckning än idag. För att långsiktigt trygga värdena kan områdesskydd och restaurering vara aktuella. Här presenteras några förslag på hur vi kan vårda dessa grunda havsvikar
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| 2. |
- Dahlgren, Kristin, et al.
(författare)
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Algblomning vad är det?
- 2016
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Rapport (populärvet., debatt m.m.)abstract
- När växtplankton förekommer i stor mängd talar man om algblomning. Vattnet grumlas, ändrar färg och algerna bildar ofta ett lager på vattenytan. Lagrets tjocklek varierar beroende på hur kraftigt algerna blommar. Algmassan kan vara giftig och därför bör du undvika att bada under tiden som algblomningen pågår. Potentiellt giftiga alger kan också tas upp och lagras i blåmusslor vilket kan vara en hälsorisk främst på västkusten.
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| 3. |
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| 4. |
- Eriksson, Britas Klemens, et al.
(författare)
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Declines in predatory fish promote bloom-forming macroalgae.
- 2009
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Ingår i: Ecological Applications. - 1051-0761 .- 1939-5582. ; 19:8, s. 1975-1988
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Tidskriftsartikel (refereegranskat)abstract
- In the Baltic Sea, increased dominance of ephemeral and bloom-forming algae is presently attributed to increased nutrient loads. Simultaneously, coastal predatory fish are in strong decline. Using field data from nine areas covering a 700-km coastline, we examined whether formation of macroalgal blooms could be linked to the composition of the fish community. We then tested whether predator or nutrient availability could explain the field patterns in two small-scale field experiments, by comparing joint effects on algal net production from nutrient enrichment with agricultural fertilizer and exclusion of larger predatory fish with cages. We also manipulated the presence of invertebrate grazers. The abundance of piscivorous fish had a strong negative correlation with the large-scale distribution of bloom-forming macroalgae. Areas with depleted top-predator communities displayed massive increases in their prey, small-bodied fish, and high covers of ephemeral algae. Combining the results from the two experiments showed that excluding larger piscivorous fish: (1) increased the abundance of small-bodied predatory fish; (2) changed the size distribution of the dominating grazers, decreasing the smaller gastropod scrapers; and (3) increased the net production of ephemeral macroalgae. Effects of removing top predators and nutrient enrichment were similar and additive, together increasing the abundance of ephemeral algae many times. Predator effects depended on invertebrate grazers; in the absence of invertebrates there were no significant effects of predator exclusion on algal production. Our results provide strong support for regional declines of larger predatory fish in the Baltic Sea promoting algal production by decreasing invertebrate grazer control. This highlights the importance of trophic interactions for ecosystem responses to eutrophication. The view emerges that to achieve management goals for water quality we need to consider the interplay between top-down and bottom-up processes in future ecosystem management of marine resources.
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| 5. |
- Eriksson, Britas Klemens, et al.
(författare)
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Omnivory and grazer functional composition moderate cascading trophic effects in experimental Fucus vesiculosus habitats
- 2011
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Ingår i: Marine Biology. - : Springer Science and Business Media LLC. - 0025-3162 .- 1432-1793. ; 158:4, s. 747-756
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Tidskriftsartikel (refereegranskat)abstract
- We tested the relative strength of direct versus indirect effects of an aquatic omnivore depending on the functional composition of grazers by manipulating the presence of gastropod and amphipod grazers and omnivorous shrimp in outdoor mesocosms. By selectively preying upon amphipods and reducing their abundance by 70-80%, omnivorous shrimp favoured the dominance of gastropods. While gastropods were the main microalgal grazers, amphipods controlled macroalgal biomass in the experiment. However, strong predation on the amphipod by the shrimp had no significant indirect effects on macroalgal biomass, indicating that when amphipod abundances declined, complementary feeding by the omnivore on macroalgae may have suppressed a trophic cascade. Accordingly, in the absence of amphipods, the shrimp grazed significantly on green algae and thereby suppressed the diversity of the macroalgal community. Our experiment demonstrates direct consumer effects by an omnivore on both the grazer and producer trophic levels in an aquatic food web, regulated by prey availability.
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| 6. |
- Johannesson, Kerstin, 1955, et al.
(författare)
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Phenotypic variation in sexually and asexually recruited individuals of the Baltic Sea endemic macroalga Fucus radicans : in the field and after growth in a common-garden
- 2012
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Ingår i: BMC Ecology. - : Springer Science and Business Media LLC. - 1472-6785. ; 12, s. 2-
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Most species of brown macroalgae recruit exclusively sexually. However, Fucus radicans, a dominant species in the northern Baltic Sea, recruits new attached thalli both sexually and asexually. The level of asexual recruitment varies among populations from complete sexual recruitment to almost (> 90%) monoclonal populations. If phenotypic traits have substantial inherited variation, low levels of sexual activity will decrease population variation in these traits, which may affect function and resilience of the species. We assessed the level of inherited variation in nine phenotypic traits by comparing variation within and among three monoclonal groups and one group of unique multilocus genotypes (MLGs) sampled in the wild.RESULTS: Of the nine phenotypic traits, recovery after freezing, recovery after desiccation, and phlorotannin content showed substantial inherited variation, that is, phenotypic variation in these traits were to a large extend genetically determined. In contrast, variation in six other phenotypic traits (growth rate, palatability to isopod grazers, thallus width, distance between dichotomies, water content after desiccation and photochemical yield under ambient conditions) did not show significant signals of genetic variation at the power of analyses used in the study. Averaged over all nine traits, phenotypic variation within monoclonal groups was only 68% of the variation within the group of different MLGs showing that genotype diversity does affect the overall level of phenotypic variation in this species.CONCLUSIONS: Our result indicates that, in general, phenotypic diversity in populations of Fucus radicans increases with increased multilocus genotype (MLG) diversity, but effects are specific for individual traits. In the light of Fucus radicans being a foundation species of the northern Baltic Sea, we propose that increased MLG diversity (leading to increased trait variation) will promote ecosystem function and resilience in areas where F. radicans is common, but this suggestion needs experimental support.
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| 7. |
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| 8. |
- Råberg, Sonja, et al.
(författare)
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A comparative biodiversity study of the associated fauna of perennial fucoids and filamentous algae
- 2007
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Ingår i: Estuarine, coastal and shelf science. - : Elsevier BV. - 0272-7714. ; 73, s. 249-258
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Tidskriftsartikel (refereegranskat)abstract
- Anthropogenic activities worldwide have contributed to vegetation changes in many coastal areas, changes that may in turn affect faunal and algal assemblages in the involved ecosystems. In the northernmost part of the Baltic Sea the salinity is extremely low (3–4) and the only structurally complex alga present is Fucus radicans. Since in this area F. radicans is living at its salinity tolerance limit, it is potentially very sensitive to environmental changes. Any change in salinity could thus alter the overall algal community, changing it to one dominated solely by filamentous algae. To determine the importance of F. radicans to the associated faunal community, we examined differences between the two main vegetation types present, i.e., F. radicans and filamentous algae, in the Kronören marine reserve in the northernmost part of the Baltic Sea. A similar study was conducted in the Askö area in the northern Baltic Proper, where the more-investigated F. vesiculosus is the only large fucoid present. The biomass of associated fauna was significantly higher in both the F. radicans and F. vesiculosus than in the filamentous algal vegetation at some, but not all, sites. The F. radicans community also displayed a greater diversity of associated fauna in 3 of 5 investigated Kronören sites, whereas no difference in diversity was detected between F. vesiculosus and the filamentous algal vegetations in the Askö sites. Furthermore, the F. radicans community displayed a different faunal community, being the only investigated algal community with a faunal community dominated by K-strategy species, according to abundance–biomass comparison curves. This pattern may be due to the low epiphytic load on these Fucus plants. In contrast, the F. vesiculosus community, as well as the algal communities with no Fucus in both areas, had high biomasses of filamentous algae and an invertebrate fauna dominated by Chironomidae, occurring in great abundance but only a low biomass. ANOSIM analyses of faunal composition demonstrated a significant difference between the two vegetation types in both areas, largely due to greater abundance of Gammarus spp. and Theodoxus fluviatilis in the fucoid vegetation. Differences observed between the F. radicans and filamentous algal vegetation types were generally more pronounced than those between F. vesiculosus and nearby filamentous algal vegetation. These observations may be due to abiotic factors that differ between the two investigated areas, factors such as depth distribution, wave action and eutrophication level. This study has demonstrated that the less-investigated F. radicans may be as important as the larger F. vesiculosus for the associated faunal assemblages. At the same time, the limited extent of F. radicans at shallower depths makes F. radicans vegetation potentially more vulnerable to anthropogenic changes, as declines in fucoid vegetation are usually first manifested in populations at their lower depth limits, whereas shallow populations are less affected.
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| 9. |
- Råberg, Sonja, et al.
(författare)
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Consumers affect prey biomass and diversity through resource partitioning
- 2007
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Ingår i: Ecology: Reports. - : Wiley. - 0012-9658. ; 88:10, s. 2468-2473
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Tidskriftsartikel (refereegranskat)abstract
- Consumer presence and nutrient availability can have contrasting and interactive effects on plant diversity. In a factorial experiment, we manipulated two levels of nutrient supply and the presence of two moderately specialized grazers in different combinations (no grazers, two species in monoculture, and both in combination). We tested how nutrients and grazers regulated the biomass of marine coastal epiphytes and the diversity of algal assemblages, based on the prediction that the effect of consumers on prey diversity depends on productivity and consumer specialization. Nutrient enrichment increased the epiphytic load while monocultures of single grazer species partly prevented epiphyte growth. However, only the presence of two species with complementary feeding preferences effectively prevented epiphyte overgrowth.The epiphytes comprised micro- and macroalgal species and the diversity of these algal assemblages differed depending on grazer identity. For the microalgae, diversity was reduced by nutrient addition when grazer control was inefficient, but not when specialist microalgal grazers were present. Macroalgal diversity was reduced in ambient water with specialist macroalgal grazers compared to the treatment with inefficient ones. These results indicate that grazer composition and productivity are crucial in determining whether consumer pressure will have a positive or negative effect on algal diversity.
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| 10. |
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