| 1. |
- Bonaglia, Stefano, et al.
(author)
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Meiofauna improve oxygenation and accelerate sulfide removal in the seasonally hypoxic seabed
- 2020
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In: Marine Environmental Research. - : Elsevier BV. - 0141-1136 .- 1879-0291. ; 159
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Journal article (peer-reviewed)abstract
- Oxygen depleted areas are widespread in the marine realm. Unlike macrofauna, meiofauna are abundant in hypoxic sediments. We studied to what extent meiofauna affect oxygen availability, sulfide removal and microbial communities. Meiofauna were extracted alive and added to intact sediments simulating abundance gradients previously reported in the area. A total of 324 porewater microprofiles were recorded over a 3-week incubation period and microbial community structure and cable bacteria densities were determined at the end of the experiment. At high abundances meiofauna activity deepened oxygen penetration by 85%, 59%, and 62% after 5, 14, and 22 days, respectively, compared to control sediment with scarce meiofauna. After 6 days, meiofauna increased the volume of oxidized, sulfide-free sediment by 68% and reduced sulfide fluxes from 8.8 to 0.4 mmol m(-2) d(-1). After 15 days, the difference with the control attenuated due to the presence of a cable bacteria population, which facilitated sulfides oxidation in all treatments. 16S rRNA gene analysis revealed that meiofauna affected microbial community structure (beta diversity). Thus, meiofauna bioturbation plays an important role in deepening oxygen penetration, counteracting euxinia and in structuring microbial diversity of hypoxic sediments. Co-existence with cable bacteria demonstrates neutralism interaction between these two ecosystem engineers.
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| 2. |
- Bradshaw, Clare, 1972-, et al.
(author)
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Effects of bottom trawling and environmental factors on benthic bacteria, meiofauna and macrofauna communities and benthic ecosystem processes
- 2024
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In: Science of the Total Environment. - 0048-9697 .- 1879-1026. ; 921
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Journal article (peer-reviewed)abstract
- Soft sediment marine benthic ecosystems comprise a diverse community of bacteria, meiofauna and macrofauna, which together support a range of ecosystem processes such as biogeochemical cycling. These ecosystems are also fishing grounds for demersal species that are often caught using bottom trawling. This fishing method can have deleterious effects on benthic communities by causing injury or mortality, and through alteration of sediment properties that in turn influence community structure. Although the impacts of bottom trawling on macrofauna are relatively well studied, less is known about the responses of meiofauna and bacteria to such disturbances, or how bottom trawling impacts benthic ecosystem processes. Quantifying trawling impacts against a background of natural environmental variability is also a challenge. To address these questions, we examined effects of bottom trawling and a range of environmental variables (e. g. water chemistry and physical and biochemical surface sediment properties) on a) bacterial, meiofaunal and macrofaunal community structure and b) benthic ecosystem processes (nutrient fluxes, extracellular enzyme activities and carbon turnover and degradation rates). We also investigated the link between the benthic macrofauna community and the same ecosystem processes. While there was a significant effect of bottom trawling intensity on macrofaunal community structure, the same was not seen for bacterial or meiofaunal community composition, which were more affected by environmental factors, such as surface sediment properties. The labile component of the surface sediment carbon pool was higher at highly trawled sites. Carbon degradation rates, extracellular enzyme activities, oxygen fluxes and some nutrient fluxes were significantly affected by trawling, but ecosystem processes were also strongly linked to the abundance of key bioturbators (Macoma balthica, Halicryptus spinulosus, Scoloplos armiger and Pontoporeia femorata). Although benthic ecosystems were affected by a combination of trawling and natural variability, disentangling these showed that the anthropogenic effects were clearest on the larger component of the community, i.e. macrofauna composition, and on ecosystem processes related to sedimentary carbon.
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| 3. |
- Iburg, Sven, et al.
(author)
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Effects of bottom trawling on the benthic habitat, with special emphasis on bacteria, meio- and macrofaunal diversity and ecosystem functioning
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Other publication (other academic/artistic)abstract
- Commercial bottom trawling can have deleterious effects on benthic communities by causing physical disturbance to sediment structure. Although the impacts of bottom trawling on macrofauna are relatively well studied, less is known about the responses of meiofauna and bacterial communities to such disturbances. Additionally, there is a lack of information on how potential effects of trawling on benthic community structure translate into impacts on ecosystem functions. To address these questions, we conducted a field study in the Baltic Sea (Bornholm area) that sampled 6 sites exposed to different trawling intensities. At each site sediment microbial and meiofauna diversity and community structure was assessed with metabarcoding of the 16S and 18S marker gene, respectively. Macrofauna community structure together with community bioturbation potential and nutrient fluxes were measured to investigate differences in ecosystem functioning in sediments subjected to varying degrees of trawling intensity. While there was a significant effect of bottom trawling intensity on macrofauna community structure, the same was not seen for microbial or meiofauna diversity and community composition Instead, our data showed stronger correlations between microbial and meiofaunal community structure and abiotic factors, in particular sediment pigment content. Similarly, differences in community bioturbation potential and nutrient fluxes were not driven by trawling intensity but were instead linked the abundance of key bioturbators like Scololpos armiger and Limecola balthica at each site. Overall, with the exception of macrofauna community structure, our study did not find significant impacts of bottom trawling on benthic diversity, community composition or function in the commercially fished areas in the Bornholm Basin, Baltic Sea. Our response variables were instead mostly driven by spatial differences in sediment abiotic and biotic parameters between our sampled sites. However, closer examination of a geographically close pair of sites with different trawling intensities showed clear differences in community structure in all three faunal groups. Bottom trawling impacts may therefore be masked by strong spatial variation in abiotic factors, something that should be considered in future studies.
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| 4. |
- Iburg, Sven, et al.
(author)
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Effects of Recreational Boating on Microbial and Meiofauna Diversity in Coastal Shallow Ecosystems of the Baltic Sea
- 2021
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In: mSphere. - 2379-5042. ; 6:5
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Journal article (peer-reviewed)abstract
- Recreational boating can impact benthic ecosystems in coastal waters. Reduced height and cover of aquatic vegetation in shallow Baltic Sea inlets with high boat traffic have raised concerns about cascading effects on benthic communities in these ecosystems. Here, we characterized the diversity and composition of sediment-associated microbial and meiofaunal communities across five bays subjected to low and high degrees of boating activity and examined the community-environment relationships and association with bay morphometry. We found that recreational boating activity altered meiofauna alpha diversity and the composition of both micro- and meiobenthic communities, and there were strong correlations between community structure and morphometric variables like topographic openness, wave exposure, water surface area, and total phosphorous concentrations. Inlets with high boat traffic showed an increase of bacterial taxa like Hydrogenophilaceae and Burkholderiaceae. Several meiofauna taxa previously reported to respond positively to high levels of suspended organic matter were found in higher relative abundances in the bays with high boat traffic. Overall, our results show that morphometric characteristics of inlets are the strongest drivers of benthic diversity in shallow coastal environments. However, while the effects were small, we found significant effects of recreational boating on benthic community structure that should be considered when evaluating the new mooring projects.IMPORTANCE With the increase of recreational boating activity and development of boating infrastructure in shallow, wave-protected areas, there is growing concern for their impact on coastal ecosystems. In order to properly assess the effects and consider the potential for recovery, it is important to investigate microbial and meiofaunal communities that underpin the functioning of these ecosystems. Here, we present the first study that uses DNA metabarcoding to assess how benthic biodiversity in shallow coastal areas is impacted by recreational boating. Our study shows a relatively small, but significant, effect of recreational boating both on meiofauna alpha diversity and meiofauna and bacterial community composition. However, both meiofauna and bacterial community composition in shallow benthic habitats is mediated to a higher degree by abiotic variables, such as topographic openness, area or size of the inlets, and wave exposure. Despite the fact that the effects were small, such impacts on benthic biodiversity should be considered in the management of coastal shallow habitats.
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| 5. |
- Iburg, Sven, 1986-
(author)
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Microbenthos under Pressure : Impacts of human activities on bacteria and meiofauna communities in Baltic soft sediments
- 2022
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Doctoral thesis (other academic/artistic)abstract
- The marine benthic zone is one of the largest habitats on the planet, harbouring a large diversity of life that underpin many important ecological processes. However, these habitats have been under growing stress from human activities, profoundly altering their living communities. How microbial communities respond to various anthropogenic disturbances has been a central topic in ecology, but the response of meiofauna (benthic microeukaryotes, 40 µm ≥ 1 mm in size) and their use as potential bioindicators in a whole-community approach, has received less attention. The Baltic Sea has been of particular interest in studying how ecological processes are affected due to its history and continuous exposure to various anthropogenic stresses. In this thesis, I explored the effects of chemical contamination (Study I), recreational boating activity (Study II), bottom trawling fishing (Study III), and hypoxia (Study IV) on the Baltic microbenthos in terms of structure and diversity using DNA-inferred community analysis in the context of controlled experiments (Studies I and IV) and field studies (Studies II and III). Study I showed a clear increase in contaminated sediments in PAH degradation, relative abundance of Pseudomonas amongst bacteria, and nematodes amongst meiofauna. Study IV showed that high meiofauna abundance, and its bioturbation, altered sediment oxygen penetration and sulphide oxidation in hypoxic conditions with clear effects on bacterial community structure. Studies II and III showed that select bacteria and meiofauna taxa were favoured in areas with high levels of disturbance. In Study II, the ostracod family Cypridoidea was found in higher abundance in bays with high recreational boating activity (marinas) whilst Cytheruridae was significantly lower. Amongst bacteria, Burkholderiaceae showed to be favoured in active marinas and served as an indicator of chemical contamination. In Study III, highly trawled areas appeared to favour Rhabdocoels flatworms and were accompanied by a decrease in Rhizobiales amongst bacteria, suggesting improved feeding opportunities for motile flatworms, and a negative pressure on substrate dependent bacteria. However, the exposure to the open sea was a major factor in structuring both meiofauna and bacterial communities in shallow bays (Study II) and the impact of trawling (Study III) was more pronounced between areas that were geographically closer. This highlights the importance of abiotic and location specific co-factors that drive microbial and meiofauna assemblages and stress the impact of survey design and sampling locations. Additionally, a common trend throughout my work emphasised the potential of select microbial taxa as bioindicators. For example, the bacteria families Pseudomonadaceae and Burkholderiaceae, and the nematode genera Sabatieria and Leptolaimus could be used as bacterial and meiofauna bioindicators of chemical contamination. In brief, chemical stress had a significant effect on bacterial community structure, whereas physical disturbances had a more pronounced effect on meiofauna, both in terms of structural changes as well as alpha diversity. As such, combining the study of meiofauna and microbial assemblages could be a useful approach in assessing the effects of a wide range of disturbances in benthic habitats.
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| 6. |
- Iburg, Sven, et al.
(author)
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Organic Contaminant Mixture Significantly Changes Microbenthic Community Structure and Increases the Expression of PAH Degradation Genes
- 2020
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In: Frontiers in Environmental Science. - : Frontiers Media SA. - 2296-665X. ; 8
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Journal article (peer-reviewed)abstract
- © Copyright © 2020 Iburg, Nybom, Bonaglia, Karlson, Sobek and Nascimento. Studying the effects of chemical contaminants on the structure and function of microbial and meiofauna communities have traditionally focused on specific effects of single contaminants on single species. This has left the complex interactions between mixtures of contaminants and its non-specific toxicity effects on the functions and structure of sediment microbial communities mostly overlooked. In order to improve our insights on such questions, we performed an experiment where Baltic Sea sediments were spiked with an ecologically relevant mixture of seven organic contaminants below specific toxicity levels and used 16S and 18S rRNA metabarcoding from RNA extracts to monitor changes in active microbial and meiofauna diversity and community structure in the spiked treatment compared to controls. In addition, we investigated the effects of exposure to this contaminant mixture on potential nitrification rates and on the expression of key-genes in the microbial nitrification and PAH degradation pathways with qPCR. There were significant differences in both eukaryotic and microbial community structures in sediments spiked with a mixture of organic contaminants. Nematoda showed a significant increase in overall relative abundance to the added contaminants (5.5 ± 1.1% higher in spiked), particularly taxa of the genus Leptolaimus (increased from 10.2 ± 5.4% in the controls to 32.5 ± 10.2% in the spiked treatment). Conversely, a significant decrease in relative abundance from 18.2 ± 5.6% in control to 7 ± 3.4% in of the genus Paraplectana was also detected. Additionally, while the abundance of active PAH degraders was significantly higher in spiked sediments than in the controls, no significant effect of our organic mixture was found on nitrification rates or the expression of AmoA (bacterial ammonia oxidizer gene). Our data indicate that mixtures of organic contaminants can have significant effects on microbenthic community structure even when its individual components are present at concentrations below its specific toxicity. In addition, we suggest that eRNA-based metabarcoding can offer important insights in microbenthic community structure and activities, and further empathizes the potential of meiofauna as bio-indicators of chemical contamination in benthic ecosystems.
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