| 1. |
- Donadi, Serena, et al.
(författare)
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Density-dependent positive feedbacks buffer aquatic plants from interactive effects of eutrophication and predator loss
- 2018
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Ingår i: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 99:11, s. 2515-2524
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Tidskriftsartikel (refereegranskat)abstract
- Self-facilitation allows populations to persist under disturbance by ameliorating experienced stress. In coastal ecosystems, eutrophication and declines of large predatory fish are two common disturbances that can synergistically impact habitat-forming plants by benefitting ephemeral algae. In theory, density-dependent intraspecific plant facilitation could weaken such effects by ameliorating the amount of experienced stress. Here, we tested whether and how shoot density of a common aquatic plant (Myriophyllum spicatum) alters the response of individual plants to eutrophication and exclusion of large predatory fish, using a 12-week cage experiment in the field. Results showed that high plant density benefitted individual plant performance, but only when the two stressors were combined. Epiphytic algal biomass per plant more than doubled in cages that excluded large predatory fish, indicative of a trophic cascade. Moreover, in this treatment, individual shoot biomass, as well as number of branches, increased with density when nutrients were added, but decreased with density at ambient nutrient levels. In contrast, in open cages that large predatory fish could access, epiphytic algal biomass was low and individual plant biomass and number of branches were unaffected by plant density and eutrophication. Plant performance generally decreased under fertilization, suggesting stressful conditions. Together, these results suggest that intraspecific plant facilitation occurred only when large fish exclusion (causing high epiphyte load) was accompanied by fertilization, and that intraspecific competition instead prevailed when no nutrients were added. As coastal ecosystems are increasingly exposed to multiple and often interacting stressors such as eutrophication and declines of large predatory fish, maintaining high plant density is important for ecosystem-based management.
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| 2. |
- Donadi, Serena, et al.
(författare)
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The body-size structure of macrobenthos changes predictably along gradients of hydrodynamic stress and organic enrichment
- 2015
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Ingår i: Marine Biology. - : Springer Science and Business Media LLC. - 0025-3162 .- 1432-1793. ; 162:3, s. 675-685
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Tidskriftsartikel (refereegranskat)abstract
- Body size is related to an extensive number of species traits and ecological processes and has therefore been suggested as an effective metric to assess community changes and ecosystem's state. However, the applicability of body size as an ecological indicator in benthic environments has been hindered by the poor knowledge of the factors influencing the size spectra of organisms. By applying biological trait analysis (BTA) and generalized linear models to a species dataset collected in the German Wadden Sea (53A degrees 41'14'' N, 7A degrees 14'19'' E) between 1999 and 2012, we show that the size structure of the macrobenthic community changes predictably along environmental gradients. Specifically, body size increases with increasing current-induced shear stress and sediment organic matter content. In addition, the presence of oyster-mussel reefs in one of the sampling stations enhanced the survival of species belonging to the smallest size categories in habitats with high hydrodynamic energy. This was probably due to the local sheltering effects, which together with biodeposition also increased organic matter in the sediment, likely favoring large deposit feeders as well. Our results suggest that body size can be a useful trait for estimating effects of anthropogenic stressors, such as organic enrichment or alteration of hydrodynamic regime and could therefore be effectively included in current monitoring programs of intertidal macrobenthic communities.
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| 3. |
- Engel, Friederike G., et al.
(författare)
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Mussel beds are biological power stations on intertidal flats
- 2017
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Ingår i: Estuarine, Coastal and Shelf Science. - : Elsevier BV. - 0272-7714 .- 1096-0015. ; 191, s. 21-27
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Tidskriftsartikel (refereegranskat)abstract
- Intertidal flats are highly productive areas that support large numbers of invertebrates, fish, and birds. Benthic diatoms are essential for the function of tidal flats. They fuel the benthic food web by forming a thin photosynthesizing compartment in the top-layer of the sediment that stretches over the vast sediment flats during low tide. However, the abundance and function of the diatom film is not homogenously distributed. Recently, we have realized the importance of bivalve reefs for structuring intertidal ecosystems; by creating structures on the intertidal flats they provide habitat, reduce hydrodynamic stress and modify the surrounding sediment conditions, which promote the abundance of associated organisms. Accordingly, field studies show that high chlorophyll a concentration in the sediment co-vary with the presence of mussel beds. Here we present conclusive evidence by a manipulative experiment that mussels increase the local biomass of benthic microalgae; and relate this to increasing biomass of microalgae as well as productivity of the biofilm across a nearby mussel bed. Our results show that the ecosystem engineering properties of mussel beds transform them into hot spots for primary production on tidal flats, highlighting the importance of biological control of sedimentary systems.
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| 4. |
- Hansen, Joakim P., et al.
(författare)
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Recreational boating degrades vegetation important for fish recruitment
- 2019
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Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 48:6, s. 539-551
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Tidskriftsartikel (refereegranskat)abstract
- Recreational boating increases globally and associated moorings are often placed in vegetated habitats important for fish recruitment. Meanwhile, assessments of the effects of boating on vegetation, and potential effects on associated fish assemblages are rare. Here, we analysed (i) the effect of small-boat marinas on vegetation structure, and (ii) juvenile fish abundance in relation to vegetation cover in shallow wave-sheltered coastal inlets. We found marinas to have lower vegetation cover and height, and a different species composition, compared to control inlets. This effect became stronger with increasing berth density. Moreover, there was a clear positive relationship between vegetation cover and fish abundance. We conclude that recreational boating and related moorings are associated with reduced cover of aquatic vegetation constituting important habitats for juvenile fish. We therefore recommend that coastal constructions and associated boating should be allocated to more disturbance tolerant environments (e.g. naturally wave-exposed shores), thereby minimizing negative environmental impacts.
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| 5. |
- Macura, Biljana, et al.
(författare)
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Impact of structural habitat modifications in coastal temperate systems on fish recruitment : a systematic review
- 2019
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Ingår i: Environmental Evidence. - : BioMed Central. - 2047-2382. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: Shallow nearshore marine ecosystems are changing at an increasing rate due to a range of human activities such as urbanisation and commercial development. As a result, an increasing number of structural modifications occur in coastal nursery and spawning habitats of fish. Concomitant to this increase, there have been declines in many coastal fish populations and changes in the composition of fish communities. As requested by Swedish stakeholders, this review aimed to synthesise scientific evidence of the impact on fish recruitment of structural modifications in temperate coastal areas.Methods: We searched for peer-reviewed and grey literature on such impacts in English, Dutch, Danish, Finnish, German, Swedish and Spanish. Searches were performed in bibliographic databases, specialist websites, bibliographies of review articles. We also contacted stakeholder to find relevant literature. Eligible studies included small- and large-scale field studies in marine systems and large lakes (> 10,000 km(2)) in temperate regions of the Northern and Southern Hemispheres. Included replicated comparisons of fish recruitment between altered and unaltered control areas, comparisons before and after an alteration, or both. Relevant outcomes (response variables) included measures of recruitment defined as abundance of juvenile fish in coastal habitats. All fish species were considered. Articles were screened for eligibility by title, abstract and full text. Eligible studies were critically appraised based on their external and internal validity. From each eligible study of sufficient validity, we extracted information on study design, measured outcomes, exposure, type of comparator, effect modifiers and study findings. Study findings were synthesised narratively.Results: We searched for eligible studies in 15 databases, 24 specialist websites, Google Scholar, and bibliographies of 11 review articles. The review finally included 37 studies that were eligible and of sufficient validity to be considered for final synthesis. Most studies (23 of 37) were from the Northern Hemisphere. Studies varied in design, spatial resolution, target fish species, and type of structural habitat change. This high level of variation did not allow for a quantitative synthesis and prevented us from drawing general conclusions on the impact of structures or structural modifications on fish recruitment. In this review we provide a narrative synthesis of the evidence base and classify eligible studies into six categories (based on type of exposure and comparator). The categories are as follows: the impacts on fish recruitment of: (1) artificial structures in coastal areas, (2) structures designed as fish attractors, (3) large scale urban sprawl, (4) 'novel' habitats, (5) habitat loss, and (6) restoration.Conclusions: This review revealed a very limited evidence base for how structural modifications and marine urban sprawl can affect fish recruitment. Thus, there is a substantial mismatch between stakeholder needs and research evidence. Further, the impact and ecological performance of artificial structures depend both on context and species. Clearly, there is a need for more research on the subject, especially on long-term consequences at larger spatial scales.
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| 6. |
- Macura, Biljana, et al.
(författare)
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What is the impact on fish recruitment of anthropogenic physical and structural habitat change in shallow nearshore areas in temperate systems? : A systematic review protocol
- 2016
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Ingår i: Environmental Evidence. - : Springer Science and Business Media LLC. - 2047-2382. ; 5:1
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Forskningsöversikt (refereegranskat)abstract
- Background:Shallow nearshore marine ecosystems are changing at an increasing rate due to a range of human activities such as urbanisation and commercial development. The growing numbers of constructions and other physical and structural alterations of the shoreline often take place in nursery and spawning habitats of many fish and other aquatic species. Several coastal fish populations have seen marked declines in abundance and diversity during the past two decades. A systematic review on the topic would clarify if anthropogenic physical and structural changes of near-shore areas have effects on fish recruitment and which these effects are.Methods:The review will examine how various physical and structural anthropogenic changes of nearshore fish habitats affect fish recruitment. Relevant studies include small- and large-scale field studies in marine and brackish systems or large lakes in temperate regions of the Northern and Southern hemispheres. Relevant studies may be based on comparisons between undisturbed and disturbed areas, before and after disturbance, or both. Relevant outcomes include measures of recruitment defined as abundance of juveniles of nearshore fish communities. Searches will be made for peer-reviewed and grey literature in English, Dutch, Danish, Finnish, German, Swedish and Spanish. All fish species and species groups will be considered in this review. Included relevant studies will be subject to a critical appraisal that will assess study validity. From relevant included studies, we will extract information on study characteristics, measured outcomes, exposure, comparators, effect modifiers and critical appraisal. Data synthesis will contain narrative and summary findings of each included study of sufficient quality. Meta-analysis may be possible in cases where studies report similar types of outcomes.
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| 7. |
- Östman, Örjan, et al.
(författare)
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Top-down control as important as nutrient enrichment for eutrophication effects in North Atlantic coastal ecosystems
- 2016
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Ingår i: Journal of Applied Ecology. - : Wiley. - 0021-8901 .- 1365-2664. ; 53:4, s. 1138-1147
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Forskningsöversikt (refereegranskat)abstract
- Seagrass and seaweed habitats constitute hotspots for diversity and ecosystem services in coastal ecosystems. These habitats are subject to anthropogenic pressures, of which eutrophication is one major stressor. Eutrophication favours fast-growing ephemeral algae over perennial macroalgae and seagrasses, causing habitat degradation. However, changes in top-down control, caused by, for example, overfishing, may also have negative impacts on such habitats by decreasing grazer control of ephemeral algae. Meanwhile, systematic analyses estimating top-down effects of predator manipulations across a wide range of studies are missing, limiting the potential use of top-down control measures in coastal management. Here, we review the literature on experiments that test top-down and bottom-up controls in seagrass Zostera marina and seaweed Fucus spp. food webs in the North Atlantic. Using meta-analysis and meta-regression, we compare effect sizes of consumer and nutrient manipulations on primary producers, grazers and mesopredators. Presence of mesopredators on average doubled the biomass of ephemeral algae through trophic cascades, mainly mediated via negative effects on amphipods and isopods. Of the grazers, gastropods had twice as strong a negative effect on ephemeral algae as amphipods/isopods, but responded weakly to both predators and fertilization. In accordance with theory, top-down effects became stronger with eutrophication. Across studies, top-down effects on ephemeral algae at all trophic levels are on par with eutrophication effects. However, the few studies manipulating piscivorous fish make estimates of their top-down effects uncertain.Synthesis and applications. Consistently strong top-down effects in coastal ecosystems call for an integrated ecosystem perspective. Management should consider measures to improve stocks of predatory fish and reduce mesopredators for restoration and conservation of essential seagrass and seaweed habitats, thereby increasing the long-term viability of ecosystem services from coastal habitats.
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