| 1. |
- Adams, M. P., et al.
(författare)
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Water residence time controls the feedback between seagrass, sediment and light: Implications for restoration
- 2018
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Ingår i: Advances in Water Resources. - : Elsevier BV. - 0309-1708. ; 117, s. 14-26
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Tidskriftsartikel (refereegranskat)abstract
- Feedbacks between seagrass and the local environmental conditions may hinder attempts to restore seagrass by inducing alternative stable states. A one-dimensional physical-biological model was used to identify the conditions under which a feedback between seagrass, sediment and light can yield alternative stable states of seagrass presence and absence (bistability). Based on our model results, a prediction of whether a given seagrass meadow is large enough to promote seagrass growth can now be made. If the water residence time within the spatial area of the meadow is similar to or greater than the sediment settling time, which is calculated from the ratio of water depth to sediment vertical settling velocity, the meadow is large enough for the feedback to potentially reduce the local suspended sediment concentration. This has important implications for seagrass restoration: for a proposed restoration plot, if the water residence time is similar to or greater than the sediment settling time, the scale of restoration is large enough for the feedback between seagrass, sediment and light to locally improve water clarity. More generally, this calculation can be used to identify areas where this feedback is likely to generate bistability, and to estimate the minimum suitable meadow size in such locations. © 2018 Elsevier Ltd
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| 2. |
- Barcelona, Aina, et al.
(författare)
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The role epiphytes play in particle capture of seagrass canopies
- 2023
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Ingår i: Marine Environmental Research. - 0141-1136 .- 1879-0291. ; 192
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Tidskriftsartikel (refereegranskat)abstract
- Seagrass epiphytic communities act as ecological indicators of the quality status of vegetated coastal environments. This study aims to determine the effect leaf epiphytes has on the sediment capture and distribution from outside sources. Thirteen laboratory experiments were conducted under a wave frequency of 0.5 Hz. Three epiphyte models were attached to a Zostera marina canopy of 100 plants/m2 density. The sediment deposited to the seabed, captured by the epiphytic leaf surface, and remaining in suspension within the canopy were quantified. This study demonstrated that the amount of epiphytes impacts on the sediment stocks. Zostera marina canopies with high epiphytic areas and long effective leaf heights may increase the sediment captured on the epiphyte surfaces. Also, reducing suspended sediment and increasing the deposition to the seabed, therefore enhancing the clarity of the water column. For largest epiphytic areas, a 34.5% increase of captured sediment mass is observed. The sediment trapped on the leaves can be 10 times greater for canopies with the highest epiphytic areas than those without epiphytes. Therefore, both the effective leaf length and the level of epiphytic colonization are found to determine the seagrass canopy ability at distributing sediment.
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| 3. |
- Castejón-Silvo, I., et al.
(författare)
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Increased energy expenditure is an indirect effect of habitat structural complexity loss
- 2021
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Ingår i: Functional Ecology. - : Wiley. - 0269-8463 .- 1365-2435. ; 35:10, s. 2316-2328
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Tidskriftsartikel (refereegranskat)abstract
- The deterioration of coastal habitats cascades to the decline of associated fauna by reducing trophic resource availability, shelter from predators and nursery grounds. The decline of biogenic habitat structure, such as in kelp forests, coral reefs, mangroves or seagrass beds, often causes a local increase in water flow velocity and wave exposure. The impact of this change in hydrodynamics on the energy expenditure of animals is largely unknown. Here we demonstrate that loss of seagrass beds increases water current velocity, which impacts associated pipefishes through increased energy expenditure. We correlated ventilation frequency with metabolic rate in four pipefish species, to be able to estimate metabolic rates in free-swimming fish. Using a hydrodynamic flume, we then experimentally tested the effect of current velocity and substrate (seagrass or sand) on ventilation frequency and behaviour. Ventilation frequency was consistently higher when they swam on sand substratum compared to seagrass substratum for all species, and this was especially noticeable for the species with prehensile tails (i.e. Nerophis ophidion). Seagrass canopies reduced flow velocities by 7%–44%, which increased the overall current exposure that pipefish tolerated. N. ophidion, Syngnathus rostellatus and Syngnathus typhle showed two behavioural responses to currents: holding on to the seagrass canopy, and moving to areas where the current was lower (i.e. bottom) in trials without seagrass. Most of the individuals of all species were unable to maintain position in velocities of 15–18cm/s on sand substratum. In this work, we demonstrate the reliance on seagrass hydrodynamic shelter of four species of pipefish. Among them, N. ophidion showed the highest seagrass shelter dependence and vulnerability, while S. rostellatus and S. typhle are potentially more resilient to vegetation changes. Increased energy expenditure is thus another impact on fishes as seagrass beds and other structural habitats continue to decline in coastal areas. A free Plain Language Summary can be found within the Supporting Information of this article. © 2021 The Authors. Functional Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society
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| 4. |
- Cossa, Damboia, et al.
(författare)
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Drones and machine-learning for monitoring dugong feeding grounds and gillnet fishing
- 2023
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Ingår i: Marine Ecology Progress Series. - 0171-8630 .- 1616-1599. ; 716, s. 123-136
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Tidskriftsartikel (refereegranskat)abstract
- Fishing provides an important food source for humans, but it also poses a threat to many marine ecosystems and species. Declines in wildlife populations due to fishing activities can remain undetected without effective monitoring methods that guide appropriate management actions. In this study, we combined the use of unmanned aerial vehicle-based imaging (drones) with machine-learning to develop a monitoring method for identifying hotspots of dugong foraging based on their feeding trails and associated seagrass beds. We surveyed dugong hotspots to evaluate the influence of gillnet fishing activities on dugong feeding grounds (Saco East and Saco West) at Inhaca Island, southern Mozambique. The results showed that drones and machine-learning can accurately identify and monitor dugong feeding trails and seagrass beds, with an F1 accuracy of 80 and 93.3%, respectively. Feeding trails were observed in all surveyed months, with the highest density occurring in August (6040 ± 4678 trails km−2). There was a clear overlap of dugong foraging areas and gillnet fishing grounds, with a statistically significant positive correlation between fishing areas and the frequency of dugong feeding trails. Dugongs were found to feed mostly in Saco East, where the number of gillnet stakes was 3.7 times lower and the area covered by gillnets was 2.6 times lower than in Saco West. This study highlights the clear potential of drones and machine-learning to study and monitor animal behaviour in the wild, particularly in hotspots and remote areas. We encourage the establishment of effective management strategies to monitor and control the use of gillnets, thereby avoiding the accidental bycatch of dugongs.
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| 5. |
- Cossa, Damboia, et al.
(författare)
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Hidden cost of pH variability in seagrass beds on marine calcifiers under ocean acidification
- 2024
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Ingår i: Science of the Total Environment. - 0048-9697 .- 1879-1026. ; 915
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Tidskriftsartikel (refereegranskat)abstract
- Coastal ecosystems experience large environmental variability leading to local adaptation. The key role of variability and adaptation in modulating the biological sensitivity to ocean acidification is increasingly acknowledged. Monitoring and understanding the ecological niche at the right spatio-temporal scale is key to understand the sensitivity of any organism and ecosystems. However, the role of the variability in relevant carbonate chemistry parameters as a driver is often overlooked. For example, the balance between photosynthesis and respiration over the day/night cycle is leading to high pH/pCO2 variability in seagrass beds. We hypothesized that (i) the calcifying larvae of the sea urchin Echinus esculentus exposed to seagrass-driven variability would have some physiological mechanisms to respond to such variability; and (ii) these mechanisms would reach their limit under ocean acidification. We compared the presence and absence of the seagrass Zostera marina in flow through mesocosms fed with seawater with 4 pHs. The carbonate chemistry was monitored and biological response of a sea urchin larvae was documented over 3 weeks. Growth and net calcification rates were measured twice a day to encompass diurnal variability. Our results show that larvae growth rate significantly decreased with decreasing average pHT in both absence and presence of seagrass. Moreover, sea urchin larvae showed a slower growth rate in presence of seagrass, only visible in the lowest pH conditions. In addition, larvae raised in presence of seagrass, maximized calcification during the day, and lower their calcification during the night. In contrast, no significant difference was observed between day and night for the net calcification rate in larvae raised in absence of seagrass. Our results demonstrate the limit of local adaptation to the present range of variability under ocean acidification conditions. It also demonstrates that photosynthetic ecosystems such as seagrass may not play a role of refuge against future ocean acidification.
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| 6. |
- Dahl, Martin, et al.
(författare)
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High Seasonal Variability in Sediment Carbon Stocks of Cold-Temperate Seagrass Meadows
- 2020
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Ingår i: Journal of Geophysical Research: Biogeosciences. - 2169-8953 .- 2169-8961. ; 125:1
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Tidskriftsartikel (refereegranskat)abstract
- ©2020. American Geophysical Union. All Rights Reserved. Seagrass meadows have a high ability to capture and store atmospheric CO2 in the plant biomass and underlying sediment and thereby function as efficient carbon sinks. The seagrass Zostera marina is a common species in the temperate Northern Hemisphere, a region with strong seasonal variations in climate. How seasonality affects carbon storage capacity in seagrass meadows is largely unknown, and therefore, in this study, we aimed to assess variations in sedimentary total organic carbon (TOC) content over a 1-year cycle in seagrass meadows on the Swedish west coast. The TOC was measured in two Z. marina sites, one wave exposed and one sheltered, and at two depths (1.5 and 4 m) within each site, every second month from August 2015 to June 2016. We found a strong seasonal variation in carbon density, with a peak in early summer (June), and that the TOC was negatively correlated to the net community production of the meadows, presumably related to organic matter degradation. There was seasonal variation in TOC content at all sediment sections, indicating that the carbon content down to 30 cm is unstable on a seasonal scale and therefore likely not a long-term carbon sink. The yearly mean carbon stocks were substantially higher in the sheltered meadow (3,965 and 3,465 g m−2) compared to the exposed one (2,712 and 1,054 g m−2) with similar seasonal variation. Due to the large intra-annual variability in TOC content, seasonal variation should be considered in carbon stock assessments and management for cold-temperate seagrass meadows.
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| 7. |
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| 8. |
- Dahl, Martin, et al.
(författare)
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Increased current flow enhances the risk of organic carbon loss from Zostera marina sediments: Insights from a flume experiment
- 2018
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Ingår i: Limnology and Oceanography. - : Wiley. - 1939-5590 .- 0024-3590. ; 63:6, s. 2793-2805
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Tidskriftsartikel (refereegranskat)abstract
- Hydrodynamic processes are important for carbon storage dynamics in seagrass meadows, where periods of increased hydrodynamic activity could result in erosion and the loss of buried carbon. To estimate hydrodynamic impacts on the resuspension of organic carbon (Corg) in seagrass-vegetated sediments, we exposed patches (0.35 × 0.35 cm) of Zostera marina (with different biomass, shoot densities, and sediment properties) to gradually increased unidirectional (current) flow velocities ranging from low (5 cm s−1) to high (26 cm s−1) in a hydraulic flume with a standardized water column height of 0.12 m. We found that higher flow velocities substantially increased (by more than threefold) the proportion of Corg in the suspended sediment resulting in a loss of up to 5.5% ± 1.7% (mean ± SE) Corg from the surface sediment. This was presumably due to increased surface erosion of larger, carbon-rich detritus particles. Resuspension of Corg in the seagrass plots correlated with sediment properties (i.e., bulk density, porosity, and sedimentary Corg) and seagrass plant structure (i.e., belowground biomass). However, shoot density had no influence on Corg resuspension (comparing unvegetated sediments with sparse, moderate, and dense seagrass bed types), which could be due to the relatively low shoot density in the experimental setup (with a maximum of 253 shoots m−2) reflecting natural conditions of the Swedish west coast. The projected increase in the frequency and intensity of hydrodynamic forces due to climate change could thus negatively affect the function of seagrass meadows as natural carbon sinks. © 2018 The Authors. Limnology and Oceanography published by Wiley Periodicals, Inc. on behalf of Association for the Sciences of Limnology and Oceanography
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| 9. |
- Dahl, Martin, et al.
(författare)
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The influence of hydrodynamic exposure on carbon storage and nutrient retention in eelgrass (Zostera marina L.) meadows on the Swedish Skagerrak coast
- 2020
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Cold-temperate seagrass (Zostera marina) meadows provide several important ecosystem services, including trapping and storage of sedimentary organic carbon and nutrients. However, seagrass meadows are rapidly decreasing worldwide and there is a pressing need for protective management of the meadows and the organic matter sinks they create. Their carbon and nutrient storage potential must be properly evaluated, both at present situation and under future climate change impacts. In this study, we assessed the effect of wave exposure on sedimentary carbon and nitrogen accumulation using existing data from 53 Z. marina meadows at the Swedish west coast. We found that meadows with higher hydrodynamic exposure had larger absolute organic carbon and nitrogen stocks (at 0-25 cm depth). This can be explained by a hydrodynamically induced sediment compaction in more exposed sites, resulting in increased sediment density and higher accumulation (per unit volume) of sedimentary organic carbon and nitrogen. With higher sediment density, the erosion threshold is assumed to increase, and as climate change-induced storms are predicted to be more common, we suggest that wave exposed meadows can be more resilient toward storms and might therefore be even more important as carbon- and nutrient sinks in the future.
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| 10. |
- de los Santos, C. B., et al.
(författare)
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Microplastic retention by marine vegetated canopies: Simulations with seagrass meadows in a hydraulic flume
- 2021
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Ingår i: Environmental Pollution. - : Elsevier BV. - 0269-7491 .- 1873-6424. ; 269:January
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Tidskriftsartikel (refereegranskat)abstract
- Main finding: marine canopies with high shoot density might act as sinks for microplastics of high polymer density in areas of low flow velocity. © 2020 The Author(s) Marine canopies formed by seagrass and other coastal vegetated ecosystems could act as sinks of microplastics for being efficient particle traps. Here we investigated for the first time the occurrence of microplastic retention by marine canopies in a hydraulic flume under unidirectional flow velocities from 2 to 30 cm s−1. We used as model canopy-forming species the seagrass Zostera marina with four canopy shoot density (0, 50, 100, 200 shoots m−2), and we used as microplastic particles industrial pristine pellets with specific densities from 0.90 to 1.34 g cm−3 (polypropylene PP; polystyrene PS; polyamide 6 PA; and polyethylene terephthalate PET). Overall, microplastics particles transported with the flow were retained in the seagrass canopies but not in bare sand. While seagrass canopies retained floating microplastics (PP) only at low velocities (<12 cm s−1) due to a barrier created by the canopy touching the water surface, the retention of sinking particles (PS, PA, PET) occurred across a wider range of flow velocities. Our simulations revealed that less dense sinking particles (PS) might escape from the canopy at high velocities, while denser sinking particles can be trapped in scouring areas created by erosive processes around the eelgrass shoots. Our results show that marine canopies might act as potential barriers or sinks for microplastics at certain bio-physical conditions, with the probability of retention generally increasing with the seagrass shoot density and polymer specific density and decreasing with the flow velocity. We conclude that seagrass meadows, and other aquatic canopy-forming ecosystems, should be prioritized habitats in assessment of microplastic exposure and impact on coastal areas since they may accumulate high concentration of microplastic particles that could affect associated fauna. © 2020 The Author(s)
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