| 1. |
- Asmala, Eero, et al.
(författare)
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Role of Eelgrass in the Coastal Filter of Contrasting Baltic Sea Environments
- 2019
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Ingår i: Estuaries and Coasts. - : Springer Science and Business Media LLC. - 1559-2723 .- 1559-2731. ; 42:7, s. 1882-1895
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Tidskriftsartikel (refereegranskat)abstract
- Coastal ecosystems act as filters of nutrients from land to the open sea. We investigated the role of eelgrass (Zostera marina) metabolism in the coastal filter transforming nitrogen, phosphorus, and organic carbon. Field campaigns following identical methodologies were carried out at two contrasting coastal locations: the mesohaline and nutrient-rich Roskilde Fjord, Denmark, and the mesotrophic brackish Tvarminne archipelago, Finland. Over the 24-h in situ benthic incubations, we measured oxygen concentrations continuously and assessed changes in DOM characteristics and net fluxes of carbon, nitrogen, and phosphorus. Ecosystem metabolism modeled on the basis of the O-2 data showed that the systems were either net heterotrophic (Roskilde Fjord; - 1.6 and - 2.4 g O-2 m(-2) day(-1) in eelgrass meadow and bare sand, respectively) or had balanced primary production and respiration (Tvarminne; 0.0 and 0.2 g O-2 m(-2) day(-1)). Overall, initial nutrient stoichiometry was a key factor determining benthic-pelagic fluxes of nutrients, which exacerbated the deviations from Redfield ratios of N and P, indicating an efficient use of the limiting nutrient. A net diel uptake of dissolved inorganic N was observed at both locations (- 2.3 mu mol l(-1) day(-1) in Roskilde Fjord and - 0.1 mu mol l(-1) day(-1) in Tvarminne). Despite minor changes in dissolved organic carbon concentrations during the incubations, a marked increase of fluorescent DOM was observed at both locations, suggesting rapid heterotrophic processing of the DOM pool. Our results underline that the biogeochemical role of eelgrass in the coastal filter is not inherent, but strongly dependent on the environmental conditions.
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| 2. |
- Correa, R. E., et al.
(författare)
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Groundwater Carbon Exports Exceed Sediment Carbon Burial in a Salt Marsh
- 2022
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Ingår i: Estuaries and Coasts. - : Springer Science and Business Media LLC. - 1559-2723 .- 1559-2731. ; 45, s. 1545-61
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Tidskriftsartikel (refereegranskat)abstract
- Salt marshes can sequester large amounts of carbon in sediments, but the relation between carbon storage and exportation remains poorly understood. Groundwater exchange can flush sediment carbon to surface waters and potentially reduce storage. In this study, we estimated groundwater fluxes and associated carbon fluxes using a radon (Rn-222) mass balance and sediment carbon burial rates using lead (Pb-210) in a pristine salt marsh (North Inlet, SC, USA). We used delta C-13 to trace carbon origins. We found that groundwater releases large amounts of carbon to the open ocean. These groundwater fluxes have the potential to export 7.2 +/- 5.5 g m(-2) of dissolved inorganic carbon (DIC), 0.2 +/- 0.2 g m(-2) of dissolved organic carbon (DOC) and 0.7 +/- 0.5 g m(-2) of carbon dioxide (CO2) per day. The fluxes exceed the average surface water CO2 emissions (0.6 +/- 0.2 g m(-2) day(-1)) and the average sediment carbon burial rates (0.17 +/- 0.09 g m(-2) day(-1)). The delta C-13 results suggest that groundwater carbon originated from salt marsh soils, while the sediment carbon source is derived from salt marsh vegetation. We propose that the impact of salt marshes in carbon cycling depends not only on their capacity to bury carbon in sediments, but also on their high potential to export carbon to the ocean via groundwater pathways.
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| 3. |
- Dijkstra, Nikki, et al.
(författare)
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Holocene Refreshening and Reoxygenation of a Bothnian Sea Estuary Led to Enhanced Phosphorus Burial
- 2018
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Ingår i: Estuaries and Coasts. - : Springer Science and Business Media LLC. - 1559-2723 .- 1559-2731. ; 41:1, s. 139-157
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Tidskriftsartikel (refereegranskat)abstract
- Salinity variations in restricted basins like the Baltic Sea can alter their vulnerability to hypoxia (i.e., bottom water oxygen concentrations <2 mg/l) and can affect the burial of phosphorus (P), a key nutrient for marine organisms. We combine porewater and solid-phase geochemistry, micro-analysis of sieved sediments (including XRD and synchrotron-based XAS), and foraminiferal δ18O and δ13C analyses to reconstruct the bottom water salinity, redox conditions, and P burial in the Ångermanälven estuary, Bothnian Sea. Our sediment records were retrieved during the Integrated Ocean Drilling Program (IODP) Baltic Sea Paleoenvironment Expedition 347 in 2013. We demonstrate that bottom waters in the Ångermanälven estuary became anoxic upon the intrusion of seawater in the early Holocene, like in the central Bothnian Sea. The subsequent refreshening and reoxygenation, which was caused by gradual isostatic uplift, promoted P burial in the sediment in the form of Mn-rich vivianite. Vivianite authigenesis in the surface sediments of the more isolated part of the estuary ultimately ceased, likely due to continued refreshening and an associated decline in productivity and P supply to the sediment. The observed shifts in environmental conditions also created conditions for post-depositional formation of authigenic vivianite, and possibly apatite formation, at ∼8 m composite depth. These salinity-related changes in redox conditions and P burial are highly relevant in light of current climate change. The results specifically highlight that increased freshwater input linked to global warming may enhance coastal P retention, thereby contributing to oligotrophication in both coastal and adjacent open waters.
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| 4. |
- Duarte, Carlos M., et al.
(författare)
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Return to Neverland: Shifting Baselines Affect Eutrophication Restoration Targets
- 2009
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Ingår i: Estuaries and Coasts. - : Springer Science and Business Media LLC. - 1559-2731 .- 1559-2723. ; 32:1, s. 29-36
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Tidskriftsartikel (refereegranskat)abstract
- The implicit assumption of many scientific and regulatory frameworks that ecosystems impacted by human pressures may be reverted to their original condition by suppressing the pressure was tested using coastal eutrophication. The response to nutrient abatement of four thoroughly studied coastal ecosystems that received increased nutrient inputs between the 1970s and the 1980s showed that the trajectories of these ecosystems were not directly reversible. All four ecosystems displayed convoluted trajectories that failed to return to the reference status upon nutrient reduction. This failure is proposed to result from the broad changes in environmental conditions, all affecting ecosystem dynamics, that occurred over the 30 years spanning from the onset of eutrophication to the reduction of nutrient levels. Understanding ecosystem response to multiple shifting baselines is essential to set reliable targets for restoration efforts.
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| 5. |
- Engelsen, Anna, 1964, et al.
(författare)
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Links Between Bottom-Water Anoxia, the Polychaete Nereis diversicolor, and the Growth of Green-Algal Mats
- 2010
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Ingår i: Estuaries and Coasts. - : Springer Science and Business Media LLC. - 1559-2723 .- 1559-2731. ; 33:6, s. 1365-1376
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Tidskriftsartikel (refereegranskat)abstract
- Sediment-water incubations were used to study effects of episodic anoxia on filamentous Ulva sp. Treatments included undisturbed sediment with (AnoxSed) and without (NatSed) exposure to 5 days of anoxia, and cores with only the top 0.5 cm of sediment (SurfSed; no macrofauna, restricted pore-water nutrient pool). All three treatments contained Ulva propagules. An Ulva mat developed in the SurfSed, and after the anoxic period in the AnoxSed cores. No growth was observed in the NatSed treatment. In the AnoxSed, Ulva was progressively removed upon reoxygenation through grazing by Nereis. The results suggest that episodic anoxia stimulates the growth of macroalgal mats not only by increasing the availability of nutrients from the sediment, but also by reducing macrofaunal grazing pressure. Infauna (grazing and bioturbation), benthic microalgae (nutrient competition and retention), and pore-water nutrients appear key components in a biogeochemical network with complex feedbacks controlling the growth of green-algal mats in shallow-water systems.
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| 6. |
- Enrich Prast, Alex, et al.
(författare)
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Sediment Denitrification in Two Contrasting Tropical Shallow Lagoons
- 2016
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Ingår i: Estuaries and Coasts. - : SPRINGER. - 1559-2723 .- 1559-2731. ; 39:3, s. 657-663
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Tidskriftsartikel (refereegranskat)abstract
- Sediment denitrification was monthly evaluated in two tropical coastal lagoons with different trophic states using the N-15 isotope pairing technique. Denitrification rates were very low in both environments, always < 5.0 mu mol N-2 m(-2) h(-1) and were not significantly different between them. Oxygen consumption varied from 426 to 4248 mu mol O-2 m(-2) h(-1) and was generally three times higher in the meso-eutrophic than the oligotrophic lagoon. The low denitrification activity was ascribed to both low water NO3- concentrations (< 2.0 mu M) and little nitrate supply from nitrification. There was no correlation of denitrification with nitrate or ammonium fluxes. Sediments in temperate environments with similar oxygen consumption rates usually presented a higher proportion of nitrification-denitrification rates. Sediment oxygen consumption was a good predictor of sediment denitrification in both studied lagoons.
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| 7. |
- Joensuu, Mari, et al.
(författare)
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Temporal Variation in Resuspension Potential and Associated Nutrient Dynamics in Shallow Coastal Environments
- 2020
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Ingår i: Estuaries and Coasts. - : Springer Science and Business Media LLC. - 1559-2723 .- 1559-2731. ; 43, s. 1361-1376
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Tidskriftsartikel (refereegranskat)abstract
- Sediment resuspension may play a major role in sediment-water exchange of nutrients, matter and energy in coastal areas where waves and currents dominate sediment transport. Biogeochemical sediment properties regulate sediment erodibility, but there is only limited knowledge of how temporal variability in environmental variables is reflected in the resuspension potential, especially for subtidal habitats. Further, the significance of resuspension on nutrient fluxes in coastal environments has remained unclear as contradicting results have been reported. Here we quantified the temporal variation in resuspension potential metrics (erosion threshold (tau(c); N m(-2)) and erosion constant (m(e); g N-1 s(-1))) and associated nutrient fluxes from three sites in the Hanko archipelago (Finland) using a core-based erosion device (EROMES). The sites were sampled bi-monthly from April to December. We also quantified the temporal variation in biogeochemical sediment properties at each site. The tau(c) exhibited the clearest temporal pattern in muddy sediment, where the coefficient of variation (= 67) was two to three times higher than the mixed (= 29) and sandy (= 16) sediments. Dry bulk density was the best predictor for sediment erodibility at all sites explaining 26-46% of the temporal variation in tau(c) despite its limited variability at sandier sites. In addition, temporal variations in the macrofaunal community were important predictors of muddy sediment erodibility and therefore community dynamics need to be considered in sediment transport studies. All sites were potential nutrient sources, yet the overall role of sediment resuspension on nutrient release from the sediments was small.
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| 8. |
- Kahma, T. I., et al.
(författare)
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Macrofauna Community Dynamics and Food Webs in the Canopy-forming Macroalgae and the Associated Detrital Subsidies
- 2023
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Ingår i: Estuaries and Coasts. - 1559-2723 .- 1559-2731. ; 46:5, s. 1345-1362
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Tidskriftsartikel (refereegranskat)abstract
- Dietary variability and the degradation and incorporation of macroalgae in key macroinvertebrate consumers were examined (1) in a monitoring field study including a natural attached canopy habitat and an adjacent habitat receiving natural accumulations of detritus, and (2) in a manipulative in situ experiment of macroalgal detritus at two different depths (3 and 6 m) in the archipelago of SW Finland. The monitoring field study, examining species-specific dietary responses across three sampling dates in natural macroalgal stands, showed that a pulse of drifting filamentous macroalgae shaped the dietary compositions of the abundant benthic macroinvertebrate consumers and that accumulations of drifting filamentous macroalgae were rapidly incorporated into the food web through epigrazers. The in situ field experiment simulating a natural accumulation event and the degradation process of Fucus vesiculosus during 60 days showed that algal decomposition progressed relatively slowly at both depths. Detectable increasing incorporation of Fucus-derived matter to epigrazers and detritivorous bivalves occurred after 2−3 weeks, while simultaneously the incorporation of filamentous algae decreased over time. Hence, the ecological role of decomposing F. vesiculosus might be more important in areas where the algal matter can accumulate for several months. The effect of depth influenced the food incorporation of typical epigrazers. The increasing depth from 3 to 6 m lowered the median proportion of Fucus-derived matter incorporated into the macrofauna community approximately by 10% points compared to the shallower depth of 3 m.
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| 9. |
- Moksnes, Per-Olav, 1965, et al.
(författare)
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Local Regime Shifts Prevent Natural Recovery and Restoration of Lost Eelgrass Beds Along the Swedish West Coast
- 2018
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Ingår i: Estuaries and Coasts. - : Springer Science and Business Media LLC. - 1559-2723 .- 1559-2731. ; 41:6, s. 1712-1731
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Tidskriftsartikel (refereegranskat)abstract
- Along the Swedish northwest coast, over 60% of the eelgrass meadows have been lost since the 1980s. Despite improved water quality, no recovery has occurred, and restoration is presently considered to mitigate historical losses. However, the factors preventing natural recovery of eelgrass are not known, and it is not clear if conditions would allow restoration. Here, we present the results from 5 years of field studies with the aim of identifying the key processes affecting eelgrass growth and survival at historical eelgrass areas. Continuous light measurements and comparison with historic eelgrass distribution indicate that maximum depth distribution has decreased locally with 1.5–2.3 m in areas that have lost large eelgrass beds in the last 10–30 years. Field studies suggest that wind-driven local resuspension of sediments that are no longer stabilized by eelgrass beds is the main cause behind the deteriorated light conditions. Field experiments show that a combination of low light condition and disturbance from drifting algal mats prevents eelgrass recovery in these areas, whereas the sulfide intrusion from the sediment and dislodgement of shoots by waves had little effect on growth and survival. These results suggest that local regime shifts acting on a scale of 40–200 ha have occurred after the loss of eelgrass beds, where increased sediment resuspension and proliferation of drifting algal mats act as feedback mechanisms that prevent both natural recovery and restoration of eelgrass. The feedbacks appear to be interacting and causing an accelerating loss of eelgrass that is presently spreading to neighboring areas.
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| 10. |
- Quintana, Cintia O., et al.
(författare)
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Functional Performance of Three Invasive Marenzelleria Species Under Contrasting Ecological Conditions Within the Baltic Sea
- 2018
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Ingår i: Estuaries and Coasts. - : Springer Science and Business Media LLC. - 1559-2723 .- 1559-2731. ; 41:6, s. 1766-1781
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Tidskriftsartikel (refereegranskat)abstract
- A 4-week laboratory experiment investigated the behaviour (survival and bioirrigation) and impact of the invasive polychaetes Marenzelleria viridis, M. neglecta and M. arctia on sediment-water solutes exchange, porewater chemistry, and Fe and P interactions in high-salinity sandy sediment (HSS) and low-salinity muddy sediment (LSM) from the Baltic Sea. M. viridis showed deep burrowing with efficient bioirrigation (11 L m−2 day−1) and high survival (71%) in HSS, while M. arctia exhibited shallow burrowing with high bioirrigation (12 L m−2 day−1) and survival (88%) in LSM. M. neglecta behaved poorly in both ecological settings (bioirrigation, 5–6 L m−2 day−1; survival, 21–44%). The deep M. viridis bioirrigation enhanced total microbial CO2 (TCO2) production in HSS by 175% with a net efflux of NH4+ and PO43−, at rates 3- to 27-fold higher than for the other species. Although the shallow and intense bioirrigation of M. arctia in LSM stimulated microbial TCO2 production to some extent (61% enhancement), the nutrient fluxes close to zero indicate that it effectively prevented the P release. Porewater Fe:PO43− ratios revealed that the oxidizing effect of M. arctia bioirrigation increased the PO43− adsorption capacity of LSM twofold relative to defaunated controls while no buffering of PO43− was detected in M. viridis HSS treatment. Therefore, the different behaviour of the three species in various environments and the sharp contrast between M. viridis and M. arctia effects on C, N and P cycling must be considered carefully when the ecological role of Marenzelleria species in the Baltic Sea is evaluated.
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